Method for forming a hole transport layer on a substrate surface, hole transport layer, solar cell and method for producing the same, photovoltaic module

Abstract

The application provides a method for forming a hole transport layer on a substrate surface, a hole transport layer, a solar cell and a preparation method thereof, and a photovoltaic module. The method for forming a hole transport layer on a substrate surface comprises the following steps: providing M targets comprising inorganic hole transport materials; forming a hole transport layer comprising at least N continuous sub-layers on the substrate surface by using a magnetron sputtering principle, 2≤N≤M, and at least one of the M targets is a doped target comprising a doping material. The application can improve the stability and consistency of the solar cell, and the energy level structure of the hole transport layer in the solar cell can be conveniently adjusted, thereby facilitating the energy level matching and optimization between the light absorption layer and the hole transport layer.

Description

Technical Field

[0001] This application belongs to the field of solar cell technology, specifically relating to a method for forming a hole transport layer on a substrate surface, the hole transport layer, a solar cell and its fabrication method, and a photovoltaic module. Background Technology

[0002] With the development of modern industry, global energy shortages and environmental pollution have become increasingly prominent, making solar cells, as an ideal renewable energy source, increasingly important. Solar cells, also known as photovoltaic cells, are devices that directly convert light energy into electrical energy through the photoelectric effect or photochemical effect. Perovskite solar cells utilize perovskite materials as the light-absorbing layer. Within a few years of their invention, they rapidly achieved high energy conversion efficiency and have received widespread attention in recent years. Although the energy conversion efficiency of perovskite solar cells has now exceeded 21%, their stability remains a stumbling block to their commercialization. Therefore, improving the stability of solar cells remains an urgent problem to be solved. Summary of the Invention

[0003] The purpose of this application is to provide a method for forming a hole transport layer on a substrate surface, a hole transport layer, a solar cell and its fabrication method, and a photovoltaic module, which aims to improve the stability and consistency of the solar cell, and to facilitate the adjustment of the energy level structure of the hole transport layer in the solar cell, thereby benefiting the energy level matching and optimization between the light-absorbing layer and the hole transport layer.

[0004] The first aspect of this application provides a method for forming a hole transport layer on a substrate surface, comprising the steps of: providing M targets comprising inorganic hole transport materials, forming a hole transport layer comprising at least N consecutive sublayers on the substrate surface using the principle of magnetron sputtering, wherein 2≤N≤M, and at least one of the M targets is a doped target further comprising doped materials.

[0005] The inventors of this application, for the first time, composite inorganic hole transport materials and dopant materials to form doped targets. Using magnetron sputtering, each target is plasma-plated and subsequently sequentially sprayed onto a substrate to form a hole transport layer. The method of this application also allows for convenient adjustment of the specific composition of the target materials or replacement of the target materials to form the desired hole transport layer. Compared with coating film preparation methods, the method of forming a hole transport layer in this application is simpler and yields a more stable and consistent hole transport layer. The method of this application allows for convenient and accurate adjustment of the composition of each target material (e.g., adjusting the type and / or content of the inorganic hole transport material, the type and / or content of the dopant material, etc.) according to actual needs to obtain a hole transport layer with the desired energy level.

[0006] In any embodiment of this application, the inorganic hole transport material of each target is of the same type.

[0007] In any embodiment of this application, the inorganic hole transport material is a P-type semiconductor.

[0008] In any embodiment of this application, the inorganic hole transport material is selected from NiO. x The inorganic hole transport material is selected from one of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3. Optionally, the inorganic hole transport material is selected from NiO. x .

[0009] In any embodiment of this application, the types of doped materials of each doped target may be the same or different from each other.

[0010] In any embodiment of this application, the doping material of each doped target is independently selected from NiO. x One or more of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3.

[0011] In any embodiment of this application, the first target or the Mth target is a doped target, and the doping material includes at least KI.

[0012] In any embodiment of this application, based on the mass of each doped target, the total mass percentage of the doped material in each doped target is ≤25%. Optionally, the total mass percentage of the doped material in each doped target is 0.1% to 25%.

[0013] In any embodiment of this application, when the doped target includes NiO x When the dopant is selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, Ag, and Ag2O, the mass percentage of the dopant material in the doped target independently satisfies ≤15%.

[0014] In any embodiment of this application, when the doped target includes one or both of MgO and KI, the mass percentage of the dopant material in the doped target independently satisfies ≤20%.

[0015] In any embodiment of this application, when the doped target includes one or both of MnO and MnO2, the mass percentage of the doped material in the doped target independently satisfies ≤10%.

[0016] In any embodiment of this application, when the doped target includes one or both of Co and CoO, the mass percentage of the doped material in the doped target independently satisfies ≤8%.

[0017] In any embodiment of this application, when the doped target includes one or more of Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, the mass percentage of the doped material in the doped target independently satisfies ≤25%.

[0018] In any embodiment of this application, the hole transport layer has gradient-varying energy levels. By adjusting the type and / or content of inorganic hole transport materials and the type and / or content of doped materials in each target, parameters such as the bandgap and conduction band bottom energy level of each target can be conveniently and precisely adjusted so that the hole transport layer satisfies one or more of the gradient-varying (e.g., gradient increasing or decreasing) bandgap and conduction band bottom energy level, thereby improving the hole collection and transport capability of the hole transport layer.

[0019] In any embodiment of this application, the hole transport layer has a gradient-varying bandgap width, the M targets have gradient-varying bandgap widths, and the absolute value of the difference between the bandgap widths of two adjacent targets, |ΔEg(TAG)|, satisfies: 0eV≤|ΔEg(TAG)|≤1.5eV.

[0020] In any embodiment of this application, the hole transport layer has a gradient-varying conduction band bottom energy level, the M targets have gradient-varying conduction band bottom energy levels, and the absolute value of the difference between the conduction band bottom energy levels of two adjacent targets, |ΔCBM(TAG)|, satisfies: 0eV≤|ΔCBM(TAG)|≤1.5eV.

[0021] In any embodiment of this application, the hole transport layer has a gradient-varying bandgap and conduction band bottom level, the M targets have gradient-varying bandgap and conduction band bottom level, and the absolute value of the difference between the bandgap of two adjacent targets, |ΔEg(TAG)|, satisfies: 0eV≤|ΔEg(TAG)|≤1.5eV, and the absolute value of the difference between the conduction band bottom levels of two adjacent targets, |ΔCBM(TAG)|, satisfies: 0eV≤|ΔCBM(TAG)|≤1.5eV.

[0022] In any embodiment of this application, the substrate is a transparent electrode, a metal electrode, or a conductive carbon electrode. Optionally, the transparent electrode is an FTO conductive glass electrode or an ITO conductive glass electrode. Optionally, the metal electrode is selected from one or two of gold, silver, aluminum, and copper electrodes.

[0023] In any embodiment of this application, magnetron sputtering satisfies: sputtering gas pressure 2×10 -3 mbar~8×10 -3 mbar.

[0024] In any embodiment of this application, magnetron sputtering satisfies the following condition: gas flow rate is 50 sccm to 250 sccm.

[0025] In any embodiment of this application, magnetron sputtering satisfies the following condition: the heating temperature is 0℃~200℃.

[0026] In any embodiment of this application, magnetron sputtering satisfies the following condition: sputtering power is 200W to 13KW.

[0027] In any embodiment of this application, magnetron sputtering satisfies the following condition: the target-substrate spacing is 60mm to 120mm.

[0028] A second aspect of this application provides a hole transport layer for a solar cell, comprising at least N consecutive sublayers, where N ≥ 2, wherein each sublayer comprises an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer that also comprises a doping material.

[0029] The hole transport layer of this application has a gently varying energy level gradient, which is beneficial for energy level matching and optimization between the light-absorbing layer and the hole transport layer, and also for improving the performance of the solar cell. The bandgap width and the position of the conduction band bottom energy level of the hole transport layer of this application can be adjusted, thereby improving the hole collection and transport capabilities of the hole transport layer.

[0030] In any embodiment of this application, 2 ≤ N ≤ 10.

[0031] In any embodiment of this application, the inorganic hole transport material of each sublayer is of the same type.

[0032] In any embodiment of this application, the inorganic hole transport material is a P-type semiconductor.

[0033] In any embodiment of this application, the inorganic hole transport material is selected from NiO. xThe inorganic hole transport material is selected from one of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3. Optionally, the inorganic hole transport material is selected from NiO. x .

