Module layup for perovskite-silicon tandem solar cells

Abstract

A solar cell module and method of manufacture are described. In one embodiment, a pair of tandem solar cells are bonded together along a contact ledge of a first tandem solar cell using a solid conductive bonding material.

Description

[Technical Field]

[0001] TECHNICAL FIELD Embodiments described herein relate to solar cells, and more particularly to series connections made between overlapping tandem solar cells.

[0002] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Provisional Application No. 63 / 378,585, filed October 6, 2022, which is incorporated herein by reference. [Background technology]

[0003] Photovoltaic cells, also called solar cells, are devices that convert radiant light energy into electrical energy. Multiple solar cells may be combined into groups to form solar panels or modules, with some or all of the solar cells typically connected in series to produce an additive voltage.

[0004] Conventional silicon solar cells are connected and arranged into modules in two main ways. In the first implementation, full or half cells are connected to the front of the solar cell by soldered wire or flat busbar ribbons, specifically screen-printed metal fingers or busbars. The attached busbars are longer than the cells and can contact the back of the next cell in a series connection. In another implementation, smaller cells are connected in series using conductive bonds, a process in which the top of one cell is placed under the next, allowing the positive terminal of one cell to contact the negative terminal of the next cell, or vice versa, depending on the type of solar cell used. Summary of the Invention

[0005] Solar cell modules and methods of manufacture including overlapping tandem solar cells are described. In some embodiments, contact ledges are patterned on the tandem solar cells to relieve stress on the top subcell of the tandem solar cell. More specifically, the contact ledges may be formed through the top perovskite subcell in a tandem perovskite-silicon subcell, so that when series tandem subcells are connected, this can be achieved by bonding the backside of the tandem solar cell to the contact ledge of the underlying tandem solar cell. More specifically, the contact ledges may be on the bottom silicon subcell of the overlapping tandem solar cell so that pressure is not applied directly onto the perovskite subcell.

[0006] In some embodiments, low-temperature conductive bonding materials, such as solid adhesive tape, may be used to bond overlapping tandem solar cells in series to each other or to bond a bus bar to the top of the tandem solar cells. Such low-temperature conductive bonding materials can mitigate degradation of the perovskite subcell materials with heat exposure. [Brief explanation of the drawings]

[0007] [Figure 1] 1A and 1B are schematic top and circuit diagrams of a solar cell module, according to an embodiment.

[0008] [Figure 2A] FIG. 1 is an illustration of a silicon-perovskite tandem solar cell stackup based on an n-type silicon substrate, according to one embodiment.

[0009] [Figure 2B] FIG. 1 is an illustration of a silicon-perovskite tandem solar cell stackup based on a p-type silicon substrate, according to one embodiment.

[0010] [Figure 3A] 1 is a schematic top view of a pair of stacked solar cells, according to one embodiment.

[0011] [Figure 3B] 1 is a schematic side view of a pair of stacked solar cells, according to one embodiment.

[0012] [Figure 4] FIG. 1 is a schematic cross-sectional side view of mechanical failure in a perovskite subcell.

[0013] [Figure 5] 1 is a schematic cross-sectional side view of a pair of stacked solar cells connected along a patterned subcell ledge, according to one embodiment.

[0014] [Figure 6A] FIG. 1B is a schematic top view of a silicon subcell patterned across a conductive front surface, according to one embodiment.

[0015] [Figure 6B] FIG. 1B is a schematic top view of a recombination layer with patterned openings over an underlying silicon pattern, according to one embodiment.

[0016] [Figure 6C] FIG. 1C is a schematic top view of a perovskite subcell patterned to expose the contact ledge of the recombination layer, according to one embodiment.

[0017] [Figure 6D] FIG. 1B is a schematic top view of a front finger and bus bar disposed over a patterned solar cell, according to one embodiment.

[0018] [Figure 7] 1 is a schematic cross-sectional side view of a pair of stacked solar cells connected along a patterned subcell ledge, according to one embodiment.

[0019] [Figure 8] 1 is a schematic cross-sectional side view of a pair of stacked solar cells, according to one embodiment.

