NiOx nanoparticle and preparation method thereof, hole transport layer, trans-perovskite solar cell and preparation method thereof

Abstract

The invention belongs to the technical field of perovskite solar cell material development, and aims to solve the technical problems that impurity ions need to be removed at a high temperature when a hole transport layer is prepared and the device efficiency is affected due to the fact that NO3 <-> residues generated during preparation of NiOx nanoparticles in the prior art are difficult to completely remove. The invention provides NiOx nanoparticles and a preparation method thereof, a hole transport layer, a trans-perovskite solar cell and a preparation method thereof, the NiOx nanoparticles are prepared by adding imidazole ionic liquid (RMImIL) into nickel nitrate hexahydrate, [RMIm] < + > cations are adsorbed on the surfaces of the NiOx nanoparticles, adsorption of other impurity ions is inhibited, and the high-purity NiOx nanoparticles are obtained; the NiOx nanoparticles serve as the hole transport layer, so that the defects are greatly passivated, the quality of the perovskite thin film is improved, the NiOx hole transport layer is prepared through low-temperature annealing, and the photoelectric property and the stability of the perovskite solar cell are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite solar cell material development and relates to a NiO x Nanoparticles and preparation methods thereof, hole transport layers, inverse perovskite solar cells and preparation methods thereof. Background Art

[0002] Perovskite solar cells (PSCs) have a power conversion efficiency (PCE) of more than 26%, which makes commercialization possible. For practical applications, photovoltaic devices need to have not only high efficiency, but also long-term stability and large-area scalability. The main key to achieving scalable and stable perovskite solar modules (PSMs) is to have a large-area, conformal, compact charge transport layer and a compact, pinhole-free perovskite film. At present, the structure of perovskite solar cells is mainly divided into two types: formal (nip) perovskite solar cells and inverted (pin) perovskite solar cells. Compared with nip devices, pin PSCs have higher operational stability, but still lag behind in PCE. The energy loss of insufficient PCE in pin PSCs mainly occurs at the interface between the perovskite layer and the hole transport layer. Therefore, passivating the defects at the interface between the perovskite layer and the hole transport layer and improving the transport performance of the hole transport layer are crucial to the preparation of efficient and stable perovskite solar cells. At present, various organic hole transport materials (HTMs) have been used to prepare hole transport layers, especially poly (3.4-ethylenedioxythiophene): poly (benzenesulfonic acid) (PEDOT:PSS) and poly (bis (4-phenyl) (2.4,6-trimethylphenyl) amine) (PTAA). However, when using the above hole transport materials to prepare hole transport layers, the preparation process is complicated, the inherent chemical solvent volatilization is easy to produce during the process, the stability is poor, and the cost is high, which greatly hinders large-scale commercial application. Among various hole transport layers and solar cell device structures, nickel oxide (NiO x ) is considered to be a very promising hole transport material in perovskite solar cells because of its high hole mobility, good chemical and thermal stability, and low-temperature preparation.

[0003] Currently, NiO as a hole transport layer xMost of the nanoparticles are prepared by a simple two-step method at low temperature. The main steps are to first prepare nickel hydroxide (Ni(OH)2) by reacting Ni(NO3)2·6H2O with NaOH, and then calcine Ni(OH)2 to obtain NiO x Nanoparticles, and then NiO x The nanoparticles are spin-coated or scraped onto a fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) conductive film substrate to form a hole transport layer.

