Three-dimensional photovoltaic devices including cavity-containing cores and methods of manufacture

Various stamping methods may reduce defects and increase throughput for manufacturing metamaterial devices. Metamaterial devices with an array of photovoltaic bristles, and/or vias, may enable each photovoltaic bristle to have a high probability of photon absorption. The high probability of photon absorption may lead to increased efficiency and more power generation from an array of photovoltaic bristles. Reduced defects in the metamaterial device may decrease manufacturing cost, increase reliability of the metamaterial device, and increase the probability of photon absorption for a metamaterial device. The increase in manufacturing throughput and reduced defects may reduce manufacturing costs to enable the embodiment metamaterial devices to reach grid parity.

FIELD

This application generally relates to photovoltaic devices, and more specifically to the methods of manufacturing photovoltaic cells featuring a large number of photovoltaic bristles.

BACKGROUND

Solar power is a popular clean energy, but it is generally more expensive than its fossil fuel competitors (e.g., oil, coal, and natural gas) and other traditional energy sources (e.g., hydropower). Typically, solar energy is relatively expensive because traditional photovoltaic cells with a planar configuration have generally low total efficiency. Total efficiency is based upon the total power produced from a solar panel throughout the day as the sun transits across the sky. Total efficiency is different from the theoretical efficiency, which is the fraction of light energy converted to electricity by the photovoltaic cells with a zero angle of incidence (e.g., the instant when the sun is directly above the metamaterial). Thus, a high total efficiency photovoltaic cell is needed to make solar energy cost-competitive with fossil fuels and traditional energy sources.

SUMMARY

The various embodiment methods of manufacturing and assembling may be used to produce photovoltaic cells formed from a plurality of photovoltaic bristles whose photovoltaic and conductive materials are configured to exhibit a high probability of photon absorption and internal reflection. As a result of the high probability of photon absorption and internal photon reflections, the photovoltaic cells of photovoltaic bristles exhibit high total efficiency in converting light energy into electrical energy. The high total efficiency of the embodiment photovoltaic cells may lead to increased efficiency and more power generation from the photovoltaic cell.

In various embodiments, printing techniques may be used to ensure high throughput and low defects in manufacturing the metamaterial device. The high throughput and low defects may reduce the manufacturing cost to enable the embodiment metamaterial devices to reach grid parity. In various embodiments, arrays of cores or vias may be manufactured from an original master template. An embodiment roll-to-web system and method may create daughter templates or master webs from the original master template to protect the original master template from repeat processing, thereby reducing defects. An embodiment web-to-plate system and method may create an array of cores or vias on a substrate from the master web. The master web, or plate, may be subjected to further processing (depositing photovoltaic layers, conductive layers, etc.) to create the embodiment metamaterial device.

In various embodiments, a system for manufacturing a photovoltaic structure is provided, which may include a web-to-plate system configured to imprint a die including a pattern of protruding structures onto a moldable material layer to generate a pattern of trenches extending downward from a top surface of the moldable material layer. The die may be incorporated into a web. The system may further include a deposition system configured to sequentially deposit a transparent conductive material layer, a photovoltaic material layer, and a core conductive material layer within the pattern of trenches in the moldable material layer.

Various embodiments include a method of manufacturing a metamaterial. In some embodiments a moldable material layer may be provided on, or in, a substrate. A die including a pattern of protruding structures and incorporated into a web may be imprinted onto the moldable material layer to generate a pattern of trenches extending downward from a top surface of the moldable material layer. A transparent conductive material layer, a photovoltaic material layer, and a core conductive material layer may be sequentially deposited within the pattern of trenches in the moldable material layer.

Various embodiments may include a photovoltaic structure. The photovoltaic structure includes a dielectric material layer comprising a planar portion having a uniform thickness and an array of protruding portions extending from a planar surface of the planar portion. The photovoltaic structure further comprises a layer stack located on the dielectric material layer and comprising a core conductive material layer, a photovoltaic material layer, and a transparent conductive material layer. The core conductive material layer is in contact with the planar surface and the protruding portions of the dielectric material layer. The transparent conductive material layer is spaced from the core conductive material layer by the photovoltaic material layer. Each combination of a protruding portion of the dielectric material layer and portions of the layer stack surrounding the protruding portion constitutes a photovoltaic bristle.

Various embodiments may include a method of forming a photovoltaic structure. A top surface of a moldable material layer is patterned with an array pattern. The array pattern includes an array of vertically extending shapes that protrude upward or downward from that top surface of the moldable material layer. A layer stack is deposited over the array pattern. The layer stack comprises a transparent conductive material layer, a photovoltaic material layer, and a core conductive material layer. A dielectric material layer is deposited over the layer stack. A two-dimensional array of photovoltaic bristles is formed. Each photovoltaic bristle comprises a vertically protruding portion of the layer stack and embedding a dielectric core comprising a dielectric material. The dielectric core contacts a sidewall of the core conductive material layer. The transparent conductive material layer is spaced from the core conductive material layer by the photovoltaic material layer.

Various embodiments may include a method for manufacturing a metamaterial including an array of photovoltaic bristles having approximately cylindrical shapes. An array of vias extending into a substrate is formed. Each via within the array has an approximately cylindrical shape and is laterally separated from one another, and is laterally surrounded, by the substrate. A transparent conductive layer is deposited over the array of vias. An absorber layer is deposited over the outer conductive layer. A core conductive material layer is deposited over the absorber layer. Each via is partially filled with the core conductive material layer to form a conductive core of a respective photovoltaic bristle. Cavities are filled within the vias by depositing a dielectric material layer over the core conductive material layer. A base layer is formed over the deposited conductive material. A dielectric core that comprises the dielectric material is formed within each photovoltaic bristle and between the core conductive material layer and the base layer.

Various embodiments may include a photovoltaic structure that may include a layer stack located over a substrate and may include a core conductive material layer, a photovoltaic material layer, and a transparent conductive material layer. The photovoltaic structure may further include a plurality of via cavities located underneath vertically protruding portions of the layer stack and above the substrate and free of any solid phase material therein.

Various embodiments may include a method of forming a photovoltaic structure that includes forming a pattern of trenches extending downward from a top surface of an optically transparent layer. A transparent conductive material layer, a photovoltaic material layer, and a core conductive material layer may be sequentially deposited within the pattern of trenches in the moldable material layer. A via cavity laterally bound by a surface of the core conductive material layer may be formed within, or above, each trench.

Various embodiments may include a method for manufacturing a metamaterial including an array of photovoltaic bristles having approximately cylindrical shapes. An array of vias extending into a substrate may be formed. Each via within the array has an approximately cylindrical shape and is laterally separated from one another, and is laterally surrounded, by the substrate. A transparent conductive layer is deposited over the array of vias. An absorber layer is deposited over the outer conductive layer. A core conductive material layer is deposited over the absorber layer. Each via is partially filled with the core conductive material layer to form a conductive core of a respective photovoltaic bristle. A base layer is formed over the deposited conductive material. A non-solid core that does not include the conductive material or a material of the base layer is formed within each photovoltaic bristle and between the core conductive material layer and the base layer.

DETAILED DESCRIPTION

The various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the invention or the claims. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” or “the” is not to be construed as limiting the element to the singular. The terms “example,” “exemplary,” or any term of the like are used herein to mean serving as an example, instance, or illustration. References to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the invention or the claims. Any implementation described herein as an “example” is not necessarily to be construed as preferred or advantageous over another implementation. The drawings are not drawn to scale. Multiple instances of an element may be duplicated where a single instance of the element is illustrated, unless absence of duplication of elements is expressly described or clearly indicated otherwise.

The various geometrical features of the embodiment photovoltaic structures are described herein with reference to spatial orientations (e.g., top, bottom, horizontal, vertical, etc.) of the photovoltaic structures (such as an upright orientation or an inverted orientation) as illustrated in the figures. Such references to special orientations of the various features described or recited in claims is for ease of description with reference to the figures, and are not intended to impose limits or requirements on the finished product produced by the various embodiment methods. Thus, references to horizontal and vertical are merely with reference to the orientation of structures illustrated in the figures, and not intended to impose limits or restrictions on the manner or orientation in which the structures may be deployed. For example, an embodiment of the structures formed by the embodiment fabrication methods orients the finished product so that the conical shapes described as having a vertical dimension are deployed at an angle to the vertical with respect to the ground.

As used herein, the term “photovoltaic bristle” refers to a three-dimensional structure approximately cylindrical with a height approximately equal to 1-100 microns, a diameter of approximately 0.2-50 microns that includes at least one photovoltaically-active semiconductor layer sandwiched between a conductive inner layer or core and a transparent outer conductive layer (e.g., TCO and a nonconductive outer layer). The term “bristle” is used merely because the structures have a length greater than their diameter, the structures have a generally (on average) circular cross-section, and the overall dimensions of the structures are on the dimensions of sub-microns to tens of microns. In the embodiment illustrated herein the photovoltaic bristles have an approximately cylindrical shape, by which it is meant that a substantial portion of the exterior surface of the structures have a cross-section that is approximately circular or elliptical with both radii being approximately coexistent. Due to manufacturing variability, no single photovoltaic bristle may be exactly cylindrical in profile, but when considered over a large number of photovoltaic bristles the average profile is approximately cylindrical. In another embodiment, the photovoltaic bristles may have a non-circular cross-section, such as hexagonal, octagonal, elliptical, etc. as may facilitate manufacturing.

When the embodiment photovoltaic bristles are arranged on a substrate in an order or disordered array, the resulting structure may form a metamaterial structure. As used herein, the term “metamaterial” or “metamaterial substrate” refers to an array of photovoltaic bristles on a substrate. Metamaterials as used herein are artificial materials that are engineered with metals or polymers that are arranged in a particular structured or non-structured pattern that result in material properties (including light absorption and refraction properties) that are different from the component materials. The cumulative effect of light interacting with the array of photovoltaic bristles may be affected by controlling the shape, geometry, size, orientation, material properties, material thicknesses, and arrangement of the bristles making up the metamaterial as described herein.

As used herein, a “layer” refers to a material portion including a region having a substantially uniform thickness. A layer may extend over the entirety of an underlying or overlying structure, or may have an extent less than the extent of an underlying or overlying structure. Further, a layer may be a region of a homogeneous or inhomogeneous contiguous structure that has a thickness less than the thickness of the contiguous structure. For example, a layer may be located between any pair of horizontal planes between, or at, a top surface and a bottom surface of the contiguous structure.

Traditional planar photovoltaic cells are flat. In traditional planar photovoltaic cells, a limited number of photons are absorbed at any given point in time. Photon absorption occurs through the thickness of the traditional planar photovoltaic cell (e.g., top-to-bottom) from the point of photon entry until the photon is converted to electrical energy. Traditional planar photovoltaic cells convert photons into electrical energy when photons interact with a photovoltaic layer. However, some photons pass through the photovoltaic layer without generating electron-hole pairs, and thus represent lost energy. While the number of photons absorbed may be increased by making the photovoltaic layer thicker, increasing the thickness increases the fraction of electron-hole pairs that recombine, converting their electrical potential into heat. Additionally, thicker photovoltaic films exhibit an exponential attenuation loss, which leads to a decrease in photon conversion. For this reason, traditional planar photovoltaic cells have emphasized thin photovoltaic layers, accepting the reduced photon-absorption rate in favor of increased conversion of electron-hole pairs into electrical current and reduced heating. The theoretical peak efficiency, as well as the total efficiency of traditional planar photovoltaic cells is thus limited by the planar geometry and the unattenuated fraction of photons that may be absorbed in a maximized optical path length through the photovoltaic layer.

Conventional planar photovoltaic cells also suffer from low total efficiency in static deployments (i.e., without sun tracking equipment) since their instantaneous power conversion efficiency decreases significantly when the sun is not directly overhead (i.e., before and after noon). Peak efficiencies of traditional planar photovoltaic cells are affected by their orientation with respect to the sun, which may change depending on the time of day and the season. The standard test conditions for calculating peak efficiencies of solar cells are based on optimum conditions, such as testing the photovoltaic cells at solar noon or with a light source directly above the cells. If light strikes traditional photovoltaic cells at an acute angle to the surface (i.e., other than perpendicular to the surface) the instantaneous power conversion efficiency is much less than the peak efficiency. Traditional planar photovoltaic cells in the northern hemisphere are typically tilted toward the south by an angle based on the latitude in order to improve their efficiency. While such fixed angles may account for the angle of the sun at noon due to latitude, the photovoltaic cells receive sunlight at an angle during the morning and afternoon (i.e., most of the day). Thus, traditional planar photovoltaic cells actually result in a low total efficiency and low total power generation when measured beyond a single moment in time.

The various embodiments include photovoltaic cells that exhibit metamaterial characteristics from regular or irregular arrays of photovoltaic bristles configured so the conversion of light into electricity occurs within layers of the photovoltaic bristles. Since the photovoltaic bristles extend above the surface of the substrate and are spaced apart, the arrays provide the photovoltaic cells of the various embodiments with volumetric photon absorption properties that lead to energy conversion performance that exceeds the levels achievable with traditional planar photovoltaic cells. The volumetric photon absorption properties enable the various embodiment photovoltaic cells to generate more power than traditional planar photovoltaic cells with the same footprint. Due to the small size of the photovoltaic bristles, the photovoltaically-active layers within each bristle are relatively thin, minimizing power losses due to electron-hole recombination. The thin photovoltaically-active layers help reduce attenuation losses normally present in thicker photovoltaic films because the photovoltaic bristles include a thin radial absorption depth and a relatively thicker vertical absorption depth maximizing photon absorption and power generation through the combined long circumferential absorption path length and short radial electron path length. When individual photovoltaic bristles are combined in an array on or within a substrate, a metamaterial structure may be formed that exhibits a high probability of photon absorption and internal reflection that leads to increased energy conversion efficiencies and power generation. Various embodiment structures also provide additional performance-enhancing benefits as will be described in more detail below.

Further performance enhancements may be obtained by positioning the embodiment photovoltaic cells so that the photovoltaic bristles' sidewalls are at an angle to the incident photons. This may improve the probability that photons will be absorbed into the photovoltaic bristles due to wave interactions between photons and the outer conductive layer on each photovoltaic bristle. Orienting the embodiment photovoltaic bristles at an angle to the incident photons also increases the circumferential optical depth of the photovoltaic bristles exposed to the light, because in such an orientation the photons strike the sides of the bristles and not just the tops of the bristles. The off-axis photon absorbing characteristics of the photovoltaic bristles also enables the embodiment photovoltaic cells to exhibit significant total energy conversion efficiency for indirect and scattered light, thereby increasing the number of photons available for absorption compared to a conventional photovoltaic cell.

An embodiment described herein includes photovoltaic cells featuring arrays of photovoltaic bristles on roughly corrugated surfaces in order to present the bristles at an angle to incident sunlight. Further embodiments described herein include methods for manufacturing photovoltaic cells featuring arrays of photovoltaic bristles, as well as assembly of such photovoltaic cells into solar panels.

For purposes of background on the physics and geometries that enable photovoltaic bristles to achieve significant improvements in peak power performance, an overview of embodiment photovoltaic bristles and corresponding photovoltaic cells is now presented. More details on the dimensions, materials and configurations of embodiment photovoltaic bristles are disclosed in U.S. patent application Ser. No. 13/751,914 that is incorporated by reference above.

FIG. 1Aillustrates a cross-sectional top view of one photovoltaic bristle101andFIG. 1Billustrates a cross-sectional side view of the photovoltaic bristle101ofFIG. 1A.FIGS. 1A and 1Billustrate the path traveled by a photon entering the side of the outer periphery of the photovoltaic bristle101. A photovoltaic bristle101may guide an absorbed photon112so that it follows an internal path113that exhibits a high probability that the photon remains within the photovoltaic bristle101due to total internal reflection. A photovoltaic bristle may exhibit total internal reflection by controlling the thickness of the layers103and111and by radially ordering the materials by indexes of refractions from a low index of refraction on the outside to a higher index of reaction in each inner layer, the photovoltaic bristle101may refract or guide photons112toward the core of the photovoltaic bristle101. Since the core106may be highly conductive, it is also highly reflective, so that it will reflect photons112. As illustrated, due to the large difference in index of refraction between the absorber layer and the outer conductive layer103, photons striking this boundary at an angle will be refracted inward. As a result of these reflections and refractions, photons112may be effectively trapped within the absorption layer111for a longer period of time, thereby increasing the probability of interaction with the absorption layer11causing an electron-hole pair to be formed. Increasing the probability of photon absorption may result in more electrical current being generated for the same amount of incident light energy by the embodiment photovoltaic cells than is achievable by conventional photovoltaic cells.

It should be noted that the embodiment shown inFIGS. 2A-2Bmay include an inner reflector due to a metal core106. In other embodiments, a refraction layer may be applied over the core106to achieve the same photon reflection effects. In such an embodiment, a reflective layer may be formed over the conductive core and under the absorber layer, such as a semiconductor or dielectric material layer having a lower index of refraction than the absorber layer. This refraction layer may be configured to reflect the photon at the interface between the reflection layer and the absorber layer, and not rely on reflection off of the conductive core106. For example, such a diffraction layer may be formed from an aluminum doped zinc oxide layer of about 500-1500 angstroms in thickness. Reflected photons then refract through each layer104,105until they reach the outer conductive layer103, where the difference in the index of refraction between the absorption sublayer105and the outer conductive layer103causes the photons to reflect back into the absorption layers of the photovoltaic bristle. The reflected photons that are not reflected inwardly at the boundary between the outer conductive layer103and the absorption sublayer105may pass through the outer conductive layer103and be reflected off of the interface between the outer conductive layer103and air due to the difference in the index of refraction at this interface. In either manner, photons may remain within the photovoltaic bristle passing back and forth through the absorption layer111until they are eventually absorbed or exit the bristle.

Each photovoltaic bristle101is made up of a core106that may be conductive or has a conductive outer surface, an absorption layer111and an outer conductive layer103, which will typically be a transparent conductive layer such as a transparent conductive oxide or transparent conductive nitride. Due to the cylindrical form of photovoltaic bristles, the absorption layer111surrounds the core106, and the outer conductive layer103surrounds the absorption layer111. Although, two absorber sublayers104,105are shown, it should be noted that the absorption layer111may include any number of absorber sublayers or regions of photovoltaically-active materials or combinations of photovoltaic materials. For example, the absorption layer111may include multiple absorber sublayers or regions that form a p-n junction, a p-i-n junction, or multi junction regions, which have a generally circular cross-section as illustrated inFIG. 1A. If the absorption layer111forms a p-i-n junction with three absorber sublayers, one sublayer may be the intrinsic portion forming the p-i-n junction. If the core106is a semiconductor core forming a p-n junction with a single absorber sublayer, the absorption layer111may include only one sublayer. Regardless of the number, the absorber sublayers or regions104,105may be made from one or more of silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, gallium arsenide, aluminum gallium arsenide, cadmium sulfide, copper indium selenide, and copper indium gallium selenide.

The relative radial positions of the p-type, intrinsic, or n-type sublayers/regions may vary in different embodiments. For example, in an embodiment the p-type semiconductor material may be positioned radially inside the n-type semiconductor material. In another embodiment, the n-type semiconductor material may be positioned radially inside the p-type semiconductor material. In addition, multiple materials may be used to create a sequence of p-n and/or n-p junctions, or p-i-n junctions in the absorption layer. For example, the absorption layer may include an absorber sublayer of p-type cadmium telluride (CdTe) and an absorber sublayer of n-type cadmium sulfide (CdS). In an embodiment, the absorption layer111may be fully depleted. For example, the p-type region and the n-type region forming the sublayer or region104and the sublayer or region105may be fully depleted.

In an example embodiment, the absorption layer111may include a p-type semiconductor sublayer105, such as p-type cadmium telluride, and an n-type semiconductor sublayer of a different material, such as n-type-cadmium sulfide. In another example embodiment, one sublayer104may be a p-type region, such as p-type amorphous silicon, and another sublayer105may be an n-type region of the same material as the sublayer104but doped to form an n-type semiconductor, such as n-type amorphous silicon.

The outer conductive layer103has a radial thickness which may be measured radially from the outer surface of the absorption layer111to the outer surface of the outer conductive layer103(i.e., the outer surface of the photovoltaic bristle). In an embodiment, the outer conductive layer103is a transparent conductive oxide (“TCO”), such as a metal oxide. In an embodiment, the outer conductive layer103may include a dopant creating a p-type or n-type transparent conductive oxide. For example, the transparent conductive oxide layer103may be one of intrinsic zinc oxide, indium tin oxide, and cadmium tin oxide (Cd2SnO4). In an embodiment, the outer conductive layer103may include a transparent conductive nitride such as titanium nitride (TiN). In another embodiment, the outer conductive layer103may include a buffer with or without the dopant. Some examples of an outer conductive layer103, which may be a transparent conductive oxide with a dopant, include boron-doped zinc oxide, fluorine doped zinc oxide, gallium doped zinc oxide, and aluminum doped zinc oxide. Some examples of buffers that may be added to a transparent conductive oxide include zinc stannate (Zn2SnO4), titanium dioxide (TiO2), and similar materials well known in the art.

Although not shown inFIGS. 1A-1B, the outer conductive layer103may include any number of conductive and/or non-conductive sublayers to achieve a particular total optical thickness while simultaneously having a thin conductive sublayer. With multiple sublayers, the outer conductive layer103may also benefit from adding flexibility to the photovoltaic bristles for a more resilient photovoltaic bristle metamaterial device. The addition of a non-conductive sublayer may have refractive properties that improve off-angle photon absorption efficiency. Analysis and observations of prototypes indicate that outer conductive layers between 500 and 15,000 angstroms result in a decrease in electrical resistance in the conductive layers from field effects at the structural discontinuities in the photovoltaic bristles. However, the outer conductive layer103of a bristle may need to be of a minimum optical thickness exceeding 500 angstroms to achieve the photon trapping and guiding effect shown inFIG. 1A. Thus, the outer conductive layer103may include multiple layers to achieve the conflicting optical thickness requirement and the requirement for electrical resistivity benefits from field effects. As an example, the outer conductive layer103may have two sublayers including a conductive sublayer such TCO and a non-conductive sublayer such as an optically transparent polymer. As another example, the non-conductive sublayer may be a bi-layer including TCO and a polymer or glass. As a further example, the outer conductive layer103may include three sublayers where a non-conductive sublayer separates two conductive sublayers.

In an embodiment, the core106may be of a variety of conductive materials and non-conductive materials. In an embodiment, the core106may be a solid conductive core such as a metal. For example, the solid conductive core may be gold, copper, nickel, molybdenum, iron, aluminum, or silver. In an embodiment, the core106may include the same material as the substrate202(shown inFIG. 2B). For example, the core106and the substrate202may include a polymer. In another embodiment, the core106may include a different material than the substrate202. In another embodiment, an inner conductive layer107may surround the core106. For example, the inner conductive layer107may be gold, copper, nickel, molybdenum, iron, aluminum, or silver to create a conductive core. In an embodiment, the core106may include a polymer with an inner conductive layer107surrounding the polymer. The inner conductive layer107may include similar material as the outer conductive layer103. For example, the inner conductive layer107may include a transparent conductive oxide, a transparent conductive nitride, and/or a non-conductive transparent material. The inner conductive layer107may include multiple layers (e.g., sublayers of TCO and a non-conductive optically transparent polymer) to achieve the conflicting benefits of field effects and proper optical depth for the photovoltaic device. In an embodiment, the core106may include a semiconductor material. For example, the core106may be made from one or more of silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, gallium arsenide, aluminum gallium arsenide, cadmium sulfide, copper indium selenide, and copper indium gallium selenide.

