Photovoltaic device

Abstract

A photovoltaic device comprising a PIN structure in which a p-type hole transport layer (2) is carried by a substrate (1) and a perovskite layer (3) and an n-type electron transport layer (4) are provided in turn on the p-type layer. A light-transmitting conductive layer (9) is provided on top of the n-type electron transport layer to form a light-receiving top surface. A structure comprising two inorganic electrically insulating layers (6, 8) with a layer of conductive material (7) between them is provided between the n-type electron transport layer and the light-transmitting conductive layer, in which the two inorganic electrically insulating layers comprise a material with a band gap greater than 4.5 eV and the layer of conductive material comprises a material with a band gap less than that of the electrically insulating layers, in which each electrically insulating layer forms a type 1 offset junction with the layer of conductive material.

Description

Technical Field

[0001] This invention relates to photovoltaic (PV) devices, and more particularly to perovskite PV devices and multijunction photovoltaic devices, such as tandem solar cells having perovskite-based sub-cells. Background Technology

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

[0003] Single-junction solar cells—such as those made of silicon pn junctions—have a maximum theoretical efficiency of approximately 29% under AM1.5G conditions (see, for example, “Photovoltaic Solar Energy – from Fundamentals to Applications,” edited by A Reinders et al., Wiley Publishers ISBN 9781118927465

[2017] , p. 164) and a practical efficiency of 26%. However, if cells with materials having higher band gaps are stacked on top of silicon single-junction cells (or other types of single-junction cells) and connected in series, the limiting theoretical efficiency increases to over 40%. Therefore, there is currently great interest in series and other multi-junction cell technologies.

[0004] Furthermore, the efficiency of single-junction perovskite solar cells is comparable to that of silicon.

[0005] Solar cells can have typical or inverted structures. For inverted perovskite solar cells such as those described in this application, developed in a configuration commonly referred to as PIN (layer sequence p-type contact (P), perovskite (I), n-type contact (N)), organic n-type contact materials are typically used. However, such organic materials can be damaged during subsequent layering. This problem can be particularly severe, for example, when a subsequent TCO (transparent conductive oxide electrode) layer is deposited onto the n-type contact by sputtering. To protect the organic n-type contact layer from sputtering damage during the sputtering of subsequent material layers, a denser n-type inorganic contact layer can be deposited immediately after the organic n-type contact layer.

[0006] For example, Bush et al. published in 2017 their use of n-type SnO2 grown by atomic layer deposition (ALD) for electron selection and sputtering protection of organofullerene contacts in inverted PIN perovskite solar cells (10.1038 / nenergy.2017.9). Furthermore, Sahli et al. disclosed a fully textured monolithic perovskite / silicon tandem solar cell in an article published online in Nature Materials on June 11, 2018 (https: / / doi.org / 10.1038 / s41563-018-0115-4). A SnO2 buffer layer was deposited onto the stack via atomic layer deposition.

[0007] A recent review on the use of ALDs in perovskite solar cells has been published—see V. Zardetto, BL Williams, et al., Sustainable Energy & Fuels, Vol. 1, pp. 30–55 (2017). The inverted PIN perovskite device structure is described in more detail in the textbook “Organic-Inorganic Halide Perovskite Photovoltaics” edited by Park, Gratzel, and Miyasaka, Springer (2016) ISBN 978-3-319-35112-4 (see, in particular, Chapter 12, pp. 307–324).

[0008] However, existing technologies have many potential drawbacks, including:

[0009] 1) Process reproducibility: Due to the surface dependence of nucleation in many ALD processes, film thickness may vary from batch to batch. For SnO2, the difference can be as high as 10-15%.

[0010] 2) Due to unpassivated bonds, carrier recombination at the inorganic-n-type / fullerene interface leads to an increase in the open-circuit voltage (V) of the solar cell device. oc ) and fill factor (FF) loss.

[0011] 3) The purpose of the inorganic n-type layer is to protect the organic n-type and perovskite layers from ITO sputtering damage and to prevent the formation of harmful ITO / organic-n-type and ITO / perovskite contact areas. Insufficient density and / or surface coverage of the inorganic layer, or excessively high conductivity, will limit its effectiveness.

[0012] This invention overcomes these shortcomings of the prior art. Summary of the Invention

[0013] According to a first aspect of the present invention, a photovoltaic device is provided.