[0020] [Figure 9] FIG. 1 is a schematic top view of an on-cell busbar, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] The embodiments describe solar cell modules and manufacturing methods. In one embodiment, the solar cell module includes a first tandem solar cell including a first lower silicon subcell and a first upper perovskite subcell patterned to form a contact ledge on the first lower silicon subcell. The backside of a second tandem solar cell is then bonded to the contact ledge of the first tandem solar cell using a conductive bonding material. In this manner, forces applied to the top surface of the first tandem solar cell by the backside of the second tandem solar cell during assembly, handling, etc. can be absorbed by the first lower silicon subcell rather than the relatively weaker perovskite subcell, thereby mitigating potential mechanical damage to the perovskite subcell. Furthermore, the second or upper tandem solar cell can be positioned to minimize overlap with the first or lower tandem solar cell so as not to obscure the solar cells of the first or lower tandem solar cell. Any suitable conductive bonding material, such as solder, a conductive adhesive layer such as solid adhesive tape, a liquid adhesive material, or the like, can be utilized in such configurations to transfer stress.

[0022] In some embodiments, a conductive adhesive layer, such as a solid adhesive tape, is used to bond the tandem solar cell. In this way, high-temperature bonding processes, such as those using solder, which can degrade the perovskite subcell materials, can be avoided. Furthermore, the solid adhesive tape can avoid the reflow and degradation that can occur with liquid adhesive materials. In addition, a contact ledge on top of the first, lower silicon subcell can absorb bonding pressures, preventing conductive material (e.g., pins, particles, etc.) in the conductive adhesive layer from migrating to the underlying perovskite layer, which may be more susceptible to mechanical deformation and therefore device degradation.

[0023] In various embodiments, the description is provided with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions, and processes, to provide a thorough understanding of the embodiments. In other instances, well-known semiconductor process and manufacturing techniques have not been described in particular detail in order to avoid unnecessarily obscuring the embodiments. References throughout this specification to "one embodiment" mean that a particular feature, structure, configuration, or characteristic described in connection with an embodiment is included in at least one embodiment. Thus, the appearances of the phrase "in one embodiment" in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] As used herein, the terms "above," "over," "to," "between," "spanning," and "on" may refer to the relative position of one layer with respect to another. A layer that is "above," "over," "spanning," or "on" another layer, or "bonded to" or "in contact" another layer, may be in direct contact with the other layer or may have one or more intervening layers. A layer "between" layers may be in direct contact with the layer or may have one or more intervening layers.

[0025] 1, a schematic top view of a solar cell module according to an embodiment is provided. As shown, the solar cell module 100 includes multiple cells 115 (also called solar cells) coupled in series with interconnects 131, with the front of one cell connected to the back of the next cell, so that their voltages (V1...V n ) are added together. Multiple cells 115 may be arranged in one or more subsets 110 (e.g., strings) coupled in parallel, which may have the effect of reducing the total module voltage. Other configurations are possible, such as a second column of cells aligned offset from the center of the first column by half the length of the cells, and a third column of cells aligned offset from the second column by half the length of the cells. In the latter, several entire rows of cells are connected in parallel. This layout is sometimes referred to as a "matrix" array.

[0026] Referring now to Figures 2A and 2B, Figure 2A is a silicon-perovskite tandem solar cell stackup based on an n-type silicon substrate, according to an embodiment, and Figure 2B is a silicon-perovskite tandem solar cell stackup based on a p-type silicon substrate, according to an embodiment. In the following description, various layers and compositions are described with respect to the solar cell stackup. It should be understood that each layer may include a single layer or multiple layers. Furthermore, references herein to a bottom layer or a top layer are relative and may not reflect the actual orientation in the product.

