Perovskite solar cell and preparation method thereof

Abstract

The invention provides a perovskite solar cell. The perovskite solar cell comprises a NiOx hole transport layer, a perovskite light absorption layer and a self-assembly molecular layer, wherein the self-assembly molecular layer is compounded between the NiOx hole transport layer and the perovskite light absorption layer; the self-assembly molecular layer comprises an organic self-assembly compound. The invention also provides a preparation method of the perovskite solar cell. According to the perovskite solar cell provided by the invention, the organic self-assembly compound is introduced, and the anchoring group at one end of the perovskite solar cell is anchored on the surface of the NiOx film to form a strong and stable covalent bond, so that defects in the NiOx film are passivated, and selective contact is realized to reduce interface recombination and promote charge transfer; the passivation group at the other end can passivate the perovskite layer, thereby reducing the vacancy defect of the perovskite layer, promoting the crystallization of the perovskite layer, finally achieving the regulation and control of the interface defect of the perovskite light absorption layer, and improving the photoelectric conversion efficiency of the cell.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and in particular to a perovskite solar cell and a preparation method thereof. Background Art

[0002] Perovskite solar cells (PSCs) have garnered widespread attention due to their exceptional optoelectronic properties, including high light absorption coefficient, long carrier lifetime, and high defect tolerance. Since their introduction in 2009, PSCs have seen improvements in power conversion efficiency (PCE) from an initial 3.8% to a currently certified 26.1%, approaching the 26.81% efficiency record for crystalline silicon solar cells. Furthermore, their solution-based fabrication method offers promising prospects for industrialization in terms of both efficiency and cost.

[0003] In recent years, with the continuous advancement of the industrialization of perovskites, pin-type planar heterojunction perovskite solar cells have attracted widespread attention due to their simple structure and compatibility with large-scale production processes. Among the hole transport layers reported for inverted pin structures, nickel oxide in p-type inorganic semiconductors has been particularly favored due to its low cost, high transmittance, stable chemical properties and easy large-scale preparation. However, NiO x It also has serious disadvantages, such as low intrinsic conductivity, high defect density, mismatch with the perovskite interface energy level, and reaction with the perovskite precursor. Even though the perovskite material itself has a high tolerance to defects, the untreated NiO x The large number of defects and deep potential wells at the interface between the film and the perovskite will cause a high degree of non-radiative recombination, thus limiting the NiO x Photovoltaic performance of perovskite-based solar cells.

[0004] Introducing interface layer for modification and modification is the key to optimizing NiO x One of the main means of photovoltaic performance of NiO-based perovskite solar cells, but the interface layer is x The modification of the NiO layer will also affect the perovskite light absorbing layer. So what kind of material should be introduced to achieve the NiO x The compatibility and performance improvement of the layer and the perovskite light absorbing layer are rarely reported in the existing technology. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a perovskite solar cell. By introducing organic self-assembly compounds, the interface defects of the perovskite light-absorbing layer are regulated, thereby ultimately improving the photoelectric conversion efficiency of the perovskite solar cell and making the perovskite solar cell have excellent performance.

[0006] In view of this, the present application provides a perovskite solar cell, comprising: NiOx a hole transport layer, a perovskite light absorbing layer and a self-assembled molecular layer between the NiO x a hole transport layer and the perovskite light absorbing layer;

[0007] the self-assembled molecular layer comprises an organic self-assembled compound selected from one or more of the following compounds:

[0008]

[0009] wherein n is independently selected from an integer between 1 and 10.

[0010] Preferably, the thickness of the self-assembled molecular layer is 1-5 nm; n is selected from 3-6.

[0011] Preferably, the perovskite material of the perovskite light absorbing layer has a general formula of ABX3, wherein A is selected from one or more of CH3NH3 + , CH(NH2)2 + , Cs + and Rb + , B is selected from one or more of Pb 2+ , Sn 2+ and Ge 2+ , and X is one or more of Cl - , Br - and I - ; the thickness of the perovskite light absorbing layer is 200-1000 nm.

[0012] The application also provides a perovskite solar cell, comprising: a substrate, a NiO x a hole transport layer, a self-assembled molecular layer, a perovskite light absorbing layer, an electron transport layer and an electrode layer;

[0013] the self-assembled molecular layer comprises an organic self-assembled compound selected from one or more of the following compounds:

[0014]

[0015] wherein n is independently selected from an integer between 1 and 10.

[0016] Preferably, the thickness of the self-assembled molecular layer is 1-5 nm; n is selected from 3-6.

[0017] Preferably, the perovskite material of the perovskite light absorbing layer has a general formula of ABX3, wherein A is selected from one or more of CH3NH3 + , CH(NH2)2 + , Cs + and Rb +One or more of, B is selected from Pb 2+ 、Sn 2+ and Ge 2+ One or more of, X is Cl - Br - and I - Any one or more of the following; the thickness of the perovskite light-absorbing layer is 200 to 1000 nm.

[0018] Preferably, the material of the electron transport layer is selected from C 60 , PCBM, TiO2, BCP, SnO2, ZnO or one or more of ZnO-ZnS; the material of the electrode layer is selected from one of Au, Ag and low-temperature carbon electrode.

[0019] The present application also provides a method for preparing the perovskite solar cell, comprising the following steps:

[0020] A) Preparation of NiO on the substrate surface x hole transport layer;

[0021] B) In the NiO x Preparation of a self-assembled molecular layer on the surface of the hole transport layer;

[0022] C) preparing a perovskite light-absorbing layer on the surface of the self-assembled molecular layer;

[0023] D) preparing an electron transport layer on the surface of the perovskite light absorbing layer;

[0024] E) preparing an electrode layer on the surface of the electron transport layer.

