Solar cell modules and methods of manufacturing the same

Back contact solar cell modules and methods of manufacturing the same. The solar cell module comprises a back surface with a plurality of first electrodes and a plurality of second electrodes formed thereon, the plurality of first electrodes and the plurality of second electrodes being of opposite polarities, the back surface being configured to form an electric field thereon of the opposite polarity as the plurality of first electrodes; a first connecting strip electrically connecting the plurality of first electrodes; and an insulative member between the back surface and the first connecting strip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Chinese Patent Application Numbers 201110140708.3, 201120175836.7, 201120176094.X, 201110141250.3, 201110141621.8, 201110141259.4, 201110141575.1, and 201110141248.6, filed May 27, 2011, which are incorporated by reference herein in their entirety. This application also claims priority to Chinese Patent Application No. 201130065596.0, filed Apr. 2, 2011, which is hereby incorporated by reference in its entirety. This application is also related to U.S. patent application Ser. No. 13/193,433 entitled “Light to Current Converter Devices and Methods of Manufacturing the Same” and U.S. patent application Ser. No. 13/193,458 entitled “Methods of Manufacturing Light to Current Converter Devices”, which are incorporated by reference herein in its entirety.

BACKGROUND

Provided herein are solar cell modules and methods of manufacturing the same, and, more particularly, back contact solar cell modules and methods of manufacturing the same.

In a back contact solar cell, also known as back electrodes solar cell, the positive electrodes and the negative electrodes are located on a same back surface of the cell body. Compared to the traditional silicon solar cell, the back contact solar cell has no bus bars on the front surface of the cell body to block the light. Thus, the area absorbing the lights is enlarged, helping to increase the efficiency of the solar cell. Furthermore, since both the positive electrodes and the negative electrodes are formed on the same back surface, the manufacturing process can be simplified. The removal of the bus bar from the front surface of the cell body also improves the appearance of the solar cell. As a result, back contact solar cell has becoming more and more popular, and has been gradually gaining acceptance by the solar industry.

During the manufacturing process of a back contact solar cell, it is necessary to electrically connect the adjacent solar cells. If the back surface forms a positive electric field, the array of the negative electrodes on the back surface need be connected by a negative connecting strip, but it often leads to a short circuit between the positive electric field on the back surface and the negative connecting strip. If the back surface forms a negative electric field, the array of the positive electrodes on the back surface need be connected by a positive connecting strip, but it often leads to a short circuit between the negative electric field on the back surface and the positive connecting strip. Thus, a solution is needed to avoid short circuit during the connecting of adjacent solar cells in a back contact solar cell module.

BRIEF SUMMARY

The embodiments of the present invention provide back contact solar cell modules in which a first connecting strip connecting the first electrodes on the back surface is insulated from the electric field formed on the back surface that is of opposite polarity from the first electrodes.

The embodiments of the present invention also provides method of making back contact solar cell modules comprising insulating a first connecting strip connecting the first electrodes on the back surface from the electric field formed on the back surface that is of opposite polarity from the first electrodes.

In accordance with one embodiment, a solar cell module comprise a solar cell comprising a back surface with a plurality of first electrodes and a plurality of second electrodes formed thereon, the plurality of first electrodes and the plurality of second electrodes being of opposite polarities, the back surface being configured to form an electric field thereon of the opposite polarity as the plurality of first electrodes; a first connecting strip electrically connecting the plurality of first electrodes; and an insulative member between the back surface and the first connecting strip.

In accordance with another embodiment, the insulative member is an insulative strip separable from the back surface of the solar cell.

In accordance with another embodiment, the insulative strip comprises a material selected from the group consisting of expandable polyethylene (EPE), thermoplastic elastomer (TPE), polyvinyl fluoride composite membrane (TPT), and silicon.

In accordance with another embodiment, the insulative strip comprises a plurality of through holes through which the first connecting strip is connected to the plurality of first electrodes.

In accordance with another embodiment, an end of the insulative strip extends beyond an edge of the back surface.