[0004] However, the NiO obtained by the conventional two-step process x Nanoparticles produce NO3 during the synthesis process - ions, and subsequent treatment cannot completely remove them, and the NO3 - The ions are embedded in the Ni(OH)2 layer, resulting in NiO x There are many impurity ions in the layer, so high temperature annealing must be used to remove these impurity ions when preparing the hole transport layer in the subsequent process. When high temperature annealing is used to remove impurity ions, NiO x The sintering and agglomeration of nanoparticles affects the quality of the film, which in turn affects the efficiency and long-term stability of the device. In addition, although these impurity ions can be removed by high temperature in the subsequent device preparation process, the NiO prepared by the traditional synthesis method x Nanoparticles lead to the formation of NiO x The poor dispersion of nanoparticles in the dispersion solution seriously affects the quality of the subsequent dispersion solution spin coating to prepare the hole transport layer, resulting in poor photoelectric performance and photothermal stability of the final device. The Chinese patent application with publication number CN117979781A discloses a preparation method and application of a hole transport layer containing functionalized nickel oxide, a trans-perovskite solar cell and a preparation method thereof. The method obtains functionalized nickel oxide nanoparticles by surface hydroxylation of nickel oxide nanoparticles, thereby improving the wettability of the perovskite layer. However, the preparation of nickel oxide nanoparticles still uses the traditional Ni(NO3)2·6H2O and NaOH hydrothermal and calcination method, which cannot avoid NO3 - Residual issues. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a NiO x Nanoparticles and preparation methods thereof, hole transport layers, inverse perovskite solar cells and preparation methods thereof, thereby solving the problems in the prior art in preparing NiO x NO3 produced during the nanoparticle process - The residual impurity ions are difficult to completely remove, which leads to the use of NiOx Preparation of NiO Nanoparticles x The hole transport layer needs high temperature annealing to remove impurity ions and make NiO x The sintering and agglomeration of nanoparticles reduces the quality of the film, which in turn leads to a technical problem of reduced device efficiency.

[0006] The present invention is achieved through the following technical solutions: A NiO x The method for preparing nanoparticles comprises the following steps: S1: dissolving nickel nitrate hexahydrate and imidazole ionic liquid in water in molar ratio, stirring evenly, adjusting the pH value of the solution system to 9-11, stirring and reacting until the solution becomes turbid, and obtaining Ni(OH)2-RMImIL precipitate; S2: After the Ni(OH)2-RMImIL precipitate is dried, it is calcined at 270-330°C for 1-3h to obtain NiO x Nanoparticles; In step S1, the structural formula of the imidazole ionic liquid is:

[0007] Wherein, R1 is any one of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl; R2 is any one of methyl, ethyl, propyl, butyl and pentyl; X - It is any one of chloride, bromide, iodide, tetrafluoroborate, hexafluorophosphate, acetate, bis(trifluoromethanesulfonyl)imide, nitrate, perchlorate, hydrogen sulfate, dihydrogen phosphate, trifluoromethanesulfonate, trifluoroacetate and p-toluenesulfonate.

[0008] In a more preferred embodiment, the pH value of the solution system is adjusted to 10, the preferred calcination temperature is 270° C., and the calcination time is 2 h.

[0009] The chemical mechanism of the reaction in the preparation method is mainly the following equation: Ni(NO3)2+2NaOH+RMImIL → Ni(OH)2-RMImIL↓+2NaNO3 Ni(OH)2-RMImILL → NiO x -RMImIL+H2O (calcined at 270~330℃).

[0010] Furthermore, in step S1, the molar ratio of the nickel nitrate hexahydrate to the imidazole ionic liquid is 1:(0.05-0.2). In a more preferred embodiment, the molar ratio of the nickel nitrate hexahydrate to the imidazole ionic liquid is 1:0.1.

[0011] Furthermore, in step S1, after stirring the reaction until the solution becomes turbid, the reaction system is centrifuged to obtain the Ni(OH)2-RMImIL precipitate; during the centrifugation, the rotation speed is 800-3000 rpm and the centrifugation time is 10-20 min. In a more preferred embodiment, during the centrifugation, the rotation speed is 3000 rpm and the centrifugation time is 10 min.

[0012] Furthermore, in step S2, the drying temperature is 80-100°C and the drying time is 8-16 hours. In a more preferred embodiment, the drying temperature is 80°C and the drying time is 8 hours.

[0013] Furthermore, the structure of the imidazole ionic liquid is preferably: R1 is a methyl group; R2 is an ethyl group; X - For chloride ion.

[0014] The present invention also provides a NiO x Nanoparticles, the NiO x The nanoparticles are prepared by the above-mentioned preparation method; NiO x The average size of nanoparticles is 5~10nm.

