Perovskite solar cell, preparation method thereof and photovoltaic module

Abstract

The invention provides a perovskite solar cell and a preparation method thereof, and a photovoltaic module, and the perovskite solar cell comprises a hole transport layer, a perovskite layer, and an electron transport layer. The perovskite solar cell further comprises a first interface layer located between the hole transport layer and the perovskite layer and / or a second interface layer located between the perovskite layer and the electron transport layer. The first interface layer and / or the second interface layer respectively and independently comprise an azo compound with a structure as shown in a formula 1: R1-N = N-R2 formula 1, and R1 and R2 are respectively and independently selected from alkyl containing cyano groups. The photoelectric conversion efficiency of the perovskite solar cell can be improved.

Description

Technical Field

[0001] This invention relates to the field of solar cells, specifically to a perovskite solar cell, its fabrication method, and a photovoltaic module. Background Technology

[0002] Solar cell devices can convert solar energy into electrical energy, effectively solving the increasingly serious energy problem. At the same time, they have received widespread attention due to their environmental friendliness and other characteristics. Among them, perovskite solar cells have developed rapidly due to their good photovoltaic characteristics and low price. However, due to factors such as the fabrication process of perovskite solar cells, existing perovskite solar cells generally suffer from low cell efficiency (photovoltaic conversion efficiency (PCE)). Summary of the Invention

[0003] This invention provides a perovskite solar cell, its preparation method, and a photovoltaic module, which can improve the efficiency of perovskite solar cells and effectively overcome the defects of existing technologies.

[0004] In one aspect, the present invention provides a perovskite solar cell, comprising a hole transport layer, a perovskite layer, and an electron transport layer. The perovskite solar cell further comprises a first interface layer located between the hole transport layer and the perovskite layer and / or a second interface layer located between the perovskite layer and the electron transport layer. The first interface layer and / or the second interface layer comprises an azo compound having the structure shown in Formula 1: R1—N=N—R2 (Formula 1), wherein R1 and R2 are each independently selected from alkyl groups containing a cyano group.

[0005] According to one embodiment of the present invention, R1 and R2 in Formula 1 are the same.

[0006] According to one embodiment of the present invention, the number of carbon atoms in R1 is 1 to 10, preferably 3 to 7; and / or, the number of carbon atoms in R2 is 1 to 10, preferably 3 to 7.

[0007] According to one embodiment of the present invention, the azo compound includes one or more of 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylpentanonitrile).

[0008] According to one embodiment of the present invention, the thickness of the first interface layer is 3 to 20 nm.

[0009] According to one embodiment of the present invention, the thickness of the second interface layer is 3 to 20 nm.

[0010] According to one embodiment of the present invention, the perovskite solar cell includes a first interface layer and a second interface layer, wherein the thickness of the first interface layer is less than or equal to the thickness of the second interface layer.

[0011] According to one embodiment of the present invention, the perovskite layer comprises a lead halide-based perovskite material.

[0012] According to one embodiment of the present invention, the thickness of the perovskite layer is 500-700 nm.

[0013] According to one embodiment of the present invention, the thickness of the hole transport layer is 7-30 nm; and / or, the hole transport layer includes one or more of NiOx, PTAA, MeO-2PACz, 2PACz, Me-4PACz, and 4PACz; and / or, the thickness of the electron transport layer is 10-40 nm; and / or, the electron transport layer includes one or more of C60, PC61BM, and SnO2.

[0014] According to one embodiment of the present invention, the band gap of the perovskite solar cell is 1.5 to 1.6 eV.

[0015] According to one embodiment of the present invention, the perovskite solar cell further includes a transparent conductive substrate located on the side of the hole transport layer opposite to the perovskite layer, and a metal electrode layer located on the side of the electron transport layer opposite to the perovskite layer.

[0016] According to one embodiment of the present invention, the perovskite solar cell further includes a hole blocking layer located between the electron transport layer and the metal electrode layer.

[0017] According to one embodiment of the present invention, the hole blocking layer comprises one or more of BCP, titanium oxide and zinc oxide; and / or, the thickness of the hole blocking layer is 5 to 10 nm.

[0018] According to one embodiment of the present invention, the transparent conductive substrate includes a substrate and a transparent conductive electrode located on the side of the substrate facing the hole transport layer. The substrate includes a glass substrate, and the transparent conductive electrode includes fluorine-doped tin oxide and / or indium tin oxide; and / or, the thickness of the metal electrode layer is 100–160 nm. and / or, the metal electrode layer includes one or more of Au, Ag, Cu, and Al.

[0019] In another aspect, the present invention provides a method for fabricating the above-mentioned perovskite solar cell, comprising the steps of sequentially forming a hole transport layer, a perovskite layer and an electron transport layer, wherein the fabrication method further comprises the steps of forming a first interface layer on the surface of the hole transport layer before forming the perovskite layer and / or forming a second interface layer on the surface of the perovskite layer before forming the electron transport layer.

[0020] According to one embodiment of the present invention, the step of forming the perovskite layer after forming a first interface layer on the surface of the hole transport layer includes: forming the first interface layer on the hole transport layer; forming a lead halide layer on the first interface layer; coating the surface of the lead halide layer with an ammonium salt solution and then performing a third annealing treatment to form the perovskite layer.

[0021] In another aspect, the present invention provides a photovoltaic module comprising the above-described perovskite solar cell or a perovskite solar cell prepared according to the above-described preparation method.