[0027] In the particular embodiment shown in Figures 2A and 2B, the solar cell 115 can absorb light from the top surface of the illustrated stackup. Referring to Figure 2A, the tandem structure can include an upper perovskite subcell 220B formed on a lower silicon subcell 220A that includes a doped silicon substrate 330 (e.g., an n-doped substrate), a p-doped silicon layer 351 (e.g., p+ doped), and optionally an n-doped silicon layer 350 (e.g., n+ doped). A back contact 310 can also be formed below the p-doped silicon layer 351. The back contact 310 can be formed from a suitable material, such as Ag, Cr, Au, Cu, or Al. It should be understood that the exemplary silicon subcell 220A and contacts can include various configurations according to all embodiments, including heterojunction (HJT) designs, tunnel oxide passivation contacts (TOPCon), passivation rear contact solar cells (PERC), and the like.

[0028] The n-doped silicon layer 350 (e.g., n+ doped) and the p+ doped silicon layer 351 can be crystalline, polycrystalline such as in the case of a TOPCon design, or amorphous such as in the case of an HJT design. In such an HJT design, an additional intrinsic layer (e.g., intrinsic silicon) can be formed between the doped silicon substrate 330 and the p-doped silicon layer 351 and the n-doped silicon layer 350. For example, the intrinsic layer can be formed by treating the doped silicon substrate 330 with a hydrogen plasma or the like. The intrinsic layer can also be crystalline or amorphous.

[0029] A recombination layer 355 may be disposed between the subcells 220. The recombination layer 355 may be formed of a transparent conductive material such as TCO, specifically ITO.

[0030] The perovskite subcell 220B includes an absorber layer 140 and one or more transport layers. In the illustrated embodiment, the perovskite subcell 220B includes a hole transport layer (HTL) 130 above an optional recombination layer 355, an absorber layer 140 above the HTL 130, and an electron transport layer (ETL) 150 above the absorber layer 140.

[0031] The HTL 130 can include one or more layers formed from metal oxides such as nickel oxide (NiOx) or vanadium oxide (VO), organic polymers such as poly(triarylamine) (PTAA), small molecules such as 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-MeOTAD), or "self-assembled monolayers" in which hole-transporting moieties are bound to the underlying TCO or HTL layer through acid-binding agent groups such as phosphate or carboxylic acids. The HTL 130 may be additionally doped to enhance conductivity and may include a bilayer of metal oxide (e.g., NiOx) and an upper organic layer such as PTAA.

[0032] The absorber layer 140 according to embodiments can be formed of a perovskite material. Perovskite materials can be characterized by the formula ABX3, where A represents a large atomic or molecular cation (e.g., Cs, methylammonium, formamidinium, etc.), B represents a positively charged cation (e.g., metal, lead, plumbate, Sn), and X represents a negatively charged anion (e.g., halide, I, Br, Cl). Perovskite materials can also be characterized by the formula ABX3, where A represents a large atomic or molecular cation (e.g., Cs, methylammonium, formamidinium, etc.), B represents a positively charged cation (e.g., metal, lead, plumbate, Sn), and X represents a negatively charged anion (e.g., halide, I, Br, Cl). 1 m A n B n -1X3 n-1 The compound may comprise a mixture of 2D and 3D structures in the family of 1 represents a positively charged cation (e.g., butylammonium, phenethylammonium, guanidinium, etc.) Alternative materials, such as organic materials, can also be used as the absorbing layer.

[0033] The ETL 150 according to embodiments can be formed from fullerenes, metal halides, tin oxide, titanium oxide, naphthalene diimides, and related derivatives, among others. An additional buffer layer can be included as part of or on the ETL 150. For example, the buffer layer can physically separate the electrode layer or top metal pattern from the subcell, more specifically, the absorber layer. In one embodiment, the buffer layer is formed on the fullerene ETL 150 from a metal oxide material, such as tin oxide, titanium dioxide, or aluminum zinc oxide (AZO). The buffer layer can function as a barrier layer as well as a charge transport layer. In certain embodiments, the electrode layer 170 is formed from a transparent conductive material.