In accordance with another embodiment, the insulative member comprises an insulative material adhered to the back surface.

In accordance with another embodiment, the insulative material comprises silicone.

In accordance with another embodiment, the first connecting strip comprises a base strip and a plurality of projections projecting from a surface on which the base strip resides.

In accordance with another embodiment, the plurality of projections correspond to the plurality of first electrodes, and each projection projects into a through hole to electrically connect to a corresponding first electrodes.

In accordance with another embodiment, the plurality of first electrodes protrude out of the back surface.

In accordance with another embodiment, the solar cell module further comprises a second connecting strip electrically connecting the plurality of second electrodes.

In accordance with another embodiment, the solar cell module further comprises a connection member electrically connecting the second connecting strip.

In accordance with another embodiment, the plurality of first electrodes are rectangle-shaped.

In accordance with another embodiment, a solar cell module comprises a first solar cell and a second solar cell adjacent to the first solar solar, each of the first solar cell and the second solar cell comprising a front surface configured to be exposed to light and a back surface with a plurality of first electrodes and a plurality of second electrodes formed thereon, the plurality of first electrodes and the plurality of second electrodes being of opposite polarities, the back surface being configured to form an electric field thereon of the opposite polarity as the plurality of first electrodes; a first connecting strip electrically connecting the plurality of first electrodes; a second connecting strip electrically connecting the plurality of second electrodes; and an insulative member between the back surface and the first connecting strip; and a connection member electrically connecting the second connecting strip of the first solar cell and the first connecting strip of the second solar cell.

In accordance with another embodiment, the insulative strip comprises a plurality of through holes corresponding to the plurality of first electrodes, and the first connecting strip comprises a plurality of projections for projecting into the plurality of through holes to electrically connect to the plurality of first electrodes.

In accordance with another embodiment, the connection member is located on the back surface of the first solar cell and connected to the second connecting strip of the first solar cell.

In accordance with another embodiment, the connection member is located on the back surface of the second solar cell and connected to the first connecting strip of the second solar cell.

In accordance with another embodiment, the solar cell module further comprises a second insulative member between the connection member and the back surface of the second solar cell.

In accordance with another embodiment, a method of manufacturing a solar cell module comprises forming a first solar cell and a second solar cell adjacent to the first solar solar, each of the first solar cell and the second solar cell comprising a front surface configured to be exposed to light and a back surface with a plurality of first electrodes and a plurality of second electrodes formed thereon, the plurality of first electrodes and the plurality of second electrodes being of opposite polarities, the back surface being configured to form an electric field thereon of the opposite polarity as the plurality of first electrodes; connecting the plurality of second electrodes electrically through a second connecting strip in each of the first solar cell and the second solar cell; forming an insulative member around the plurality of first electrodes in each of the first solar cell and the second solar cell; connecting the plurality of first electrodes electrically through a first connecting strip in each of the first solar cell and the second solar cell, wherein said insulative member is located said first strip and the back surface in each of the first solar cell the second solar cell; and connecting the second connecting strip of the first solar cell and the first connecting strip of the second solar cell electrically through a connection member.

In accordance with another embodiment, the method of manufacturing a solar cell module further comprises forming a plurality of projections on the first connecting strip corresponding to the plurality of first electrodes; and connecting each of the plurality of projections on the first connecting strip with a corresponding first electrode electrically.

In accordance with another embodiment, forming the insulative member comprises depositing an insulative material on the back surface where the first connecting strip is located and the plurality of first electrodes are not located.

In accordance with another embodiment, forming the insulative member comprise providing an insulative strip on the back surface where the first connecting strip is located, the insulative strip comprises a plurality of through holes corresponding to the plurality of first electrodes.

DETAILED DESCRIPTION

As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly indicates otherwise. Additionally, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, alone or in combination with other elements, components, or steps that are not expressly referenced.