[0025] Preferably, the preparation method of the self-assembled molecular layer is specifically as follows:

[0026] mixing the organic self-assembly compound and the organic solvent to obtain a mixed solution;

[0027] The mixed solution was spin-coated on NiO x The surface of the hole transport layer is then annealed at 80-120° C. for 10-30 minutes, and after cleaning, it is annealed again at 80-120° C. for 1-5 minutes to obtain a self-assembled molecular layer;

[0028] The organic solvent is selected from isopropanol and / or ethanol; the molar concentration of the organic self-assembly compound in the mixed solution is 1-5 mM.

[0029] Preferably, the NiO x The preparation method of the hole transport layer is specifically as follows:

[0030] mixing a nickel source and a solvent to obtain a precursor solution;

[0031] The precursor solution is spin-coated on the surface of the substrate, annealed at 350-450℃ for 30-50min to obtain NiO x A hole transport layer.

[0032] Preferably, the preparation method of the perovskite light-absorbing layer is specifically as follows:

[0033] The perovskite raw materials and the solvent are mixed, and after heating, a perovskite precursor solution is obtained;

[0034] The perovskite precursor solution is spin-coated on the surface of the self-assembled molecular layer, and after annealing, a perovskite light-absorbing layer is obtained;

[0035] The solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, dimethylacetamide, N,N-dimethylacrylurea, acetonitrile and 2-mercaptoethanol; and the concentration of the perovskite precursor solution is 1-5M.

[0036] The present application provides a perovskite thin film, which comprises NiO x A hole transport layer, a perovskite light-absorbing layer and a self-assembled molecular layer complexed between the NiO x A hole transport layer and the perovskite light-absorbing layer; the self-assembled molecular layer comprises an organic self-assembled compound; the organic self-assembled compound in the self-assembled molecular layer of the present application is a bifunctional organic self-assembled monomer based on imidazole and pyrazole, which can simultaneously passivate the surface of the NiO x and the perovskite light-absorbing layer, reduce the interface defects; specifically, the anchoring group phosphonic acid group, carboxylic acid group, boric acid group and or mercapto group contained at one end of the organic self-assembled compound can be anchored on the surface of the NiO x hole transport layer to form a strong and stable covalent bond, realize selective contact to reduce interface recombination and reduce the surface defects of the NiO x thin film, and the electron donor unit -C=N- in the imidazole group or pyrazole group at the other end can combine with the uncoordinated Pb 2+ in the perovskite light-absorbing layer, greatly reduce the vacancy defects in the perovskite light-absorbing layer, and finally realize the regulation of the interface defects at the bottom of the perovskite light-absorbing layer, thereby improving the photoelectric conversion efficiency of the battery. The perovskite solar cell treated based on the bifunctional organic self-assembled compound has excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The figure is a schematic structure of the perovskite solar cell of the present application Figure 1 ;

[0038] Figure 2 The figure is an XRD pattern of the perovskite thin film prepared in Comparative Example 1 and Example 1;

[0039] Figure 3 UV spectra of the perovskite films prepared in Comparative Example 1 and Example 1;

[0040] Figure 4 1 is the fluorescence spectra of the perovskite films prepared in Comparative Example 1 and Example 1;

[0041] Figure 5 Fluorescence lifetime spectra of the perovskite films prepared in Comparative Example 1 and Example 1;

[0042] Figure 6 The figure is a comparison chart of the stability of perovskite solar cells prepared in the embodiment and the comparative example. DETAILED DESCRIPTION

[0043] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0044] In view of the existing technology of NiO x The present application provides a perovskite solar cell which uses NiO to solve the defect problem at the interface between the hole transport layer and the perovskite light absorbing layer. x A self-assembled molecular layer is introduced between the hole transport layer and the perovskite light absorbing layer, wherein the organic self-assembled compound and NiO x The hole transport layer and the perovskite light absorbing layer greatly reduce the vacancy defects in the perovskite light absorbing layer, and finally realize the regulation of interface defects and improve the photoelectric conversion efficiency of the perovskite solar cell. Specifically, the present application first provides a perovskite solar cell, comprising: NiO x Hole transport layer, perovskite light absorbing layer and composite NiO x a self-assembled molecular layer between the hole transport layer and the perovskite light absorbing layer;

[0045] The self-assembled molecular layer includes an organic self-assembly compound, and the organic self-assembly compound is selected from one or more of the following compounds;

[0046]

[0047] wherein n is independently selected from integers between 1 and 10.

[0048] In the present invention, the NiO x The hole transport layer, self-assembled molecular layer and perovskite light absorption layer are key parts of perovskite solar cells, which play an important role in the photoelectric conversion efficiency of perovskite solar cells. x The hole transport layer serves as a transport layer and may have a thickness of 10 to 30 nm.