[0034] Because the lower silicon subcell 220A may be opaque, the top electrode layer 170 may be formed from a transparent conductive layer such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), cadmium stannate, or other transparent conductive oxides (TCOs). A top metal pattern 181 may then be formed on the transparent top electrode layer 170, for example, to facilitate charge transport. In one embodiment, the top metal pattern is formed from a suitable material such as Ag, Cr, Au, Cu, or Al. The top metal pattern 181 may be formed in the shape of a plurality of metal finger 180 electrodes, and optionally in the shape of a bus bar connecting the plurality of metal finger electrodes to transport charges without excessively blocking light transmission.

[0035] 2B, a tandem structure may include an upper perovskite subcell 220B formed on a lower silicon subcell 220A that includes a doped silicon substrate 330 (e.g., a p-doped substrate), an n-doped silicon layer 350 (e.g., n+ doped), and optionally a p-doped silicon layer 351 (e.g., p+ doped). Thus, the lower silicon subcell 220A of FIG. 2B may be based on a p-doped silicon substrate rather than the n-doped silicon substrate of FIG. 2A. In such an embodiment, the n-doped silicon layer 350 may be optional, whereas the p-doped silicon layer 351 may be optional.

[0036] 2A and 2B, specific stackups are described and illustrated with np, pn, nip, or pin orientations. These variations in the order of layer formation may further alter the material selection of some layers without departing from the principles of the embodiments. Thus, references to ETL or HTL and n-doped or p-doped layers may be reversed depending on the embodiment.

[0037] In one aspect, it has been observed that conventional silicon solar cells are connected to each other by soldering metal busbars (typically 0.5-2 mm flat metal ribbons) to the front of the solar cells. Specifically, the busbar ribbons are soldered to screen-printed metal fingers and busbars (e.g., of the top metal pattern). The attached busbars are generally longer than the solar cells and can contact the next solar cell in a series connection. However, it has been observed that perovskite solar cells (and subcells) are sensitive to heat (e.g., temperatures above 150°C can cause damage, and soldering is typically performed at >200°C) and pinpoint pressure, and therefore the soldering process is likely to damage perovskite-silicon tandem solar cells. Furthermore, connecting solar cells with only a few solder joints also reduces the mechanical stability of the solar cells. Each joint has been observed to be one of the most common causes of failure in silicon solar cells.

[0038] According to embodiments, these problems can be overcome or mitigated by using an electrically conductive adhesive (ECA) to secure the busbar to the solar cells and to bond the series solar cells. While ECAs are available as both liquids and solids during application, it has been observed that the liquids used in most commercially available ECAs can damage perovskite solar cells or subcells and therefore may not be suitable for tandem production. It has been observed that during curing of ECAs that are liquid during application, the polymer binder component of the adhesive tends to "leak" from the desired area and adversely affect the optical properties of the cell area adjacent to the busbar. According to some embodiments, solid ECA tapes can be used. These can contain polymer matrix adhesives (e.g., acrylic, silicone, butyl rubber, etc.) embedded with conductive particles (e.g., made from metals such as silver, copper, aluminum, nickel, etc., or made from carbon) and / or wires or pins (depending on whether only Z or XYZ conductivity is desired), or metal-coated particles. When stacked under pressure, the particles and / or wires or pins transport electrical current directly between the two materials between which the tape is placed.

[0039] Referring now to FIGS. 3A and 3B, schematic top and cross-sectional side views of a pair of stacked tandem solar cells 115 are provided, according to one embodiment. As shown, the backside of the second tandem solar cell 115B (top solar cell) can be bonded to the first tandem solar cell 115A (bottom solar cell) using an electrically conductive adhesive layer (ECA) 190. Specifically, the ECA 190 can be applied as a solid conductive tape rather than as a liquid adhesive. Such a solid tape may not require curing at temperatures typical of liquid adhesive materials, which may contain silver particles that require curing temperatures too high for perovskites. The solid ECA 190 tape can also provide improved mechanical properties, since the mechanical connection between the cells relies on a polymer adhesive. This is particularly important for modules that may need to withstand vibration or be curved in shape. Still referring to FIGS. 3A and 3B, bonding may optionally be performed to a busbar 185 formed on the first tandem solar cell 115A (bottom solar cell). Bus bars 185 may be formed as part of the top metal pattern 181, which may include metal fingers 180 that extend over the first tandem solar cell 115 A. However, the bus bars and fingers may be omitted where light transmission is preferred.