[0015] At the same time, the present invention also provides a hole transport layer, the hole transport layer is made of the above-mentioned NiO x Nanoparticles are made of materials.

[0016] Furthermore, the thickness of the hole transport layer is 15-20 nm.

[0017] In addition, the present invention also provides an inverted perovskite solar cell, comprising a transparent conductive layer, a hole transport layer, a perovskite active layer, an electron transport layer, a cathode buffer layer and a back electrode stacked from bottom to top, wherein the hole transport layer adopts the above-mentioned hole transport layer.

[0018] Finally, the present invention also provides a method for preparing an inverse perovskite solar cell, comprising the following steps: Step 1: Add the above NiO x The nanoparticles are dispersed in a dispersion according to the required concentration, and the dispersion is coated on the pre-treated transparent conductive layer by blade coating or spin coating. After annealing at 80-120° C. for 10-30 min, a hole transport layer of the required thickness is formed on the transparent conductive layer. Step 2: Prepare a perovskite active layer, an electron transport layer, a cathode buffer layer and a back electrode in sequence on the hole transport layer to obtain an inverse perovskite solar cell.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: 1. NiO of the present invention x Nanoparticles and preparation method thereof, by x Nanoparticles are doped with imidazolium ionic liquids to make [RMIm] + Cations adsorbed on NiO x The surface of nanoparticles inhibits the adsorption of other impurity ions, effectively solving the problem of NO3 - The problem of residual impurity ions being difficult to completely remove, thus avoiding the preparation of NiO x The nanoparticle hole transport layer needs high temperature annealing to reduce the quality of the perovskite film; at the same time, the NiO prepared by the method of the present invention x Nanoparticles have the advantages of small size (less than 10nm, much smaller than the 200-400nm prepared in the traditional way) and uniform dispersion in the dispersion liquid, which is conducive to forming a more compact and uniform hole transport layer; in addition, the NiO prepared by the present invention x Nanoparticles have better electrical conductivity. Figure 2 The test results show that the conductivity is more than 2 times higher than that of traditional methods.

[0020] 2. The present invention provides an inverted perovskite solar cell and a preparation method thereof, wherein the hole transport layer in the cell is made of high-purity NiO prepared by the present invention. x Nanoparticles, no need to consider NO3 - The problem of residual impurity ions is solved. Therefore, in the preparation process of the hole transport layer, low-temperature annealing at 80~120℃ is used, which solves the problem of residual impurity ions in the traditional preparation of NiO x The nano hole transport layer must be annealed at high temperature (above 150°C) to remove the impurity ions, thus avoiding the NiO x Nanoparticles agglomerate due to high temperature sintering, which reduces the film quality and affects the device efficiency and long-term stability. At the same time, through device performance test comparison, the open circuit voltage V oc Value, short circuit current J sc The value and filling factor FF value are significantly improved compared with the control ratio.

[0021] 3. NiO of the present invention x The imidazole ionic liquid structure provided in the preparation method of the nanoparticles can be adjusted by combining alkyl chains of different lengths and different anions to adjust the imidazole ionic liquid to NiO x The wettability of nanoparticles and the influence on the growth rate and direction of perovskite grains by regulating the steric hindrance effect help to form more uniform grains, thereby obtaining better perovskite film quality.

[0022] 4. NiO of the present invention xThe raw material molar ratio in the preparation method of nanoparticles is reasonably designed. Within this molar ratio range, the imidazole ionic liquid can be moderately adsorbed on NiO x A uniform and dense covering layer is formed on the surface of the nanoparticles, which is neither too dense to interfere with the interaction between the ionic liquids, nor too sparse to result in poor adsorption and covering function.