FIG. 1Balso illustrates that photons striking the photovoltaic bristle101will have a higher probability of absorption when they strike the sidewall of a photovoltaic bristle at a compound angle that is less than 90 degrees but more the 0 degrees to the surface, where an angle perpendicular to the sidewall surface is considered to be 0 degrees. The compound incident angle includes a vertical plane component133(shown inFIG. 1B) and a horizontal plane component132(shown inFIG. 1A). The horizontal plane component132is defined by a photon112striking the outer surface of the bristle at a point along the perimeter of the circular cross-section plane forming an angle with the perimeter where an angle perpendicular to the perimeter is considered 0 degrees. Similarly, the vertical plane component133is defined by the photon112striking the outer surface of the bristle at a point along the height forming a vertical angle with the surface where an angle perpendicular to the surface is considered 0 degrees.

Analysis of photon absorption characteristics of the outer conductive layer have revealed that photons striking the surface of the sidewall of the photovoltaic bristle perpendicular to the horizontal component132and the vertical component133may result in a compound angle of 0 degrees and an increased probability of being reflected off the surface. Similarly, photons striking the surface of the sidewall of the photovoltaic bristle parallel to the vertical and the horizontal component will also have an increased probability of being reflected off the surface. However, photons striking the side surface at a compound angle between 10° and 80° have a high probability of being absorbed into the outer conductive layer203. Once absorbed, the internal refraction characteristics of the absorber sublayers104,105and outer conductive layer103cause the photons to remain within the photovoltaic bristle101for an extended time or path length. This characteristic is very different from conventional photovoltaic cells, which exhibit the maximum power conversion efficiency when the angle of incidence of photons is normal to its single planar surface.

The difference between the incident angle corresponding to conventional photovoltaic cells and the photovoltaic bristles is illustrated by angle θp inFIG. 1B. The preferred incident angle for a traditional solar cell, θp, would form a right angle with the top of the bristle as well as the substrate of the full metamaterial device (not shown). Thus, not only does the photovoltaic bristle exhibit better absorption characteristics at off-angles (not perpendicular or parallel to the surface), the reference point for measuring an off-angle is different from that of a conventional photovoltaic cells. For a metamaterial device with photovoltaic bristles, the reference point is measured from the sidewall of a bristle in two planes, which is unachievable by a planar photovoltaic cell. Thus, due to the off-angle absorption characteristics of photovoltaic bristles, the embodiment photovoltaic cells exhibit significant power conversion efficiency across a broad range of angle of incidence. This translates to more power generation throughout the day than achievable from fixed solar panels with conventional planar solar arrays that produce their peak efficiencies (i.e., maximum power generation) when the sun is directly overhead.

FIG. 2Aillustrates a perspective view of metamaterial200including an array of photovoltaic bristles201a,201b,201c,201d,201e,201f,201g,201h,201i,201j,201k,201l,201m,201n,201o,201pextending from a flat substrate202(shown inFIG. 2B). While illustrated with twelve photovoltaic bristles201a-201p, a metamaterial may include a larger number of photovoltaic bristles. The number of photovoltaic bristles201will depend upon the dimensions and spacing of the bristles and the size of the photovoltaic cell. As with conventional photovoltaic cells, metamaterials may be assembled together in large numbers to form panels (i.e., solar panels) of a size that are suitable for a variety of installations.

Each photovoltaic bristle201a-201pis characterized by its height “h,” which is the distance that each bristle extends from the substrate202. Photovoltaic bristles201a-201pare also characterized by their radius “r”. In an embodiment, all photovoltaic bristles201a-201pwithin an array will have approximately the same height h and approximately the same radius r in order to facilitate manufacturing. However, in other embodiments, photovoltaic bristles201a-201pwithin the array may be manufactured with different heights and diameters.

In an embodiment, the number of photovoltaic bristles in a photovoltaic cell may depend upon the substrate surface area available within the cell and the packing density or inter-bristle spacing. In an embodiment, photovoltaic bristles may be positioned on the substrate with a packing density or inter-bristle spacing that is determined based upon the bristle dimensions (i.e., h and r dimensions) as well as other parameters, and/or pattern variations. For example, a hexagonal pattern may be used rather than the trigonometric pattern shown inFIG. 2A.

In the various embodiments, the dimensions and the inter-bristle spacing of photovoltaic bristles may be balanced against the shading of neighboring bristles. In other words, increasing the number of photovoltaic bristles on a plane may increase the surface area available for absorbing photons. However, each photovoltaic bristle casts a small shadow, so increasing the photovoltaic bristle density of a photovoltaic cell beyond a certain point may result in a significant portion of each bristle being shadowed by its neighbors. While such shadowing may not reduce the number of photons that are absorbed within the array, shadowing may decrease the number of photons that are absorbed by each photovoltaic bristle, and thus there may be a plateau in the photon absorption versus packing density of photovoltaic bristles.

A further consideration beyond shadowing is the wave interaction effects of the array of closely packed photovoltaic bristles. The interior-bristle spacing may be adjusted to increase the probability that photons entering the array are absorbed by the photovoltaic bristles' metamaterial properties considering the bulk material properties of the layered films that makeup the array. For example, specific characteristics such as extinction coefficient or absorption path length may predict an optimal dimensional design, although one may choose to deviate from this prediction resulting in a sacrifice in performance.

FIG. 2Bis a cross-sectional side view of a section of metamaterial200including photovoltaic bristles201m,201n,201o, and201pas illustrated inFIG. 2A. As shown inFIG. 2Bthe photovoltaic bristles extend from a substrate202. In an embodiment, the core106may be the same material as the substrate202and an inner conductive layer107may surround the core106. The absorber layer111may surround the inner conductive layer107and the outer conductive layer103may surround the absorber layer111. The absorber layer111may include any number of sublayer or regions. As illustrated inFIG. 2B, the absorber layer111may include two sublayers or regions104,105. In an embodiment, the two absorber sublayers or regions104,105may be any semiconductor material where one sublayer or region is doped as n-type and the other is doped as p-type.

The metamaterial200may include a substrate202of any suitable substrate material known to one skilled in the art. For example, the substrate202may be glass, doped semiconductor, diamond, metal, a polymer, ceramics, or a variety of composite materials. The substrate202material may be used elsewhere in the metamaterial200, such as a material used in any layer of a photovoltaic bristle201m-201n. Alternatively, the material used in the substrate202may be different from other materials used in the photovoltaic bristles201m-201n. In an embodiment, the core106and the substrate202may include a common material. For example, the substrate202and the core106may include glass, semiconductor material, a polymer, ceramics, or composites. In a further embodiment, the core106and substrate202may include similar materials, while the inner conductive layer107is added over the substrate202and surrounding the core106creating a conductive core. The inner conductive layer107may include metal such as gold, copper, nickel, molybdenum, iron, aluminum, or silver. Alternatively, the inner conductive layer may include any of the materials used for the outer conductive layer103which may be used in combination with the previously listed metals.

In an embodiment, the inner conductive layer107may also be an inner refraction or reflection layer that is added on top of the core106in order to provide an inner reflection interface for photons. In this embodiment, a layer of semi-conductive or insulator material, such as B:ZnO, Al:ZnO, ZnO, or ITO, may be applied over the metal core. This layer may be at least one-half wavelength in thickness, depending on the refractive index of the material. For example, such a layer made of Al:ZnO (AZO) may be approximately 500 angstroms to 1500 angstroms thick over which the absorber layer may be applied. Such an AZO layer has a refractive index that is lower than the absorber layer. This difference in refractive index coupled with the curvature of the interface of these two layers will reflect the photons before they reach the metal core. The reflection induced by this design may exhibit lower losses than the designs in which photons reflect from a metal surface of the core. The use of such a refraction layer may be included in any of the embodiments illustrated and described herein. For example, in the embodiments in which the center of the core is a plastic rod, a metal layer is applied over the plastic core and then the AZO is applied over the metal layer. In further embodiments, this refractive layer forming a reflecting interface may be formed using multiple layers, such as: ITO-AZO; ITO-AZO-ITO; TiO2-TiN—TiO2; ZnO-AZO-ZnO; etc. Such multiple layers may function similar to a Bragg reflector used in fiber optics.

In order to increase the percentage of solar photons striking photovoltaic bristles at the appropriate angle of incidence, one embodiment orients the photovoltaic bristles at an angle on a corrugated substrate. Positioning photovoltaic bristles at an angle to incident light increases the probability of off-axis photon absorption, which may reflect and propagate photons around and within the photovoltaic bristles, thereby developing an equilibrium standing wave and increasing probability of converting photon energy into electrical energy. Consequently, embodiment photovoltaic cells with such a corrugated shape may generate more electrical power than is possible from conventional photovoltaic cells.

In addition to increasing the probability of photon absorption, embodiment corrugated photovoltaic cells provide more surfaces and more photovoltaic bristles for photon absorption within a given planar footprint than a comparable flat substrate configuration. Each corrugated photovoltaic cell may include a large number of angled surfaces with photovoltaic bristles, compared to a conventional flat substrate photovoltaic cell that has only a single flat surface or absorbing photons. The improvements from the corrugated photovoltaic cell results in an increase in optical volume enabling more photon absorption and power generation from such a metamaterial device.

FIG. 3Ais a perspective view of an embodiment metamaterial300including a corrugated shaped substrate302(shown inFIG. 3B) with arrays of photovoltaic bristles301positioned on each slanted substrate surface308a,308b,308c,309a,309b, and309c. AlthoughFIG. 3Adepicts six slanted substrate surfaces, in an embodiment, the metamaterial300may have a larger number of slanted substrate surfaces. InFIG. 3A, each slanted substrate surface308a-308c, and309a-309cmay form an angle θb with the flat foundation303of the substrate302. In an embodiment angle θb may be between about 30 and about 60 degrees. In further embodiments the angle θb may be 30-35 degrees, 35-40 degrees, 40-45 degrees, 45-50 degrees, 50-55 degrees, and 55-60 degrees. In an embodiment, arrays of photovoltaic bristles301may be oriented so that their long axis is normal to the slanted substrate surfaces308a-308cand309a-309cincluding angle θb to increase the probability of photon absorption and photon trapping and guiding from photons striking the sidewalls of each photovoltaic bristles301at compound angles approximately between 10 and 80. It should be noted that each slanted substrate surface308a-308cand309a-309cmay include any number of photovoltaic bristles301(i.e. more than the twelve photovoltaic bristles301shown in the figure).

FIG. 3Bis a cross-sectional side view of a section of a metamaterial300including slanted substrate surfaces308aand309aat angles θb with the foundation303and an array of photovoltaic bristles301on each slanted substrate surface. As described above, each photovoltaic bristle301may include a core106, an inner conductive layer107, and an absorber layer111with absorber sublayers104,105surrounding the inner conductive layer, and an outer conductive layer103surrounding the absorber layer111. In an embodiment, the core106may be the same material as the substrate302. The photovoltaic bristles301extend from the corrugated surface302perpendicular to each slanted surface308,309. As illustrated in the figure, this angle enables photons112traveling along the photon path113to enter the sidewall of the photovoltaic bristle301at a compound angle of approximately 10°-80°.

In another embodiment, photovoltaic bristles are positioned only on alternating slanted surfaces of the corrugated substrate, with the opposite surfaces lacking such structures. This embodiment configuration may reduce manufacturing costs while presenting photovoltaic bristles on the surfaces most likely to receive solar radiation when deployed. Additionally, the slanted surfaces that do not include photovoltaic bristles may be coated with a reflective material (e.g., a metal) so that photons striking that surface are reflected at a desirable angle into the photovoltaic bristles on the opposite surface. Such an embodiment is illustrated inFIGS. 4A and 4B.

FIG. 4Ais a perspective view of metamaterial400including a corrugated shaped substrate402(shown inFIG. 4B) and arrays of photovoltaic bristles401positioned at normal from the planes of alternating slanted substrate surfaces408a,408b, and408c. In an embodiment, slanted substrate surfaces409a,409b, and409cmay be without arrays of photovoltaic bristles401and may be configured with a reflective surface coating, such as a metal, that may reflect photons into the photovoltaic bristles on the opposite surface as illustrated inFIG. 4B. AlthoughFIG. 4Adepicts six slanted substrate surfaces, in an embodiment, the metamaterial400may have a larger or smaller number of slanted substrate surfaces.

FIG. 4Bis a cross-sectional side view of a section of metamaterial400with a corrugated substrate402including slanted substrate surfaces408a,408b,409a,409bat angles θb with the foundation403. In an embodiment, each slanted substrate surface408a,408bmay include an array of photovoltaic bristles401configured approximately normal to the slanted substrate surface. In an embodiment, slanted substrate surfaces409aand409bmay include a reflective layer405. As such, the reflective layer405may reflect photons411along a photon path412so that the reflected photons411′ strikes the photovoltaic bristles extending from the adjacent slanted substrate surface408bof the substrate402. In an embodiment, a reflective layer405(i.e., reflective film) may be any material that has high reflective characteristics to reflect photons usable for the embodied metamaterial.

FIG. 5illustrates an advantage of the various embodiment photovoltaic cells when installed on a typical structure502(e.g., a house) having a roof with angled surfaces504,506. In this illustrative figure, photovoltaic cells200on a northern facing roof surface may have a flat profile and feature photovoltaic bristles201that extend perpendicular from the surface. Since this surface of the roof506receives sunlight at an angle, the incident sunlight on this surface is preferable for increasing photon absorption on such a photovoltaic cell200. On the southern facing roof surface504, corrugated photovoltaic cells300,400may be used since the sunlight will be striking the roof surface504at closer to a perpendicular angle of incidence. The301,304angular orientation of the photovoltaic bristles on such corrugated photovoltaic cells300,400ensures that incident sunlight strikes the photovoltaic bristles at angles of incidence that will increase photon absorption.

Various embodiment methods of making photovoltaic bristles are now presented.

An embodiment method800for manufacturing photovoltaic bristles using a press or stamping process is illustrated inFIGS. 6A-6H, 7A-7C,FIG. 8. This embodiment method800may enable fabricating photovoltaic bristles using low-cost substrate materials such as plastics and polymers that may be processed rapidly in large volumes. This embodiment method will be described with reference toFIGS. 6A-6HandFIG. 8together. Although the figures illustrate and the text describes a rod imprint design, a via design may be similarly created as shown and described with reference to method1600. Additionally, any of a variety of raised shapes other than cylindrical rods or cones may be produced on the substrate using the embodiment methods and embodiment imprinting systems, including ridges, a mesh of interlocking ridges, hemispheres, etc.

In method800in block804, a plastic or polymer block or starting material may be processed in order to prepare it for a pressing or forming operation. The methods used for preparing such a polymer for pressing will depend upon the type of plastic or polymer selected. As illustrated inFIGS. 6A and 6B, in block808a die or mold602including a number of bristle holes604for forming the bristle cores may be pressed into the plastic or polymer material202and then removed, thereby forming an array of cores106out of the plastic polymer202. In an embodiment, vertical stamp602moves in a downward vertical manner into a polymer substrate202forming cores106and moving vertically away from the substrate202and the formed cores106. Alternatively, a rolling press or rolling die may be applied to a moving sheet or tray of material similar to printing press techniques.

When using a rolling press or rolling die a separate roll-to-web and web-to-plate sub-process may create the associated rolling stamps and the array of cores on the substrate for use in method800. The sub-process is discussed in depth later in this application with reference toFIGS. 33A-33G, 34, 35A-35E, 36A-36E. Generally, a master template is created using photolithographic techniques or nanoimprint lithography. The master template imprints a pattern on a polymer sheet or a web. The sheet or web may be a base material with a thin polymer imprintable layer or coating. For example, the sheet could be glass and/or the web could be polyester. The web is then used in combination with rollers (e.g., a rolling stamp) to stamp cores on a substrate similar to substrate202with cores106illustrated inFIG. 6B.

In block810, the newly formed array of cores106may be cured or otherwise processed in order to improve the material properties, such as to harden the material. This may involve processing with heat, ultraviolet radiation, and/or chemical vapor exposure, as would be well-known in the polymer arts and depend upon the type of material used. In an embodiment, the material processing in block810may be accomplished as part of the stamping operation in block808, either as part of the stamping operation and as a host stamping process, or entirely as a post-stamping process. For example, a rolling stamp may include an ultraviolet light that is configured so that when the rolling stamp rotates over the unformed substrate202the ultraviolet light simultaneously cures or partially cures the newly formed cores106.

As illustrated inFIG. 6C, in block812, an inner conductive layer107may be formed over the cores106. This may be accomplished by chemical vapor deposition, plasma enhanced chemical vapor deposition, physical deposition, plasma deposition, sputtering techniques, or electro-deposition techniques. The inner conductive layer107may further be formed or thickened by electroplating processes. Multiple conductive layers may be applied as part of block812. In an embodiment, the inner conductive layer or layers may be one or more of copper, aluminum, gold, nickel, titanium, silver, tin, tantalum, and chromium, as well as alloys of such metals. This process forms an inner conducting core for the photovoltaic bristle.

To form the photovoltaic portion of the photovoltaic bristles, a number of semiconductor layers may be applied to the inner conducting core using well-known semiconductor processing methods. As illustrated inFIG. 6D, in block804, a first absorber layer of semiconductor material may be formed over the inner conductive layer. For example, the first absorber layer105may include silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, cadmium sulfide, gallium arsenide, copper indium selenide, and copper indium gallium selenide. The first absorber layer105over the inner conductive layer107by electroplating, chemical vapor deposition, atomic layer deposition, etc.

As illustrated inFIG. 6E, in block842a second semiconductor material layer may be formed over the first absorber layer, with the first and second absorber layers having material properties to create a p-n junction or n-p junction configured to release electrons upon absorbing a photon. Any deposition method used to add the first absorber layer105may also be used to add the second absorber layer104. In an embodiment, the deposition method for the second absorber layer104may be the same deposition method used for adding the first absorber layer105. In an embodiment, the second absorber layer104may include a semiconductor material. For example, the second absorber layer104may include silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, cadmium sulfide, gallium arsenide, copper indium selenide, and copper indium gallium selenide. In an embodiment, the second absorber layer104may be an absorber sublayer or region comprising the same material as the first absorber layer105with a different dopant. For example, the first absorber layer105may be p-doped amorphous silicon and the second absorber layer104may be n-doped amorphous silicon. In an embodiment, the second absorber layer104may be an absorber sublayer comprising a different material as the first absorber layer105. For example, the first absorber layer105may be p-doped cadmium telluride and the second absorber layer104may be n-doped cadmium sulfide. In optional block846, additional absorber layers of semiconductor materials may be applied to form multiple p-n and/or n-p junctions (e.g., n-p-n or p-n-p junctions).

With the photon absorber layers formed, an outer conductive layer may be formed in block848as illustrated inFIG. 6G. The outer conductive layer may be a transparent conducting oxide or transparent conducting nitride, as are well-known in the photovoltaic technologies. In an embodiment, the only two absorber layers104,105may be applied, and thus the outer conductive layer103is deposited (e.g., by chemical deposition or physical deposition) over the last absorber layer104as shown inFIG. 6F. In optional block852, additional outer conductive layers may be applied depending upon the configuration of the photovoltaic bristles. Although the outer conductive layer inFIG. 6Gincludes two layers, any number of layers may make up the outer conductive layer103.

Corrugated photovoltaic cells may also be configured using similar processes as illustrated inFIGS. 7A-7C. For example, as illustrated in these figures, the operations of forming an array of cores in the plastic or polymer in block808may be accomplished by alternately pressing the material302with dies that are oriented at the desired angle of the corrugated surfaces. For example, photovoltaic bristles106may be formed on corrugated surfaces in the first orientation by pressing the material with dies702oriented along one angle as illustrated inFIG. 7B, followed by pressing the opposite surfaces with opposite oriented dies702as illustrated inFIG. 7C.

To form the embodiment illustrated inFIG. 4Cin which photovoltaic bristles are formed on only alternating sides of the corrugated surface, only a single pressing step as illustrated inFIG. 7Bmay be accomplished. In some embodiments, in optional block854a reflective layer may be applied to the surfaces that do not feature photovoltaic bristles. This may be accomplished using photoelectric graphic methods, such as coding the photovoltaic bristles with a photoresist that is removed from the other surfaces before a reflective layers applied.

As illustrated inFIG. 6H, in optional block856the conductive traces may be added to portions of the solar cells to gather and distribute electricity from the photovoltaic bristles, thereby reducing the path length of electrons through the transparent conducting oxide layers. Finally in optional block858, a transparent coating may be applied over the bristles in order to provide desirable strength and photon absorption c characteristics. For example, a transparent coating608may seal each bristle in a transparent material providing stability to each bristle to prevent the bristles from breaking. The transparent coating608may be conventional shatterproof material such as ethylene-vinyl acetate (EVA).

In a further embodiment method that uses some of the same processes as in method800, the material forming the cores106may be poured and formed in a mold612instead of being pressed, as illustrated inFIGS. 6I through 6K. As illustrated inFIG. 6I, instead of a die602, the same basic shape may be inverted to form a mold612onto which may be poured the material614to form the cores and supporting substrate. This material614may be a plastic or polymer, but may also be other materials, such as a metal, a ceramic paste, or a liquid glass (e.g., common glass). In this embodiment, the operations of forming the array of cores in block808include pouring the base material614into the mold612, sufficiently covering the mold surface to provide a substrate202as shown inFIG. 6J. The material may be cured in block810in this state before the mold612is removed as shown inFIG. 6K. Thereafter, the operations of depositing absorber layers and outer conductive layers may be accomplished as described above with reference to blocks812-858.

Another embodiment method for forming an array of bristles for a metamaterial device involves plating up metal cores using photolithographic methods to create a template on a substrate. The plating up method is illustrated inFIGS. 9A-9JandFIG. 10. In block1008a metal layer may be deposited over a substrate. As illustrated inFIG. 9Athe metal layer187may be deposited over the substrate202by chemical deposition or physical deposition. In block1010a photoresist layer over the metal layer. The photoresist layer189may be deposited over the metal layer187by chemical vapor deposition or physical deposition as shown inFIG. 9A. The photoresist layer189may be a positive photoresist or a negative photoresist.

In block1012a mask may be applied over the photoresist. As shown inFIG. 9B, the mask195may include holes195athrough which ultraviolet light may pass so that only the photoresist beneath the holes is exposed as shown inFIG. 9B. In block1014the photoresist layer may be exposed to an ultraviolet light through the mask to create exposed photoresist portions189aas shown inFIG. 9B. When a positive photoresist is used, the exposed photoresist portions189amatch the mask holes195a. However, if a negative photoresist is used, ultraviolet light may be able to pass through the entire mask except through solid portions of the mask which block the ultraviolet light. After the ultraviolet light is applied to the photoresist189creating exposed portions189a, the mask195is removed leaving the entire photoresist layer189.

