Multi-junction photovoltaic device

Abstract

The multi-junction photovoltaic device has a first subcell (11b) and a second subcell (11a), with the second subcell (11a) overlapping the first subcell (11b) so that incident light passes through the second subcell (11a) before the first subcell (11b). The light-receiving surface of the second subcell (11a) has a layer of transparent conductive material (12) and one or more metal tracks (13) extending in a first direction and in contact with the layer of transparent conductive material (12). A layer of electrically insulating material (16) is provided on the light-receiving surface of the second subcell (11a) at the edge of the device, underlying one end of the one or more metal tracks (13), and electrically conductive pads (14) are provided on the layer of electrically insulating material (16) and in electrical contact with the one or more metal tracks (13) to provide electrical contact to an external circuit.

Description

Technical Field

[0001] The present invention relates to photovoltaic (PV) devices, and more particularly to multi-junction photovoltaic devices monolithically integrated such as tandem solar cells and PV panels.

Background Art

[0002] Solar energy conversion is one of the most promising technologies for providing renewable energy. However, the high cost of manufacturing devices for capturing solar energy, including high material costs, has historically hindered its widespread use.

[0003] For example, single-junction solar cells such as silicon p-n junctions have a maximum theoretical efficiency of about 29% and a maximum practical efficiency of 26% under AM1.5G conditions (see, for example, Non-Patent Document 1). However, when cells of materials with higher bandgaps are stacked on silicon single-junction cells (or other types of single-junction cells) and connected in series, the limiting theoretical efficiency increases to over 40%. Thus, there is currently much interest in tandem and other multi-junction cell technologies.

[0004] A conventional example of a monolithic integrated multi-junction cell is shown in FIGS. 1A (plan view) and 1B (cross-sectional view). The device has a first sub-cell (1b) and a second sub-cell (1a) that is in electrical contact with the first sub-cell (1b), and the sub-cells are configured such that incident light passes through the second sub-cell (1a) and reaches the first sub-cell (1b) in use. The surface of the second sub-cell has a light-receiving surface having a layer of a light-transmissive conductive material (2) and one or more metal tracks (e.g., copper strips, etc.) that are in contact with the layer of the light-transmissive conductive material (2) and extend in a first direction (i.e., parallel to the A-A' axis). Typically, conductive pads (e.g., metal ribbons) are provided both on top of the metal tracks (4) and at the bottom of the device (5), and electrical connection between the bottom conductive pads of one device and the top conductive pads of adjacent devices enables series connection and stringing of multiple devices.

[0005] However, one problem in the manufacture of photovoltaic modules and panels using multi-junction devices such as those of FIGS. 1A and 1B is short-circuiting through the multi-junction cell when electrical connection to the device is made, for example, by adhesive bonding or soldering. As a result, the yield and efficiency of the device may be reduced.

[0006] The present invention aims to mitigate such drawbacks, make the manufacture of multi-junction PV panels less expensive, and enhance the reliability of photovoltaic panels.

[0007] A known method of interconnecting photovoltaic strips with a flexible plastic tape therebetween is disclosed in Patent Document 1.

Prior Art Documents

Non-Patent Documents

[0008]

Non-Patent Document 1

[2017] on p.164

Patent Document

[0009]

Patent Document 1

Summary of the Invention

[0010] The present invention alleviates these drawbacks by the subject matter of the claims defined herein. Further advantages of the present invention are explained in more detail in the following sections.

[0011] According to a first aspect of the present invention, a multi-junction photovoltaic device as claimed in claims 1 to 11 is provided. According to a second aspect of the present invention, a photovoltaic panel having a plurality of multi-junction devices according to the first aspect connected in series as claimed in claims 12 and 13 is provided. According to a third aspect of the present invention, a method for manufacturing a multi-junction photovoltaic device as claimed in claim 14 is provided.

[0012] Preferred embodiments of the monolithic integrated multi-junction photovoltaic device according to the present invention and other aspects of the present invention are described in the following description and claims.

Brief Description of the Drawings

[0013] Hereinafter, embodiments of the present invention will be described by way of example only with reference to the attached schematic diagrams:

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Figure 1A

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DETAILED DESCRIPTION OF THE INVENTION

[0032] For a more complete understanding of the present invention, reference is now made to the following description of its exemplary embodiments:

[0033] Monolithic Integrated Multi-Junction Photovoltaic Device In the first embodiment, the present invention relates to a monolithic integrated multi-junction photovoltaic device having a first sub-cell and a second sub-cell that is in electrical contact with the first sub-cell, the second sub-cell covering the first sub-cell and configured such that incident light reaches the first sub-cell in use through the second sub-cell, the surface of the second sub-cell having a light-receiving surface having a layer of a light-transmissive conductive material and one or more metal tracks that are in contact with the layer of the light-transmissive conductive material and extend in a first direction, a layer of an electrically insulating material being provided on the light-receiving surface of the second sub-cell that extends under one end of one or more of the metal tracks at an end of the multi-junction cell, and a conductive pad being provided on the layer of the electrically insulating material and in electrical contact with one or more of the metal tracks to provide electrical contact to an external circuit.