[0049] The self-assembled molecular layer comprises a bifunctional organic self-assembled compound with one end being phosphonic acid group, carboxylic acid group, mercapto group or boronic acid group and the other end being imidazole or pyrazole; wherein the phosphonic acid group, carboxylic acid group, mercapto group or boronic acid group is only used to anchor NiO x The organic self-assembled compound is prepared according to the method known to those skilled in the art, and as a preferred solution, the preparation method of the organic self-assembled compound A (n = 1) with one end being phosphonic acid group and the other end being imidazole group is specifically as follows:

[0050] 1) Imidazole and dibromomethane are subjected to alkylation reaction in the presence of KOH, water and tetrabutylammonium bromide, and after the reaction, the solution is naturally cooled to room temperature, and then subjected to water washing, dichloromethane extraction, anhydrous magnesium sulfate drying, and rotary evaporation to remove the solvent, and then subjected to silica gel column chromatography purification using a mixture of petroleum ether and dichloromethane (volume ratio 3:1) to obtain compound 2; wherein the molar ratio of imidazole to dibromomethane is 1:10-20; the molar ratio of tetrabutylammonium bromide to potassium hydroxide to imidazole in the mixed solution of tetrabutylammonium bromide, potassium hydroxide and water is 2:1 and 5:1 respectively, the mass concentration of potassium hydroxide in the mixed solution is 50%, the reaction temperature is 80°C, and the reaction time is 5-12h;

[0051] 2) 4.84mmol of compound 2 is dissolved in 2.48mL of triethyl phosphite, and the mixture is reacted at 150°C for 24h, and then the obtained crude product is added to a mixture of tetrahydrofuran and hexane (volume ratio 2:1) eluent, and the crude product is purified by silica gel column chromatography to obtain compound 3;

[0052] 3) 0.67mmol of compound 3 is dissolved in anhydrous 1,4-dioxane (10ml) under argon atmosphere, and then bromotrimethylsilane (1.43mL, 10.84mmol) is added dropwise, and stirred at 25°C for 2h, and then 10mL of methanol is added and stirred for another 3h, and finally distilled water (20mL) is added dropwise until the solution becomes opaque, and stirred overnight, and the precipitated product is filtered and washed with water to obtain compound 4. The reaction formula of the above reaction is specifically as follows:

[0053]

[0054] The preparation method of the organic self-assembled compound B (n = 1) with one end being carboxyl group and the other end being imidazole group specifically includes the following steps:

[0055] 1) Imidazole and dibromomethane were subjected to alkylation reaction in the presence of tetrabutylammonium bromide, KOH and water, and after the reaction was completed, the mixture was naturally cooled to room temperature, and then subjected to water washing, dichloromethane extraction, anhydrous magnesium sulfate drying, rotary evaporation to remove the solvent, and then column chromatography using a mixture of petroleum ether / dichloromethane (3:1 by volume) to obtain compound 2; in this step, the molar ratio of imidazole to dibromomethane was 1:10-20; the molar ratio of tetrabutylammonium bromide to imidazole in the mixed solution of tetrabutylammonium bromide, potassium hydroxide and water was 2:1 and 5:1, respectively; the mass concentration of potassium hydroxide in the mixed solution was 50%; the reaction temperature was 80°C; and the reaction time was 5-12h;

[0056] 2) 4mmol of compound 2 was dissolved in 10mL of DMSO and 6mmol of CuSCN was added, and the mixture was stirred at 40°C for 24h to obtain compound 3;

[0057] 3) A mixture of 6mmol of compound 3, 1.15mL of water and 0.84mL of concentrated sulfuric acid (98%) was heated (50°C) under reflux condenser for 3h, and then washed with hot water for three times to obtain compound 4 (compound B). The reaction formula of the above reaction is shown as follows:

[0058]

[0059] For example, the preparation method of an organic self-assembled compound C (n=1) having a thiol group at one end and an imidazole group at the other end specifically includes the following steps:

[0060] 1) Imidazole and dibromomethane were subjected to alkylation reaction in the presence of tetrabutylammonium bromide, KOH and water, and after the reaction was completed, the mixture was naturally cooled to room temperature, and then subjected to water washing, dichloromethane extraction, anhydrous magnesium sulfate drying, rotary evaporation to remove the solvent, and then column chromatography using a mixture of petroleum ether / dichloromethane (3:1 by volume) to obtain compound 2; in this step, the molar ratio of imidazole to dibromomethane was 1:10-20; the molar ratio of tetrabutylammonium bromide to imidazole in the mixed solution of tetrabutylammonium bromide, potassium hydroxide and water was 2:1 and 5:1, respectively; the mass concentration of potassium hydroxide in the mixed solution was 50%; the reaction temperature was 80°C; and the reaction time was 5-12h;

[0061] 2) 2.5mmol of compound 2 and 4mmol of NaHS were dissolved in 5mL of ethanol, and the mixture was continuously stirred at 50°C for 12h to obtain compound 3 (compound C); the reaction formula of the above reaction is shown as follows:

[0062]

[0063] The preparation method of the organic self-assembled compound D (n=1) with one end as a boronic acid group and the other end as an imidazole group specifically comprises the following steps:

[0064] 1) Imidazole and dibromomethane are subjected to alkylation reaction in the presence of tetrabutylammonium bromide, KOH and water, and after the reaction is completed, the reaction system is naturally cooled to room temperature, and then water washing, dichloromethane extraction, anhydrous magnesium sulfate drying, rotary evaporation to remove the solvent, and then silica gel column chromatography using a petroleum ether / dichloromethane mixture with a volume ratio of 3:1 are sequentially performed to purify compound 2; in this step, the molar ratio of imidazole to dibromomethane is 1:10-20; the molar ratio of tetrabutylammonium bromide to imidazole in the mixed solution of tetrabutylammonium bromide, potassium hydroxide and water is 2:1 and 5:1 respectively, the mass concentration of potassium hydroxide in the mixed solution is 50%, the reaction temperature is 80°C, and the reaction time is 5-12h;