[0034] In any embodiment of this application, the types of doped materials in each sub-doped layer may be the same or different from each other.

[0035] In any embodiment of this application, the doping material of each sub-doped layer is independently selected from NiO. x One or more of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3.

[0036] In any embodiment of this application, the first sublayer or the Nth sublayer is a sub-doped layer, and the doping material includes at least KI.

[0037] In any embodiment of this application, based on the quality of each sub-doped layer, the total mass percentage of doped material in each sub-doped layer is ≤25%. Optionally, the total mass percentage of doped material in each sub-doped layer is 0.1% to 25%.

[0038] In any embodiment of this application, when the sub-doped layer includes NiO x When the dopant is selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, Ag, and Ag2O, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤15%.

[0039] In any embodiment of this application, when the sub-doped layer includes one or both of MgO and KI, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤20%.

[0040] In any embodiment of this application, when the sub-doped layer includes one or both of MnO and MnO2, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤10%.

[0041] In any embodiment of this application, when the sub-doped layer includes one or both of Co and CoO, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤8%.

[0042] In any embodiment of this application, when the sub-doped layer includes one or more of Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, the mass percentage of the doping material in the sub-doped layer independently satisfies ≤25%.

[0043] In any embodiment of this application, the N sub-layers have bandgap widths that increase or decrease with gradients, and the absolute value of the difference between the bandgap widths of two adjacent sub-layers, |ΔEg(HTL)|, satisfies: 0eV<|ΔEg(HTL)|≤1.5eV.

[0044] In any embodiment of this application, the N sublayers have conduction band bottom energy levels with increasing or decreasing gradients, and the absolute value of the difference between the conduction band bottom energy levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0eV<|ΔCBM(HTL)|≤1.5eV.

[0045] In any embodiment of this application, the N sublayers have a gradient increasing or decreasing bandgap width and conduction band bottom level, and the absolute value of the difference between the bandgap widths of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0eV < |ΔEg(HTL)| ≤ 1.5eV, and the absolute value of the difference between the conduction band bottom levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0eV < |ΔCBM(HTL)| ≤ 1.5eV.

[0046] In any embodiment of this application, the total thickness of the hole transport layer is 5 nm to 150 nm. Optionally, the total thickness of the hole transport layer is 10 nm to 80 nm.

[0047] A third aspect of this application provides a solar cell, including a hole transport layer prepared according to the method of the first aspect of this application, or a hole transport layer of the second aspect of this application.

[0048] The fourth aspect of this application provides a method for fabricating a solar cell, including the method of the first aspect of this application for forming a hole transport layer on a substrate surface.

[0049] The fifth aspect of this application provides a photovoltaic module, including the solar cell of the third aspect of this application.

[0050] The solar cell of this application includes a hole transport layer with a gently varying energy level gradient, which facilitates energy level matching and optimization between the light-absorbing layer and the hole transport layer, thereby improving the performance of the solar cell. The bandgap width and conduction band bottom of the hole transport layer are adjustable, further enhancing its hole collection and transport capabilities. The photovoltaic module of this application includes the solar cell provided in this application and therefore possesses at least the same advantages as the solar cell described above. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of one embodiment of the solar cell of this application.

[0053] Figure 2 This is a schematic diagram of another embodiment of the solar cell of this application.

[0054] Figure 3 This is a schematic diagram of the energy level distribution of the solar cell in Example 1. Detailed Implementation

[0055] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the method for forming a hole transport layer on a substrate surface, the hole transport layer itself, the solar cell and its fabrication method, and the photovoltaic module. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0056] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0057] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0058] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0059] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0060] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0061] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0062] Solar energy, as a clean and renewable energy source, has the advantage of being inexhaustible, thus solar energy research occupies an important position in energy strategy. Solar cells, as an ideal renewable energy source, are receiving increasing attention. Currently, solar cells have expanded from simple lighting applications to aerospace, transportation, power, communications, and portable and wearable devices.

[0063] The stability of solar cells remains a stumbling block to their commercialization. Taking perovskite solar cells as an example, perovskite materials are relatively unstable in humid environments and under light conditions, easily decomposing and causing a decrease in solar cell energy conversion efficiency or even solar cell failure. Besides improving the stability of the perovskite material itself, another feasible solution to improve the stability of solar cells is to provide a hole transport layer with higher stability and consistency to suppress the decomposition of the perovskite material.

[0064] To obtain a hole transport layer with higher stability and consistency, existing technologies employ a method of first coating to form a film and then annealing at high temperature to create the hole transport layer. However, this preparation process is complex, has a narrow process window, and requires stringent reaction conditions, necessitating precise control of the concentration of each component in the reaction solution. Furthermore, because this process is a single-wafer, single-batch preparation process, the reaction solution needs to be prepared independently for each wafer, resulting in poor consistency between different batches of samples. In addition, the coating-film preparation process limits its application to large-scale, large-size products.

[0065] Method for forming a hole transport layer on a substrate surface

[0066] In view of the above problems, a first aspect of the present application provides a method for forming a hole transport layer on a substrate surface, which can achieve high stability and high consistency of the fabrication process, and the energy level structure of the hole transport layer can be easily adjusted. The method for forming a hole transport layer on a substrate surface includes the steps of: providing M targets comprising inorganic hole transport materials; forming a hole transport layer comprising at least N consecutive sublayers on the substrate surface using magnetron sputtering, where 2 ≤ N ≤ M; and at least one of the M targets is a doped target further comprising doped materials.

[0067] Magnetron sputtering can be performed in a magnetron sputtering chamber. The substrate is mounted on the anode of the magnetron sputtering chamber and can be driven forward. The M targets are sequentially mounted and fixed on the cathode of the magnetron sputtering chamber. During magnetron sputtering, when the substrate moves forward and passes the first target, a first sublayer with the same composition (including the types and contents of each component) as the first target is formed on the substrate surface. As the substrate moves forward, a second sublayer with the same composition as the second target is formed on the basis of the first sublayer, and so on, until an Nth sublayer with the same composition as the Mth target is formed on the basis of the (N-1)th sublayer, where 2≤N≤M.

[0068] M > N indicates that two or more adjacent targets are identical, and these targets together form one of the sublayers of the hole transport layer. For example, to increase the thickness of one of the sublayers of the hole transport layer, two adjacent targets are made to be exactly the same.

[0069] M = N indicates that the M targets correspond one-to-one with the N sublayers, that is, the first target is used to form the first sublayer, the second target is used to form the second sublayer, and so on.

[0070] The inventors of this application, for the first time, composite inorganic hole transport materials and doped materials to form a doped target. Using magnetron sputtering, each target is plasma-plated and subsequently sequentially sprayed onto a substrate to form a hole transport layer. The method of this application also allows for convenient adjustment of the specific composition of the target or replacement of the target to form the desired hole transport layer. Compared with coating methods, the method for forming a hole transport layer in this application is simpler and yields a hole transport layer with higher stability and consistency.

[0071] At least one of the M targets further includes a doped material to form a doped target. In some embodiments, M-1 of the M targets include a doped material to form a doped target; and one of the M targets does not include a doped material, serving as an undoped target. In other embodiments, all M targets include a doped material to form a doped target.

[0072] The method of this application can conveniently and accurately adjust the composition of each target material (e.g., adjust the type and / or content of inorganic hole transport materials, the type and / or content of doped materials, etc.) according to actual needs to obtain a hole transport layer with the required energy level.

[0073] By adjusting the composition of each target material (e.g., adjusting the type and / or content of inorganic hole transport materials, the type and / or content of doping materials, etc.), a gently varying energy level gradient can be achieved in the resulting hole transport layer. This facilitates energy level matching and optimization between the light-absorbing layer and the hole transport layer, thereby improving the performance of the solar cell. Furthermore, adjusting the composition of each target material (e.g., adjusting the type and / or content of inorganic hole transport materials, the type and / or content of doping materials, etc.) also allows for convenient and precise adjustment of the bandgap and conduction band bottom of each target material, thereby enhancing the hole collection and transport capabilities of the hole transport layer.

[0074] The method of this application can conveniently and accurately adjust the energy level structure of the hole transport layer according to actual needs, resulting in a variety of different hole transport layers. This provides a very wide adjustment window for the performance optimization and design of the hole transport layer, and can further expand the performance optimization space of solar cells and enhance the contribution space of the hole transport layer to the improvement of solar cell performance.

[0075] The method of this application can effectively improve the fabrication process window of hole transport layers and achieve process stability and consistency when fabricating hole transport layers in batches.