[0034] Advantageously, the absence of the light-transmissive conductive material and / or the presence of the layer of the electrically insulating material on the light-receiving surface under the pad significantly reduces the risk of short circuits typically observed during the application of lamination pressure in subsequent bonding and / or encapsulation.

[0035] The light-transmissive conductive material may be under the entire layer of the electrically insulating material, but it is preferred that the edge of the multi-junction cell is left uncoated with the light-transmissive conductive material such that the electrically insulating material is provided adjacent to or only partially overlaps the light-transmissive conductive material. In other words, it is preferred that the layer of the light-transmissive conductive material does not exist under the layer of the electrically insulating material, or that the layer of the electrically insulating material overlaps the edge of the layer of the light-transmissive conductive material on the light-receiving surface, such that the mechanical and thermal stresses at the interface (contact surface) between the conductive pad and the metal track are separated from the tandem active region.

[0036] The light-transmissive conductive material used in the present invention preferably has a light transmittance of 50% to 90% or 95%, more preferably at least 80%, measured between wavelengths of 250 nm and 750 nm, and a resistivity of 10 -2 Ω·cm or less (according to ASTM B193-16).

[0037] Typically used materials are transparent conductive oxides (TCOs) such as, for example, SnO2 doped with Sb or F (ATO or FTO), ZnO doped with Al (AZO) or Ga, and In2O3 doped with Sn (ITO). Alternatively, carbon nanotubes, silver nanowires or graphene films may be used. The thickness of the optically transparent conductive material layer can be appropriately selected by those skilled in the art depending on the material used. For example, when a transparent conductive oxide is used as the optically transparent conductive material, a typical thickness ranges from 50 to 200 nm.

[0038] The electrical insulating material used in the present invention is not particularly limited, but materials having a volume resistivity exceeding 10 10 Ω·cm (which can be determined, for example, in accordance with ASTM D257) and a coefficient of thermal expansion between 1 and 100 ppm / K (by thermomechanical analysis) are preferred.

[0039] In a preferred embodiment, the electrical insulating material is optically transparent, i.e., exhibits an average transmittance for at least 90% of visible light, which potentially enables the extension of the tandem active region when the optically transparent conductive material is present under the layer of the electrical insulating material.

[0040] In a particularly preferred embodiment, the electrical insulating material is one or more of silicon oxide, silicon oxynitride, silicon nitride, alumina and crosslinked polymers (including, but not limited to, epoxy-based polymers, silicone-based polymers, polyimides, acrylate-based polymers and copolymers thereof). In a particularly preferred embodiment from the viewpoint of easy manufacturing, the electrical insulating material includes a photocrosslinkable polymer. The thickness of the electrical insulating material layer is not particularly limited, but typically ranges between 0.5 and 300 μm, preferably between 1 and 100 μm. The electrical insulating material is preferably elastic, so that when the module is arranged in a shingled configuration within the module, the module can easily withstand temperature gradients that cause shear forces due to mechanical shock or differential expansion.

[0041] One or more metal tracks in contact with the layer of the optically transparent conductive material are typically ribbons or deposited layers comprising or consisting of one or more highly conductive metals (such as copper, silver or aluminum) or metal alloys. In a preferred embodiment, one or more metal tracks are formed by the deposition of a metallization paste (such as a silver paste with 70 - 95% Ag loading) and subsequent drying. Typical dimensions of the metal tracks range from 10 to 100 μm in width, preferably 25 to 60 μm, and from 1 to 30 μm in height, preferably between 5 and 17 μm.

