Solar laminated cell, preparation method thereof and photovoltaic module

Abstract

The invention provides a solar laminated cell, a preparation method thereof and a photovoltaic module. The solar laminated cell comprises a bottom cell, a composite layer and a top cell which are arranged in a laminated manner, the composite layer comprises a plurality of functional layers which are arranged in a stacked manner; the work functions of the multiple functional layers increase progressively in the direction from the bottom cell to the top cell. The composite layer composed of the multiple functional layers is arranged between the bottom cell and the top cell of the solar laminated cell, the work function of the multiple functional layers increases progressively in the direction from the bottom cell to the top cell, so that continuous transition of energy band structures of the multiple functional layers is achieved, energy level matching between the top cell and the bottom cell is optimized through the design, and the performance of the solar laminated cell is improved. According to the invention, the interface potential barrier can be effectively reduced, the extraction and transmission of carriers can be promoted, the interface recombination loss can be inhibited, the open-circuit voltage and fill factor of the solar laminated cell can be improved, and the photoelectric conversion efficiency of the solar laminated cell can be finally improved.

Description

Technical Field

[0001] This application relates to the field of solar tandem battery technology, specifically to a solar tandem battery, its preparation method, and a photovoltaic module. Background Technology

[0002] With the improvement of my country's energy structure, more and more new energy sources are replacing traditional thermal power generation. Among them, solar energy is a renewable energy source. Solar power generation is simple to install, requires little site space, and is suitable for various occasions and needs. Therefore, it is widely used in various fields.

[0003] Perovskite solar cells (PSCs) represent a new generation of photovoltaic technology, attracting significant research attention due to their high photoelectric conversion efficiency and low-cost solution processing. With the evolution of photovoltaic technology, the need to break the Schockley-Queisser limit to achieve even higher photoelectric conversion efficiency has spurred the rapid development of tandem solar cells.

[0004] However, there is still a significant gap between the efficiency of current perovskite / crystalline silicon tandem solar cells and the theoretical limit. Therefore, further optimizing the cell structure design and improving the fabrication quality of each functional film layer will be the core task and key direction for pushing solar cell efficiency to new heights in the future.

[0005] In perovskite / crystalline silicon tandem solar cells, the intermediate connecting layer (or composite contact layer) located between the crystalline silicon bottom cell and the perovskite top cell plays a crucial role. It needs to simultaneously possess excellent lateral conductivity, high light transmittance, and the ability to achieve efficient and low-loss charge (usually hole) transport and collection between the two cells.

[0006] The intermediate connecting layer of existing perovskite / crystalline silicon tandem solar cells is usually made of transparent conductive oxide (TCO) material. However, the valence band top of the perovskite top cell and the conduction band bottom of the crystalline silicon bottom cell each have specific energy positions, which can fluctuate due to factors such as material batch, process, and thickness. The work function of the intermediate connecting layer of a single TCO material is fixed, making it difficult to achieve precise energy level matching with the crystalline silicon bottom cell and the perovskite top cell. This easily forms an interface barrier, which reduces the efficiency of carrier extraction and transport, increases interface recombination loss, and leads to a decrease in the open circuit voltage and fill factor of the perovskite / crystalline silicon tandem solar cell. Summary of the Invention

[0007] This application provides a solar tandem cell and its preparation method, as well as a photovoltaic module, to solve or alleviate one or more of the technical problems mentioned above.

[0008] The first aspect of this application provides a solar tandem battery, which includes a bottom cell, a composite layer, and a top cell stacked together. The composite layer comprises multiple functional layers stacked together, wherein the work function of the multiple functional layers increases in the direction from the bottom cell to the top cell.

[0009] The second aspect of this application provides a method for preparing a solar tandem cell, the method comprising: A multi-layered functional layer is formed on the surface of the bottom cell by using a multi-pass magnetron sputtering process to obtain a composite layer; A top cell is formed on the surface of the composite layer away from the bottom cell, resulting in a solar tandem cell. In this process, by controlling the volume fraction of the reactive gas in the sputtering gas to change successively, the work function of the multilayer functional layers increases in the direction from the bottom cell to the top cell.

[0010] A third aspect of this application provides a photovoltaic module, which includes the solar tandem cells as described above.

[0011] The advantages of using the above-described technical solution in this application include the following: This application sets up a composite layer composed of multiple functional layers between the bottom cell and the top cell of a solar tandem cell. The work function of the multi-layer functional layer increases in the direction from the bottom cell to the top cell, so that the band structure of the multi-layer functional layer achieves a continuous transition. This design optimizes the energy level matching between the top cell and the bottom cell, effectively reduces the interface barrier, promotes the extraction and transport of charge carriers, and suppresses interface recombination loss. This helps to improve the open circuit voltage and fill factor of the solar tandem cell, and ultimately improves its photoelectric conversion efficiency. Attached Figure Description

[0012] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0013] Figure 1 This is a schematic diagram of the structure of the solar tandem cell in Embodiment 1 of this application; Figure 2 This is a schematic diagram of the composite layer structure in Embodiment 1 of this application; Figure 3 This is a schematic diagram of the mechanism by which the functional layer improves charge transport in a specific embodiment of this application; Explanation of reference numerals in the attached figures: 1. Crystalline silicon bottom cell; 2. Composite layer; 3. Hole transport layer; 4. Perovskite absorber layer; 5. Electron transport layer; 6. Electrode layer.

[0014] 21. First functional layer; 22. Second functional layer. Detailed Implementation

[0015] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, and elements, as well as their relative dimensions, may be exaggerated. Throughout, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0016] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0017] In this application, when numerical intervals (i.e., numerical ranges) are involved, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0018] This application provides a technical solution for a solar tandem cell, its fabrication method, and a photovoltaic module. Details are provided below.

[0019] The fill factor (FF) used in this article refers to the actual maximum available power (P).m or V mp J mp ) and theoretical (not practically obtainable) power (Jsc The ratio of Voc. Therefore, FF can be determined by the following formula: FF = (Voc) / (Voc) mp J mp ) / (J sc V oc ), where Jmp and Vmp represent the current density and voltage at the maximum power point (Pm), respectively, which is determined by changing the resistance in the circuit until Jmp is reached. V is obtained at its maximum value; Jsc and Voc represent the short-circuit current and open-circuit voltage, respectively. The fill factor is a key parameter for evaluating solar tandem cells. Commercial solar tandem cells typically have a fill factor of approximately 60% or higher.

[0020] The open-circuit voltage (Voc) used in this paper is the potential difference between the anode and cathode of the device under conditions of no external load connection.

[0021] The short-circuit current (Isc) used in this article is the maximum current flowing through the output terminal of a photovoltaic cell or module when it is short-circuited (voltage V=0) under STC conditions.

[0022] The power conversion efficiency (PCE) of the solar tandem cells used in this article refers to the percentage of power converted from absorbed light into electrical energy. The PCE of a solar tandem cell can be measured under standard test conditions (STC) with incident light irradiance (E: W / m²). 2 ) and the surface area of ​​solar tandem cells (Ac:m 2 The STC is calculated by dividing by the point of maximum power (Pm). STC typically refers to the value at a temperature of 25°C and an irradiance of 1000 W / m². 2 The spectrum of air quality 1.5 (AM1.5).

[0023] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. It should be understood that these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0024] This application provides a solar tandem battery, which includes a bottom cell, a composite layer, and a top cell stacked together; the composite layer includes multiple functional layers stacked together; the work function of the multiple functional layers increases in the direction from the bottom cell to the top cell.

[0025] In some embodiments, the number of functional layers is 2-5 (exemplary, 2, 3, 4, or 5 layers). Within this range, the gradient continuity of the band structure can be maintained while avoiding a significant increase in series resistance. Too few layers make it difficult to form an effective gradient; too many layers introduce too many interfaces, impairing device reliability.

