Abstract:
This application relates to systems and methods for improving solar cell efficiently by enabling more light to be captured by the absorber layer. The reflector layer in a solar cell may be designed to reflect light back into the absorber layer that has already passed through the absorber layer. The reflector layer may include a surface protrusion that has a surface that has an angle of approximately 45 degrees. Incident light is reflected from that surface towards the absorber layer or towards the reflector layer which, in turn, reflects the light back towards the absorber layer or the silicon stack. The light may be reflected at an angle that enables the light to have total internal reflection within the silicon layer (e.g., absorber layer, μc-Si layer, and a-Si layer).

Description:
FIELD OF DISCLOSURE 
       [0001]    This disclosure relates to solar photovoltaic conversions devices. More particularly to a method and apparatus for improving the energy conversion efficiency in a solar cell device using solar cell design that enables a higher amount of light to be converted to energy by trapping the light in the solar cell. 
       BACKGROUND OF THE INVENTION 
       [0002]    Solar photovoltaic conversions devices can convert light into electrical energy using an absorber layer that uses photons from incident light to create electron-hole pairs. Generally, the absorber lay is relatively thin to enable the electrons and holes to reach membrane layer by making the absorber layer thickness smaller than the diffusion lengths of the charge carriers. As a result, light may not be totally absorbed by the absorber layer in a single pass. The absorber layer may be thickened to absorb more light, but this increases cost of the solar cell device. Another approach may be to design a solar cell that diffuses the light more broadly across the absorber layer. However, the random scattering causes the light path to increase which results in a limitation on energy conversion by letting light escape from the solar cell. Accordingly, solar cell designs that prevent light from escaping may be desirable. 
       SUMMARY 
       [0003]    Broadly, converting solar energy to electrical energy is based on photons of incident radiation (e.g., light) generating electron-hole pairs within the silicon layer(s) of a solar cell to force charge carriers in the silicon layer(s) to move (e.g., current flow). The silicon layer may include an absorber layer with p-type silicon layer(s) and n-type silicon layer(s) on either side. The electron and holes generated in the absorber layer should reach the p-type or n-type silicon layer. This movement can be accomplished by making the absorber layer thinner than the diffusion lengths of the electrons and holes. Generally, below the silicon layer may be a reflector layer that reflects light back into the silicon layer to generate additional electron-hole pairs. However, the reflected light may escape the silicon layer and may not further contribute to electron-hole pair generation. This disclosure describes systems and methods for trapping reflected light (e.g., photons) within the silicon layer to increase electron-hole pair generation per unit of light. Trapping may be explained using the total internal reflection principle. 
         [0004]    Total internal reflection of a propagating wave (e.g., light) can occur when a wave attempts to travel between a propagating medium that has a higher refractive index than an adjacent propagating medium. However, total internal reflection may also depend on the incident angle of the wave. For example, total internal reflection may occur when the incident angle is greater than a critical angle that may be dependent upon the refractive index of each propagating medium. In this way, light may be trapped within a propagating medium as long as the incident angle is greater than the critical angle. As a result, trapped light (e.g., photons) may generate more electron-hole pairs in the silicon layer than a single or double pass of a light through the silicon layer. 
         [0005]    In one embodiment, the solar cell may comprise a glass layer or substantially transparent layer, a silicon layer(s), and a reflector layer. The glass layer may also include a light concentration layer or component that directs incident light through the glass layer and the silicon layer to a focal point in the reflector layer. The silicon layer may include a reflection notch that may be substantially filled by the reflector layer and adjacent to the focal point. The reflection notch may be configured to reflect at least a portion of the incident light towards the boundary of the silicon layer and the reflector layer. When the refractive index of the silicon layer may be higher than the refractive index of the reflector layer then total internal reflection may occur. The geometry of the reflection notch may be configured to reflect at least a portion of the incident light such that the incident angle of the reflected light at the silicon-reflector layer boundary is greater than the critical angle. In this way, light may be trapped within the silicon layer per the total internal reflection principle. 
         [0006]    The reflection notch may be formed in the silicon layer(s) using a variety of techniques that are optimized to form a reflective surface. The reflective surface may be designed to reflect incident light towards silicon-reflector layer interface so that the reflected light may be totally reflected at the silicon-reflector layer interface. The reflection notch may be generated by selective etching (e.g., wet or dry etch), selective imprinting, or selective formation of topology. 