[0042] In the monolithic integrated multi - junction photovoltaic device according to the present invention, a conductive pad is provided on a layer of an electrically insulating material and is in electrical contact with one or more metal tracks to provide electrical contact to an external circuit. For this purpose, the conductive pad may extend beyond the surface of the electrically insulating material layer and / or the upper surface of the multi - junction device. The material used for the conductive pad exhibits a low resistivity (preferably 10 -1 Ω·cm or less, more preferably 10 -2 Ω·cm or less resistivity) and is not particularly limited as long as it enables bonding for stringing applications. Although not limited thereto, preferred materials include solders (such as metals or metal alloys such as Sn / Pb 60 / 40, Sn / Pb / Ag 62 / 36 / 2 or Sn / Ag 96.5 / 3.5 alloys) to which a flux can be added to prevent oxidation. Alternatively, when a low - temperature process is desired (such as when using a heat - sensitive perovskite formulation), a conductive adhesive, or even a thickness or z - axis ranging from 0.5·10 -4 ~50·10 -4It is preferable to use an isotropic or anisotropic conductive adhesive (paste or tape) having a resistivity of Ω·cm, and ideally enabling a peel strength exceeding 1 Nmm. Exemplary conductive adhesives may include crosslinkable polymers (such as epoxy, silicone or acrylate) filled with conductive particles (such as metal particles). The thickness of the conductive pad can be appropriately selected by those skilled in the art according to the material, geometric shape and desired bonding properties. For example, a typical solder thickness ranges from 5 to 100 μm, preferably from 10 to 50 μm. The typical thickness of a pad made of a conductive adhesive ranges from 20 to 300 μm, preferably from 30 to 200 μm.

[0043] As used herein, the term "conductive pad" can refer to a pad on a metal track (in the case of a shingle stringing arrangement) or a metal ribbon attached to a metal track (in the case of a conventional stringing arrangement). Thus, examples of "conductive pads" can include: a) a metal ribbon joined (to a metal track) with a conductive adhesive (for a conventional string); b) a metal ribbon joined (to a metal track) with solder (for a conventional string); c) only a conductive adhesive pad (for shingling); and d) only a solder pad (for shingling).

[0044] Generally, the specific configurations of the first sub-cell and the second sub-cell are not particularly limited, and it is understood that each of them may include a plurality of sub-layers, similar to one or more intermediate layers provided between the first sub-cell and the second sub-cell.

[0045] Exemplary intermediate layers may include, for example, transparent conductive oxides (including indium tin oxide (ITO) or aluminum-doped zinc oxide (AZO), etc.), carbon (such as graphene), and an interconnecting layer containing metal nanowires. Preferably, the ITO interconnecting layer has a thickness of 10 nm to 60 nm, more preferably about 30 to 55 nm.

[0046] In a preferred embodiment, the second sub-cell comprises a layer of perovskite material.

[0047] As used herein, the term "perovskite" refers to a material having a three-dimensional crystal structure related to that of CaTiO3, or a material comprising a layer of a material, the layer having a structure related to that of CaTiO3, with the former being preferred. As is known to those skilled in the art, perovskites can generally be represented by the chemical formula ABX3, where A and B are cations of different sizes and X is an anion, or can generally be represented by the chemical formula [A][B][X]3, where [A] is at least one cation, [B] is at least one cation, and [X] is an anion. Preferred perovskite materials are photosensitizing materials, i.e., materials capable of both light generation and charge transport. In a further preferred embodiment, the perovskite material comprises one or more cations selected from organic cations and cesium or rubidium cations, one or more of Pb, Sn or Ti, and one or more halide anions selected from Cl, Br and I.

[0048] A perovskite material can be a perovskite that acts as an n-type electron transport semiconductor when photo-doped. Alternatively, it can be a perovskite that acts as a p-type hole transport semiconductor when photo-doped. Thus, the perovskite can be n-type or p-type, or it can be an intrinsic semiconductor. In a preferred embodiment, the perovskite used is one that acts as an n-type electron transport semiconductor when photo-doped. The perovskite material can exhibit ambipolar charge transport and thus can act as both an n-type and a p-type semiconductor. In particular, the perovskite can act as both an n-type and a p-type semiconductor depending on the type of junction formed between the perovskite and the adjacent material. Exemplary perovskite materials that can be used include, but are not limited to, those disclosed in, for example, Kojima, A. et al., Journal of the American Chemical Society 2009, 131(17), pp. 6050-1; Zuo, C. et al., Adv. Sci. 2016, 3, 1500324; WO2013 / 171517A1; WO2014 / 045021A1; and WO2016 / 198898A1.

[0049] When the second sub-cell includes a perovskite material, the layer including the perovskite material is preferably sandwiched between an n-type region including at least one n-type layer and a p-type region including at least one p-type layer, thus providing a p-i-n or n-i-p sub-cell architecture.

