Composite hole transport layer, method for preparing the same, and stacked solar cell

Abstract

The present application relates to the field of solar cells, and particularly relates to a composite hole transport layer, a preparation method thereof and a laminated solar cell. The composite hole transport layer comprises a conductive layer and a passivation layer arranged in layers. The conductive layer is made of nickel oxide, formed on the surface of the tunneling layer away from the bottom cell, and the value of Ni 3+ / Ni 2+ is any value in the range of 3.0-3.4, for example, any value in the range of 3.0, 3.1, 3.2, 3.3 and 3.4. The passivation layer is made of metal oxide, with a band gap greater than 5eV, formed on the surface of the conductive layer away from the bottom cell, and the surface thereof away from the conductive layer is used to form a perovskite light-absorbing layer. The passivation layer isolates the conductive layer and the perovskite, which helps to protect the perovskite and improve the stability of the cell, and by constraining the value of Ni 3+ / Ni 2+ , the electrical characteristics of the cell can be optimized.

Description

Technical Field

[0001] This invention relates to the field of solar cells, and particularly to a composite hole transport layer, its preparation method, and a tandem solar cell. Background Technology

[0002] Solar cells are photovoltaic semiconductor devices that directly convert sunlight into electrical energy. They are widely used in the clean energy field and help reduce energy costs. However, current solar cells have relatively low power output, making it difficult to power high-power devices independently, thus hindering their widespread application.

[0003] To promote the application of solar power generation in various fields, improving the power output of solar cells is imperative. Currently, the tandem method is commonly used to increase cell power. In tandem solar cells, the wide-bandgap perovskite top cell is integrated onto the narrow-bandgap bottom cell through an intermediate composite layer. The multi-layer PN junction structure absorbs photons of different wavelengths in the solar spectrum, thereby breaking through the conversion efficiency limit of single-junction cells and increasing output power. The hole transport layer of the top cell in a tandem solar cell is used to extract and transport holes and block electrons, playing a crucial role in the efficiency and stability of the tandem solar cell. However, existing hole transport layers often use nickel oxide, whose surface typically contains numerous dangling bonds and defect states. These active sites react with the perovskite on the surface, inducing perovskite decomposition and generating deep-level defects, severely limiting the efficiency and long-term stability of tandem devices. Summary of the Invention

[0004] The purpose of this invention is to provide a composite hole transport layer that is not prone to interfacial reaction with perovskite, its preparation method, and a tandem solar cell.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A composite hole transport layer, comprising: A conductive layer, made of nickel oxide, is formed on the surface of the tunneling layer away from the bottom cell, and the conductive layer is located on the surface of the tunneling layer away from the Ni. 3+ / Ni 2+ The value can be any value between 3.0 and 3.4; A passivation layer, constructed of metal oxide with a band gap greater than 5 eV, is formed on the surface of the conductive layer away from the bottom cell, and the surface of the passivation layer away from the conductive layer is used to form a perovskite light-absorbing layer.

[0006] The present invention also provides a method for preparing a composite hole transport layer, wherein the maximum temperature during the preparation of the conductive layer and the passivation layer is less than or equal to 200°C.

[0007] Optionally, the composite hole transport layer is prepared by means of: Obtain the bottom battery on which the tunneling layer is formed on the surface; A nickel oxide thin film is formed on the surface of the tunneling layer by magnetron sputtering, with the substrate temperature set to any value between 150°C and 180°C and the power set to any value between 150W and 200W. The conductive layer is formed by treating the surface of the nickel oxide film with hydrogen plasma, wherein the ionization power of the hydrogen plasma is any value between 40W and 110W, and the treatment time is any value between 0.1s and 0.8s. The passivation layer is prepared on the surface of the conductive layer after hydrogen plasma treatment by magnetron sputtering or atomic layering.

[0008] Optionally, the passivation layer is made of any one of aluminum oxide, zirconium oxide, and hafnium oxide, and the thickness of the passivation layer is any value from 0.1 nm to 5 nm.

[0009] Optionally, when preparing the passivation layer by magnetron sputtering, the power is any value between 90W and 120W, the sputtering time is any value between 4s and 6s, and the substrate temperature is any value between 150℃ and 180℃; when preparing the passivation layer by atomic layering, the number of cycles is any value between 2 and 10, and the reaction temperature is any value between 150℃ and 180℃.

[0010] Optionally, the thickness of the conductive layer is any value from 5 nm to 40 nm.

[0011] Optionally, the hydrogen plasma is formed by magnetron sputtering or atomic layer deposition.

[0012] The present invention also provides a tandem solar cell, including the aforementioned composite hole transport layer.

[0013] Optionally, the tandem solar cell includes a bottom cell, a top cell, and a tunneling layer connecting the bottom cell and the top cell. The top cell includes a transparent electrode, an electron transport layer, a perovskite light-absorbing layer, and a composite hole transport layer stacked sequentially. The perovskite light-absorbing layer is made of Cs. a MA b FA （1-a-b） PbI c Br （3-c） , where 0≤a≤1, 0≤b≤1, 0≤c≤3, the composite hole transport layer is attached to the tunneling layer, and the bottom cell is attached to the surface of the tunneling layer away from the top cell. The bottom cell includes a narrowband light-absorbing layer, a composite suppression layer formed on opposite sides of the narrowband light-absorbing layer, a front emitter formed on the surface of the composite suppression layer near the top cell, a back surface field formed on the surface of the composite suppression layer away from the top cell, and a bottom electrode formed on the surface of the back surface field.