Exemplary embodiments of solar cell modules will now be discussed with reference toFIGS. 1-9. Metallization Wrap Through (“MWT”) back contact solar cells are used in such exemplary embodiments. However, the applications of the present invention is not limited to MWT back contact solar cells, but can be extended to other type of solar cells, such as Metallization Wrap Around (“MWA”) or Emitter Wrap Through (“EWT”) solar cells.

A solar cell module can be formed by electrically connecting an array of solar cells in series with each other, and packaging them into an enclosure. The solar cell module can be used to absorb sun light, and convert the sun light into electricity.FIG. 1illustrates the back surface11of an exemplary solar cell10in accordance with the MWT technology. A solar cell typically comprises two or more semiconductor plates. The semiconductor typically used in solar cell is silicon, including mono-crystalline silicon, polycrystalline silicon and amorphous silicon. When light impinges upon the front surface of a solar cell, electrical charges will be accumulated on the two sides of the cell to create a voltage. This is the photovoltaic effect, which generates an electromotive force on the two sides of the solar cell converting light into electricity. For a MWT solar cell, the front surface of the cell (not shown) typically contains a plurality arrays of metal bus bars (not shown) to collect the electric current generated by the impinging light. The back surface11has a plurality of positive electrodes111and a plurality of negative electrodes112. Since the a positive electric field will be generated on the back surface11printed with an aluminium paste, the negative electrodes112must be insulated from the positive electric field and the positive electrodes111. For example, as shown inFIG. 1, an insulative area around the negative electrode112may be formed to prevent an electrical connection between the negative electrode112and the positive electric field. The insulative area can formed by laser etching, or other methods. The negative electrodes112are connected to the metal bus bars on the front surface through via holes (not shown) in the solar cell. The via holes can be obtained by laser drilling, and an metal layer can be formed on the inner surface of the via holes for electrically connecting the metal bus bars of the front surface and the negative electrodes112of the back surface so that the current from the metal bus bars can be transferred to the negative electrodes on the back surface. The MWT technology is known in the art, and had been disclosed in various prior art, such as EP0985233B1.

As shown inFIG. 1, the back surface of the solar cell in this exemplary embodiment has a plurality of arrays of positive electrodes111and negative electrodes112, each array of electrodes has at least two electrodes111/112. The electrodes111/112are of rectangle shape. Of course, in other embodiments, the shape, number, and pattern of the electrodes can be varied depending on the requirement of particular application.

As shown inFIGS. 2-7, the solar cell module also includes several positive connecting strips31for electrically connecting an array of positive electrodes111, several negative connecting strips32for electrically connecting an array of negative electrodes112, several insulative members20between the negative connecting strips32and the back surface11of the solar cell10, and a connecting member33for electrically connecting with an adjacent solar cell.

As shown inFIG. 2, in an exemplary embodiment, the insulative member20is an insulative strip that is separable from the back surface11of the solar cell10. The insulative member20is made of an insulative material, such as expandable polyethylene (EPE), thermoplastic elastomer (TPE), polyvinyl fluoride composite membrane (TPT), or silicon. The insulative strip20is of rectangle shape, and has a main body21with a plurality of rectangle shaped holes22corresponding to the negative electrodes112. The distance between two adjacent holes22is substantially equal to the distance between two adjacent negative electrodes112. In another embodiment, the distance between two adjacent holes22is slightly larger than the distance between two adjacent negative electrodes112; but all the negative electrodes112can go through the holes22, and the size of the negative electrodes112is slightly smaller than the size of the holes22. In another embodiment, the shape of the holes22can be different from the shape of the negative electrodes112. For example, the holes22can be round, but the holes are bigger enough to allow the negative electrodes112to go through. In yet another embodiment, the insulative member20is an insulative layer adhered to the back surface11, such as silica gel painted to the area around the negative electrodes112so that the negative connecting strips32can be electrically isolated from the back surface11of the solar cell10.