[0023] 5. The present invention also discloses a hole transport layer, wherein the hole transport layer is made of NiO x The nanoparticles are made of materials, and the resulting hole transport layer is dense and uniform, with fewer defects and pores. Its surface defects and grain boundaries are effectively passivated, thereby enhancing the conductivity of the film, reducing the recombination and leakage of charges, and effectively improving the photoelectric conversion efficiency of perovskite solar cells. The thickness of the hole transport layer is controlled to be 15~20nm, which will not excessively block the incident light, thereby ensuring that the perovskite layer can fully absorb and utilize light energy; at the same time, the thinner hole transport layer helps to reduce charge recombination and leakage at the interface, thereby reducing the degradation rate of the device and improving the stability and service life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 The schematic diagram of the structure of the inverted perovskite solar cell of the present invention is shown in FIG. 1 , wherein, from bottom to top, there are stacked transparent conductive layer, hole transport layer, perovskite active layer, electron transport layer, cathode buffer layer and back electrode. Figure 1 The preferred specific materials in each layer except the perovskite active layer are also shown; Figure 2 EMImCl-doped NiO prepared in Example 1 of the present invention x Nanoparticles and undoped NiO prepared in the comparative example x Comparison of conductivity of nanoparticles; Figure 3 EMImCl-doped NiO prepared in Example 1 of the present invention x Nanoparticles and undoped NiO prepared in the comparative example x Comparison of X-ray diffraction (XRD) patterns of nanoparticles; Figure 4 EMImCl-doped NiO prepared in Example 1 of the present invention xTransmission electron microscopy (TEM) images of nanoparticles; Figure 5 The EMImCl-doped NiO prepared in Example 1 of the present invention x Nanoparticles and undoped NiO prepared using Comparative Example 1 x Nanoparticles were prepared into NiO x Water contact angle diagram of the layer; Figure 6 The EMImCl-doped NiO prepared in Example 1 of the present invention x The perovskite film prepared by nanoparticles is similar to the undoped NiO in the comparative example. x Comparison of the surface and cross-sectional SEM images of the perovskite film prepared by nanoparticles, where the top two images are the surface SEM images, and the bottom two images are the cross-sectional SEM images; Figure 7 The EMImCl-doped NiO prepared in Example 1 of the present invention x The XRD spectrum of the perovskite film prepared by nanoparticles is similar to that of the undoped NiO in the comparative example. x Comparison of XRD patterns of perovskite films prepared by nanoparticle layer; Figure 8 It is a comparison diagram of the JV curves of the EMImCl-doped inverse perovskite solar cell prepared by Preparation Example 1 of the present invention and the undoped inverse perovskite solar cell prepared by the comparative example. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0028] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0029] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0030] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0031] The invention discloses a NiO x Nanoparticles and preparation methods thereof, hole transport layers, inverse perovskite solar cells and preparation methods thereof, the present invention will be described in detail below through specific embodiments and preparation examples.

[0032] It should be understood that these embodiments and preparation examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application. Conventional instruments and equipment in the art are used in the following examples and preparation examples. The experimental methods for which specific conditions are not indicated in the following examples and preparation examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer. Various raw materials are used in the following examples, and unless otherwise specified, conventional commercial products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples and preparation examples, if not otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0033] First, the present invention discloses a NiO x Nanoparticles, the NiO x The nanoparticles are made of conventional NiO x In situ functionalized NiO was formed by introducing imidazolium ionic liquid into the nanoparticles x Nanoparticles, specific reaction mechanism and preparation method are described in detail in the preparation method of the second part.

[0034] Second, the NiO x The method for preparing nanoparticles comprises the following steps: S1: Dissolve Ni(NO3)2·6H2O and imidazole ionic liquid (RMImIL) in ultrapure water and stir evenly, then drop NaOH solution to adjust the pH value to 9-11, preferably 10, at which point the solution becomes turbid to obtain Ni(OH)2-RMImIL precipitate. Then, place the Ni(OH)2-RMImILL precipitate in a centrifuge and centrifuge for 10-20 minutes, preferably 10 minutes, at a speed of 800-3000 rpm; then, drop ultrapure water and centrifuge for 3 cycles to obtain a precipitate product after centrifugation.