[0014] Optionally, a is 0.05, b is 0.15, and c is 2.25.

[0015] According to a first aspect of the present invention, nickel oxide is chemically and physically stable and inexpensive when used for hole transport. Nickel oxide films with high work function, conductivity, and transmittance can be easily obtained by magnetron sputtering, making nickel oxide a superior material for constructing hole transport layers. However, the surface of the nickel oxide film obtained by magnetron sputtering contains numerous dangling bonds and defect states. These active sites can react with the perovskite light-absorbing layer on its surface, inducing perovskite decomposition and generating deep-level defects, which is detrimental to the efficiency and long-term stability of tandem solar cells. Placing a passivation layer between the conductive layer and the perovskite light-absorbing layer helps suppress the interfacial reaction between them, thus improving the performance and lifetime of the tandem solar cell. The Ni on the surface of the conductive layer adjacent to the passivation layer... 3+ When the content is too high, the strong oxidizing Ni 3+ It can steal electrons from halide ions, oxidizing them into elemental halogens, leaving vacancy defects in the perovskite lattice, thereby accelerating the degradation of perovskite materials. 3+ Reduced to Ni 2+ This will significantly reduce the conductivity of the conductive layer, hindering hole transport. Ni at the interface 3+ / Ni 2+ The value directly affects the Fermi level of nickel oxide, Ni 3+ / Ni 2+ A suitable value ensures the valence band position is within the optimal matching range of the perovskite absorber layer. This prevents hole injection barriers caused by energy level shifts, reduces the resistance to photogenerated holes transferring from the perovskite to the transport layer, suppresses interface charge accumulation, and reduces recombination losses. Excess Ni... 3+ Metal cations readily aggregate at grain boundaries, generating high-density defect states. These defects become nonradiative recombination centers, significantly reducing carrier lifetime and device efficiency, while also causing a marked decrease in steady-state photoluminescence intensity. Therefore, Ni at the interface... 3+ / Ni 2+ The value directly affects the power and stability of tandem solar cells.

[0016] According to a second aspect of the invention, the maximum temperature during the preparation process does not exceed 200°C, which is not only applicable to various types of bottom cells and prevents high-temperature damage to the bottom cells, thereby optimizing the performance of tandem solar cells; it also avoids the high temperatures required in conventional hydrogen atmosphere annealing, reducing energy consumption and production costs.

[0017] Furthermore, by treating the nickel oxide thin film formed by magnetron sputtering with hydrogen plasma (H-plasma), the high-energy hydrogen ions H in the H-plasma... +It has strong reducing properties and will reduce Ni ≥3+ Reduced to Ni 2+ Because of H + The diffusion depth is limited, typically less than 5 nm, so the reduction effect is confined to only a few atomic layers on the outermost surface of nickel oxide, while the bulk material retains its original high Ni content. 3+ / Ni 2+ Proportion and conductivity. By constraining the parameters of the deposited nickel oxide film and H-plasma treatment, it is helpful to constrain the Ni at the interface. 3+ / Ni 2+ The value of H-plasma is used to deposit a metal oxide film on the surface of the conductive layer formed after H-plasma treatment, creating a wide-bandgap passivation layer. This dense passivation layer isolates external water and oxygen, while preventing the oxidation of nickel oxide and the decomposition of perovskite, thus consolidating the reduction effect. The wide-bandgap passivation layer has a deep valence band structure, which can act as an electron blocking layer, forcing holes to transport along the valence band of nickel oxide and reducing interfacial recombination losses. H-plasma can be directly generated through a reaction gas chamber of magnetron sputtering or a plasma source of atomic layer deposition (ALD), without the need for additional equipment, which helps to reduce the difficulty of operation and simplify the reaction steps.

[0018] According to a third aspect of the present invention, by enabling the composite hole transport layer to have a better hole transport effect and protecting the perovskite light-absorbing layer, the tandem solar cell can obtain better electrical performance and better stability.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the stacked solar cell shown in Embodiment 1 of the present invention; Figure 2 This is a flowchart illustrating the fabrication method of the composite hole transport layer shown in Embodiment 1 of the present invention; Figure 3 This is a statistical chart of the power conversion efficiency of each tandem solar cell shown in Embodiment 1 of the present invention; Figure 4 This is a maximum power point tracking curve of a tandem solar cell obtained in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the structure of the stacked solar cell shown in Embodiment 3 of the present invention; Figure 6 This is a schematic diagram of the structure of the stacked solar cell shown in Embodiment 5 of the present invention; Figure 7This is a comparison of the current density-voltage characteristic curves of the tandem solar cell shown in Comparative Example 1 of the present invention and a tandem solar cell obtained in Example 1. Figure 8 This is a comparison chart of the current density-voltage characteristic curves of the tandem solar cells shown in Comparative Example 1 and Comparative Example 2 of this invention.