[0026] In some embodiments, the thickness of each functional layer is 3-15 nm (exemplary thicknesses include 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, etc.). This thickness range allows for the formation of continuous conductive pathways while maintaining good light transmittance. Too thin a layer makes it difficult to form an effective conductive network; too thick a layer significantly reduces light transmittance, making it difficult to achieve both conductivity and light transmittance simultaneously. It is understood that the thicknesses of multiple functional layers can be the same or different.

[0027] In some embodiments, the material of the functional layer includes a transparent conductive oxide material, which includes any one or a combination of at least two of indium tin oxide, indium zinc oxide, tungsten-doped indium oxide, zirconium-doped indium oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, or gallium-doped zinc oxide.

[0028] In some embodiments, the oxygen vacancy concentration of the multilayer functional layers decreases along the direction from the bottom cell to the top cell.

[0029] In this application, an oxygen vacancy refers to a defect formed when an oxygen atom in a metal oxide crystal lattice gains sufficient energy to detach from its original position under specific external conditions. In this application, oxygen vacancies are characterized using XPS.

[0030] It is understandable that by controlling the number of functional layers, thickness, material, and oxygen vacancy concentration, a continuous transition of the energy level structure of multi-layer functional layers can be achieved, thereby optimizing the energy level matching between the top and bottom cells and reducing light loss while ensuring conductivity.

[0031] In some embodiments, the bottom cell is selected from crystalline silicon bottom cells, CIGS thin-film bottom cells, cadmium telluride thin-film bottom cells, III V thin-film bottom cells, or perovskite bottom cells.

[0032] In some embodiments, the bottom cell is a crystalline silicon bottom cell, and the top cell is a perovskite top cell, thus forming a perovskite / crystalline silicon tandem solar cell. The crystalline silicon bottom cell includes an N-type monocrystalline silicon substrate, a P-type amorphous silicon thin film (P-side) deposited on one side of the N-type monocrystalline silicon substrate, a transparent conductive layer, and a back electrode, and an N-type amorphous silicon thin film (N-side) deposited on the other side of the N-type monocrystalline silicon substrate. The N-type monocrystalline silicon substrate has a thickness of 80 μm to 220 μm and is mainly used to absorb light and generate charge carriers (holes and electrons). The P-type amorphous silicon thin film has a thickness of 5 to 30 nm, and the N-type amorphous silicon thin film has a thickness of 5 nm to 30 nm. The P-type and N-type amorphous silicon films form a PN junction, generating a built-in electric field to separate electrons and holes. The transparent conductive layer has a thickness of 15 nm to 60 nm, and the back electrode has a thickness of 2 μm to 30 μm. The transparent conductive layer and the back electrode are mainly used to collect and conduct current.

[0033] In some embodiments, the materials of the transparent conductive layer include, but are not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO), indium zirconium oxide (IZrO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), and gallium-doped zinc oxide (GZO), and the preparation methods include, but are not limited to, magnetron sputtering (PVD) and reactive plasma deposition (RPD).

[0034] In some embodiments, the material of the back electrode includes a metal, specifically at least one of the following metals: copper (Cu), aluminum (Al), silver (Ag), nickel (Ni), cobalt (Co), gold (Au), molybdenum (Mo), or chromium (Cr). Examples include combinations of Ag, copper, Cu, and Al; combinations of Ag and Ni; combinations of Co and Au; combinations of Mo and Cr; or combinations of Cu, Al, Ag, Ni, Co, Au, Mo, and Cr. In some embodiments, the back electrode is prepared by methods including, but not limited to, vapor deposition, screen printing, electroplating, laser technology, PVD (Physical Vapor Deposition), and inkjet printing.

[0035] In some embodiments, the perovskite top solar cell includes a hole transport layer, a perovskite absorber layer, and an electron transport layer prepared sequentially, wherein the hole transport layer is connected to the composite layer.

[0036] In some embodiments, the material of the hole transport layer includes at least one of organic small molecule materials, polymer materials, and transition metal oxide materials.

[0037] Organic small molecule materials include self-assembled monolayer (SAM) materials. SAMs can form monolayers on the surface of composite layers through self-assembly, thereby regulating interfacial properties, promoting charge transport, and reducing non-radiative recombination. SAM materials generally consist of anchoring groups, alkyl bridges, and terminal groups.

[0038] Anchoring groups typically contain polar atoms (such as oxygen, nitrogen, and sulfur) or active functional groups, which can form chemical bonds (such as covalent bonds and coordinate bonds) or strong hydrogen bonds with hydroxyl groups (-OH) or metal atoms on the surface of the composite layer, thus tightly anchoring it to the surface of the transparent conductive oxide. Common types of anchoring groups include phosphonic acid groups (-PO(OH)2), carboxyl groups (-COOH), hydroxyl groups (-OH), and thiol groups (-SH), with phosphonic acid groups (-PO(OH)2) being preferred. The bonding strength of the anchoring groups directly determines the stability of the self-assembled monomolecule material (such as water resistance and heat resistance); if the bonding is too weak, the self-assembled monomolecule material is prone to detachment, leading to the degradation of solar cell performance. Terminal groups include carbazole groups, dibenzocarbazole groups, acridine groups, phenothiazine groups, or phenyl groups. Terminal groups have a conjugated structure, and the π-electron cloud of the conjugated structure can be used to compensate for the charge of halogen vacancies in perovskite, filling the shallow energy level defects caused by halogen vacancies. The nitrogen atoms of terminal groups such as carbazole, dibenzocarbazole, acridine, and phenothiazine contain lone pairs of electrons, which can form coordination bonds with uncoordinated lead ions on the perovskite surface, thereby precisely passivating deep-level defects caused by uncoordinated lead ions. This allows the work function of the hole transport layer to match the energy levels of the perovskite layer, facilitating hole transport. The terminal groups may further contain substituents, which can be used to regulate the electron cloud density of the terminal groups, enhance their coordination with uncoordinated lead ions, improve passivation efficiency, and coordinate with uncoordinated lead ions or halogen vacancies in the perovskite layer, suppressing grain boundary defects. Substituents include at least one of halogen substituents, alkyl, alkoxy, benzene substituents, and bis(4-methoxyphenyl)amino. The alkyl chain bridge is the "skeleton" connecting the anchoring group and the terminal group, usually composed of carbon chains, commonly C6-C. 18 The alkyl chain. The length of the alkyl chain bridge determines the spatial distance between the anchoring group (TCO side) and the terminal group (perovskite side). The length and chemical properties of the alkyl chain bridge also affect the orderliness, conductivity, and steric hindrance of self-assembled monomolecules.

[0039] In some embodiments, the self-assembled monomolecular materials include [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz, CAS No. 20999-38-6), [2-(3,6-dimethyl-9H-carbazole-9-yl)ethyl]phosphonic acid (Me-2PACz, CAS No. 2996161-30-7), (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid (MeO-2PACz, CAS No. 2377770-18-6), and [2-(3,6-diphenyl-9H-carbazole-9-yl)ethyl]phosphonic acid (Ph-2PACz, CAS No. 3085827-62-6). [2-(3,6-Diiodo-9H-carbazole-9-yl)ethyl]phosphonic acid (I-2PACz, CAS No. 3026275-69-1), 2-(3,6-dibromo-9H-carbazole-9-yl)ethyl]phosphonic acid (Br-2PACz, CAS No. 2762888-11-7), 2-(3,6-dichloro-9H-carbazole-9-yl)ethyl]phosphonic acid (Cl-2PACz, CAS No. 3036926-72-1), 2-(3,6-difluoro-9H-carbazole-9-yl)ethyl]phosphonic acid (F-2PACz, CAS No. 3036926-69-6), [ 2-(7H-dibenzocarbazole-7-yl)ethyl]phosphoric acid (2PADCB, CAS No. 2882156-61-6), [4-(9H-carbazole-9-yl)ethyl]phosphoric acid (4PACz, CAS No. 20999-36-4), [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz, CAS No. 2747959-96-0), [4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz, CAS No. 2377770-18-6), [4-(3,6-diphenyl- [4-(3,6-diiodo-9H-carbazole-9-yl)butyl]phosphonic acid (Ph-4PACz, CAS No. 2814500-04-2), [4-(3,6-diiodo-9H-carbazole-9-yl)butyl]phosphonic acid (Br-4PACz, CAS No. 3026275-67-9), [4-(3,6-dibromo-9H-carbazole-9-yl)butyl]phosphonic acid (Br-4PACz, CAS No. 2996161-28-3), (4-(3,6-dichloro-9H-carbazole-9-yl)butyl)phosphonic acid (Cl-4PACz, CAS No. 3026275-66-8) (4-(3,6-difluoro-9H-carbazole-9-yl)butyl)phosphonic acid (F-4PACz, CAS No. 3026275-65-7), [4-[3-bromo-6-(4-methoxyphenyl)-9H-carbazole-9-yl]butyl]phosphonic acid (BrMeOPh-4PACz, CAS No. 3053380-37-0), (4-(3,6-Di-tert-butyl-9H-carbazole-9-yl)butyl)phosphonic acid (tBu-4PACz) The following are listed as at least one of the following: [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid (4PADCB, CAS No. 2882156-63-8), [4-(2,7-dibromo-9,9-dimethylacridin-10(9-hydro)-yl)butyl]phosphonic acid (2Br-4DMAcPA / DMAcPA, CAS No. 2971088-37-4), 2-(3,7-dibromo-10H-phenthiazin-10-yl)ethyl]phosphonic acid (Br-2EPT, CAS No. 2826271-17-2), and (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl)phosphonic acid (MPA-CPA, CAS No. 2212003-31-9).

