Solar Cell Assembly

Abstract

1. A solar cell assembly (100) comprising: a layered structure (102) including a photovoltaic element and a conductive surface (111); and an electrode assembly (101) including a plurality of longitudinally extending and laterally spaced apart conductive elements (104a-104f), the plurality of conductive elements including a first conductive element (104b) having a first cross-sectional area and a second conductive element (104a) having a second cross-sectional area greater than the first cross-sectional area, the electrode assembly being disposed on the conductive surface of the layered structure such that the conductive elements are in ohmic contact with the conductive surface.

Description

[Technical field]

[0001] The present disclosure relates to an electrode assembly for a solar cell and to a solar cell having an electrode assembly. [Background technology]

[0002] Solar modules for providing electrical energy from sunlight typically include an array of solar cells, each having a semiconductor substrate. The solar cells are traditionally electrically connected via a number of finger electrodes on the front and rear faces of each cell to a series of wide, vertical busbar electrodes printed on the front and rear sides of the cells. From the busbar electrodes, the current flows along a series of copper ribbons, each of which is soldered to a respective busbar electrode, to a junction box.

[0003] A general objective for solar cell development is to achieve high conversion efficiency balanced with the need for reduced production costs. Efforts to achieve this have focused on the electrode connections between the solar cells in the solar cell module and the properties of the semiconductor substrate.

[0004] For example, configurations are known having a foil wire (electrode) assembly in which the busbar is replaced by multiple wires arranged on a film (or foil). The busbar is typically rectangular in cross section (with the longer dimension parallel to the front surface of the solar cell). On the other hand, the wires of the foil wire electrode assembly are typically circular in cross section. For the same cross-sectional area, a circular shape does not present as much shading to the light as a rectangular shape. Additionally, the circular geometry means that less incident light is reflected directly from the solar cell. Thus, replacing the busbar with multiple wires can reduce optical losses resulting from shading caused by the presence of the busbar. While this can increase the conversion efficiency, there is a continuing need to further improve the efficiency of solar cells and maintain that improved efficiency over the operational life of those solar cells. Summary of the Invention

[0005] According to a first aspect, there is provided a solar cell assembly comprising: a layered structure having a photovoltaic element and a conductive surface (e.g., a conductive outer surface); A solar cell assembly is provided, comprising: an electrode assembly having a plurality of longitudinally extending and laterally spaced apart conductive elements, the plurality of conductive elements including a first conductive element having a first cross-sectional area and a second conductive element having a second cross-sectional area larger than the first cross-sectional area, the electrode assembly being disposed on a conductive surface of the layered structure such that the conductive elements are in ohmic contact with the conductive surface.

[0006] The conductive elements collect current from the layered structure (e.g., via finger electrodes disposed on the layered structure). In general, each conductive element collects current from an area of ​​the conductive surface that extends along both sides of the conductive element. The current drawn by a conductive element depends on the size of this area and whether this area is also supplied by another conductive element. Thus, for example, in an area defined between two conductive elements, roughly half of the current is drawn by each conductive element. On the other hand, in an area defined by a conductive element and the edge of the conductive surface, all of the current is drawn by the single outermost conductive element. For the same reason, the spacing of the conductive elements also influences the required current draw of each conductive element. For example, a larger spacing of the conductive elements means that each conductive element occupies a larger area, increasing the amount of current that needs to be drawn by each conductive element.

[0007] By providing at least two conductive elements of different cross-sectional areas, these differences in current draw can be accommodated. Thus, for example, the larger (second) conductive element may be positioned where more current is to be drawn. The smaller (first) conductive element may be positioned where less current draw by the conductive element is required. By arranging the conductive elements in this manner (i.e., to match the size of the conductive element to the current draw requirements), power losses can be minimized while at the same time light shading by the conductive element can be minimized. Thus, providing conductive elements of different cross-sectional areas facilitates the arrangement of the conductive elements to optimize the optoelectronic properties of the electrode assembly.

[0008] For the avoidance of doubt, the term "cross-sectional area" is used to denote the area of ​​a cross section of a conductive element in a plane perpendicular to the (longitudinal) extension of that conductive element.

[0009] The term "on" as used herein, for example in the phrase "on a surface", is intended to encompass both direct and indirect placement on an element, such as a layer, film, or region. Thus, the term "on a surface" encompasses configurations with one or more intervening layers, or alternatively, no intervening layers. In contrast, when an element is referred to as being "directly on" another element, no intervening elements are present. Thus, in a first aspect, the electrode assembly may be directly or indirectly placed on the conductive surface.

[0010] The terms "longitudinal" (defined by the orientation of the conductive elements) and "laterally" refer to directions that are substantially perpendicular to one another.

[0011] It is understood that the terms "conductive" and "insulating" as used herein are expressly intended to mean electrically conductive and electrically insulating, respectively. The meaning of these terms is particularly clear when considering the technical context of the present invention, i.e., the context of a photovoltaic solar cell device.

[0012] We now describe optional features of the first aspect, which may be applied alone or in any combination with any aspect.

[0013] As described above, the plurality of conductive elements may be configured such that the second conductive element draws more current from the conductive surface of the layered structure than the first conductive element. For example, the second conductive element may be an outermost conductive element of the plurality of conductive elements. The plurality of conductive elements may include two outermost conductive elements and a plurality of intermediate conductive elements disposed between the two outermost conductive elements. In some embodiments, the second conductive element may be an intermediate conductive element.

[0014] As mentioned above, the outermost conductive element of the plurality of conductive elements may in some cases function (i.e., draw current from) a larger area than the intermediate conductive elements (i.e., when the outermost conductive element is located away from the edge of the conductive surface by a distance greater than half the spacing between the plurality of conductive elements). This is because all of the current drawn in the region between the outermost conductive element and the adjacent edge of the conductive surface must pass through the outermost conductive element (whereas in the region between two adjacent conductive elements, only half of the current passes through each conductive element). Increasing the cross-sectional area of ​​the outermost conductive element means that it can better accommodate this larger current, which can help minimize power losses (resulting from the smaller size of the conductive elements).