In block1016the method may include developing the photoresist layer to create a template of masked portions. A developer may be used to dissolve only the exposed portions of the photoresist. Assuming the method uses a positive photoresist189, the exposed photoresist portions189aare removed creating voids189bin the photoresist layer that extend to the metal layer187as shown inFIG. 9C. These voids189aalong with the remaining photoresist layer189form a template over the metal layer187.

In block1018additional metal may be added to the metal layer through the photoresist layer using electroplating, chemical vapor deposition or plasma deposition methods, forming metal cores. As shown inFIG. 9Dthe metal cores106may fill the voids189bwithin the photoresist189by electroplating metal in the voids189b. Metal cores may also extend above the photoresist layer. Alternatively, a second metal layer may fill the voids189band covers the remaining portions of the photoresist layer189(not shown). The metal cores106may be the same material as the metal layer187such as gold, copper, nickel, molybdenum, iron, aluminum, or silver, or an alloy of the same.

In block1020the photoresist layer may be removed using conventional methods. As shown inFIGS. 9D and 9E, the metal cores106may only fill the voids189bcreated by the exposed photoresist layer through an electroplating process. When the photoresist layer189is removed, only the formed metal cores106(within voids189b) remain. Alternatively, if a second metal layer fills the voids189band covers the photoresist layer189, a lift-off process known in the art may remove the photoresist layer189and the second metal layer leaving only the metal cores106. The resulting metal cores106from the lift-off process may have height greater than the voids189b.

In block1040a first absorber layer (i.e., sublayer)105may be deposited over the metal core106for metamaterials200illustrated inFIG. 9F. In an embodiment, the first absorber layer105may include a semiconductor material. For example, the first absorber layer105may include silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, cadmium sulfide, gallium arsenide, copper indium selenide, and copper indium gallium selenide. In an embodiment, the first absorber layer105may be deposited over the metal core106by electroplating, chemical vapor deposition, atomic layer deposition, etc. In an embodiment, the first absorber layer105may be deposited over the inner conductive layer107by sputtering, electron beam, pulsed laser deposition, etc.

In block1042a second absorber layer104may be deposited over the first absorber layer105for metamaterial200as illustrated inFIG. 9G. Any deposition method used with respect to the first absorber layer105may also be used with the second absorber layer104. In an embodiment, the second absorber layer104may include silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, cadmium sulfide, gallium arsenide, copper indium selenide, and copper indium gallium selenide. In an embodiment, the second absorber layer104may be an absorber sublayer or region comprising the same material as the first absorber layer105with a different dopant. For example, the first absorber layer105may be p-doped amorphous silicon and the second absorber layer104may be n-doped amorphous silicon. In an embodiment, the second absorber layer104may be an absorber sublayer comprising a different material as the first absorber layer105. For example, the first absorber layer105may be p-doped cadmium telluride and the second absorber layer104may be n-doped cadmium sulfide.

In some implementation multiple absorber layers may be applied. So in optional block1046, one, two or more additional absorber layers may be applied over the previous layer in a manner similar to the process steps in blocks1040and1042. As shown inFIG. 9H, in block1048, an outer conductive layer103may be deposited over the last absorber layer (e.g., second absorber layer104), such as by chemical deposition or physical deposition.

As illustrated inFIG. 9I, additional outer conductive layers may be applied in optional block1052. In an embodiment, the outer conductive layers may include a transparent non-conductive layer103a(e.g., an optical transparent polymer) and a conductive layer103b(e.g., a transparent conducting oxide). Although the outer conductive layer shown inFIG. 9Iincludes two layers, any number of layers may make up the outer conductive layer103. The non-conductive layer103aillustrated inFIG. 9Imay be a conformal layer which may act as a protective coating similar to the transparent coating608described below. The conformal non-conductive layer103amay be added by dip coating, chemical vapor deposition, physical deposition, and atomic layer deposition, and evaporation techniques.

In optional block1056, current conducting traces may be added to the metamaterials200and300. As explained later with reference toFIGS. 23 and 25, the current conducting traces may be added by creating a template using photolithography and depositing a highly conductive material in a selected position from the template. The current conducting trace may be deposited on the metamaterial by any known deposition method such as chemical vapor deposition, physical deposition, plating, or ink jet material deposition. The ink jet deposition methods may utilize piezoelectric ink jets to add silver or other colloidal conductive material to the desired position without damaging the metamaterial.

Alternatively, the current conductive traces may be added by etching with laser ablation in combination with a deposition method such as ink jet. Tuned wavelength lasers may etch desired layers by controlling the laser's wavelength for different layers within the metamaterial. Once etching is complete, the method may include adding the electrical connections such as the current conducting traces at the desired positions on the metamaterial by chemical vapor deposition, physical deposition, plating or inkjet deposition.

As a further alternative, the metamaterial may be etched using ink jet technology to apply an acid to precise locations followed by applying the conductive material using the same technology, or any other deposition method known in the art.

Regardless of method used, the current conducting traces may allow for efficient transfer of electricity by adding a lower resistant electrical path within the metamaterials.

In optional block1058a transparent coating may be deposited over the bristles. As illustrated inFIG. 9J, the transparent coating608is different from the outer conductive layer103and its sublayers103aand103b. The transparent coating608may completely fill the voids between each bristle and extending beyond the height of each bristle. As shown, the transparent coating608may not be conformal, thus leading to deposition methods that use liquid solutions. Accordingly, the method of depositing transparent coating608may include one or more of the following: immersion coating techniques, spray gel techniques, extrusion techniques, a spreader bar, photoresist techniques, sol gel techniques, or any other methods known in the art. The transparent coating608may seal each bristle providing stability and preventing them from breaking, as well as insulating each bristle from any heat created by the metamaterial device. Observations and experimentations also indicate enhanced peak power generation as the sun translates across the sky for a metamaterial device with a transparent coating608having an index of refraction similar to glass (e.g., around 1.5). All of these benefits may add enhanced power performance and total power generation of the metamaterial device.

A further method for forming an array of bristles for metamaterial200includes forming bristles by etching vias in a substrate through a photolithographic template. The method includes adding an inner conductive layer107and a base layer202bover the original substrate202aand in the vias. The method then includes turning the metamaterial device over and depositing absorber layers104,105, outer conductive layers103a,103band a transparent coating over the inner conductive layer. This via method is illustrated inFIGS. 11A-11LandFIG. 12.

In block1210a photoresist layer may be deposited over the substrate. The photoresist layer189may be deposited over the substrate202aby chemical vapor deposition or physical deposition as shown inFIG. 11A. AlthoughFIGS. 11B-11Dillustrates a positive photoresist, the photoresist layer189may be negative photoresist.

In block1212a mask may be deposited over the photoresist layer. The mask195may be any suitable mask known in the art. As shown inFIG. 12B, the mask195may include mask holes195a. Alternatively, if using a negative photoresist, the pores195amay be filters for blocking ultraviolet light.

In block1214the method may include exposing an ultraviolet light to the photoresist layer through the mask. The ultraviolet light from the ultraviolet light source193passes through the mask holes195ainto the photoresist layer189creating exposed portions189aof the photoresist layer as shown inFIG. 11B. The exposed photoresist portions189amatch the mask holes195a. However, if a negative photoresist is used, ultraviolet light may be able to pass through the entire mask except through filters where at the locations of mask holes195a, which block the ultraviolet light. Regardless, after the ultraviolet light is applied to the photoresist layer189creating exposed portions189a, the mask195is removed leaving the entire photoresist189.

In block1216the method may include developing the photoresist layer to create a template, such as by using developer to dissolve the exposed portions of the photoresist as shown inFIG. 11C. After dissolving the required portions of the photoresist layer, the remaining photoresist layer189portions forms a template over the substrate202a.

In block1218the substrate may be etched through the template creating vias. Etching may include wet etching or dry etching. Regardless of the etching technique, vias1103are formed from within the substrate202a.

In block1220the photoresist layer may be removed as shown inFIGS. 11D-11E, leaving only the original substrate202awith formed vias1103. Any process known in the art may remove the photoresist layer189from the substrate. For example, the photoresist may be removed by stripping or dissolving the remaining portion of the photoresist.

In block1222an inner conductive layer may be deposited in the vias. As shown inFIG. 11F, the inner conductive layer107may be deposited as a layer that covers the bottoms and the sides of the vias1103as well as covering the top of the substrate202a. Although the method steps do not explicitly show it, the inner conductive layer107may include multiple layers similar to the outer conductive layer103later described with reference to blocks1248,1450, and1452.

As shown inFIG. 11G, in block1224the base layer may be deposited over the inner conductive layer107. Although the base layer202bis a separate layer than the original substrate202a, it may be the same material as the original substrate202a. Alternatively, the base layer202bmay be a different substance. It should be noted, that althoughFIG. 11Gillustrates the base layer202bcompletely fills the vias1103, the base layer202bmay only partially fill the vias1103and may be deposited similar to the inner conductive layer107resulting in an unfilled void and a non-solid core.

In block1226the device may be turned over, and the substrate etched in block1228.FIG. 11Hillustrates the metamaterial device turned over (i.e., flipped 180 degrees) as well as the original substrate etched away leaving the inner conductive layer107and the base layer202b. A wet etching process (i.e., using acid) or a dry etching process may remove the original substrate202a.

In block1240, a first absorber layer (i.e., sublayer)105may be deposited over the inner conductive layer107for metamaterial200as illustrated inFIG. 11I. In an embodiment, the first absorber layer105may include a semiconductor material. For example, the first absorber layer105may include silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, cadmium sulfide, gallium arsenide, copper indium selenide, and copper indium gallium selenide. In an embodiment, the manufacturing system may add the first absorber layer105over the metal core106by electroplating, chemical vapor deposition, atomic layer deposition, etc. In an embodiment, the manufacturing system may add the first absorber layer105over the inner conductive layer107by sputtering, electron beam physical deposition, pulsed laser deposition, etc.

In block1242a second absorber layer may be deposited over the first absorber layer105for metamaterial200as illustrated inFIG. 11I. Any deposition method used to deposit the first absorber layer105may be used to deposit the second absorber layer104. In an embodiment, the deposition method for the second absorber layer104may be the same deposition method used for adding the first absorber layer105. In an embodiment, the second absorber layer104may include a semiconductor material. For example, the second absorber layer104may include silicon, amorphous silicon, polycrystalline silicon, single crystal silicon, cadmium telluride, cadmium sulfide, gallium arsenide, copper indium selenide, and copper indium gallium selenide. In an embodiment, the second absorber layer104may be an absorber sublayer or region comprising the same material as the first absorber layer105with a different dopant. For example, the first absorber layer105may be p-doped amorphous silicon and the second absorber layer104may be n-doped amorphous silicon. In an embodiment, the second absorber layer104may be an absorber sublayer comprising a different material as the first absorber layer105. For example, the first absorber layer105may be p-doped cadmium telluride and the second absorber layer104may be n-doped cadmium sulfide.

As mentioned above, in some implementations multiple absorber layers may be applied, so in optional block1246such additional absorber layers may be over the previous layer in a manner similar to the process steps in blocks1240and1242. As shown inFIG. 11J, in block1248, an outer conductive layer103may be deposited over the last absorber layer (e.g., second absorber layer104). In optional block1252, multiple outer conductive layers may be applied as illustrated inFIG. 11K. As discussed above, such outer conductive layers may be applied using chemical deposition or physical deposition.

In optional block1256, current conducting traces may be deposited on the metamaterials200. As explained later with reference toFIGS. 23 and 25, the current conducting traces may be added by creating a template using photolithography and depositing a highly conductive material in a selected position from the template. The current conducting traces may be deposited on the metamaterial by any known deposition method such as chemical vapor deposition, physical deposition, plating, or ink jet material deposition. The ink jet deposition may utilize piezoelectric technology and add silver or any other colloidal material to the desired position without damaging the metamaterial. Alternatively, the current conductive traces may be added by etching with laser ablation in combination with a deposition method such as ink jet techniques. Tuned wavelength lasers may etch desired layers by controlling the laser's wavelength for different layers within the metamaterial. Once etching is complete, the method may include adding the electrical connections such as the current conducting traces at the desired positions on the metamaterial by chemical vapor deposition, physical deposition, plating or inkjet deposition. As a further alternative, the metamaterial may be etched by ink jet technology using acid followed by deposition of conductive material using the same technology or any other deposition method known in the art. Regardless of method used, the current conducting traces may allow for efficient transfer of electricity by adding a lower resistant electrical path within the metamaterials.

As illustrated inFIG. 11L, in optional block1258a transparent coating may be applied over the bristles. Such a transparent coating608may be different from the outer conductive layer103and any sublayers103aand103b. The transparent coating608may fully fill the voids between each bristle and extend beyond the height of each bristle. As shown, the transparent coating608may not be conformal thus leading to deposition methods that use liquid solutions. Thus, the method of depositing transparent coating608may include using one or more of the following immersion coating, spray gel techniques, extrusion techniques, a spreader bar, photoresist techniques, sol gel techniques, or any other methods known in the art. In an embodiment, the transparent coating608may be a shatterproof material such as EVA. The transparent coating608may seal each bristle providing stability and to prevent them from breaking as well as insulate each bristle from any heat created by the metamaterial device. Observations and experimentations also indicate enhanced peak power generation as the sun translates across the sky for a metamaterial device with a transparent coating608having a index of refraction similar to glass (e.g., around 1.5). All these benefits may add enhanced power performance and total power generation of the metamaterial device.

A further method for forming an array of bristles for a metamaterial200includes forming the bristles by etching vias in a substrate through a photolithographic template. Bristles are formed within the vias by depositing an outer conductive layer, absorber layers, an inner conductive layer, an optional base layer. After forming the bristles, the metamaterial may be turned over where the original substrate is left intact serving as a protective coating and an optical enhancement for the metamaterial200. This via method is illustrated inFIGS. 13A-13LandFIG. 14. As shown inFIG. 13A-13Land the method steps inFIG. 14, an etching technique may be used to create vias, which is particularly useful when using a glass substrate.

In block1410a photoresist may be deposited over the substrate. The photoresist layer189may be deposited over the substrate202aby spin on, spray on, or other controlled flow methods know in the art as shown inFIG. 13A. AlthoughFIGS. 13B-13Dillustrate a positive photoresist, the photoresist layer189may be negative photoresist.

In block1412a mask may be positioned over the photoresist layer. The mask195may be any suitable mask known in the art. As shown inFIG. 12B, the mask195may include mask holes195a. Alternatively, if using a negative photoresist, the pores195amay be filters for blocking ultraviolet light.

In block1414the method may include exposing an ultraviolet light to the photoresist layer through the mask. The mask195may be any suitable mask known in the art. As shown inFIG. 13B, the mask195may include mask holes195a.

In block1416the method may include developing the photoresist layer to dissolve the exposed portions of the photoresist layer. Assuming a positive photoresist layer189, the exposed portions189aare removed creating voids189bin the photoresist layer that extend to the substrate202aas shown inFIG. 13C. After dissolving the required portions of the photoresist layer189, the remaining photoresist layer189forms a template over the substrate192.

In block1418the substrate may be etched through the template creating vias. Etching may include wet etching or dry etching. Regardless of the etching technique employed, vias1103are formed from within the substrate192.

In block1420the photoresist layer may be removed leaving the substrate192with formed vias1103as shown inFIGS. 13D-13E.

Since the outside layers of the photovoltaic bristles are laid down first, conductive traces used to draw current from the photovoltaic cells may be laid down as a first step. Thus, in optional block1421, conductive traces may be applied to the substrate. Vias for such conductive traces may be formed as part of the operations in blocks1410-1420. Alternatively, conductive traces may be applied to the substrate using dedicated photolithography steps, laser ablation steps, and deposition steps such as those described above and below. In a particular embodiment, the conductive traces may be applied using spray jet techniques. In block1422an outer conductive layer may be deposited in the vias, such as by chemical vapor deposition or physical deposition. If conductive traces are prior to the outer conductive layer, the method may include depositing the outer conductive layer103over the conductive traces as a conformal film.

Although not shown inFIGS. 13A-13L, the metamaterial may include an outer conductive layer103with multiple sublayers. So, in optional block1452another outer conductive layer may be applied over the previous layer, essentially repeating blocks1450and1452. As shown inFIGS. 13G-13H, in block1440a first absorber layer may be deposited on the outer conductive layer(s), and in block1442a second absorber layer may be deposited over the first absorber layer. The first and second absorber layer104,105may be applied by chemical vapor deposition.

In block1446additional absorber layer applied over the previous layer in a manner similar to the process steps in blocks1440and1442. In block1448, an inner conductive layer107may be applied over the last absorber layer (e.g., second absorber layer105). In an embodiment, the method may include adding only two absorber layers104,105and thus the inner conductive layer107is deposited over the last absorber layer105by chemical deposition or physical deposition as shown inFIG. 13I. Although the method steps do not explicitly show it, the inner conductive layer107may also include multiple layers similar to the outer conductive layer103.

In block1424a base layer may be deposited. As shown inFIG. 13J, the base layer202may be different from the substrate192associated with block1410. The base layer202may be deposited over the inner conductive layer107and serves as the actual bottom substrate of the metamaterial device once the vias are turned over. The base layer202may fill the vias1103creating bristles with solid cores. Alternatively, as shown inFIG. 13J, the base layer202may not fill the vias1103, creating bristles with non-solid cores. Regardless, the base layer202may be deposited over the inner conductive layer107by any method known in the art.

In block1426the metamaterial may be turned over as shown inFIG. 13K, so that the bristles are turned upright presenting the original substrate192covering the outer conductive layer103at the top and the base layer202at the bottom of the device. In optional block1460the substrate may be further processed, such as to form an antireflection layer or rough outer surface192aas shown inFIG. 13L.

In an alternative embodiment method, lasers2401may create vias1103out of a substrate or index matched material as illustrated inFIGS. 13M through 13O. The lasers2401may be controlled in terms of exposure time and energy in order to control the depth and size of the vias. After creating the vias1103, the method1400operations described above with references to blocks1421,1448,1452,1440,1442,1446,1442,1422,1424,1426,1458, and1460may be followed.

Stamps may create vias out of a substrate such as a transparent polymer. When using a polymer, a UV source may cure the stamped vias creating a more rigid structure followed by adding conductive layers, absorber layers, and a base layer. The stamping via method for forming an array of bristles for a metamaterial device is illustrated inFIGS. 15A-15JandFIG. 16.

In block1608an array of vias may be formed out of the processed polymer. As illustrated inFIGS. 15A-15B, a stamping process may be used to create vias1103out of a polymer substrate192. In block1610the formed polymer may be cured or otherwise treated to yield desired material properties. For example, such curing/treating may include heating and/or exposure to an ultraviolet light source193.

The stamping process may include a rolling press or rolling die to create vias1103on a substrate192similar toFIG. 15B. When using a rolling press or a rolling die, a roll-to-web and a web-to-plate sub-process may create the associated stamps and vias method1600. The rolling press or rolling die sub-process is described in more detail below with reference toFIGS. 33A-33G, 34, 35A-35E, 36A-36E.

Similar to method1400, the method1600includes laying down the outside layers of the photovoltaic bristles are laid down first, so conductive traces used to draw current from the photovoltaic cells may be laid down prior to the outer conductive layer103. Thus, in optional block1612, conductive traces may be applied to the substrate. Vias for such conductive traces may be formed as part of the operations in blocks1608-1610. Alternatively, conductive traces may be applied to the substrate using dedicated photolithography steps, laser ablation steps, and deposition steps such as those described above and below. In particular embodiment, the method may include applying conductive traces using a spray jet techniques. In block1622an outer conductive layer may be deposited in the vias. If conductive traces are added prior to the outer conductive layer103, the method may include depositing the outer conductive layer103over the conductive traces as a conformal film. As illustrated inFIG. 15D, the outer conductive layer103may be deposited over the polymer192and in the vias1103.

Although it is not shown inFIGS. 15A-15J, multiple outer conductive layers103or sublayers may be applied. So, in optional block1652additional outer conductive layers may be applied over the previous layer.

As shown inFIGS. 15E-15F, in block1640a first absorber layer may be applied over the outer conductive layer(s), and in block1642a second absorber layer may be deposited over the first absorber layer. The method may deposit the first and second absorber layer104,105by chemical vapor deposition. In optional block1646additional absorber layers may be deposited over the other absorber layers in a manner similar to the process steps in blocks1640and1642.

As shown inFIG. 15G, in block1648, an inner conductive layer107may be applied over the last absorber layer (e.g., second absorber layer105), such as by chemical vapor deposition or physical deposition. The inner conductive layer107may also include multiple layers similar to the outer conductive layer103earlier described with reference to blocks1622,1650, and1652.

As shown inFIG. 15H, in optional block1624a base layer may be applied. The base layer202may be different from the polymer192applied in block1608because the base layer202is deposited over the inner conductive layer107and serves as the actual bottom substrate of the metamaterial device once turned over. Although the polymer192may be of the same material as the base layer202, the polymer192may serve as an outer transparent coating to the metamaterial device once the metamaterial is complete. The base layer202may fill the vias1103creating bristles with solid cores. Alternatively, as shown inFIG. 15J, the base layer202may not fill the vias1103, creating bristles with non-solid cores. Regardless, the base layer202may be deposited over the inner conductive layer107by any method known in the art.

As shown inFIG. 15I, in block1626the metamaterial may be turned over for further processing. In optional block1660the substrate192may be processed to give it desired physical properties, such as hardening or polishing. The processing may include forming an antireflection layer or rough outer surface192aas shown inFIG. 15J.

In a further embodiment method that uses some of the same processes as in method1600, material1112in which vias1103are poured into a mold1110instead of being pressed, as illustrated inFIGS. 15K through 15M. As illustrated inFIG. 15K, instead of a die, the same basic shape may be inverted to form a mold1110onto which may be poured the material1112to form the vias1103and supporting substrate. This material1113may be a transparent plastic, polymer or glass that will ultimately have the desired optical properties in the finished product. In this embodiment, the operations of forming the array of vias1103in block1608include pouring the base material1112into the mold1110, sufficiently covering the mold surface to provide a substrate1112as shown inFIG. 15L. The material may be cured in block1610in this state before the mold1110is removed as shown inFIG. 15M. Thereafter, the operations of depositing outer conductive layers, absorber layers and inner conductors may be accomplished as described above with reference to blocks1612-1626.

As a further alternative embodiment, vias may be formed by adding an index-matched nano-imprinted layer over a substrate. The nano-imprinted layer includes the vias for methods1200,1400,1600and may use suitable nano-imprinting techniques known in the art. For example, methods1200,1400, and1600may include depositing a nano-imprinted layer material with an index of refraction of 1.5 over a glass or polymer substrate.

As mentioned with reference to block808ofFIG. 8forming an array of cores out of the processed polymer may include using a rolling die or rolling press. Similarly, with reference to block1608ofFIG. 16, forming an array of vias may also include using a rolling die or rolling press. Although a rolling press may be directly applied to a substrate or a moldable layer on top of the substrate, using such a method may damage a master template having a particular pattern for creating the cores or vias. Thus, to increase yield and throughput of creating substrates with an array of cores or vias, a master template may be used to create daughter templates on a web, and each daughter template web may be applied to a substrate to create the desired core or via pattern in a surface material that will be subsequently processed to form the solar arrays. For example, a master template including cores may imprint vias on a substrate applied to a web creating a daughter template. The daughter template with vias may then be applied to a substrate to create cores on the substrate. After curing to increase material strength of the newly formed cores, the substrate may be further processed using embodiment methods such as described above with reference toFIG. 8and blocks810-858. As an alternative example, a master template including vias may be applied to a substrate on a web to create a daughter template featuring rods that may then be applied to a substrate to imprint vias into the substrate (or a layer over a substrate). The via imprinted substrate may be further processed using embodiment methods such as described above with reference toFIG. 16and blocks1612-1660.