[0021] Legend: 1-Bottom cell, 11-Narrow band light-absorbing layer, 12-Composite suppression layer, 13-Front emitter, 14-Back surface field, 15-Bottom electrode, 151-Transparent layer, 152-First metal electrode network, 16-Passivation protection layer, 171-Glass substrate, 172-Back contact, 173-Cadmium sulfide thin film, 2-Top cell, 21-Transparent electrode, 22-Electron transport layer, 221-First electron transport layer, 222-Second electron transport layer, 23-Perovskite light-absorbing layer, 24-Composite hole transport layer, 241-Conductive layer, 242-Passivation layer, 25-Second metal electrode network, 26-Antireflection layer, 3-Tunneling layer. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] This invention application protects a composite hole transport layer 24, comprising a conductive layer 241 and a passivation layer 242 stacked together. The conductive layer 241 is made of nickel oxide and is formed on the surface of the tunneling layer 3 away from the bottom cell 1, and the Ni oxide of the conductive layer 241 away from the surface of the tunneling layer 3 is... 3+ / Ni 2+ The value is any value from 3.0 to 3.4, for example, any value from 3.0, 3.1, 3.2, 3.3, and 3.4. The passivation layer 242 is constructed of metal oxide with a band gap greater than 5 eV, for example, any value from 5.5 eV, 5.7 eV, and 6.7 eV, and is formed on the surface of the conductive layer 241 away from the bottom cell 1, and the surface of the conductive layer 241 away from the conductive layer 241 is used to form the perovskite light-absorbing layer 23.

[0027] Nickel oxide is chemically and physically stable and inexpensive for hole transport. It can be easily obtained as a thin film with high work function, conductivity, and transmittance via magnetron sputtering, making it a superior material for constructing hole transport layers. However, the surface of the magnetron sputtered nickel oxide film contains numerous dangling bonds and defect states. These active sites can react with the perovskite light-absorbing layer 23, inducing perovskite decomposition and generating deep-level defects, which is detrimental to the efficiency and long-term stability of tandem solar cells. Placing a passivation layer 242 between the conductive layer 241 and the perovskite light-absorbing layer 23 helps suppress the interfacial reaction between them, thus improving the performance and lifetime of the tandem solar cell. The Ni on the surface of the conductive layer 241 adjacent to the passivation layer 242... 3+ When the content is too high, the strong oxidizing Ni 3+ It can steal electrons from halide ions, oxidizing them into elemental halogens, leaving vacancy defects in the perovskite lattice, thereby accelerating the degradation of perovskite materials. 3+ Reduced to Ni 2+ This will significantly reduce the conductivity of the conductive layer 241, which is detrimental to hole transport. Ni at the interface 3+ / Ni 2+ The value directly affects the Fermi level of nickel oxide, Ni 3+ / Ni 2+ A suitable value ensures the valence band position is within the optimal matching range of the perovskite absorber layer 23. This prevents hole injection barriers caused by energy level shifts, reduces the resistance to the transfer of photogenerated holes from the perovskite to the transport layer, suppresses interface charge accumulation, and reduces recombination losses. Excess Ni 3+Metal cations readily aggregate at grain boundaries, generating high-density defect states. These defects become nonradiative recombination centers, significantly reducing carrier lifetime and device efficiency, while also causing a marked decrease in steady-state photoluminescence intensity. Therefore, Ni at the interface... 3+ / Ni 2+ The value directly affects the power and stability of tandem solar cells.

[0028] In existing technologies, to reduce nickel vacancies and suppress interfacial reactions when nickel oxide is used as a hole transport layer, multifunctional metal doping or surface-coated organic self-assembled monomolecular hole transport layers (SAMs) are commonly employed. However, the doping ratio of multifunctional metal doping requires precise control, and it is difficult to balance energy level matching and conductivity, and its ability to suppress interfacial reactions is weak. SAM molecules have poor thermal stability and are prone to degradation and detachment during long-term device operation. Furthermore, the coverage and orderliness of SAMs are highly dependent on the substrate and process, making it difficult to achieve uniform and dense monomolecular coverage over large areas, leading to performance fluctuations and reliability issues, and resulting in low yields in large-scale production. In this application, surface modification of nickel oxide followed by a passivation layer 242 effectively reduces nickel vacancies and suppresses interfacial reactions. The preparation method is simple, low-cost, and has good process repeatability, providing a new direction for the research of nickel oxide hole transport layers.

[0029] The present invention also provides a method for preparing the composite hole transport layer 24, wherein the maximum temperature during the preparation of the conductive layer 241 and the passivation layer 242 is less than or equal to 200°C.

[0030] Ensuring that the maximum temperature during the fabrication process does not exceed 200°C helps prevent high-temperature damage to the bottom cell 1, thereby optimizing the performance of the tandem solar cell.

[0031] In some embodiments, the composite hole transport layer 24 is fabricated by: S1. Obtain a bottom cell 1 with a tunneling layer 3 formed on its surface.

[0032] S2. A nickel oxide thin film is formed on the surface of the tunneling layer 3 by magnetron sputtering, with the substrate temperature set to any value between 150℃ and 180℃ and the power set to any value between 150W and 200W.