[0050] As used herein, the term "n-type" refers to a region, layer, or material that includes an extrinsic semiconductor having a higher electron concentration than hole concentration. Thus, in an n-type semiconductor, electrons are the majority carriers and holes are the minority carriers, and thus they are electron transport materials. Accordingly, the term "n-type region", as used herein, refers to a region of one or more electron transport (i.e., n-type) materials. Similarly, the term "n-type layer" refers to a layer of an electron transporting (i.e., n-type) material. The electron transport material (i.e., n-type) can be a single electron transport compound or elemental material, or a mixture of two or more electron transport compounds or elemental materials known in the art. The electron transporting compound or elemental material may or may not be doped, or may be doped with one or more dopant elements. By way of non-limiting example, exemplary n-type materials can be selected from metal oxides, metal sulfides, metal selenides, metal tellurides, amorphous Si, n-type group-IV semiconductors, n-type group-III-V semiconductors, n-type group-II-VI semiconductors, n-type group-I-VII semiconductors, n-type group-IV-VI semiconductors, n-type group-V-VI semiconductors, and n-type group-II-V semiconductors, any of which may be doped or undoped. Examples thereof include oxides of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, cadmium, or a mixture of two or more of the foregoing metals; sulfides of cadmium, tin, copper, zinc, or a mixture of two or more of the foregoing metals; selenides of cadmium, zinc, indium, gallium, or a mixture of two or more of the foregoing metals; or n-type materials selected from tellurides of cadmium, zinc, cadmium or tin, or a mixture of two or more of the foregoing metals. Alternatively, C 60 or C 70 Fullerene or fullerene derivative materials can be used to form the n-type region.

[0051] As used herein, the term "p-type" refers to a region, layer, or material that includes an extrinsic semiconductor having a hole concentration greater than that of electrons. In a p-type semiconductor, holes are the majority carriers and electrons are the minority carriers, so it is a hole transport material. Thus, as used herein, the term "p-type region" refers to a region of one or more hole transport (i.e., p-type) materials. Similarly, the term "p-type layer" refers to a layer of hole transport (i.e., p-type) materials. The hole transport material (i.e., p-type) can be a single hole transport compound or elemental material, or a mixture of two or more hole transport compounds or elemental materials known in the art. The hole transport compound or elemental material may or may not be doped, or may be doped with one or more dopant elements.Exemplary p-type compounds include, but are not limited to, spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine) 9,9'-spirobifluorene), TNATA (4,4',4”-tris-(N-(naphthalen-2-yl)-N-phenylamine) triphenylamine), BPAPF (9,9-bis[4-(N,N-bis-biphenyl-4-yl-amino)phenyl]-9H-fluorene), spiro-NPB (N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9,9'-spirobi[9H-fluorene]-2,7-diamine), 4P-TPD (4,4-bis-(N,N-diphenylamino)-tetraphenyl), P3HT (poly(3-hexylthiophene)), PCPDTBT (poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4b']dithiophene-2,6-diyl]]), PVK (poly(N-vinylcarbazole)), HTM-TFSI (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), Li-TFSI (lithium bis(trifluoromethanesulfonyl)imide), tBP (tert-butylpyridine), m-MTDATA (4,4',4”-tris(methylphenylphenylamino)triphenylamine), MeOTPD (N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine), BP2T (5,5'-di(biphenyl-4-yl)-2,2'-bithiophene), di-NPB (N,N'-di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl)-4,4'-diamine), α-NPB (N,N'-di(naphthalen-1-yl)-N,N'-diphenylbenzidine, and PEDOT:PSS. The p-type layer may further include a dopant such as, for example, tert-butylpyridine, LiTFSI or nitrosonium tetrafluoroborate.

[0052] The p-type layer may further include oxides of nickel, vanadium, copper or molybdenum; CuI, CuBr, CuSCN, Cu2O, CuO or CIS; perovskite; amorphous Si; p-type group-IV semiconductors, p-type group-III-V semiconductors, p-type group-II-VI semiconductors, p-type group-I-VII semiconductors, p-type group-IV-VI semiconductors, p-type group-V-VI semiconductors, and p-type group-II-V semiconductors, which may be doped or undoped inorganic hole transporters, respectively.

[0053] In another preferred embodiment, the first sub-cell has a smaller band gap than the second sub-cell. More preferably, the first sub-cell includes single crystal silicon, polysilicon, CdTe, Cu(In,Ga)Se2 or Cu2ZnSn(S,Se)4 sub-cells, or perovskite sub-cells (the band gap of which is smaller than that of the second sub-cell).

[0054] To optimize the harvesting of the solar spectrum, the second sub-cell preferably includes a perovskite material having a band gap of 1.50 eV to 1.75 eV, more preferably 1.65 eV to 1.70 eV, and the first sub-cell preferably has a band gap of 1.05 eV to 1.15 eV, more preferably about 1.1 eV. The term "band gap" as used herein refers to the energy difference between the top of the valence band and the bottom of the conduction band of a material, which can be determined by those skilled in the art without undue experimentation.

[0055] It should be noted that a monolithic integrated multi-junction photovoltaic device may include two or more sub-cells as long as the individual sub-cells are electrically connected in series between a single terminal pair (i.e., conductive pads). Examples of triple sub-cell structures include, but are not limited to, a double-sided monolithic integrated multi-junction photovoltaic device including an upper sub-cell (second sub-cell) including a photoactive region including a perovskite material, an intermediate sub-cell (first sub-cell) including a silicon heterojunction (SHJ), and a bottom sub-cell including a photoactive region including a perovskite material.