[0040] In the particular embodiment shown in Figures 3A and 3B, the second tandem solar cell 115B (top solar cell) can be bonded to the first tandem solar cell 115A (bottom solar cell) at various locations. For example, briefly referring back to Figures 2A and 2B, the back contact 310 (electrode) of the top tandem solar cell 115B can be bonded to the metal fingers 180 (or busbar 185) or electrode layer 170 of the bottom tandem solar cell 115A using an ECA 190. As described in further detail herein, the top perovskite subcell 220B of the bottom tandem solar cell 115A may be patterned to form a contact ledge to avoid stress on the absorber layer 140 of the bottom tandem solar cell 115A, which helps to avoid short circuits and mechanical failure when threshold bonding pressures are exceeded or during installation and operation of a final module including the solar cell string described herein.

[0041] As shown in Figures 3A and 3B, connecting two single-junction cells (e.g., the solar cell of Figure 2A) in series by stacking them can be straightforward. However, it has been observed that connecting tandem cells can be difficult for several reasons. In particular, both liquid and solid tape ECAs contain irregularly shaped metal particles, typically >1 μm in size for liquid ECAs and >25 μm in size for solid tape ECAs, and the pressure used to stack modules together (e.g., stacking the backside of the second tandem solar cell 115B onto the top side of the first tandem solar cell) can cause the particles to "punch through" the <1 μm thick perovskite absorber portion of the bottom perovskite subcell 220B, effectively creating a short circuit through the perovskite half of the tandem solar cell. As shown in FIG. 4, local adhesion and pressure at the ECA junction between the perovskite front surface and the silicon back surface of two tandem solar cells can cause mechanical failure in the mechanically weaker top subcell 220B, such as the perovskite subcell 220B, when the cell or module is subjected to mechanical stress, such as that experienced during manufacturing or module installation and operation.

[0042] According to some embodiments, the front surface (often referred to as the "front emitter") of the lower solar cell 115A is patterned to prevent conductive particles (from the ECA 190) from penetrating into the front perovskite subcell 220B and adversely affecting the electrical properties of the connection. Such patterning can be done by lithography or shadow masking during the doping process (e.g., for the n-doped silicon layer 350 on a P-type wafer for a silicon tunnel oxide passivated contact (TOPCon) or passivated emitter and rear contact (PERC) cell, which is not required for heterojunction cells), or by post-deposition laser patterning. The recombination layer 355 is typically laterally conductive and may be similarly patterned. For heterojunction cells with low-conductivity front (n-side in the most common tandem configuration) passivation, the silicon front surface does not need to be patterned, but the recombination layer (e.g., TCO) does. This can be done by either shadow masking or laser patterning.

[0043] According to embodiments, the perovskite subcell 220 in the tandem subcell may be relatively weak compared to the silicon subcell 220. According to embodiments, the perovskite subcell, and in particular the absorber layer 140, may be patterned during deposition (e.g., using a shadow mask) or by laser ablation after deposition.

[0044] In the following description of Figures 5-9, various connected (e.g., overlapping) tandem solar cell configurations and methods of fabrication and assembly are described. In particular, the tandem solar cell configurations described and illustrated are similar to those shown and described with respect to Figures 2A and 2B. Accordingly, specific layers or compositions may not be separately described again. Furthermore, while embodiments are described with respect to the specific configuration shown in Figures 2A and 2B, the embodiments are not so limited and may be utilized with tandem solar cells based on other stackups or other materials that do not include silicon. The embodiments may also be used with any material system in which the top subcell is mechanically weaker than the bottom subcell, and thus are not limited to perovskite top subcells or silicon-perovskite tandem solar cells.