[0015] The second conductive element may have a larger effective served area than the first conductive element. For the intermediate conductive element, the effective served area may be determined by summing half of the first area and half of the second area. The first area may be defined as the area between the intermediate conductive element and the first adjacent conductive element, and the second area may be defined as the area between the intermediate conductive element and the second adjacent conductive element. For the outermost conductive element, the effective served area may be determined by summing half of the third area and the fourth area. The third area may be defined as the area between the outermost conductive element and the adjacent conductive element, and the fourth area may be defined as the area between the outermost conductive element and the adjacent edge of the layered structure.

[0016] For the avoidance of doubt, the first, second, third and fourth areas are areas of the surface (i.e., conductive surface) of the layered structure on which the electrode assembly is disposed. Furthermore, references to an area at least partially defined by a wire (e.g., between two wires or between a wire and an end) are references to an area extending to the central axis of the wire.

[0017] For the avoidance of doubt, as used herein, the term "adjacent" does not mean "directly adjacent" or "contacting." For example, the term "adjacent conductive element" is used herein to describe the laterally closest conductive element (or one of the two closest conductive elements). Similarly, the term "adjacent end" is used herein to describe the nearest longitudinally extending end (i.e., laterally closest).

[0018] A further advantage of providing larger outermost conductive elements is that the conductive elements can be placed at a greater distance from the edge of the layered structure (e.g., the edge of the conductive surface) while at the same time accommodating increased current collection from a larger area on which the conductive elements function (due to the increased spacing). By providing this increased spacing from the edge of the layered structure (e.g., the conductive surface), there is a larger area at the edge of the layered structure (e.g., the conductive surface) that is free of conductive elements. This larger conductive element-free area can provide better adhesion, for example, between the film (if present) and the solar cell (because the increased size of this area provides a larger contact area between the film and the solar cell). Thus, if present, the film (and, consequently, the conductive elements) can be held more firmly on the solar cell.

[0019] More generally, using a larger conductive element (whether or not the conductive element is the outermost wire) can provide a larger contact area between the conductive element and the conductive surface, improving contact (and providing better adhesion) between the conductive element and the conductive surface.

[0020] The first conductive element may be an intermediate conductive element. Alternatively, the first conductive element may be an outermost conductive element. This may be desirable, for example, when the outermost conductive element is disposed at or near an edge of a conductive surface to provide a smaller area for utilization than the intermediate conductive elements. The first conductive element may be adjacent to the second conductive element.

[0021] The plurality of conductive elements may include a third conductive element, and the third conductive element may have a third cross-sectional area. The third cross-sectional area may be greater than the first cross-sectional area. The third cross-sectional area may be the same as the second cross-sectional area. Thus, the second and third conductive elements may have the same cross-sectional area. The third conductive element may be an outermost conductive element of the plurality of conductive elements (i.e., the second and third conductive elements may define the two outermost conductive elements of the plurality of conductive elements).

[0022] Thus, two outermost conductive elements (e.g., the second and third conductive elements) of the plurality of conductive elements may each have a larger cross-sectional area than at least one intermediate conductive element (e.g., the first conductive element). Two outermost conductive elements of the plurality of conductive elements may each have a larger cross-sectional area than the plurality of intermediate conductive elements. In some embodiments, two outermost conductive elements of the plurality of conductive elements may each have a larger cross-sectional area than each of the intermediate conductive elements (i.e., the outermost conductive elements may be larger than all of the intermediate conductive elements).

[0023] In some embodiments, all (or substantially all) of the intermediate conductive elements may have the same cross-sectional area (eg, a first cross-sectional area).

[0024] The plurality of conductive elements may be evenly spaced (i.e., equally spaced apart). That is, there may be a constant spacing between each adjacent pair of conductive elements in the plurality of conductive elements. The plurality of conductive elements may alternatively be unevenly spaced. That is, the lateral spacing between at least one pair of adjacent conductive elements may be greater than the lateral spacing between another pair of adjacent conductive elements. When a first pair of conductive elements has a greater spacing between the conductive elements than a second pair of conductive elements (of the plurality of conductive elements), the first pair of conductive elements may include the second conductive element and the second pair of conductive elements may include the first conductive element.

[0025] The conductive elements may be substantially parallel to one another.

[0026] The shape of the conductive elements (in addition to their cross-sectional area as explained above) may be selected to optimize the optoelectronic properties of the electrode assembly, ie, their current collecting and light blocking properties.

[0027] Each conductive element may have a circular cross-sectional shape, i.e., a shape across the axial length of the conductive element. Alternatively, each conductive element may have a different transverse cross-sectional shape, for example having a rectangular or triangular shape. Alternatively, each conductive element may have an elliptical, oval (i.e., racecourse shaped), or irregular transverse cross-sectional shape.

[0028] Each conductive element may comprise a conductive metal or metal alloy. Each of the conductive elements may be coated with an alloy coating, comprising an alloy having a low melting point, i.e. a melting point lower than the melting point of the conductive metal / metal alloy forming the core of the conductive element. Each conductive element may be completely coated with the alloy coating or may be at least partially coated on one or more sides facing the layered structure of the solar cell (if disposed on the layered structure).

[0029] Each conductive element may have a substantially constant cross-sectional area along the length of the conductive element. Each conductive element may have a substantially constant cross-sectional shape along the length of the conductive element.

[0030] The first conductive element and / or each intermediate conductive element may have a first diameter. The first diameter may be between 200 μm and 300 μm, or such as between 225 μm and 275 μm, or about 250 μm. The first cross-sectional area may be greater than or equal to 0.03 mm. 2 ~0.07mm 2 , or for example 0.04 mm 2 ~0.06mm 2 , or about 0.05 mm 2 may be also.