[0022] The perovskite solar cell provided by this invention introduces a first interface layer between the hole transport layer and the perovskite layer and / or introduces a second interface layer between the perovskite layer and the electron transport layer, and the first interface layer and / or the second interface layer contains an azo compound as shown in Formula 1. In this way, by constructing an interface containing an azo compound as shown in Formula 1 on the side of the perovskite layer toward the hole transport layer and / or on the side of the perovskite layer toward the electron transport layer, the photoelectric conversion efficiency of the perovskite solar cell can be improved, effectively solving the problem of low photoelectric conversion efficiency of existing perovskite solar cells. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell according to an embodiment of the present invention;

[0024] Figure 2 a is a SEM image of the perovskite layer in Comparative Example 1, and b is a SEM image of the perovskite layer in Example 1. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope 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.

[0026] In related technologies, due to limitations such as the fabrication process of perovskite solar cells, existing perovskite solar cells generally suffer from low cell efficiency (photovoltaic conversion efficiency (PCE)).

[0027] For example, due to limitations in the solution-based fabrication process of perovskite solar cells, such as the difficulty in controlling the crystallization of the perovskite thin film, the efficiency of perovskite solar cells is generally lower than the Shockley-Quiesser limit. Specifically, the fabrication process of the perovskite layer (or perovskite light-absorbing layer) in perovskite solar cells can be divided into one-step and two-step methods. Among them, the two-step process has advantages such as simple and controllable operation, high reproducibility, and large perovskite grain size, and is more widely used. In the two-step process, a halide layer is usually formed first, and then an organic ammonium salt is coated onto the halide film. The organic ammonium salt reacts with the halide (such as lead iodide) in the halide layer to form the perovskite layer. However, due to the limitations of organic ammonium salt (FA) in the process, the perovskite layer is difficult to control. + The large ionic radius of PbX6 makes it difficult for it to embed into the halide framework (such as the PbX6 octahedral framework). Therefore, the two-step method for preparing perovskite layers can lead to incomplete halide conversion, as well as problems such as uneven perovskite crystal orientation and high defect density. This results in severe nonradiative recombination and low charge carrier extraction efficiency, which in turn leads to low efficiency of perovskite solar cells.

[0028] In view of this, embodiments of the present invention provide a perovskite solar cell, such as... Figure 1 As shown, the perovskite solar cell includes a hole transport layer, a perovskite layer, and an electron transport layer. The perovskite solar cell also includes a first interface layer located between the hole transport layer and the perovskite layer and / or a second interface layer located between the perovskite layer and the electron transport layer; the first interface layer and / or the second interface layer includes an azo compound having the structure shown in Formula 1.

[0029] R1—N=N—R2 Equation 1

[0030] R1 and R2 are each independently selected from alkyl groups containing cyano groups.

[0031] According to the inventors' research, when a first interface is formed between the hole transport layer and the perovskite layer, during the formation of the perovskite layer, the azo compound (Formula 1) in the first interface layer can coordinate with halides, slowing down the crystallization rate of halides (i.e., delaying halide crystallization) and reducing the crystallinity of halides. Halides with poor crystallinity can be induced to react more fully with organic ammonium salts, which is beneficial for the subsequent penetration of organic ammonium salt solutions into the halide layer, inducing an orderly reaction between halides and organic ammonium salts, reducing residual halides, and improving the crystallinity of the perovskite. When a second interface layer is formed between the perovskite layer and the electron transport layer, the second interface layer can achieve coordination between the transition metal (such as lead (Pd) in lead iodide) in the perovskite layer and the nitrogen element of the azo compound (Formula 1) in the second interface layer, enabling the formation of dual-site transition metal ions (such as Pb).2+ The efficient passivation of perovskite solar cells reduces the vacancy defect density, thereby suppressing nonradiative recombination, which is beneficial for carrier extraction and transport, and improves the photoelectric conversion efficiency of perovskite solar cells.

[0032] Therefore, the embodiments of the present invention can improve the photoelectric conversion efficiency of perovskite solar cells by introducing a first interface layer between the hole transport layer and the perovskite layer and / or introducing a second interface layer between the perovskite layer and the electron transport layer, wherein the first interface layer and / or the second interface layer contains an azo compound as shown in Formula 1. This is particularly suitable for forming the perovskite layer by a two-step method, effectively solving the problems of incomplete halide conversion, non-uniform perovskite crystal orientation, high defect density, and low photoelectric conversion efficiency of perovskite solar cells that exist in the two-step perovskite layer formation process.

[0033] According to further research by the inventors, perovskite solar cells can simultaneously include a first interface layer located between the hole transport layer and the perovskite layer, and a second interface layer located between the perovskite layer and the electron transport layer. Thus, by introducing the first interface layer between the hole transport layer and the perovskite layer, and the second interface layer between the perovskite layer and the electron transport layer, and by containing the azo compound shown in Formula 1 in both the first and second interface layers, the crystallization of perovskite can be effectively controlled, the crystal quality optimized, and the defect density reduced, thereby further improving the photoelectric conversion efficiency of perovskite solar cells. This method is particularly suitable for forming perovskite layers using a two-step method, effectively solving problems such as incomplete halide conversion, uneven perovskite crystal orientation, high defect density, and the resulting low photoelectric conversion efficiency of perovskite solar cells in the two-step perovskite layer formation process.

[0034] In this embodiment of the invention, the perovskite layer can be prepared by a two-step method, namely, firstly forming a halide film on a first interface layer, then coating (e.g., spin-coating) an organic ammonium salt film on the halide film, and then subjecting it to annealing or other treatments to allow the halide in the halide film and the organic ammonium in the organic ammonium salt film to react and form a perovskite layer.