         [0007]    In one embodiment, selective formation of topology may be implemented by altering the substrate surface of a first solar cell layer to impact the formation of a second solar cell layer that may be deposited on the first solar cell layer. For example, the glass substrate layer may be etched to form a 3-dimensional pattern on the surface. Subsequent solar cells layer may conform to the pattern and form a reflection notch that is aligned with the light concentration module on the glass layer surface. 
         [0008]    Described herein are several embodiments related to the current density control across the anode assembly. Note that this summary section does not specify every embodiment and/or incrementally novel aspect of the present disclosure or claimed invention. Instead, this summary only provides a preliminary discussion of different embodiments and corresponding points of novelty over conventional techniques. For additional details and/or possible perspectives of the invention and embodiments, the reader is directed to the Detailed Description section and corresponding figures of the present disclosure as further discussed below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The features within the drawings are numbered and are cross-referenced with the written description. Generally, the first numeral reflects the drawing number where the feature was first introduced, and the remaining numerals are intended to distinguish the feature from the other notated features within that drawing. However, if a feature is used across several drawings, the number used to identify the feature in the drawing where the feature first appeared will be used. Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale and wherein: 
           [0010]      FIG. 1  illustrates a representative embodiment of a solar cell environment and a solar cell design described in one or more embodiments of the disclosure. 
           [0011]      FIG. 2  illustrates a solar cell with a light concentration component and a focal point of the light concentration component as described in one or more embodiments of the disclosure. 
           [0012]      FIG. 3  illustrates a solar cell and a path of light through the solar cell as described in one or more embodiments of the disclosure. 
           [0013]      FIG. 4  illustrates a portion of the solar cell the path of light reflected within the solar cell as described in one or more embodiments of the disclosure. 
           [0014]      FIG. 5  illustrates a solar cell that includes a plurality of light reflection features as described in one or more embodiments of the disclosure. 
           [0015]      FIG. 6  illustrates another embodiment of a solar cell as described in one or more embodiments of the disclosure. 
           [0016]      FIG. 7  illustrates another embodiment of a solar cell as described in one or more embodiments of the disclosure. 
           [0017]      FIGS. 8A-8B  illustrates a flow diagram of a solar cell manufacturing method with accompanying illustrations as described in one or more embodiments of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Disclosed herein include systems and methods for a solar cell design that reflects light within the silicon layer(s) of the solar cell. The topography of the silicon layer(s) and the reflector layer are configured to reflect incident light along the silicon layer(s). 
         [0019]    Of course, the order of discussion of the different steps as described herein has been presented for clarity sake. In general, these steps can be performed in any suitable order. Additionally, although each of the different features, techniques, configurations, etc. herein may be discussed in different places of this disclosure, it is intended that each of the concepts can be executed independently of each other or in combination with each other. 
         [0020]      FIG. 1  illustrates a solar cell environment  100  and a solar cell design  102  that may be used in used in a solar conversion panel  104 . Generally, a solar panel  104  receives light  106  (e.g., photons) from the sun  108  to convert the light  106  into electrical energy for electrical devices (not shown). In this embodiment, the solar panel  104  is installed in a ground  110  site, but this solar cell design  102  is not limited to solar panels  104  installed in the ground  110 . For example, the solar panel  104  may mounted on a building (not shown) or home (not shown) or anywhere light  106  or electromagnetic radiation may be found. Another embodiment of the solar panel  104  may be embedded in an electrical device (not shown) to generate electrical current to power the device or store in a battery. The electrical device may include, but is not limited to, smart phones, tablets, laptop computers, lighting fixtures, automobiles, and/or any wireless mobile device. 
         [0021]    The solar cell design  102  may include, but is not limited to, a light concentration component  112 , a substantially transparent layer  114  (e.g., glass), a silicon layer(s)  116  that use light  106  (e.g., photons) to generate electrical energy, and a reflector layer  118 . 