[0031] The second conductive element and / or the third conductive element may have a second diameter. The second diameter may be between 250 μm and 350 μm, or such as between 275 μm and 325 μm, or about 300 μm. The second cross-sectional area may be less than 0.05 mm. 2 ~0.10mm 2 , or for example 0.06 mm 2 ~0.08mm 2 , or about 0.07 mm 2 may be also.

[0032] The second diameter may be between 30 μm and 70 μm larger than the first diameter. The second diameter may be approximately 50 μm larger than the first diameter.

[0033] The second cross-sectional area is 0.01 mm smaller than the first cross-sectional area. 2 ~0.03mm 2 The second cross-sectional area may be approximately 0.02 mm larger than the first cross-sectional area. 2 It can be big.

[0034] The second cross-sectional area may be between 30% and 60% larger than the first cross-sectional area. The second cross-sectional area may be approximately 45% larger than the first cross-sectional area.

[0035] The first distance may be defined between two adjacent conductive elements (e.g., a first conductive element and an adjacent conductive element) of the plurality of conductive elements. If the conductive elements are evenly spaced apart, the first distance may represent the (even) spacing between each of the conductive elements (i.e., each conductive element may be spaced apart from an adjacent conductive element by the first distance).

[0036] The first distance may be between 8 mm and 10 mm, or between 8.5 mm and 10 mm, or between 9 mm and 9.5 mm, or about 9.3 mm.

[0037] To avoid any uncertainty, references herein to distances and / or spacings between conductive elements and / or ends shall be construed as lateral distances / spacings (i.e. perpendicular to the axial extension of the conductive elements). Furthermore, (lateral) distances involving one or more conductive elements shall be measured from the central axis of the conductive elements. As an example, a reference to a distance between two adjacent conductive elements is the distance between the central axis of one conductive element and the central axis of the other adjacent conductive element. As a second example, a reference to a distance between a conductive element and an end (of a film or layered structure) is a reference to the lateral distance between the central axis of the conductive element and the end. As will be understood, in this second example, the central axis of the conductive element may be spaced apart (e.g. above) from the surface of the component (e.g. film or layered structure) of which the end forms a part. In such a case, it is emphasized that references to such distances are references to the lateral component of the distance between the central axis and the end (i.e. the distance shall be measured parallel to the surface).

[0038] The distance between an outermost conductive element of the plurality of conductive elements and an adjacent end of the layered structure (e.g., an end of the conductive surface) may be equal to or greater than the distance between two adjacent conductive elements of the plurality of conductive elements. In other words, the electrode assembly may be disposed on the conductive surface such that a second (lateral) distance is defined between an outermost conductive element of the plurality of conductive elements (e.g., a second conductive element) and an adjacent (longitudinal) end of the conductive surface of the layered structure on which the electrode assembly is disposed. The second distance may be equal to or greater than the first distance. That is, the outermost conductive element may be spaced from the adjacent end of the layered structure by a distance greater than the distance between two adjacent conductive elements of the plurality of conductive elements.

[0039] The first distance may be defined between an outermost conductive element (e.g., the second conductive element) that partially defines the second distance and a conductive element adjacent to the outermost conductive element (e.g., the first conductive element).

[0040] As already mentioned above, maximizing the distance of the conductive elements from the edge of the solar cell assembly is advantageous in that it provides a larger conductive element-free area for adhering a means (such as a film) for fixing the conductive elements to the solar cell assembly. The larger outermost conductive elements can enable such a distance by ensuring that there is sufficient capacity to draw charge (with minimal power loss) from the larger area resulting from such a distance.

[0041] In other embodiments, the second distance may be less than the first distance (eg, approximately half the first distance).

[0042] A third (lateral) distance may be defined between the other of the two outermost conductive elements (e.g., the third conductive element) and an adjacent end of the layered structure (e.g., an adjacent end of the conductive surface). The third distance may be the same as the second distance. In this regard, the multiple conductive elements may be arranged on the layered structure such that the spacing between the opposing (longitudinally extending) ends of the layered structure and the adjacent outermost conductive elements is greater than the spacing between the conductive elements themselves.

[0043] The second and / or third distance may be between 10 mm and 13 mm, or between 11 mm and 12 mm, or between 11 mm and 11.5 mm, or about 11.25 mm.

[0044] The electrode assembly may have an insulating, light-transmitting film. The film may overlie the conductive elements (i.e., the conductive elements may be provided between the film and the conductive surface). The film (also referred to as a foil) may provide a means for maintaining the conductive elements in a spaced apart arrangement during attachment onto the conductive surface. The film may be configured to hold the electrode assembly on the surface of the layered structure (thereby maintaining ohmic contact between the conductive elements and the conductive surface). When the electrode assembly has such a film (and the conductive elements are in the form of wires), the electrode assembly may be referred to as a foil (or film) and wire assembly.

[0045] A distance between an outermost conductive element of the plurality of conductive elements and an adjacent edge of the film may be equal to or greater than a distance between two adjacent conductive elements of the plurality of conductive elements, i.e., the plurality of conductive elements may be arranged such that a fourth (lateral) distance, which is equal to or greater than the first distance, is defined between an outermost conductive element of the plurality of conductive elements (e.g., the second conductive element) and an adjacent (longitudinal) edge of the film.

[0046] A fifth (lateral) distance, greater than or equal to the first distance, may be defined between the other of the two outermost conductive elements (e.g., the third conductive element) and the adjacent edge of the film. The fifth distance may be the same as the fourth distance.

[0047] In this regard, the plurality of conductive elements may be arranged such that the spacing between opposing longitudinal ends of the film and the adjacent outermost conductive elements is greater than the spacing between the conductive elements.

[0048] The fourth and / or fifth distance may be between 10 mm and 13 mm, or between 11 mm and 12 mm, or between 11 mm and 11.5 mm, or about 11.25 mm.