[0065] 2) 100ml of dry tetrahydrofuran is taken, 10mmol of compound 2 and 12mmol of boron acid triisopropyl ester are added, and the reaction is carried out at minus 40°C for 30min, then 12mmol of n-butyllithium is added, the reaction is carried out for 2h, the temperature is raised to minus 20°C, 50ml of 6mol / L hydrochloric acid is added, the reaction is carried out for 24h, deionized water and sodium hydroxide are added to neutralize to pH 7, dichloromethane is added for extraction, the organic phase is dried with anhydrous magnesium sulfate, and the organic phase is rotary dried to obtain compound 3;

[0066] 3) 10mmol of compound 3 and 10mmol of methyl boronic acid are dissolved in 1mL of acetone, 1mL of NaOH solution (0.1N) is added, and stirring is carried out at room temperature for 24h; then 0.1N HCl solution is added dropwise until the pH of the solution is 7, the above reaction mixture is concentrated and dried, the product is washed with acetone and filtered to remove NaCl, and finally dried to obtain compound 4 (compound D); the reaction formula of the above reaction is specifically as follows:

[0067]

[0068] In the organic self-assembled layer of the present application, the thickness of the organic self-assembled compound is 1-5nm; n is more specifically 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0069] In the present application, the perovskite material of the perovskite light-absorbing layer has a general formula ABX3, wherein A is selected from one or more of CH3NH3 + (MA + ), CH(NH2)2 + (FA + ), Cs + and Rb + , B is selected from Pb 2+ , Sn 2+ and Ge2+ X is any one or more of Cl - , Br - , and I - . The perovskite material is a perovskite material well known to those skilled in the art, and the present application is not particularly limited thereto; for example, the perovskite material is CsPbI x Br 3-x , FA 0.95 MA 0.05 PbI3, FA 0.85 Cs 0.15 PbI3, or Rb 0.15 Cs 0.85 PbI 1.75 Br 1.25 . The thickness of the perovskite light-absorbing layer is 200 to 1000 nm, and specifically, the thickness of the perovskite light-absorbing layer is 400 to 800 nm.

[0070] Further, the present application also provides a perovskite solar cell, which comprises: a substrate, a NiO x hole transport layer, a self-assembled molecular layer, a perovskite light-absorbing layer, an electron transport layer, and an electrode layer, which are sequentially stacked in combination.

[0071] The self-assembled molecular layer comprises an organic self-assembled compound, and the organic self-assembled compound is selected from one or more of the following compounds:

[0072]

[0073] wherein n is independently selected from an integer between 1 and 10.

[0074] For the perovskite solar cell described above, from one direction, it comprises a substrate, a NiO x hole transport layer, a self-assembled molecular layer, a perovskite light-absorbing layer, an electron transport layer, and an electrode layer, which are sequentially stacked in combination, as shown in FIG. 1, wherein 1 is the substrate, 2 is the NiO x hole transport layer, 3 is the self-assembled molecular layer, 4 is the perovskite light-absorbing layer, 5 is the electron transport layer, and 6 is the electrode layer. Figure 1 The NiO x hole transport layer, the self-assembled molecular layer, and the perovskite light-absorbing layer have been described in detail above, and will not be described again here.

[0075]

[0076] ​In the present invention, the substrate is a material well known to those skilled in the art, and this application does not impose any particular restrictions on this. For example, the substrate is transparent conductive glass. The material of the electron transport layer can be an n-type inorganic semiconductor or an n-type organic semiconductor. More specifically, the material of the electron transport layer is selected from C 60 , PCBM, TiO2, BCP, SnO2, ZnO or ZnO-ZnS; its thickness is 10 to 30 nm, more specifically, the thickness of the electron transport layer is 12 to 28 nm. The surface of the electron transport layer can be further added with an electron transport layer as needed, which can also be called a hole blocking layer. The hole blocking layer can be an n-type inorganic semiconductor or an n-type organic semiconductor. The material of the hole blocking layer is selected from C 60 , PCBM, TiO2, BCP, SnO2, ZnO or ZnO-ZnS; more specifically, the hole blocking layer is made of BCP and / or SnO2; its thickness is 5 to 20 nm, more specifically, the hole blocking layer is 8 to 15 nm; the electron transport layer can be the same as or different from the electron transport layer on the surface of the perovskite light absorbing layer, and this application has no particular restrictions on this. Finally, an electrode layer is composited on the surface of the electron transport layer; the electrode material of the electrode layer is selected from one of Au, Ag and a low-temperature carbon electrode; the thickness of the electrode layer is 50 to 100 nm, more specifically, the thickness of the electrode layer is 80 to 100 nm.

[0077] The present application also provides a method for preparing a perovskite solar cell, comprising the following steps:

[0078] A) Preparation of NiO on the substrate surface x hole transport layer;

[0079] B) In the NiO x Preparation of a self-assembled molecular layer on the surface of the hole transport layer;

[0080] C) preparing a perovskite light-absorbing layer on the surface of the self-assembled molecular layer;

[0081] D) preparing an electron transport layer on the surface of the perovskite light absorbing layer;

[0082] E) preparing an electrode layer on the surface of the electron transport layer.