An embodiment method3400for manufacturing an array of cores for photovoltaic bristles using a rolling press or die is illustrated inFIGS. 33A-33GandFIG. 34. Using a rolling press or die method as described below may enable processing methods that reduce the number of defects in fabricating photovoltaic bristles by creating reusable master templates and daughter dies that may be inspected with inspection results used in a feedback control system to bypass imperfect portions.

Referring toFIGS. 33A-33GandFIG. 34together, in block3402of method3400an original master may be created to form a patterned array of bristles for the metamaterial device. Stamping processes such as nano-imprint lithography may create the original master3306with rods3308from a flexible material as illustrated inFIGS. 33A and 33B. Any known process in the relevant art may be used to create such master templates. Companies such as EVG, Obducat, NIL Technology, Nanoex, Molecular Imprints, and Süss Microtech work with nanoimprint lithography and have refined reliable nanoprint lithography techniques. As an alternative, traditional photolithography also may create the original master.

If using nanoimprint lithography, the process may include imprinting the desired pattern onto the original master3306created out of a flexible material such as a polymer or polydimethylsiloxane (PDMS). In optional block3404a suitable metal, such as nickel, may be electroformed over the original master to create a rigid master template or shim. Such metal plating may also be applied after the master is formed into or onto a roller as described below with reference to block3408. The rigid master template may be used to create flexible master templates such as the master webs described below. Whether created by the rigid master template or formed as the original master, flexible templates such as PDMS may be used to imprint patterns on more rigid materials.

The master template may be formed in one piece, or a large master template may be formed from stitching together the master template in block3406. Whether the master template is flexible or rigid, multiple masters may be stitched together as illustrated inFIG. 33C. Once the large master template is formed, in block3408, the large master template may be wrapped around a drum roller (or formed into a roller) as illustrated inFIG. 33D. The drum roller may then be used for subsequent processing in a roll-to-web system as described below.

The web material may be a polymer or polyester film, such a Dupont's Mylar®. By way of example, the web material may have a thickness of 25 to 250 microns, a length of 100 to 2000 feet, and a width of 0.5 to 6 feet. In block3410a first moldable material, such as a lacquer, spin-on-glass coatings, a sol-gel, or PDMS, may be applied to a web to coat a thin layer of the material over the web. Since the web itself is flexible, a flexible material such as PDMS may be less restricting than sol-gel, spin-on-glass coatings when moving through the rollers and subsequent processing.

In block3412the first pattern from the large master template may be imprinted to the coated web to create a second imprint pattern on the web as illustrated inFIG. 33E. In this process operation, the drum roller with a rod pattern imprints vias3314binto the coated material on the web by pressing the web and the coated material against a transfer spacing roller3318. Alternatively, the drum roller with a via pattern creates a rod pattern from the coated material on the web (not shown). In block3414the second imprint pattern on the web may be cured or otherwise processed to increase its material strength. An ultra violet light or a thermal mechanism for applying heat may be used to cure the second imprinted pattern. If using PDMS as a moldable material, a thermal mechanism may apply heat to cure the imprinted pattern. The result of these processor operations is a daughter die web suitable for use in subsequent operations for creating a substrate with cores (or alternatively vias) on a substrate that will eventually become solar cells. As an alternative embodiment method, the web itself may be a flexible substrate and with a cured second imprinted pattern the web substrate may be suitable for use in embodiment methods (e.g., method800or1600) describe herein to create metamaterial devices.

In block3416the master web may be installed on rollers in a web-to-plate process. In block3418a moldable material may be applied to a substrate or surface on which the solar arrays will be formed. For example, the moldable material may be a polymer that may be cured (e.g., by exposing it to ultra violet radiation) after it is applied to a substrate or support surface and imprinted as described below. As another example, the moldable material may be a flexible thermally curable sol-gel that is applied to a substrate or support surface and imprinted as described below. Alternatively, the substrate itself may be a moldable material and thus the operations in block3418may involve creating the substrate of moldable material.

As illustrated inFIG. 33F, the second pattern from the master web may be imprinted on the moldable material to create a third imprint pattern on or in the substrate in block3420. In the example illustrated inFIG. 33F, a daughter die web with vias3314bwill form cores3320aof the moldable material3320on the substrate3322. As described below, the process pressing the daughter die3316into the moldable material3320on the substrate3322may be controlled so that the two surfaces come together without sliding, which could deform or fail to form the desired cores3320a(or vias).

In block3422the cores3320a(which are the third imprinted pattern) illustrated inFIG. 33Gor vias (not shown) may be cured or otherwise processed to increase their strength and rigidity before subsequent processing according to embodiment methods described above with reference toFIGS. 8 and 16. As mentioned above, such curing or processing of the cores or vias may involve exposure to ultra violet light (e.g., to increase cross linking in a polymer material) or heating (e.g., to convert sol gel into a glass or ceramic).

FIG. 35Aillustrates an embodiment roll-to-web system3500suitable for use in the operations described above with reference to blocks3406-3414in method3400. The illustration of the roll-to-web system3500inFIG. 35Aand the following description is provided as an illustrative example and is not intended to limit the scope of the claims as other roll-to-web system configurations (e.g., different roller configurations, different web paths and different sequences of operations) are possible without departing from the scope of the present invention.

In the embodiment roll-to-web system3500illustrated inFIG. 35A, a web material may pass through a series of rollers configured and controlled to maintain tension and orientation, apply a moldable material to the web, and imprint a first pattern from a master die on the moldable material to create a second pattern of cores or vias in the moldable material. That second pattern of cores or vias in the moldable material may be subsequently cured/processed to form the daughter die on the web.

The roll-to-web system3500may include an unwind roller3502that may be driven by an unwind motor3502aconnected to an unwind motor controller3502bto control the rotation of the unwind roller. An uncoated web3501amay be installed on the unwind roller3502and be unwound throughout the roll-to-web system3500. From the unwound roller3502, the uncoated web3501amay roll over a tension sensor3312. The tension sensor may provide web-tension information to the unwind motor controller3502bwhich may use this information as feedback along with torque sensing feedback from the unwind motor3502ato control web tension through the roll-to-web system3500.

The uncoated web3501amay travel over a tracking roller3504, which may be adjusted by the control system to control the lateral position of the web in the system in response to signals from an edge sensor3505. By adjusting the tracking roller3504, the web's position on the rollers may also be adjusted to an optimum position/orientation to prevent skewing of the pattern on the web. For example, if the web is too far to the left side of the rollers, the tracking roller may be adjusted to move the web back toward the center of the rollers.

The uncoated web3501amay travel through S-wrap rollers3506, which control the velocity and tension of the web3501as it passes through the roll-to-web system3500. The S-wrap rollers3506may adjust the velocity of the web3501traveling through the roll-to-web system3500based on data from drum roller speed encoders3521. In this manner, the S-wrap rollers may serve to synchronize the speed of the web as it meets with the drum roller (which includes the master die) that imprints the pattern on the web3501. Closely controlling the relative speed of the web and the drum roller reduces the chance for defects to be printed on the daughter dies as well as the chance for damaging the master die on the drum roller.

The uncoated web3501amay travel between a transfer roller3507and a rubber roller3508. The transfer roller3507picks up a layer of moldable material3509and applies the layer to the web, while a shear roller3510ensures the applied layer is of the desired thickness. As the uncoated web3501atravels between the rubber roller3508and the transfer roller3507, the transfer roller3507collects the moldable material3509on the transfer roller3507. Prior to the transfer roller3507applying the first moldable material3509to the uncoated web3501a, the shear roller3510removes excess moldable material3509from the transfer roller3507to ensure a consistent coating on the web3501a. A rubber roller3508, potentially made of high durometer ground rubber, may provide support to the web3501while the transfer roller3507applies the first moldable material3509.

After the transfer roller3507applies the first moldable material3509to the uncoated web3501a, a thickness sensor3511may measure the thickness of the first moldable material3509on the coated web3501b. The thickness sensor may be used by a control system that may send a signal to cause the shear roller3510shift position in order to maintain a consistent thickness and compensate for any thickness variations in the uncoated web3501a. For example, if the thickness sensor indicates that the coated web's thickness is higher than a set point, the control system may cause the shear roller3510to move closer to the transfer roller3507, thereby removing more of moldable material3509from the transfer roller3507prior to its application to the uncoated web3501a.

The coated web3501bpasses between the drum roller3512, which includes the master template, and a transfer spacing roller3513in order to imprint the daughter die pattern in the moldable material on coated web3501b. The moldable material on the coated web3501baccepts the first pattern as the coated web3501bis pressed against the drum roller3512to create a second pattern in the moldable material3509. The speed of rotation of the drum roller3512is closely controlled by a control system so that it spins in conformity with the speed of the moving web3501to precisely imprint the first pattern on the web. To do so, the control system may receive signals from speed encoders3521coupled to the S-wrap roller(s)3506and use this information in a closed-loop control algorithm to ensure that the surface of the drum roller matches the speed of the web3501passing beneath or over it. Depending on the type of moldable material, the imprinted web3501cmay be cured/processed (e.g., thermally or with ultra violet light) by a curing mechanism3514.

The cured web3501dmay travel over a support roller3515and a second tension sensor3516prior to being collected on a wind roller3518. The wind roller3518may be driven by a wind motor3518acontrolled by a wind motor controller3518b. The wind motor controller3518bmay adjust the wind up speed of the wind roller3518based on the torque of the wind motor3518aand signals from the second tension sensor3516to assist in maintaining proper web tension and a speed of advance.

The roll-to-web system3500may also include an inspection camera3519that may scan the cured web3501dfor defects. Images from the inspection camera3519may be processed by a computer to identify areas of defects, which may be recorded against position on the web in a web-mapping database3520that may be used in controlling the final printing process. As described below, a web-to-plate system3600may access the web-mapping database3520and adjust its system parameters (e.g., web speed, substrate linear speed, sheet gap mechanism) to avoid applying any mapped defects in the web3501dto substrate being processed in such a system.

The roll-to-web system may also include a moldable material processing system3522. The moldable material processing system3522may be fluidly connected to a moldable material container that houses the moldable material3509for the transfer roller3507. The moldable material processing system3522may recirculate the moldable material3507through system components (filters, heat exchangers, etc) to ensure the moldable material3507is clean and at the proper temperature for applying to the web3501a. The moldable material processing system3522may add moldable material3509as needed to ensure ample moldable material for the roll-to-web system3500.

Various portions of the roll-to-web system3500may be subject to humidity and temperature controlled to ensure that the moldable material3509adheres to the web3501and that the moldable material3509accepts the desired pattern from the drum roller3512with minimal defects. This may be especially important if the moldable material3509is a sol-gel or other thermally cured material.

FIGS. 35B-35Eillustrate example control systems that may be used to control various portions and components of the roll-to-web system3500described above enable high precision printing from the drum roller3512to the web3501.FIG. 35Billustrates the electrical controls between the tension sensor3503, the unwind motor3502a, and the unwind motor controller3502b. The unwind motor controller3502bmay utilize a PID controller system that adjusts the unwind motor3502abased on inputs from the tension sensor3503, a tension sensor set point, a torque input from the unwind motor3502a, and a torque set point. A skew actuator controller3504aillustrated inFIG. 35Cmay adjust the position of the tracking roller3504based on data from the edge sensor3505and a set point. An S-wrap motor controller3506aillustrated inFIG. 35Dmay control speed of the s-wrap rollers3506and the corresponding web velocity through the roll-to-web system. The S-wrap motor controller3506acontrols S-wrap rollers3506to synchronize the web velocity with the drum roller's rotational speed based on data from the speed encoder3521and a set point. The wind motor controller3518billustrated inFIG. 35Eis similar to the unwind motor controller3502billustrated inFIG. 35B, except that the wind motor controller3518baccepts input data based on the second tension sensor3516, a tension set point, torque data from the wind control motor3518a, and a torque set point.

FIG. 36Aillustrates an embodiment web-to-plate system3600that may be suitable for forming the desired pattern of cores or vias on the substrate as described above with reference to blocks3416-3422in method3400. The illustration of the web-to-plate system3600inFIG. 36Aand the following description is provided as an illustrative example and is not intended to limit the scope of the claims as other web-to-plate system configurations (e.g., different roller configurations, different web paths and different sequences of operations) are possible without departing from the scope of the present invention.

The web-to-plate system3600may process a substrate that moves through the system on a linear drive mechanism by applying a moldable material to the surface of the substrate. As an alternative, if the substrate is the second moldable material, then a moldable material does not need be added to the substrate. The moldable material applied to the substrate in this process may be different from the moldable material that is applied to the web and used to form the daughter die pattern. The web-to-plate system3600also passes the daughter die web (which has the second template pattern as described above) through a series of rollers that control its tension and speed of advance, and presses it onto the moldable material on the substrate to create a third pattern, which is the desired cores or vias. The web-to-plate system3600has a web subsection and a plate subsection.

The web subsection will be discussed first. The web-to-plate system3600may also include a module or apparatus that cures/processes the third pattern in order to produce the substrate with a pattern of cores or vias suitable for the embodiment processes described above with reference toFIGS. 8 and 16for applying photovoltaic materials.

The web3501don the web-to-plate system3600is weaved through various rollers to control tension and position, similar to the roll-to-web system3500. The web-to-plate system3600may include an unwind roller3602driven/controlled by an unwind motor3602aconnected to an unwind motor controller3602bconfigured to control the rotation of the unwind roller3602. The daughter die web3501dfrom the roll-to-web process described above may be installed on the unwind roller3602. The daughter die web3501dmay travel across a tracking roller3603and an edge guide sensor3604. The edge guide sensor3604may collect information regarding the position of the web3501don the rollers relative to a set point, and send that data to a controller of the tracking roller3603. The controller of the tracking roller may use the data to adjust the position/orientation of the tracking roller3603in order to correct the orientation of the daughter die web3501din the system and prevent web skewing within the rollers.

The web-to-plate system3600may include a tension sensor3606that provides data to an unwind motor controller3602bto enable the unwind motor controller3602bto control the unwind motor3602ato adjust the speed of the unwind roller3606based on tension data. The unwind motor controller3602bmay also use torque data from the unwind motor3602a. Unlike the roll-to-web system3500, in the web-to plate system3600the same tension sensor3606may also be connected to the wind motor controller3608to enable the wind motor controller3608bto control the wind motor3608ato adjust the speed of the wind roller3608based on the same tension data. The tension sensor3606may be positioned after the velocity roller3605.

The web-to-plate system3600may not include S-wrap rollers to control the velocity of the web. Instead, the web-to-plate system3600may use a velocity roller3605to perform a similar function. The velocity roller3605may be connected to a velocity roller motor controller3605a, which may adjust the velocity of the daughter die web3501dto match the linear speed of the substrate based on data acquired from the linear drive controller3601a. The velocity roller controller3605amay also adjust the speed of the web3501dbased on web-mapping data from the web-mapping database3520. For example, if there is a defect in the daughter die web, the velocity roller3605may increase the velocity of the daughter die web3601dat a certain point in time to ensure that the defected portions are not imprinted on the substrate3609a. Alternatively or additionally, the linear drive controller3601amay be controlled to pause the advance of the substrates in order to enable a portion of the daughter die web with a defect to be advanced before imprinting of the next substrate begins.

The daughter die web3501bmay travel around the velocity roller3605past the tension sensor3606to a transfer gap roller3607. The transfer gap roller may aid in pressing the daughter die web3501dagainst the substrate to imprint the second pattern into moldable material on the substrate3609athereby creating the third pattern of cores or vias. Once the daughter die web3501dimprints the second pattern on the substrate3609a, the daughter die web3501dmay be wound around the wind roller3608and used for future processing.

The plate subsection of the web-to-plate system3600includes a linear drive mechanism3610configured to control the linear motion and linear velocity of the substrate3609through the web-to-plate system3600. The linear drive mechanism3610is connected to a linear drive controller3610a, which may control the speed of the substrate3609in the web-to-plate system3600based on data from the sheet gap controller3611a, the web-mapping database3520, and the velocity roller motor controller3605a.

While the pre-imprinting substrate3609ais traveling across the linear drive mechanism3610, the sheet gap mechanism3611may stop the pre-imprinting substrate3609aby a vertical actuation synchronized with the movement of the substrate3609and the daughter die web3501dto reduce imprinting defects. For example, the sheet gap controller3611amay receive web-mapping data regarding a known defect on the daughter die web's pattern from the web-mapping database3520, and in response control the sheet gap mechanism3611to stop the substrate3609afrom moving forward in the system when a defective portion of the daughter die web is present on or near the transfer gap roller3607to avoid printing a defect from the daughter die web3501don to the substrate3609a. As another example, the sheet gap mechanism3611may prevent the substrate3609afrom moving to the second moldable material applicator3612, while the moldable material application is adjusted, refilled, etc. When the sheet gap mechanism is actuated, a sheet gap sensor or trigger may act as an input to other controllers in the system.

After passing the sheet gap mechanism3611, a moldable material applicator3612may apply the moldable material3613over the substrate to create a coated substrate3609b. A thickness sensor3614may detect the thickness of the moldable material on the coated substrate3609band provide feedback to the moldable material applicator3612for adjusting the amount of moldable material applied to the substrate3609a. The coated substrate3609bcontacts the daughter die web3501dwith pressure applied by the transfer gap roller3607so that the second pattern from the daughter die web3501dis imprinted on the coated substrate3609bto create an imprinted substrate3609c.

Depending on the type of moldable material, the imprinted substrate3609cmay be cured or processed in a curing mechanism3615to increase its material strength, such as via thermal and/or ultraviolet radiation curing. After curing, the final substrate3609dis ready for further photovoltaic processing according to an embodiment method described above with reference toFIG. 8orFIG. 16. Further processing may include adding absorber layers, inner conductive layers, outer conductive, microtraces, etc.

FIGS. 36B-36Eillustrate control systems that may be configured to enable high precision printing from the web to the substrate in the web-to-plate system3600.FIG. 36Billustrates electrical controls between the tension sensor3606, the unwind roller motor3602a, and the unwind motor controller3602b. The unwind motor controller3502bmay utilize a PID controller system that adjusts the unwind motor3602abased on inputs from the tension sensor3606, a tension sensor set point, a torque input from the unwind motor3602a, and a torque set point. The tension input may be used as the lowest level input variable and torque from the unwind motor3602aand the wind motor3608amay be the major control variables. The unwind and wind motor controllers3602band3608b, respectively, will look for a minimum value from the tension sensor3606to insure the web has tension. The differential between the wind/unwind torque and a respective set point may be used to determine dynamic wind or unwind force to be applied in order to maintain a desired tension. The wind and unwind controller3602band3608bwill evaluate the differential between the two motor systems to control the web tension. Software may run linear and non-linear proportional loop equations based on an input factor. The integral portion will smooth the interactions and the integral sample rate within a sample window. Due to the sensitive nature of the process and the time constants involved, the derivative portion may act as a dampener. Similar logic may be applied to the control of the roll-to-web system3500. Further details regarding PID logic and control loops may be found in U.S. Pat. No. 4,500,408, entitled Apparatus for and Method of Controlling Sputter Coating.

A skew actuator controller3603aillustrated inFIG. 36Cmay adjust the position of the tracking roller3603based on data from the edge sensor3604and a set point. A velocity controller3605amay control the speed of the velocity roller3605and the corresponding web velocity through the web-to-plate system3600as illustrated inFIG. 36D. The velocity motor controller3605amay control the velocity roller3605to synchronize the web velocity with the linear drive speed controlled by the linear drive controller3610a. The wind motor controller3608billustrated inFIG. 36Eis similar to the unwind motor controller3602bofFIG. 36B, except that the wind motor controller3518amay accept input data based on torque data from the wind control motor3518a, and a torque set point.

FIGS. 17-21illustrate multiple embodiment metamaterials1700,1900,2100with current conducting traces1701,1702,1703,1901,2101applied to reduce electrical resistance within the metamaterials. The current conducting traces1701,1702,1703,1901,2101provide an electrical path for flowing electrons from the outer conductive layer103in metamaterials200,300,400to collector contacts on the edges of the cells. Electrons may travel from the outer conductive layer103via the current conducting traces1701,1702,1703,1901,2101to the outer edge of the metamaterials1700,1900,2100where they connect to bus bars or high capacity conductors. By reducing the electrical resistance within metamaterials1700,1900,2100less electrical energy will be converted to heat and more electrical power may be produced. The embodiment metamaterials1700,1900,2100described below may include current conducting traces1701,1702,1703,1901,2101in any combination or sub-combination.

FIG. 17illustrates a cross-sectional side view of a metamaterial1700, which is similar to metamaterial200but with current conducting traces1701,1702, and1703. In an embodiment, metamaterial1700may include current conducting trace1701on top of the outer conductive layer103of a row of shorter photovoltaic bristles1704. AlthoughFIG. 17shows only one row of shorter photovoltaic bristles1704with a current conducting trace1701on the shorter photovoltaic bristles1704, in an embodiment there may be multiple rows of shorter photovoltaic bristles1704with current conducting traces1701on top.

In an embodiment, metamaterial1700may include current conducting traces1702,1703in different locations than current conducting trace1701. As with the current conducting trace1701, metamaterial1700may include current conducting trace1702on top of the outer conductive layer103, but positioned at the end of the array of photovoltaic bristles201. Metamaterial1700may include current conducting trace1703on top of the substrate202or in contact with the inner conductive layer107to allow efficient electron flow. Electrons may flow from the absorber sublayer105to the outer conductive layer103through the current conducting traces1701,1702to the electrical destination (e.g., electrical storage, electrical converter, or motor) and the circuit is completed by connecting current conducting trace1303to the inner conductive layer107or metal substrate202. Alternatively, electrons may flow from the absorber layer105through the inner conductive layer107to the current conducting trace1303and then to an electrical destination (e.g., electrical storage, power converter, etc).

FIG. 18illustrates the top view ofFIG. 17of metamaterial1700with current conducting traces1701,1702,1703. In an embodiment, metamaterial1700may include current conducting trace1701on top of an array of shortened photovoltaic bristles1704extending along the width of the array. Similarly, current conducting traces1702and1703may extend along in the same direction of the array. Connecting current conducting traces1701and1702to current conducting traces1703may create a complete circuit in the metamaterial1700, thereby allowing current to flow through the array of bristles when struck by photons sufficient to generate electron movement.

FIG. 19illustrates a cross-sectional side view of a metamaterial1900, which is similar to metamaterial200, but with current conducting traces1901,1702,1703. In an embodiment, metamaterial1900may include current conducting trace1901on the outer conductive layer103between the photovoltaic bristles201. As withFIG. 17, metamaterial1900may include current conducting traces1702on the outer conductive layer103and current conducting traces1703on the substrate202and/or in contact with the inner conductive layer107. In contrast withFIG. 17, metamaterial1900may not include a row of shorter photovoltaic bristles1704because current conducting traces1901are between the photovoltaic bristles201on top of the outer conductive layer103. However, in an embodiment, metamaterial1900may include a row of shorter photovoltaic bristles1704with a current conducting trace1701on the shorter photovoltaic bristles1704in addition to the current conducting traces1901positioned between photovoltaic bristles201.