[0014] Photovoltaic devices comprising multiple interface layers are known from US 9,416,279. However, that patent discloses a typical NIP structure instead of the PIN structure of this invention. The manufacturing process considerations for NIP and PIN structures are different. Sputtering is generally not a problem for NIP structures, but sputtering can damage the material in PIN structures, as described above. This invention relates to inverted perovskite solar cells and provides an inorganic "intrinsic-n-type-intrinsic (INI)" sandwich structure to replace the pure inorganic n-type layer of the prior art described above. When using a single "pure" SnO2 layer, there is greater variability and lower peak and average efficiency compared to using the three-layer stack of this invention.

[0015] For several reasons, the three-layer interface structure of this invention is superior to using a single SnO2 layer. Using a first electrically insulating layer, such as Al2O3, in the stack enables more reproducible growth across the entire stack when using ALD. ALD growth is almost entirely dependent on surface chemistry. The Al2O3 layer acts as a rapid nucleation layer, functionalizing the surface by generating OH surface terminations, thereby aiding the growth of subsequent layers in the stack. Ultimately, including the first layer reduces run-to-run thickness variability.

[0016] The first layer (e.g., Al2O3) can also chemically passivate any free bonds present at the inorganic n / organic n interface, subsequently reducing the density of electron traps available for carrier recombination, thereby reducing the saturation current density and diode ideality factor. This can increase the open-circuit voltage and fill factor.

[0017] Finally, materials such as Al2O3 can act as reservoirs for free radicals. Additional protection against sputtering damage and prevention of ITO / organo-n or ITO / perovskite defect interfaces can reduce the formation of parasitic shunt paths and / or weak diode regions.

[0018] According to a second aspect of the invention, a method for manufacturing a photovoltaic device is provided, wherein two inorganic electrical insulating layers and an intermediate conductive material layer are sequentially deposited onto an n-type electron transport material layer by atomic layer deposition. This deposition is preferably performed at a temperature less than or equal to 125°C. Attached Figure Description

[0019] Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

[0020] Figure 1A A known photovoltaic device is shown in cross-section;

[0021] Figure 1B An exemplary device according to the present invention is shown in cross-section;

[0022] Figure 2 To normalize the measured thickness to the expected thickness graph, the following steps were repeated: a) SnO2 only; and b) Al2O3 / SnO2 / Al2O3;

[0023] Figure 3 A table listing the optimal values ​​and associated ranges for series resistance, ideality factor, and reverse saturation current (from 20 single-junction perovskite devices for each device type) is provided, extracted by fitting a diode model to dark current-voltage data. The V obtained by using a triple layer instead of SnO2 alone is also shown. oc The gain of the photocurrent and the photocurrent voltage (FF) is measured based on the photocurrent-voltage data.

[0024] Figure 4 The shunt resistance R of a perovskite / Si tandem solar cell is shown as a function of the thickness x of the first Al2O3 layer within the ALD three-layer (x nm-Al2O3 / SnO2 / 1 nm-Al2O3) structure. shunt The graph shows the optimal cell and average values ​​for each thickness for 20 devices; and

[0025] Figure 5 The energy level diagram shows a type 1 straddle offset junction. Detailed Implementation

[0026] In one embodiment, the photovoltaic device includes a PIN structure, wherein a p-type hole transport layer is disposed (or carried) on a substrate, a perovskite layer and an n-type electron transport layer are sequentially disposed on the p-type layer, and a light-receiving top surface is formed on top of the n-type electron transport layer. The device is characterized by providing an interface structure between the n-type electron transport layer and the light-receiving conductive layer, which includes two inorganic electrical insulating layers with a conductive material layer between them. The two inorganic electrical insulating layers comprise materials with a band gap greater than 4.5 eV, and the conductive material layer comprises materials with a band gap smaller than that of the electrical insulating layers (e.g., less than or equal to 4.0 eV and greater than 2 eV).

[0027] The substrate advantageously includes additional photovoltaic sub-cells to form a monolithically integrated multi-junction photovoltaic device. These additional photovoltaic sub-cells may include, for example, additional perovskite, monocrystalline silicon, polycrystalline silicon, Cu(In,Ga)Se2, or Cu2ZnSn(S,Se)4 sub-cells.

[0028] Advantageously, the photovoltaic device is a monolithically integrated solar cell, in which the additional sub-cells include a perovskite material layer.