[0083] During the preparation process of perovskite solar cells, the present application first pre-treats the substrate, and the pre-treatment specifically involves cleaning the substrate to avoid the influence of impurity elements on the perovskite solar cell. Specifically, the cleaning is ultrasonic cleaning using detergent, deionized water, acetone and anhydrous ethanol in sequence.

[0084] According to the application, the NiO x The hole transport layer is prepared by mixing a nickel source and a solvent to obtain a precursor solution.

[0085] The precursor solution is spin-coated on the surface of the substrate, and annealed at 350-450°C for 30-50 min to obtain the NiO x The hole transport layer.

[0086] In the above process, the nickel source is specifically selected from Ni(OCOCH3)2·4H2O and / or Ni(NO3)2·6H2O, and the solvent is selected from one or more of anhydrous ethanol, water, and diethanolamine. The spin-coating method is performed in a manner known to those skilled in the art, and the present application does not make a special limitation thereon. In specific embodiments, the annealing temperature is 380-420°C, and the annealing time is 35-45 min.

[0087] According to the application, the perovskite light-absorbing layer is then prepared on the surface of the self-assembled molecular layer. x The self-assembled molecular layer is prepared on the surface of the hole transport layer by mixing an organic self-assembled compound and an organic solvent to obtain a mixed solution.

[0088] The mixed solution is spin-coated on the surface of the hole transport layer, and then annealed at 80-120°C for 10-30 min. After cleaning, the self-assembled molecular layer is obtained by annealing at 80-120°C for 1-5 min. x The self-assembled molecular layer is prepared on the surface of the hole transport layer by mixing an organic self-assembled compound and an organic solvent to obtain a mixed solution.

[0089] In the above process, the organic solvent is selected from isopropanol and / or ethanol, and the molar concentration of the organic self-assembled compound in the mixed solution is 1-5 mM, more specifically, 1-3 mM. The spin-coating method is not particularly limited in the present application, and in specific embodiments, the spin-coating time is 20-50 s. Specifically, the annealing temperature is 90-100°C, and the annealing time is 10-20 min. In order to remove the organic self-assembled compound that is not covalently bonded, the self-assembled molecular layer after annealing is cleaned with a solvent, and finally annealed at 80-120°C for 1-5 min to obtain the self-assembled molecular layer.

[0090] According to the application, the perovskite light-absorbing layer is then prepared on the surface of the self-assembled molecular layer.

[0091] The perovskite light-absorbing layer is obtained by spin-coating the perovskite precursor solution on the surface of the self-assembled molecular layer and annealing.

[0092] In the preparation process of the perovskite light-absorbing layer, the solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, gamma-butyrolactone, 1,3-dimethyl-2-imidazolidinone, dimethylacetamide, N,N-dimethylacrylurea, acetonitrile and 2-mercaptoethanol, and specifically, the solvent is selected from dimethyl sulfoxide and N,N-dimethylformamide; the concentration of the perovskite precursor solution is 1-5 M, and specifically, the concentration of the perovskite precursor solution is 1.5-3 M. The perovskite raw material is a source material for forming a perovskite material, which is obtained by subsequent annealing. The annealing temperature is 100-150 DEG C, and the annealing time is 10-30 min, and specifically, the annealing temperature is 120-140 DEG C, and the annealing time is 15-25 min.

[0093] According to the present application, then, an electron transport layer is deposited on the surface of the perovskite light-absorbing layer, and an electrode layer is prepared on the surface of the electron transport layer; or an electron transport layer is deposited on the surface of the perovskite light-absorbing layer, and then another electron transport layer is deposited on the surface of the electron transport layer, and an electrode layer is prepared on the surface of the electron transport layer; the electron transport layer is preferably prepared by vacuum evaporation, and the electrode layer is preferably prepared by PVD; the above-mentioned methods are well known to those skilled in the art, and the present application is not particularly limited in this regard.

[0094] The present application provides a kind of based on imidazole, pyrazole's bifunctional organic self-assembly compound in perovskite solar cell application, it can simultaneously passivate NiO x Hole transport layer and perovskite light-absorbing layer surface, reduce interface defect;Specifically, one end of the organic self-assembly compound contains anchor group can be anchored in NiO x Strong and stable covalent bond is formed on the surface of light-absorbing layer, selective contact is realized to reduce interface recombination and reduce NiO x Film surface defect;Meanwhile, the electron donor unit-C=N-in the other end imidazole group / pyrazole group can be coordinated with Pb 2+ Combine, greatly reduce the vacancy defect in perovskite light-absorbing layer, finally realize the regulation of perovskite film bottom interface defect, improve the photoelectric conversion efficiency of battery, based on the performance of perovskite solar cell treated by the bifunctional organic self-assembly monomer is excellent.

[0095] In order to further understand the present application, the perovskite solar cell and the preparation method thereof provided by the present application will be described in detail below in conjunction with examples, and the protection scope of the present application is not limited by the following examples.