[0035] Specifically, in the process of forming a perovskite layer through a two-step method, a halide layer is formed on the first interface layer, and then an organic ammonium salt solution is coated on the halide layer (i.e., an organic ammonium salt film is formed), so that the organic ammonium salt reacts with the halides (such as lead iodide) in the halide layer to form perovskite, thereby forming a perovskite layer, and then a second interface layer is formed on the perovskite layer. In the first interface layer, the azo compound (Formula 1) can coordinate with halides, slowing down the crystallization rate of halides (i.e., delaying halide crystallization) and reducing the crystallinity of halides. Halides with poor crystallinity can be induced to react more fully with organic ammonium salts, which is beneficial for the subsequent penetration of organic ammonium salt solutions into the halide layer, inducing an ordered reaction between halides and organic ammonium salts, reducing residual halides, and improving the crystallinity of perovskite. The second interface layer can achieve coordination between transition metals (such as lead (Pd) in lead iodide) in the perovskite layer and the nitrogen element of the azo compound (Formula 1) in the second interface layer, enabling the formation of dual-site transition metal ions (such as Pb). 2+ The efficient passivation of perovskite layers reduces vacancy defect density, thereby suppressing nonradiative recombination, which is beneficial for carrier extraction and transport, and improves the photoelectric conversion efficiency of perovskite solar cells. Therefore, this invention, by constructing a dual interface on both sides of the perovskite layer, can effectively control the crystallization of halides and perovskite, optimize its crystal quality, and reduce passivation film defects, thereby improving the photoelectric conversion efficiency and other performance characteristics of perovskite solar cells.

[0036] Specifically, in Formula 1, the number of carbon atoms in R1 can be 1 to 10, such as 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, preferably 3 to 7.

[0037] Furthermore, in Formula 1, the number of carbon atoms in R2 can be 1 to 10, such as 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, preferably 3 to 7.

[0038] According to the inventor's research and analysis, the carbon number and other characteristics of R1 and R2 in Formula 1 will affect the steric hindrance and electronic effects of the compound shown in Formula 1, and thus affect its coordination with the halide used to form the perovskite layer or the transition metal element in the perovskite layer. Therefore, by controlling the carbon number of R1 and / or R2 in Formula 1 within the above range, it is beneficial to further improve the photoelectric conversion efficiency of perovskite solar cells.

[0039] Furthermore, R1 and R2 in Formula 1 can be the same or different. According to the inventors' further research, when R1 and R2 are the same (i.e., the entire molecule of the azo compound shown in Formula 1 is symmetrically constructed), the photoelectric conversion efficiency of the perovskite solar cell can be significantly improved. The reason for this is that the same R1 and R2 in Formula 1 makes Formula 1 have more suitable steric hindrance and electronic effects, which are more conducive to its compatibility with the perovskite layer. For example, it is beneficial for the azo compound in the first interface layer to coordinate and react with the halide used to form the perovskite layer, reducing residual halides and improving the crystal quality of the perovskite. It is also beneficial for the azo compound in the second interface layer to coordinate with the transition metal in the perovskite layer, suppressing non-radiative recombination, etc., thereby significantly improving the photoelectric conversion efficiency of the perovskite solar cell.

[0040] In some embodiments, R1 may be selected from one or more of 2-methylpropionitrile, 2-methylbutyronitrile, and 2,4-dimethylpentanonitrile.

[0041] In some embodiments, R2 may be selected from one or more of 2-methylpropionitrile, 2-methylbutyronitrile, and 2,4-dimethylpentanonitrile.

[0042] In some embodiments, the azo compound may include one or more of 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylpentanonitrile). That is, the azo compound in the first interface layer and the second interface layer may each independently include one or more of 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylpentanonitrile). This is more conducive to leveraging the coordination and reaction between the first interface layer and the halide to optimize the perovskite crystal quality, and the coordination between the second interface layer and the transition metal elements in the perovskite layer to reduce the vacancy defect density, thereby further improving the photoelectric conversion efficiency of the perovskite solar cell.

[0043] Specifically, the azo compound in the first interface layer and the azo compound in the second interface layer can be the same or different.

[0044] Generally, the thickness of the first interface layer can be less than or equal to the thickness of the second interface layer. This helps to maintain the thinness of the perovskite solar cell while giving full play to the functions of the first and second interface layers, thereby further improving the photoelectric conversion efficiency and other performance of the perovskite solar cell.

[0045] In some embodiments, the thickness of the first interface layer is 3 to 20 nm, for example, a range of 3 nm, 4 nm, 6 nm, 9 nm, 11 nm, 13 nm, 15 nm, 17 nm, 19 nm, 20 nm or any combination thereof, which is beneficial to further improve the photoelectric conversion efficiency of the perovskite solar cell. The reason for this is that by controlling the thickness of the first interface layer within the above range, it is beneficial to further reduce residual halides, improve the crystal quality of the perovskite, and facilitate carrier transport in the perovskite solar cell, thereby improving the photoelectric conversion efficiency of the perovskite solar cell.

[0046] In some embodiments, the thickness of the second interface layer is 3 to 20 nm, such as 3 nm, 5 nm, 8 nm, 10 nm, 13 nm, 15 nm, 18 nm, 20 nm or any combination thereof, which is beneficial to further improve the photoelectric conversion efficiency of perovskite solar cells. The reason for this is that it helps to further reduce the vacancy defect density, thereby suppressing nonradiative recombination, which is beneficial to the extraction and transport of charge carriers, and thus improves the photoelectric conversion efficiency of perovskite solar cells.

[0047] Specifically, defects (such as transition metal element vacancies, such as lead vacancies) often exist in the perovskite layer. When the cell is not in operation, groups such as formamidinium ions in the perovskite will spontaneously move to the vacancies and undergo nonradiative recombination, which will affect the photoelectric conversion efficiency and other performance of the perovskite solar cell. In this embodiment of the invention, by constructing a second interface layer on one side of the electron transport layer from the perovskite layer, nonradiative recombination can be effectively suppressed, thereby improving the photoelectric conversion efficiency and other performance of the perovskite solar cell.