[0035] The molar ratio of Ni(NO3)2·6H2O to imidazolium ionic liquid (RMImIL) is 1:(0.05~0.2), and the molar ratio is preferably 10:1. The molar ratio of the raw materials is reasonably designed. Within this molar ratio range, the imidazolium ionic liquid can be moderately adsorbed on NiO x A uniform and dense covering layer is formed on the surface of the nanoparticles. The adsorbed ions between the formed covering layers are neither too dense to interfere with the interaction between the ionic liquids, nor too sparse to cause poor adsorption and covering effects. The reaction equation in this process is: Ni(NO3)2+2NaOH+RMImIL → Ni(OH)2-RMImIL↓+2NaNO3 S2: The precipitated product is dried in a vacuum drying oven for 8-16 hours, preferably 8 hours, at an oven temperature of 80-100°C, preferably 80°C, to obtain a dried product. The dried product is then calcined at 270-330°C for 1-3 hours, preferably at 270°C, and preferably for 2 hours, to obtain high-quality in-situ functionalized NiOx nanoparticles (NiO x -RMImIL). The drying temperature is 80~100℃ and the time is 8~16h. Under this drying condition, the residual solvent or water in the product can be effectively removed to ensure the dryness of the product, avoiding the performance degradation or stability problems caused by the residue. Moreover, this condition will not cause the product structure to be destroyed or decomposed, ensuring the stability of the product. The reaction mode in this process is: Ni(OH)2-RMImILL → NiO x -RMImIL+H2O (calcined at 270~330℃) The structural formula of the above-mentioned imidazolium ionic liquid (RMImIL) is as follows:

[0036] Wherein, R1 is any one of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl, R2 is any one of methyl, ethyl, propyl, butyl and pentyl; anion X- is any one of chloride, bromide, iodide, tetrafluoroborate, hexafluorophosphate, acetate, bis(trifluoromethanesulfonyl)imide, nitrate, perchlorate, hydrogen sulfate, dihydrogen phosphate, trifluoromethanesulfonate, trifluoroacetate and p-toluenesulfonate. In a more preferred embodiment, R1 is methyl, R2 is ethyl, X - The preferred imidazolium ionic liquid is 1-ethyl-3-methylimidazole chloride (EMImCl).

[0037] First, the selection of alkyl groups in R1 can increase the affinity of imidazolium ionic liquids with NiO x The interaction area of ​​the nanoparticle surface improves the adsorption stability, which helps to maintain NiO during preparation and application. x Functionalization effect of nanoparticles; in addition, by selecting alkyl chains of different lengths, the effect of imidazolium ionic liquids on NiO can be regulated. x The influence of nanoparticle wettability, this balance helps to optimize the perovskite solution in NiO x The spreading and penetration on the substrate improves the solute molecules in the perovskite solution in NiO x The long-chain alkyl group can affect the growth rate and direction of the perovskite grains through the steric hindrance effect, which helps to form more uniform grains and thus obtain better perovskite film quality. Secondly, the anion can passivate the defects on the nickel oxide side. The present invention provides a variety of different types of anions X - , for passivation NiO x The defects on the side provide a variety of options. Different anions have different chemical properties and charge distributions and can react with NiO x The defect sites on the surface form strong interactions, which effectively passivates these defects and improves the photoelectric conversion efficiency; at the same time, the presence of anions can affect the bonding between imidazolium ionic liquids and NiO x The interaction of nanoparticle surfaces changes the NiO x In addition, the anions in the imidazole ionic liquid will also affect the crystallization process of the perovskite, and by interacting with the cations in the perovskite, the growth rate and direction of the perovskite grains can be regulated by selecting different anions, which is beneficial to promote the growth of the perovskite grains and improve the efficiency and stability of the perovskite solar cell. On the basis of the above, the present invention provides a preferred imidazole ionic liquid structure, wherein R1 is methyl, R2 is ethyl, and X - The nitrogen atom and electron-donating alkyl chain in the imidazolium cation contained in the imidazolium ionic liquid can passivate the uncoordinated Pb 2+These ionic bonds can passivate the defects on the perovskite surface and inhibit carrier recombination at the interface, while chloride ions can passivate the defects on the nickel oxide side, effectively improving the photovoltaic performance of the device.