[0096] Example 1

[0097] Step 1: cleaning the transparent conductive glass, specifically: sequentially using soapy water, deionized water, acetone and anhydrous ethanol for ultrasonic cleaning, and then blowing dry with a nitrogen gun; wherein the power of ultrasonic cleaning is 100 Hz, and the time of ultrasonic cleaning is 15 min;

[0098] Step 2: spin coating and depositing a hole transport layer on the surface of the conductive glass, specifically: mixing and stirring 125 mg of Ni(OCOCH3)2·4H2O, 5 mL of anhydrous ethanol and 30 μL of diethanolamine at room temperature for 2 h to prepare a precursor solution of NiO x , spin coating the solution on the conductive glass obtained in step 2) at a speed of 5000 rpm for 30 s, and then annealing at an annealing temperature of 400℃ for 40 min to form a NiO x hole transport layer;

[0099] Step 3: depositing a self-assembled molecular layer on the surface of the hole transport layer, specifically: dispersing the organic self-assembled compound A in isopropyl alcohol (IPA) and stirring at room temperature for 10 h to completely dissolve, and configuring a concentration of 1 mM; then spin coating 100 μL of the solution on the NiO x layer at 2000 rpm for 30 s, followed by annealing at 100℃ for 10 min; finally, spin coating the IPA solvent to remove excess organic self-assembled compounds not covalently bonded to the NiO x , and annealing at 100℃ for 1 min to obtain a self-assembled molecular layer;

[0100] Step 4: preparing a perovskite light absorption layer on the upper surface of the self-assembled molecular layer, specifically: dissolving CH3NH3I (MAI), CH(NH2)2I (FAI), CH3NH3Cl (MACl) and PbI2 in a mixed solvent composed of dimethyl sulfoxide (DMSO) and dimethylformamide (DMF), heating at 70℃ and continuously stirring for 1 hour to completely dissolve, to prepare a perovskite precursor solution; wherein the concentration ratio of FAI:MAI:MACl is 0.95:0.05:0.14, the concentrations of FAI and PbI2 are both 1.5 M (M is molar concentration, i.e. mol / L), and the volume ratio of dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) in the mixed solvent is 1:9;

[0101] The perovskite precursor solution is coated on the hole transport layer by spin coating, spin coating at a speed of 5000 rpm for 50 s, and finally annealing at 120℃ for 15 min to crystallize to form a FA 0.95 MA 0.05 PbI3perovskite light absorption layer with a thickness of about 450 nm;

[0102] Step 5: Deposit the electron transport layer C on the surface of the perovskite layer by vacuum evaporation 60 The evaporation is carried out at a vacuum degree of 5×10 -4 It was carried out in a Pa environment with an evaporation rate of 0.15 A / s and a thickness of approximately 20 nm;

[0103] Step 6: Deposit another layer of electron transport layer BCP on the surface of the electron transport layer by vacuum evaporation. The evaporation is carried out at a vacuum degree of 5×10 -4 It was carried out in a Pa environment with an evaporation rate of 0.2 A / s and a thickness of approximately 8 nm;

[0104] Step 7: A metal electrode is prepared on the upper surface of the electron transport layer obtained in step 6) by PVD, specifically: in a metal evaporation chamber, a silver electrode with a thickness of 80 nm to 100 nm is formed on the surface of the electron transport layer facing away from the perovskite light absorption layer by a thermal evaporation process to serve as the metal cathode; wherein the vacuum degree of the evaporation chamber is 5×10 -4 Pa, and the evaporation rate is 2A / s.

[0105] Example 2

[0106] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the self-assembly compound in step 3) is an organic self-assembly compound B, which is fully stirred and dissolved.

[0107] Example 3

[0108] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the self-assembly compound in step 3) is an organic self-assembly compound C, which is fully stirred and dissolved.

[0109] Example 4

[0110] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the self-assembly compound in step 3) is an organic self-assembly compound D, which is fully stirred and dissolved.

[0111] Example 5

[0112] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the self-assembly compound in step 3) is an organic self-assembly compound E, and is fully stirred and dissolved.

[0113] Example 6

[0114] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the self-assembly compound in step 3) is an organic self-assembly compound F, which is fully stirred and dissolved.

[0115] Example 7

[0116] The preparation method of this example is basically the same as that of Example 1, except that the self-assembled compound in step 3) is organic self-assembled compound G, which is fully stirred and dissolved.

[0117] Example 8

[0118] The preparation method of this example is basically the same as that of Example 1, except that the self-assembled compound in step 3) is organic self-assembled compound H, which is fully stirred and dissolved.

[0119] The structural formula of the organic self-assembled compounds A-H in the above examples is as follows, where n = 5;

[0120]

[0121] Comparative Example 1

[0122] The preparation method of this example is basically the same as that of Example 1, except that no self-assembled molecular layer is introduced in step 3), and the perovskite film is directly deposited on the surface of the NiO x layer.

[0123] Comparative Example 2

[0124] The preparation method of this example is basically the same as that of Example 1, except that the self-assembled compound in step 3) is organic self-assembled compound I, which is fully stirred and dissolved;

[0125] The synthesis method of organic self-assembled compound I is as follows: imidazole and 1-bromopentane undergo an alkylation reaction in the presence of tetrabutylammonium bromide, KOH and water, and after the reaction is completed, it is naturally cooled to room temperature, and then water washing, dichloromethane extraction, anhydrous magnesium sulfate drying, rotary evaporation to remove the solvent, and then using a mixture of petroleum ether / dichloromethane with a volume ratio of 3:1 for silica gel column chromatography purification are sequentially performed to obtain compound 2. In this step, the molar ratio of imidazole to dibromomethane is 1:10-20; the molar ratio of tetrabutylammonium bromide to potassium hydroxide to imidazole in the mixed solution of tetrabutylammonium bromide, potassium hydroxide and water is 2:1 and 5:1, respectively; the mass concentration of potassium hydroxide in the mixed solution is 50%; the reaction temperature is 80°C; and the reaction time is 5-12h.