FIG. 20illustrates the top view ofFIG. 19of an array of photovoltaic bristles201on a flat substrate202with current conducting traces1901positioned between photovoltaic bristles201. Similar to the current conducting traces1701,1702,1703inFIG. 18, the current conducting traces1901,1702, and1703extend the entire width of the array. In an embodiment, the current conducting traces1901,1702,1703may extend in any direction. For example, the current conducting traces1901,1702, and1703may extend diagonally, along the length, and/or along the width of the metamaterial1900.

FIG. 21illustrates a cross-sectional side view of a portion of metamaterial2100similar to metamaterial300, but with current conducting traces2101,1702,1703. Metamaterial2100includes current conducting trace2101, which may be located between photovoltaic bristles301as well as at the peak and trough of the slanted substrate surfaces308a,309a,308b,309b. In an embodiment, metamaterial2100includes current conducting traces1702,1703at the ends of the metamaterial2100similar toFIGS. 17 and 19. Current conducting trace1702may be on the outer conductive layer103at the ends of the array of photovoltaic bristles301. Current conducting trace1703may be on top of the substrate302and/or in contact with the inner conductive layer107. In an embodiment, metamaterial2100may include current conducting traces2101on top of the outer conductive layer103and between photovoltaic bristles301located on the peak and/or the trough of the slanted substrate surfaces308a,309a,308b,309b. Although it is not shown inFIG. 21, the metamaterial2100may have current conducting traces2101positioned on the outer conductive layer103on top of shorter photovoltaic bristles1704as shown inFIG. 17. In an embodiment, metamaterial2100may be similar to metamaterial400as it may be without photovoltaic bristles401on slanted substrate surfaces409a,409b. For example, the metamaterial may include current conducting traces2101between photovoltaic bristles401only on alternating slanted substrate surfaces408a,408b, etc.

Photolithographic techniques may be used to deposit the current conducting traces1701,1702,1703,1901, and2101ofFIGS. 17-21on metamaterials200,300, and400. These current conducting traces may be added to the metamaterials regardless of whether the metamaterials are created through stamping, vias, or any other technique. Although photolithographic techniques are used for adding each current conducting trace1701,1702,1703,1901, and2101to the metamaterial device, when adding current conducting trace1703to a metamaterial a different method may be used. Thus,FIGS. 22A-22Fillustrate andFIG. 23describes by the method steps for forming current conducting traces1701,1702,1901, and2101, whileFIGS. 24A-24Jillustrate andFIG. 25describes the methods steps for forming current conducting trace1703. Each method is discussed in turn.

Current conducting traces1701,1702,1901, and2101may be formed on metamaterials200,300, and/or400. In block2302a photoresist layer may be deposited over the metamaterial. As shown inFIGS. 22A and 22B, a photoresist layer189may be deposited over the metamaterial. In block2304a mask may be positioned over the photoresist layer. In block2306the photoresist layer may be exposed to UV light through the mask. As illustrated inFIG. 22C, exposing only a portion of the photoresist189to UV radiation creates an exposed portion189awithin the photoresist layer189. In block2308the photoresist layer189may be “developed” by exposing it to chemicals that remove the exposed portions189aleaving a protective template, and the assembly may be etched to create pores189bshown inFIG. 22D. In optional block2310the substrate may be etched through the template. This step may be required when the metamaterial is formed with vias in methods1400or1500. When creating photovoltaic bristles using vias, the original substrate192(shown inFIGS. 13K and 15I) may form a protective coating over the bristles. Thus, the method may include an etching step to expose the outer conductive layer103through the substrate192before depositing current conducting traces1701,1702,1901, and2101on the outer conductive layer103eventually followed by filling the etched void in the substrate192with a transparent coating. In block2322a current conducting trace may be deposited on the metamaterial. Current conducting traces1701,1702,1901, and2101may be deposited on the outer conductive layer103through a photoresist template as shown inFIG. 22E. In block2312the photoresist layer may be removed. As shown inFIG. 22F, when the photoresist189is removed, only the bristles and the current conducting trace remains. After removing the photoresist, a transparent coasting may be applied to the solar cell covering the bristles and the deposited current conducting trace.

As an alternative to photolithographic techniques, a method for depositing the current conductive traces may include an ink jet device2201illustrated inFIGS. 22G and 22Hto reduce manufacturing cost. The ink jet2201may deposit a conductive trace1901in desired locations (e.g., between bristles) by using colloidal material such as silver without the use of the multiple steps associated with photolithographic techniques. Thus, this alternative may include only one-step of depositing a conductive trace on the metamaterial in block2322.

Current conducting trace1703may be formed by a different method as illustrated inFIGS. 24A-24JandFIG. 25. In block2502a first photoresist layer may be deposited over the metamaterial. As shown inFIG. 24A, a first photoresist layer189may be deposited over and between the bristles of the metamaterial. In block2504a first mask may be positioned over the first photoresist layer. As shown inFIG. 24B, the first mask195may block UV radiation to the photoresist189except through mask portion195a. This controls the UV radiation to the desired portion of the photoresist layer189. In block2506the method may include exposing a UV source to the first photoresist layer through the first mask to create an etching template. As illustrated inFIG. 24B, exposing only a portion of the photoresist layer189to UV radiation creates an exposed portion189awithin the photoresist layer189. After creating the exposed portion189awithin the photoresist, the mask may be subsequently removed from the metamaterial. In block2508the first photoresist layer may be developed. For a positive photoresist layer this includes removing the exposed portion189aleaving a template created by the remaining photoresist layer189with pores189bas shown inFIG. 24C. In block2510the method may include etching the metamaterial through the etching template. As illustrated inFIG. 24D, the photoresist template189controls the etching process by removing only a portion of the outer conductive layer103, the first absorber layer105, and the second absorber layer104. In block2512the first photoresist layer may be removed. As shown inFIG. 24E, after removing the first photoresist layer189, the metamaterial may include a void in the outer conductive layer and the absorber layers. In block2514a second photoresist layer may be deposited over the metamaterial. As shown inFIG. 24Fthe second photoresist layer190covers the bristles and the void in the metamaterial created by the etching step. In block2516a second mask may be positioned over the second photoresist layer. As shown inFIG. 24G, a second mask196may block the UV radiation to the second photoresist layer190except through the second mask portion190a. This controls the UV radiation to the desired portion of the second photoresist layer190. In block2518the method may include exposing a UV source to the second photoresist layer through the second mask. As illustrated inFIG. 24G, exposing only a portion of the second photoresist layer190to UV radiation creates a second exposed portion190awithin the second photoresist layer190. After creating the second exposed portion190awithin the second photoresist layer, the second mask may be subsequently removed from the metamaterial. In block2520the second photoresist layer may be developed. For a positive photoresist this includes removing the second exposed portion190aleaving a template created by the remaining second photoresist layer190with pores190bas shown inFIG. 24H. In block2522a current conducting trace may be deposited on the metamaterial. The current conducting trace1703may be deposited on the inner conductive layer107through the second photoresist pore190bas shown inFIG. 24I. In block2524the second photoresist layer may be removed. As shown inFIG. 24J, when the second photoresist layer190is removed, only the bristles and the current conducting trace1703remains. After removing the photoresist, a transparent coating may be applied to the metamaterial covering the bristles and the deposited current conducting trace.

In another embodiment method that uses some of the same processes as in method2500, the steps for etching may include laser ablation using a wavelength-tuned laser to etch only the desired layers, as illustrated inFIGS. 24K through 24M. This may reduce the number of steps associated with the photolithographic techniques of method2500thereby reducing manufacturing cost. As illustrated, a wavelength-tuned laser2401may be used to etch desired portions of the metamaterial for a conductive trace. Since this technique provides a controlled etching alternative, it allows for any of the methods above to deposit current conducting traces at any point within the method steps.

As an alternative embodiment to the conductive traces described above, high conductive regions may be applied to the various metamaterials though directional deposition such as solid angle physical vapor deposition or ion source deposition. The method may include preferentially coating highly conductive regions with metal while leaving other regions with minimal coating to refrain from blocking entering photons. For example, the method may include coating the area between the vias or bristles ten times as thick as the coating along the sidewalls of the vias or bristles allowing photons to pass through the sidewalls while simultaneously creating a highly conductive region to act as a conductive trace. As another example, the method may include using a thicker conductive coating only on the side of bristles or vias that will receive less exposure to photons during operation of the completed metamaterial. To accomplish the single region deposition, the method may include angling the substrate during the deposition process so that only the desired side receives the highly conductive coating. Regardless of the exact process, the conductive regions may be applied to any of the methods listed above.

Metamaterials200,300,400,1700,1900, and2100formed by any of the processes above may be assembled into a solar panel. As briefly described above, the corrugated shape may be incorporated into an assembled solar panel as illustrated inFIGS. 26-32. The panel assembly may include a corrugated base with panel surfaces angled at approximately 30 to 60 degrees for increasing off-axis photon absorption in metamaterials200with flat substrates as well as increasing the planar bristle density without increasing shadowing, resulting in similar gains in total efficiency and power generation from metamaterials300,400with corrugated substrates. However, the total efficiencies gains are compounded when the panel assembly and metamaterials include a corrugated shape (e.g., metamaterial300in a corrugated solar panel assembly) because the assembled panel benefits from an increase in planar bristle density and off-axis photon absorption.

FIGS. 26-32illustrate an embodiment solar panel3100with a corrugated base2610. Solar panels with a corrugated base2610may be formed by assembling metamaterials200,300,400,1700,1900, and/or2100together.FIG. 26illustrates a perspective view of a section of a solar panel2600. Solar panel section2600may include one or more panel surfaces2602,2604in an alternating fashion on a corrugated base2610. In an embodiment, each panel surface2602,2604may include metamaterials200,300,400,1700,1900, and/or2100with photovoltaic bristles201,301,401. In an embodiment, panel surfaces2602,2604may include the same metamaterial. For example, each panel surface2602,2604may include metamaterials200with a flat substrate202. In an embodiment, panel surfaces2602,2604may include different metamaterials. For example, panel surfaces2602may include metamaterials200with flat substrates202while panel surfaces2604may include metamaterials300with corrugated substrates302. In an embodiment, a first panel surface2602may include metamaterials200,300,400,1700,1900, and/or2100, while a second panel surface2604is without metamaterial200,300,400,1700,1900, and/or2100. For example, solar panel section2600may include a first panel surface2602with metamaterials300alternating along a corrugated base2610with a second panel surface2604without metamaterials. In an embodiment, a second panel surface2604without metamaterials200,300, and/or400may include a reflective film (i.e., a mirror). For example, the first and second panel surfaces2602,2604may alternate along the corrugated base2610with a first panel surface2602with metamaterials400and a second panel surface2604with only a reflective film. Regardless, each panel surface2602,2604rests on the front of a corrugated base2610.

In an embodiment, fasteners2612may be used to fasten the panel surfaces2602,2604to the corrugated base2610with connectors2608. The same fastener2612may also fasten the rails2902(shown inFIG. 29) to the corrugated base2610and the connectors2608. In an embodiment, solar panel section2600may include a buss bar2606with connectors2608to connect the buss bar2606to each metamaterial200,300,400,1700,1900, and/or2100of the panel surfaces2602,2604. In an embodiment, the buss bar2606may connect to the corrugated base2610in a slot2614of the corrugated based2610. The slot2614may provide stability for the buss bar2606as well as allow solar panel section2600to rest on a flat back of the corrugated base2610.

FIG. 27illustrates a top view of solar panel section2600. As illustrated withFIG. 26, the solar panel section2600may include panel surfaces2602,2604, a corrugated base2610, a buss bar2606, fasteners2612, and connectors2608.

FIG. 28illustrates a side view of solar panel section2600. As illustrated, the connectors2608may use a single fastener2612for each pair of panel surfaces2602,2604. The fastener2612may be any means of fastening the connectors2608to the corrugated base2610and the panel surfaces2602,2604. For example, the fasteners2612may utilize a bolt, a joint, a rivet, screws, a pin, clips, latch, etc. In an embodiment, the fastener2612may be metal or metalized to create an electrical pathway from the metamaterials200,300,400,1700,1900, and/or2100of panel surfaces2602,2604to the connectors2608. As referenced inFIG. 26, the corrugated base2610may have a slot2614for the buss bar2606. The slot2614may allow the buss bar2606to connect to the backside of the corrugated base2610and form a flat surface (i.e. flat back) of the corrugated base2610. The flat surface of the backside of the corrugated base2610may allow for a more stable assembly for the completed solar panel2600.

FIG. 29illustrates an exploded view of a solar panel section2600. As illustrated, rail2902may be secured to the corrugated base2610by a securing mechanism2901. The rail2902may be secured to the corrugated base2610by any means possible. For example, the rail2902may be secured to the backside of the corrugated base2610by a rivet, crimping, a bolt, adhesive or any other securing means. In another example, the rail2902may be secured to the corrugated base2610similar to a fastener2612used to fasten the panel surfaces2602,2604to the corrugated base2610. In an embodiment, the rail2902also may be fastened by the fastener2612to panel surfaces2602,2604on the backside of the corrugated base2610opposite the connectors2608. In an embodiment, the rail2902may be fastened to the panel surfaces2602,2604by any means possible including the fastening means as described with reference toFIG. 28. In an embodiment, the buss bar2606may be secured to the corrugated base2610by a securing mechanism2901. In an embodiment, the buss bar2606may be attached to the rail2902with an attachment mechanism2904. The attachment mechanism2904may be any means of attachment. The attachment mechanism may be the same as the securing mechanisms2901, or the fasteners2612as described above.

In an embodiment, the rails2902and the buss bars2606may be electrically connected to the metamaterials200,300,400,1700,1900, and/or2100of panel surfaces2602,2604. In an embodiment, the rails2902may be electrically connected to connectors2608. The connectors2608may be electrically connected to the panel surfaces2602,2604including metamaterials200,300,400,1700,1900, and/or2100. The metamaterials200,300,400,1700,1900, and/or2100may create electron movement when the photovoltaic bristles201,301,401are struck by photons. In an embodiment, the outer conductive layer103of metamaterials200,300,400illustrated inFIGS. 2B, 3B, and 4Bmay be electrically connected to connectors2608. In an embodiment the current conducting traces1701,1702,1703,1901, and/or2101of metamaterials1700,1900,2100as illustrated inFIGS. 17, 19, and 21may be electrically connected the connectors2608to help reduce the electrical resistance in the metamaterial1700,1900,2100. Regardless, electron movement may create electricity to flow from the metamaterials200,300,400,1700,1900, and/or2100within the panel surfaces2602,2604to the connectors2608to the rails2902and buss bars2606connected to the rails2902. From the rails2902and buss bars2606, the electricity may flow to other rails2902and buss bars2606in neighboring panel sections2600and eventually to an electrical destination (e.g. electrical storage) connected to the completed solar panel3100.

FIG. 30illustrates a back view of a solar panel section2600. As discussed earlier, the buss bar2606of the solar panel section2600may have a securing mechanism2901to help stabilize the buss bar2606on the backside of the corrugated section2600. In an embodiment, each buss bar2606may have one or more securing mechanism2901to secure the buss bar2606to the back of the corrugated base2610. Alternatively, each buss bar2606may not have a securing mechanism2901with the corrugated base2610and may be secured and connected only with the rails2902. AlthoughFIGS. 26-30depict a solar panel section2600with two rails2902and two buss bars2606, a solar panel section2600may have any number of rails2902and buss bars2606. Some examples of solar panel sections2600with a different number of rails include solar panel sections with one rail, two rails, three rails, four rails, five rails, etc. Some other examples of solar panel sections with a different number of buss bars include panel sections with one buss bar, two buss bars, three buss bars, four buss bars, five buss bars, etc.

FIG. 31illustrates a perspective view of a solar panel3100with multiple solar panel sections2600. In an embodiment, each solar panel section2600may include metamaterials200,300,400. In another embodiment, the metamaterials may include current conducting traces1701,1702,1703,1901,2101as illustrated in metamaterials1700,1900, or2100ofFIGS. 17, 19, and 21. In an embodiment, each solar panel section2600may be adjacent and combine with one or more other solar panel sections2600. In an embodiment, the solar panel3100may include a frame3102that surrounds the outer perimeter of the combined solar panel sections2600within the solar panel3100.

FIG. 32illustrates an exploded view of a solar panel3100. In an embodiment, the solar panel3100may include a frame3102, a top cover3202, and a back cover3208. In an embodiment, the frame3102is connected with corner brackets3206and fasteners3204to the corners of solar panel sections2600positioned in the corners of solar panel3100. In an embodiment, the frame3102for solar panel3100may include two short pieces3214a,3214band two long pieces3216a,3216bto attach along the four sides of the assembled solar panel sections2600. In an embodiment, the solar panel3100may have four or more corner brackets3206(e.g., eight as shown) to connect the pieces of the frame3102to the assembled solar panel sections2600.

In an embodiment, the top cover3202of the solar panel3100may be transparent or semitransparent. The top cover3202may protect the solar panel section3100and their electrical and photovoltaic components. For example, the top cover3202may protect the solar panel section2600and their electrical and photovoltaic components from oxygen corrosion, wind, water, and dirt or anything else that may reduce the efficiency or life of the metamaterials200,300,400,1700,1900, and/or2100in solar panel3100.

In an embodiment, the back cover3208of solar panel3100may include rounded slots3212so that fasteners3210may connect the back cover3208to the assembled (i.e., combined) solar panel sections2600. The fasteners3210may be any type that may connect the back cover3208to the assembled solar panel sections2600. For example, the fasteners3210may fasten similar to the fasteners2612as described with reference toFIG. 28(e.g., by bolts, screws, etc.).

In an embodiment, the back cover3208and the top cover3202may be sealed within the solar panel3100by the frame3102. In an embodiment, only the back cover3208or the top cover3202may be sealed within the solar panel3100by the frame3102. The back cover3208and the top cover3202may provide structural support to the solar panel3100and its subparts. In addition, the back cover3208and the top cover3202may protect the subparts of the solar panel3100from any contamination that may reduce the efficiency and life of the metamaterials200,300,400,1700,1900, and/or2100in solar panel3100such as wind, water, dirt, or oxygen, etc.

In another embodiment, the volumetric efficiency gains realized from the solar panel with the corrugated sections may be achieved by mounting completed solar panels in corrugated patterns with respect to each other. Thus, completed solar panels may be mounted in an array of solar panels where the surfaces of each solar panel form an angle of approximately 30 to 60 degrees with a common plane such as a base connecting the solar panels that is perpendicular to the sun. As an alternative embodiment, reflectors may replace some completed solar panels in the corrugated pattern to help maximize efficiency gain of each completed solar panel.

Referring toFIG. 37A, a first exemplary in-process photovoltaic structure is illustrated. As used herein, an “in-process” structure or a “prototypical” structure refers to a transient structure that is subsequently modified by addition of another material, removal of an existing material, or a combination thereof to provide a final device structure.

The first exemplary in-process photovoltaic structure may include a final substrate3609das provided by the processing steps ofFIG. 36A. The final substrate3609dmay include a sheet substrate3710and a moldable material layer3720that is an optically transparent layer, i.e., a layer composed of an optically transparent material. As used herein, an “optically transparent material” refers to a material having an absorption coefficient that is less than 100 cm−1between the entire wavelength range from 400 nm to 800 nm. In an embodiment, the optically transparent material of the moldable material layer3720may have an absorption coefficient that is less than 10 cm−1between the entire wavelength range from 400 nm to 800 nm. In another embodiment, the optically transparent material of the moldable material layer3720may have an absorption coefficient that is less than 1 cm−1between the entire wavelength range from 400 nm to 800 nm.

The refractive index of the moldable material layer3720may be in a range between 1 and 3 between the wavelength range from 400 nm to 800 nm. In an embodiment, the refractive index of the moldable material layer3720may be in a range between 1.2 and 2.4 between the wavelength range from 400 nm to 800 nm. In another embodiment, the refractive index of the moldable material layer3720may be in a range between 1.3 and 2.0 between the wavelength range from 400 nm to 800 nm. In an embodiment, the refractive index of the moldable material layer3720may be in a range between 1.4 and 1.7 between the wavelength range from 400 nm to 800 nm.

The moldable material layer3720may be a dielectric material layer. The resistivity of the moldable material layer3720may be greater than 1.0×105Ohm-cm. In an embodiment, the resistivity of the moldable material layer3720may be greater than 1.0×106Ohm-cm. In another embodiment, the resistivity of the moldable material layer3720may be greater than 1.0×107Ohm-cm.

In an embodiment, the sheet substrate3710may be an optically transparent substrate, and may, or may not, be flexible. In an embodiment, the sheet substrate3710may include a rigid material such as glass (including doped or undoped silicate glass) or sapphire. In another embodiment, the sheet substrate3710may include a transparent flexible material such as transparent polymers (e.g., plastics). The sheet substrate3710may be a continuous sheet extending for hundreds of feet and stored in a roll, or may be discrete sheet having lateral dimensions on the order of 1 m and stored, for example, by stacking.

A metamaterial of the present disclosure may be formed by providing a moldable material layer3720on, or in, a sheet substrate3710. In an embodiment, the moldable material layer3720may be formed on the sheet substrate3710by dispensing a moldable material on the sheet substrate3710. The moldable material may be any optically transparent material that may be molded. The thickness of the moldable material layer3720, prior to patterning by imprinting or alternative means, may be in a range from 6 microns to 1 mm, and typically in a range from 10 microns to 60 microns, although lesser and greater thicknesses may also be employed.

In an embodiment, the moldable material layer3720may contain a moldable material selected from a lacquer, a silicone precursor material, a gel derived from a sol containing a polymerizable colloid, and a glass transition material. In an embodiment, the moldable material layer3720may include a polymer resin-based plastic material, an organic material including at least one resin, or a flexible glass material based on silica. The transparent sheet substrate3710may include a plastic film or a glass film that is more rigid than the moldable material layer3720. In one embodiment, the moldable material layer3720may be provided by applying a polymerizable material on a substrate (such as the sheet substrate3710), and inducing partial polymerization of the polymerizable material.

In embodiments in which the moldable material layer3720includes a lacquer, the moldable material may be selected from phenylalkyl catechol-based lacquers, nitrocellulose lacquers, acrylic lacquers, and water-based lacquers. Phenylalkyl catechol-based lacquers include at least one phenylalkyl catechol that includes a long alkyl chain. Examples of such phenylalkyl catechols include urushiol and laccol (also referred to as thitsiol). Urushiol has the formula of C6H3(OH)2R, in which R may be, for example, (CH2)14CH3or (CH2)7CH═CHCH2CH═CHCH2CH═CH, or a similar radical. Laccol is a crystalline phenol having the formula of or (CH2)7CH═CHCH2CH═CH(CH2)2CH3or (CH2)7CH═CH(CH2)5CH3or (CH2)7CH═CHCH2CH═CHCH═CHCH3. Laccol has the formula of C17H31C6H3(OH)2(i.e., C6H3(OH)2R in which R=C17H31) and occurring in the sap of lacquer trees. Phenylalkyl catechol-based lacquers are generally slow-drying, and are set by oxidation and polymerization in addition to evaporation alone. Heat and humidity may be applied to accelerate partial setting of the phenylalkyl catechol-based lacquers prior to imprinting and/or to accelerate full setting of the phenylalkyl catechol-based lacquers after imprinting. The phenols oxidize and polymerize under the action of an enzyme laccase, yielding a substrate that, upon proper evaporation of its water content, is hard.