[0033] S3. The surface of the nickel oxide thin film is treated with hydrogen plasma to form a conductive layer 241. The ionization power of the hydrogen plasma is any value between 40W and 110W, and the treatment time is any value between 0.1s and 0.8s.

[0034] S4. Passivation layer 242 is prepared on the surface of tunneling layer 3 after hydrogen plasma treatment by magnetron sputtering or atomic layering.

[0035] When preparing the nickel oxide thin film, the substrate temperature can be set to any value among 150°C, 160°C, 170°C, and 180°C, and the power can be set to any value among 150W, 160W, 170W, 180W, 190W, and 200W. The ionization power corresponding to hydrogen plasma can be set to any value among 40W, 60W, 80W, 100W, and 110W, and the processing time can be set to any value among 0.1s, 0.3s, 0.5s, 0.6s, and 0.8s.

[0036] Treating magnetron sputtered nickel oxide films with hydrogen plasma (H-plasma) utilizes the strong reducing properties of high-energy hydrogen ions (H) in H-plasma to reduce Ni oxide oxide. ≥3+ Reduced to Ni 2+ This reduces the Ni content on the surface of the nickel oxide film. 3+ Content. Due to H + The diffusion depth is limited, typically less than 5 nm, so the reduction effect is confined to only a few atomic layers on the outermost surface of nickel oxide, while the bulk material retains its original high Ni content. 3+ / Ni 2+ Proportion and conductivity. By constraining the parameters of the deposited nickel oxide film and H-plasma treatment, it is helpful to constrain the Ni at the interface. 3+ / Ni 2+ The value of . After H-plasma treatment, a metal oxide film is deposited on the surface of the conductive layer 241 to form a wide-bandgap passivation layer 242. Oxygen atoms in the passivation layer 242 fill the oxygen vacancies on the surface of the conductive layer 241, suppressing Ni. 3+ To Ni 2+ The dense passivation layer 242 effectively isolates the nickel oxide from external water and oxygen, preventing oxidation and decomposition of the perovskite, thus consolidating the reduction effect. The wide-bandgap passivation layer 242, with its deep valence band structure, acts as an electron blocking layer, forcing holes to transport along the valence band of the nickel oxide and reducing interfacial recombination losses. H-plasma can be directly generated via a magnetron sputtering reaction gas chamber or a plasma source for atomic layer deposition (ALD), requiring no additional equipment, which helps reduce operational complexity and simplify reaction steps.

[0037] In some embodiments, the passivation layer 242 is made of any one of aluminum oxide, zirconium oxide, and hafnium oxide, and the thickness of the passivation layer 242 is any value from 0.1 nm to 5 nm, for example, any value from 0.1 nm, 0.5 nm, 1 nm, 2 nm, 3 nm, 4 nm, and 5 nm.

[0038] In some embodiments, when the passivation layer 242 is prepared by magnetron sputtering, the power is any value from 90W to 120W, for example, any value from 90W, 100W, 110W, and 120W; the sputtering time is any value from 4s to 6s, for example, any value from 4s, 5s, and 6s; the substrate temperature is any value from 150℃ to 180℃, for example, any value from 150℃, 160℃, 170℃, and 180℃; when the passivation layer 242 is prepared by atomic layering, the number of cycles is any value from 2 to 10, for example, any value from 2, 4, 6, 8, and 10; and the reaction temperature is any value from 150℃ to 180℃, for example, any value from 150℃, 160℃, 170℃, and 180℃.

[0039] In some embodiments, the thickness of the conductive layer 241 is any value from 5nm to 40nm, for example, any value from 5nm, 10nm, 20nm, 30nm and 40nm.

[0040] In some embodiments, hydrogen plasma is formed using a magnetron sputtering device or an atomic layer deposition system, which helps to reduce operational difficulty and preparation costs.

[0041] The present invention also provides a tandem solar cell, including the aforementioned composite hole transport layer 24.

[0042] By enabling the composite hole transport layer 24 to have a better hole transport effect and protecting the perovskite light-absorbing layer 23, the tandem solar cell can obtain better electrical performance and better stability.

[0043] In some embodiments, the tandem solar cell includes a bottom cell 1, a top cell 2, and a tunneling layer 3 connecting the bottom cell 1 and the top cell 2. The top cell 2 includes a transparent electrode 21, an electron transport layer 22, a perovskite light-absorbing layer 23, and a composite hole transport layer 24, which are stacked sequentially. The perovskite light-absorbing layer 23 is made of Cs. a MA b FA 1-a-b PbI c Br 3-c Where 0≤a≤1, 0≤b≤1, 0≤c≤3, the composite hole transport layer 24 is attached to the tunneling layer 3, and the bottom cell 1 is attached to the surface of the tunneling layer 3 away from the top cell 2. The bottom cell 1 includes a narrow band light-absorbing layer 11, a composite suppression layer 12 formed on the opposite two sides of the narrow band light-absorbing layer 11, a front emitter 13 formed on the surface of the composite suppression layer 12 near the top cell 2, a back surface field 14 formed on the surface of the composite suppression layer 12 away from the top cell 2, and a bottom electrode 15 formed on the surface of the back surface field 14.