In one embodiment, the positive connecting strips31and the negative connecting strips32are welding strips30. As shown inFIG. 4, the welding strip30has a longitudinal base301and a plurality of projections302projecting from the longitudinal base301. The number of projections302on each positive connecting strip31and negative connecting strip32is the same as the number of negative electrodes112and positive electrodes111in each array of negative electrodes112and positive electrodes111, and the distance between two adjacent projections302is the same as the distance between two adjacent negative electrodes112and two adjacent positive electrodes111. When the welding strip30is welded to the back surface11of the solar cell, the projections302electrically connect to the negative electrodes112on the back surface11through the through holes22of the insulative member20. The projections302can be an integral part of the base301, and be formed by bending or stamping. The projections302can also be formed by attaching something to the surface of the base301, such as by welding. In one embodiment, the width of the welding strip30is roughly the same as the width of the negative electrodes112, and the base301is bended to form the projections302for easy assembly. In one embodiment, there is no insulative member20between the positive connecting strip31and the back surface11. Thus, it is not necessary to form the projections302, and the positive connecting strip31is not bended. In another embodiment, the positive connecting strip31is replaced by a longitudinal positive electrode. In yet another embodiment, the array of negative electrodes112forms a longitudinal unitary negative electrode, and the through hole22on the insulative strip20is also a longitudinal through hole corresponding to the longitudinal unitary negative electrode, and the base301only needs one longitudinal projection302corresponding to the longitudinal unitary negative electrode. In one embodiment, the connecting member33is a metal strip which electrically connects the negative connecting strip32of one solar cell with the positive connecting strip31of an adjacent solar cell.

As show inFIGS. 3,5,6,7, the insulative strip20is first put onto the back surface11of the solar cell11, with the through holes22over the negative electrodes112. One end25of the insulative strip20extends over the the edge115of the back surface11, and may extend to the back surface of an adjacent solar cell, as illustrated inFIG. 7. Then, the negative connecting strip32is mounted onto the back surface11, with the projections302welding to the negative electrodes112through the through holes22. The insulative strip20is located between the negative connecting strip32and the back surface11, and prevents contact between the negative connecting strip32and the back surface11on all directions. Thus the insulative strip20can ensure good insulation between the negative connecting strip32and the back surface11on all directions and avoid short circuit. Afterwards, the positive connecting strip31is mounted onto the back surface11, with the projections302connecting to the positive electrodes111. In another embodiment, the positive connection strip31can be mounted before the negative connection strip32. In yet another embodiment, the insulative strip20can be assembled with the negative connecting strip32first, then jointly mounted onto the back surface11.

FIGS. 6 and 7illustrates the connection between two adjacent solar cells. A typical solar cell module often includes dozens or more inter-connected solar cells. By way of example, in the following exemplary embodiments, only the connection between two adjacent solar cells will be described. In one embodiment, the solar cell module includes a first solar cell101and a second solar cell102. The connecting member33connects to all the positive connecting strips311on the back surface11of the first solar cell101, then electrically connects to the negative connecting strips322extending from the back surface of the second solar cell102. As a result, the first solar cell101and the second solar cell102are electrically connected. Since the connecting member33is connected to all the positive connecting strips311on the back surface11of the first solar cell101, there is no need to insulate the connecting member33from the back surface of the first solar cell101. In another embodiment as shown inFIG. 9, the connecting member33can also be connected to the negative connecting strip322of the second solar cell102first, then then connects to the positive connecting strips311on the back surface of the first solar cell101. In this embodiment, an additional insulative strip29is needed to isolate the connecting member33from the back surface11of the second solar cell102. In one embodiment, the insulative strip29can be installed the same way as insulative strip20. Furthermore, the connecting member33can be located either on the back surface of the first solar cell101, or on the back surface of the second solar cell202. When one end25of the insulative strip20extends beyond the edge115of the second solar cell102and reaches to the back surface of the first solar cell11, the negative connecting strip322will be obscured by insulative strip20, and not visible from the front surface of the solar cell. This improves the appearance of the solar cell module.