[0056] An example of a monolithic integrated multi-junction photovoltaic device is shown in FIGS. 2A and 2B, showing a monolithic integrated structure including a first sub-cell (11b) covered by a second sub-cell (11a). On the upper part of the second sub-cell (11a), i.e., on the light-receiving surface side, a layer of a light-transmissive conductive material (12) is provided on a part of the light-receiving surface (as shown in FIGS. 2A and 2B). Alternatively, the light-transmissive conductive material (12) may be provided over the entire light-receiving surface (not shown). The multi-junction cell (11) further has an electrically insulating material (16) at its ends. In addition, at least one metal track (13) is provided in contact with the layer of the light-transmissive conductive material (12) and extending in a first direction (i.e., parallel to the B-B' axis), and one end of the metal track (13) is disposed on the electrically insulating material (16). In a preferred embodiment, the monolithic integrated multi-junction photovoltaic device has a plurality of metal tracks spaced apart from each other and extending in the first direction (not shown in FIGS. 2A and 2B). Without being limited thereto, the electrically insulating material (16) extends in a direction perpendicular to the first direction (i.e., the B-B' axis) and parallel to the light-receiving surface, as shown in FIG. 2A. Finally, a conductive pad (14) is provided on the layer of the electrically insulating material (16) and is in electrical contact with the metal track (13) to provide electrical contact to an external circuit. Optionally, a second conductive pad (15) may be provided on the bottom surface of the multi-junction cell.

[0057] In the conventional devices of FIGS. 1A and 1B, the region where the conductive pad (4) is joined to the metal track (3) is directly above the light-transmissive conductive material (2), and the metal track (3) is in direct contact with it. Therefore, the joining process involving high temperatures must be avoided to prevent damage to the light-receiving surface, which severely limits the choice of joining technology and the resulting quality of the joints. In contrast, in the present invention, as shown in FIGS. 2A and 2B, an electrically insulating material (16) is provided below the metal track (13) at the portion where the conductive pad (14) is joined, and thus functions as a heat buffer. Therefore, a wide range of techniques can be used for joining the conductive pad (14) to the metal track (13), including soldering methods at high temperatures (above 300 °C). A further advantage is that during aging, the thermal stress (shearing) at the interface between the conductive pad (14) and the metal track (13) is away from the tandem active region. Therefore, the monolithic integrated multiple-junction photovoltaic device according to the present invention exhibits improved performance and reliability.

[0058] Photovoltaic panel In a second embodiment, the present invention relates to a photovoltaic panel having a plurality of multiple-junction photovoltaic devices according to the above-described first embodiment, arranged in a row on a substrate and electrically connected in series to each other via the conductive pads.

[0059] In a preferred embodiment, the multi-junction photovoltaic devices are arranged in overlapping rows such that the pads on one device contact the rear contacts of the adjacent devices. For example, by using the configuration according to FIGS. 2A and 2B, the pad contact can be established by bonding the lower conductive bond pad (15) of one device to the upper conductive bond pad (14) of the adjacent device. Alternative preferred embodiments are shown in FIGS. 3A - 3C. Here, the lower conductive bond pads are omitted. The plurality of multi-junction photovoltaic devices according to FIGS. 3A and 3B can then be directly connected to each other, preferably using a conductive adhesive for the conductive pads, such that the back of the upper cell contacts the conductive pads (24) on the front of the lower cell (see FIG. 3C), thereby providing a singulated configuration. The maximum overlap between the two connected cells is preferably limited to the width of the strip of insulating material.

[0060] One or more glass substrates and / or transparent polymer substrates can be used to cover the back and front of the photovoltaic panel. In addition, the photovoltaic panel can be sealed (e.g., at the corner portions) using a sealing material and / or a sealing member known in the art. Depending on the application, the photovoltaic panel may optionally include mounting members (e.g., mounting plates or the like) and / or height / angle adjustment supports.

[0061] Method for manufacturing a monolithic integrated multi-junction photovoltaic device In a third embodiment, the present invention relates to a method of manufacturing a monolithic integrated optical device, the method comprising: (a) a step of providing a first photovoltaic sub-cell; and (b) a step of providing a second sub-cell on the first sub-cell and in electrical contact with the first sub-cell, wherein a light-receiving surface of the second sub-cell has a layer of a light-transmissive conductive material on most of an upper surface of the second sub-cell; (c) a step of providing a layer of an electrically insulating material on a minority (preferably one edge region) of the upper surface of the second sub-cell; (d) a step of providing an elongated electrical contact on the light-receiving surface, the contact extending over both the layer of the light-transmissive conductive material and the layer of the electrically insulating material; and (e) a step of providing a conductive pad on the upper part of the layer of the electrically insulating material and in electrical contact with the elongated electrical contact to provide electrical contact to an external circuit.