[0029] Preferably, the perovskite material is bipolar. It typically has a three-dimensional crystal structure with the chemical formula ABX3, where A contains one or more organic or inorganic cations (e.g., methylammonium, formamidinium, guanidine, and cesium, rubidium, etc.), B represents one or more divalent metals selected from the group consisting of Pb, Sn, Sb, or Ti, and X represents one or more halide anions selected from, for example, Cl, Br, and I.

[0030] In another embodiment, a photovoltaic device is provided, comprising a Cu(In,Ga)Se2 or Cu2ZnSn(S,Se)4p-n junction including a p-type layer and an n-type layer, and a light-transmitting conductive layer disposed on top of the n-type layer to form a light-receiving top surface. The device is characterized by providing a structure comprising two inorganic electrical insulating layers between the n-type layer and the light-transmitting conductive layer, wherein a conductive material layer is provided between the two inorganic electrical insulating layers, wherein the two inorganic electrical insulating layers comprise materials with a band gap greater than that of the conductive material (e.g., greater than 4.5 eV), and the conductive material layer comprises materials with a band gap smaller than that of the electrical insulating layer (e.g., less than 4.0 eV) and greater than 2 eV.

[0031] Figure 1A A schematic cross-section shows a prior art device stack, while Figure 1B A schematic cross-section of a photovoltaic device according to the present invention is shown. The substrate (1) at the bottom of each stack comprises a material such as glass, and has a TCO layer such as ITO on top, or a bottom sub-cell such as a silicon solar cell. Perovskite / silicon tandem solar cells are described more fully, for example, in Werner et al., Adv. Mater. Interfaces 5, 1700731 (2017).

[0032] Figure 1B An exemplary embodiment of the invention is shown. It can be seen that the bottom (1) of the stack comprises a Si bottom cell or ITO / glass. This is then covered by a p-type layer (2), followed by a perovskite layer (3). The perovskite layer is covered by an organic n-type layer (4). The top of the stack is formed by an ITO layer (9). An inventive three-layer interface structure (6, 7, 8) of the invention exists between the ITO layer and the organic n-type layer.

[0033] The p-type layer (2) comprises a hole transport material, which can be inorganic or organic. On top of the p-type layer is a material with a structure such as MAPbI3 or FA. 0.8 :Cs 0.2 The perovskite layer with a three-dimensional crystal structure of PbI2Br (3). The composition of the perovskite layer can be appropriately selected according to the required band gap of the photosensitive layer.

[0034] A p-type layer is a layer of hole transport (i.e., p-type) material. The p-type material can be a single p-type compound or element, or a mixture of two or more p-type compounds or elements, and it can be undoped or doped with one or more doping elements.

[0035] The p-type layer can include inorganic or organic p-type materials. Typically, the p-type region includes a layer of organic p-type material.

[0036] Suitable p-type materials can be selected from polymers or molecular hole transport agents. The p-type layer used in the photovoltaic device of this invention can, for example, include Spiro-OMeTAD (2,2',7,7'-tetra-(N,N-di-p-methoxyaniline)9,9'-spirodifluorene), P3HT (poly(3-hexylthiophene)), PCPDTBT (poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopentyl[2,1-b:3,4-b']dithiophene-2,6-diyl]]), PVK (poly(N-vinylcarbazole)), HTM-TFSI (1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), Li-TFSI (lithium bis(trifluoromethanesulfonyl)imide), or tBP (tert-butylpyridine). The p-type region can include carbon nanotubes. Typically, p-type materials are selected from spiro-OMeTAD, P3HT, PCPDTBT, and PVK. Preferably, the p-type region consists of a p-type layer containing spiro-MeOTAD.

[0037] The p-type layer can include, for example, spiro-OMeTAD (2,2',7,7'-tetra-(N,N-di-p-methoxyaniline)9,9'-spirodifluorene), P3HT (poly(3-hexylthiophene)), PCPDTBT (poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopentadiene[2,1-b:3,4-b']dithiophene-2,6-diyl]]) or PVK (poly(N-vinylcarbazole)).

[0038] Suitable p-type materials also include molecular hole transporters, polymeric hole transporters, and copolymeric hole transporters. P-type materials can be, for example, molecular hole transport materials, polymers or copolymers comprising one or more of the following moieties: thiophene, phenyl, dithiazolyl, benzothiazolyl, diketopyrrolopyrrole, ethoxydithiophene, amino, triphenylamino, carbazole, ethylenedioxythiophene, dioxythiophene, or fluorene. Therefore, the p-type layer used in the photovoltaic device of the present invention can, for example, include any of the above-mentioned molecular hole transport materials, polymers, or copolymers.