[0038] The preparation method of the present invention adds imidazole ionic liquid (RMImIL) to Ni(NO3)2·6H2O. First, [RMIm] + NO3 - The impurity ion has a lower adsorption energy, then [RMIm] + Cations are more easily adsorbed on NiO x The surface of the nanoparticles; secondly, the imidazole ionic liquids interact with NiO through strong hydrogen bonds x The strong interaction between the nanoparticles and the surface helps stabilize NiO x The surface structure of nanoparticles can also inhibit the adsorption of other impurity ions, effectively avoiding NO3 - The residual impurity ions; In addition, NiO x The surface of nanoparticles is the main active area for redox reactions. + The doping of cations effectively covers and shields the original redox active sites.

[0039] In step S1, when preparing Ni(OH)2-RMImIL, the pH value of the solution system is adjusted to 9-11, so that nickel ions can effectively generate nickel hydroxide precipitation. At the same time, when the prepared Ni(OH)2-RMImIL is calcined in step S2, the calcination temperature is 270-330°C and the time is 1-3h. Calcination within this temperature range can effectively promote the decomposition and recrystallization process of the precursor to form NiO with smaller size. x Nanoparticles, small particle size helps to increase the specific surface area, which is conducive to the uniform dispersion of particles in the matrix; in addition, the calcination temperature and time provided by the present invention can ensure the uniform growth of particles, avoid significant differences between large particles and small particles, and the uniform particle size distribution helps to improve the overall performance and stability of the product; under this calcination condition, NiO x Nanoparticles can form a crystalline structure that is more conducive to conductivity, thereby improving its conductivity. Good conductivity is NiO xImportant performance indicators of nanoparticles in the fields of electronic devices, sensors, batteries, etc. After stirring the reaction until the solution becomes turbid, the reaction system is centrifuged to obtain Ni(OH)2-RMImIL. During the centrifugal treatment, the speed is 800~3000rpm and the centrifugal time is 10~20min. Under this centrifugal condition, Ni(OH)2-RMImIL nanoparticles can be fully separated from other components in the reaction solution, such as unreacted raw materials, solvents, by-products, etc. Through efficient centrifugal separation, impurities can be removed to the maximum extent, thereby improving the purity of Ni(OH)2-RMImIL nanoparticles; at the same time, appropriate centrifugal speed and time can prevent Ni(OH)2-RMImIL nanoparticles from agglomerating during the centrifugation process, affecting its performance.

[0040] The above NiO of the present invention is described below through a number of specific embodiments. x The preparation method of nanoparticles is described in more detail.

[0041] Example 1 A NiO x The method for preparing nanoparticles comprises the following steps: S1: Dissolve Ni(NO3)2·6H2O and 1-ethyl-3-methylimidazole chloride (EMImCl) in ultrapure water and stir evenly, add NaOH solution to adjust the pH value to 10, stir and react, the solution becomes turbid to obtain Ni(OH)2-EMImCl precipitate; (the molar ratio of Ni(NO3)2·6H2O and EMImCl is 10:1.

[0042] The Ni(OH)2-EMImCl precipitate was then placed in a centrifuge and centrifuged at 3000 rpm for 10 min. Ultrapure water was then added and centrifuged three times to obtain a precipitate product after centrifugation.

[0043] S2: The precipitated product after centrifugation was dried in a vacuum drying oven for 8 hours at 80°C to obtain a dry product. The dry product was then calcined at 270°C for 2 hours to obtain high-quality NiO doped with 1-ethyl-3-methylimidazolium chloride ionic liquid. x Nanoparticles (NiO x -EMImCl), the 1-ethyl-3-methylimidazolium chloride ionic liquid doped NiO x The average particle size of the nanoparticles is 5 nm.

[0044] Example 2 The difference from Example 1 is: In S1, Ni(NO3)2·6H2O and 1-ethyl-3-methylimidazole chloride (EMImCl) were dissolved in ultrapure water and stirred evenly, and NaOH solution was added dropwise to adjust the pH value to 9. After stirring, the solution became turbid to obtain Ni(OH)2-EMImCl precipitate; (the molar ratio of Ni(NO3)2·6H2O and EMImCl was 10:1.

[0045] Then the Ni(OH)2-EMImCl precipitate was placed in a centrifuge and centrifuged at 2000 rpm for 12 min.