[0076] The method described in this application enables the fabrication of large-scale, large-size hole transport layers.

[0077] The method of this application can realize the simultaneous hole transport layer coating process and annealing process, reducing the process flow.

[0078] The method of this application can maintain the cleanliness of the obtained hole transport layer, which is beneficial to improving the performance of solar cells.

[0079] The method described in this application does not have any safety or environmental issues related to organic solvents.

[0080] In some embodiments, N is a range consisting of any number of values ​​from 2, 3, 4, 5, 6, 7, 8, 9, 10 or above. Optionally, 2≤N≤10, 3≤N≤10, 4≤N≤10, 5≤N≤10, 2≤N≤9, 2≤N≤8, 2≤N≤7, 2≤N≤6, 2≤N≤5, or 2≤N≤5.

[0081] In some embodiments, each target material is introduced into the plasma generator sprayer of the magnetron sputtering chamber in powder or wire form, and is then sequentially sprayed onto the substrate after plasmaization to form a hole transport layer.

[0082] In some embodiments, the M targets are arranged in a continuous manner, an intermittent manner, or a partially continuous and partially intermittent manner.

[0083] In some embodiments, the inorganic hole transport material of each target is of the same type.

[0084] In some embodiments, the inorganic hole transport material may be a p-type semiconductor. As an example, the inorganic hole transport material is selected from nickel oxide (NiO). x The inorganic hole transport material is selected from one of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3. Optionally, the inorganic hole transport material is selected from NiO. x .

[0085] In some embodiments, the inorganic hole transport material of each doped target is the same type, or the doping material is the same type or different type.

[0086] For example, in some embodiments, the inorganic hole transport material of each doped target is the same type, and the doping material is different type; in other embodiments, the inorganic hole transport material of each doped target is the same type, and the doping material is not completely the same type. For example, each doped target contains at least one identical doping material and at least one different doping material.

[0087] As an example, the doping material of each doped target is independently selected from NiO. x One or more of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3.

[0088] In some embodiments, based on the mass of each doped target, the total mass percentage of the doped material in each doped target is ≤25%, for example, ≤24%, ≤23%, ≤22%, ≤21%, ≤20%, ≤19%, ≤18%, ≤17%, ≤16%, ≤15%, ≤14%, ≤13%, ≤12%, ≤11%, ≤10%, ≤9%, ≤8%, ≤7%, ≤6%, or ≤5%. Optionally, the total mass percentage of the doped material in each doped target is 0.1%–25%, 0.1%–22.5%, 0.1%–20%, 0.1%–17.5%, 0.1%–15%, 0.1%–12.5%, 0.1%–10%, 0.1%–7.5%, or 0.1%–5%.

[0089] NiO xCuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3 can be used as inorganic hole transport materials or as dopant materials for specific inorganic hole transport materials. The difference lies in their mass percentage content in each target (or doped target) when used as an inorganic hole transport material, for example, greater than 75%, optionally between 75% and 100%; while when used as a dopant material for a specific inorganic hole transport material, the mass percentage content in each doped target is lower, for example, ≤25%.

[0090] In some embodiments, when the doped target includes NiO x When one or more of the following are selected: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, Ag, and Ag2O, the mass percentage of each dopant material in the doped target independently satisfies ≤15%. Among them, NiO... x CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, and Ag2O are used here as dopants for certain inorganic hole transport materials in the target material.

[0091] In some embodiments, when the doped target includes one or both of MgO and KI, the mass percentage of the dopant material in the doped target independently satisfies ≤20%.

[0092] In some embodiments, when the doped target includes one or both of MnO and MnO2, the mass percentage of each dopant material in the doped target independently satisfies ≤10%. Here, MnO and MnO2 are dopant materials that serve as inorganic hole transport materials in the target.

[0093] In some embodiments, when the doped target includes one or both of Co and CoO, the mass percentage of each dopant material in the doped target independently satisfies ≤8%. Here, CoO is a dopant material that serves as an inorganic hole transport material in the target.

[0094] In some embodiments, when the doped target includes one or more of Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, the mass percentage of each dopant in the doped target independently satisfies ≤25%. Here, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3 are dopant materials used as inorganic hole transport materials in the target.

[0095] The energy levels of each target (e.g., band gap, conduction band bottom level, etc.) can be obtained by adjusting the type and / or content of inorganic hole transport materials and the type and / or content of doped materials in each target.

[0096] In order to obtain the desired energy level (e.g., band gap, conduction band bottom, etc.), the type and content of the doping material of each doped target can be selected from the above doping materials and their contents as needed. The doping material can be one type or a combination of multiple types.

[0097] In some embodiments, the first target or the Mth target is a doped target, and the doping material includes at least KI. In this case, the surface defects of the obtained hole transport layer can be reduced to promote the subsequent deposition and crystallization of perovskite materials.

[0098] In some embodiments, the hole transport layer has gradient-varying energy levels. For example, the hole transport layer satisfies one or more of a gradient-varying bandgap and conduction band bottom energy level. By adjusting the type and / or content of inorganic hole transport materials and the type and / or content of doping materials in each target, parameters such as the bandgap and conduction band bottom energy level of each target can be conveniently and precisely adjusted so that the hole transport layer satisfies one or more of a gradient-varying (e.g., gradient increasing or decreasing) bandgap and conduction band bottom energy level, thereby improving the hole collection and transport capability of the hole transport layer.

[0099] As an example, in some embodiments, the hole transport layer has a gradient-varying bandgap, the M targets have gradient-varying bandgap, and the absolute value of the difference between the bandgap of two adjacent targets, |ΔEg(TAG)|, satisfies: 0 eV ≤ |ΔEg(TAG)| ≤ 1.5 eV. In other embodiments, the hole transport layer has a gradient-varying conduction band bottom level, the M targets have gradient-varying conduction band bottom levels, and the absolute value of the difference between the conduction band bottom levels of two adjacent targets, |ΔCBM(TAG)|, satisfies: 0 eV ≤ |ΔCBM(TAG)| ≤ 1.5 eV. In some other embodiments, the hole transport layer has a gradient-varying bandgap and conduction band bottom level, the M targets have gradient-varying bandgap and conduction band bottom level, and the absolute value of the difference between the bandgap of two adjacent targets, |ΔEg(TAG)|, satisfies: 0eV≤|ΔEg(TAG)|≤1.5eV, and the absolute value of the difference between the conduction band bottom levels of two adjacent targets, |ΔCBM(TAG)|, satisfies: 0eV≤|ΔCBM(TAG)|≤1.5eV.

[0100] In some embodiments, the magnetron sputtering may be pulsed magnetron sputtering, DC magnetron sputtering, RF magnetron sputtering, medium frequency magnetron sputtering, or a combination of magnetron sputtering.

[0101] In some embodiments, magnetron sputtering satisfies the following condition: the sputtering gas pressure is 2 × 10⁻⁶. -3 mbar~8×10 -3 mbar.

[0102] In some embodiments, magnetron sputtering satisfies the following: gas flow rate of 50 sccm to 250 sccm.

[0103] In some embodiments, magnetron sputtering satisfies the following condition: the heating temperature is 0°C to 200°C.

[0104] In some embodiments, magnetron sputtering satisfies the following: sputtering power is 200W to 13KW.

[0105] In some embodiments, magnetron sputtering satisfies the following: the target-substrate spacing is 60 mm to 120 mm.

[0106] In some embodiments, the magnetron sputtering process may be performed under the following conditions: sputtering gas pressure 2 × 10⁻⁶. -3 mbar~8×10 -3 mbar, gas flow rate 50sccm~250sccm, heating temperature 0℃~200℃, sputtering power 200W~13KW, target-substrate spacing 60mm~120mm.

[0107] In some embodiments, the working gas for magnetron sputtering is selected from one or both of O2 and Ar. Optionally, the volume ratio of O2 to Ar is 1% to 90%. The working gas used for magnetron sputtering of different targets may be the same or different, and can be selected according to actual needs.

[0108] The magnetron sputtering conditions for each target material can be the same or different. For example, in order to increase or decrease the thickness of one of the sublayers of the hole transport layer, the sputtering power or sputtering pressure of the target material corresponding to that sublayer can be increased or decreased individually.

[0109] In some embodiments, the substrate advances at a speed of 0.1 mm / s to 50 cm / s. The substrate can advance at a uniform speed or a non-uniform speed. For example, to increase or decrease the thickness of one of the sublayers of the hole transport layer, the advance speed of the substrate as it passes through the target material corresponding to that sublayer can be increased or decreased individually.