[0040] In some embodiments, the organic small molecule material further includes 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline] (TAPC), etc. When 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD) is used as the hole transport layer material, additives are typically added to improve the conductivity and hole mobility of the hole transport layer. Exemplarily, additives include lithium bis(trifluoromethanesulfonylimide) (Li-TFSI) and 4-tert-butylpyridine (tBP). Li-TFSI acts as a p-type dopant, providing mobile lithium ions (Li... + ) and free holes, significantly improving the conductivity and hole mobility of the hole transport layer, tBP) suppresses Li + Diffusion into the perovskite layer to avoid Li + Inducing perovskite decomposition, thereby ensuring the efficiency and stability of solar cells.

[0041] In some embodiments, the transition metal oxide material includes at least one selected from nickel oxide, copper oxide, cobalt tetroxide, and ferric oxide. The preparation processes for transition metal oxide materials include solution methods, physical vapor deposition (PVD), atomic layer deposition (ALD), and inkjet printing.

[0042] In some embodiments, the polymer material includes at least one of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and poly(3-hexylthiophene) (P3HT).

[0043] In some embodiments, the method for preparing a hole transport layer includes: A1. Mix the self-assembled monomolecule material with a solvent and stir at room temperature in a glove box under a nitrogen atmosphere until completely dissolved to obtain a self-assembled monomolecule solution. The concentration of the self-assembled monomolecule material in the self-assembled monomolecule solution is 0.1-3 mg / mL (exemplary concentrations are 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL, 2 mg / mL, 2.5 mg / mL, 3 mg / mL, etc.). A2. In a glove box under a nitrogen atmosphere, the self-assembled monomolecular solution is coated to obtain a wet film; then it is placed on a hot plate at 80-120℃ (exemplary temperatures are 80℃, 90℃, 100℃, 110℃, 120℃, etc.) and heated and annealed for 5-20 min (exemplary times are 5 min, 10 min, 15 min, 20 min, etc.) to form a self-assembled monomolecular layer as a hole transport layer.

[0044] In some embodiments, a seed layer is provided between the top battery and the composite layer.

[0045] In some embodiments, the thickness of the seed layer is 1-3 nm (exemplary thicknesses are 1 nm, 2 nm, 3 nm, etc.).

[0046] In some embodiments, the oxygen vacancy concentration of the seed layer is higher than that of the functional layer connected to the seed layer.

[0047] In some embodiments, the seed layer is made of a transparent conductive oxide material, which includes any one or a combination of at least two of indium tin oxide, indium zinc oxide, tungsten-doped indium oxide, zirconium-doped indium oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, or gallium-doped zinc oxide.

[0048] In this application, in the tandem battery, the hole transport layer of the top cell is connected to the composite layer. When the hole transport layer is made of a self-assembled monomolecule material, the introduction of the seed layer is beneficial to the orderly self-assembly of the self-assembled monomolecule material. In particular, the seed layer prepared in an oxygen-free environment has more oxygen vacancies and uncoordinated metal ions on its surface, which can form stronger chemical bonds with the anchoring groups of the self-assembled monomolecule material.

[0049] In this application, an extremely thin seed layer is provided, which not only enables the anchoring groups in the self-assembled monomolecule material to anchor to the surface of the seed layer through hydrogen bonds, but also allows the anchoring groups in the self-assembled monomolecule material to fully occupy the oxygen vacancies on the surface of the seed layer and form chemical bonds with free metal ions, thereby further enhancing the anchoring effect of the self-assembled monomolecule material of the hole transport layer on the surface of the functional layer and making the hole transport layer uniformly laid.

[0050] In some embodiments, the electron transport layer material includes inorganic metal oxide materials such as SnO2, TiO2, ZnO, ZrO2, ZnO, MgO, zinc gallium oxide, zinc indium oxide, fluorine-doped tin oxide, and indium tin oxide. Its preparation processes include sol-gel method, atomic layer deposition (ALD), chemical vapor deposition (CVD, including plasma-enhanced chemical vapor deposition (PECVD), metal-organic chemical vapor deposition (MOCVD), physical vapor deposition (PVD, including magnetron sputtering, thermal evaporation, pulsed laser deposition (PLD), spray pyrolysis, solution spin coating, electrochemical deposition, and chemical bath deposition). Atomic layer deposition (ALD) is preferred.

[0051] In some embodiments, the specific process for preparing the electron transport layer of an inorganic metal oxide material by atomic layer deposition (ALD) includes: alternately introducing a metal precursor and an oxygen source under a gas pressure of 0.05 Torr to 1.5 Torr. The flow rate of the metal precursor introduced in each cycle is 10 sccm to 100 sccm, and the pulse duration of the metal precursor introduction in each cycle is 100 ms to 300 ms. The flow rate of the oxygen source introduced in each cycle is 10 sccm to 100 sccm, and the pulse duration of the oxygen source introduction in each cycle is 100 ms to 300 ms. The thickness of the electron transport layer of the inorganic metal oxide material prepared by atomic layer deposition (ALD) is 20 nm to 200 nm, and the growth rate of the inorganic metal oxide is typically between 0.03 and 0.2 nm / cycle. The required number of cycles depends on the type of metal precursor, the type of oxygen source, and the process temperature. It should be noted that in the process of alternately introducing the metal precursor and oxygen source, the metal precursor is introduced first.

[0052] In some embodiments, the material of the electron transport layer also includes C 60 Fullerene C 70 Organic materials such as (6,6)-phenyl-C61-butyrate methyl ester (PCBM) and 4-(1',5'-dihydro-1'-methyl-2'H-(5,6)fullerene-C60-In-(1,9-c)pyrrole-2'-yl)benzamine chloride (CPMAC) are prepared. Their preparation processes include vacuum evaporation, spin coating, inkjet printing, doctor blade coating, slot coating, dip coating, spray coating, drop coating, and roll-to-roll printing. Vacuum evaporation is preferred, with a evaporation rate of 0.05 nm / s to 0.1 nm / s.

[0053] In some embodiments, the electron transport layer material also includes one or more inorganic silicon materials such as n-type monocrystalline silicon, n-type polycrystalline silicon, and n-type amorphous silicon. Its fabrication processes mainly include low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), magnetron sputtering, thermal diffusion (such as phosphorus diffusion), ion implantation, sol-gel methods, and electron beam evaporation.