[0046] The NiO doped with 1-ethyl-3-methylimidazolium chloride ionic liquid obtained in this embodiment x The average particle size of the nanoparticles is 6 nm.

[0047] Example 3 The difference from Example 1 is: In S1, Ni(NO3)2·6H2O and 1-ethyl-3-methylimidazole chloride (EMImCl) were dissolved in ultrapure water and stirred evenly, and NaOH solution was added dropwise to adjust the pH value to 11. After stirring for reaction, the solution became turbid to obtain Ni(OH)2-EMImCl precipitate; (the molar ratio of Ni(NO3)2·6H2O and EMImCl was 10:1. Then, the Ni(OH)2-EMImCl precipitate was placed in a centrifuge and centrifuged at a speed of 1000 rpm for 15 min.

[0048] The NiO doped with 1-ethyl-3-methylimidazolium chloride ionic liquid obtained in this embodiment x The average particle size of the nanoparticles is 7 nm.

[0049] Example 4 The difference from Example 1 is: In S1, Ni(NO3)2·6H2O and 1-ethyl-3-methylimidazole chloride (EMImCl) were dissolved in ultrapure water and stirred evenly, and NaOH solution was added dropwise to adjust the pH value to 9. After stirring, the solution became turbid to obtain Ni(OH)2-EMImCl precipitate; (the molar ratio of Ni(NO3)2·6H2O and EMImCl was 5:1.

[0050] Then the Ni(OH)2-EMImCl precipitate was placed in a centrifuge and centrifuged at 800 rpm for 20 min.

[0051] The NiO doped with 1-ethyl-3-methylimidazolium chloride ionic liquid obtained in this embodiment x The average particle size of the nanoparticles is 8 nm.

[0052] Example 5 The difference from Example 1 is: In S1, Ni(NO3)2·6H2O and 1-ethyl-3-methylimidazolium chloride (EMImCl) are dissolved in ultrapure water and stirred evenly, and NaOH solution is added dropwise to adjust the pH value to 9, and the reaction is stirred until the solution becomes turbid to obtain Ni(OH)2-EMImCl precipitate; (the molar ratio of Ni(NO3)2·6H2O and EMImCl is 4:1, and the NiO doped with 1-ethyl-3-methylimidazolium chloride ionic liquid finally prepared in this embodiment x The average particle size of the nanoparticles is 9 nm.

[0053] Example 6 The difference from Example 1 is: In S2, the precipitated product after centrifugation is dried in a vacuum drying oven for 8 hours at a temperature of 100°C to obtain a dry product. The dry product is then calcined at 270°C for 2 hours to obtain high-quality NiO containing 1-ethyl-3-methylimidazolium chloride ionic liquid. x Nanoparticles (NiO x -EMImCl), the NiO doped with 1-ethyl-3-methylimidazolium chloride ionic liquid finally prepared in this embodiment x The average particle size of the nanoparticles is 10 nm.

[0054] Example 7 The difference from Example 1 is: In S2, the precipitated product after centrifugation is dried in a vacuum drying oven for 8 hours at a temperature of 80°C to obtain a dry product. The dry product is then calcined at 330°C for 3 hours to obtain high-quality NiO containing 1-ethyl-3-methylimidazolium chloride ionic liquid. x Nanoparticles (NiO x -EMImCl), the NiO doped with 1-ethyl-3-methylimidazolium chloride ionic liquid finally prepared in this embodiment x The average particle size of the nanoparticles is 8 nm.

[0055] Example 8 A NiO x The method for preparing nanoparticles comprises the following steps: S1: Dissolve Ni(NO3)2·6H2O and imidazole ionic liquid (RMImIL) in ultrapure water and stir evenly, add NaOH solution to adjust the pH to 9, stir and react, the solution becomes turbid, and Ni(OH)2-RMImIL precipitate is obtained; (The molar ratio of Ni(NO3)2·6H2O and imidazole ionic liquid (RMImIL) is 1:0.05.