[0110] In some embodiments, the heating temperature for magnetron sputtering is 0°C to 200°C. When the heating temperature is low, the resulting thin film can be annealed in air after magnetron sputtering to eliminate internal stress and make the film surface smoother. When the heating temperature is high, the method of this application can synchronize the coating process and the annealing process to reduce the process flow. The stable annealing temperature can be 250°C to 300°C.

[0111] This application does not impose any particular limitation on the type of substrate, which can be selected according to actual needs. For example, in some embodiments, the substrate is a transparent electrode, a metal electrode, or a conductive carbon electrode. Optionally, the transparent electrode is an FTO (fluorine-doped tin dioxide, SnO2:F) conductive glass electrode or an ITO (indium-doped tin dioxide, SnO2:In2O3) conductive glass electrode. Optionally, the metal electrode is selected from one or more of gold, silver, aluminum, and copper electrodes.

[0112] In some embodiments, the method for forming a hole transport layer on a substrate surface includes the steps of: providing M targets comprising inorganic hole transport materials, forming a hole transport layer comprising at least N consecutive sublayers on the substrate surface using magnetron sputtering, where 2 ≤ N ≤ M, and at least one of the M targets is a doped target further comprising a doped material; the inorganic hole transport materials of the M targets are of the same type and are all selected from NiO. x The doping material of each doped target is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each doped target is ≤25% based on the mass of each doped target; the resulting hole transport layer has a gradient-varying bandgap, the M targets have gradient-varying bandgap, and the absolute value of the difference between the bandgap of two adjacent targets, |ΔEg(TAG)|, satisfies: 0eV≤|ΔEg(TAG)|≤1.5eV.

[0113] In some embodiments, the method for forming a hole transport layer on a substrate surface includes the steps of: providing M targets comprising inorganic hole transport materials, forming a hole transport layer comprising at least N consecutive sublayers on the substrate surface using magnetron sputtering, where 2 ≤ N ≤ M, and at least one of the M targets is a doped target further comprising a doped material; the inorganic hole transport materials of the M targets are of the same type and are all selected from NiO. x The doping material of each doped target is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each doped target is ≤25% based on the mass of each doped target; the resulting hole transport layer has a gradient-varying conduction band bottom energy level, the M targets have gradient-varying conduction band bottom energy levels, and the absolute value of the difference between the conduction band bottom energy levels of two adjacent targets, |ΔCBM(TAG)|, satisfies: 0eV≤|ΔCBM(TAG)|≤1.5eV.

[0114] In some embodiments, the method for forming a hole transport layer on a substrate surface includes the steps of: providing M targets comprising inorganic hole transport materials, forming a hole transport layer comprising at least N consecutive sublayers on the substrate surface using magnetron sputtering, where 2 ≤ N ≤ M, and at least one of the M targets is a doped target further comprising a doped material; the inorganic hole transport materials of the M targets are of the same type and are all selected from NiO. x The doping material of each doped target is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each doped target is based on the mass of each doped target. The amount is ≤25%; the obtained hole transport layer has a gradient-varying bandgap and conduction band bottom level, the M targets have gradient-varying bandgap and conduction band bottom level, and the absolute value of the difference between the bandgap of two adjacent targets, |ΔEg(TAG)|, satisfies: 0eV≤|ΔEg(TAG)|≤1.5eV, and the absolute value of the difference between the conduction band bottom level of two adjacent targets, |ΔCBM(TAG)|, satisfies: 0eV≤|ΔCBM(TAG)|≤1.5eV.

[0115] Hole transport layer

[0116] A second aspect of this application provides a hole transport layer for a solar cell. The hole transport layer comprises at least N consecutive sublayers, where N ≥ 2, wherein each sublayer comprises an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer further comprising a doping material.

[0117] In some embodiments, N-1 of the N sublayers include doped material, and one sublayer does not include doped material. In other embodiments, all N sublayers include doped material.

[0118] In some embodiments, N is a range consisting of any number of values ​​from 2, 3, 4, 5, 6, 7, 8, 9, 10 or above. Optionally, 2≤N≤10, 3≤N≤10, 4≤N≤10, 5≤N≤10, 2≤N≤9, 2≤N≤8, 2≤N≤7, 2≤N≤6, 2≤N≤5, or 2≤N≤5.

[0119] In some embodiments, the inorganic hole transport materials of each sublayer are of the same type.

[0120] In some embodiments, the inorganic hole transport material may be a p-type semiconductor. As an example, the inorganic hole transport material is selected from nickel oxide (NiO). x The inorganic hole transport material is selected from one of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3. Optionally, the inorganic hole transport material is selected from NiO. x .

[0121] In some embodiments, the inorganic hole transport materials of each sub-doped layer are of the same type, or the doping materials are of the same type or different types.

[0122] For example, in some embodiments, the inorganic hole transport materials of each sub-doped layer are of the same type, and the doping materials are of different types; in other embodiments, the inorganic hole transport materials of each sub-doped layer are of the same type, and the doping materials are not completely the same type, for example, each sub-doped layer has at least one identical doping material and at least one different doping material.

[0123] As an example, the doping material of each sub-doped layer is independently selected from NiO. xOne or more of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3.

[0124] In some embodiments, based on the quality of each sub-doped layer, the total mass percentage of the doped material in each sub-doped layer is ≤25%, for example, ≤24%, ≤23%, ≤22%, ≤21%, ≤20%, ≤19%, ≤18%, ≤17%, ≤16%, ≤15%, ≤14%, ≤13%, ≤12%, ≤11%, ≤10%, ≤9%, ≤8%, ≤7%, ≤6%, or ≤5%. Optionally, the total mass percentage of the doped material in each sub-doped layer is 0.1%–25%, 0.1%–22.5%, 0.1%–20%, 0.1%–17.5%, 0.1%–15%, 0.1%–12.5%, 0.1%–10%, 0.1%–7.5%, or 0.1%–5%.

[0125] NiO x CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3 can be used as inorganic hole transport materials or as dopants for a specific inorganic hole transport material. The difference lies in the following: when used as an inorganic hole transport material, the mass percentage content in each sublayer (or sub-doped layer) is relatively high, for example, greater than 75%, optionally 75% to 100%; while when used as a dopant for a specific inorganic hole transport material, the mass percentage content in each sub-doped layer is relatively low, for example, ≤25%.

[0126] In some embodiments, when the sub-doped layer comprises NiO x When one or more of the following are selected: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, Ag, and Ag2O, the mass percentage of the doped material in the sub-doped layer independently satisfies ≤15%. Among them, NiO... x CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, and Ag2O are dopants used here as inorganic hole transport materials in a sub-doped layer.

[0127] In some embodiments, when the sub-doped layer comprises one or both of MgO and KI, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤20%.

[0128] In some embodiments, when the sub-doped layer includes one or both of MnO and MnO2, the mass percentage of each dopant material in the sub-doped layer independently satisfies ≤10%. Here, MnO and MnO2 are dopant materials that serve as inorganic hole transport materials in the sub-doped layer.

[0129] In some embodiments, when the sub-doped layer includes one or both of Co and CoO, the mass percentage of each dopant material in the sub-doped layer independently satisfies ≤8%. Here, CoO is a dopant material that serves as an inorganic hole transport material in the sub-doped layer.

[0130] In some embodiments, when the sub-doped layer includes one or more of Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, the mass percentage of each dopant material in the sub-doped layer independently satisfies ≤25%. Here, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3 are dopant materials used as inorganic hole transport materials in the sub-doped layer.

[0131] The energy levels of each sublayer (e.g., band gap, conduction band bottom level, etc.) can be obtained by adjusting the type and / or content of the inorganic hole transport material and the type and / or content of the doped material in each sublayer.

[0132] To obtain the desired energy level (e.g., band gap, conduction band bottom level, etc.), the type and content of the doping material for each sub-doped layer can be selected from the above doping materials and their contents as needed. The doping material can be one type or a combination of multiple types.

[0133] In some embodiments, the first sublayer or the Nth sublayer is a sub-doped layer, and the doping material includes at least KI. In this case, the surface defects of the hole transport layer can be reduced to promote the deposition and crystallization of subsequent perovskite materials.