[0054] In some embodiments, the material of the electron transport layer may be a single material selected from the above-mentioned materials, or a combination of multiple materials, for example, it may be C. 60 , fullerene derivatives (6,6)-phenyl-C61-butyrate methyl ester (PCBM), combinations of C60 and PCBM, combinations of PCBM and ZnO, combinations of ZnO and MgO, combinations of C60, PCBM and ZnO, combinations of PCBM, ZnO and MgO, or combinations of C60, PCBM, ZnO and MgO.

[0055] In some embodiments, the thickness of the electron transport layer is 3–50 nm. This application does not limit the material, fabrication process, or thickness of the electron transport layer.

[0056] In some embodiments, the thickness of the perovskite layer is 100~1000 nm.

[0057] In some embodiments, the perovskite layer material comprises a perovskite structural material with the general structural formula ABX3; wherein the A-site cation is typically a monovalent cation, including at least one of a monovalent metal cation and a monovalent organic cation, wherein the monovalent metal cation is selected from cesium ions (Cs). + ), rubidium ions (Rb + Lithium ion (Li) + Sodium ions (Na) + Potassium ions (K+), thallium ions (Tl) + One or more of the following, wherein the monovalent organic cation is selected from ammonium ions (NH4+). + ), Methylamine ion (MA) (CH3NH3) + ), ethylammonium ion (CH3CH2NH3) + ), dimethylamine ion ((CH3)2NH2) + ), trimethylammonium ion ((CH3)3NH + ), tetramethylammonium ion ((CH3)4N + ), formamidinium ion (FA) (HC(NH2)2) + ), Methylformamidinium ion (CH3C(NH2)2 + Acetamidinium ion (H3C2(NH2)2)+ ), guanidinium ion (C(NH2)3 + ), or one or more of the following. The B-site cation is usually a divalent metal cation, selected from lead ion (Pb 2+ ), tin ion (Sn 2+ ), or germanium ion (Ge 2+ ). The X-site anion includes halogen anions, thiocyanate ion (SCN - ), tetrafluoroborate ion (BF4 - ), and hexafluoroborate ion (BF6 - ), or one or more of the following. The halogen anions include bromide ion (Br - ), iodide ion (I - ), chloride ion (Cl - ), at least one of which.

[0058] Exemplarily, the perovskite-structured material is selected from FAPbI3, MAPbI3, CsPbI3, and Cs x FA 1-x Pb(Br y I 1-y ), where 0.1 < x < 0.3, 0.1 < y < 0.4, and the specific composition of the perovskite-structured material is not limited in this application.

[0059] In some embodiments, the preparation process of the perovskite layer includes: forming a perovskite precursor layer, forming a perovskite precursor layer, annealing the perovskite precursor layer, and obtaining the perovskite layer.

[0060] In some embodiments, the process of forming the perovskite precursor layer includes coating and evaporation. Coating can be carried out by slit coating, blade coating, spin coating, etc., which is not limited in this application. It should be noted that during the coating process, especially in small-area coating processes such as spin coating, an anti-solvent can be added dropwise to precisely control the crystallization process of the perovskite, and finally obtain a high-density, low-defect, and high-phase purity perovskite active layer film. The anti-solvent includes at least one of chlorobenzene, dichloromethane, dichlorobenzene, toluene, ethyl acetate, chloroform, and ether. When preparing the perovskite precursor layer by coating process, the perovskite precursor material needs to be mixed with a solvent to prepare a perovskite precursor solution, and then the perovskite precursor solution is coated to obtain the perovskite precursor layer.

[0061] In some embodiments, in the perovskite precursor solution, the molar concentration of the perovskite precursor material is 1 - 2 mol / L (exemplarily, the molar concentration is 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, etc.).

[0062] In some embodiments, the solvent in the perovskite precursor solution includes at least one selected from N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), 2-methoxyethanol (2-Me), N,N'-dimethylacrylurea (DMPU), 1,3-dimethyl-2-imidazolinone (DMI), N,N-diethylformamide (DEF), and sulfolane. Preferably, the solvent is a combination of DMF and NMP, a combination of DMF and DMI, or a combination of DMF and DMSO.

[0063] When the solvent is a combination of DMF and NMP, the volume ratio of DMF to NMP is 4:1; when the solvent is a combination of DMF and DMI, the volume ratio of DMF to DMI is 9:1; when the solvent is a combination of DMF and DMSO, the volume ratio of DMF to DMSO is 4:1.

[0064] In some embodiments, the perovskite precursor material includes a first precursor compound and a second precursor compound. The first precursor compound has the chemical formula AX, and may be, for example, one or a combination of several of the following: FAI (formamidine iodide), FABr (formamidine bromide), MAI (methylammonium iodide), MABr (methylammonium bromide), CsI (cesium iodide), and CsBr (cesium bromide). The second precursor compound has the chemical formula BX2, and may be, for example, one or a combination of several of the following: PbI2 (lead iodide), PbBr2 (lead bromide), SnI2 (stannous iodide), and SnBr2 (stannous bromide).

[0065] Perovskite precursor materials can also be classified into organic precursor compounds and inorganic precursor compounds. Organic precursor compounds include at least one of FAI (formamidine iodide), FABr (formamidine bromide), MAI (methylammonium iodide), and MABr (methylammonium bromide), while inorganic precursor compounds include at least one of CsI (cesium iodide), CsBr (cesium bromide), PbI2 (lead iodide), PbBr2 (lead bromide), SnI2 (stannous iodide), and SnBr2 (stannous bromide).

[0066] In preparing the perovskite precursor layer, a combined vapor deposition and coating process can also be used. For example, an inorganic precursor compound can be vapor deposited to obtain a framework layer, and then an organic precursor compound solution can be coated on the framework layer to obtain a wet film. The wet film and the framework layer constitute the perovskite precursor layer. The solvent of the organic precursor compound solution includes at least one of ethanol, isopropanol (IPA), and γ-butyrolactone (GBL).

[0067] In some embodiments, the annealing crystallization temperature is 90-150°C (exemplary temperatures include 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.), and the time is 5-30 min (exemplary times include 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, etc.). The purpose of annealing is to drive the perovskite precursor material to undergo a chemical reaction and crystallize to form a perovskite layer, while removing residual solvent.

[0068] In some embodiments, the top cell further includes a transparent conductive functional layer and a top electrode layer, wherein the transparent conductive functional layer is disposed between the electron transport layer and the top electrode layer. The transparent conductive functional layer, deposited on the electron transport layer, is a thin film that is both conductive and transparent to light. It is used for lateral charge collection of carriers and their transport to the top electrode layer, and also reduces the reflection of incident light on the surface of the perovskite top cell, increasing the absorption of light by the solar tandem cell. The top electrode layer is used for the efficient collection and extraction of carriers transported by the transparent conductive functional layer. The transparent conductive functional layer and the top electrode layer together constitute the efficient current collection and extraction system of the solar tandem cell.

[0069] In some embodiments, the transparent conductive functional layer is prepared using a transparent conductive oxide material, and the preparation method includes, but is not limited to, magnetron sputtering (PVD) and reactive plasma deposition (RPD), with a thickness of 10 nm to 100 nm.

[0070] In some embodiments, the material of the top electrode layer includes any one or a combination of at least two of copper (Cu), aluminum (Al), silver (Ag), nickel (Ni), cobalt (Co), gold (Au), molybdenum (Mo), or chromium (Cr), preferably a combination of Ag, copper, Cu, and Al; a combination of Ag and Ni; a combination of Co and Au; a combination of Mo and Cr; or a combination of Cu, Al, Ag, Ni, Co, Au, Mo, and Cr. The top electrode layer is prepared by methods including vapor deposition, screen printing, electroplating, laser technology, physical vapor deposition (PVD), or inkjet printing. The thickness of the top electrode layer is 10–120 μm.

[0071] This application provides a method for preparing a solar tandem cell in its embodiments. The preparation method includes: A multi-layered functional layer is formed on the surface of the bottom cell by using a multi-pass magnetron sputtering process to obtain a composite layer; A top cell is formed on the surface of the composite layer away from the bottom cell, resulting in a solar tandem cell. In this process, by controlling the volume fraction of the reactive gas in the sputtering gas to change successively, the work function of the multilayer functional layers increases along the direction from the bottom cell to the top cell.