[0044] A narrowband light-absorbing layer 11 serves as the main material for the bottom cell 1, providing a site for the generation of photogenerated carriers. A recombination suppression layer 12 is wrapped around the surface of the narrowband light-absorbing layer 11, reducing interface defects and carrier recombination losses, and significantly improving the open-circuit voltage. The ultra-thin recombination suppression layer 12 allows carriers to be transported efficiently through quantum tunneling while blocking the lateral flow of majority carriers. The back surface field 14 and the narrowband light-absorbing layer 11 form a PN junction, generating a built-in electric field to separate photogenerated electron-hole pairs, acting as a hole transport layer to directionally transport holes to the tunneling layer 3 and output them. The front emitter 13 forms a highly doped region on the back of the cell, reflecting minority holes and reducing back surface recombination losses. Working in conjunction with the tunneling layer 3, it rapidly transports electrons to the bottom electrode 15, improving the fill factor FF. The tunneling layer 3 achieves efficient carrier tunneling. Perovskite is used as the light-absorbing material in the top cell 2 to provide photogenerated charge carriers. A composite hole transport layer 24 efficiently extracts holes from the perovskite layer and guides them to the back electrode, while simultaneously blocking electrons from flowing back to the perovskite layer. An electron transport layer 22 efficiently extracts electrons generated by photoexcitation in the perovskite layer and directionally transports them to a transparent electrode 21. The transparent electrode 21 allows visible light to efficiently transmit to the perovskite light-absorbing layer 23, while simultaneously collecting the charge transported by the hole transport layer. Cesium ions are inorganic cations with small ionic radii, which can improve lattice stability and suppress the volatile decomposition of organic cations. Methylamine ions are organic cations that enhance the crystallinity of the perovskite film through hydrogen bonding, but excessive amounts can lead to humidity sensitivity. Formamidinium ions are large-sized organic cations that can reduce the overall band gap of the perovskite material and expand the near-infrared light absorption range, but pure phases are prone to phase transitions. Iodide ions dominate long-wavelength absorption, but excessive amounts can lead to an excessively narrow band gap and reduced open-circuit voltage. Bromine ions are used to optimize spectral matching with silicon-based solar cells and enhance hydrothermal stability. The selection of elements facilitates precise control of the band gap in perovskite materials, improving overall material stability and defect tolerance.

[0045] In some embodiments, a is 0.05, b is 0.15, and c is 2.25. By adjusting the ratio of each ion in the material, it is possible to precisely control the band gap of the perovskite material and optimize its stability and defect tolerance.

[0046] Please refer to the following examples for details.

[0047] Example 1: Please see Figure 1 The tandem solar cell shown in a preferred embodiment of this application includes a bottom cell 1, a top cell 2, and a tunneling layer 3 connecting the bottom cell 1 and the top cell 2.

[0048] The bottom cell 1 includes a narrow band light-absorbing layer 11, a composite suppression layer 12 formed on opposite sides of the narrow band light-absorbing layer 11, a front emitter 13 formed on the surface of the composite suppression layer 12 near the top cell 2, a back surface field 14 formed on the surface of the composite suppression layer 12 away from the top cell 2, and a bottom electrode 15 formed on the surface of the back surface field 14.

[0049] The narrowband light-absorbing layer 11 is an N-type monocrystalline silicon wafer. It is formed by etching away the damaged layer on the surface of the monocrystalline silicon with a 10wt% NaOH aqueous solution, texturing the surface using a diluted NaOH solution, and then cleaning it using the RCA standard cleaning method. Two composite suppression layers 12 are deposited on the front and back sides of the narrowband light-absorbing layer 11, respectively. In this embodiment, the composite suppression layers 12 are made of intrinsic hydrogenated amorphous silicon, prepared using a PECVD process at a deposition temperature of 200℃, and each has a thickness of 5nm. The front emitter 13 is formed on the surface of the composite suppression layer 12 located on the back side of the narrowband light-absorbing layer 11. In this embodiment, the front emitter 13 is made of N-type hydrogenated nanocrystalline silicon oxide, prepared using a PECVD process at a deposition temperature of 170℃, and has a thickness of 10nm. The back surface field 14 is formed on the surface of the composite suppression layer 12 located on the front side of the narrow-band light-absorbing layer 11. In this embodiment, the back surface field 14 is made of P-type hydrogenated nanocrystalline silicon, prepared by PECVD process at a deposition temperature of 170°C and a thickness of 10 nm. The bottom electrode 15 includes a transparent layer 151 and a first metal electrode network 152. The transparent layer 151 is made of transparent ITO material, prepared by magnetron sputtering process at a substrate temperature of 160°C, a power of 200W, and a thickness of 110 nm. The first metal electrode network 152 is formed by printing silver paste on the surface of the bottom electrode 15 using a low-temperature silver paste screen printing process and drying it in air at 200°C for energy collection.

[0050] The tunneling layer 3 is an ITO composite layer, which is prepared by magnetron sputtering and has a thickness of 10 nm.

[0051] The top cell 2 includes a transparent electrode 21, an electron transport layer 22, a perovskite light-absorbing layer 23, and a composite hole transport layer 24, which are stacked in sequence.

[0052] The composite hole transport layer 24 includes a conductive layer 241 formed on the surface of the tunneling layer 3 away from the bottom cell 1 and a passivation layer 242 formed on the surface of the conductive layer 241 away from the bottom cell 1. See also... Figure 2 Its preparation method includes: S1. Obtain a bottom cell 1 with a tunneling layer 3 formed on its surface.