[0062] In this regard, the term "most" indicates more than 50% of the surface, preferably more than 60%, particularly preferably more than 70%, and especially preferably between 80% and 98%, while the term "minority" indicates less than 50% of the surface, preferably less than 40%, particularly preferably less than 30%, and especially preferably between 2% and 20%. In a preferred embodiment, step (b) is performed such that a region of the light-receiving surface (particularly preferably an edge region) does not have a layer of the light-transmissive conductive material. In a further preferred embodiment, the layer of the electrically insulating material is provided in step (c) in the region of the light-receiving surface that does not have the layer of the light-transmissive conductive material.

[0063] In this regard, in step (c), it is preferable that the layer of the electrically insulating material is arranged so as to overlap an edge of the layer of the light-transmissive conductive material.

[0064] Without being limited thereto, depending mainly on the types and structures of the first and second sub-cells, steps (a) and / or (b) are preferably performed by vacuum deposition or solution coating.

[0065] For example, in the case of a two-terminal Si / perovskite tandem cell (using an n-i-p or p-i-n cell architecture), step (a) may include providing a silicon solar cell without a front metallization grid, and step (b) may include: (b1) uniformly providing an n-type (or p-type) contact material on top of the silicon solar cell (e.g., by vacuum evaporation or solution coating); (b2) directly or multi-step depositing a perovskite photoabsorber on top of the n-type (or p-type) contact material (e.g., by vacuum evaporation or solution coating); and (b3) uniformly providing a p-type (or n-type) contact material on top of the silicon solar cell stack of the sub-cell (e.g., by vacuum evaporation or solution coating).

[0066] Although not limited thereto, preferred embodiments of the following steps are shown in FIGS. 4A-4F. Here, a layer of a light-transmissive conductive material (32) is provided on top of the stack of sub-cells (30), and the pattern leaves one narrow strip of the contact material uncoated at one of the edges of the wafer (e.g., by vacuum evaporation or solution coating). When using vacuum evaporation, such a pattern can be created by using a shadow mask. When using solution coating, a photolithography step may be required to mask the p-type contact material where the transparent conductive material should not be deposited (in the case of an n-i-p structure where the p-type material is deposited on top, if a p-i-n configuration is desired, the mask is on the n-type material). A photoresist etching step may then be required (lift-off process). Alternatively, although the embodiment shown in FIG. 4A is preferred, the transparent conductive material may be uniformly deposited over the entire upper surface of the stack of sub-cells (not shown).

[0067] Materials suitable for the light-transmissive conductive material are described above with respect to the first embodiment. When using a transparent conductive oxide, sputtering and chemical vapor deposition are suitable deposition methods. If sputtering is selected, this can be done, for example, with a metal target using a reactive gas or a metal oxide target using an RF power source.

[0068] Thereafter, the electrical insulating material (36) is deposited onto the edge of the pre-patterned cell, preferably with a small overlap between the insulating material (36) and the optically transparent conductive material (32) (see FIG. 4B). Methods suitable for this step include, for example, screen printing. As the electrical insulating material, an inorganic thin film such as a SiO2 or Al2O3 layer can be deposited by a vacuum evaporation method. When a crosslinkable (thermosetting or UV curable) polymer such as an epoxide, acrylate or polyimide is used as the electrical insulating material, these can be deposited, for example, by printing (e.g., screen printing or inkjet printing) or dispensing (e.g., pneumatic dispensing) methods and then cured, if necessary (typically by heating in the temperature range of 100 to 200 °C or by UV irradiation).

[0069] Subsequently, the metal tracks (33) can be deposited onto the cell via, for example, screen printing or plating methods (see FIGS. 4C and 4D). As described above, exemplary materials used for the metal tracks can be metal-filled pastes that further require a drying step at 150 to 400 °C. For heat-sensitive compositions, it is recommended to select a metallization paste with a low drying temperature.

[0070] Thereafter, as shown in FIGS. 4E and 4F, the conductive pad (34) is provided in contact with the metal track (33). Alternatively, a conductive adhesive can be used for singling technology and also for conventional stringing technology when a low temperature process is recommended (e.g., when using a heat-sensitive perovskite composition). When the conductive pad (34) is made of a crosslinkable polymer such as, for example, an epoxy, silicone or acrylate filled with metal particles, a curing step is usually required. Typical curing temperatures are in the range of 100 to 200 °C. In some embodiments, curing of the conductive adhesive can be achieved at a temperature of 140 °C to 160 °C during the module lamination step (e.g., in a singling arrangement). As described above with respect to the first embodiment, additional conductive pads can be provided at the bottom of the device (not shown in FIGS. 4E and 4F), which can be made of, for example, metal, metal alloy (e.g., via screen printing or plating methods), or a conductive adhesive.