         [0022]    In this embodiment, a reflection notch  120  may be incorporated into the interface of the silicon layer  116  and the reflector layer  118 . The light concentration component  112  may focus, direct, or concentrate the light  106  towards the reflection notch  120 . The light  106  may be reflected by the reflection notch  120  towards the silicon-reflector interface. The light  106  may be reflected towards the glass-silicon interface. When the incident angle (not shown) of the light  106  at the glass-silicon interface is greater than a critical angle (not shown) will enable at least a majority of the light  106  to be reflected back within the silicon layer  116 . The critical angle (not shown) may be determined based, at least in part, on the principle of total internal reflection which enables propagating waves (e.g., light  106 ) to completely reflect from an interface of two wave mediums, such as the silicon layer  116  and the reflector layer  118 . The principle of total internal reflection will be described in greater detail in the description of the remaining figures. 
         [0023]    In other embodiments, the solar cell design  104  may include additional layers (e.g., transparent conductive oxides, etc.) or components to generate electrical energy. The silicon layer  116 ( s )  116  may include multiple silicon layers  116  that may be used to generate electrical energy and transfer electrical energy from the solar cell  102  to the electrical device. The silicon layers  116  may include different dopant concentrations (e.g., p-type, n-type, intrinsic, etc.), crystal structures (e.g., microcrystalline, amorphous, etc.) and/or surface textures. 
         [0024]      FIG. 2  illustrates one embodiment of a cross section of the solar cell  102  with a light concentration component  112  and a focal point  200  of the light concentration component  112  located in the reflector layer  118 . In other embodiments, the focal point  200  may be located anywhere along the principal axis  202 . 
         [0025]    In the  FIG. 2  embodiment, the light concentration component  112  may be made of a substantially transparent material, such as amorphous or crystalline ceramic, glass, plastic, formed either by photolithography, embossing, molding, or self assembly of particles that may allow light  106  to pass through into the substantially transparent layer  114  (e.g., glass). In this instance, the light concentration component  112  is symmetrical along a principal axis  202  that is aligned with the focal point  200 . The design of the light concentration component  112  may be, but is not limited to, a spherical plano-convex lens which may have one side that is spherical and the opposite side may be substantially flat or conformal with the transparent layer  114 . In other embodiments, the light concentration component  112  may be one of the following: biconvex, positive meniscus, negative meniscus, plano-concave, or biconcave. Alternatively, in other embodiments, the light concentration component  112  may be asymmetrical and the focal point  200  may be in any of the layers within the solar cell  102 . In some embodiments, the light concentration component  112  may be part of an array as shown in  FIG. 5 . 
         [0026]    The focal point  200  may be the point on the principal axis  202  in which light  106  that passes through the light concentration component may converge together. The location of the focal point  200  may vary horizontally or vertically as shown in  FIG. 2  depending on the type and/or design of the light concentration component  112 . As shown in the  FIG. 2  embodiment, the focal point  200  is located within the reflector layer  118  which results in the paths of light  106  intersecting the reflection notch  120  at different points and prior to converging at the focal point  200 . In other embodiments, the light  106  may reflect off the reflection notch  120  in various directions, as shown in  FIG. 3 . Controlling the direction of the reflected light  106  may be based, at least in part, on the geometry of the reflection notch  120  and the location of the focal point  200 . Ideally, a portion of the reflected light  106  may be reflected towards the reflector layer  118  and the silicon layer  116  in a way that enables the light  106  to be trapped within the silicon layer  116  under the principle of total internal reflection, as described in the description of  FIG. 4 . 
         [0027]    The reflection notch  120 , as shown in  FIG. 2 , is cross section of a pyramid-like or cone-like structure that protrudes up from the reflector layer  118  into the silicon layer  116 . The reflection notch  120  may also be an angular cut or indentation into the silicon layer  116 . The shape and geometry of the reflection notch  120  may vary depending the size and composition of the solar cell  102  in addition to the light concentration component  112  configuration. As noted above, the reflection notch  120  may be designed to reflect light  106  in manner that enables the light  106  to be confined within the silicon layer  116 . This may allow additional electron-hole pairs (not shown) to be formed using the same photon of light  106 . For example, light  116  may be reflected three or more times within the silicon layer  116  than when the reflection notch  120  is not present. An example of how this may be accomplished will be described in the description of  FIG. 3 . 