[0039] Suitable p-type materials also include m-MTDATA (4,4',4''-tris(methylphenylphenylamino)triphenylamine), MeOTPD (N,N,N',N'-tetra(4-methoxyphenyl)-biphenyldiamine), BP2T (5,5'-bis(biphenyl-4-yl)-2,2'-bithiophene), di-NPB (N,N'-bis-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl)-4,4'-diamine), α-NPB (N,N'-bis(naphthyl-1-yl)-N,N'-diphenyl) -Benzidine), TNATA (4,4',4''-tri-(N-(naphthyl-2-yl)-N-aniline)triphenylamine), BPAPF (9,9-bis[4-(N,N-bis-diphenyl-4-yl-amino)phenyl]-9H-fluorene), spiro-NPB (N2,N7-di-1-naphthyl-N2,N7-diphenyl-9,9'-spirobis[9H-fluorene]-2,7-diamine), 4P-TPD (4,4-bis(N,N-diphenylamino)-tetraphenyl), PEDOT:PSS and spiro-OMeTAD.

[0040] The p-type layer can be doped with, for example, tert-butylpyridine and LiTFSI. Doping of the p-type layer can increase the hole density. For example, the p-type layer can be doped with NOBF4 (nitroso tetrafluoroborate) to increase the hole density.

[0041] In other examples, the p-type layer may include an inorganic hole transport agent. For instance, the p-type layer may include an inorganic hole transport agent comprising oxides of vanadium, copper, nickel, or molybdenum; CuI, CuBr, CuSCN, Cu2O, CuO, or CIS; perovskite; amorphous silicon; 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, wherein the inorganic material may be doped or undoped. The p-type layer may be a non-porous, dense layer of the inorganic hole transport agent.

[0042] The p-type layer may include, for example, an inorganic hole transporter comprising oxides of nickel, vanadium, copper, or molybdenum; CuI, CuBr, CuSCN, Cu2O, CuO, or CIS; amorphous silicon; 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, wherein the inorganic material may be doped or undoped.

[0043] The p-type region can, for example, have a thickness from 5 nm to 1000 nm. For instance, the p-type region can have a thickness from 50 nm to 500 nm or from 100 nm to 500 nm. In the multi-junction photovoltaic device described above, the p-type region 112 of the first sub-cell preferably has a thickness from 10 nm to 50 nm, and more preferably about 20 nm. The p-type region can also comprise a bilayer or multilayer structure consisting of two or more layers of different materials.

[0044] Perovskite materials can have the general formula (I):

[0045] [A][B][X]3(I)

[0046] Wherein [A] is one or more monovalent cations, [B] is one or more divalent inorganic cations, and [X] is one or more halide anions, preferably comprising one or more halide anions selected from fluorides, chlorides, bromides, and iodides, and more preferably selected from chlorides, bromides, and iodides. More preferably, [X] comprises one or more halide anions selected from bromides and iodides. In some examples, [X] preferably comprises two different halide anions selected from fluorides, chlorides, bromides, and iodides, and more preferably selected from chlorides, bromides, and iodides, and more preferably includes bromides and iodides.

[0047] [A] Preferably contains a compound selected from methylammonium (CH3NH3) + ), formamidin (HC(NH)2)2 + ) and ethylammonium (CH3CH2NH3) + One or more organic cations selected from methylammonium (CH3NH3), and preferably containing methylammonium (CH3NH3). + ) and formamidin (HC(NH2)2 + [A] is an organic cation selected from Cs. + 、Rb + Cu + Pd + Pt + Ag + Au + ,Rh + and Ru + One or more inorganic cations.

[0048] [B] Preferably contains Pb 2+ and Sn 2+ At least one divalent inorganic cation, and preferably containing Pb. 2+ .

[0049] In a preferred example, the perovskite material has the general formula:

[0050] A x A’ 1-x B(X y X’ 1-y )3(IA)

[0051] where A is formamidinium (FA), A' is cesium cation (Cs + ), B is Pb 2+ , X is iodide, X' is bromide, and where 0 < x ≤ 1 and 0 < y ≤ 1. In these preferred embodiments, the perovskite material can thus comprise a mixture of two monovalent cations. In addition, in a preferred embodiment, the perovskite material can thus comprise a single iodide anion or a mixture of iodide and bromide anions. The inventors have found that such perovskite materials can have a band gap of 1.50 eV to 1.75 eV, and that such perovskite material layers can be readily formed with a suitable crystalline morphology and phase. More preferably, the perovskite material is FA 1- x Cs x PbI 3-y Br y .