[0134] In some embodiments, the N sublayers have gradient-varying energy levels. For example, the N sublayers satisfy one or more of a gradient-varying bandgap and conduction band bottom energy level. By adjusting the type and / or content of the inorganic hole transport material and the type and / or content of the dopant material in each sublayer, the energy level positions (e.g., bandgap, conduction band bottom energy level, etc.) of each sublayer and the hole transport layer can be adjusted, thereby better achieving energy level matching and optimization between the light-absorbing layer and the hole transport layer.

[0135] For example, in some embodiments, the N sublayers have gradient-increasing or decreasing bandgap widths, and the absolute value of the difference between the bandgap widths of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0 eV < |ΔEg(HTL)| ≤ 1.5 eV. In other embodiments, the N sublayers have gradient-increasing or decreasing conduction band bottom levels, and the absolute value of the difference between the conduction band bottom levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0 eV < |ΔCBM(HTL)| ≤ 1.5 eV. In some other embodiments, the N sublayers have gradient-increasing or decreasing bandgap widths and conduction band bottom levels, and the absolute value of the difference between the bandgap widths of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0eV < |ΔEg(HTL)| ≤ 1.5eV, and the absolute value of the difference between the conduction band bottom levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0eV < |ΔCBM(HTL)| ≤ 1.5eV.

[0136] The hole transport layer of this application has a gently varying energy level gradient, which is beneficial for energy level matching and optimization between the light-absorbing layer and the hole transport layer, and also for improving the performance of the solar cell. The bandgap width and the position of the conduction band bottom energy level of the hole transport layer of this application can be adjusted, thereby improving the hole collection and transport capabilities of the hole transport layer.

[0137] In some embodiments, the total thickness of the hole transport layer is 5 nm to 150 nm. Optionally, the total thickness of the hole transport layer is 10 nm to 80 nm. The thickness of each sublayer may be the same or different.

[0138] The band distribution of each sublayer and the hole transport layer can be obtained by using X-ray photoelectron spectroscopy (XPS) or ultraviolet photoelectron spectroscopy (UPS).

[0139] In some embodiments, the hole transport layer comprises at least N consecutive sublayers, 2 ≤ N ≤ 10, each sublayer comprising an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer further comprising a doped material; the inorganic hole transport materials of the N sublayers are of the same type and are all selected from NiO. xThe doping material of each sub-doped layer is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each sub-doped layer is ≤25% based on the mass of each sub-doped layer; the N sub-layers have a gradient increasing or decreasing band gap, and the absolute value of the difference between the band gaps of two adjacent sub-layers, |ΔEg(HTL)|, satisfies: 0eV < |ΔEg(HTL)| ≤ 1.5eV.

[0140] In some embodiments, the hole transport layer comprises at least N consecutive sublayers, 2 ≤ N ≤ 10, each sublayer comprising an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer further comprising a doped material; the inorganic hole transport materials of the N sublayers are of the same type and are all selected from NiO. x The doping material of each sub-doped layer is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each sub-doped layer is ≤25% based on the mass of each sub-doped layer; the N sub-layers have a gradient increasing or decreasing conduction band bottom energy level, and the absolute value of the difference between the conduction band bottom energy levels of two adjacent sub-layers, |ΔCBM(HTL)|, satisfies: 0eV < |ΔCBM(HTL)| ≤ 1.5eV.

[0141] In some embodiments, the hole transport layer comprises at least N consecutive sublayers, 2 ≤ N ≤ 10, each sublayer comprising an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer further comprising a doped material; the inorganic hole transport materials of the N sublayers are of the same type and are all selected from NiO. xThe doping material of each sub-doped layer is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the doping material of each sub-doped layer is determined based on the quality of each sub-doped layer. The total mass percentage of the doped material is ≤25%; the N sublayers have a gradient increasing or decreasing bandgap and conduction band bottom level, and the absolute value of the difference between the bandgap of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0eV < |ΔEg(HTL)| ≤1.5eV, and the absolute value of the difference between the conduction band bottom levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0eV < |ΔCBM(HTL)| ≤1.5eV.

[0142] Solar cells

[0143] A third aspect of the present application provides a solar cell, which includes a hole transport layer prepared by the method of the first aspect of the present application, or a hole transport layer of the second aspect of the present application.

[0144] The solar cell of this application also includes a front electrode, a back electrode, a light-absorbing layer, and an electron transport layer. The hole transport layer, the light-absorbing layer, and the electron transport layer are located between the front electrode and the back electrode, and the light-absorbing layer is located between the electron transport layer and the hole transport layer.

[0145] The solar cell of the third aspect of the embodiments of this application will now be described with reference to the accompanying drawings.

[0146] Figure 1 This is a schematic diagram of one embodiment of the solar cell of this application. Figure 1 As shown, the solar cell includes a front electrode 10, a hole transport layer 20, a light-absorbing layer 30, an electron transport layer 40, and a back electrode 50 arranged sequentially. Figure 2 This is a schematic diagram of another embodiment of the solar cell of this application, as shown below. Figure 2 As shown, the solar cell includes a front electrode 10, an electron transport layer 40, a light-absorbing layer 30, a hole transport layer 20, and a back electrode 50 arranged sequentially. The hole transport layer 20 includes N consecutive sublayers, where N ≥ 2. Each sublayer includes an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer that also includes a doped material. The first sublayer is positioned away from the light-absorbing layer 30, and the Nth sublayer is positioned close to the light-absorbing layer 30.

[0147] In some embodiments, N-1 of the N sublayers include doped material, and one sublayer does not include doped material. In other embodiments, all N sublayers include doped material.

[0148] In some embodiments, N is a range consisting of any number of values ​​from 2, 3, 4, 5, 6, 7, 8, 9, 10 or above. Optionally, 2≤N≤10, 3≤N≤10, 4≤N≤10, 5≤N≤10, 2≤N≤9, 2≤N≤8, 2≤N≤7, 2≤N≤6, 2≤N≤5, or 2≤N≤5.

[0149] In some embodiments, the inorganic hole transport materials of each sublayer are of the same type.

[0150] In some embodiments, the inorganic hole transport material may be a p-type semiconductor. As an example, the inorganic hole transport material is selected from nickel oxide (NiO). x The inorganic hole transport material is selected from one of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3. Optionally, the inorganic hole transport material is selected from NiO. x .

[0151] In some embodiments, the inorganic hole transport materials of each sub-doped layer are of the same type, or the doping materials are of the same type or different types.

[0152] For example, in some embodiments, the inorganic hole transport materials of each sub-doped layer are of the same type, and the doping materials are of different types; in other embodiments, the inorganic hole transport materials of each sub-doped layer are of the same type, and the doping materials are not completely the same type, for example, each sub-doped layer has at least one identical doping material and at least one different doping material.

[0153] As an example, the doping material of each sub-doped layer is independently selected from NiO. x One or more of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3.

[0154] In some embodiments, based on the quality of each sub-doped layer, the total mass percentage of the doped material in each sub-doped layer is ≤25%, for example, ≤24%, ≤23%, ≤22%, ≤21%, ≤20%, ≤19%, ≤18%, ≤17%, ≤16%, ≤15%, ≤14%, ≤13%, ≤12%, ≤11%, ≤10%, ≤9%, ≤8%, ≤7%, ≤6%, or ≤5%. Optionally, the total mass percentage of the doped material in each sub-doped layer is 0.1%–25%, 0.1%–22.5%, 0.1%–20%, 0.1%–17.5%, 0.1%–15%, 0.1%–12.5%, 0.1%–10%, 0.1%–7.5%, or 0.1%–5%.

[0155] NiO x CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3 can be used as inorganic hole transport materials or as dopants for a specific inorganic hole transport material. The difference lies in the following: when used as an inorganic hole transport material, the mass percentage content in each sublayer (or sub-doped layer) is relatively high, for example, greater than 75%, optionally 75% to 100%; while when used as a dopant for a specific inorganic hole transport material, the mass percentage content in each sub-doped layer is relatively low, for example, ≤25%.

[0156] In some embodiments, when the sub-doped layer comprises NiO x When one or more of the following are selected: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, Ag, and Ag2O, the mass percentage of the doped material in the sub-doped layer independently satisfies ≤15%. Among them, NiO... x CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, and Ag2O are dopants used here as inorganic hole transport materials in a sub-doped layer.

[0157] In some embodiments, when the sub-doped layer comprises one or both of MgO and KI, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤20%.

[0158] In some embodiments, when the sub-doped layer includes one or both of MnO and MnO2, the mass percentage of each dopant material in the sub-doped layer independently satisfies ≤10%. Here, MnO and MnO2 are dopant materials that serve as inorganic hole transport materials in the sub-doped layer.