[0126] The preparation method of this example is basically the same as that of Example 1, except that the self-assembled compound in step 3) is organic self-assembled compound J, which is fully stirred and dissolved;

[0127] The synthesis method of compound J is similar to that of compound I, except that imidazole is replaced by an equal amount of pyrazole.

[0128] The preparation method of this comparative example is basically the same as that of Example 1, except that: the self-assembly compound in step 3) is an organic self-assembly compound K, and is fully stirred and dissolved;

[0129] The synthesis method of compound K refers to the synthesis method of compound A, except that the imidazole in step 1) is replaced by an equal amount of tetrahydropyrrole and the dibromomethane is replaced by 1-bromopentane.

[0130]

[0131] NiO in Example 1 x The perovskite film formed by the layer, the self-assembled molecular layer and the perovskite light absorbing layer is the same as the NiO in Comparative Example 1. x The perovskite film formed by the layer, self-assembled molecular layer and perovskite light absorbing layer was subjected to XRD analysis, such as Figure 2 As shown, from Figure 2 It can be seen that the XRD diffraction peak positions of the perovskite films with and without self-assembled single molecules are the same, and there are no other impurity peaks, indicating that the organic self-assembled compounds have not entered the perovskite lattice; in addition, the relative height of the PbI2 diffraction peak in the perovskite film after modification with the organic self-assembled compounds is significantly reduced, further indicating that the electron donor unit -C=N- in imidazole and pyrazole can bind to the unbonded Pb on the perovskite surface. 2+ Combining, reducing lead defects and reducing non-radiative recombination.

[0132] NiO in Example 1 x The perovskite film formed by the layer, the self-assembled molecular layer and the perovskite light absorbing layer is the same as the NiO in Comparative Example 1. x UV spectroscopy analysis of perovskite films formed by the layer, self-assembled molecular layer and perovskite light absorbing layer, such as Figure 3 As shown, from Figure 3 It can be seen that the insertion of the self-assembled molecular layer causes a slight red shift in the ultraviolet absorption peak of the perovskite film, which indicates that the organic self-assembled compound effectively promotes the crystallization of the perovskite film, making the size of the final perovskite larger.

[0133] NiO in Example 1 x The perovskite film formed by the layer, the self-assembled molecular layer and the perovskite light absorbing layer is the same as the NiO in Comparative Example 1. x Fluorescence spectrum analysis of perovskite thin films formed by layer, self-assembled molecular layer and perovskite light absorbing layer, such as Figure 4 As shown, from Figure 4 It can be seen that when there is no self-assembled molecular layer on the surface of the perovskite light absorbing layer, it shows a very high PL intensity, and the insertion of the self-assembled molecular layer makes the perovskite light absorbing layer / NiO x The PL quenching at the hole transport layer interface is significantly enhanced; the quenching is believed to be from the perovskite layer to the NiOx The hole charge transfer of the layer reduces the radiative relaxation from the excited state to the ground state.

[0134] NiO in Example 1 x The perovskite thin film formed by the layer, self-assembled molecular layer and perovskite light absorbing layer and the NiO in Comparative Example 1 x The fluorescence lifetime spectrum of the perovskite film formed by the layer, self-assembled molecular layer and perovskite light absorbing layer is shown in Figure 2. Figure 5 As shown, from Figure 5 It can be seen that the average carrier lifetimes of the perovskite films with and without self-assembled molecular layer modification are 136ns and 277ns, respectively. The reduction in lifetime indicates that the introduction of self-assembled molecular layer effectively promotes the x Hole separation at the perovskite / perovskite interface.

[0135] The performance of the perovskite solar cells prepared in the examples and comparative examples was tested, and the test results are shown in Table 1.

[0136] Table 1 Performance parameter data of perovskite solar cells prepared in Examples and Comparative Examples

[0137] Serial number Voc (V) Jsc(mA / cm 2 )]]> FF (%) PCE (%) Example 1 1.20 25.2 77.9 23.5 Example 2 1.19 24.9 78.2 23.2 Example 3 1.18 24.9 78.6 23.1 Example 4 1.19 25.0 78.5 23.4 Example 5 1.21 25.1 78.0 23.7 Example 6 1.20 25.0 78.1 23.4 Example 7 1.20 25.1 77.7 23.4 Example 8 1.19 25.2 77.8 23.3 Comparative Example 1 1.13 23.9 75.9 20.5 Comparative Example 2 1.16 23.7 76.5 21.0 Comparative Example 3 1.17 23.2 76.8 20.8 Comparative Example 4 1.17 23.1 76.6 20.7

[0138] As shown in Table 1, the open circuit voltage, short circuit current, fill factor and photoelectric conversion efficiency of the perovskite thin film battery after adding the self-assembled molecular layer are significantly improved. The reason for the improvement in battery performance is that the anchoring group in the organic self-assembled compound structure is anchored on NiO x Strong and stable covalent bonds are formed on the surface of the film, achieving selective contact to reduce surface defects and promote charge transfer; the important reason for the increase in Voc is the formation of a more favorable energy level arrangement. x A large number of carriers accumulated at the interface of NiO / perovskite are highly selectively extracted through the self-assembled molecular layer, reducing non-radiative recombination at the interface. When there are only pyrazolyl or imidazole groups without anchoring groups (Comparative Examples 2 and 3) and only anchoring groups without imidazole or pyrazole (Comparative Example 4), the efficiency is slightly improved compared to the device without treatment (Comparative Example 1), but the device performance is still very different from that of other examples; this is mainly because Comparative Examples 2 and 3 only passivate the perovskite layer, while Comparative Example 4 only passivates the NiO x The defects of the layer are not as good as the double-sided passivation in other embodiments.