FIG. 8shows a sectional view of a solar cell module that has been been laminated and packaged. There is a back plate40under the back surface of the solar cell10for protecting the solar cell module100. The back plate40can be made of polyvinyl fluoride composite membrane (TPT). On the top of the front surface of the solar cell module100is a glass layer, typically made of tempered glass. The solar cell10, insulative strip20and the welding strip30are all located between the glass layer and the back plate40. There is adhesive on both the top and bottom sides of the solar cell10. The adhesive can be made of materials such as ethylene-vinyl acetate (EVA) and has some flexibility. The adhesive wraps around the solar cell10, and makes the solar cell10, the glass layer and the back plate40one unitary module.

In embodiments mentioned above, all the solar cells are of n+/p type having N-type silicon on the front surface of the cell and P-type silicon on the back surface of the cell. This type of solar cell forms a negative electric field on the front surface, and a positive electric field on the back surface, so the negative electrodes on the back surface must be insulated from the positive electric field on the back surface. For p+/n type solar cell, the front surface has P-type silicon, while the back surface has N-type silicon, so the p+/n type solar cell forms a positive electric field on the front surface and a negative electric field on the back surface. The application of the resent invention is not limited to p+/n type solar cell, but can also be extended to n+/p type solar cell. In such embodiments, the positive electrodes (the first electrodes) and the positive connecting strips (the first connecting strips) on the back surface must be insulated from the negative electric field on the back surface. More generally, we define a first electrode having the opposite polarity with the electric field on the back surface, and a second electrode having the opposite polarity with the first electrode. We also define a first connecting strip for connecting with the first electrodes and a second connection strip for connection with the second electrodes.

In sum, the embodiments of the present invention provide an insulative strip20between the first connecting strip and the back surface of the solar cell prevent short circuit. This is important for the large-scale industry use of the back contact solar cell modules.

The embodiments of the present invention may be used to electrically connecting light to current converter devices, such as solar cells. The light to current converter devices may include via holes extending through the cell substrate and may include through-hole electrodes disposed within the via holes. The through-hole electrodes may be made from one or more materials and may be hollow, partially hollow, or fully filled. Front electrodes and rear electrodes may also be formed on the device and can be made of the same or different materials as the through-hole electrode. The devices may further include emitters located only on the top surface of the cell, located on the top surface and symmetrically along a portion of the inner surface of the via holes, located on the top surface and asymmetrically along a portion of the inner surface of the via holes, or located on the top surface and full inner surface of the via holes. Processes for making the described light to current converter devices are also disclosed.

FIGS. 10-13illustrate exemplary P-N junctions that may be used in a light to current converter device, such as a solar cell. The exemplary P-N junctions shown inFIGS. 10-13do not include a deposited dielectric layer or an emitter located on the back surface of the substrate. The absence of a back side emitter allows a device having a P-N junction like that shown inFIGS. 10-13to be manufactured without performing double side diffusion or back contact isolation. Additionally, the absence of a deposited dielectric layer allows the device to be manufactured without performing dielectric layer deposition and removal as is required to manufacture conventional P-N junctions. As a result, a device having a P-N junction similar or identical to those shown inFIGS. 10-13may be cheaper and quicker to manufacture than those having a conventional P-N junction.

Specifically,FIG. 10illustrates an exemplary P-N junction having an emitter2that covers the front surface of the substrate1and the full inner surface of the via hole3. The substrate1may include monocrystalline silicon or polycrystalline silicon having a first doping type (e.g., P or N) while the emitter2may have an opposite doping type (e.g., N or P). In this example, since the emitter2may not cover the backside of substrate1, the backside of substrate1may remain the same doping type as substrate1. In other examples, other types of opposite conductivity type semiconductors may be used for substrate1and emitter2.