[0052] To provide an efficient photovoltaic device, it is desirable to maximize the absorption of the absorber to generate an optimum current flow. Thus, when perovskite is used as an absorber in a photovoltaic device or sub-cell, the thickness of the perovskite layer should ideally be on the order of 300 to 600 nm in order to absorb sunlight in most of the visible spectrum. Thus, the thickness of the perovskite material layer is generally greater than 100 nm. The thickness of the perovskite material layer in a photovoltaic device can be, for example, 100 nm to 1000 nm. The thickness of the perovskite material layer in a photovoltaic device can be, for example, 200 nm to 700 nm, and preferably 300 nm to 600 nm. In the above multi-junction photovoltaic device, the planar perovskite material layer 11 in the photosensitive region of the first / top sub-cell 210 preferably has a thickness of 350 nm to 450 nm, and more preferably about 400 nm.

[0053] The perovskite layer can be prepared as described in the following literature: WO2013 / 171517, WO2014 / 045021, WO2016 / 198889, WO2016 / 005758, WO2017 / 089819 and the reference book “Photovoltaic Solar Energy: From Fundamentals to Applications”, edited by Angèle Reinders and Pierre Verlinden, Wiley-Blackwell (2017) ISBN-13: 978-1118927465 and “Organic-Inorganic Halide Perovskite Photovoltaics: From Fundamentals to Device Architectures”, edited by Nam-Gyu Park et al., Springer (2016) ISBN-13:978-3319351124.

[0054] On top of the perovskite layer is an electron transport material layer (4). The electron transport layer suitable for the perovskite photovoltaic cell in this embodiment has recently been described in the review paper “Current status of electron transport layers in perovskite solar cells: materials and properties”, Mahmood, Sarwar and Mehran, RSC Adv. 2017.7.17044.

[0055] The electron transport layer typically comprises an n-type region. In the multi-junction photovoltaic device described above, the n-type region of the first sub-cell comprises one or more n-type layers. Typically, the n-type region is an n-type layer, i.e., a single n-type layer. However, in other examples, the n-type region may include an n-type layer and a separate n-type exciton blocking layer or hole blocking layer.

[0056] An exciton blocking layer is a material with a wider band gap than the photosensitive material, but its conduction band or valence band is closely matched with that of the photosensitive material. If the conduction band (or the lowest unoccupied molecular orbital level) of the exciton blocking layer is closely aligned with the conduction band of the photosensitive material, electrons can enter from the photosensitive material and pass through the exciton blocking layer, or pass through the exciton blocking layer and enter the photosensitive material. This is called an n-type exciton blocking layer. One example of this is bathcuproine (BCP), as described in P. Peumans, A. Yakimov, and SR Forrest, “Small molecular weight organic thin-film photodetectors and solar cells”, J. Appl. Phys. 93, 3693 (2001), and Masaya Hirade and Chihaya Adachi, “Small molecular organic photovoltaic cells with exciton blocking layer at anode interface for improved device performance”, Appl. Phys. Lett. 99, 153302 (2011).

[0057] The n-type layer (4) is an electron transport (i.e., n-type) material layer. The n-type material can be a single n-type compound or element material, or a mixture of two or more n-type compounds or elements materials, which can be undoped or doped with one or more doping elements.

[0058] The electron transport materials used may include inorganic or organic n-type materials.

[0059] Suitable inorganic n-type materials can be selected from metal oxides, metal sulfides, metal selenides, metal tellurides, perovskites, amorphous or nanocrystalline 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 can be doped or undoped.

[0060] More typically, n-type materials are selected from metal oxides, metal sulfides, metal selenides, and metal tellurides.

[0061] Therefore, the n-type layer may comprise an inorganic material selected from oxides of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, or cadmium, or oxides of mixtures of two or more of these metals. For example, the n-type layer may comprise TiO2, SnO2, ZnO, Nb2O5, Ta2O5, WO3, W2O5, In2O3, Ga2O3, Nd2O3, PbO, or CdO.

[0062] Other suitable n-type materials that can be used include sulfides of cadmium, tin, copper, or zinc, including sulfides of mixtures of two or more of the aforementioned metals. For example, the sulfide can be FeS2, CdS, ZnS, SnS, BiS, SbS, or Cu2ZnSnS4.