[0045] Referring to Figure 5, a schematic cross-sectional side view of a pair of stacked solar cells connected along a patterned subcell ledge is provided, according to one embodiment. As shown, the solar cell module can include a first tandem solar cell 115A (bottom solar cell) including a first bottom silicon subcell 220A and a first top perovskite subcell 220B patterned to form a contact ledge 195 on the first bottom silicon subcell 220A. The second (top) tandem solar cell 115B also includes a second bottom silicon subcell 220A and a second top perovskite subcell 220B. As shown, the back surface 221 of the second bottom silicon subcell 220A is bonded to the contact ledge 195 by an electrically conductive adhesive layer (ECA) 190. As previously described, the ECA 190 can include an electrically conductive material 194 (e.g., pins, particles, etc.) within a polymer matrix 192. The contact ledge 195 may intersect the lateral edge 117 of the first tandem solar cell 115A. It should be understood that other conductive bonding materials, including solder, solder paste, etc., may be used in place of an ECA 190 having such a contact ledge 195 configuration while still relieving stress on the top perovskite sub-cell 220B.

[0046] As shown in the particular embodiment illustrated, the lateral conductive recombination layer 355 is disposed between the first lower silicon subcell 220A and the first upper perovskite subcell 220B. A first transparent top electrode layer 170 may also be formed and patterned over the underlying perovskite subcell 220B. In the illustrated embodiment, the first transparent top electrode layer optionally does not extend over the contact ledge 195. A first top metal pattern 181 may then be formed extending over the first transparent top electrode layer 170 and the lateral conductive recombination layer 355 over the contact ledge 195 to form a bus bar 185 over the contact ledge. Thus, the bus bar 185 and the metal fingers 180 of the top metal pattern 181 may be formed simultaneously or separately. As shown, the backside 221 of the second lower silicon subcell 220A (which may optionally be the backside contact 310 in FIGS. 2A and 2B) may be bonded to the busbar 185 using the ECA 190.

[0047] Various patterned line openings of various widths may be formed to prevent shorts across the solar cell. For example, a first patterned line opening (P1) may be formed through the upper surface of the first lower silicon subcell 220A. In the particular embodiment shown, this may be done through the n-doped silicon layer 350. It should be understood that this is exemplary and the doping may be reversed. Such openings may not be required for heterojunction (HJT) solar cells. A first patterned line opening may be formed in the appropriate silicon subcell 220A to avoid shorts between the highly doped layers 350. In the particular embodiment shown, a second patterned line opening (P2) is formed through the lateral conductive recombination layer 355, with P2 being directly above and wider than P1. The backside metallization and backside doped layer of the silicon subcell 220A may be similarly patterned with backside patterned line openings (Px) to prevent current flow in the overlapping areas. Px may be directly below P1 and may have similar dimensions, for example. The relative widths of the P1 and P2 openings may be reversed, provided that one overlaps the other.

[0048] A plurality of stacked tandem solar cells can be integrated into a module that includes a backsheet 210, a transparent encapsulant 212 around the plurality of tandem solar cells, and a transparent cover layer 214, such as glass.

[0049] A process sequence for forming the exemplary solar cell 115 of FIG. 5 is provided in FIGS. 6A-6D. As shown in FIG. 6A, the sequence can begin with a silicon subcell wafer 101 patterned across its conductive front and backside surfaces. Depending on the type of silicon subcell being formed, this frontside pattern may also extend across the n-doped silicon layer 350 of the exemplary embodiment. As shown in FIG. 6B, a recombination layer 355 may be added and patterned (e.g., silicon cut) with a second patterned line opening (P2) wider than P1. The perovskite subcell 220A may then be formed and patterned as shown in FIG. 6C, exposing the contact ledge 195. For example, the contact ledge 195 may be the exposed recombination layer 355. Processing of the top perovskite subcell 220B, including the top electrode layer 170 (e.g., TCO) and top metal pattern 181 (e.g., including fingers 180 and busbar 185), can then be completed.

[0050] In other embodiments, the perovskite sub-cell 220B is not patterned into a ledge, for example in certain configurations it may not be necessary to pattern the perovskite sub-cell, but it may still be necessary to pattern the front / back emitter and recombination layers.