FIG. 11illustrates another exemplary P-N junction having an emitter2that covers the front surface of the substrate1and symmetrically covers a portion of the inner surface of the via hole3. The substrate1may include monocrystalline silicon or polycrystalline silicon having a first doping type (e.g., P or N) while the emitter2may have an opposite doping type (e.g., N or P). In this example, since the emitter2may not cover a portion of the inner surface of via hole3and the backside of substrate1, the uncovered portion of the inner surface of via hole3and the backside of substrate1may remain the same doping type as substrate1.

FIG. 12illustrates yet another exemplary P-N junction having an emitter2that covers the front surface of the substrate1and and asymmetrically covers a portion of the inner surface of the via hole3. The substrate1may include monocrystalline silicon or polycrystalline silicon having a first doping type (e.g., P or N) while the emitter2may have an opposite doping type (e.g., N or P). In this example, since the emitter2may not cover a portion of the inner surface of via hole3and the backside of substrate1, the uncovered portion of the inner surface of via hole3and the backside of substrate1may remain the same doping type as substrate1.

FIG. 13illustrates yet another exemplary P-N junction having an emitter2that covers only the front surface of the substrate1. The substrate1may include monocrystalline silicon or polycrystalline silicon having a first doping type (e.g., P or N) while the emitter2may have an opposite doping type (e.g., N or P). In this example, since the emitter2may not cover the inner surface of via hole3and the backside of substrate1, the the inner surface of via hole3and the backside of substrate1may remain the same doping type as substrate1.

Various embodiments of light to current converter devices having exemplary P-N junctions similar or identical to those shown inFIGS. 10-13are described below with respect toFIGS. 14-19.

FIG. 14illustrates an exemplary light to current converter device140having a P-N junction similar to that shown inFIG. 10. Specifically, device140includes a P-type or N-type semiconductor substrate1with one or more via holes3(e.g., 9, 13, 20, 25, 40, 48, 60, or 80 via holes3) penetrating the substrate1. An N-type (for P-type substrate1) or P-type (for N-type substrate1) emitter2may be formed on the front surface of the substrate1and the full inner surface of the via hole3.

Device140may further include front electrodes5and one or more anti-reflective films4, for example, one or more layers of SiN, SiO2/SiN, Si3N4, TiO2, SiNx, or the like. The one or more anti-reflective films4may be used to absorb additional light and improve light conversion efficiency. A via front collector10(electrode) may also be placed on a portion of emitter2and above via hole3. Via hole3may be at least partially filled with a via hole electrode9that is electrically coupled to via front collector10and a via rear collector8(electrode) that may be disposed below via hole3. Via front collector10, via hole electrode9(electrode), and via rear collector8may collectively be referred to herein as a “through-hole electrode.” Device140may further include rear electrodes7(or back electrodes) disposed below substrate1. Front electrodes5, via front collector10, inner via hole electrode9, via rear collector8, and rear electrodes7may be made of any conductive material, such as metals, alloys, conductive pastes, conductive compounds, conductive films, or the like. In some examples, commercially available conductive pastes that are suitable for forming electrodes in a solar cell may be used. For example, DuPont Microcircuit Materials of the United States offers several types of silver-based DuPont Solamet photovoltaic metallization pastes, including Solamet PV17A, PV16x, PVD2A, PV173, PV502, PV505, PV506, and PV701, as described by the website at http://www2.dupont.com/Photovoltaics/en_US/assets/downloads/pdf/PV_SolametProductOverview.pdf of Dupont. Targray Technology International Inc. of Canada also offers many types of the HeraSol Ag Paste compositions, including SOL953, SOL953, SOL90235H, SOL9273M, SOL9318, SOL230, CL80-9381M, CL80-9383M, SOL108, and SOL9400, as described by the website at http://www.targray.com/solar/crystalline-cell-materials/silver-paste.php of Targray. Furthermore, some suppliers can customize their pastes to the specific manufacturing process to increase efficiency and provide wider processing windows. While specific pastes have been provided above, it should be appreciated that other known pastes may be used.