[0048] Generally, the perovskite layer includes perovskite material, which may include R3NH3AX, where R3 represents an organic group, specifically an alkyl group, such as methyl; A represents a transition metal element, specifically lead (Pb); and X represents a halogen, specifically bromine (Br) and / or iodine (I).

[0049] Specifically, the perovskite layer may include lead halide-based perovskite materials (i.e., the transition metal element A in the perovskite layer is Pb), which is beneficial for compatibility with the first and second interface layers mentioned above, thereby improving the photoelectric conversion efficiency of the perovskite solar cell.

[0050] Specifically, in the formation of the perovskite layer, the halide used is lead halide (such as lead iodide), and the resulting perovskite is a lead halide-based perovskite material. In the first interface layer, the azo compound (Formula 1) can coordinate with lead halide, slowing down the crystallization rate and reducing the crystallinity of lead halide. The poorly crystallized lead halide can induce a more complete reaction with organic ammonium salts, leading to an ordered reaction between lead halide and organic ammonium salts, reducing residual lead halide, and improving the crystallinity of the perovskite. The second interface layer can achieve dual-site Pb through the coordination (Pd-N) between Pd in ​​the perovskite layer and the nitrogen element of the azo compound in the second interface layer. 2+ The efficient passivation reduces the vacancy defect density, thereby suppressing nonradiative recombination, which is beneficial for carrier extraction and transport, and improves the photoelectric conversion efficiency of perovskite solar cells.

[0051] In some embodiments, the thickness of the perovskite layer is 500–700 nm, for example, a range of 500 nm, 550 nm, 600 nm, 650 nm, 700 nm or any combination thereof.

[0052] In some embodiments, the thickness of the hole transport layer is 7 to 30 nm, for example, a range of 7 nm, 8 nm, 10 nm, 13 nm, 15 nm, 18 nm, 20 nm, 23 nm, 25 nm, 28 nm, 30 nm or any combination thereof.

[0053] In some embodiments, the hole transport layer includes oxynitride (NiO) x One or more of the following: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz), [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz), and [4-(9H-carbazole-9-yl)butyl]phosphonic acid (4PACz).

[0054] In some embodiments, the thickness of the electron transport layer is 10 to 40 nm, for example, a range of 10 nm, 13 nm, 15 nm, 18 nm, 20 nm, 23 nm, 25 nm, 28 nm, 30 nm, 33 nm, 35 nm, 38 nm, 40 nm or any combination thereof.

[0055] In some embodiments, the electron transport layer comprises one or more of fullerene (C60), methyl [6,6]-phenyl-C61-butyrate (PC61BM), and tin oxide (SnO2).

[0056] Generally, the smaller the band gap of a semiconductor material, the higher its photoelectric conversion efficiency. However, an excessively small band gap can lead to the recombination of photogenerated electrons and holes, which can also affect the efficiency of solar cells to some extent. The perovskite solar cell in this embodiment of the invention has a band gap of 1.5 to 1.6 eV, which is beneficial for further improving the photoelectric conversion efficiency and other performance characteristics of the perovskite solar cell.

[0057] In this embodiment of the invention, the perovskite solar cell can be an inverted perovskite solar cell, and the cell structure is PIN type. For example... Figure 1 As shown, the perovskite solar cell also includes a transparent conductive substrate located on the side of the hole transport layer opposite to the perovskite layer, and a metal electrode layer located on the side of the electric transport layer opposite to the perovskite layer. Specifically, the transparent conductive substrate may include a substrate and a transparent conductive electrode (or transparent conductive electrode layer) located between the substrate and the hole transport layer.

[0058] In some embodiments, the substrate may include a glass substrate.

[0059] In some embodiments, the transparent conductive electrode comprises fluorine-doped tin oxide (FTO) and / or indium tin oxide (ITO).

[0060] In some embodiments, the thickness of the metal electrode layer is 100 to 160 nm, for example, a range of 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm or any two of these.

[0061] In some embodiments, the metal electrode layer includes one or more of gold (Au), silver (Ag), copper (Cu), and aluminum (Al).

[0062] In some embodiments, such as Figure 1 As shown, perovskite solar cells may also include a hole-blocking layer located between the electron transport layer and the metal electrode layer, which can block holes from moving to the cathode (metal electrode layer), avoid leakage and other problems, thereby further optimizing the performance of perovskite solar cells.

[0063] In some embodiments, the hole blocking layer may include one or more of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), titanium dioxide (TiO2), and zinc oxide (ZnO), which helps to block holes from moving toward the cathode (metal electrode layer), avoiding problems such as leakage, while facilitating electron transport and further improving the photoelectric conversion efficiency and other performance of the perovskite solar cell.

[0064] In some embodiments, the thickness of the hole blocking layer is 5 to 10 nm, for example, a range of 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm or any combination thereof. Thus, the hole blocking layer has a thickness of not less than 5 nm, which is beneficial for blocking holes from moving to the cathode (metal electrode layer) and avoiding problems such as leakage. At the same time, the hole blocking layer has a thickness of not more than 10 nm, which is beneficial for taking into account electron transport capability, thereby further improving the photoelectric conversion efficiency and other performance of the perovskite solar cell.

[0065] This invention also provides a method for fabricating the above-mentioned perovskite solar cell, comprising the steps of sequentially forming a hole transport layer, a perovskite layer, and an electron transport layer, wherein the fabrication method includes the steps of forming a first interface layer on the surface of the hole transport layer before forming the perovskite layer and / or forming a second interface layer on the surface of the perovskite layer before forming the electron transport layer.

[0066] Specifically, the step of forming a perovskite layer after forming a first interface layer on the surface of the hole transport layer may include: forming a first interface layer on the hole transport layer; forming a lead halide layer on the first interface layer; coating the surface of the lead halide layer with an ammonium salt solution; and performing a third annealing treatment to form the perovskite layer.