         [0028]      FIG. 3  illustrates one embodiment of how light  106  may be reflected off the reflection notch  120  to enable total internal reflection within the silicon layer  116 . In the  FIG. 3  embodiment, a cross section of the solar cell  102  is shown with paths of light  106  passing through the solar cell  102  layers (e.g., transparent layer  114 , etc.) to the reflection notch  120 . The reflected light  300  may be reflected off the reflection notch  120  and then the surface of the reflector layer  118  back into the silicon layer  116 . As noted in the description of  FIG. 2 , the light  106  converges towards the focal point  200  and impacts the reflection notch  120  which, in this embodiment, is above the focal point  200 . Accordingly, the reflection notch  120  may include a single pyramid or cone, or a one direction light reflector. The apex of the element can have an angle varying from 0 to 80° with respect to the plane to induce a portion of the reflected light  300  to impact the transparent layer  114  surface for a second time at or below the critical angle (not shown) to maintain total internal reflection of the light  106  within the silicon layer  116 . The critical angle (not shown) for implementing total internal reflection will be discussed in the description of  FIG. 4 . 
         [0029]      FIG. 4  illustrates a modified solar cell  400  that only shows the silicon layer  116  and the reflector layer  118  of the solar cell  102  for the purpose of ease of explanation of the solar cell  102  design. The modified solar cell  400  highlights several surfaces that may be used to measure angles related to light incidence or reflection notch  120  geometry. These surfaces are merely one example of how the solar cell  102  may be designed to facility total internal reflection of light  106  within the silicon layer  116 . 
         [0030]    They surfaces may include, but are not limited to, a reflector layer surface  402  at the silicon layer  116  and reflector layer  118  interface, a silicon layer surface  404  at the silicon layer  116  and transparent layer  114  (not shown) interface. The reflection notch surface  406  may also be at the silicon layer  116  and reflector layer  118  interface, but may not be on the same plane as the reflector layer surface  402 . Although all of the surfaces are shown as planar, they are not required to be absolutely planar and may have significant non-uniformity. In which case, the surface planes may be approximated to a plane that is an average or a mean of the surface that forms the silicon layer  116  and reflector layer  118  interface or the silicon layer  116  and transparent layer  114  (not shown) interface that may refract or reflect light  106 . 
         [0031]    The reflection notch angle  408  may represent how much the reflection notch  120  may protrude from the reflector layer  118  into the silicon layer  116 . In one embodiment, the reflection notch angle  408  may be measured between the intersection of the reflector layer surface  402  and the reflection notch surface  406 . The reflection notch angle  408  may range between 15° and 80° and may vary in view of the focal point  200 , the light concentration component  112 , the incident light angle  410 , the reflected angle  412 , and the critical angle  414 . 
         [0032]    The incident light angle  410  may represent the angle between the intersection of the principal axis  202  and the light  106  that is incident upon the reflection notch  120 . The intersection may be at the focal point  200 . Generally, there may be not set absolute value for each instance of light  106  (e.g., light  106  in  FIG. 3 ) but may include a range of 0° to 70° in view of the reflection notch angle  408  and the critical angle  414 . The incident light  106  may be reflected towards the surface of the reflector layer  118  and be reflected again toward the silicon layer based, at least in part, on the reflected light angle  412 . 
         [0033]    The reflected light angle  412  may represent the angle between the intersection of the reflector layer surface  402  and the reflected light  106  from the reflection notch  120 . The incident light angle  410  and the reflection notch angle  408  may have a relatively large impact on the reflected light angle  412 . For total internal reflection, the incident light angle  410  may be lower than 2 times the reflection notch angle  408  minus the critical angle  414 . The light  106  reflected back into the silicon layer  116  may also induce additional electron-hole pair generation. However, to generate more electron-hole pairs the light  106  may need to be reflected back into the silicon layer  116  when the light intercepts the transparent/silicon layer interface. Under the principle of total internal reflection, the light may intercept the transparent/silicon layer interface at a critical angle  414 . 