Additionally, front electrodes5, via front collector10, inner via hole electrode9, via rear collector8, and rear electrodes7may be made from the same or different materials, and may each be made of one or more materials. For instance, in some examples, front electrodes5, via front collector10, inner via hole electrode9, and via rear collector8may be made of silver, while the rear electrodes7may be made of aluminum, or vice versa. In other examples, front electrodes5, via front collector10, inner via hole electrode9, and via rear collector8may be made of aluminum, while the rear electrodes7may be made of silver. Moreover, the via front collector10, the inner via hole electrode9, and the via rear collector8can be hollow, partially filled, or fully filled, and may form a unitary body or may form multiple segments. In the example shown inFIG. 8, the via front collector10, the inner via hole electrode9, and the via rear collector8are fully filled.

Front electrodes5, via front collector10, inner via hole electrode9, and the via rear collector8may be coupled together such that during operation, electric current may be generated by the light receiving surface of device140and directed to via front collector10by front electrodes5. From via front collector10, the current may be directed through via hole electrode9to via rear collector8. Rear electrodes7may be electrically isolated from via rear collector8and may collect opposite conductivity current on the back surface of device140. In this way, electrodes of opposite conductivity may be placed on the same side (back surface) of device140without interfering with light absorption on the front surface of the device.

Device140may further include impurity layer6. In some examples, an N+(for N-type substrate1) or P+(for P-type substrate1) impurity layer6may be positioned on the bottom of substrate1to form a back surface field. In other examples, impurity layer6may include an N+(for N-type substrate1) doping region, P+(for P-type substrate1) doping region, SiNx, SiO2, or combinations thereof. Device140may further include light-trapping structures on the light-receiving surface of the device. In some examples, the surface may be textured with a random arrangement of pyramids, inversed pyramids, honeycomb structures, and the like. Using these structures, a ray of light may be reflected toward a neighboring structure resulting in a greater amount of light absorption. To further improve the absorption of light, the light-trapping surface may be optically dark or black.

FIG. 15illustrates another exemplary light to current converter device150having a P-N junction similar to that shown inFIG. 11. Device150may be similar to device140, except that the emitter2may symmetrically cover only a portion of the inner surface of the via hole3.

FIG. 16illustrates an exemplary light to current converter device160having a P-N junction similar to that shown inFIG. 13. Device160may be similar to device140, except that the emitter2only covers the front surface of substrate1and does not cover the inner surface of the via hole3.

FIG. 17illustrates an exemplary light to current converter device170having a P-N junction similar to that shown inFIG. 13. Device170may be similar to device160except that via front collector10, via hole electrode9, and via rear collector8may be hollow. Additionally, front electrodes5, via front collector10, via hole electrode9, and via rear collector8may be made from the same material and may form a unitary body. In some examples, front electrodes5, via front collector10, inner via hole electrode9, and via rear collector8may be made of silver, while the rear electrodes7may be made of aluminum. In other examples, front electrodes5, via front collector10, inner via hole electrode9, and via rear collector8may be made of aluminum, while the rear electrodes7may be made of silver.

FIG. 18illustrates another exemplary light to current converter device180having a P-N junction similar to that shown inFIG. 13. Device180may be similar to device160except that via front collector10and via rear collector8may be fully filled while via hole electrode9may be hollow. Additionally, front electrodes5may be made from a first material, via front collector10and via rear collector8may be made from a second material, and via hole electrode9may be made from a third material.

FIG. 19illustrates another exemplary light to current converter device190having a P-N junction similar to that shown inFIG. 12. Device190may be similar to device140, except that the emitter2asymmetrically covers only a portion of the inner surface of the via hole3.

It should be appreciated by one or ordinary skill that any one of the P-N junctions shown inFIGS. 10-13may be used to make light to current converter devices having any combination of materials for front electrodes5, rear electrodes7, via hole electrode9, via front collector10, and via rear collector8, and having a hole through all, a portion, or none of via hole electrode9, via front collector10, and via rear collector8.

Although embodiments have been described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the various embodiments as defined by the appended claims.