Nitrocellulose lacquers are fast-drying solvent-based lacquers that contain nitrocellulose, which is a resin obtained from the nitration of a cellulostic material (such as cotton). Nitrocellulose lacquers may be applied by spraying. Nitrocellulose lacquers produce a flexible, hard, and transparent film.

Acrylic lacquers refer to lacquers using acrylic resin (which is a synthetic polymer). Acrylic resin is a transparent thermoplastic that is obtained by the polymerization of derivatives of acrylic acid. Acrylic lacquer has a fast drying time.

Water-based lacquers are less toxic than other types of lacquers, and various types of water-based lacquers are known. An illustrative exemplary composition for water-base lacquer may be acrylic Copolymer Resin 30% in weight percentage, dipropylene glycol monomethyl ether at about 5% in weight percentage, propylene glycol monomethyl ether at about 5% in weight percentage, and water in about 60% weight percentage. Other exemplary compositions for water-based lacquer are disclosed, for example, in European Patent Publication No. EP0555830 A1 and U.S. Pat. No. 5,550,179 A.

In an embodiment, the moldable material layer3720may include a plastic material prepared from semicrystalline or amorphous polymer resins. Examples of semicrystalline resins that may be employed for the moldable material layer3720include, but are not limited to, terephthalate (PET), polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), nylon, polyoxymethylene (POM), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVFD), polyethylenechlorotrifluoroethylene (PECTFE), polyethylene tetrafluoroethylene (PETFE), or similar fluoro-based and non-fluoro-based polymers blended together or copolymerized in one or more mixtures. In an embodiment, the moldable material layer3720may include terephthalate (PET). Examples of amorphous polymer resins include, but are not limited to, polycarbonate (PC), polymethylmethacrylate (PMMA), polymethacrylate (PMA), cyclic polyolefin (branded under the trade name Topas™), or similar polymers blended together or copolymerized in one or more mixtures.

In an embodiment, the moldable material layer3720may include a resin material. In an embodiment, the resin material may be selected such that the resin material may be cured with a radiation with wavelengths between 200 nm and 450 nm (such as 365 nm), or may be cured or set thermally with heat treatment at a temperature in a range from 500° C. to 500° C.

In an embodiment, the resin material of the moldable material layer3720may be selected from radiation cured organic materials that are cured through radical polymerization of methacrylate and methylmethacrylate monomers, preferably methylmethacrylate monomers and methylmethacrylate derivations. Example of methylmethacrylate derivations include by not limited to methylmethylacrylic acid, hydroxyethylmethylmethacrylate, fluorofunctinoalized methylmethacrylate, and silicone-functionalized methylmethacrylate. These may be mixed in various proportions and blended with oligomers based on urethane acrylate precursors and photoinitiators activated by light in the wavelength range listed above.

In another embodiment, the resin material of the moldable material layer3720may be selected from radiation cured organic materials cured through cationic polymerization using a cationic photoinitiators activated by light in the wavelength range above. Monomers are epoxy based with single, double, or multiple functionality. Monomer examples include, but are not limited to, diglycidyl monomers based on bisphenol-A or bisphenol-F, cylic aliphatic monomers and oligomers, and mixtures thereof.

In another embodiment, the resin material of the moldable material layer3720may be selected from thermally cured sol-gel based chemistries that undergo hydrolysis and condensation reactions resulting in highly crosslinked inorganic matrices. Examples include but not limited to tetraethylorthosilicate (TEOS), tetramethylorthosilicate (TMOS), or organically modified silicates with one or more hydrolyzeable components, or mixtures thereof. These resin materials may be further sintered at an elevated temperature between 300° C. and 500° C. to densify the silicate, evaporate low molecular weight byproducts, and pyrolyze the organic materials to form a high temperature resistant ceramic.

In another embodiment, the resin material of the moldable material layer3720may be selected from thermally cured silicates that are crosslinked through hydrosilation addition reactions using platinum catalysts which may be sintered at an elevated temperature between 300° C. and 500° C. to densify silicate and pyrolyze away the organic materials to form a temperature resistant ceramic.

In another embodiment, the resin material of the moldable material layer3720may be selected from organic-inorganic hybrid resins based on radiation cured silicates from monomers of acrylate and methacrylate functionality that may be cured with radical polymerization after activation of photoinitiators irradiated with light in the wavelength range above and undergo further densification by sol-gel condensation of hydroxysiloxane groups in the materials. These materials may then be subsequently sintered at an elevated temperature between 300° C. and 500° C. to form a high temperature resistant ceramic.

In another embodiment, the resin material of the moldable material layer3720may be selected from a solid deformable material, which may be a thermoset or thermoplastic resin, that may be applied through a solvent cast method and may be laminated as a film. Examples of thermoset resins include, but are not limited to, epoxies, polyurethanes, silicones, ethylene propylene diene monomer (EPDM) rubber, and nitrile and natural rubbers. Examples of thermoplastic resins include both semi-crytalline and amorphous resins. Semi-crystalline polymer resins include, but are not limited to, polyethylene terephthalate (PET), polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), nylon, polyoxymethylene (POM), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVFD), polyethylenechlorotrifluoroethylene (PECTFE), polyethylene tetrafluoroethylene (PETFE), and similar fluoro-based and non-fluoro-based polymers blended together or copolymerized in one or more mixtures. For films embossed with an imprinting lacquer, PET may be employed. For films embossed with heat and pressure, PE may be employed. Amorphous polymer resins include, but are not limited to, polycarbonate (PC), polymethylmethacrylate (PMMA), polymethacrylate (PMA), cyclic polyolefin (branded under the trade name Topas™), and similar polymers blended together or copolymerized in one or more mixtures.

In an embodiment, the moldable material layer3720may include a moldable material that may form silicone, i.e., a silicone precursor. Silicones are polymers that include any inert, synthetic compound made up of repeating units of siloxane, which is a functional group of two silicon atoms and one oxygen atom, and may be combined with carbon and/or hydrogen. In an embodiment, the moldable material of the moldable material layer3720, as applied to the sheet substrate3710prior to imprinting, may be selected from polydimethylsiloxane, dimethyldichlorosilane, methyltrichlorosilane, and methyltrimethoxysilane.

In an embodiment, the moldable material layer3720may be formed by applying a precursor material for polydimethylsiloxane (PDMS; CH3[Si(CH3)2O]nSi(CH3)3) and inducing the polymerization of the precursor material. The number n of repetition of the monomer [SiO(CH3)2] units determines the viscosity and elasticity of the polydimethylsiloxane material. The polymerization reaction evolves hydrogen chloride.

Silane precursors with more acid-forming groups and fewer methyl groups, such as methyltrichlorosilane, may be used to introduce branches or cross-links in the polymer chain, thereby producing hard silicone resins. Alternatively, chlorine atoms in the silane precursor for polydimethylsiloxane may be replaced with acetate groups. In this case, the polymerization produces acetic acid, which is less chemically aggressive than HCl. After polymerization and cross-linking, a silicone precursor material produces an optically transparent layer having a hydrophobic surface.

In an embodiment, the moldable material layer3720may contain a sol-gel material. As used herein, a sol-gel material refers to a sol material that may be subsequently transformed to a gel material or a gel material that is derived from a sol material, i.e., a material that may go through a sol-gel transition or has gone through a sol-gel transition. The moldable material layer3720as applied to the sheet substrate3710may be a sol material, which subsequently goes through a sol-gel transition to become a gel material prior to imprinting.

A sol-gel transition or a sol-gel process refers to a process in which a sol (a set of solid nanoparticles and a liquid in a state in which the solid particles are dispersed in the liquid) agglomerate to form a gel (a set of a liquid and a continuous three-dimensional network extending throughout the liquid). A sol is a colloid. A colloid is a mixture in which at least two different phases (such as solid and liquid) are intimately mixed at microscopic level. Solid nanoparticles or macromolecules are dispersed throughout the liquid in a sol. In a gel, the solid network of interconnected nanostructures spans the volume of a liquid medium. In the gel, the continuous phase is a solid network and the dispersed phase is a liquid. A sol may become a gel when the solid nanoparticles dispersed in it may join together to form a network of particles that spans the liquid. As a sol becomes a gel, its viscosity approaches infinity and finally becomes immobile. A sol-gel transition may be triggered with the passage of time, change of pH, addition of a gelation agent, temperature, agitation, and/or catalysts.

In an embodiment, the moldable material of the moldable material layer3720as applied to the sheet substrate3710may be a sol-gel material selected from a colloid containing a metal alkoxide and a colloid containing silicon alkoxide. In this case, hydrosis and condensation may be employed to form a gel from the sol so that the moldable material layer3720as provided for imprinting is in a gel state.

The precursor sol may be either deposited on a substrate to form a film (e.g., by dip coating or spin coating), cast into a suitable container with the desired shape (e.g., to obtain monolithic ceramics, glasses, fibers, membranes, aerogels), or used to synthesize powders (e.g., microspheres, nanospheres).

A typical sol-gel process includes solution, gelation, optional drying, and optional densification operations. In one exemplary embodiment, the moldable material layer3720may include an incompletely dried or incompletely densified silica glass. An alkoxide may be mixed with water and a mutual solvent to form a solution. During gelation, hydrolysis leads to the formation of silanol groups (Si—OH), which are intermediate groups. The moldable material layer3720as provided for imprinting may include silanol groups. Optionally, a partial condensation reaction that produces siloxane bonds (Si—O—Si) may be performed prior to imprinting. A second condensation reaction may be performed after imprinting. Alternatively, the condensation reaction may be performed only after imprinting. The silica gel formed by this process leads to an interconnected three-dimensional network including polymeric chains. Thus, drying and densification may be performed after imprinting of the moldable material layer3720.

If a sol-gel material selected from a colloid containing a metal alkoxide and a colloid containing silicon alkoxide may be applied as the moldable material layer3720on the sheet substrate3710, hydrosis and condensation may be employed to form a gel from the sol so that the moldable material layer3720as provided for imprinting is in a gel state. In an embodiment, a silcon alkoxide such as silicon tetraethoxide (Si(OC2H5)4, i.e., tetraethyl orthosilicate (TEOS)) may be employed as the sol material for the moldable material layer3720. In a subsequent hydrolysis (reaction with water), a hydroxyl ion becomes attached to the silicon atom as follows: Si(OC2H5)4+H2O→HO—Si(OC2H5)3+C2H5—OH

In an embodiment, the amount of water added to silicon tetraethoxide for hydrolysis may be controlled such that hydrolysis proceeds partially, and does not result in 100% conversion of silicon tetraethoxide into silica, but provides a gel including polymer chains of intermediate species a partial hydrolysis reaction such as HO—Si(OC2H5)3and/or (HO)2—Si(OC2H5)2. The moldable material layer3720as provided for imprinting includes such a gel. After imprinting, complete hydrolysis may be performed by providing additional water and optionally employing a hydrolysis catalyst such as acetic acid or hydrochloric acid.

Formation of a metal oxide involves connecting the metal centers with oxo (M-O-M) or hydroxo (M-OH-M) bridges, therefore generating metal-oxo or metal-hydroxo polymers in solution.

In an embodiment, the moldable material layer3720may include a flexible glass material based on silica (SiO2) manufactured and processed with a roll-to-roll manufacturing method. In an embodiment, the moldable material layer3720may include glass film commercially available from the glass manufacturer Corning™ and branded as Willow Glass™.

The web-to-plate system may include a first densification device configured to reduce elasticity of the moldable material prior imprinting, and/or a second densification device configured to reduce elasticity of the moldable material after imprinting. In an embodiment, each of the first and second densification devices may include at least one of a fan, a heater, an ultraviolet treatment system, an agitator, and a laser irradiation system. The first and/or second densification device may optionally include a spray device configured to spray a gelation accelerant or a catalyst that accelerates densification of the moldable material at various stages of densification.

In an embodiment, the pattern in the moldable material layer3720may be made by embossing the moldable material layer3720with a patterned metal plate with heat and pressure in case the moldable material layer3720includes a plastic or glass film, or may be made by embossing an imprinting resin on the plastic or glass film and subsequently curing the imprinting resin while in contact with the patterned metal plate in case the moldable material layer3720includes the resin.

During the imprinting process, a die (such as a daughter die web3501dinFIG. 36A) including a pattern of protruding structures and incorporated into a web may be imprinted onto the moldable material layer3720to generate a pattern of trenches1103extending downward from a top surface of the moldable material layer3720to a depth, which may be the same as the height h of the trench1103. The height h of the trenches1103may be the same as the height h of the bristles discussed above. In an embodiment, the height h of the trench1103may be less than the thickness t of the moldable material layer3720. In an embodiment, the thickness t of the moldable material layer3720may be in a range from 6 microns to 200 microns. In another embodiment, the thickness t of the moldable material layer3720may be in a range from 10 microns to 100 microns. In yet another embodiment, the thickness t of the moldable material layer3720may be in a range from 15 microns to 30 microns.

In an embodiment, each of the trenches1103may have a height h in a range from 3 microns to 100 microns, although lesser and greater depths may also be employed. In an embodiment, each of the trenches1103may have a height h in a range from 6 microns to 30 microns. In another embodiment, each of the trenches1103may have a height h in a range from 9 microns to 15 microns. In another embodiment, each of the trenches1103may have a height h in a range from 10 microns to 12 microns. In another embodiment, the trenches1103may have the same depth.

A base lateral dimension bd may be in a range from 0.4 micron to 20 microns at the top portion of each trench1103, although lesser and greater dimensions may also be employed. As used herein, a base lateral dimension bd refers to the maximum lateral dimension at the topmost portion of a trench1103. The base lateral dimension becomes the base dimension of an inverted trench after the first exemplary structure is subsequently flipped upside down. The horizontal cross-sectional shape of each trench1103may be in a circular shape, an elliptical shape, or a closed curvilinear shape. In an embodiment, the horizontal cross-sectional shape of each trench1103may be a circle, and the base lateral dimension bd may be the diameter of each trench1103at a topmost portion, i.e., the portion that is most distal from the interface between the moldable material layer3720and the transparent sheet substrate3710. In an embodiment, the base lateral dimension bd may be in a range from 1 micron to 10 microns. In another embodiment, the base lateral dimension bd may be in a range from 2 microns to 9 microns. In yet another embodiment, the base lateral dimension bd may be in a range from 4 microns to 8 microns. In another embodiment, the base lateral dimension bd may be in a range from 5 microns to 7 microns.

A tapered-end lateral dimension td may be in a range from 0.22 micron to 12 microns at the top portion of each trench1103, although lesser and greater dimensions may also be employed. As used herein, a tapered-end lateral dimension td refers to the maximum lateral dimension at the bottommost portion of a trench1103. The tapered-end lateral dimension becomes the dimension of the tapered upper portion of an inverted trench after the first exemplary structure is subsequently flipped upside down. In an embodiment, the horizontal cross-sectional shape of each trench1103may be a circle, and the tapered-end lateral dimension td may be the diameter of each trench1103at a bottommost portion, i.e., the portion that is most proximal to the interface between the moldable material layer3720and the transparent sheet substrate3710. In an embodiment, the tapered-end lateral dimension td may be in a range from 0.6 micron to 6 microns. In another embodiment, the tapered-end lateral dimension td may be in a range from 1.2 microns to 4.8 microns. In another embodiment, the base lateral dimension bd may be in a range from 2.4 microns to 3.6 microns. In another embodiment, the base lateral dimension bd may be in a range from 3 microns to 4.2 microns.

The ratio of the base lateral dimension bd to the height h of the trench1103may be in a range from 0.5 to 0.75, although lesser and greater ratios may also be employed. In an embodiment, the ratio of the base lateral dimension bd to the height h of the trench1103may be in a range from 0.55 to 0.7. In another embodiment, the ratio of the base lateral dimension bd to the height h of the trench1103may be in a range from 0.6 to 0.65.

The horizontal cross-sectional shape of each trench1103may be circular, elliptical, polygonal, or of any other closed curvilinear shape. In an embodiment, the horizontal cross-sectional shape of each trench1103may be substantially circular. The sidewall of each trench1103may be substantially vertical, or may be tapered with a taper angle α in a range from 3 degrees to 15 degrees, although greater taper angles may also be employed. As used herein, a surface is substantially vertical if the angle of the surface with respect to a vertical direction does not exceed 3 degrees. In an embodiment, the taper angle α may be in a range from 6 degrees to 10 degrees. In another embodiment, the taper angle α may be in a range from 7 degrees to 9 degrees.

After imprinting, the material of the moldable material layer3720with an imprint pattern thereupon may be densified or otherwise transformed to increase the rigidity. For example, if the moldable material layer3720includes a lacquer, a silicone, or a gel, densification or additional transformation of the moldable material layer3720may be effected by heat, cold, moisture, agitation, application of a catalyst, irradiation by visible light, ultraviolet light, or infrared light, ventilation, or a combination thereof. In one embodiment, if the moldable material layer3720is provided by applying a polymerizable material on a substrate (such as the sheet substrate3710) and subsequently inducing partial polymerization of the polymerizable material, the patterned moldable material layer3720may be cured for further polymerization after patterning and prior to depositing a layer stack, or after depositing the layer stack.

In case the moldable material layer3720after imprinting includes a gel, further polycondensation process may be performed to enhance mechanical properties and structural stability by application of heat to induce sintering, densification and/or grain growth. Optionally, a drying process may be employed to remove any residual liquid (solvent) in the moldable material layer3720.

The moldable material layer3720after densification or rigidification functions an optically transparent template on which material layers for forming a photovoltaic structure may be sequentially deposited.

Referring toFIG. 37B, an outer conductive layer103may be deposited on the contiguous top surface of the moldable material layer3720, which includes a planar top surface and surfaces of the trenches1103. The outer conductive layer103may be the same as described above. In an embodiment, the outer conductive layer103may be a transparent conductive material layer, and may contain, for example, a transparent conductive oxide such as indium tin oxide (ITO), fluorine doped tin oxide (FTO), and doped zinc oxide.

The outer conductive layer103may be deposited, for example, by sputtering (physical vapor deposition), metal organic chemical vapor deposition (MOCVD), metal organic molecular beam deposition (MOMBD), spray pyrolysis, or pulsed laser deposition (PLD). The thickness of the outer conductive layer103, as measured on the sidewalls of the trenches1103, may be in a range from 200 nm to 6 microns, although lesser and greater thicknesses may also be employed. In an embodiment, the thickness of the outer conductive layer103may be in a range from 400 nm to 3 microns. In another embodiment, the thickness of the outer conductive layer103may be in a range from 600 nm to 1.5 microns. In another embodiment, the thickness of the outer conductive layer103may be in a range from 700 nm to 1 micron. A cavity1103′ may be present within each trench1103because the trenches1103are not completely filled by the outer conductive layer103.

Subsequently, the outer conductive layer103may be patterned, for example, by laser ablation. The pattern of the outer conductive layer103may be selected to facilitate electrical wiring of photovoltaic devices to be formed on the transparent sheet substrate3710. For example, the outer conductive layer103may be patterned into a plurality of electrically isolated portions, each of which functions as an electrode of a photovoltaic device that may be connected in a series connection and/or in a parallel connection.

Referring toFIG. 37C, a photovoltaic material layer (104,105) may be formed on the surfaces of the outer conductive layer103. The surfaces of the outer conductive layer103on which the photovoltaic material layer (104,105) may be deposited include a planar top surface of the outer conductive layer103located above the moldable material layer3720, and inner sidewalls of the outer conductive layer103located inside the trenches1103.

The photovoltaic material layer (104,105) may include a second absorber sublayer104and a first absorber sublayer105as described above. The photovoltaic material layer (104,105) may include a p-n junction or a p-i-n junction or a plurality of p-n junctions or p-i-n junctions provided that the photovoltaic material layer (104,105) is a material stack that generates and separates photogenerated electron-hole pairs in opposite directions, i.e., one of the electron and the hole toward the outer conductive layer103and the other of the electron and the hole away from the outer conductive layer103. The thickness of the photovoltaic material layer (104,105) may be in a range from 200 nm to 6 microns, although lesser and greater thicknesses may also be employed. In an embodiment, the thickness of the photovoltaic material layer (104,105) may be in a range from 400 nm to 3 microns. In another embodiment, the thickness of the photovoltaic material layer (104,105) may be in a range from 600 nm to 1.5 microns. In yet another embodiment, the thickness of the photovoltaic material layer (104,105) may be in a range from 700 nm to 1 micron. The photovoltaic material layer (104,105) may be formed by low pressure chemical vapor deposition (LPCVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or a combination thereof.

Subsequently, the photovoltaic material layer (104,105) may be patterned, for example, by laser ablation. The pattern of the photovoltaic material layer (104,105) may be selected to facilitate electrical wiring of photovoltaic devices to be formed on the transparent sheet substrate3710. For example, the photovoltaic material layer (104,105) may be patterned into a plurality of electrically isolated portions. In an embodiment, a portion of the photovoltaic material layer (104,105) may be removed in a boundary region between a photovoltaic region containing the photovoltaic bristles to be formed and a conducting trace region in which a current conducting trace for a portion of the outer conductor layer103is to be formed.

Referring toFIG. 37D, an optional transparent inner conductive layer107amay be deposited by a conformal deposition method such as chemical vapor deposition, or atomic layer deposition. Alternatively, the optional transparent inner conductive layer107amay be deposited by a non-conformal deposition method such as physical vapor deposition. The optional transparent inner conductive layer107amay include a transparent conductive oxide material. In an embodiment, the transparent inner conductive layer107aincludes aluminum doped zinc oxide (Al:ZnO). The thickness of the optional transparent inner conductive layer107a, if present, may be in a range from 50 nm to 200 nm, although lesser and greater thicknesses may also be employed.

A conductive core layer106may be formed by deposition of a conductive material on the transparent inner conductive layer107a(if the transparent inner conductive layer107ais present) or on the photovoltaic material layer (104,105) (if the transparent inner conductive layer107ais omitted). The conductive core layer106may include the same material as the conductive cores106described above. The conductive core layer106may be a contiguous layer of a conductive material, and may be a metallic conductive layer, i.e., a conductive layer composed of a metallic material. In an embodiment, the conductive core layer106may include aluminum, copper, silver, gold, tungsten, nickel, cobalt, and/or any other conductive elemental metal. Further, the conductive core layer106may include an alloy of at least two elemental metals and/or a stack of at least two metallic layers each including an elemental metal or an alloy of at least two elemental metals. In an embodiment, the conductive core layer106may include a stack of a silver layer that contacts the transparent inner conductive layer107aor the photovoltaic material layer (104,105), and an aluminum layer. The thickness of the conductive core layer106, as measured on the sidewalls of the transparent inner conductive layer107aor the photovoltaic material layer (104,105) may be in a range from 300 nm to 6 microns. In an embodiment, the thickness of the conductive core layer106may be in a range from 500 nm to 3 microns. In another embodiment, the thickness of the conductive core layer106may be in a range from 750 nm to 1.5 microns. The conductive core layer106includes a core portion of each photovoltaic bristle formed in a respective trench1103. The core portions of the photovoltaic bristles are electrically shorted together because the conductive core layer106is a contiguous material layer.