[0159] In some embodiments, when the sub-doped layer includes one or both of Co and CoO, the mass percentage of each dopant material in the sub-doped layer independently satisfies ≤8%. Here, CoO is a dopant material that serves as an inorganic hole transport material in the sub-doped layer.

[0160] In some embodiments, when the sub-doped layer includes one or more of Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, the mass percentage of each dopant material in the sub-doped layer independently satisfies ≤25%. Here, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3 are dopant materials used as inorganic hole transport materials in the sub-doped layer.

[0161] The energy levels of each sublayer (e.g., band gap, conduction band bottom level, etc.) can be obtained by adjusting the type and / or content of the inorganic hole transport material and the type and / or content of the doped material in each sublayer.

[0162] To obtain the desired energy level (e.g., band gap, conduction band bottom level, etc.), the type and content of the doping material for each sub-doped layer can be selected from the above doping materials and their contents as needed. The doping material can be one type or a combination of multiple types.

[0163] In some embodiments, the Nth sublayer is a sub-doped layer, and the doping material includes at least KI, which can reduce surface defects in the hole transport layer to promote the deposition and crystallization of subsequent perovskite materials.

[0164] In some embodiments, the N sublayers have gradient-varying energy levels. For example, the N sublayers satisfy one or more of a gradient-varying bandgap and conduction band bottom energy level. By adjusting the type and / or content of the inorganic hole transport material and the type and / or content of the dopant material in each sublayer, the energy level positions (e.g., bandgap, conduction band bottom energy level, etc.) of each sublayer and the hole transport layer can be adjusted, thereby better achieving energy level matching and optimization between the light-absorbing layer and the hole transport layer.

[0165] In some embodiments, along the direction from the Nth sublayer to the 1st sublayer, the N sublayers have a gradient-increasing bandgap width, and the absolute value of the difference between the bandgap widths of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0 eV < |ΔEg(HTL)| ≤ 1.5 eV. In other embodiments, along the direction from the Nth sublayer to the 1st sublayer, the N sublayers have a gradient-increasing conduction band bottom level, and the absolute value of the difference between the conduction band bottom levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0 eV < |ΔCBM(HTL)| ≤ 1.5 eV. In some other embodiments, along the direction from the Nth sublayer to the 1st sublayer, the N sublayers have gradient-increasing bandgap widths and conduction band bottom levels, and the absolute value of the difference between the bandgap widths of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0eV < |ΔEg(HTL)| ≤ 1.5eV, and the absolute value of the difference between the conduction band bottom levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0eV < |ΔCBM(HTL)| ≤ 1.5eV.

[0166] Specifically, the conduction band bottom level of the first sublayer is CBM1, the valence band top level is VBM1, and the band gap ΔEg1 = CBM1 - VBM1; the conduction band bottom level of the second sublayer is CBM2, the valence band top level is VBM2, and the band gap ΔEg2 = CBM2 - VBM2; ..., the conduction band bottom level of the Nth sublayer is CBM1. n The top energy level of the valence band is VBM. n Bandwidth ΔEg n =CBM n -VBM n .

[0167] In some embodiments, ΔEg1, ΔEg2, ..., ΔEg n Decreasing sequentially, and 0eV < ΔEg i -ΔEg i+1 ≤1.5eV, 1≤i≤N-1. In other embodiments, CBM1, CBM2, ..., CBM n Decreasing sequentially, and 0eV < CBM i -CBM i+1 ≤1.5eV, 1≤i≤N-1. In some other embodiments, ΔEg1, ΔEg2, ..., ΔEg n Decreasing sequentially: CBM1, CBM2, ..., CBM n Decreasing sequentially, and 0eV < ΔEg i -ΔEg i+1 ≤1.5eV, 0eV<CBM i -CBM i+1 ≤1.5eV, 1≤i≤N-1.

[0168] The solar cell of this application includes a hole transport layer with a gently varying energy level gradient, which facilitates energy level matching and optimization between the light-absorbing layer and the hole transport layer, thereby improving the performance of the solar cell. The bandgap width and conduction band bottom level of the hole transport layer can be adjusted, further enhancing its hole collection and transport capabilities.

[0169] In some embodiments, the total thickness of the hole transport layer 20 is 5 nm to 150 nm. Optionally, the total thickness of the hole transport layer 20 is 10 nm to 80 nm. The thicknesses of the sublayers in the hole transport layer 20 may be the same or different.

[0170] In some embodiments, the light-absorbing layer 30 comprises a perovskite material. As an intrinsic semiconductor material, the perovskite material can transport both electrons and holes; therefore, it can function as a light-absorbing layer, an electron transport layer, or a hole transport layer in a solar cell. The type of perovskite material is not specifically limited and can be selected according to actual needs. In some embodiments, the perovskite material may include one or more of inorganic halide perovskite materials, organic halide perovskite materials, and organic-inorganic hybrid halide perovskite materials. The molecular formula of the perovskite material may be ABX3, where A represents an inorganic cation, an organic cation, or a mixed organic-inorganic cation; B represents an inorganic cation, an organic cation, or a mixed organic-inorganic cation; and X represents an inorganic anion, an organic anion, or a mixed organic-inorganic anion.

[0171] As an example, A is selected from CH3NH3 + (MA + CH(NH2)2 + (FA + ), Li + Na + K + 、Rb + Cs + One or more of them. Optionally, A is selected from CH3NH3. + CH(NH2)2 + Cs + One or more of them,

[0172] As an example, B is selected from Pb. 2+ Sn 2+ Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Zn 2+ 、Ge 2+ Fe 2+Co 2+ Ni 2+ One or more of them. Optionally, B is selected from Pb. 2+ Sn 2+ One or two of them,

[0173] As an example, X is selected from F - Cl - ,Br - I - One or more of them. Optionally, X is selected from Cl. - ,Br - I - One or more of them.

[0174] In some embodiments, the perovskite material includes, but is not limited to, one or more of CH3NH3PbI3 (MAPbI3), CH(NH2)2PbI3 (FAPbI3), CsPbI3, CsPbI2Br, and CsPbIBr2.

[0175] In some embodiments, the thickness of the light-absorbing layer 30 is not specifically limited and can be selected according to actual needs. For example, the thickness of the light-absorbing layer 30 is 150 nm to 1000 nm. Optionally, the thickness of the light-absorbing layer 30 is 300 nm to 700 nm.

[0176] In some embodiments, the electron transport layer 40 includes an electron transport material. The electron transport material of the electron transport layer 40 is not specifically limited and can be selected according to actual needs. For example, the electron transport material is selected from organic electron transport materials, inorganic electron transport materials, or organic-inorganic hybrid electron transport materials.

[0177] As an example, the electron transport material is selected from at least one of the following materials: imide compounds, quinone compounds, fullerenes and their derivatives, 2,2',7,7'-tetra(N,N-p-methoxyaniline)-9,9'-spirodifluorene (Spiro-OMeTAD), methoxytriphenylamine-fluoroformamidinium (OMeTPA-FA), poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS), poly3-hexylthiophene (P3HT), triphenylamine with a triphenylene core (H101), 3,4-ethylenedioxythiophene-methoxy Triphenylamine (EDOT-OMeTPA), N-(4-aniline)carbazole-spirobisfluorene (CzPAF-SBF), polythiophene, metal oxides (metal elements selected from Mg, Ni, Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, or Cr), silicon dioxide (SiO2), strontium titanate (SrTiO3), calcium titanate (CaTiO3), lithium fluoride (LiF), calcium fluoride (CaF2), and cuprous thiocyanate (CuSCN).

[0178] Optionally, the electron transport material is selected from one or more of fullerenes and their derivatives. For example, the electron transport material is selected from PC. 60 BM, PC 70 One or more of the BM. The energy levels of fullerenes and their derivatives can be better matched with the energy levels of the light-absorbing layer, which is beneficial for promoting electron extraction and transport.

[0179] In some embodiments, the thickness of the electron transport layer 40 is not specifically limited and can be selected according to actual needs. For example, the thickness of the electron transport layer 40 is 20 nm to 200 nm.

[0180] In some embodiments, at least one of the front electrode 10 and the back electrode 50 is a transparent electrode. As an example, the transparent electrode is an FTO (fluorine-doped tin dioxide, SnO2:F) conductive glass electrode or an ITO (indium-doped tin dioxide, SnO2:In2O3) conductive glass electrode.