[0063] The n-type layer may, for example, comprise a selenide of cadmium, zinc, indium, or gallium, or a selenide of a mixture of two or more of said metals; or a telluride of cadmium, zinc, cadmium, or tin, or a telluride of a mixture of two or more said metals. For example, the selenide may be Cu(In,Ga)Se2. Typically, the telluride is a telluride of cadmium, zinc, cadmium, or tin. For example, the telluride may be CdTe.

[0064] The n-type layer may, for example, comprise the following inorganic materials: oxides selected from titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, cadmium, or oxides of mixtures of two or more of the aforementioned metals; sulfides of cadmium, tin, copper, zinc, or sulfides of mixtures of two or more of the aforementioned metals; selenides of cadmium, zinc, indium, gallium, or selenides of mixtures of two or more of the aforementioned metals; or tellurides of cadmium, zinc, cadmium, or tin, or tellurides of mixtures of two or more of the aforementioned metals.

[0065] Other examples of semiconductors that might be suitable n-type materials (e.g., if they are n-doped) include group IV elemental or compound semiconductors; amorphous silicon; group III-V semiconductors (e.g., gallium arsenide); group II-VI semiconductors (e.g., cadmium selenide); group I-VII semiconductors (e.g., cuprous chloride); group IV-VI semiconductors (e.g., lead selenide); group V-VI semiconductors (e.g., bismuth telluride); and group II-V semiconductors (e.g., cadmium arsenide).

[0066] When the n-type layer is an inorganic material, such as TiO2 or any other material listed above, it can advantageously be a dense layer of said inorganic material. Preferably, the n-type layer is a dense TiO2 layer.

[0067] Other n-type materials may also be used, including organic and polymeric electron transport materials, as well as electrolytes. Suitable examples include, but are not limited to, fullerenes or fullerene derivatives, organic electron transport materials containing dinaphthalene or derivatives thereof, or poly{[N,NO-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,50-(2,20-dithiophene)}(P(NDI2OD-T2)). For example, the n-type region may include an n-type layer comprising one or more of C60, C70, C84, C60-PCBM, C70-PCBM, C84-PCBM, and carbon nanotubes. It may contain C60-IPB, C60-IPH, C70-IPB, C70IPH, or mixtures thereof. Such materials are commercially available from Solenne BV, 6 Zernikepark 9747AN, Groningen, Netherlands.

[0068] The n-type region can have a thickness ranging from 3 nm to 1000 nm. In the case where the n-type region includes a dense layer of n-type semiconductor, the thickness of the dense layer is from 3 nm to 200 nm.

[0069] The interface structure (6, 7, 8) of the present invention includes a conductive material (7) sandwiched between two electrically insulating layers (6, 8). The two electrically insulating layers comprise materials with a suitable band gap greater than 4.5 eV. Each electrically insulating layer does not need to contain the same material, although preferably, both layers do contain the same material. A wide band gap is important. This material provides passivation of the band gap states introduced by the underlying n-type region and the upper conductive layer (such as SnO2).

[0070] An example of the interface structure according to the present invention is in Figure 1B As shown, two inorganic electrical insulating layers (6, 8) are deposited on an n-type layer (4), each comprising a material having a band gap greater than 4.5 eV, and a conductive material layer (7) therebetween, preferably comprising a material having a band gap of less than 4.0 eV and greater than 2 eV. The electrical insulating layers are preferably deposited by atomic layer deposition (ALD).

[0071] like Figure 5 As shown, the conductive material layer forms a cross-type -1 offset junction with each electrically insulating layer. In this figure:

[0072] E g-A >W g-B

[0073] E C-A >E C-B

[0074] E V-A <E V-B

[0075] The electrical insulating layers (6, 8) are formed of a material with a band gap greater than 4.5 eV, preferably greater than 5, 5.5, 6, 6.5, or 7 eV. Suitable materials include Al2O3 and LiF. The most preferred material is Al2O3.

[0076] The electrical insulating layer forms conduction band and valence band barriers at the interface with the adjacent layer, generating a type I heterojunction at these locations.

[0077] Preferably, each electrical insulating material layer has a thickness in the range of 0.1-10 nm, more preferably 0.4-3 nm, and most preferably about 1 nm thick.