[0053] S2. A nickel oxide thin film is formed on the surface of the tunneling layer 3 by magnetron sputtering, with the substrate temperature set to any value between 150℃ and 180℃ and the power set to any value between 150W and 200W.

[0054] S3. The surface of the nickel oxide film is treated with hydrogen plasma to form a conductive layer 241 for any value between 0.1s and 0.8s.

[0055] S4. Passivation layer 242 is prepared on the surface of tunneling layer 3 after hydrogen plasma treatment by magnetron sputtering or atomic layering.

[0056] In step S2, the nickel oxide target is installed onto the target stage in the sputtering chamber, fixed, and its height is adjusted. The bottom cell 1, with the tunneling layer 3 formed on its surface, is fixed onto the sample tray and placed into the sample holder inside the sputtering chamber, with the tunneling layer 3 facing the target stage. The sputtering chamber door is closed, and the machine is started. A vacuum of 4.0 × 10⁻⁶ is drawn. -4 Argon gas was introduced, the pressure inside the vacuum chamber was adjusted, the RF power supply was started, the substrate temperature was set to 170℃, and pre-sputtering was performed at a power of 90 W to remove contaminants from the target surface. After pre-sputtering, the substrate baffle was opened, and sputtering continued at a power of 180 W for a certain period of time to deposit a nickel oxide film. The magnetron sputtering equipment was then turned off, and the sample was removed. The thickness of the nickel oxide film was measured to be 1.2 nm using an ellipsometry.

[0057] In step S3, the sample is sent into the atomic layer instrument chamber, the chamber door is closed, and H-plasma obtained by ionization at a preset power is introduced into the chamber. After a preset time, the introduction is stopped, and the chamber is flushed with inert gas N2 to remove excess H-plasma.

[0058] In step S4, a first precursor gas, trimethylaluminum (TMA), is introduced into the atomic layer instrument chamber to react chemically with the substrate surface. The chamber is then flushed with inert gas N2 to remove unreacted first precursor gas and generated byproducts. A second precursor gas, water vapor, is then introduced to react chemically with the first precursor gas on the substrate surface. The chamber is flushed again with inert gas N2 to remove excess reactants and byproducts. After repeating this cycle a preset number of times, a passivation layer 242 of alumina material for thickness measurement is formed.

[0059] The perovskite light-absorbing layer 23 is made of Cs. 0.05 MA 0.15 FA 0.8 PbI 2.25 Br 0.75 It was prepared by spin coating and has a band gap of approximately 1.68 eV.

[0060] The electron transport layer 22 includes a first electron transport layer 221 and a second electron transport layer 222. The first electron transport layer 221 is formed on the surface of the perovskite light-absorbing layer 23 by high-temperature thermal evaporation, and the material is C. 60The thickness is 20 nm. The second electric conduction layer 222 is formed on the surface of the first electric conduction layer 221 by atomic layer deposition. The material is SnO2, the deposition temperature is 100℃, and the thickness is 20 nm.

[0061] The transparent electrode 21 is formed on the surface of the second electric conduction layer 222 by magnetron sputtering. The material is zinc-doped indium oxide (IZO) with a thickness of 100 nm.

[0062] The top battery 2 also includes a second metal electrode network 25 and an anti-reflective layer 26. The second metal electrode network 25 is formed by printing silver paste onto the surface of the transparent electrode 21 using a low-temperature silver paste screen printing process and drying it in air at 200°C, and is used for energy collection. The anti-reflective layer 26 is prepared by high-temperature thermal evaporation, is made of magnesium fluoride, has a thickness of 100 nm, and is formed on the surface of the second metal electrode network 25.

[0063] Adjust the preset power and preset time in step S3 above, and adjust the preset number of times and preset thickness in step S4. Please refer to Table 1 below for the experimental parameters corresponding to each experiment.

[0064] In Table 1, the measured thickness is the thickness obtained by ellipsometer measurement, Ni 3+ / Ni 2+ The results are from X-ray photoelectron spectroscopy analysis. The data in Table 1 show that as the alumina film thickness increases, Ni... 3+ / Ni 2+ The proportion decreases; as the H-Plasma ionization power increases, Ni 3+ / Ni 2+ The proportion decreases; as H-plasma time increases, Ni 3+ / Ni 2+ The proportion has decreased.

[0065] The performance of each hole transport layer was characterized by the power conversion efficiency (PCE) of each tandem solar cell. PCE was obtained by measuring the current density-voltage (JV) characteristic curve. The JV characteristic curve was measured under the AM 1.5G standard spectrum using a Wavelabs Sinus 300 LED solar simulator combined with a Keithley 2400 digital source meter. The digital source meter provided a voltage scan range of -0.1V to 2.00V with a scan step size of 0.02V. The conversion efficiency of the device was measured, with the effective area of ​​the cell limited to 1 cm² by a metal mask. 2 Measurements were performed on 10 batteries under each condition; the statistical results can be found in the [link to statistical analysis]. Figure 3It can be seen that when the H-Plasma pretreatment power is 50W, the processing time is 0.4s, the preset number of cycles is 8, and the passivation layer 242 thickness is 1.0nm, the Ni on the modified nickel oxide surface... 3+ / Ni 2+ The value is 3.23, at which point the solar tandem cell has an effective area of ​​1 cm². 2 An average power conversion efficiency of 30.1% can be achieved on devices of this size. At this point, the hole transport layer performance is theoretically optimal, and the interfacial reaction with the perovskite can be effectively suppressed.