[0181] In some embodiments, one of the front electrode 10 and the back electrode 50 is a metal electrode or a conductive carbon electrode. As an example, the metal electrode is selected from one or more of gold, silver, aluminum, and copper electrodes.

[0182] In some embodiments, the thickness of the front electrode 10 is not specifically limited and can be selected according to actual needs. For example, the thickness of the front electrode 10 is 10 nm to 650 nm.

[0183] In some embodiments, the thickness of the back electrode 10 is not specifically limited and can be selected according to actual needs. For example, the thickness of the back electrode 10 is 10 nm to 650 nm.

[0184] The solar cell of this application is not limited to the structure described above, and may also include other functional layers. For example, in some embodiments, the solar cell further includes a hole-blocking layer located between the light-absorbing layer 30 and the electron transport layer 40. In other embodiments, the solar cell further includes an electrode modification layer for modifying the front electrode 10 or the back electrode 50. The electrode modification layer can reduce the energy level barrier between the light-absorbing layer 30 and the front electrode 10 or the back electrode 50, thereby playing the role of transporting holes while blocking electrons or transporting electrons while blocking holes.

[0185] The band distribution of each film layer can be obtained by using X-ray photoelectron spectroscopy (XPS) or ultraviolet photoelectron spectroscopy (UPS).

[0186] In some embodiments, a solar cell includes a front electrode, a back electrode, a hole transport layer, a light-absorbing layer, and an electron transport layer. The hole transport layer, light-absorbing layer, and electron transport layer are located between the front electrode and the back electrode. The light-absorbing layer is located between the electron transport layer and the hole transport layer. The hole transport layer includes N consecutive sublayers, where 2 ≤ N ≤ 10. Each sublayer includes an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer that also includes a doped material. The inorganic hole transport materials in the N sublayers are of the same type and are all selected from NiO. x The doping material of each sub-doped layer is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each sub-doped layer is ≤25% based on the mass of each sub-doped layer; the first sub-layer is disposed away from the light-absorbing layer, and the Nth sub-layer is disposed close to the light-absorbing layer. Along the direction from the Nth sub-layer to the first sub-layer, the N sub-layers have a gradient increasing band gap, and the absolute value of the difference between the band gaps of two adjacent sub-layers, |ΔEg(HTL)|, satisfies: 0eV < |ΔEg(HTL)| ≤ 1.5eV.

[0187] In some embodiments, a solar cell includes a front electrode, a back electrode, a hole transport layer, a light-absorbing layer, and an electron transport layer. The hole transport layer, light-absorbing layer, and electron transport layer are located between the front electrode and the back electrode. The light-absorbing layer is located between the electron transport layer and the hole transport layer. The hole transport layer includes N consecutive sublayers, where 2 ≤ N ≤ 10. Each sublayer includes an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer that also includes a doped material. The inorganic hole transport materials in the N sublayers are of the same type and are all selected from NiO. x The doping material of each sub-doped layer is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each sub-doped layer is ≤25% based on the mass of each sub-doped layer; the first sub-layer is disposed away from the light-absorbing layer, and the Nth sub-layer is disposed close to the light-absorbing layer. Along the direction from the Nth sub-layer to the first sub-layer, the N sub-layers have a gradient increasing conduction band bottom energy level, and the absolute value of the difference between the conduction band bottom energy levels of two adjacent sub-layers, |ΔCBM(HTL)|, satisfies: 0eV<|ΔCBM(HTL)|≤1.5eV.

[0188] In some embodiments, a solar cell includes a front electrode, a back electrode, a hole transport layer, a light-absorbing layer, and an electron transport layer. The hole transport layer, light-absorbing layer, and electron transport layer are located between the front electrode and the back electrode. The light-absorbing layer is located between the electron transport layer and the hole transport layer. The hole transport layer includes N consecutive sublayers, where 2 ≤ N ≤ 10. Each sublayer includes an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer that also includes a doped material. The inorganic hole transport materials in the N sublayers are of the same type and are all selected from NiO. xThe doping material of each sub-doped layer is independently selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, and the total mass percentage of the doping material of each sub-doped layer is ≤25% based on the mass of each sub-doped layer; the first The Nth sublayer is disposed away from the light-absorbing layer, and the Nth sublayer is disposed close to the light-absorbing layer. Along the direction from the Nth sublayer to the 1st sublayer, the N sublayers have a gradient increasing bandgap and conduction band bottom level. The absolute value of the difference between the bandgap of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0eV<|ΔEg(HTL)|≤1.5eV, and the absolute value of the difference between the conduction band bottom levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0eV<|ΔCBM(HTL)|≤1.5eV.

[0189] Methods for preparing solar cells

[0190] A fourth aspect of the present application provides a method for preparing a solar cell, which includes at least the step of forming a hole transport layer on the surface of a substrate according to the first aspect of the present application.

[0191] The method for fabricating a solar cell according to this application further includes the steps of: fabricating a front electrode; fabricating a light-absorbing layer; fabricating an electron transport layer; and fabricating a back electrode. The methods for forming the above-mentioned films are not specifically limited and can employ film-forming methods known in the art. For example, the above-mentioned films can be grown using any solution method, vacuum evaporation method, chemical vapor deposition method, sputtering method, etc.

[0192] In some embodiments, the method for preparing a solar cell according to this application includes the steps of: preparing a front electrode, forming a hole transport layer on the front electrode according to the method of the first aspect of the embodiments of this application, forming a light-absorbing layer on the hole transport layer, forming an electron transport layer on the light-absorbing layer, and forming a back electrode on the electron transport layer.

[0193] In some embodiments, the method for preparing a solar cell according to this application includes the steps of: preparing a front electrode, forming an electron transport layer on the front electrode, forming a light-absorbing layer on the electron transport layer, forming a hole transport layer on the light-absorbing layer according to the method of the first aspect of the present application, and forming a back electrode on the hole transport layer.

[0194] The band distribution of each film layer can be obtained by using X-ray photoelectron spectroscopy (XPS) or ultraviolet photoelectron spectroscopy (UPS).

[0195] photovoltaic modules

[0196] A fifth aspect of the embodiments of this application provides a photovoltaic module, the photovoltaic module including a solar cell according to a third aspect of the embodiments of this application, the solar cell being usable as a power source for the photovoltaic module.

[0197] Example

[0198] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0199] Example 1

[0200] Preparation of ITO conductive glass electrode

[0201] Take an ITO conductive glass with dimensions of 2.0cm × 2.0cm, clean the surface of the ITO conductive glass twice with acetone and isopropanol respectively, then immerse it in deionized water for ultrasonic treatment for 10 minutes and then dry it in a forced-air drying oven.

[0202] Preparation of hole transport layer

[0203] Prepare four targets as shown in Table 1, numbered 1#, 2#, 3#, 4#, ..., and install and fix the four targets sequentially on the cathode of the magnetron sputtering chamber. Set the magnetron sputtering conditions for each target according to Table 2. Place the ITO conductive glass obtained above on the anode of the magnetron sputtering chamber as a substrate, and the substrate advances at a speed of 4.5 mm / s.

[0204] During magnetron sputtering, when the ITO conductive glass propels forward and passes over target #1, a sublayer #1 with the same composition as target #1 will be formed on the surface of the ITO conductive glass. As the ITO conductive glass propels forward, a sublayer #2 with the same composition as target #2 will be formed on the basis of sublayer #1, and so on.

[0205] After magnetron sputtering, a hole transport layer with four sublayers was obtained on the surface of the ITO conductive glass electrode, with a total thickness of 25 nm. The band distribution of each sublayer of the hole transport layer was measured at room temperature and pressure using an Escalab 250Xi (from Thermo Scientific), and the results are shown in Table 3.

[0206] Table 1

[0207]

[0208] Table 2

[0209]

[0210] Table 3

[0211]

[0212] Preparation of light-absorbing layer

[0213] A 1 mol / L MAPbI3 dimethylformamide solution was spin-coated onto the obtained hole transport layer at a speed of 3000 rpm to 4500 rpm. The layer was then transferred to a constant temperature hot plate and heated at 100 °C for 30 min. After cooling to room temperature, a light-absorbing layer with a thickness of 500 nm was formed.

[0214] Fabrication of electron transport layer

[0215] PC with a concentration of 20 mg / L was spin-coated onto the obtained light-absorbing layer at a speed of 800 rpm to 1500 rpm. 60 The BM chlorobenzene solution was then transferred to a constant temperature hot plate and heated at 150°C for 15 minutes. After cooling to room temperature, an electron transport layer with a thickness of 70 nm was formed.