[0051] In other embodiments, only the perovskite layer or only the silicon layer is patterned, or only the silicon layer is patterned. Solar cells according to embodiments are envisioned where they are formed in tandem without a lateral conductive recombination layer.

[0052] FIG. 7 is a schematic cross-sectional side view of a pair of stacked tandem solar cells connected along a patterned subcell ledge, according to one embodiment. FIG. 7 may be substantially similar to that of FIG. 5, with one difference being that the recombination layer 355 is not laterally conductive. In such an embodiment, there is no need to form a second patterned line opening (P2), and the recombination layer 355 can extend over and at least partially fill the first patterned line opening (P1). As with the embodiment of FIG. 5, the perovskite subcell 220B can be removed at the mechanical connection points that define the contact ledges. It should be understood that other conductive bonding materials, including solder, solder paste, and the like, can be used in place of an ECA 190 having such a contact ledge 195 configuration while still relieving stress on the upper perovskite subcell 220B.

[0053] 8 is a schematic cross-sectional side view of a pair of stacked tandem solar cells according to one embodiment. In such an embodiment, overlapping tandem solar cells 115 can be stacked back-to-back without removing the top subcell 220B (e.g., perovskite). As with the previous embodiment, a busbar 185 can optionally be formed to enhance contact with the ECA 190. The busbar 185 can be formed as part of the same layer as the metal fingers 180 or as a separate layer. In one embodiment, the solar cell module includes a first transparent top electrode layer 170 over the first top perovskite subcell 220B and a first top metal pattern 181 extending over the first transparent top electrode layer 170, the first top metal pattern including a plurality of metal fingers 180 and a busbar 185 adjacent to the lateral edges 117 of the first tandem solar cell. The back surface 221 of the second tandem solar cell 115B is bonded to the bus bar 185 using the ECA 190. In the illustrated embodiment, the first tandem solar cell 115A includes a first patterned line opening (P1) that penetrates the upper surface of the first lower silicon subcell 220A. The bus bar 185 is parallel to P1, and the bus bar 185 may be positioned substantially laterally adjacent to a first lateral edge 349 of P1. For example, the first lateral edge 349 may be the edge of P1 that is closest to the lateral edge 117 of the first tandem solar cell 115A. Such a configuration can reduce the overlapping area of ​​the active regions of the tandem solar cells. In one embodiment, the first tandem solar cell 115 further includes a recombination layer 355 between the first lower silicon subcell 220A and the first upper perovskite subcell 220B, and a second patterned line opening (P2) through the recombination layer, where P2 is directly above and wider than P1.

[0054] Up to this point, the ECA 190 has been described with respect to bonding tandem solar cells to one another; however, the ECA 190, particularly a solid-state ECA such as a tape, can be used to bond a bus bar 185 (e.g., a flat metal ribbon, etc.) to an underlying structure. FIG. 9 is a schematic top view of an on-cell bus bar 185, according to one embodiment. As shown, the tandem solar cell 115 can include fingers 180 formed using conventional deposition techniques for the tandem solar cells 115. Following this, the solid-state ECA 190 can be used to bond the on-cell bus bar 185 (e.g., a flat metal ribbon). In this manner, multiple tandem solar cells 115 can be connected to one another. In one embodiment, a solar cell module comprises a first tandem solar cell including a first plurality of metal fingers, a second tandem solar cell including a second plurality of metal fingers, and a bus bar bonded to the first plurality of metal fingers with a conductive adhesive material and bonded to a back surface of the second tandem solar cell with a second conductive adhesive material, such as for additional connections.

[0055] It will be apparent to those skilled in the art that combinations or variations of the above embodiments are possible when utilizing various aspects of the embodiments to form solar cell modules having overlapping tandem solar cells. While the embodiments have been described herein with respect to silicon-perovskite tandem solar cells, this is exemplary and the embodiments may be applied to alternative tandem solar cell compositions. Although the embodiments have been described in language specific to structural features and / or methodological acts, it should be understood that the appended claims are not necessarily limited to the specific features or acts described. The specific features and acts disclosed should instead be understood as illustrative embodiments of the claims.