[0066] The solar tandem cell obtained in experiment group 5 was named Al2O3 / H-Plasma NiO. x To plot its maximum power point tracking curve after 1000 hours of irradiation, please refer to [link / reference needed]. Figure 4 This shows that its output power is relatively stable during long-term operation and is not prone to attenuation.

[0067] Alumina, prepared by atomic layering, is inexpensive and readily available, resulting in low film preparation costs, stable film formation rates, uniform film formation, and strong process compatibility. These advantages make nickel oxide modified with alumina films a promising candidate for the hole transport layer in perovskite-crystalline silicon tandem solar cells.

[0068] Example 2: The difference between this embodiment and Embodiment 1 lies only in that, in step S2 of this embodiment, the nickel oxide target is mounted on target stage 1 within the sputtering chamber, and the zirconium oxide target is mounted on target stage 2 within the sputtering chamber, with pre-sputtering and nickel oxide film deposition performed using the first RF power supply corresponding to target stage 1. In step S3, the first RF power supply is turned off, a hydrogen-argon mixture with a hydrogen ratio of 5% is introduced, the substrate bias power supply is turned on, and hydrogen plasma is generated at a power of 100W to treat the nickel oxide film surface for 0.6s, forming a conductive layer 241. In step S4, the substrate bias power supply is turned off, argon gas is introduced, the target stage 2 baffle is opened, the second RF power supply is turned on, and pre-sputtering is performed at a power of 120W to remove contaminants from the target surface. After pre-sputtering is completed, the substrate baffle is opened, and sputtering continues for a certain period of time, depositing a zirconium oxide passivation layer 242 with a thickness of 1nm. The magnetron sputtering equipment is then turned off, and the sample is removed.

[0069] In this embodiment, the composite hole transport layer 24 has a passivation layer 242 with a thickness of 1 nm and Ni 3+ / Ni 2+ Its value is 3.22, and it also has excellent hole transport capability and effective interface reaction suppression.

[0070] Example 3: The only difference between this embodiment and Embodiment 1 is that the bottom cell 1 in this embodiment is a TOPCon cell, its narrow-band light-absorbing layer 11 is the same silicon wafer as in Embodiment 1, and the composite suppression layer 12 is made of silicon oxide. Both are prepared in a PECVD chamber using a plasma-assisted method, and their thicknesses are both 1.7 nm. The front emitter 13 is a polycrystalline silicon thin film obtained by crystallizing N-type hydrogenated amorphous silicon, and the back surface field 14 is a polycrystalline silicon thin film obtained by crystallizing P-type hydrogenated amorphous silicon. After depositing N-type hydrogenated amorphous silicon thin films and P-type hydrogenated amorphous silicon thin films with a thickness of 10 nm at 170°C using a PECVD process, they are annealed in an annealing furnace at 800°C for 30 min to crystallize the amorphous silicon thin films into polycrystalline silicon thin films. The bottom electrode 15 only includes the first metal electrode network 152 and does not have a transparent layer 151. The bottom battery 1 in this embodiment also includes a passivation protective layer 16, which is made of aluminum oxide. The surface oxide layer is removed by cleaning the sample after annealing to form the front emitter 13 and the back surface field 14 in a 4.9% HF solution. Then, a 15nm thick aluminum oxide layer AlO is prepared in an atomic layer deposition (ALD) device. x H, and activated by annealing at 450 °C in a nitrogen atmosphere. The tunneling layer 3 is formed on the surface of the passivation protective layer 16.

[0071] Example 4: The only difference between this embodiment and Embodiment 3 is that the passivation layer 242 in this embodiment is made of zirconium oxide and is prepared by magnetron sputtering. The preparation method is the same as in Embodiment 2.

[0072] Example 5: The only difference between this embodiment and Embodiment 1 is that the bottom cell 1 in this embodiment is a CIGS cell, including a glass substrate 171, a back contact 172, a narrow-band light-absorbing layer 11, and a cadmium sulfide thin film 173. After ultrasonic cleaning, the surface of the glass substrate 171 near the top cell 2 is used to form a back contact 172 with a thickness of 800 nm by magnetron sputtering of a molybdenum target. The surface of the back contact 172 is deposited with CIGS to form the narrow-band light-absorbing layer 11 by thermal evaporation. First, a copper indium gallium selenide (In,Ga)2Se3 precursor is deposited at a substrate temperature of 300°C, then Cu and Se are evaporated at a substrate temperature of 530°C, and finally In, Ga, and Se are thermally evaporated to form the narrow-band light-absorbing layer 11 of the bottom cell 1. Cadmium sulfide is uniformly deposited on the surface of the narrow-band light-absorbing layer 11 using a chemical bath deposition process to form a cadmium sulfide thin film 173 with a thickness of 60 nm, constituting a PN junction structure. In this embodiment, the tunneling layer 3 is deposited on the surface of the cadmium sulfide thin film 173 and is prepared by magnetron sputtering, with TiO2 as the material. x N y The thickness is 4nm.