[0072] Figure 3 A mechanism diagram for improving charge transport in functional layers, through Figure 3 It is known that after the perovskite absorber layer absorbs photons and generates electron-hole pairs, the holes are first transported along the valence band bottom to the hole transport layer. If there is only one functional layer, the hole transport efficiency is relatively low. When there are two or more functional layers, the holes require less energy to transport to the second functional layer more quickly, where they recombine rapidly with the electrons transported from the crystalline silicon bottom cell, thereby improving the overall carrier transport capability of the device.

[0073] This application provides a method for preparing a solar tandem cell. While being compatible with existing battery production lines, the method achieves a gradient change in the work function of the functional layers by adjusting the concentration of the reactant gas.

[0074] It should be noted that conventional methods for fabricating multilayer functional layers require interrupting deposition between each layer to adjust the target material or process parameters, which can lead to significant interface defects. This application achieves a gradient transition by controlling the content of reactive gases, eliminating clear physical interfaces between layers and thus greatly reducing the occurrence of interface defects.

[0075] In some embodiments, the sputtering power of the magnetron sputtering method is 100-800 W (exemplary sputtering powers are 100W, 300W, 500W, 800W, etc.), the sputtering time is 5-60 s (exemplary sputtering times are 5 s, 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, etc.), and the sputtering gas flow rate is 30-500 sccm (exemplary sputtering gas flow rates are 30 sccm, 50 sccm, 80 sccm, 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, etc.).

[0076] In this application, the functional layer is prepared by magnetron sputtering, which results in a functional layer with good density. When the sputtering power is 100-800 W, the sputtering time is 5-60 s, and the sputtering gas flow rate is 30-500 sccm, both production efficiency and film quality can be achieved simultaneously.

[0077] The functional layer is made of transparent conductive oxide material. In the magnetron sputtering process, the bottom cell is used as the substrate and a transparent conductive oxide target is used. The target is bombarded by sputtering gas, causing transparent conductive oxide particles to escape and reach the substrate. Through the process of adsorption, diffusion, nucleation and growth, a continuous and dense functional layer is gradually formed.

[0078] Sputtering gases include inert gases, which are selected from argon, krypton or xenon, etc. Argon is preferred because its atomic weight (39.9) is moderate and the ion bombardment intensity is balanced. This ensures a sufficient sputtering rate while avoiding excessive bombardment that could lead to target ablation and substrate overheating. At the same time, argon has extremely strong chemical inertness and will not react with the target or substrate, thus ensuring the purity of the functional layer.

[0079] The sputtering gas also includes a reactive gas, which includes at least one of oxygen, nitrogen, methane, acetylene, and hydrogen, preferably oxygen and / or hydrogen. Oxygen primarily regulates the proportion of oxygen atoms in the escaping particles during sputtering, thereby adjusting the oxygen vacancy content of the functional layer and consequently, the work function of the functional layer. Hydrogen primarily induces chemical reduction in the functional layer, increasing oxygen vacancies, and simultaneously hydroxylates the surface of the functional layer to form a dipole layer. These two processes regulate the Fermi level, thus contributing to the adjustment of the work function of the functional layer.

[0080] In some embodiments, the reaction gas includes oxygen and / or hydrogen. Along the direction from the bottom cell to the top cell, during the fabrication of the multilayer functional layers, the volume fraction of oxygen in the sputtering gas increases sequentially, and / or the volume fraction of hydrogen in the sputtering gas decreases sequentially.

[0081] In some embodiments, when the functional layer adjacent to the bottom battery is prepared, the volume fraction of oxygen in the sputtering gas is 0.1-10% (exemplary examples include 0.1%, 0.5%, 1%, 3%, 5%, 7%, 10%, etc.); when the functional layer adjacent to the top battery is prepared, the volume fraction of oxygen in the sputtering gas is 1-20% (exemplary examples include 1%, 3%, 5%, 7%, 10%, 13%, 15%, 17%, 20%, etc.). It should be noted that when the functional layer adjacent to the top battery is prepared, the volume fraction of oxygen in the sputtering gas needs to be higher than that when the functional layer adjacent to the bottom battery is prepared.

[0082] The work function of the functional layer is modulated by controlling the oxygen content in the sputtering gas. Essentially, the higher the volume fraction of oxygen in the sputtering gas, the lower the oxygen vacancy concentration in the functional layer. As a donor defect, the decrease in oxygen vacancy concentration directly leads to a decrease in the free carrier concentration, causing the Fermi level position to shift towards the valence band, which ultimately manifests as an increase in the work function of the functional layer.

[0083] In some embodiments, when the functional layer adjacent to the bottom cell is prepared, the volume fraction of hydrogen in the sputtering gas is 0.1-1% (exemplary, the volume fraction of hydrogen in the sputtering gas is 0.1%, 0.3%, 0.5%, 0.8%, 1%, etc.); when the functional layer adjacent to the top cell is prepared, the volume fraction of hydrogen in the sputtering gas is 0-0.6% (exemplary, the volume fraction of hydrogen in the sputtering gas is 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, etc.).

[0084] The work function of the functional layer is modulated by controlling the hydrogen content in the sputtering gas. Essentially, during magnetron sputtering, hydrogen is ionized, and the more active hydrogen atoms enter the functional layer lattice, the higher the Fermi level of the functional layer shifts, and the lower the work function becomes.

[0085] Thus, incorporating an appropriate amount of hydrogen into the sputtering gas, especially in the range of 0-1%, has a dual optimizing effect on the functional layer: firstly, hydrogen can act as a donor dopant, effectively modulating the Fermi level and work function; secondly, hydrogen can passivate deep-level defect states within the functional layer, improving the electrical quality of the material. This synergizes with oxygen gradient modulation. Particularly in the IZO functional layer, hydrogen can specifically passivate deep-level defects such as indium vacancies, significantly improving carrier lifetime, thereby ensuring excellent bulk transport characteristics while achieving continuous band transition.

[0086] In some embodiments, when oxygen and hydrogen are used as reactants, the oxygen content increases and the hydrogen content decreases gradually during the fabrication of the multilayer functional layers along the direction from the bottom cell to the top cell.

[0087] In some embodiments, when oxygen and hydrogen are used as reactants simultaneously, the functional layer adjacent to the bottom cell has an oxygen volume fraction of 0.1-10% in the sputtering gas (exemplary, the oxygen volume fraction in the sputtering gas is 0.1%, 0.5%, 1%, 3%, 5%, 7%, 10%, etc.) and a hydrogen volume fraction of 0.1-1% in the sputtering gas (exemplary, the hydrogen volume fraction in the sputtering gas is 0.1%, 0.3%, 0.5%, 0.8%, 1%, etc.); the functional layer adjacent to the top cell has an oxygen volume fraction of 1-20% in the sputtering gas (exemplary, the oxygen volume fraction in the sputtering gas is 1%, 3%, 5%, 7%, 10%, 13%, 15%, 17%, 20%, etc.) and a hydrogen volume fraction of 0-0.6% in the sputtering gas (exemplary, the hydrogen volume fraction in the sputtering gas is 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, etc.).

[0088] In some embodiments, prior to forming the top cell, a seed layer is first formed on the surface of the composite layer away from the bottom cell using a magnetron sputtering process.

[0089] In some embodiments, the sputtering power of the magnetron sputtering method is 100-800 W (exemplary sputtering powers are 100W, 300W, 500W, 800W, etc.), the sputtering time is 5-60 s (exemplary sputtering times are 5 s, 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, etc.), and the sputtering gas flow rate is 30-500 sccm (exemplary sputtering gas flow rates are 30 sccm, 50 sccm, 80 sccm, 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, etc.).

[0090] In some embodiments, when a seed layer is formed using magnetron sputtering, the volume fraction of oxygen in the sputtering gas is lower than the volume fraction of oxygen in the sputtering gas when a functional layer connected to the seed layer is formed, such that the oxygen vacancy concentration of the seed layer is higher than the oxygen vacancy concentration of the functional layer connected to the seed layer.