[0078] The conductive layer 7 is formed of a material with a band gap smaller than that of the materials of the electrically insulating layers (6, 8). When each conductive layer is made of a different material, the conductive layer is formed of a material with a band gap smaller than that of both materials. Preferably, the band gap is less than 4.0 eV and greater than 2 eV. Preferably, the conductive layer is formed of a conductive n-type oxide. Suitable materials include SnO. x ZnO x (Zn:Sn)O x TiO x and InO x The most preferred materials are SnO2, ZnO, In2O3 and TiO2.

[0079] The most preferred material for the conductive layer is SnO2. The conductive material layer (7) between the two inorganic insulating layers preferably has a thickness of 3 to 12 nm.

[0080] The band gap is measured using UV-VIS spectroscopy with methods known in the art. When the band gap is wider than, for example, a glass substrate, ellipsometric measurement (extending fully into the UV) can be used to determine the parameter k more accurately. The band gap can then be determined from the Tauc plot generated by k-dispersion.

[0081] The band gap can be measured as described in Part 3 of the paper by Vos et al. in Journal of Vacuum Science & Technology A34, 01A103 (2016).

[0082] A transparent conductive layer (9) is then deposited on top of the n-type electron transport layer to form a light-receiving top surface. This layer typically comprises a sputtered transparent conductive oxide, such as an ITO layer with a thickness of 10 to 200 nm, but other oxides or materials, such as metal nanowires, may be used alternatively or additionally. The chosen thickness is a trade-off between transparency and conductivity.

[0083] The invention will now be illustrated by the following examples.

[0084] Example

[0085] The results presented in this paper are for PIN photovoltaic devices with an inorganic "intrinsic-n-type-intrinsic (INI)" sandwich interface structure, such as... Figure 1B As shown, the INI structure is specifically Al2O3 / SnO2 / Al2O3.

[0086] The Al2O3 layer is 1 nm thick, and the SnO2 layer is 6 nm thick, including SnO deposited by ALD. 2。

[0087] For thermal ALD of Al2O3, the substrate was maintained at 80–120ºC. TMA and H2O were stored in separate stainless steel containers at room temperature, and the ALD sequence was TMA-dose / TMA-purge / H2O-dose / H2O-purge.

[0088] For SnO x Thermal ALD was performed with the substrate maintained at 80–120ºC. TDMASn and H2O were stored in separate stainless steel containers at 60ºC and room temperature, respectively, with the ALD sequence being TDMASn-doping / TDMASn-purge / H2O-doping / H2O-purge.

[0089] The growth per cycle for Al2O3 and SnO2 layers is 0.1-0.12 nm and 0.12-0.14 nm, respectively. The number of cycles is appropriately selected to produce the desired thickness.

[0090] The entire stack was deposited using thermal ALD to ensure thickness control and film completion for each component of the stack. H2O was used as a co-reactant in the SnO2 and Al2O3 processes. TDMASn and TMA were used as their respective metal precursors. A series of experiments were then conducted on the stack of the present invention and on stacks corresponding to those in the prior art, including stacks that replaced three SnO2 layers. The stacks were otherwise identical.

[0091] Example 1: Measured thickness

[0092] Figure 2 The measured thickness was normalized to a graph of the expected thickness for repeated measurements of: a) SnO2 only; b) Al2O3 / SnO2 / Al2O3, demonstrating reduced batch-to-batch variability achieved with three layers compared to a single layer. This is attributed to the first Al2O3 layer serving to promote nucleation of the SnO2 layer.

[0093] Thickness was measured from Si check samples using elliptic polarization spectroscopy, the Si check samples being included in the deposition run of the perovskite apparatus. The measured thickness is correlated with the nominal thickness, which is set by the number of ALD cycles used. Thickness was measured using a Woollam M2000 ellipticmeter. A generalized oscillator model consisting of a single Tauc-Lorentz oscillator was used to describe the complex dielectric function, thus fitting the raw psi-delta dispersion data. Fitting parameters extracted from the Tauc-Lorentz oscillator were used to construct the n and k dispersions. After data fitting, n@632nm is between 1.8 and 1.85.

[0094] Example 2: Series resistance, ideality factor, and reverse saturation current

[0095] When using the structure of this invention, current-voltage (IV) curves are constructed and the improved diode parameters are demonstrated. Measurements are performed using a Keithley source meter. Initially, the JV curve is generated and fitted to an equivalent circuit of a single-diode solar cell to extract n (ideality factor), J0 (reverse saturation current), and R. s (Series resistance). V oc FF, etc., were obtained from JV measurements of AM1.5 lighting.