[0049] Each of the first, second, third, fourth, and fifth distances may be measured along the same laterally extending axis.

[0050] As already mentioned above, maximizing the distance from the edge of the film to the conductive element is beneficial in that it provides a larger conductive element-free area for adhesion between the edge of the film and the solar cell (this may be achieved by varying the size of the conductive element).

[0051] As described above, the film may be configured to hold the conductive elements on the layered structure of the solar cell. The conductive elements may be attached (e.g., glued) to the film. The conductive elements may be partially embedded in the film such that a surface of each conductive element protrudes from a surface of the film. Alternatively, the conductive elements may be fully embedded in the film.

[0052] Each of the conductive elements may have an elongated shape, such as a wire or wire portion (although in other embodiments the conductive elements may be, for example, a bus bar). Each conductive element may be continuous (i.e., uninterrupted) and may extend across a majority of the film (e.g., substantially completely across). Each conductive element may extend substantially uninterrupted from one end of the film to an opposing end of the film. Each conductive element may extend beyond at least one of the ends of the film. In some embodiments, references herein to conductive elements may refer only to the portions of those conductive elements that are disposed on the surface of the layered structure.

[0053] The film may be rectangular. The film may have a long dimension and a short dimension. The conductive elements may extend in the direction of the short dimension (i.e., the longitudinal direction may be in the direction of the short dimension). Thus, in such an embodiment, the lateral direction may be in the direction of the long dimension. Alternatively, the conductive elements may extend in the direction of the long dimension and the lateral direction may be in the direction of the short dimension.

[0054] The film may comprise a polymeric material having high ductility, good insulating properties, optical transparency and thermal stability, resistance to shrinkage, etc. Exemplary polymeric materials may include acetates, epoxies, fluoroplastics, polyamides, polysulfones, rayon, polyolefins, plastyrene, rayonext, polyethylene terephthalate (PET), polyvinyl fluoride films, and modified ethylene tetrafluoroethylene.

[0055] The surface of the film (i.e., facing the conductive element) may be coated with a transparent sealing layer (e.g., an adhesive layer). The sealing layer may be configured to be in a non-adhesive state at room temperature and to transition to an adhesive state when heated (i.e., to a temperature above room temperature). Thus, during the manufacturing of the solar cell, the film may be heated such that the sealing layer softens to allow adhesion of the film to the conductive element due to the application of a force. In this way, the conductive element may be at least partially embedded in the sealing layer. Additionally or alternatively, the film (e.g., a portion or surface of the film configured to contact the solar cell) may be configured to be in a non-adhesive state at room temperature and to transition to an adhesive state when heated (i.e., to a temperature above room temperature). Thus, during the manufacturing of the solar cell, the film may be heated and softens to allow adhesion of the film to the conductive element due to the application of a force. In this way, the conductive element may be at least partially embedded in the film. In this embodiment, the sealing layer may not be present.

[0056] The conductive surface may have a plurality of finger electrodes (e.g., conductive elements / members). Each finger electrode may be elongated and may extend substantially laterally. The conductive elements (of the electrode assembly) may extend longitudinally across the plurality of finger electrodes. In this respect, the finger electrodes may be substantially perpendicular to the conductive elements.

[0057] The finger electrodes may comprise a printed conductive material, which may enable the formation of fine (i.e., narrow width and small depth) finger electrodes on the surface of the layered structure.

[0058] The finger electrodes may be substantially evenly distributed across the conductive surface. Thus, for example, the area between the outermost conductive element and the edge of the conductive surface may have the same number of finger electrodes as the area between two adjacent conductive elements. In other words, the conductive surface may be free of excess lines (extending from one or both of the opposing longitudinal edges of the conductive surface that are parallel to the conductive elements).

[0059] The presence of one or more larger outermost conductive elements can easily provide such an arrangement. Redundant lines are typically provided at the ends of the solar cell to reduce losses that occur, since the area at the ends is only utilized by one conductive element each. By making the outermost conductive elements larger, which have lower resistance, the redundant lines can be eliminated in some cases without compromising the efficiency of the solar cell assembly. This is because the lower power loss of the larger outermost conductive elements (resulting from the reduction in shading caused by the redundant lines) and the higher current in the outermost areas can offset any adverse effects of eliminating the redundant lines.

[0060] The layered structure may have a front surface (eg, a front-most surface) upon which light is incident during use, and a rear surface (eg, a rear-most surface) opposite the front surface.

[0061] The conductive surface may be the front surface (light-incident surface) of the layered structure. Thus, the electrode assembly may be disposed on the front surface of the layered structure (i.e., on the finger electrodes of the conductive surface), and the conductive elements may extend across the front surface of the layered structure (i.e., across the finger electrodes). Such an electrode assembly may be referred to as a front electrode assembly.

[0062] In other embodiments, the conductive surface may be a rear surface of the layered structure. Thus, the electrode assembly may be disposed on the rear surface of the layered structure, and the conductive elements may extend across the rear surface of the layered structure (i.e., over the finger electrodes of the conductive surface). Such an electrode assembly may be referred to as a rear electrode assembly.

[0063] A solar cell assembly may include both a front electrode assembly and a rear electrode assembly (and a layered structure may have both a front conductive surface and a rear conductive surface).

[0064] The layered structure may have multiple layers with photovoltaic elements. The photovoltaic elements may include a semiconductor material. Thus, the photovoltaic elements may be a semiconductor substrate. The semiconductor substrate may be formed of crystalline silicon (e.g., a monocrystalline silicon wafer). The substrate may be configured with a first conductivity type (e.g., n-type) and the layered structure may have a collector layer configured with a second conductivity type (e.g., p-type) that is opposite to the first conductivity type and thus forms a pn junction with the substrate. According to such a configuration, the collector layer may define a minority charge carrier collector layer (e.g., a hole collector layer) of the solar cell.