         [0034]    The critical angle  414  determines whether the incident light may reflect back into the silicon layer  116  when the light  106  reaches the silicon-transparent layer interface. The critical angle  414  may be equal to or greater than the critical angle  414  to enable the light  106  to be reflected into the silicon layer  116  and not refracted into the transparent layer  114  (not shown). As noted above in the description of  FIGS. 1-3 , the complete or substantially complete reflection of the light  106  falls under the principle of total internal reflection. In this way, the light  106  may continue to reflect or travel through the silicon layer  116  without substantially crossing into the transparent layer  114  or the reflector layer  118 . The additional time spent in the silicon layer  116  may result in a higher amount of electron-hole pairs being generated than if the light  106  was refracted out of the silicon layer  116  into the transparent layer  114 . The critical angle  414  should be less than a predetermined amount that may be based, at least in part, on index of refraction of the transparent layer  114  and the silicon layer  116 . The critical angle  414  (θ C ) may be determined based on the following equation: 
         [0000]    
       
         
           
             
               θ 
               C 
             
             = 
             
               arcsin 
                
               
                 ( 
                 
                   
                     n 
                     2 
                   
                   
                     n 
                     1 
                   
                 
                 ) 
               
             
           
         
       
     
         [0035]    Wherein n 2  is the index of refraction for the transparent layer  114  and n 1  is the index of refraction for the silicon layer  116 . The critical angle  414  may be measured from a perpendicular plane  416  that extends out from the point of intersection between the light  106  and the silicon-transparent layer  114  interface or the silicon layer surface  404 . The material for total internal reflection could be metal or ceramic. 
         [0036]    In some embodiments, the solar cell  102  may include multiple reflection notches  120  to enable total internal reflection of light  106  throughout a larger surface area than the solar cell  102  shown in  FIGS. 1-4 .  FIG. 5  illustrates a solar cell  500  that includes a plurality of light  106  reflection features over a surface area as shown in solar cell  500 . To minimize escape of light from reflection with another reflection notch, the distance between two notches  120  may be larger than the thickness of the layer  116 . In the  FIG. 5  embodiment, the solar cell  500  is shown in cross section with several light concentration components  112  aligned next to each other and on top of the transparent layer  114 . In this instance additional (not shown) light concentration components  112  may be arranged across the surface of the transparent layer  114  in several directions. 
         [0037]    In one embodiment, the light concentration components  112  may each include a corresponding reflection notch  120  that aligned along the principal axis  202 . In this way, each of the reflection notches  120  may be able to reflect light  106  in a way that may enable total internal reflection as described above in the description of  FIGS. 1-4 . However, in other embodiments, each of the light concentration components  112  may not each have their reflection notch  120 . The density of the reflection notches  120  may be lower to facilitate or maintain total internal reflection of light  106  over a longer distance within the silicon layer  116 . The additional reflection notches  120  may interfere or alter the angle of light that may have already been reflected back from the transparen layer  114 . Accordingly, there may be one or more adjacent light concentration components  112  that may not have a reflection notch  120  aligned along the principal axis  202  of the light concentration component  112 . 
         [0038]    Solar cell  102  is not limited to the layers shown in  FIGS. 1-5  and may include one or more additional layers between any of the other layers.  FIG. 6  illustrates another embodiment of a solar cell  600  that may include an oxide layer  602  in between the transparent layer  114  and the silicon layer  116 . The metal-oxide layer  602  may include, but is not limited to, a metal oxide that is substantially transparent (e.g., transparent conductive oxide) and may include a polycrystalline or an amorphous microstructure. The metal-oxide layer  602  can include, but is not limited to, aluminum-doped zinc oxide, tin-doped indium zinc oxide, and tin-doped cadmium oxide. Additional dopants that may be incorporated into a metal oxide may include, but is not limited to: F, Nb, Ga, Ge, Hf, Mg, Mo, Ta, Y, Zr, W, B, V, Ti, and As. In other embodiments, an additional metal-oxide layer (not shown) may be between the silicon layer  116  and the reflector layer  118 . 
         [0039]    Manufacturing the solar cell  600  may be done using selective etching techniques to form the reflection notch  120 . The selective etching methods may include patterning processes that may designate which portions of the substrate that may be etched or left in place. Prior to and after the selective etching, one or more cleaning processes may also be used to prepare the substrate for patterning and etching and/or post-etch cleaning. Selective etching or removal of material may be accomplished through photolithography patterning and plasma etching or laser ablation. 