[0096] Figure 3 A table listing the optimal values ​​and associated ranges for series resistance, ideality factor, and reverse saturation current (from 20 single-junction perovskite devices for each device type) is provided, extracted by fitting a diode model to dark current-voltage data. The V obtained by using a triple layer instead of SnO2 alone is also shown. oc The gain of the photocurrent and the photocurrent voltage (FF) were measured based on the photocurrent-voltage data.

[0097] Figure 3 The device parameters listed, including the ideality factor (n) and saturation current (J0), decrease due to the inclusion of the INI structure, indicating reduced recombination. Open-circuit voltage and FF enhancement are also observed. When a logarithmic plot of the dark IV curves is constructed, they show a reduction in parasitic shunt current.

[0098] Example 3: Shunt resistor

[0099] In this experiment, the importance of the thickness of the first Al2O3 layer, which varies between 0 and 2 nm, was demonstrated. Optical IV measurements were obtained using a Keithley source meter and AM1.5 illumination. The shunt resistance was taken as the reciprocal of the JV gradient under short-circuit conditions.

[0100] Figure 4The shunt resistance R of a perovskite / Si tandem solar cell is shown as a function of the thickness x of the first Al2O3 layer within the ALD three-layer (x nm-Al2O3 / SnO2 / 1 nm-Al2O3) structure. shunt .

[0101] Experiments were conducted on two different bottom cell wafer types, on which inverted perovskite top cells were deposited. Device efficiency, fill factor, and shunt resistance all increased with increasing Al2O3 thickness.

[0102] Figure 4 The graph shows the optimal cell and average values ​​for each thickness across 20 devices. The experiment was conducted twice, and results from both batches are shown, demonstrating a consistent positive trend—particularly for the best-performing devices.

Claims

1. A photovoltaic device, comprising a PIN structure, wherein a p-type hole transport layer is supported by a substrate, a perovskite layer and an n-type electron transport layer are sequentially disposed on the p-type layer, and a light-transmitting conductive layer is disposed on top of the n-type electron transport layer to form a light-receiving top surface, characterized in that, An interface structure is provided between an n-type electron transport layer and a transparent conductive layer, comprising two inorganic electrical insulating layers with a conductive material layer between them, wherein the two inorganic electrical insulating layers comprise materials with a band gap greater than 4.5 eV, and the conductive material layer comprises materials with a band gap smaller than that of the electrical insulating layers, wherein each electrical insulating layer and the conductive material layer form a type I offset junction.

2. The photovoltaic device according to claim 1, wherein, The conductive material layer comprises a material with a band gap of less than or equal to 4.0 eV and greater than 2 eV.

3. The photovoltaic device according to claim 1 or 2, wherein, The substrate includes additional photovoltaic cells to form a monolithically integrated multi-junction photovoltaic device.

4. The photovoltaic device according to claim 1, wherein, The two inorganic electrical insulating layers include Al2O3.

5. The photovoltaic device according to claim 1, wherein, The conductive material layer between the two inorganic electrical insulating layers comprises one or more materials selected from the group consisting of: SnO x ZnO x ;(Zn:Sn)O x TiO x and InO x .

6. The photovoltaic device according to claim 5, wherein, The conductive material layer between the two inorganic electrical insulating layers includes SnO. x .

7. The photovoltaic device according to claim 3, wherein, The additional photovoltaic sub-cells include perovskite, monocrystalline silicon, polycrystalline silicon, Cu(In,Ga)Se2, or Cu2ZnSn(S,Se)4 sub-cells.

8. The photovoltaic device according to claim 1, wherein, The perovskite layer contains one or more cations selected from organic cations and cesium cations, one or more of Pb, Sn, Sb or Ti, and one or more halide anions selected from Cl, Br and I.

9. The photovoltaic device according to claim 1, wherein, The two inorganic electrical insulating layers have a thickness between 0.4 and 3 nm.

10. The photovoltaic device according to claim 1, wherein, The conductive material layer between the two inorganic electrical insulating layers has a thickness between 3 and 12 nm.

11. A method for manufacturing a photovoltaic device according to any one of the preceding claims, wherein, Two inorganic electrical insulating layers and an intermediate conductive material layer are sequentially deposited onto an n-type electron transport material layer using atomic layer deposition.

12. The method according to claim 11, wherein, Atomic layer deposition is performed at a temperature of 125°C or less.

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