[0065] During the operation of a solar cell, multiple electron-hole pairs are generated by light incident on the substrate. If the substrate is n-type and the minority charge carrier collector layer is p-type (e.g., a hole collector layer), the separated holes and electrons migrate to the p-type hole collector layer and the n-type substrate, respectively. Thus, the holes act as majority charge carriers in the p-type hole collector layer, and the electrons act as majority charge carriers in the n-type substrate.

[0066] According to an alternative configuration, the substrate may be p-type and the minority charge carrier collector layer may be n-type (e.g., an electron collector layer), thus forming a p-n junction with the substrate, in which case the separated electrons and holes migrate to the n-type electron collector layer and the p-type substrate, respectively.

[0067] The collector layer may define a majority charge carrier collector layer configured with a first conductivity type (e.g., n-type) that is the same as the conductivity type of the substrate. For example, both the substrate and the majority charge carrier collector layer may be n-type, such that the majority charge carrier collector layer defines an electron collector layer. The majority charge carrier collector layer may thus be configured to selectively screen or draw charge carriers out of the substrate. Thus, when the solar cell is in use, electrons generated by light incident on the substrate are collected in the electron collector layer, and these electrons act as majority charge carriers.

[0068] The collector layer may be disposed on a first surface of the substrate. The layered structure of the solar cell may further include a second collector layer (e.g., a backfield layer) disposed on a second surface of the substrate opposite the first surface. The first and second surfaces may define a front surface and a back surface (or rear surface) of the substrate, respectively. The layered structure of the solar cell may further include a passivation layer disposed between the substrate and the respective first and second collector layers.

[0069] According to an exemplary configuration, the substrate may be formed from an n-type monocrystalline silicon wafer, which exhibits longer lifetime characteristics as compared to a p-type monocrystalline silicon wafer. The front collector layer may include an amorphous material (e.g., amorphous silicon) at least partially doped to be n-type. The back collector layer may include an amorphous material (e.g., amorphous silicon) at least partially doped to be p-type. In other embodiments, the back collector layer may be at least partially doped to be n-type and the front collector layer may be at least partially doped to be p-type.

[0070] Such configurations can contribute to the formation of heterojunction technology (HJT) type solar cells, which are defined as such because they combine two different materials to create a charge separating pn junction. Alternatively, the solar cell may have a multijunction (e.g., tandem) solar cell, which is defined as such because it has two or more charge separating junctions and two or more charge generating photon absorbing layers. Of course, the layered structure may be in other forms (e.g., the solar cell assembly need not be a heterojunction solar cell).

[0071] The electrode assembly may be positioned such that the collector layer is interposed between the electrode assembly and the substrate.

[0072] If the collector layer is disposed on the rear (e.g., rearmost) surface of the substrate, an electrode assembly may be disposed on the rear surface of the layered structure to define a rear electrode of the solar cell. If the collector layer is disposed on the front (e.g., frontmost) surface of the substrate, an electrode assembly may be disposed on the front surface of the layered structure to define a front electrode of the solar cell. The solar cell may have a front electrode assembly disposed on the front surface of the front layered structure and a back electrode assembly disposed on the back surface of the back layered structure.

[0073] The semiconductor substrate may include crystalline silicon (c-Si). If the semiconductor substrate is an n-type semiconductor, the semiconductor material may be configured to contain impurities of group V elements, such as phosphorus (P), arsenic (As), and antimony (Sb). If the semiconductor material is a p-type semiconductor material, the semiconductor material may contain impurities of group III elements, such as boron (B), gallium (Ga), and indium (In). Alternatively, the semiconductor material may be formed of a material other than silicon.

[0074] A surface of the layered structure, e.g., the front surface, may be textured to form a non-uniform surface or a surface having non-uniform properties, where the textured surface of the layered structure may increase the amount of light incident on the layered structure and thus improve the efficiency of the solar cell.

[0075] The layered structure may further include an anti-reflective layer or coating disposed on the front and / or rear surface of the layered structure. The anti-reflective layer may have a single layer structure or a multi-layer structure. The anti-reflective layer may be formed from silicon nitride (SiNx) and / or silicon oxide (SiOx). Alternatively, the anti-reflective layer may be formed from a transparent conductive oxide (TCO), such as indium tin oxide (ITO), textured to provide an anti-reflective surface. The anti-reflective layer can effectively reduce the reflectance of light incident on the solar cell and increase the selectivity of a given wavelength band, thereby increasing the efficiency of the solar cell.

[0076] In a second aspect, there is provided a solar module comprising a plurality of solar cell assemblies, each according to the first aspect. The solar cell assemblies may be electrically coupled to each other.

[0077] The plurality of solar cell assemblies may include a first and a second solar cell assembly, where the conductive wires of the first solar cell assembly are electrically coupled to the conductive elements of the second solar cell assembly, and the plurality of conductive elements may thus form an electrical connection between two or more solar cell assemblies within the solar module.

[0078] The plurality of conductive elements may include pairs of electrically coupled conductive elements, each pair having a first conductive element that forms part of the first solar cell assembly and a second conductive element that forms part of the second solar cell assembly. The first and second conductive elements may be electrically coupled to each other by a third conductive element (e.g., a copper ribbon) to allow electrical current to flow between the first and second conductive elements. The third conductive element may be substantially parallel or substantially perpendicular to the first and second conductive elements.

[0079] The first, second, and third conductive elements may be integrally formed to form a single integrally formed element (e.g., a wire). Configuring the conductive elements in this manner eliminates the need for separate connections (such as copper ribbons) between adjacent solar cells, thereby reducing the number and complexity of manufacturing steps required to fabricate a solar cell assembly.

[0080] Alternatively, the first and second conductive elements (and third conductive element, if present) may be formed separately but electrically coupled to one another.