[0091] In some embodiments, during the magnetron sputtering process for preparing the seed layer, the volume fraction of oxygen in the sputtering gas is lower than the volume fraction of oxygen in the sputtering gas when forming any layer of the multilayer functional layers, so that the oxygen vacancy concentration of the seed layer is higher than the oxygen vacancy concentration of any layer of the multilayer functional layers.

[0092] In some embodiments, when the seed layer is formed using the magnetron sputtering process, the volume fraction of oxygen in the sputtering gas is 0-3% (exemplary volume fractions are 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.), preferably 0-1%, and more preferably 0%.

[0093] In this application, when the top cell is a perovskite top cell and the hole transport layer of the perovskite top cell is made of a self-assembled monomolecule material, by setting a seed layer with a higher oxygen vacancy concentration on the functional layer, on the one hand, the chemical interaction between the functional layer and the self-assembled monomolecule material can be enhanced, which is conducive to the large-area uniform spread of the self-assembled monomolecule material to form a dense hole transport layer. On the other hand, it can also protect the functional layer from damage by subsequent processes.

[0094] In this application, the seed layer is prepared in an oxygen-free environment, which exposes more uncoordinated metal ion sites on the surface of the seed layer, enabling it to form strong coordination bonds with the anchoring groups in the self-assembled monomolecule material.

[0095] The following section will conduct performance tests on the structure or manufacturing method of the solar tandem cell provided in the embodiments of this application, as well as related comparative examples.

[0096]

Example 1

[0097] Among them, composite layers such as Figure 2 As shown, it includes a first functional layer 21 and a second functional layer 22 stacked from bottom to top; the thickness of the first functional layer and the second functional layer is 15 nm, the material is IZO, the work function of the first functional layer is lower than that of the second functional layer, and the oxygen vacancy concentration of the first functional layer is higher than that of the second functional layer.

[0098] This embodiment also provides a method for preparing a solar tandem cell, including the following steps: (1) Pretreatment of crystalline silicon bottom cells: A 10cm × 10cm crystalline silicon solar cell was used as the substrate. This crystalline silicon solar cell comprises an N-type monocrystalline silicon substrate (220 μm thick), a P-type amorphous silicon film (20 nm thick) sequentially deposited on the back side (backlight side) of the N-type monocrystalline silicon substrate, an indium tin oxide (ITO) transparent conductive layer and a silver electrode (500 nm thick), and an N-type amorphous silicon film (20 nm thick) deposited on the front side (light-facing side) of the N-type monocrystalline silicon substrate. Ethanol was spin-coated onto the surface of the N-type amorphous silicon film in a spin coater at 3000 rpm for 60 seconds, followed by heat treatment at 200°C for 10 minutes to complete the cleaning process.

[0099] (2) Preparation of composite layer: A first functional layer with a thickness of 15 nm and a second functional layer with a thickness of 15 nm were sequentially deposited on an N-type amorphous silicon thin film on the back of a crystalline silicon solar cell using magnetron sputtering, resulting in a composite layer with a thickness of 30 nm. The first functional layer was made of IZO, and the magnetron sputtering process used IZO as the target material, with a sputtering power of 300 W, a sputtering time of 40 s, and a sputtering gas flow rate of 50 sccm (where oxygen accounted for 5% and argon for 95% by volume). The second functional layer was also made of IZO, and the magnetron sputtering process used the same method with a power of 300 W, a sputtering time of 40 s, and a gas flow rate of 50 sccm (where oxygen accounted for 10% and argon for 90% by volume). X-ray photoelectron spectroscopy (XPS) analysis of the first and second functional layers showed that the oxygen vacancy concentration in the first functional layer was higher than that in the second functional layer.

[0100] (3) Preparation of hole transport layer: [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid (4PADCB) was dissolved in anhydrous ethanol and stirred to prepare a solution containing 2.5 mM 4PADCB. This solution was then spin-coated onto the surface of the composite layer in a cleanroom at 25°C and 10% humidity at a spin speed of 3000 rpm for 30 seconds, followed by annealing at 100°C for 10 minutes to form a hole transport layer with a thickness of 2 nm.

[0101] (4) Preparation of perovskite absorber layer: Lead iodide and cesium bromide were co-deposited on the surface of the hole transport layer using a thermal evaporation method to form a 550 nm thick framework layer. The deposition rates of lead iodide and cesium bromide were 0.2 nm / s and 0.01 nm / s, respectively, with a volume ratio of 26.5:1. Subsequently, a 0.5 M cationic solution was spin-coated onto the framework layer surface. This solution was prepared by dissolving formamidine iodide (0.5 M), formamidine bromide (0.2 M), methylamine bromide (0.3 M), methylamine iodide (0.1 M), and methylamine chloride (0.2 M) in ethanol. After annealing at 130 °C for 20 minutes, a Cs-based framework layer was formed. 0.05 MA 0.3 FA 0.65 Pb(I, Br)3, a perovskite absorber layer with a thickness of 600 nm; 1,3-Diaminopropane dihydroiodate was thermally deposited on the surface of the perovskite absorber layer at an evaporation temperature of 220 °C and an evaporation rate of 0.02 nm / s to form a perovskite absorber layer with a PDAI passivation layer of 1 nm thickness.

[0102] (5) Fabrication of the electron transport layer: A 20 nm thick C60 layer is deposited on the passivation layer surface using a vacuum deposition instrument, and then a 20 nm thick tin dioxide layer is deposited on its surface using atomic layer deposition, together forming an electron transport layer.

[0103] (6) Preparation of electrode layer: A 50 nm thick indium zinc oxide thin film was deposited on the surface of the electron transport layer at room temperature using a DC magnetron sputtering process to serve as a transparent conductive layer; A silver gate electrode was deposited on the surface of a transparent conductive layer using a vacuum deposition instrument. Subsequently, a lithium fluoride antireflection layer with a thickness of 100 nm was deposited on both the silver gate and the exposed area of ​​the transparent conductive layer to form an electrode layer with an antireflection layer.

[0104]

Example 2

[0105] The first functional layer was prepared using a magnetron sputtering process with a power of 100 W, a sputtering time of 60 s, and a gas flow rate of 30 sccm (where oxygen accounted for 3% of the sputtering gas by volume and argon accounted for 97% of the sputtering gas by volume). The second functional layer was prepared using the same magnetron sputtering process with a power of 100 W, a sputtering time of 60 s, and a gas flow rate of 30 sccm (where oxygen accounted for 5% of the sputtering gas by volume and argon accounted for 95% of the sputtering gas by volume). X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration in the first functional layer was higher than that in the second functional layer.

[0106]

Example 3

[0107] The first functional layer was fabricated using a magnetron sputtering process with a power of 800 W, a sputtering time of 5 s, and a gas flow rate of 500 sccm (where oxygen accounted for 8% of the sputtering gas by volume and argon accounted for 92% of the sputtering gas by volume). The magnetron sputtering process for the second functional layer was 800 W, sputtering time 5 s, and gas flow rate 500 sccm (of which oxygen accounted for 20% by volume and argon accounted for 80% by volume). X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration in the first functional layer was higher than that in the second functional layer.

[0108]

Example 4

[0109] The composite layer includes a first functional layer, a second functional layer, and a third functional layer stacked from bottom to top, each with a thickness of 10 nm and made of IZO. The work function of the first functional layer is less than that of the second functional layer, and the work function of the second functional layer is less than that of the third functional layer.

[0110] Preparation methods include: A first functional layer with a thickness of 10 nm, a second functional layer with a thickness of 10 nm, and a third functional layer with a thickness of 10 nm were sequentially deposited on an N-type amorphous silicon thin film on the back side of the substrate by magnetron sputtering to obtain a composite layer with a thickness of 30 nm.