[0071] Next, the cells are prepared for top and bottom contacts for a string (e.g., a conventional one using ribbon or singling). For conventional stringing methods (= using a conductive ribbon) and when using a conductive adhesive, the conductive adhesive can be applied onto the cell or ribbon, for example, using an air pressure dispensing method. In addition, the conductive ribbon can be attached to the metal track and the back of the cell using soldering techniques or using a conductive adhesive (which may require automated air pressure dispensing and heat curing). Soldering and dispensing of the conductive adhesive onto the top of the front conductive fingers should be limited to areas coated with an insulating material. For stringing methods that use soldering as the contact method (e.g., when a metal or metal alloy is used for both the top and bottom conductive pads), the ribbon can be supplied already coated with solder. When singling, the maximum overlap between two connected cells should be limited to the width of the strip of insulating material in order to avoid loss of device efficiency.

[0072] It will be appreciated that the preferred features of the various embodiments can be freely combined in any combination, except for combinations in which at least some of the features are mutually exclusive.

[0073] Example Comparative Example 1 In Comparative Example 1, a two-terminal Si / perovskite tandem cell of a conventional design (according to FIGS. 1A and 1B) including an Ag metal track was provided. On the tandem cell, an upper conductive pad was provided using a silver paste to deposit a finger (i.e., a layer with a thickness of 10 μm) with a thickness of 10 μm by screen printing on the central metal track, and the paste was dried in an infrared dryer at 170° C. for 20 minutes. In addition, a bottom conductive pad was provided on the bottom surface of the silicon sub-cell in the same manner. Two wires were used to contact the upper and lower conductive pads, and then the device was sealed. A photograph of the resulting monolithic integrated cell is shown in FIG. 5. The current-voltage characteristics of the device were measured before and after the lamination of the monolithic integration pair of the cells. As shown in FIG. 6, a short circuit was observed in the upper cell during lamination.

[0074] Comparative Example 2 In Comparative Example 2, the same two-terminal Si / perovskite tandem cell as in Comparative Example 1 was used, except that an electrically insulating material in the form of a 25-μm-thick UV-curable epoxy film was provided (see below the T-shaped horizontal line in the photograph of FIG. 7A) and the Ag metal track was extended over the insulating material. The electrically insulating material was deposited by screen printing using a screen with a mesh size of 380 - 460 tpi at a printing speed of 45 mm / s, a squeegee pressure of 3 kg (45° angle), and a printing gap of 0.7 mm. After printing, a UV conveyor curing machine cured the cell at 500 - 1000 mJ / cm using a UV-LED lamp at a wavelength of 395 nm. 2It was used to expose to the UV dose between. The upper conductive pad was provided by using silver paste to deposit a layer with a thickness of 10 μm on the metal track in the area not covered by the insulating material by screen printing (see Fig. 7A), and also by drying the paste at 170 °C for 20 minutes with an infrared dryer. In addition, the lower conductive pad was provided in the same way on the bottom surface of the silicon sub-cell. Two wires were used to contact the upper and lower conductive pads, and the device was sealed. The current-voltage characteristics of the device were measured after lamination.

[0075] Example 1 In Example 1, along with FIGS. 2A and 2B, a two-terminal Si / perovskite tandem cell was adopted as in Comparative Example 2, except that an upper conductive pad (see Fig. 7B) was provided on the electrical insulating layer. Two wires were used to contact the upper and lower conductive pads, and then the device was sealed. The current-voltage characteristics of the device were measured after lamination.

[0076] The current-voltage characteristics of Comparative Example 2 and Example 1 are shown in Fig. 8. As can be seen from the profile of Comparative Example 2, a short circuit is observed and C-V characteristics similar to those of Comparative Example 1 are obtained.

[0077] On the other hand, in Example 1, the short circuit that occurred during the lamination under the upper ribbon was successfully removed by providing the upper conductive pad on the electrical insulating layer.

[0078] These results indicate that the monolithic integrated multiple junction photovoltaic device according to the present invention enables the provision of a photovoltaic panel with improved performance and reliability.

[0079] Given the above disclosure, many other features, modifications, and improvements will be apparent to those skilled in the art.

[0080] The tandem cells can be connected to each other by stringing or singling in a panel including an array of tandem cells.