The conductive core layer106may include the same material as the cores106described above. The conductive core layer106(and the cores106described above) may include a reflective metallic material, or a transparent material. The thickness of the conductive core layer106may be in a range from 30 nm to 2,000 nm, although lesser and greater thicknesses may also be employed.

In an embodiment, the conductive core layer106may include a metallic material such as an elemental metal (e.g., aluminum, tungsten, copper, silver, gold, platinum, nickel, cobalt, chromium, titanium, tantalum, rhodium, iridium, zinc, and vanadium), an intermetallic alloy of at least two elemental metals (e.g., the elemental metals listed above), a conductive metallic nitride (e.g., TiN, TaN, WN), a metal-semiconductor alloy (e.g., a metal silicide, and a metal germanosilicide), and/or a combination or a stack thereof. In an embodiment, the conductive core layer106may include an optional diffusion barrier metallic liner such as a conductive metallic nitride and a high conductivity material such as an elemental metal. In an embodiment, the high conductivity material may be aluminum or copper.

In an embodiment, the conductive core layer106may employ a transparent conductive material that allows transmission of ambient light from the backside of a photovoltaic device to the photovoltaic material layer (104,105). The backside of the photovoltaic device corresponds to the upside of the exemplary in-process photovoltaic structure ofFIG. 37D. While the backside efficiency of the photovoltaic structure may be lower than the efficiency of the proper side (front side) of the photovoltaic structure due to higher intensity of radiation available from the front side, an additional gain in efficiency may be realized through the use of a transparent conductive material. Exemplary transparent conductive materials that may be employed for the conductive core layer106include, but are not limited to, boron doped zinc oxide and aluminum doped zinc oxide. In this case, the thickness of the transparent conductive core layer106may be in a range from 200 nm to 1,200 nm to provide a highly conductive path to the tip of each photovoltaic brush while allowing light to pass through the transparent conductive core layer106.

The conductive core layer106may be formed by sputtering (physical vapor deposition), chemical vapor deposition, or atomic layer deposition. The thickness of the conductive core layer106may be selected such that the trenches1103are completely filled, or may be selected such that a via cavity3769is present within, or over, each trench1103. As used herein, a via cavity3769refers to an unfilled volume (i.e., a volume that is not occupied by any liquid or solid) that extends most along a vertical direction. In other words, the maximum dimension of a via cavity may occur along the vertical direction. In an embodiment, the maximum vertical dimension of each via cavity3769may be greater than the maximum lateral dimension of the via cavity3769. The via cavity3769may be formed through many mechanisms.

In an embodiment, the via cavities3769may be formed when the amount of the deposited material for the conductive core layer106is insufficient to fill the trenches1103. In this case, the cavities1103′ within the trenches1103do not disappear even after the conductive core layer106is formed, and each remaining cavity1103′ constitutes a via cavity3769. Such via cavities may also be present in the exemplary structures ofFIGS. 13I-13L and 15G-15J. The top surface of the conductive core layer106includes a planar surface located within a horizontal plane (i.e., a Euclidean plane that is parallel to the top surface of the sheet substrate3710) and inner sidewalls of the conductive core layer106that extend into the trenches1103and define the lateral boundaries of the via cavities3769.

Subsequently, the conductive core layer106and the optional transparent inner conductive layer107amay be patterned, for example, by laser ablation. The pattern of remaining stacks of the conductive core layer106and the optional transparent inner conductive layer107amay be selected to facilitate electrical wiring of photovoltaic devices to be formed on the transparent sheet substrate3710. For example, the conductive core layer106and the optional transparent inner conductive layer107amay be patterned into a plurality of electrically isolated portions. In an embodiment, a portion of the conductive core layer106and the optional transparent inner conductive layer107amay be removed in a boundary region between a photovoltaic region containing photovoltaic bristles and a conducting trace region in which a current conducting trace1703for the outer conductor layer103is formed.

Referring toFIG. 37E, a passivation substrate3770may be disposed on the conductive core layer106. In an embodiment, the bottom surface of the passivation substrate3770may contact the horizontal portion of the top surface of the conductive core layer106. As used herein, a passivation substrate refers to a substrate that passivates a structure that it contacts, e.g., by protecting the structure from exposure to air or ambient conditions. In an embodiment, the passivation substrate3770may include glass, sapphire, plastics, or other inert materials that do not interact with the material of the conductive core layer106. In an embodiment, the passivation substrate3770may have a thickness in a range from 100 microns to 1 cm, although lesser and greater thicknesses may also be employed. In an embodiment, the plurality of via cavities3769may be filled with a gas, or may be in vacuum upon disposition of the passivation substrate3770.

The outer conductive layer103, the photovoltaic layer (104,105), the optional transparent inner conductive layer107a, and the conductive core layer106collectively constitutes a photovoltaic layer stack3700. The first exemplary photovoltaic structure may be flipped upside down such that a source of radiation (e.g., the sun) may be located within the upper hemisphere, which is defined as the space located above the horizontal interface between the passivation substrate3770and the photovoltaic layer stack3700after flipping of the first exemplary photovoltaic structure.

Referring toFIG. 37F, a magnified vertical cross-sectional view of a portion of the first exemplary photovoltaic structure ofFIG. 37Eafter flipping upside down is shown. A via cavity3769may be laterally bounded by a non-planar bottom surface of the conductive core layer106, and may be vertically bounded by a top surface of the passivation substrate3770, which is located within the same horizontal plane as the interface between the conductive core layer106and the passivation substrate3770.

Referring toFIG. 37G, a magnified vertical cross-sectional view of a portion of another embodiment of the first exemplary photovoltaic structure is shown. The bottommost portion of each trench1103as formed at the processing step ofFIG. 37A, i.e., the topmost portion of each bristle as formed at the processing steps ofFIG. 37E, may have a rounded tip. In this case, each bristle may include a frustum portion3780and a hemi-spheroid portion3790. The hemi-spheroid portion3790may have a shape that is approximately a hemi-spheroid, i.e., about one half of a spheroid. The ratio of the frustum height h1to the height h of the bristle (3789,3790) may be in a range from 0.7 to 0.95, although lesser and greater ratios may also be employed. In an embodiment, the ratio of the frustum height h1to the height h of the bristle (3789,3790) may be in a range from 0.76 to 0.90. In another embodiment, the ratio of the frustum height h1to the height h of the bristle (3789,3790) may be in a range from 0.80 to 0.87.

Referring toFIG. 37H, a perspective view of the first exemplary photovoltaic structure ofFIG. 37Eis illustrated, in which the transparent sheet substrate3710, the moldable material layer3720(which is an optically transparent layer), and the passivation substrate3770are illustrated with dotted lines to clearly illustrate the shapes of the photovoltaic bristles embedded within the photovoltaic layer stack3700. While cylindrical shapes are illustrated for the photovoltaic bristles, frustum shapes may also be employed for the photovoltaic bristles.

As discussed above, the bristles may be arranged in a two-dimensional hexagonal array. A center-to-center dimension ccd may be in a range from 0.5 micron to 25 microns. The center-to-center dimension ccd refers to the lateral distance between the a vertical axis passing through a geometrical center of a bristle (i.e., the geometrical center of the volume of the bristle) and a vertical axis passing through a geometrical center of a nearest neighbor bristle. If the bristles have a cylindrical symmetry, the center-to-center dimension ccd may be the lateral distance between a vertical symmetry axis of a bristle and a vertical symmetry axis of a nearest neighbor bristle. In an embodiment, the ratio between the base lateral dimension bd to the center-to-center dimension ccd may be in a range from 0.75 to 0.99. In another embodiment, the ratio between the base lateral dimension bd to the center-to-center dimension ccd may be in a range from 0.85 to 0.97. In yet another embodiment, the ratio between the base lateral dimension bd to the center-to-center dimension ccd may be in a range from 0.92 to 0.96. In an embodiment, the center-to-center dimension ccd may be in a range from 1.1 micron to 12 microns. In another embodiment, the center-to-center dimension ccd may be in a range from 2.2 microns to 10 microns. In yet another embodiment, the center-to-center dimension ccd may be in a range from 4.4 microns to 8.8 microns. In still another embodiment, the center-to-center dimension ccd may be in a range from 5.5 microns to 7.7 microns.

Referring toFIG. 37I, an alternative embodiment of the first exemplary photovoltaic structure ofFIG. 37Eis illustrated. One mechanism that forms the via cavity3769is when the deposition method that deposits the conductive core layer106is not sufficiently conformal, thereby depositing more material on the horizontal surfaces of the photovoltaic material layer (104,105) at the processing step ofFIG. 37Dthan on the non-horizontal sidewalls of the photovoltaic material layer (104,105) within the trenches1103. In this case, each via cavity3769may be defined by a contiguous surface of the conductive core layer106that does not touch (i.e., is spatially spaced from) the interface between the conductive core layer106and the photovoltaic material layer (104,105) and does not touch the interface between the conductive core layer106and the passivation substrate3720.

Referring toFIG. 37J, an alternate embodiment of the first exemplary photovoltaic structure ofFIG. 37Eis illustrated. The process that forms the conductive core layer106may be a conformal deposition process and the thickness of the deposited material may be sufficient to completely fill each trench1103. In this case, a dimple may be formed directly over each trench1103by the top surface of the conductive core layer106at the processing step ofFIG. 37D. In this case, each via cavity3769may be defined by a non-planar portion of the top surface of the conductive core layer106at the processing step ofFIG. 37D(or the bottom surface of the conductive core layer106as shown inFIG. 37J) and a portion of the horizontal surface of the passivation substrate3770that contacts the conductive core layer106. A seam3779may be present through the center of each trench1103. In an embodiment, each seam3779of the core conductive material layer106may extend vertically from an apex of each of the plurality of via cavities3769.

Referring toFIG. 37K, a magnified vertical cross-sectional view of another embodiment of the first exemplary photovoltaic structure is illustrated. In this embodiment, a via cavity3769may not be formed within a photovoltaic bristle, and a seam3779extending along a one-dimensional line (in case the photovoltaic bristle has a cylindrical symmetry) or along a vertical plane (in case the photovoltaic bristle has a non-circular elliptical horizontal cross-sectional shape) may be present within each photovoltaic bristle.

Referring toFIG. 37L, a magnified vertical cross-sectional view of further another embodiment of the first exemplary photovoltaic structure is illustrated. In this embodiment, the conductive core layer106may include a transparent conductive material such as a transparent conductive oxide (TCO). In an embodiment, an optional inner transparent conductive layer107amay also be deposited in the structure before the conductive core layer106, such as by sputtering or chemical vapor deposition. The transparent conductive material of the conductive core layer106may be deposited, for example, by sputtering or chemical vapor deposition. A via cavity3769that is entirely laterally surrounded by a surface of the conductive core layer106, including the transparent conductive material may be present within each photovoltaic bristle. In this case, backside illumination, which refers to radiation entering through the passivation substrate3770, may contribute to additional photogeneration of electricity from each photovoltaic bristle. The passivation substrate3770may include a transparent material such as glass or sapphire.

Referring toFIG. 37M, a magnified vertical cross-sectional view of another embodiment of the first exemplary photovoltaic structure is illustrated. The optional inner transparent conductive layer107ain the structure illustrated inFIG. 36Lmay be omitted to form the structure illustrated inFIG. 37M.

Referring toFIG. 37N, a magnified vertical cross-sectional view of another embodiment of the first exemplary photovoltaic structure is illustrated. If the conformity of the deposition process employed to deposit the conductive core layer106is high enough, a seam3779may be formed within each photovoltaic bristle, and a via cavity3769may be formed below the horizontal plane including the bottommost surface of the photovoltaic material layer (104,105).

Referring toFIG. 38A, a second exemplary in-process photovoltaic structure is illustrated, which may include a moldable material layer3820that is provided as a substrate and includes an imprint pattern. The imprint pattern may be the same as the imprint pattern of the first exemplary in-process photovoltaic structure ofFIG. 37A. The moldable material of the moldable material layer3820may be an optically transparent material that is transparent within a visible wavelength range. The moldable material layer3820may be provided in a form having a sufficient mechanical strength to be handled manually or with mechanical devices. The moldable material layer3820may be a moldable substrate including a moldable material and having a thickness t in a range from 5 microns to 5 mm, although lesser and greater thicknesses may also be employed. As such, the moldable material layer3820may be the final substrate3609das provided by the processing steps ofFIG. 36A. Alternatively, the moldable material layer3820may be provided on a substrate of another material.

In an embodiment, the moldable material layer3820may include a moldable substrate that includes a glass transition material. As used herein, a “glass transition material” is a material that displays the behavior of glass transition. A “glass transition” refers to a transition from a liquid to a solid-like state that occurs during cooling or compression in which viscosity increases by at least one order of magnitude. Thermal expansion coefficient, heat capacity, shear modulus, and many other properties of inorganic glasses show a relatively sudden change at the glass transition temperature. Any such step or kink may be used to define the glass transition temperature. Glass transition materials include, among others, plastics, resins, and glass materials based on silica.

In an embodiment, the glass transition material of the moldable material layer3820may be a plastic material prepared from semicrystalline or amorphous polymer resins such as polyethylene terephthalate (PET), polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), nylon, polyoxymethylene (POM), polybutylene terephthalate (PBT), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVFD), polyethylenechlorotrifluoroethylene (PECTFE), polyethylene tetrafluoroethylene (PETFE), similar fluoro-based and non-fluoro-based polymers blended together or copolymerized in one or more mixtures, polycarbonate (PC), polymethylmethacrylate (PMMA), polymethacrylate (PMA), cyclic polyolefin (branded under the trade name Topas™), and similar polymers blended together or copolymerized in one or more mixtures.

In an embodiment, the glass transition material of the moldable material layer3820may be any of the resin material that may be employed for the moldable material layer3720as described above.

In an embodiment, the glass transition material of the moldable material layer3820may be a glass-based on silica (SiO2) blended with other non-silicate glasses or elements. Examples of silica-based glasses include, but are not limited, to soda-lime glass, borosilicate glass, and borophosphatesilicate glass or similar materials. In an embodiment, the glass transition material may be soda-lime glass.

A web-to-plate system3500ofFIG. 35Amay be adapted to process an unpatterned moldable material layer3820to provide an imprinted pattern. Referring toFIG. 39, a web-to-plate system3900is illustrated, which is a modification of the web-to-plate system3500ofFIG. 35Ato provide additional processing capabilities if the moldable material layer3820is provided as a moldable substrate including a glass transition material, or as a moldable material layer of a glass transition material provided on another substrate.

If the moldable material layer3820is provided as a moldable substrate or on another substrate, a moldable material applicator3612illustrated inFIG. 35Ais not necessary. Instead of a moldable material applicator3612, a pre-treatment device3980that may provide a suitable level of viscosity to the moldable material layer3820may be provided in the path of transit for a pre-imprint substrate3820a(which is a moldable material layer3820or a combination of a moldable material layer3820and a substrate) prior to imprinting. In an embodiment, the pre-treatment device3980may be a temperature control device such as a heater or a refrigerator. Depending on the viscosity of the moldable material layer3820in the pre-imprint substrate3820a, the pre-treatment device3980may harden (increase the viscosity of) or soften (decrease the viscosity of) the moldable material of the moldable material layer380.

In an embodiment, the pre-treatment device3980may be a heater configured to heat the top side of the pre-imprint substrate3820a(which may be a moldable substrate) during transportation to the imprint location. The amount of the heat transferred from the pre-treatment device3980to the pre-implant substrate3820amay be controlled such that the top surface of the pre-implant substrate3820has a suitable level of viscosity. The temperature of the top surface of the pre-implant substrate3820at the time of imprinting may be at, above, or below the glass transition temperature of the glass transition material of the moldable material layer3820as provided within the pre-implant substrate3820a.

In an embodiment, the temperature of the linear drive mechanism3610(such as rollers) may be controlled to provide a lower temperature to the backside of the pre-imprint substrate3810ato prevent a lower level of viscosity than the front side of the pre-imprint substrate3820, and thus, prevent sticking of the pre-imprint substrate3820ato the linear drive mechanism3610. The backside of the pre-imprint substrate3820amay be cooled during transportation to the imprint location (the location of the transfer gap roller3607). In an illustrative example, the cooling of the linear drive mechanism3610may be effected by air cooling effected, for example, by a first fan3971, or may be effected by a refrigeration system or a cooling system that cools the linear drive mechanism3610in any other manner.

The imprinted substrate3820cmay be temperature cooled to prevent loss of the imprinted pattern due to excessive viscous flow of the moldable material layer3820within the imprinted substrate3820c. For example, a second fan3972may be employed to circulate air over the imprinted substrate3820cand to provide cooling of the imprinted substrate3820cin case cooling of the imprinted substrate3820cis desired to reduce the viscosity. In an embodiment, a refrigerated air may be circulated by the second fan3972. In this case, the imprinted substrate3820cmay be placed in a mini-environment to reduce the cost of cooling a large space.

In case the top surface of the pre-imprint substrate3810ais heated prior to imprinting, the die as incorporated into the web (such as a daughter die web3501d) may be cooled after imprinting, i.e., after transfer of the pattern of the die into the moldable material layer3820, to minimize damage to the web. Optionally, a third fan3973may be employed to cool the web before the web is wound into a roll.

The imprinted substrate3820cmay be further subjected to an optional densification or rigidification process. For example, a densification device3990may be employed to increase the viscosity of the moldable material layer3820in the imprinted substrate3820cto provide a final substrate3820d, which may be employed to perform the processing step ofFIG. 38Bthereupon. The densification device3990may use any suitable mechanism that increases the viscosity and/or rigidity of the moldable material layer3820, for example, by providing heat, cold, moisture, agitation, application of a catalyst, irradiation by visible light, ultraviolet light, or infrared light, ventilation, or a combination thereof.

Referring toFIG. 38B, an outer conductive layer103may be formed on the moldable material layer3820(as provided within a finished substrate3820d) by performing the processing steps ofFIG. 37B.

Referring toFIG. 38C, a photovoltaic material layer (104,105) may be formed on the upper surface of the outer conductive layer103by performing the processing steps ofFIG. 37C.

Referring toFIG. 38D, an optional transparent inner conductive layer107aand a conductive core layer106may be on the upper surface of the photovoltaic material layer (104,105) by performing the processing steps ofFIG. 37D. Via cavities3769and/or seams3779may be formed in the same manner as illustrated inFIGS. 37F, 37G,37I, and37J. The plurality of via cavities3769may be filled with a gas, or may be in vacuum depending on the ambient conditions at the time of disposing the passivation substrate3770.

Referring toFIG. 38E, a passivation substrate3770may be disposed on the conductive core layer106to seal the conductive core layer106in the same manner as in the case of the first exemplary photovoltaic structure illustrated inFIG. 37E. A second exemplary photovoltaic structure is formed, which is illustrated in a perspective view inFIG. 38F.

Each of the photovoltaic structures illustrated inFIGS. 37E-37J, 38E, and 38Fincludes a layer stack3700located over a substrate3770and includes a core conductive material layer106, a photovoltaic material layer (105,104), and a transparent conductive material layer103. A plurality of via cavities3769may be located underneath vertically protruding portions of the layer stack3700(which form photovoltaic bristles) and above the substrate3770and may be free of any solid phase material therein.

The passivation substrate3770having a planar bottom surface may be disposed directly on a physically exposed planar surface of the core conductive material layer106. A plurality of via cavities3769may be laterally surrounded by the core conductive material layer106, and may be vertically bounded by the passivation substrate3770. In an embodiment, each of the plurality of via cavities3769may be a three-dimensional closed shape defined by a portion of a planar surface of the substrate3770and a non-planar portion of a contiguous surface of the core conductive material layer106.

The contiguous surface of the core conductive material layer106may be the bottom surface of the core conductive material layer106in the upright position (as illustrated inFIGS. 37F-37J and 38F), and is a top surface of the core conductive material layer106prior to flipping the photovoltaic structures (as illustrated inFIGS. 37D, 37E, 38D, and 38E). The contiguous surface of the core conductive material layer106may be located within the same horizontal plane as the top surface of the substrate3770when the photovoltaic structure is in the upright position.

The three-dimensional closed shape may have a variable horizontal cross-sectional area that decreases strictly with a vertical distance from a top surface of the substrate3770as illustrated inFIG. 37F, 37G, andFIG. 37J. Alternatively, the three-dimensional closed shape may have a variable horizontal cross-sectional area that has a maximum at a certain vertical distance from a top surface of the substrate3770as illustrated inFIG. 37I. In an embodiment, the three-dimensional closed shape of a via cavity3769may be a conical shape. In an embodiment, a seam of the core conductive material layer106may extend upward vertically from a topmost apex of each of the plurality of via cavities3769as illustrated inFIG. 37J.

The moldable material layer (3720,3820) may be located on the layer stack3700, and may overlie the layer stack3700in the upright orientation. The moldable material layer (3720,3820) may be an optically transparent layer, and the entirety of the top surface of the moldable material layer (3720,3820) may be planar in the upright orientation. The moldable material layer (3720,3820) may include an optically transparent material selected from a material selected from a lacquer, a silicone precursor material, a gel derived from a sol, and a glass transition material. In an embodiment, the optically transparent material may be selected from phenylalkyl catechol-based lacquers, nitrocellulose lacquers, acrylic lacquers, and water-based lacquers. In another embodiment, the optically transparent material may include silicone. In another embodiment, the optically transparent material may be selected from a gel of silicon oxide and a gel of dielectric metal oxide.

Each of the exemplary structures ofFIGS. 37D-37N and 38D-38Fillustrate a portion of a metamaterial including an array of photovoltaic bristles having approximately cylindrical shapes. As used herein, an “approximately cylindrical shape” refers to a shape that is topologically homeomorphic to a cylinder of a circular or polygonal horizontal cross-sectional shape and having sidewalls that are vertical or having a taper angle less than 10 degrees. The top portion of an “approximately cylindrical shape” may be pointed, or may be rounded.

The metamaterial may be formed by forming an array of vias1103extending into a substrate, which may be a combination of a sheet substrate3710and a moldable material layer3720as illustrated inFIG. 37A, or may be a moldable material layer3820as illustrated inFIG. 38A. Each via1103within the array has an approximately cylindrical shape and is laterally separated from one another, and is laterally surrounded, by the substrate ((3710,3720);3820). In one embodiment, the moldable material layer (3720,3820) may be patterned by imprinting a die including a pattern of protruding structures and incorporated into a web onto the moldable material layer (3720,3820). The patterned moldable material layer (3720,3820) includes a pattern of via cavities. The patterned moldable material layer (3720,3820) is subsequently cured to form a rigid structure.