[0067] In some embodiments, the method for preparing the perovskite solar cell described above may include the following steps: forming a first interface layer on a hole transport layer; forming a lead halide layer on the first interface layer; coating an ammonium salt solution on the surface of the lead halide layer and then performing a third annealing treatment to form a perovskite layer; forming a second interface layer on the surface of the perovskite layer; and forming an electron transport layer on the surface of the second interface layer.

[0068] In practice, the transparent conductive substrate can be cleaned and hydrophilicated first (by cleaning and hydrophilicating the transparent conductive substrate, the transparent conductive electrodes in the transparent conductive substrate can be cleaned and hydrophilicated). Specifically, the transparent conductive substrate can be ultrasonically cleaned sequentially with cleaning agent, deionized water, and anhydrous ethanol, then dried with inert gas such as nitrogen, and then hydrophilicated by ultraviolet-oxygen treatment. Afterward, the transparent conductive substrate can be transferred to a glove box with an inert atmosphere such as nitrogen. The ultrasonic cleaning time can be 8 to 15 minutes, for example, about 10 minutes, and the ultraviolet-oxygen treatment time can be 5 to 12 minutes, for example, about 8 minutes.

[0069] In some specific embodiments, the cleaning process of the transparent conductive substrate may include: wiping the substrate clean with a cleaning agent mixed with deionized water using a cleaning agent; placing the cleaned substrate in a substrate holder and then in a beaker, adding deionized water mixed with the cleaning agent until it covers the substrate surface, and ultrasonically cleaning for 8-15 minutes, for example, 10 minutes; discarding the detergent water (i.e., deionized water mixed with the cleaning agent), adding clean deionized water until it covers the substrate surface, and ultrasonically cleaning for 8-15 minutes, for example, 10 minutes; discarding the deionized water, adding anhydrous ethanol until it covers the substrate surface, and ultrasonically cleaning for 8-15 minutes, for example, 10 minutes; and drying the substrate using a nitrogen gun.

[0070] Subsequently, a first coating liquid for forming a hole transport layer can be applied to the surface of a transparent conductive substrate, and after a first annealing treatment, a hole transport layer is formed on the surface of the transparent conductive substrate.

[0071] The first coating liquid includes a hole transport material and a first solvent. The first solvent may include an alcohol solvent, such as ethanol (specifically anhydrous ethanol). The hole transport material may include one or more of NiOx, PTAA, MeO-2PACz, 2PACz, Me-4PACz, and 4PACz.

[0072] The first coating liquid can be spin-coated onto the surface of a transparent conductive substrate using a spin-coating method. The first coating liquid covers the entire surface of the transparent conductive substrate, and the volume of the first coating liquid is, for example, 80 to 120 μL.

[0073] The temperature of the first annealing treatment can be 80-120℃, for example 100℃, and the time can be 8-12 minutes, for example 10 minutes.

[0074] Subsequently, a second coating liquid for forming the first interface layer is applied to the surface of the hole transport layer to form the first interface layer.

[0075] The second coating liquid includes a second solvent and an azo compound (or functional material) having the structure shown in Formula 1. The second solvent includes an organic solvent, specifically dimethylformamide (DMF).

[0076] Specifically, in the second coating solution, the concentration of the azo compound having the structure shown in Formula 1 can be 0.2 to 2 mg / mL, for example, 0.2 mg / mL, 0.5 mg / mL, 0.8 mg / mL, 1 mg / mL, 1.2 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2 mg / mL or any combination thereof.

[0077] Specifically, the second coating liquid can be spin-coated onto the surface of the hole transport layer by spin coating, so that the second coating liquid covers the entire surface of the hole transport layer, and the volume of the second coating liquid is, for example, 80 to 120 μL.

[0078] Generally, after the second coating liquid is applied to the hole transport layer, a non-fluid first interface layer is formed, and then a third coating liquid is applied to the surface of the second interface layer. Specifically, during the spin coating process of the second coating liquid, the solvent in it continuously evaporates. After the spin coating of the second coating liquid is completed, it can be left to stand for a certain period of time as needed, such as 10 min to 30 min (e.g., about 20 min), to form a non-fluid first interface layer.

[0079] Subsequently, a third coating solution for forming a halide layer is applied to the surface of the first interface layer, and after a second annealing treatment, a halide layer is formed; then an ammonium salt solution is applied to the surface of the halide layer, and after a third annealing treatment, a perovskite layer is formed.

[0080] The third coating solution is a halide precursor solution, which may include a halide and a third solvent. The halide may include lead iodide (PbI2), and the third solvent may include DMF and / or dimethyl sulfoxide (DMSO).

[0081] Specifically, the third coating liquid can be spin-coated onto the surface of the first interface layer by spin coating. The third coating liquid covers the entire surface of the first interface layer. The volume of the third coating liquid is, for example, 80 to 120 μL, and the temperature of the third coating liquid can be 22 to 25 °C.

[0082] Specifically, the temperature of the second annealing treatment can be 60-80℃, for example 70℃, and the time can be 20-40s, for example 30s.

[0083] In addition, the second annealing process can be carried out in air with a humidity of 30-40%.

[0084] Specifically, the ammonium salt solution (organic ammonium salt solution) includes an organic ammonium salt (R3NH3X) and a fourth solvent, such as methylammonium chloride (MACl(CH3NH3Cl)), and the third solvent may include isopropanol (IPA).

[0085] Specifically, the temperature of the third annealing treatment can be 140–160°C, for example 150°C, and the time can be 10–20 min, for example 15 min.

[0086] Subsequently, the fifth coating liquid used to form the second interface layer can be applied to the surface of the perovskite layer, and after the fourth annealing treatment, the second interface layer is formed.

[0087] Specifically, the temperature for the fourth annealing can be 80℃ to 120℃, for example, 100℃, and the time can be 5 to 10 minutes.