[0111] The first functional layer is made of IZO, and the magnetron sputtering process is performed at a power of 300 W, a sputtering time of 26 s, and a gas flow rate of 50 sccm (where oxygen accounts for 0.1% by volume and argon accounts for 99.9% by volume). The second functional layer is made of IZO, and the magnetron sputtering process is 300 W, sputtering time 26 s, and gas flow rate 50 sccm (of which oxygen accounts for 8% by volume and argon accounts for 92% by volume). The material of the third functional layer is IZO, and the magnetron sputtering process is 300 W, sputtering time 26 s, and gas flow rate 50 sccm (of which oxygen accounts for 15% by volume and argon accounts for 85% by volume). X-ray photoelectron spectroscopy results show that the oxygen vacancy concentration of the first functional layer is higher than that of the second functional layer, and the oxygen vacancy concentration of the second functional layer is higher than that of the third functional layer.

[0112]

Example 5

[0113]

Example 6

[0114] The seed layer was made of IZO. The seed layer was prepared by magnetron sputtering, with a power of 300 W, a sputtering time of 5 s, and a gas flow rate of 50 sccm (where oxygen was 0% and argon was 100% by volume). X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration in the seed layer was higher than that in the second functional layer.

[0115]

Example 7

[0116] The seed layer is made of IZO and is prepared by magnetron sputtering. The magnetron sputtering power is 300 W, the sputtering time is 5 s, and the gas flow rate is 50 sccm (where oxygen is 0% by volume and argon is 100% by volume).

[0117] Comparative Example 1 The difference from Example 1 is that the composite layer is replaced with a first functional layer with a thickness of 30 nm.

[0118] The first functional layer is made of IZO, the magnetron sputtering power is 300 W, the sputtering time is 80 s, and the gas flow rate is 50 sccm (of which, the volume fraction of oxygen in the sputtering gas is 5%, and the volume fraction of argon in the sputtering gas is 95%).

[0119] Comparative Example 2 The difference from Example 1 is that the composite layer is replaced with a second functional layer with a thickness of 30 nm.

[0120] The first functional layer is made of IZO, the magnetron sputtering power is 300 W, the sputtering time is 80 s, and the gas flow rate is 50 sccm (of which, the volume fraction of oxygen in the sputtering gas is 10% and the volume fraction of argon in the sputtering gas is 90%).

[0121]

Example 8

[0122] In the preparation of the first functional layer, the volume fraction of hydrogen in the sputtering gas is 0.1%, and the volume fraction of argon in the sputtering gas is 99.9%. During the preparation of the second functional layer, the volume fraction of oxygen in the sputtering gas was 5%, and the volume fraction of argon in the sputtering gas was 95%. X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration of the first functional layer was higher than that of the second functional layer.

[0123]

Example 9

[0124] In the preparation of the first functional layer, the volume fraction of hydrogen in the sputtering gas is 0.5%, and the volume fraction of argon in the sputtering gas is 99.5%. During the preparation of the second functional layer, the volume fraction of oxygen in the sputtering gas was 5%, and the volume fraction of argon in the sputtering gas was 95%. X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration of the first functional layer was higher than that of the second functional layer.

[0125]

Example 10

[0126] In the preparation of the first functional layer, the volume fraction of hydrogen in the sputtering gas is 0.1%, the volume fraction of oxygen in the sputtering gas is 3%, and the volume fraction of argon in the sputtering gas is 96.9%. During the preparation of the second functional layer, the volume fraction of oxygen in the sputtering gas was 5%, and the volume fraction of argon in the sputtering gas was 95%. X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration of the first functional layer was higher than that of the second functional layer.

[0127]

Example 11

[0128]

Example 12

[0129] The seed layer was made of ITO and prepared by magnetron sputtering. The magnetron sputtering power was 300 W, the sputtering time was 5 s, and the gas flow rate was 50 sccm (where oxygen was 0% by volume and argon was 100% by volume). X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration in the seed layer was higher than that in the second functional layer.

[0130]

Example 13

[0131] The seed layer was made of ITO and prepared by magnetron sputtering. The magnetron sputtering power was 300 W, the sputtering time was 5 s, and the gas flow rate was 50 sccm (where oxygen was 0% and argon was 100% by volume). X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration in the seed layer was higher than that in the third functional layer.

[0132] Comparative Example 3 The difference from Example 8 is that the composite layer is replaced with a first functional layer with a thickness of 30 nm.

[0133] The first functional layer is IZO, the magnetron sputtering power is 300 W, the sputtering time is 80 s, and the gas flow rate is 50 sccm (of which, the volume fraction of hydrogen in the sputtering gas is 0.1%, and the volume fraction of argon in the sputtering gas is 99.9%).

[0134]

Example 14

[0135] In the preparation of the first functional layer, the volume fraction of hydrogen in the sputtering gas is 0.1%, and the volume fraction of argon in the sputtering gas is 99.9%. During the preparation of the second functional layer, the volume fraction of hydrogen in the sputtering gas was 0.05%, and the volume fraction of argon in the sputtering gas was 99.95%. X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration of the first functional layer was higher than that of the second functional layer.

[0136]

Example 15

[0137] In the preparation of the first functional layer, the volume fraction of hydrogen in the sputtering gas is 1%, and the volume fraction of argon in the sputtering gas is 99%. During the preparation of the second functional layer, the volume fraction of hydrogen in the sputtering gas was 0.6%, and the volume fraction of argon in the sputtering gas was 99.4%. X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration of the first functional layer was higher than that of the second functional layer.

[0138]

Example 16

[0139] In the preparation of the first functional layer, the volume fraction of hydrogen in the sputtering gas is 0.5%, and the volume fraction of argon in the sputtering gas is 99.5%. During the preparation of the second functional layer, the volume fraction of hydrogen in the sputtering gas was 0.1%, and the volume fraction of argon in the sputtering gas was 99.9%. X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration of the first functional layer was higher than that of the second functional layer.

[0140]

Example 17

[0141] In the preparation of the first functional layer, the volume fraction of hydrogen in the sputtering gas is 1%, and the volume fraction of argon in the sputtering gas is 99%. During the fabrication of the second functional layer, the volume fraction of hydrogen in the sputtering gas was 0.5%, and the volume fraction of argon in the sputtering gas was 99.5%. During the preparation of the third functional layer, the volume fraction of hydrogen in the sputtering gas was 0.1%, and the volume fraction of argon in the sputtering gas was 99.9%. X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration of the first functional layer was higher than that of the second functional layer, and the oxygen vacancy concentration of the second functional layer was higher than that of the third functional layer.

[0142]

Example 18

[0143] The seed layer was made of ITO and prepared by magnetron sputtering. The magnetron sputtering power was 300 W, the sputtering time was 5 s, and the gas flow rate was 50 sccm (where oxygen was 0% by volume and argon was 100% by volume). X-ray photoelectron spectroscopy results showed that the oxygen vacancy concentration in the seed layer was higher than that in the second functional layer.

[0144] The short-circuit current, open-circuit voltage, fill factor, and light conversion efficiency of the solar tandem cells obtained in Examples 1-18 and Comparative Examples 1-3 were tested. Table 1 Performance test results of perovskite / crystalline silicon tandem solar cells obtained in Examples 1-18 and Comparative Examples 1-3

[0145] The comparison of Examples 1-5 shows that introducing multiple functional layers into a solar tandem cell, with the work function of each functional layer increasing from bottom to top, can effectively improve the energy level arrangement of the hole transport layer and the functional layer, enhance charge transport, and strengthen the anchoring effect of the self-assembled monomolecule material of the hole transport layer on the surface of the functional layer, thereby improving the light conversion efficiency of the solar tandem cell.

[0146] By comparing Examples 1 and 6, and Examples 4 and 7, it can be seen that by setting a seed layer between the composite layer and the hole transport layer, the chemical state of the TCO surface can be further optimized, the anchoring density and order of the self-assembled monomolecule material can be significantly enhanced, the interfacial contact resistance can be reduced, and the defect states of the TCO surface can be passivated. Thus, on the basis of the multilayer gradient structure, the open-circuit voltage and fill factor of the device can be synergistically improved, and the light conversion efficiency of the battery can be further improved.