A transparent conductive layer103(i.e., an outer conductive layer103) is formed over the array of vias1103. An absorber layer (104,105) is formed over the outer conductive layer103. A core conductive material layer106(i.e., the conductive core layer106or the core106) is formed over the absorber layer (104,105). Each via1103is partially filled with the core conductive material layer106to form a conductive core of a respective photovoltaic bristle. A base layer3770(which may be a passivation substrate3770) is formed over the deposited conductive material. A non-solid core3769(i.e., a via cavity3769) that does not include the conductive material or a material of the base layer3770is formed within each photovoltaic bristle and between the core conductive material layer106and the base layer3770.

In one embodiment, the substrate ((3710,3720);3820) comprises a moldable material. Formation of the array of vias1103may be is effected by moving the moldable material under a rolling press or under a rolling die that transfers a pattern thereupon on the moldable material. The conductive cores106of photovoltaic bristles and the core conductive material layer106may be formed as a single contiguous structure in a same deposition process. The transparent conductive layer103may comprise transparent conductive oxide or transparent conductive nitride. In one embodiment, the passivation substrate3770may comprise a non-conductive transparent layer disposed over the array of vias1103. In one embodiment, the substrate ((3710,3720);3820) comprises a polymer. For example, the substrate ((3710,3720);3820) may include a moldable material layer (3720,3820) comprising a polymer.

Referring toFIG. 40, a system4100for manufacturing a photovoltaic structure may include a web-to-plate system (3600,3900) such as the system illustrated in FIG.36A, and a deposition system4000including a plurality of process chambers (4010,4020,4030,4040,4050,4060). The web-to-plate system (3600,3900) may be configured to imprint a die (e.g., a daughter die web3501dinFIG. 36A) including a pattern of protruding structures onto a moldable material layer3720(which is the coating layer in a coated substrate3509binFIG. 36A) to generate a pattern of trenches1103extending downward from a top surface of the moldable material layer3720. The die may be incorporated into a web as in the case of the daughter die web3501d. A roll-to-web system3500, as illustrated inFIG. 35A, may be employed to provide a web with an imprint pattern to the web-to-plate system (3600,3900).

In an embodiment, the web-to-plate system (3600,3900) may include a moldable material dispensation subsystem including a moldable material container (such as the container containing the moldable material3613illustrated inFIG. 36A) and a moldable material dispenser (such as the second moldable material applicator3612illustrated inFIG. 36A). The moldable material dispenser may be configured to coat the moldable material layer3720on a sheet substrate3710prior to transportation of the sheet substrate3710to an imprint location. The moldable material may be selected from a lacquer, a silicone precursor material, a gel derived from a sol, and a glass transition material as described above. In case a sol-gel material is employed for the moldable material layer (3720,3820), a sol may be applied onto the sheet substrate3710, and transition of the sol into a gel may be induced to form the moldable material layer3720. In an embodiment, the moldable material layer3720may be selected from a gel of silicon oxide and a gel of dielectric metal oxide. The moldable material layer3720may include an optically transparent material that is transparent within the visible wavelength range.

Optionally, the web-to-plate system (3600,3900) may further include a densification device configured to reduce elasticity of the moldable material prior to, or after, imprinting. For example, a curing mechanism3615illustrated inFIG. 36Aand/or a densification device3990and/or a second fan3972illustrated inFIG. 39may be employed. In an embodiment, the densification device may include at least one of a fan, a heater, an ultraviolet treatment system, an agitator, and a laser irradiation system.

In an embodiment, the moldable material layer3820may be a moldable substrate including a glass transition material, and the web-to-plate system3900may include a moldable substrate transportation subsystem (such as the linear drive mechanism3610) configured to transport the moldable substrate to an imprint location. The moldable material layer3820may include an optically transparent material that is transparent within the visible wavelength range.

In an embodiment, the web-to-plate system3900may include a heating system3980configured to heat a top side of the moldable substrate during transportation to the imprint location. In an embodiment, the web-to-plate system3900may include a substrate backside cooling system (such as the first fan3971or a built-in cooling system within the linear drive mechanism3600) configured to cool a backside of each moldable substrate during transportation to the imprint location. In an embodiment, a web cooling system (such as the third fan3973inFIG. 39) may be provided, which may be configured to cool the die after transfer of the pattern of the die into the moldable material layer3820.

A die including a pattern of protruding structures and incorporated into a web may be imprinted onto the moldable material layer (3720,3820). The patterned moldable material layer (3720,3820) may be an optically transparent layer including the pattern of trenches1103.

After the web-to-plate system (3600,3900) forms a pattern of trenches1103extending downward from a top surface of a moldable material layer (3720,3820) (which may be an optically transparent layer), a transparent conductive material layer103, a photovoltaic material layer (104,105), and a core conductive material layer106may be sequentially deposited within the pattern of trenches1103in the moldable material layer (3720,3820) as described above. A via cavity3769may be formed within, or above, each trench1103. In an embodiment, the core conductive material layer106may incompletely fill the trenches1103.

The system4100for manufacturing the photovoltaic structure may further include a deposition system4000configured to sequentially deposit a transparent conductive material layer103, a photovoltaic material layer (104,105), and a core conductive material layer106within the pattern of trenches1103in the moldable material layer (3720,3820).

The plurality of process chambers (4010-4080) in the deposition system4000may be integrated into an automated deposition system in which the in-process photovoltaic structure is processed step by step employing an integrated robotic transport system or a manual transport system. The plurality of process chambers (4010-4080) may include, for example, a transparent conductive layer deposition module4010that deposits a transparent conductive layer103, a first laser scribing module4020that patterns the transparent conductive layer103, a first photovoltaic material deposition module4030that deposits a first absorber sublayer104of a first conductivity type, a second photovoltaic material deposition module4040that deposits a second absorber sublayer105of a second conductivity type (which is the opposite of the first conductivity type), a second laser scribing module4050that patterns the first and second absorber sublayers (104,105) (i.e., the photovoltaic material layer (104,105)), an optional transparent inner conductive layer deposition module4060that deposits a transparent inner conductive layer107a, a conductive core layer deposition module4070that deposits a conductive core layer106, and a third laser scribing module4080that patterns the conductive core layer106and the optional transparent inner conductive layer107a. Optionally, assembly of a passivation substrate3770may be automated employing another process module that processes the output substrate from the second conductive trace module4060.

Referring toFIG. 41A, a third exemplary structure according to an embodiment of the present disclosure may be derived from the first exemplary structure illustrated inFIG. 37D. As discussed above, a top surface of a moldable material layer3720may be patterned with an array pattern. The array pattern includes an array of vertically extending shapes that protrude downward from that top surface of the moldable material layer3720, i.e., an array of via1103that includes via cavities therein. A layer stack (103,104,105,107a,106) may be formed over the array pattern. The layer stack comprising a transparent conductive material layer103, a photovoltaic material layer (104,105), an optional transparent inner conductive layer107a, and a core conductive material layer106. Specifically, the transparent conductive material layer103is deposited on surfaces of the via cavities1103and the top surface of the moldable material layer (3720,3820), the photovoltaic material layer (104,105) is deposited on the transparent conductive material layer103, and the core conductive material layer103is deposited on the photovoltaic material layer (104,105). The conductive cores106of photovoltaic bristles and the core conductive material layer106may be formed as a single contiguous structure in a same deposition process. The transparent conductive layer103may comprise transparent conductive oxide or transparent conductive nitride.

A dielectric material layer4120is deposited in each of the cavities that overlying recessed portions (i.e., portions that protrude downward) of the core conductive material layer106. The dielectric material layer4120comprises a dielectric material, i.e., an electrical insulator), and may be deposited by a conformal deposited method (such as chemical vapor deposition), a self-planarizing deposition method (such as spin-coating, spraying, immersion in a bath including the dielectric material, etc. In one embodiment, each via cavity1103may be entirely filled with a respective photovoltaic bristle, which includes vertically extending portions of the transparent conductive material layer103, the photovoltaic material layer (104,105), the core conductive material layer106, and the dielectric material layer4120. Each vertically extending portion of the dielectric material layer4120constitutes a dielectric core4122. Thus, each dielectric core4122may be a portion of the dielectric material layer4120that protrudes into a respective via cavity.

In one embodiment, the thickness of the deposited dielectric material of the dielectric material layer4120may be selected such that all unfilled volumes of the via cavities1103are filled with the dielectric material of the dielectric material layer4120. For example, the thickness of the dielectric material layer4120as measured over a topmost surface of the core conductive material layer107may be in a range from 200 nm to 10 microns, although lesser and greater thicknesses may also be employed. In one embodiment, the dielectric material layer4120comprises a self-planarizing polymer material. In one embodiment, the dielectric material layer4120comprises a transparent material. The top surface of the dielectric material4120(which is a bottom surface of the dielectric material layer4120upon flipping the third exemplary photovoltaic structure) may be a planar surface, i.e., a surface that is within a flat plane.

A two-dimensional array of photovoltaic bristles (103,104,105,107a,106,4122) is formed. Each photovoltaic bristle bristles (103,104,105,107a,106,4122) comprises a vertically protruding portion of the layer stack (103,104,105,107a,106) and embedding a dielectric core4122comprising a dielectric material. The dielectric core4122contacts a sidewall of the core conductive material layer106. The transparent conductive material layer103is spaced from the core conductive material layer106by the photovoltaic material layer (104,105).

Referring toFIG. 41B, a substrate, which is herein referred to as a passivation substrate3770) is having a planar bottom surface may be disposed on the top surface of the dielectric material layer4120. The passivation substrate3770may be the same as in the first and second exemplary photovoltaic structures. The passivation substrate3770may, or may not, be optically transparent. The passivation substrate3770may include a material such as glass, sapphire, a polymer material, or a plastic material.

FIG. 41Cis an exploded view of the third exemplary photovoltaic structure after formation of the passivation substrate3770. The combination of the sheet substrate3710and the moldable material layer3720may be replaced with a moldable material layer3820that functions as a substrate that provides mechanical support to provide a fourth exemplary photovoltaic structure.FIG. 41Dprovides a see-through perspective view of the third or fourth exemplary photovoltaic structure.

FIGS. 41E-41Iare magnified views of various embodiments of a photovoltaic bristle of the third exemplary photovoltaic structure. The various dimensions such as a taper angle α, a base lateral dimension bd, a tapered-end lateral dimension td, the frustum height h1, and the height h of the bristle3700may be the same as in the various embodiments of the first exemplary photovoltaic structure.FIG. 41Eillustrates a photovoltaic bristle including a hemi-spheroid region.FIG. 41Fillustrates a photovoltaic bristle including a substantially planar top surface.FIG. 41Fillustrates a photovoltaic bristle including a transparent conductive material as the material of the core conductive material layer106.FIG. 41Hillustrates a photovoltaic bristle including a seam3779therein.FIG. 41Iillustrates a photovoltaic bristle including a via cavity3769.

Referring toFIG. 42A, a fourth exemplary photovoltaic structure may be derived from the second exemplary photovoltaic structure ofFIG. 38Dby depositing a dielectric material layer4120employing the same processing steps of the processing steps ofFIG. 41A. Thus, the combination of the sheet substrate3710and the moldable material layer3720is replaced with the moldable material layer3820that provides mechanical support to the photovoltaic bristles.

Each of the third and fourth exemplary photovoltaic structures may be flipped upside down prior to installation and/or use. In this configuration, each of the third and fourth exemplary photovoltaic structures comprises a dielectric material layer4120comprising a planar portion having a uniform thickness and an array of protruding portions4122extending from a planar surface of the planar portion; and a layer stack (103,104,105,107a,106) located on the dielectric material layer4120and comprising a core conductive material layer106, a photovoltaic material layer (104,105), and a transparent conductive material layer103. The core conductive material layer106is in contact with the planar surface and the protruding portions4122of the dielectric material layer4120. The transparent conductive material layer103is spaced from the core conductive material layer106by the photovoltaic material layer (104,105). Each combination of a protruding portion4122of the dielectric material layer4120and portions of the layer stack (103,104,105,107a,106) surrounding the protruding portion4122constitutes a photovoltaic bristle (103,104,105,107a,106,4122).

In one embodiment, the entirety of the dielectric material layer4120may be a single material layer without any interface or seam therein. In one embodiment, the entirety of the dielectric material layer4120may have a homogeneous material composition throughout. In one embodiment, the dielectric material layer4120comprises an optically transparent material. In one embodiment, each protruding portion4122of the dielectric layer4120may have a variable horizontal cross-sectional area that decreases strictly with a vertical distance from the planar surface of the planar portion of the dielectric material layer4120. In one embodiment, each protruding portion4122of the dielectric material layer4120may have a conical shape.

In one embodiment, a seam3779of the core conductive material layer106may extend vertically from an apex of each protruding portion4122of the dielectric material layer4120as illustrated inFIG. 41H. In one embodiment, a substrate (such as a passivation substrate3770) contacting another planar surface of the planar portion of the dielectric material layer4120may be provided. Such a substrate3770may be vertically spaced from the layer stack (103,104,105,107a,106) by the planar portion of the dielectric material layer4120. In one embodiment, each protruding portion4122may have a lateral dimension less than 10 microns (which may be less than 5 microns, and may be, for example, in a range from 10 nm to 3 microns) and a height less than 100 microns (for example, in a range from 0.3 micron to 10 microns).

In one embodiment, the moldable material layer (3720,3820) may be an optically transparent layer. In this case, the optically transparent layer (3720,3820) may overlie, and laterally surround protruding portions of, the layer stack (103,104,105,107a,106). The entirety of a top surface of the optically transparent layer (3720,3820) (that does not contact the layer stack) may be planar. In one embodiment, the sheet substrate3710may be a transparent substrate, which is located on the top surface of the optically transparent layer (3720,3820). In one embodiment, the optically transparent layer (3720,3820) may have a refractive index less than the refractive index of the transparent conductive material layer103to induce refraction at the interface between the optically transparent layer (3720,3820) and the transparent conductive material layer103.

The optically transparent material of the optically transparent layer (3720,3820) may be any transparent material that may be employed for the moldable material layer (3720,3820) of the first exemplary photovoltaic structure, or any transparent material that may be employed for the moldable material layer3820of the second exemplary photovoltaic structure. In one embodiment, the optically transparent layer (3720,3820) comprises a polymer material. In one embodiment, the optically transparent layer (3720,3820) comprises a moldable material selected from a lacquer, a silicone precursor material, a gel derived from a sol containing a polymerizable colloid, and a glass transition material. In one embodiment, the optically transparent layer (3720,3820) comprises a moldable material selected from a polymer resin-based plastic material, an organic material including at least one resin, a flexible glass material based on silica, phenylalkyl catechol-based lacquers, nitrocellulose lacquers, acrylic lacquers, water-based lacquers, silicone, a gel of silicon oxide, and a gel of dielectric metal oxide. In one embodiment, the optically transparent layer (3720,3820) comprises a polymer material.

Referring toFIG. 43A, a fifth exemplary photovoltaic structure is illustrated during a manufacturing step. A sheet substrate3710and a moldable material layer3720having a uniform thickness may be provided as in the case of the first and third exemplary photovoltaic structures. For example, the moldable material layer3720may include an optically transparent material selected from a lacquer, a plastic material, a resin material, a silicone precursor material, a gel derived from a sol, and a glass transition material. The processing steps illustrated inFIG. 39may be employed to patterning a top surface of the moldable material layer3720with an array pattern. In one embodiment, the moldable material layer3720may be patterned by imprinting a die including a pattern of recessed structures and incorporated into a web onto the moldable material layer3720. In one embodiment, the patterned moldable material layer3720includes a pattern of dielectric cores3722. In one embodiment, the dielectric cores3722may be nanorods, which are structures each having a shape of a rod and having at least one nanoscale dimension (i.e., a dimension less than 1 micron). For example, a diameter of a topmost portion of each dielectric core3722may be less than 1 micron.

In this case, the array pattern may comprise a pattern of dielectric cores3722extending upward from the top surface of the moldable material layer3720. Each dielectric core3722may be a patterned portion of the moldable material layer3720. The array pattern includes an array of vertically extending shapes3722that protrude upward from that top surface of the moldable material layer3720. Each vertically extending shape3720may be a dielectric core3722of a respective photovoltaic bristle to be subsequently formed.

Referring toFIG. 43B, a layer stack (103,104,105,107a,106) is deposited over the array pattern. The layer stack comprises a core conductive material layer106, an optional inner transparent conductive layer107a, a photovoltaic material layer (105,104), and a transparent conductive material layer103. Specifically, the core conductive material layer106may be deposited on the top surface of the planar portion of the moldable material layer3720and the dielectric cores3722(vertically extending portions) of the moldable material layer3720. The optional inner transparent conductive layer107amay be deposited on the core conductive material layer106. The photovoltaic material layer (105,104) may be deposited on the optional inner transparent conductive layer107aand over the core conductive material layer106. The transparent conductive material layer103may be formed on the photovoltaic material layer (105,104). The thickness and composition of each layer within the layer stack (103,104,105,107a,106) may be the same as in the first, second, third, or fourth exemplary photovoltaic structures.

A two-dimensional array of photovoltaic bristles (103,104,105,107a,106,3722) is formed. Each photovoltaic bristle (103,104,105,107a,106,3722) comprises a vertically protruding portion of the layer stack (103,104,105,107a,106) and embedding a dielectric core3722comprising a dielectric material. The dielectric core3722contacts a sidewall of the core conductive material layer106. The transparent conductive material layer103is spaced from the core conductive material layer106by the photovoltaic material layer (105,106).

Referring toFIG. 43C, a dielectric material layer4320is deposited over the layer stack (103,104,105,107a,106). The dielectric material layer4320may include any of the transparent materials that may be employed for the dielectric material layer4210of the third and fourth exemplary photovoltaic structures. In one embodiment, the dielectric material layer4320may include ethylene vinyl acetate. The dielectric material layer4320may be deposited by a conformal deposition method or a self-planarizing deposition method. The thickness of the dielectric material layer4320, as measured over a topmost surface of the transparent conductive material layer103, may be in a range from 0.5 micron to 20 microns, although lesser and greater thicknesses may also be employed. The top surface of the dielectric material layer4320may be planar as formed if a self-planarizing deposition process (such as spin coating) is employed, or may be planarized, for example, by polishing.

Subsequently, a passivation substrate4310having a planar bottom surface may be disposed on a top surface of the dielectric material layer4320. The passivation substrate4320comprises an optically transparent material. The passivation substrate4320may include a material such as glass, sapphire, an optically transparent polymer material, or an optically transparent plastic material.

FIG. 43Dis an exploded view of the fifth exemplary photovoltaic structure after formation of the passivation substrate4310. The combination of the sheet substrate3710and the moldable material layer3720may be replaced with a moldable material layer3820that functions as a substrate that provides mechanical support to provide a sixth exemplary photovoltaic structure.FIG. 43Eprovides a see-through perspective view of the fifth or sixth exemplary photovoltaic structure.

FIGS. 44A-44Care magnified views of various embodiments of a photovoltaic bristle of the fifth exemplary photovoltaic structure. The various dimensions such as a taper angle α, a base lateral dimension bd, a tapered-end lateral dimension td, the frustum height h1, and the height h of the bristle3700may be the same as in the various embodiments of the first exemplary photovoltaic structure.FIG. 44Aillustrates a photovoltaic bristle including a hemi-spheroid region.FIG. 44Billustrates a photovoltaic bristle including a substantially planar top surface.FIG. 44Cillustrates a photovoltaic bristle including a transparent conductive material as the material of the core conductive material layer106.

Referring toFIG. 45, a sixth exemplary photovoltaic structure may be derived from the fifth exemplary photovoltaic structure by substituting a moldable material layer3820for a combination of a sheet substrate3710and a moldable material layer3820. In other words, the combination of the sheet substrate3710and the moldable material layer3720of the fifth exemplary photovoltaic structure is replaced with the moldable material layer3820that provides mechanical support to the photovoltaic bristles of the sixth exemplary photovoltaic structure.

Each of the fifth and sixth exemplary photovoltaic structures comprises a dielectric material layer (3720,3820), which is a moldable material layer. The dielectric material layer (3720,3820) comprises a planar portion having a uniform thickness and an array of protruding portions3722extending from a planar surface of the planar portion; and a layer stack (103,104,105,107a,106) located on the dielectric material layer (3720,3820) and comprising a core conductive material layer106, a photovoltaic material layer (104,105), and a transparent conductive material layer103. The core conductive material layer106is in contact with the planar surface and the protruding portions3722of the dielectric material layer (3720,3820). The transparent conductive material layer103is spaced from the core conductive material layer106by the photovoltaic material layer (104,105). Each combination of a protruding portion3722of the dielectric material layer (3720,3820) and portions of the layer stack (103,104,105,107a,106) surrounding the protruding portion3722constitutes a photovoltaic bristle (103,104,105,107a,106,3722).

In one embodiment, the dielectric material layer (3720,3820) comprises a self-planarizing polymer material, which forms a film of a uniform thickness prior to imprinting, and is subsequently cured to provide the dielectric cores3722that do not change shapes. In one embodiment, the dielectric material layer (3720,3820) comprises an optically transparent material. The core conductive material layer106is deposited on surfaces of the dielectric cores3722and the top surface of the planar portion of the dielectric material layer (3720,3820), i.e., the moldable material layer. The photovoltaic material layer (104,105) is deposited on the core conductive material layer106. The transparent conductive material layer103is deposited on the photovoltaic material layer (104,105).

In one embodiment, the entirety of the dielectric material layer (3720,3820) may be a single material layer without any interface or seam therein. In one embodiment, the entirety of the dielectric material layer (3720,3820) may have a homogeneous material composition throughout. In one embodiment, the dielectric material layer (3720,3820) comprises an optically transparent material. In one embodiment, each protruding portion (i.e., each dielectric core3722) of the dielectric material layer (3720,3820) may have a variable horizontal cross-sectional area that decreases strictly with a vertical distance from the planar surface of the planar portion of the dielectric material layer (3720,3820). In one embodiment, each protruding portion of the dielectric material layer may have a conical shape.

In one embodiment, a substrate (e.g., a sheet substrate3710) contacting another planar surface of the planar portion of the dielectric material layer3720and vertically spaced from the layer stack (103,104,105,107a,106) by the planar portion of the dielectric material layer3720. In one embodiment, each protruding portion3722may have a lateral dimension less than 10 microns and a height less than 100 microns.

In one embodiment, an optically transparent layer4320may overlie the layer stack (103,104,105,107a,106). The entirety of the top surface of the optically transparent layer4320may be planar. A transparent substrate (such as a passivation substrate4310) may be located on the top surface of the optically transparent layer4320. The optically transparent layer4320may have a refractive index less than a refractive index of the transparent conductive material layer103. In one embodiment, the optically transparent layer4320may comprise a polymer material, which may be any transparent material that may be employed for the dielectric material layer4120discussed above.

In one embodiment, the dielectric material layer (3720,3820) of the fifth or sixth exemplary photovoltaic structure may comprise a moldable material selected from a lacquer, a silicone precursor material, a gel derived from a sol containing a polymerizable colloid, and a glass transition material. In one embodiment, the dielectric material layer (3720,3820) comprises a moldable material selected from a polymer resin-based plastic material, an organic material including at least one resin, a flexible glass material based on silica, phenylalkyl catechol-based lacquers, nitrocellulose lacquers, acrylic lacquers, water-based lacquers, silicone, a gel of silicon oxide, and a gel of dielectric metal oxide. In one embodiment, the dielectric material layer (3720,3820) comprises a polymer material.