[0088] The fifth coating liquid includes a fifth solvent and an azo compound (or functional material) having the structure shown in Formula 1. The fifth solvent includes an organic solvent, specifically including IPA.

[0089] Specifically, in the fifth coating solution, the concentration of the azo compound having the structure shown in Formula 1 can be 0.2 to 2 mg / mL, for example, 0.2 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.8 mg / mL, 1 mg / mL, 1.3 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2 mg / mL or any combination thereof, which is beneficial for forming a first interface layer of suitable thickness. At the same time, during the spin coating process of the second coating solution, it is beneficial for the solvent in the second coating solution to evaporate, and a non-fluid dynamic first interface layer is formed more quickly, thereby improving the formation efficiency of the first interface layer.

[0090] Subsequently, an electron transport layer can be formed on the surface of the second interface layer using vacuum evaporation or spin coating. Generally, when the electron transport layer material is C60, it can be formed by vacuum evaporation; when the electron transport layer material includes PC61BM and / or SnO2, it can be formed by spin coating.

[0091] Subsequently, a sixth coating liquid for forming a hole blocking layer can be applied to the surface of the electron transport layer, and after a fifth annealing treatment, a hole blocking layer is formed.

[0092] The sixth coating liquid includes a sixth solvent and a material for forming a hole-blocking layer. The material for forming the hole-blocking layer may include BCP, etc., and the sixth solvent may include IPA.

[0093] Specifically, the sixth coating liquid can be spin-coated onto the surface of the electron transport layer using a spin-coating method.

[0094] Specifically, the temperature of the fifth annealing treatment can be 60-80℃, for example 70℃, and the time can be 3-7 minutes, for example 5 minutes.

[0095] Subsequently, a metal electrode layer can be formed on the surface of the hole blocking layer using vacuum evaporation technology to produce a perovskite solar cell.

[0096] In the embodiments of the present invention, unless otherwise specified, the spin coating method, vacuum evaporation method and other processes involved can be conventional operations in the field, and there are no special restrictions on them.

[0097] This invention also provides a photovoltaic module, including the above-described perovskite solar cell or a perovskite solar cell prepared according to the above-described method for preparing perovskite solar cells, which has advantages corresponding to the above-described perovskite solar cells, and will not be described in detail here.

[0098] The present invention will be further described below through specific embodiments.

[0099] Example 1

[0100] A schematic diagram of the perovskite solar cell in Example 1 is shown below. Figure 1 As shown, it includes a substrate, a transparent conductive electrode, a hole transport layer, a first interface layer, a perovskite layer, a second interface layer, an electron transport layer, a hole blocking layer, and a metal electrode layer, which are stacked sequentially. The hole transport layer has a thickness of 8 nm, the perovskite layer has a thickness of 650 nm, the electron transport layer has a thickness of 30 nm, the hole blocking layer has a thickness of 6 nm, and the metal electrode layer has a thickness of 120 nm.

[0101] The fabrication process of the perovskite solar cell in Example 1 is as follows:

[0102] (1) Cleaning the substrate and hydrophilic treatment of the surface (surface treatment): After cleaning the transparent conductive substrate with a cleaning agent, ultrasonically clean it with cleaning agent, deionized water and anhydrous ethanol for 10 minutes in sequence, and blow it dry with a nitrogen gun; use a PM20L plasma cleaner to treat the cleaned transparent conductive substrate with ultraviolet-oxygen for 8 minutes, and then transfer the transparent conductive substrate to a nitrogen glove box; wherein, the substrate in the transparent conductive substrate is a glass substrate and the transparent conductive electrode is an FTO electrode.

[0103] (2) Preparation of hole transport layer: Dissolve 0.5 mg of MeO-2PACz in 1 mL of anhydrous ethanol and dissolve 0.5 mg of Me-4PACz in 1 mL of anhydrous ethanol. Mix the dissolved MeO-2PACz and Me-4PACz solutions at a volume ratio of 1:3 to obtain the first coating solution. Take 80-120 μL of the prepared first coating solution and spread it on the surface of the surface-treated transparent conductive substrate (i.e., the surface of the transparent conductive electrode). Spin coat it at a speed of 3000 rpm for 30 s with an acceleration of 1500 rpm / s. Then anneal the substrate with the hole transport material at 100°C for 10 minutes to form the hole transport layer.

[0104] (3) Preparation of the first interface layer: Dissolve 0.5 mg of 2,2'-azobis(2-methylbutyronitrile) in 1 mL of DMF (i.e., the concentration of the second coating solution is 0.5 mg / mL) to obtain the second coating solution (2,2'-azobis(2-methylbutyronitrile) solution); spin-coat the second coating solution onto the surface of the hole transport layer and cover the surface of the hole transport layer (the volume of the second coating solution is about 80-120 μL), spin-coat at a speed of 4000 rpm for 30 s with an acceleration of 2000 rpm / s, and let stand for about 20 min after spin-coating to form the first interface layer;

[0105] (4) Preparation of lead iodide layer: Dissolve 601.6 mg PbI2, 4 mg RbCl and 10 mg CsCl in 1 mL of a solvent made of DMF and DMSO in a volume ratio of 9:1 (i.e. DMF:DMSO(v:v)=9:1), place it on a hot plate at 50-60℃ and heat for 12 h to prepare lead iodide solution (third coating solution); spin coat the lead iodide solution onto the surface of the first interface layer and cover the surface of the first interface layer (the volume of lead iodide solution is about 70-120 μL), spin coat at 1700 rpm for 30 s with an acceleration of 1000 rpm / s, and anneal at 70℃ for 30 s after spin coating to form lead iodide layer (halide layer);