[0139] Figure 6 The stability curves of the perovskite solar cells prepared in the examples and comparative examples are shown in FIG. Figure 6It can be seen that the stability of the perovskite solar cell modified by the organic self-assembled compound can still maintain more than 90% of the initial value after 1000h, while the unmodified solar cell has a faster decay rate; the enhancement of the stability of the device can be attributed to the improvement of the crystallinity of the perovskite layer and the NiO x The reduction of defects in the thin film, the former improves the stability of the perovskite lattice, and the latter hinders the penetration of water and oxygen into the internal perovskite thin film, prevents the degradation of the perovskite thin film by the reaction of the perovskite precursor with the NiO x The reduction of defects in the thin film, the former improves the stability of the perovskite lattice, and the latter hinders the penetration of water and oxygen into the internal perovskite thin film, prevents the degradation of the perovskite thin film by the reaction of the perovskite precursor with the NiO

[0140] The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified, and these improvements and modifications also fall within the scope of the claims of the present application.

[0141] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A perovskite solar cell, comprising: NiO x a hole transport layer, a perovskite light absorbing layer and a self-assembled molecular layer between the hole transport layer and the perovskite light absorbing layer. x a hole transport layer, a perovskite light absorbing layer and a self-assembled molecular layer between the hole transport layer and the perovskite light absorbing layer. The self-assembled molecular layer comprises an organic self-assembled compound selected from one or more of the following compounds: wherein n is independently selected from an integer between 1 and 10.

2. The perovskite solar cell according to claim 1, characterized in that, The thickness of the self-assembled molecular layer is 1-5 nm; n is selected from 3-6. 3.The perovskite solar cell of claim 1, wherein, The general formula of the perovskite material of the perovskite light-absorbing layer is ABX3, wherein A is selected from one or more of CH3NH3 + , CH(NH2)2 + , Cs + , and Rb + , B is selected from one or more of Pb 2+ , Sn 2 + , and Ge 2+ , and X is one or more of Cl - , Br - , and I - ; and the thickness of the perovskite light-absorbing layer is 200-1000 nm.

4. A perovskite solar cell, characterized by, The self-assembled molecular layer comprises an organic self-assembled compound selected from one or more of the following compounds: The base, NiO, and the compound are sequentially stacked x A hole transport layer, a self-assembled molecular layer, a perovskite light absorption layer, an electron transport layer, and an electrode layer wherein n is independently selected from an integer between 1 and 10. The thickness of the self-assembled molecular layer is 1-5 nm; n is selected from 3-6.

5. The perovskite solar cell according to claim 4, characterized in that, 8. The method for preparing the perovskite solar cell according to any one of claims 4-7, comprising the following steps:

6. The perovskite solar cell according to claim 4, characterized in that, The perovskite material of the perovskite light-absorbing layer has a general formula of ABX3, wherein A is selected from one or more of CH3NH3 + , CH(NH2)2 + , Cs + , and Rb + , B is selected from one or more of Pb 2+ , Sn 2+ , and Ge 2+ , and X is any one or more of Cl - , Br - , and I - ; and the perovskite light-absorbing layer has a thickness of 200-1000 nm.

7. The perovskite solar cell according to claim 4, characterized in that, The material of the electron transport layer is selected from one or more of C 60 , PCBM, Ti02, BCP, Sn02, ZnO or ZnO-ZnS; the material of the electrode layer is selected from one of Au, Ag and low temperature carbon electrode. C) preparing a perovskite light-absorbing layer on the surface of the self-assembled molecular layer; A) Preparation of NiO on the surface of the substrate x Hole transport layer; B) in the NiO x The surface of the hole transport layer is prepared with a self-assembled molecular layer; D) preparing an electron transport layer on the surface of the perovskite light-absorbing layer; E) preparing an electrode layer on the surface of the electron transport layer. The method for preparing the self-assembled molecular layer comprises:

9. The production method according to claim 8, characterized by, mixing the organic self-assembled compound and the organic solvent to obtain a mixed solution; The organic solvent is selected from isopropyl alcohol and / or ethanol; the molar concentration of the organic self-assembled compound in the mixed solution is 1-5 mM. The mixed solution is spin-coated on a NiO x The surface of the hole transport layer is annealed at 80-120°C for 10-30 min, and after cleaning, the surface is again annealed at 80-120°C for 1-5 min to obtain a self-assembled molecular layer. mixing the nickel source and the solvent to obtain a precursor solution; 10. The preparation method according to claim 8, characterized in that The NiO x The preparation method of the hole transport layer is specifically as follows: The method for preparing the perovskite light-absorbing layer comprises: The precursor solution is spin-coated on the surface of a substrate, annealed at 350-450°C for 30-50 min to obtain NiO x Hole transport layer.

11. The method of claim 6, wherein, mixing the perovskite raw material and the solvent, and heating to obtain a perovskite precursor solution; spin-coating the perovskite precursor solution on the surface of the self-assembled molecular layer, and annealing to obtain the perovskite light-absorbing layer; The solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, gamma-butyrolactone, 1,3-dimethyl-2-imidazolidinone, dimethylacetamide, N,N-dimethylacrylurea, acetonitrile and 2-mercaptoethanol; the concentration of the perovskite precursor solution is 1-5 M. ​

Images