Claims

1. A solar cell module, A first tandem solar cell, comprising: a first lower silicon subcell; a first upper perovskite sub-cell patterned to form a contact ledge on the first lower silicon sub-cell; and a second tandem solar cell, a second lower silicon subcell; and a second upper perovskite sub-cell; and a second tandem solar cell comprising: a back surface of the second lower silicon subcell bonded to the contact ledge using a conductive bonding material.

2. The solar cell module according to claim 1 , wherein the conductive bonding material is a solder material.

3. The solar cell module of claim 1 , wherein the conductive bonding material is a conductive adhesive layer comprising a conductive material within a polymer matrix.

4. 10. The solar cell module of claim 1, further comprising a recombination layer between the first lower silicon subcell and the first upper perovskite subcell.

5. 5. The solar cell module of claim 4, further comprising a first transparent upper electrode layer over the first upper perovskite subcell.

6. The solar cell module of claim 5 , wherein the first transparent top electrode layer does not extend completely over the contact ledge.

7. 6. The solar cell module of claim 5, further comprising a first top metal pattern extending over the first transparent top electrode layer and the recombination layer on the contact ledge to form a bus bar on the contact ledge.

8. 8. The solar cell module of claim 7, wherein the back surface of the second lower silicon subcell is bonded to the bus bar using the conductive bonding material, and the conductive bonding material is a conductive adhesive layer.

9. 9. The solar cell module of claim 8, further comprising a first patterned line opening (P1) through an upper surface of the first lower silicon subcell.

10. 10. The solar cell module of claim 9, further comprising a second patterned line opening (P2) through the recombination layer, said P2 being directly above said P1 and wider than said P1.

11. 1. A method for assembling a solar module, comprising: The method includes bonding a back surface of a second tandem solar cell to a front surface of a first tandem solar cell using a conductive adhesive tape.

12. the first tandem solar cell comprising a first lower silicon sub-cell and a first upper perovskite sub-cell patterned to form a contact ledge on the first lower silicon sub-cell; 12. The method of claim 11 , wherein bonding the back surface of the second tandem solar cell comprises bonding the back surface of the second tandem solar cell to the contact ledge using the conductive adhesive tape.

13. A solar cell module, a first solar cell including a first plurality of metal fingers; a bus bar joined to the first plurality of metal fingers with a conductive adhesive material.

14. 14. The solar cell module of claim 13, further comprising a second tandem solar cell including a second plurality of fingers, the bus bar being bonded to a back surface of the second tandem solar cell with a second conductive adhesive material.

15. A solar cell module, A first tandem solar cell, a first lower silicon subcell; a first upper perovskite subcell; and an upper electrode layer over the first upper perovskite subcell; and a top metal pattern on the top electrode layer; and a second tandem solar cell, a second lower silicon subcell; and a second upper perovskite subcell; and a backside contact on a bottom surface of the second lower silicon subcell; A solar cell module, wherein the back contact of the second tandem solar cell is bonded to the top metal pattern of the first tandem solar cell with a conductive adhesive layer.

16. a first transparent upper electrode layer over the first upper perovskite subcell; and 16. The solar cell module of claim 15, further comprising: a first top metal pattern extending over the first transparent top electrode layer, the first top metal pattern including a plurality of metal fingers and bus bars adjacent lateral edges of the first tandem solar cell.

17. The solar cell module of claim 16 , wherein the back surface of the second tandem solar cell is bonded to the bus bar using the conductive adhesive layer.

18. 18. The solar cell module of claim 17, further comprising a first patterned line opening (P1) through an upper surface of the first lower silicon subcell, the bus bar being parallel to P1 and the bus bar being positioned substantially laterally adjacent a first lateral edge of P1.

19. 20. The solar cell module of claim 18, further comprising a recombination layer between the first lower silicon subcell and the first upper perovskite subcell.

20. 20. The solar cell module of claim 19, further comprising a second patterned line opening (P2) through the recombination layer, said P2 being directly above said P1 and wider than said P1.

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