[0073] Comparative Example 1: The only difference between this comparative example and Example 1 is that steps S3 and S4 are omitted in this comparative example, i.e., the passivation layer 242 is not set, and the H-Plasma reduction treatment is not performed on the surface of the nickel oxide film. The resulting solar tandem cell is named NiO. x Drawing NiO x and Al2O3 / H-Plasma NiO x For the JV curve, please refer to [link / reference]. Figure 7 It can be seen that Al2O3 / H-plasma NiO x Compared to NiO x Efficiency improved by 5.1%, and stability was significantly improved.

[0074] Comparative Example 2: The only difference between this comparative example and Example 1 is that step S3 is omitted in this comparative example, but step S4 is performed, i.e., passivation layer 242 is set, but H-Plasma reduction treatment is not performed on the surface of the nickel oxide film. The resulting solar tandem cell is named Al2O3 / NiO. x Drawing Al2O3 / NiO x and Al2O3 / H-Plasma NiO x For the JV curve, please refer to [link / reference]. Figure 8 It can be seen that H-Plasma reduction treatment on the surface of nickel oxide film can improve the electrochemical performance of the battery.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A composite hole transport layer, characterized in that, include: The conductive layer (241), made of nickel oxide, is formed on the surface of the tunneling layer (3) away from the bottom cell (1), and the conductive layer (241) is located away from the surface of the tunneling layer (3) in Ni. 3+ / Ni 2+ The value can be any value between 3.0 and 3.4; A passivation layer (242), constructed of metal oxide with a band gap greater than 5 eV, is formed on the surface of the conductive layer (241) away from the bottom cell (1), and the surface of the passivation layer (241) away from the conductive layer (241) is used to form a perovskite light-absorbing layer (23).

2. The method for preparing the composite hole transport layer as described in claim 1, characterized in that, The maximum temperature during the preparation of the conductive layer (241) and the passivation layer (242) is less than or equal to 200°C.

3. The method for preparing the composite hole transport layer as described in claim 2, characterized in that, include: Obtain the bottom cell (1) with the tunneling layer (3) formed on its surface. A nickel oxide film is formed on the surface of the tunneling layer (3) by magnetron sputtering, with the substrate temperature set to any value between 150°C and 180°C and the power set to any value between 150W and 200W. The conductive layer (241) is formed by treating the surface of the nickel oxide film with hydrogen plasma, wherein the ionization power of the hydrogen plasma is any value between 40W and 110W, and the treatment time is any value between 0.1s and 0.8s. The passivation layer (242) is prepared on the surface of the conductive layer (241) after hydrogen plasma treatment by magnetron sputtering or atomic layering.

4. The method for preparing the composite hole transport layer as described in claim 3, characterized in that, The passivation layer (242) is made of any one of aluminum oxide, zirconium oxide and hafnium oxide, and the thickness of the passivation layer (242) is any value from 0.1 nm to 5 nm.

5. The method for preparing the composite hole transport layer as described in claim 3, characterized in that, When the passivation layer (242) is prepared by magnetron sputtering, the power is any value between 90W and 120W, the sputtering time is any value between 4s and 6s, and the substrate temperature is any value between 150℃ and 180℃; when the passivation layer (242) is prepared by atomic layering, the number of cycles is any value between 2 and 10, and the reaction temperature is any value between 150℃ and 180℃.

6. The method for preparing the composite hole transport layer as described in claim 3, characterized in that, The thickness of the conductive layer (241) is any value between 5 nm and 40 nm.

7. The method for preparing the composite hole transport layer as described in claim 3, characterized in that, The hydrogen plasma is formed using a magnetron sputtering device or an atomic layer deposition system.

8. A tandem solar cell, characterized in that, Includes the composite hole transport layer (24) as described in claim 1.

9. The tandem solar cell as described in claim 8, characterized in that, The battery includes a bottom cell (1), a top cell (2), and a tunneling layer (3) connecting the bottom cell (1) and the top cell (2). The top cell (2) includes a transparent electrode (21), an electron transport layer (22), a perovskite light-absorbing layer (23), and a composite hole transport layer (24) stacked sequentially. The perovskite light-absorbing layer (23) is made of Cs. a MA b FA （1-a-b） PbI c Br （3-c） , where 0≤a≤1, 0≤b≤1, 0≤c≤3, the composite hole transport layer (24) is attached to the tunneling layer (3), and the bottom cell (1) is attached to the surface of the tunneling layer (3) away from the top cell (2). The bottom cell (1) includes a narrow band light-absorbing layer (11), a composite suppression layer (12) formed on opposite sides of the narrow band light-absorbing layer (11), a front emitter (13) formed on the surface of the composite suppression layer (12) near the top cell (2), a back surface field (14) formed on the surface of the composite suppression layer (12) away from the top cell (2), and a bottom electrode (15) formed on the surface of the back surface field (14).

10. The tandem solar cell as described in claim 9, characterized in that, a is 0.05, b is 0.15, and c is 2.25.

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