[0081] The first conductive element may contact the conductive front surface of the layered structure of the first solar cell assembly, and the second conductive element may contact the conductive rear surface of the second solar cell assembly. Thus, when present, the third conductive element may extend from the front surface of the layered structure of the first solar cell assembly to the rear surface of the layered structure of the second solar cell assembly.

[0082] As described above, the electrode assembly of each solar cell assembly comprises films. The conductive elements are received between these films and the respective conductive surfaces of the corresponding solar assemblies. The films of one solar cell assembly may be separated from the films of another solar cell assembly. Thus, each first conductive element may be received between the first film and the front surface of the layered structure of the first solar cell assembly, and each second conductive element may be received between the second film and the rear surface of the layered structure of the second solar cell assembly. Each third conductive element may extend between the first film and the second film (i.e., it may not be attached / received by either the first or second film).

[0083] As will be appreciated, a second solar cell assembly may be bonded to a third solar cell assembly in a similar manner (i.e., the conductive elements extend from the conductive front surface of the layered structure of the second solar cell assembly to the conductive rear surface of the layered structure of the third solar cell assembly), and in this manner, a row or string of bonded solar cell assemblies may be formed.

[0084] In a third aspect, there is provided an electrode assembly for a solar cell, the electrode assembly comprising: an insulating light-transmitting film; An electrode assembly for a solar cell is provided, comprising: a plurality of longitudinally extending and laterally spaced apart conductive elements disposed on a surface of a film, the plurality of conductive elements including a first conductive element having a first cross-sectional area and a second conductive element having a second cross-sectional area larger than the first cross-sectional area.

[0085] The electrode assembly of the third embodiment may be the same as the electrode assembly described above in relation to the first embodiment (and may have one or more of the optional features of one or more of the first embodiment). Thus, the film may be as described above in relation to the first embodiment, and similarly, the plurality of conductive elements (including their configuration) may be as described above in relation to the first embodiment.

[0086] Those skilled in the art will appreciate that, unless mutually exclusive, a feature or parameter described in connection with any one of the above aspects may be applied to any other aspect. Further, unless mutually exclusive, any feature or parameter described herein may be applied to any aspect and / or may be combined with any other feature or parameter described herein. [Brief description of the drawings]

[0087] Embodiments will now be described, by way of example only, with reference to the drawings in which:

[0088] [Figure 1A] FIG. [Figure 1B] 1B is a cross-sectional side view of the solar cell of FIG. 1A. [Diagram 2] FIG. 1B is a schematic diagram illustrating the layered structure of the solar cell of FIG. 1A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0089] Aspects and embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which: Further aspects and embodiments will be apparent to those skilled in the art.

[0090] 1A and 1B show a solar cell assembly 100 having a front electrode assembly 101 and a rear electrode assembly 101′ disposed on the front and rear sides, respectively, of a photovoltaic element (not shown) and a layered structure 102 having a conductive front surface 111 and a conductive rear surface. For brevity, only the front electrode assembly 101 is described below, but it should be understood that the description applies equally to the rear electrode assembly 101′ (which is why similar reference numerals are used to label the rear electrode assembly 101′).

[0091] The front electrode assembly 101 comprises an electrically insulating, light transmissive film 103 and a plurality of laterally spaced apart conductive elements in the form of wires 104a-104f disposed on a surface of the film 103. As described further below, the electrode assembly 101 is configured to be disposed on a conductive front surface 111 of the layered structure 102 of the solar cell assembly 100 to draw electrical current generated by the photovoltaic elements of the layered structure 102 (in response to light incident on the solar cell assembly 100).

[0092] Each of the wires 104a-104f has a circular cross-sectional shape (as shown in FIG. 1B). The wires 104a-104f are also evenly spaced apart, parallel to each other, and extend in a longitudinal direction (vertical direction in FIG. 1). It should be understood that only six wires 104a-104f are shown, but some (middle) wires are omitted from the figure for clarity. A first wire 104b of the wires 104a-104f has a first cross-sectional area, and a second wire 104a of the wires 104a-104f has a second cross-sectional area that is larger than the first cross-sectional area (i.e., the second wire 104a has a larger diameter than the first wire 104b). Again, this is particularly evident from FIG. 1B. The first wire 104b has a diameter of 250 μm and the second wire 104a has a diameter of 300 μm.

[0093] The second wire 104a, having a larger cross-sectional area, is one of the two outermost wires of the plurality of wires 104a-104f (the other being the third wire 104f). Although not shown, these wires 104a-104f are disposed on a plurality of finger electrodes of the conductive front surface 111 of the layered structure that extend perpendicularly to the wires 104a-104f. The finger electrodes are evenly distributed across the entire surface and transfer current from the layered structure 102 to the wires 104a-104f for extraction of current from the solar cell assembly 100 by the wires 104a-104f. In general, the amount of current drawn by a particular wire of the plurality of wires 104a-104f depends on the proximity of that wire to any adjacent wires and / or adjacent ends of the layered structure 102.

[0094] Thus, as can be seen, the second wire 104a is required to draw more current than the first wire 104b, since it is the outermost wire of the plurality of wires 104a-104f, which means that all of the current generated in the region between the second wire 104a and the adjacent longitudinal end 105a of the layered structure is drawn only by the second wire 104a. This is in contrast to the first wire 104b, which is between two other adjacent wires (the second wire 104a and the fourth wire 104c), such that the current draw from the region on either side of the first wire 104b is shared by the adjacent wires 104a, 104c.

[0095] In particular, the second wire 104a has a larger effective utilization area than the first wire 104b. The effective utilization area of ​​the first wire 104b is determined by adding half of the first area 117a and half of the second area 117b. The first area 117a is defined between the first wire 104b and the second wire 104a, and the second area 117b is defined between the first wire 104b and the fourth wire 104c. The effective utilization area of ​​the second wire 104b is determined by adding half of the first area 117a and a third area 117c. The third area 117c is defined between the second wire 104a and the adjacent end 105a of the layered structure 102. For illustrative purposes, dashed lines indicating first area 117a, second area 117b, and third area 117c are inserted from wires / ends 104a, 104b, 104c, but it should be understood that these areas 117a, 117b, 117c extend throughout the region between wires / ends 104a, 104b, 105a.