[0106] (5) Preparation of ammonium salt layer: Dissolve 90 mg formamidine hydroiodide (FAI) and 10 mg MACl in 1 mL IPA, let stand for 12 h to prepare ammonium salt solution; take 80 μL of the prepared ammonium salt solution, spin coat at 1800 rpm for 30 s with an acceleration of 1500 rpm / s, and quickly drop it onto the surface of the annealed and cooled lead iodide layer in the 5th to 8th second of the spin coating. After spin coating, anneal in air at 150 °C for 15 minutes to form perovskite layer;

[0107] (6) Preparation of the second interface layer: Dissolve 1 mg of 2,2'-azobis(2-methylbutyronitrile) in 1 mL of IPA (i.e., the concentration of the fifth coating solution is 1 mg / mL) to obtain the fifth coating solution; take 20 μL of the fifth coating solution, spin coat at 4000 rpm for 30 s with an acceleration of 2000 rpm / s, and quickly drop it onto the surface of the annealed and cooled perovskite layer in the 5th to 8th second after the spin coating begins, and then anneal at 100℃ for 5 min to form the second interface layer;

[0108] (7) Preparation of electron transport layer: C60 is deposited on the second interface layer by vacuum evaporation to form electron transport layer;

[0109] (8) Preparation of hole blocking layer: Dissolve 0.5 mg of BCP in 1 mL of IPA and stir at 60 °C for 12 hours to obtain the sixth coating solution (BCP solution); take 50 μL of BCP solution and spin coat at 4000 rpm for 30 s with an acceleration of 2000 rpm / s. In the 5th to 8th second of the spin coating, quickly drop it onto the electron transport layer. After spin coating, anneal at 70 °C for 5 minutes to form hole blocking layer.

[0110] (9) Preparation of metal electrode layer: Ag metal electrode is deposited on hole blocking layer by vacuum evaporation technology to form metal electrode layer and obtain perovskite solar cell.

[0111] Examples 2 to 5, and Examples 8 to 13 differ from Example 1 in that the concentration of the second coating liquid (i.e., the concentration of the first interface layer material) or the concentration of the fifth coating liquid (i.e., the concentration of the second interface layer material) is different. Correspondingly, the thickness of the first interface layer or the thickness of the second interface layer is different, as shown in Table 1. The other conditions are the same as in Example 1.

[0112] Examples 6-7 and 14: The functional materials of the first interface layer and / or the second interface layer are different, as shown in Table 1. The other conditions are the same as in Example 1.

[0113] Example 15: The difference from Example 1 is that the first interface layer is not formed (that is, the perovskite solar cell structure of Example 15 includes, from bottom to top, a transparent conductive substrate, a hole transport layer, a perovskite layer, a second interface layer, an electron transport layer, a hole blocking layer, and a metal electrode layer), while the other conditions are the same as those of Example 1.

[0114] Example 16: The difference from Example 1 is that a second interface layer is not formed (i.e., the perovskite solar cell structure of Example 16 includes, from bottom to top, a transparent conductive substrate, a hole transport layer, a first interface layer, a perovskite layer, an electron transport layer, a hole blocking layer, and a metal electrode layer), while the other conditions are the same as in Example 1.

[0115] Comparative Example 1: The difference from Example 1 is that the first interface layer and the second interface layer are not formed (that is, the perovskite solar cell structure of Comparative Example 1 includes, from bottom to top, a transparent conductive substrate, a hole transport layer, a perovskite layer, an electron transport layer, a hole blocking layer and a metal electrode layer), and the other conditions are the same as those of Example 1.

[0116] Scanning electron microscopy (SEM) tests were performed on the perovskite layers in each embodiment and comparative example. The results showed that in Examples 1-14 and Example 16, a first interface layer was provided on the side of the perovskite layer facing the hole transport layer, which could eliminate residual lead iodide and improve the crystal quality of the perovskite. In Comparative Example 1, which did not have a first interface layer, the perovskite layer contained more residual lead iodide, and the crystal quality of the perovskite layer was poor. Taking Example 1 and Comparative Example 1 as examples... Figure 2 Image a is a surface SEM image of the perovskite layer (perovskite film) in Comparative Example 1. Figure 2 b is a surface SEM image of the perovskite layer (perovskite film) in Example 1. Figure 2 Light-colored grains are lead iodide, dark-colored grains are perovskite. Figure 2 As can be seen, in Comparative Example 1, without the first interface layer, there are many lead iodide grains distributed at the perovskite grain boundaries in the perovskite layer. In Example 1, the first interface layer is provided on the side of the perovskite layer towards the hole transport layer. The residual lead iodide in the perovskite film treated with the first interface layer is significantly reduced, and the perovskite grain size is increased, resulting in a significant improvement in quality. This indicates that the first interface layer treatment can effectively eliminate residual lead iodide, improve the perovskite crystal quality, and increase the photoelectric conversion efficiency of the perovskite solar cell.

[0117] Furthermore, although no first interface layer is provided in Example 15, a second interface layer is provided between the perovskite layer and the electron transport layer. This reduces the defect density of the perovskite layer, suppresses non-radiative recombination, and also improves the photoelectric conversion efficiency of the perovskite solar cell. In particular, in Examples 1 to 14, the simultaneous provision of a first interface layer on the side of the perovskite layer facing the hole transport layer and a second interface layer on the side of the perovskite layer facing the electron transport layer significantly improves the photoelectric conversion efficiency and other performance characteristics of the perovskite solar cell.

[0118] In addition, current density-voltage characteristic curves (JV) were tested on the perovskite solar cells of each embodiment and comparative example. The test procedure is as follows: the perovskite solar cells were placed in an area of ​​0.16 cm². 2 On the fixture, under standard test conditions (illuminance of 100 mW / cm²), 2 The JV characteristics of the perovskite solar cell were tested under AM 1.5G solar irradiation (using an AM 1.5G solar simulator). The short-circuit current density Jsc, open-circuit voltage Voc, fill factor FF, and photoelectric conversion efficiency PCE of the cell were measured and are shown in Table 2.