         [0040]    Photolithography may include using light sensitive films to put a sacrificial pattern on top of the substrate and plasma etching may be used to remove portions of the substrate that are not covered by the pattern. Laser ablation may include using a laser to etch a pattern into the substrate. This may involve moving the laser along the substrate that may remove portions of the substrate where the laser contacts the substrate. 
         [0041]    In view of the aforementioned solar cell  102  design, the alignment of the light concentration component  112  and the reflection notch  120  may be needed. However, selectively etching multiple layers, or even one layer, to align with other features in the solar cell  102  may be costly and time consuming. One embodiment that may reduce manufacturing cost and time may include a self-aligned process that assists with aligning the features of the solar cell  102 . One embodiment of the self-aligned solar cell  700  will be described in the description of  FIG. 7 , while one specific manufacturing method that will be described in the description of  FIGS. 8A-8B . 
         [0042]      FIG. 7  illustrates one embodiment of a self-aligned solar cell  700  that may be manufactured using a self-aligned process that may substantially align the light concentration component  112  with the reflection notch  120  and focal point  200  on the principal axis  202 . Again, the solar cell  700  may include additional layers that are not shown in  FIG. 7  and are not shown here for the purpose of ease of explanation of the of solar cell  700  structure. 
         [0043]    In contrast to solar cell  600 , the self-aligned solar cell  700  may include an alignment notch  708  in the transparent substrate layer  702  that may be similar to the transparent substrate  114 . The alignment notch  708  may be aligned with the light concentration component  112  during the selective etching process (e.g., laser ablation). For example, the laser may be shot through the light concentration component  112  to remove a portion of the transparent layer  702  that is opposite the light concentration component  112 . The laser may travel through the transparent layer  702  to remove a portion of material that on the opposite side from the light concentration component. 
         [0044]    The alignment notch  708  may include a metal-oxide layer  704  that may be similar to the metal-oxide layer  602  described in the description of  FIG. 6 . In this embodiment, the metal-oxide layer  704  fills a portion of the reflection notch  120  with the remainder being filled by the silicon layer  706 . In this embodiment, the oxide layer  702  is very conformal with the alignment notch  708 . As shown, the metal-oxide layer  704  follows the form of the alignment notch  708  very closely. This may be due to the thickness of the metal-oxide layer  704 . In contrast, the silicon layer  116  may be thicker than the metal-oxide layer  704  and may be less conformal with the alignment notch  708 . For example, the silicon layer  116  may have to fill a larger portion of the alignment notch  708  than the metal-oxide layer  704 . As a result, the silicon layer surface  404  that is opposite the alignment notch  708  may form a divot or notch that may be filled by the reflector layer  118  to form the reflection notch  120 . The reflection notch may be formed using other techniques and the description of  FIG. 7  is one specific embodiment used to form the self-aligned solar cell  700 . 
         [0045]      FIGS. 8A-8B  illustrates a flow diagram of a method  800  to manufacture a self-aligned solar cell  700 . The method  800  also includes corresponding illustrations next to each description of the method  800 . The solar cell  700  may be manufactured using a self-aligning strategy between the light concentration component  112  and the reflection notch  120 , such that the focal point  200  for the light concentration component  112  is also substantially aligned with the reflection notch  120 . The method  800  is one embodiment for generating the solar cell  700  and the step order may be configured differently and may include additional steps or omit steps in the illustrated method  800 . 
         [0046]    At step  802 , a transparent substrate  114  for a solar cell  700  may have a light concentration component  112  formed on one of its surfaces. In the illustrated embodiment, a single light concentration component  112  is shown. However, in other embodiments, two or more light concentration components  112  may be adjacent to each other, as shown in  FIG. 5 . The transparent substrate  114  may include, but is not limited to, glass that will enable light  106  to pass through from one side of the glass to another side of the glass. The light concentration component  112  may be coupled to or adhered to the surface of the glass. Similarly, light  106  should be able to pass through the light concentration component  112  and enter the glass. The light concentration component  112  may be enable to focus incident light  106  towards a focal point  200 . As noted above in the description of  FIG. 1 , the light concentration component  112  may include, but is not limited to, a spherical plano-convex lens that may receive light  106  along a spherical portion of the lens and reflect the light  106  towards substantially flat side of the lens. The substantially flat portion may be coupled to the glass. The lens may be a transparent material, as amorphous or crystalline ceramic, glass, plastic, formed either by photolithography, embossing, molding, or self assembly of particles. 