[0216] Preparation of Ag electrode

[0217] The aforementioned sample was placed in a vacuum coating machine and subjected to a 5×10⁻⁶ temperature. -4 Ag electrodes with a thickness of 80 nm were deposited on the surface of the obtained electron transport layer under vacuum conditions of Pa.

[0218] The final solar cell structure obtained in Example 1 is ITO / doped NiO. x / MAPbI3 / PC 60 A schematic diagram of the energy level distribution of the BM / Ag solar cell prepared in Example 1 is shown below. Figure 3 As shown.

[0219] The solar cells obtained by the method of this application have better stability and consistency, and the energy level structure of the hole transport layer in the solar cell can be easily adjusted by adjusting the specific composition of the target material or by replacing the target material, which is beneficial to the energy level matching and optimization between the light-absorbing layer and the hole transport layer.

[0220] Table 4 presents the test results of short-circuit voltage Voc, short-circuit current density Jsc, fill factor, and energy conversion efficiency of the solar cell prepared in Example 1.

[0221] Table 4

[0222] Voc(V) <![CDATA[Jsc(mA / cm 2 )]]> Fill Factor (%) Efficiency (%) Example 1 1.07 20.8 65.0 14.3

[0223] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for forming a hole transport layer on a substrate surface, comprising the steps of: M targets comprising inorganic hole transport materials are provided, and a hole transport layer comprising at least N consecutive sublayers is formed on the substrate surface using the principle of magnetron sputtering, where 2≤N≤M, and at least one of the M targets is a doped target that also includes doped materials. The hole transport layer has gradient-varying energy levels; The hole transport layer has a gradient-varying bandgap, the M targets have gradient-varying bandgap, and the absolute value of the difference between the bandgap of two adjacent targets, |ΔEg(TAG)|, satisfies: 0eV≤|ΔEg(TAG)|≤1.5eV; The hole transport layer has a gradient-varying conduction band bottom energy level, the M targets have gradient-varying conduction band bottom energy levels, and the absolute value of the difference between the conduction band bottom energy levels of two adjacent targets, |ΔCBM(TAG)|, satisfies: 0eV≤|ΔCBM(TAG)|≤1.5eV.

2. The method according to claim 1, wherein, The inorganic hole transport materials of each target are of the same type.

3. The method according to claim 1 or 2, wherein, The inorganic hole transport material is a P-type semiconductor.

4. The method according to claim 1 or 2, wherein, The inorganic hole transport material is selected from NiO. x One of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3.

5. The method according to claim 1 or 2, wherein, The inorganic hole transport material is selected from NiO. x .

6. The method according to claim 1 or 2, wherein, The types of doped materials in each of the doped targets may be the same or different from each other.

7. The method according to claim 1 or 2, wherein, The doping material of each doped target is independently selected from NiO. x One or more of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3.

8. The method according to claim 6, wherein, The first target or the Mth target is a doped target, and the doped material includes at least KI.

9. The method according to claim 1 or 2, wherein, Based on the mass of each doped target, the total mass percentage of the doped material in each doped target is ≤25%.

10. The method according to claim 1 or 2, wherein, Based on the mass of each doped target, the total mass percentage of the doped material in each doped target is 0.1% to 25%.

11. The method according to claim 9, wherein, When the doped target includes NiO x When the dopant is selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, Ag, and Ag2O, the mass percentage of the dopant material in the doped target independently satisfies ≤15%; When the doped target includes one or both of MgO and KI, the mass percentage of the dopant material in the doped target independently satisfies ≤20%; When the doped target includes one or both of MnO and MnO2, the mass percentage of the dopant material in the doped target independently satisfies ≤10%; When the doped target includes one or both of Co and CoO, the mass percentage of the dopant material in the doped target independently satisfies ≤8%; When the doped target includes one or more of Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, the mass percentage of the doped material in the doped target independently satisfies ≤25%.

12. The method according to claim 1 or 2, wherein, The substrate is a transparent electrode, a metal electrode, or a conductive carbon electrode.

13. The method according to claim 12, wherein, The transparent electrode is an FTO conductive glass electrode or an ITO conductive glass electrode.

14. The method according to claim 12, wherein, The metal electrode is selected from one or more of the following: gold electrode, silver electrode, aluminum electrode, and copper electrode.

15. The method according to claim 1 or 2, wherein, The magnetron sputtering satisfies: The sputtering pressure is 2×10 -3 mbar~8×10 -3 mbar; and / or, Gas flow rate of 50 sccm to 250 sccm; and / or, The heating temperature is 0℃~200℃; and / or, Sputtering power is 200W~13KW; and / or, The target-substrate spacing is 60mm~120mm.

16. A hole transport layer for a solar cell, comprising at least N consecutive sublayers, where N ≥ 2, wherein, Each sublayer includes an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer that also includes a doped material; The N sublayers have bandgap widths that increase or decrease with gradients, and the absolute value of the difference between the bandgap widths of two adjacent sublayers, |ΔEg(HTL)|, satisfies: 0eV<|ΔEg(HTL)|≤1.5eV; The N sublayers have conduction band bottom energy levels with increasing or decreasing gradients, and the absolute value of the difference between the conduction band bottom energy levels of two adjacent sublayers, |ΔCBM(HTL)|, satisfies: 0eV<|ΔCBM(HTL)|≤1.5eV.

17. The hole transport layer according to claim 16, comprising at least N consecutive sublayers, 2 ≤ N ≤ 10, wherein, Each sublayer includes an inorganic hole transport material, and at least one of the N sublayers is a sub-doped layer that also includes a doped material.

18. The hole transport layer according to claim 16 or 17, wherein, The inorganic hole transport materials in each of the sublayers are of the same type.

19. The hole transport layer according to claim 16 or 17, wherein, The inorganic hole transport material is a P-type semiconductor.

20. The hole transport layer according to claim 16 or 17, wherein, The inorganic hole transport material is selected from NiO. x One of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, CoO, Cr2O3, SnO, SnS, Hg2O, PbO, Ag2O, MnO, MnO2, and Pr2O3.

21. The hole transport layer according to claim 16 or 17, wherein, The inorganic hole transport material is selected from NiO. x .

22. The hole transport layer according to claim 16 or 17, wherein, The types of doped materials in each of the sub-doped layers may be the same or different from each other.

23. The hole transport layer according to claim 16 or 17, wherein, The doping material of each sub-doped layer is independently selected from NiO. x One or more of the following: CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, MgO, MnO, MnO2, Ag, Ag2O, Co, CoO, KI, Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3.

24. The hole transport layer according to claim 22, wherein, The first or Nth sublayer is a sub-doped layer, and the doping material includes at least KI.

25. The hole transport layer according to claim 16 or 17, wherein, Based on the quality of each sub-doped layer, the total mass percentage of the doped material in each sub-doped layer is ≤25%.

26. The hole transport layer according to claim 16 or 17, wherein, Based on the quality of each sub-doped layer, the total mass percentage of the doped material in each sub-doped layer is 0.1% to 25%.

27. The hole transport layer according to claim 25, wherein, When the sub-doped layer includes NiO x When the dopant is selected from one or more of CuO, Cu2O, Cu2S, CuI, CuSCN, CuGaO2, Ag, and Ag2O, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤15%; When the sub-doped layer includes one or both of MgO and KI, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤20%; When the sub-doped layer includes one or both of MnO and MnO2, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤10%; When the sub-doped layer includes one or both of Co and CoO, the mass percentage of the dopant material in the sub-doped layer independently satisfies ≤8%; When the sub-doped layer includes one or more of Li, Cs, Pb, In, Ga, Hg, Hg2O, Cr2O3, SnO, SnS, PbO, and Pr2O3, the mass percentage of the doping material in the sub-doped layer independently satisfies ≤25%.

28. The hole transport layer according to claim 16 or 17, wherein, The total thickness of the hole transport layer is 5nm~150nm.

29. The hole transport layer according to claim 16 or 17, wherein, The total thickness of the hole transport layer is 10nm~80nm.

30. A solar cell comprising a hole transport layer prepared by the method according to any one of claims 1-15, or a hole transport layer according to any one of claims 16-29.

31. A method for fabricating a solar cell, comprising a method for forming a hole transport layer on a substrate surface according to any one of claims 1-15.

32. A photovoltaic module comprising the solar cell according to claim 30.

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