[0147] The comparison between Example 1 and Comparative Examples 1-2 shows that when the composite layer is a single functional layer and does not involve a change in the work function gradient, an effective energy level transition channel cannot be formed, resulting in a high charge extraction barrier at the interface, which triggers severe nonradiative recombination at the interface. This leads to a significant deterioration in the open-circuit voltage and fill factor of the battery, ultimately resulting in a decrease in light conversion efficiency.

[0148] A comparison of Examples 1 and 8-11 shows that using a hydrogen-oxygen mixture can also regulate the work function of the functional layer, thereby improving the light conversion efficiency of the solar tandem cell.

[0149] A comparison of Examples 8 and 12, and Examples 11 and 13 shows that even in a system using a hydrogen-oxygen mixture for work function regulation, by setting a seed layer between the composite layer and the hole transport layer, an oxygen-free, metal-rich interface can be further provided. This interface has a stronger chemical affinity for the phosphonic acid groups of the self-assembled monomolecular material, thereby achieving significant improvement in interface properties in addition to the bulk energy level optimization brought about by gas regulation, and further enhancing the light conversion efficiency of the battery.

[0150] The comparison between Example 8 and Comparative Example 3 shows that when the composite layer is a single functional layer and does not involve changes in the work function gradient, an effective energy level transition channel cannot be formed, resulting in a high charge extraction barrier at the interface, which leads to severe nonradiative recombination at the interface. This causes a significant deterioration in the open-circuit voltage and fill factor of the battery, ultimately resulting in a decrease in light conversion efficiency.

[0151] A comparison of Examples 1 and 14-17 shows that hydrogen gas can also be used to regulate the work function of the functional layer and improve the light conversion efficiency of solar tandem cells.

[0152] A comparison of Examples 14 and 18 shows that even in systems where work function is regulated using hydrogen, by setting a seed layer between the composite layer and the hole transport layer, an oxygen-free, metal-rich interface can be further provided. This interface has a stronger chemical affinity for the phosphonic acid groups of the self-assembled monomolecular material, thereby achieving significant improvement in interface properties in addition to the bulk energy level optimization brought about by gas regulation, and further enhancing the light conversion efficiency of the battery.

[0153] The comparison between Example 14 and Comparative Example 3 shows that when the composite layer is a single functional layer and does not involve changes in the work function gradient, an effective energy level transition channel cannot be formed, resulting in a high charge extraction barrier at the interface, which leads to severe nonradiative recombination at the interface. This causes a significant deterioration in the open-circuit voltage and fill factor of the battery, ultimately resulting in a decrease in light conversion efficiency.

[0154] This application embodiment can also provide a photovoltaic module (not shown), which includes the solar tandem cells as described above. The solar tandem cells can be connected in series and / or in parallel with one or more other solar tandem cells in a predetermined manner. Multiple cells can form a cell string, and adjacent cells can be connected together by string welding.

[0155] This application provides a photovoltaic system including the photovoltaic modules described in any of the above embodiments. The advantages of the aforementioned photovoltaic modules are also present in this photovoltaic system, and will not be repeated here. The application fields of the aforementioned photovoltaic system are wide, not limited to photovoltaic power plants, such as ground-mounted power plants, rooftop power plants, and floating power plants, but also including various devices and apparatuses that utilize solar energy for power generation, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system are not limited to these; that is, the photovoltaic system can be applied in all fields that require solar energy for power generation. Taking a photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may be an array combination of multiple photovoltaic modules; for example, multiple photovoltaic modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the combiner box, which can collect the current generated by the photovoltaic array. The collected current flows through the inverter and is converted into AC power required by the mains power grid before being connected to the mains power grid to achieve solar power supply.

[0156] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0157] It should also be noted that the above are merely preferred embodiments of this application and do not limit the scope of patent protection of this application. Any equivalent structural or procedural changes made using the content of this application’s specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A solar tandem battery, characterized in that, The solar tandem battery includes a bottom battery, a composite layer, and a top battery stacked together. The composite layer includes multiple functional layers stacked together, wherein the work function of the multiple functional layers increases in the direction from the bottom cell to the top cell.

2. The solar tandem battery according to claim 1, characterized in that, The functional layer satisfies at least one of the following characteristics: The number of functional layers is 2-5; The thickness of each of the functional layers is 3-15 nm; The functional layer is made of a transparent conductive oxide material; The transparent conductive oxide material includes any one or a combination of at least two of the following: indium tin oxide, indium zinc oxide, tungsten-doped indium oxide, zirconium-doped indium oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, or gallium-doped zinc oxide. The oxygen vacancy concentration of the multilayer functional layers decreases along the direction from the bottom cell to the top cell.

3. The solar tandem battery according to claim 1, characterized in that, A seed layer is disposed between the top battery and the composite layer, and the seed layer satisfies at least one of the following characteristics: The thickness of the seed layer is 1-3 nm; The oxygen vacancy concentration of the seed layer is higher than that of the functional layer connected to the seed layer. The seed layer is made of a transparent conductive oxide material; The transparent conductive oxide material includes any one or a combination of at least two of the following: indium tin oxide, indium zinc oxide, tungsten-doped indium oxide, zirconium-doped indium oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, or gallium-doped zinc oxide.

4. The solar tandem battery according to claim 1, characterized in that, The bottom cell is a crystalline silicon bottom cell, and the top cell is a perovskite top cell; Along the direction from the bottom cell to the top cell, the top cell includes a stacked hole transport layer, a perovskite absorber layer, and an electron transport layer, wherein the hole transport layer is made of a self-assembled monomolecule material.

5. A method for preparing a solar tandem cell, characterized in that, The preparation method includes: A multi-layered functional layer is formed on the surface of the bottom cell by using a multi-pass magnetron sputtering process to obtain a composite layer; A top cell is formed on the surface of the composite layer away from the bottom cell to obtain the solar tandem cell; In this process, by controlling the volume fraction of the reactive gas in the sputtering gas to change successively, the work function of the multilayer functional layer increases in the direction from the bottom cell to the top cell.

6. The preparation method according to claim 5, characterized in that, The magnetron sputtering process has a sputtering power of 100-800 W, a sputtering time of 5-60 s, and a sputtering gas flow rate of 30-500 sccm.

7. The preparation method according to claim 5, characterized in that, The reactant gas includes oxygen and / or hydrogen. During the fabrication of the multilayer functional layers along the direction from the bottom cell to the top cell, the volume fraction of oxygen in the sputtering gas increases sequentially, and / or the volume fraction of hydrogen in the sputtering gas decreases sequentially.

8. The preparation method according to any one of claims 5 to 7, characterized in that, When the functional layer adjacent to the bottom battery is fabricated, the oxygen in the sputtering gas has a volume fraction of 0.1-10%. And / or, when the functional layer adjacent to the top battery is prepared, the oxygen in the sputtering gas has a volume fraction of 1-20%; And / or, when the functional layer adjacent to the bottom battery is prepared, the volume fraction of hydrogen in the sputtering gas is 0.1-1%; And / or, when the functional layer adjacent to the top battery is prepared, the volume fraction of hydrogen in the sputtering gas is 0-0.6%.

9. The preparation method according to claim 5, characterized in that, Before forming the top cell on the surface of the composite layer away from the bottom cell, the method further includes: A seed layer is formed on the surface of the composite layer away from the bottom cell using a magnetron sputtering process; wherein the magnetron sputtering process for preparing the seed layer satisfies at least one of the following characteristics: The volume fraction of oxygen in the sputtering gas is lower than the volume fraction of oxygen in the sputtering gas when forming the functional layer connected to the seed layer, such that the oxygen vacancy concentration of the seed layer is higher than the oxygen vacancy concentration of the functional layer connected to the seed layer. The oxygen volume fraction in the sputtering gas is 0-3%.

10. A photovoltaic module, characterized in that, The photovoltaic module includes the solar tandem cell as described in any one of claims 1-4.

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