[0096] The larger cross-sectional area of ​​the second wire 104a helps to minimize power losses that would occur, for example, if the second wire were undersized (e.g., had the same cross-sectional area as the first wire 104b) for the area it serves.

[0097] As mentioned above, the plurality of wires 104a-104f also includes a third wire 104f that is a second outermost wire of the plurality of wires 104a-104f and is disposed on the opposite side of the plurality of wires 104a-104f from the second wire 104a. The third wire 104f has the same diameter (300 μm) as the second wire 104a, and therefore the same cross-sectional area.

[0098] The plurality of wires 104a-104f includes a plurality of intermediate wires 104b-104e disposed between the outermost wires 104a, 104f. The first wire 104b is one of these intermediate wires 104b-104e. As is evident from FIG. 1B, each of the intermediate wires 104b-104e has the same diameter as the first wire 104b (so that each intermediate wire 104b-104e has a first cross-sectional area). Each of the intermediate wires 104b-104e offers a smaller area for utilization (in terms of current drawing) than each of the two outermost wires 104a, 104f. In this respect, the diameter (and therefore the cross-sectional area) of the wires 104a-104f corresponds to the respective area that these wires are required to offer for utilization (and therefore the magnitude of the current that these wires are required to draw). This ensures that both power loss (due to under-sizing the wires) and light blockage (due to over-sizing the wires) are minimized.

[0099] In addition to minimizing power loss, making the second wire 104a and the third wire 104f larger can also improve adhesion between the film 103 and the surface of the layered structure 102, as will be described in more detail below.

[0100] As is evident from the figure, the first distance A, which represents the spacing between the wires 104a-104f, is shorter than the second distance B defined between the second wire 104a and the adjacent end 105a of the layered structure 102. Similarly, the first distance A is also shorter than the third distance C defined by the third wire 104f and the adjacent end 105b of the layered structure 102. In the illustrated embodiment, the film 103 has the same width and length dimensions as the layered structure 102. Thus, the second distance B is the same as the fourth distance D defined between the second wire 104a and the adjacent end 106a of the film 103. Similarly, the third distance C is the same as the fifth distance E defined between the third wire 104f and the adjacent end 106b of the film 103.

[0101] The second, third, fourth, and fifth distances can be longer than the first distance because the cross-sectional areas of the second wire 104a and the third wire 104f are larger (i.e., these wires 104a, 104f are capable of a higher current draw). The benefit provided by these longer distances arises from the fact that the two spaces between the second wire 104a and the third wire 104f and their respective adjacent ends 105a, 105b of the layered structure 102 define wire-free regions 107a, 107b. These wire-free regions provide areas within which the film 103 is in direct contact with the front surface of the layered structure 102 (i.e., uninterrupted by the presence of wires). Maximizing this direct contact is desirable because doing so can increase adhesion between the film 103 and the layered structure 102 (and thus can help ensure that the wires 104a-104f are firmly held on the layered structure 102).

[0102] 2 is a cross-sectional view of the layered structure 102 of the solar cell assembly 100 described above. In this view, the layered structure 102 is shown isolated from the front electrode assembly 101 and the rear electrode assembly 101'. The layered structure 102 comprises a multi-layer semiconductor assembly having a photovoltaic element in the form of a semiconductor substrate 108 sandwiched between a front collector layer 109 and a rear collector layer 110. The front collector layer 109 and the rear collector layer 110 are thus disposed on opposite sides of the substrate 108.

[0103] The front collector layer 109 is disposed towards the front surface 111 of the layered structure 102, and the back collector layer 110 is disposed towards the back surface 112. When assembled, the front electrode assembly 101 is electrically connected to the front collector layer 109, and the back electrode assembly 101' is electrically connected to the back collector layer 110. Such a configuration defines a heterojunction technology (HJT) type solar cell. In other embodiments, the layered structure may take other forms (e.g., the solar cell assembly may not be in the form of an HJT type solar cell). For example, in some other embodiments, one or more layers may be absent, one or more layers may be bonded to each other, and / or additional layers may be added, provided that the layered structure 102 can continue to perform its function of generating electricity from incident radiation (e.g., light).

[0104] The substrate 108 is formed of crystalline silicon (c-Si) negatively doped (i.e., n-type material) with impurities of group V elements such as phosphorus (P), arsenic (As), and antimony (Sb). The front collector layer 109 and the back collector layer 110 are each formed of amorphous silicon (a-Si:H). The amorphous silicon is deposited on the front and back surfaces of a silicon wafer using PECVD.

[0105] The back collector layer 110 comprises a positively doped semiconductor material (i.e., a p-type material) and the front collector layer 109 comprises an n-type material. The p-type material contains impurities of group III elements such as boron (B), gallium (Ga), and indium (In).

[0106] In this exemplary configuration of the layered structure 102 , the back collector layer 110 defines an impurity region of the layered structure 102 that has a conductivity type opposite that of the substrate 108 , and thus forms a pn junction with the substrate 108 .

[0107] The multi-layer semiconductor assembly further comprises a first intrinsic layer 113 and a second intrinsic layer 114. Both intrinsic layers 113, 114 are made of intrinsically doped amorphous silicon. The first intrinsic layer 113 is disposed between the front collector layer 109 and the substrate 108 to form a front side passivation layer. Additionally, the second intrinsic layer 114 is disposed between the substrate 108 and the rear collector layer 110 to form a rear side passivation layer.