         [0047]    The light concentration component  112  may have a focal point  200  that needs to be aligned with a reflection notch  120  that may be formed by a blanket film deposition process without selectively etching that the deposited film. In this embodiment, the self-alignment may use the light concentration component  112  to pattern the transparent substrate  114  in a way that forms the reflection notch  120  using a blanket deposition process for the reflector material. 
         [0048]    At step  804 , a trench may be formed in the transparent layer  702  by using a laser that is focused by the light concentration component  112 . The laser ablation may remove a portion of the transparent layer  702  that is on the opposite side from the light concentration component  112 . In one embodiment, the laser may be configured to form the trench so that the trench width is greater than the trench depth. The aspect ratio trench depth over trench width may be lower 0.5 and with a depth in the range 0.5 micron to 40 microns. The trench may include two opposing surfaces that form the trench depth and another surface connected to the two opposing surfaces. The connecting surface may represent the trench width. The trench width and depth may vary to accommodate various sizes of the reflection notch  120 . A deeper trench may increase the height of the reflection notch  120  and a wider trench may increase the width of the reflection notch  120 . Generally, the trench surfaces may be configured to adhere to an overlying film. 
         [0049]    At step  806 , a transparent electrode layer  704  or metal-oxide layer may be deposited on the transparent substrate  702  and may, at least, partially fill the trench. The fill may be substantially conformal to the trench features and may be a less thickness than the transparent substrate  702  thickness. The transparent electrode layer  704 , as described in  FIGS. 6-7 , may be a metal-oxide that may be doped with one or more materials. The transparent electrode layer  704  may be configured to transmit incident light  106  from the metal-oxide/glass interface to the opposite side of the metal-oxide layer and into another film layer that may be adhered to the metal-oxide layer. 
         [0050]    At step  808 , a silicon layer  706  may be deposited on the transparent electrode layer  704  and may fill the remainder of the trench in a substantially conformal manner. A notch in the silicon layer  706  may be formed by the silicon layer  116  as a result of conforming to the trench. As shown in the corresponding diagram, the notch may be opposing the trench from the upper surface of the silicon layer  116 . Although substantially triangular in the cross section illustration, the notch may be substantially conical or pyramid-like in three dimensions. The notch geometry may be based, at least in part, on the trench width, trench depth, trench length, and the deposition rate of the silicon layer(s)  116 . As noted in the description of  FIG. 1 , the silicon layer  116  may be a combination of multiple silicon layers  116  with differing dopant concentrations and/or microcrystalline structures. The silicon layer  116  may also transmit light  106  from the metal-oxide/silicon interface towards the notch and to a film layer that may fill the notch. 
         [0051]    At step  810 , the reflector layer  118  may be deposited over the silicon layer  116  and substantially fills the notch in the silicon layer  116 . The reflector layer  118  may form the reflection notch  120  by filling the notch in the silicon layer  116 . The reflection notch  120  may reflect substantial portion of light  106  from the silicon layer  116  towards the reflector/silicon interface that may surround the reflection notch  120 . As noted in the description of  FIGS. 2-5 , the light  106  may be reflected from the reflector/silicon interface (e.g., reflector layer surface  402 ) towards the metal-oxide/silicon interface (e.g., silicon layer surface  404 ). The reflection notch  120  and the focal point  200  may be arranged to reflect light  106  at an angle that may enable total internal reflection within the silicon layer  116 . As described in the description of  FIG. 4 , total internal reflection may mean the light  106  that intersects the metal-oxide/silicon interface (e.g., silicon layer surface  404 ) at or less than the critical angle  414  may be completely reflected back into the silicon layer  116 . In this way, the energy conversion process may be made more efficient by using the same photon of light  106  three or more times instead of just twice. 
         [0052]    Although only certain embodiments of this application have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.