[0119] The band gap of the perovskite solar cells in Examples 1 to 16 and Comparative Example 1 is approximately 1.57e.

[0120] Table 1

[0121]

[0122] Table 2

[0123]

[0124] As can be seen from the test results in Table 2, compared with Comparative Example 1, setting a first interface layer between the perovskite layer and the hole transport layer and / or setting a second interface layer between the perovskite layer and the electron transport layer in Examples 1 to 16 can effectively improve the photoelectric conversion efficiency (PCE) of perovskite solar cells. In particular, setting a first interface layer on the side of the perovskite layer facing the hole transport layer and a second interface layer on the side of the perovskite layer facing the electron transport layer in Examples 1 to 14 can more significantly improve the photoelectric conversion efficiency and other performance of perovskite solar cells.

[0125] Furthermore, as can be seen from Examples 1 and 8 to 10, compared with Examples 8 and 10, Examples 1 and 9 further improve the photoelectric conversion efficiency of perovskite solar cells by further controlling the thickness of the first interface layer in the range of 3 to 20 nm.

[0126] Furthermore, as can be seen from Examples 1 and 11 to 13, compared with Examples 11 and 13, Examples 1 and 12 further improve the photoelectric conversion efficiency of perovskite solar cells by further controlling the thickness of the first interface layer in the range of 3 to 20 nm.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A perovskite solar cell, characterized in that, The perovskite solar cell includes a hole transport layer, a perovskite layer, and an electron transport layer. The perovskite solar cell also includes a first interface layer located between the hole transport layer and the perovskite layer and / or a second interface layer located between the perovskite layer and the electron transport layer. The first interface layer and / or the second interface layer comprise an azo compound having the structure shown in Formula 1: R1—N=N—R2 Equation 1 R1 and R2 are each independently selected from alkyl groups containing cyano groups.

2. The perovskite solar cell according to claim 1, characterized in that, R1 and R2 in Equation 1 are the same.

3. The perovskite solar cell according to claim 1, characterized in that, The number of carbon atoms in R1 is 1 to 10, preferably 3 to 7; And / or, the number of carbon atoms in R2 is 1 to 10, preferably 3 to 7.

4. The perovskite solar cell according to claim 3, characterized in that, The azo compound includes one or more of 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylpentanonitrile).

5. The perovskite solar cell according to claim 1, characterized in that, The thickness of the first interface layer is 3–20 nm.

6. The perovskite solar cell according to claim 1, characterized in that, The thickness of the second interface layer is 3–20 nm.

7. The perovskite solar cell according to any one of claims 1-6, characterized in that, The perovskite solar cell includes a first interface layer and a second interface layer, wherein the thickness of the first interface layer is less than or equal to the thickness of the second interface layer.

8. The perovskite solar cell according to any one of claims 1-6, characterized in that, The perovskite layer comprises lead halide-based perovskite material.

9. The perovskite solar cell according to any one of claims 1-6, characterized in that, The thickness of the perovskite layer is 500–700 nm.

10. The perovskite solar cell according to any one of claims 1-6, characterized in that, The thickness of the hole transport layer is 7–30 nm; And / or, the hole transport layer includes one or more of NiOx, PTAA, MeO-2PACz, 2PACz, Me-4PACz, and 4PACz; And / or, the thickness of the electron transport layer is 10–40 nm; And / or, the electron transport layer includes one or more of C60, PC61BM, and SnO2.

11. The perovskite solar cell according to any one of claims 1-6, characterized in that, The perovskite solar cell has a band gap of 1.5–1.6 eV.

12. The perovskite solar cell according to any one of claims 1-6, characterized in that, The perovskite solar cell also includes a transparent conductive substrate located on the side of the hole transport layer opposite to the perovskite layer, and a metal electrode layer located on the side of the electron transport layer opposite to the perovskite layer.

13. The perovskite solar cell according to claim 12, characterized in that, The perovskite solar cell also includes a hole blocking layer located between the electron transport layer and the metal electrode layer.

14. The perovskite solar cell according to claim 13, characterized in that, The hole-blocking layer includes one or more of BCP, titanium dioxide, and zinc oxide; And / or, the thickness of the hole blocking layer is 5 to 10 nm.

15. The perovskite solar cell according to claim 12, characterized in that, The transparent conductive substrate includes a substrate and a transparent conductive electrode located on the side of the substrate facing the hole transport layer. The substrate includes a glass substrate, and the transparent conductive electrode includes fluorine-doped tin oxide and / or indium tin oxide. And / or, the thickness of the metal electrode layer is 100–160 nm; And / or, the metal electrode layer includes one or more of Au, Ag, Cu, and Al.

16. A method for preparing a perovskite solar cell according to any one of claims 1-15, characterized in that, The method includes the steps of sequentially forming a hole transport layer, a perovskite layer, and an electron transport layer. The preparation method further includes the steps of forming a first interface layer on the surface of the hole transport layer before forming the perovskite layer and / or forming a second interface layer on the surface of the perovskite layer before forming the electron transport layer.

17. The method for preparing a perovskite solar cell according to claim 16, characterized in that, The step of forming the perovskite layer after forming the first interface layer on the surface of the hole transport layer includes: The first interface layer is formed on the hole transport layer; A lead halide layer is formed on the first interface layer. After an ammonium salt solution is coated on the surface of the lead halide layer, a third annealing treatment is performed to form the perovskite layer.

18. A photovoltaic module, characterized in that, This includes the perovskite solar cell according to any one of claims 1-15 or the perovskite solar cell prepared according to the preparation method described in claim 16 or 17.

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