[0108] Finally, the front surface 111 of the layered structure 102 is covered with a transparent conductive coating 115 formed of indium tin oxide (ITO). The top surface of the ITO layer is textured to provide anti-reflective properties. The anti-reflective layer effectively reduces the reflectance of light incident on the solar cell assembly 100 and increases the selectivity of certain wavelength bands, thereby increasing the efficiency of the solar cell assembly 100.

[0109] The back surface 112 of the layered structure 102 is also covered with a transparent conductive coating 116 formed of indium tin oxide (ITO). The transparent conductive coatings 115, 116 are configured to increase lateral carrier transport to finger electrodes disposed on each surface of the layered structure 102. The transparent conductive coatings 115, 116 are particularly advantageous in heterojunction devices having layers formed of amorphous silicon, which exhibit poor carrier mobility.

[0110] During operation of the solar cell assembly 100, light is incident on the layered structure 102, as indicated by the arrows at the top of FIG. 2. Absorption of the incident photons generates a number of electron-hole pairs. The electron-hole pairs are then separated into electrons and holes by the built-in potential difference caused by the pn junction. The separated electrons migrate to the n-type semiconductor in the substrate 108, and the separated holes migrate to the p-type semiconductor in the back collector layer 110. Thus, the electrons become majority carriers in the substrate 108, and the holes become majority carriers in the back collector layer 110. Each of these majority carriers is extracted from the layered structure 102 by a respective electrode assembly 101, 101′.

[0111] It is understood that the present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the concept described herein. Any feature can be used separately or in combination with any other feature, except where mutually exclusive, and the present disclosure extends to and includes all combinations and subcombinations of one or more features described herein.

Claims

1. 1. A solar cell assembly comprising: a layered structure having a photovoltaic element and a conductive surface; 1. A solar cell assembly comprising: an electrode assembly having a plurality of longitudinally extending, laterally spaced apart conductive elements, the plurality of conductive elements comprising a first conductive element having a first cross-sectional area and a second conductive element having a second cross-sectional area greater than the first cross-sectional area, the electrode assembly being disposed on the conductive surface of the layered structure such that the conductive elements are in ohmic contact with the conductive surface.

2. 10. The solar cell assembly of claim 1, wherein the plurality of conductive elements comprises two outermost conductive elements and a plurality of intermediate conductive elements disposed between the two outermost conductive elements.

3. The solar cell assembly of claim 2 , wherein the second conductive element is an outermost conductive element of the plurality of conductive elements.

4. The solar cell assembly of claim 2 , wherein the first conductive element is an intermediate conductive element.

5. The solar cell assembly of claim 2 comprising a third conductive element having a third cross-sectional area greater than the first cross-sectional area.

6. The solar cell assembly of claim 5 , wherein the third conductive element is an outermost conductive element of the plurality of conductive elements.

7. The solar cell assembly of claim 2 , wherein the two outermost conductive elements each have a cross-sectional area that is greater than a cross-sectional area of ​​each of the intermediate conductive elements.

8. 3. The solar cell assembly of claim 2, wherein a distance between an outermost conductive element of the plurality of conductive elements and an adjacent edge of the layered structure is equal to or greater than a distance between two adjacent conductive elements of the plurality of conductive elements.

9. The solar cell assembly of claim 1 , wherein the plurality of conductive elements are evenly spaced apart.

10. The first cross-sectional area is 0.03 mm ２ ~0.07mm ２ 2. The solar cell assembly of claim 1, wherein:

11. The second cross-sectional area is 0.05 mm ２ ~0.1mm ２ 2. The solar cell assembly of claim 1, wherein:

12. The second cross-sectional area is 0.01 mm smaller than the first cross-sectional area. ２ ~0.03mm ２ The solar cell assembly of claim 1 which is large.

13. The solar cell assembly of claim 1 , wherein each conductive element has a circular transverse cross-sectional shape.

14. The solar cell assembly of claim 1 , wherein the electrode assembly comprises an insulating, light-transmitting film for holding the plurality of conductive elements on the conductive surface of the layered structure.

15. The second conductive element has a larger effective area than the first conductive element, and the effective area is: an intermediate conductive element that is half a first area plus half a second area, the first area being defined as the area between the intermediate conductive element and a first adjacent conductive element, and the second area being defined as the area between the intermediate conductive element and a second adjacent conductive element; 3. The solar cell assembly of claim 2, wherein the fourth area is determined for an outermost conductive element by adding half of a third area and a fourth area, the third area being defined as the area between the outermost conductive element and an adjacent conductive element, and the fourth area being defined as the area between the outermost conductive element and an adjacent edge of the layered structure.

16. An electrode assembly for a solar cell, comprising: an insulating light-transmitting film; a plurality of longitudinally extending conductive elements disposed on a surface of the film at laterally spaced intervals, the plurality of conductive elements comprising: a first conductive element having a first cross-sectional area; and a second conductive element having a second cross-sectional area larger than the first cross-sectional area.

17. 17. The electrode assembly of claim 16, wherein the plurality of conductive elements includes two outermost conductive elements and a plurality of intermediate conductive elements disposed between the two outermost conductive elements.

18. 20. The solar cell assembly of claim 17, wherein the second conductive element is the outermost conductive element.

19. 20. The solar cell assembly of claim 17, wherein the first conductive element is an intermediate conductive element.

20. 20. The solar cell assembly of claim 17, wherein a distance between an outermost conductive element of the plurality of conductive elements and an adjacent edge of the film is equal to or greater than a distance between two adjacent conductive elements of the plurality of conductive elements.

21. 17. The solar cell assembly of claim 16, wherein the conductive elements are evenly spaced apart.

22. The second cross-sectional area is 0.01 mm smaller than the first cross-sectional area. ２ ~0.03mm ２ The solar cell assembly of claim 16 which is large.

23. 17. The solar cell assembly of claim 16, wherein each conductive element has a circular transverse cross-sectional shape.

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