Description of Reference Numerals

[0081] 1 / 11 / 21 / 31: Monolithic integrated multiple junction photovoltaic device 1a / 11a / 21a: Second sub-cell 2b / 12b / 22b: First sub-cell 2 / 12 / 22 / 32: Light-transmissive conductive material 3 / 13 / 23 / 33: Metal track(s) 4 / 14 / 24 / 34: Upper conductive pad 5 / 15: Optional lower conductive pad 16 / 26 / 36: Electrical insulating material 30: Stack of sub-cells X: Width of tandem active region

Claims

1. A photovoltaic panel having a plurality of monolithic integrated multi-junction photovoltaic devices each having a first sub-cell and a second sub-cell in electrical contact with the first sub-cell, wherein the second sub-cell includes a layer of perovskite material, covers the first sub-cell, and is configured to pass through the second sub-cell such that incident light reaches the first sub-cell in use, the surface of the second sub-cell having a light-receiving surface having a layer of a light-transmissive conductive material and one or more metal tracks in contact with the layer of the light-transmissive conductive material and extending in a first direction, a layer of an electrically insulating material being provided on the light-receiving surface of the second sub-cell extending under one end of one of the one or more metal tracks at an end of the second sub-cell, a conductive pad being provided on the layer of the electrically insulating material and in electrical contact with the one or more metal tracks to provide electrical contact to an external circuit, the layer of the light-transmissive conductive material not being present under at least a part of the layer of the electrically insulating material on the light-receiving surface, the conductive pad including only a conductive adhesive pad or only a solder pad, the plurality of monolithic integrated multi-junction photovoltaic devices being arranged in a row on a substrate and being electrically connected in series with each other in a configuration singling by the conductive pads. A photovoltaic panel.

2. The layer of the electrically insulating material on the light-receiving surface partially overlaps the layer of the light-transmissive conductive material. The photovoltaic panel according to claim 1.

3. Having a plurality of metal tracks spaced apart from each other and extending in the first direction, the electrically insulating material extending perpendicular to the first direction and parallel to the plane of the light-receiving surface. The photovoltaic panel according to claim 1.

4. The first sub-cell includes single crystal silicon, polysilicon, CdTe, Cu(In, Ga)Se2 or Cu2ZnSn(S, Se)4 sub-cell, or a perovskite sub-cell, and the first sub-cell has a smaller bandgap than the second sub-cell. The photovoltaic panel according to any one of claims 1 to 3.

5. The electrically insulating material is light-transmissive. The photovoltaic panel according to any one of claims 1 to 4.

6. The electrically insulating material is one or more of silicon oxide, silicon oxynitride, silicon nitride, alumina and a crosslinked polymer. The photovoltaic panel according to any one of claims 1 to 5.

7. The electrical insulating material is elastic, The photovoltaic panel according to any one of claims 1 to 6.

8. The electrical insulating material includes a photocrosslinkable polymer, The photovoltaic panel according to any one of claims 1 to 7.

9. The second sub-cell further includes a hole transport material layer disposed on one side of the layer of the perovskite material and an electron transport material layer disposed on the other side of the layer of the perovskite material, The photovoltaic panel according to claim 1.

10. The perovskite material includes one or more cations selected from organic cations and cesium or rubidium cations, one or more of Pb, Sn, or Ti, and one or more halide anions selected from Cl, Br, and I, The photovoltaic panel according to claim 1.

11. The monolithic integrated multi-junction photovoltaic device is arranged in overlapping rows such that the conductive pads on one device contact the rear contacts of adjacent devices, The photovoltaic panel according to claim 1.

12. A method for manufacturing a photovoltaic panel having a plurality of monolithic integrated multi-junction photovoltaic devices, the method comprising: (a) providing a first sub-cell; (b) providing a second sub-cell including a layer of perovskite material on top of and in electrical contact with the first sub-cell, wherein a light-receiving surface of the second sub-cell includes a layer of a light-transmissive conductive material on most of the upper surface of the second sub-cell; (c) providing a layer of an electrical insulating material on a minority of the upper surface of the second sub-cell; (d) providing an elongated electrical contact on the light-receiving surface, the elongated electrical contact extending over both the layer of the light-transmissive conductive material and the layer of the electrical insulating material; (e) providing a conductive pad on top of the layer of the electrical insulating material and in electrical contact with the elongated electrical contact, the conductive pad including only a conductive adhesive pad or only a solder pad; The step (b) is performed such that the region of the light-receiving surface does not have the layer of the light-transmissive conductive material; In the step (c), the layer of the electrical insulating material is provided in the region of the light-receiving surface that does not have the layer of the light-transmissive conductive material, and further, the plurality of monolithic integrated multiple junction photovoltaic devices are arranged in a row on a substrate and are electrically connected in series to each other in a configuration singulated by the conductive pads. Method. **Claim 13** In the step (c), the layer of the electrical insulating material is arranged so as to overlap an edge of the layer of the light-transmissive conductive material. The method according to claim 12.

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