[0056] Then the Ni(OH)2-RMImILL precipitate was placed in a centrifuge and centrifuged at 3000 rpm for 10 minutes. Then, ultrapure water was added and centrifuged three times to obtain a precipitate product after centrifugation.

[0057] S2: The centrifuged precipitate is dried in a vacuum drying oven for 8 hours at a temperature of 100°C to obtain a dry product. The dried product is then calcined at 270°C for 1 hour to obtain high-quality NiO containing imidazole ionic liquid. x Nanoparticles (NiO x -RMImIL), the NiO containing imidazole ionic liquid finally prepared in this embodiment x The average particle size of the nanoparticles is 10 nm.

[0058] The imidazolium ionic liquid of Example 8 has the structural formula (RMImIL) as follows:

[0059] Among them, R1 is propyl, R2 is methyl, and the anion X - It is a bromide ion.

[0060] Example 9 A NiO x The method for preparing nanoparticles comprises the following steps: S1: Dissolve Ni(NO3)2·6H2O and imidazole ionic liquid (RMImIL) in ultrapure water and stir evenly, add NaOH solution to adjust the pH to 11, stir and react, the solution becomes turbid, and Ni(OH)2-RMImIL precipitate is obtained; (The molar ratio of Ni(NO3)2·6H2O and imidazole ionic liquid (RMImIL) is 1:0.2.

[0061] Then the Ni(OH)2-RMImILL precipitate was placed in a centrifuge and centrifuged at 800 rpm for 20 minutes. Then, ultrapure water was added and centrifuged three times to obtain a precipitate product after centrifugation.

[0062] S2: The precipitated product after centrifugation is dried in a vacuum drying oven for 16 hours at a temperature of 100°C to obtain a dry product. The dry product is then calcined at 330°C for 2 hours to obtain high-quality NiO containing imidazole ionic liquid. x Nanoparticles (NiO x -RMImIL), the NiO containing imidazole ionic liquid finally prepared in this embodiment x The average particle size of the nanoparticles is 9 nm.

[0063] The imidazolium ionic liquid of Example 9 (RMImIL) has the following structural formula:

[0064] Among them, R1 is pentyl, R2 is butyl, and the anion X - It is tetrafluoroborate.

[0065] Example 10 A NiO x The method for preparing nanoparticles comprises the following steps: S1: Dissolve Ni(NO3)2·6H2O and imidazole ionic liquid (RMImIL) in ultrapure water and stir evenly, add NaOH solution to adjust the pH value to 10, stir and react, the solution becomes turbid, and Ni(OH)2-RMImIL precipitate is obtained; (The molar ratio of Ni(NO3)2·6H2O and imidazole ionic liquid (RMImIL) is 1:0.1.

[0066] Then the Ni(OH)2-RMImILL precipitate was placed in a centrifuge and centrifuged at 1000 rpm for 15 min, and ultrapure water was added and centrifuged three times to obtain a precipitate product after centrifugation.

[0067] S2: The precipitated product after centrifugation was dried in a vacuum drying oven for 10 h at a temperature of 90 °C to obtain a dry product. The dry product was then calcined at 300 °C for 2.5 h to obtain high-quality NiOx nanoparticles (NiO x -RMImIL), the NiO containing imidazole ionic liquid finally prepared in this embodiment x The average particle size of the nanoparticles is 7 nm.

[0068] The imidazolium ionic liquid of Example 10 has the structural formula of (RMImIL) as follows:

[0069] Wherein, R1 is hexadecyl, R2 is pentyl, and anion X - It is hydrogen sulfate.

[0070] The present invention proposes a method for obtaining high-quality NiO by using imidazole ionic liquid-assisted synthesis x The method is simple, fast, efficient and reproducible. The NiO synthesized by this method x The nanoparticles are small, free of residual impurities, uniform, and have good conductivity. The main synthesis mechanism is to add imidazole ionic liquid to the Ni(NO3)2 precursor to synthesize high-purity NiO x Nanoparticles, due to [RMIm] + NO3 -Impurity ions have lower adsorption energy and can act on the particle surface through strong hydrogen bonds to inhibit the redox reaction at the interface. That is, the adsorption of impurity ions on Ni(OH)2 is inhibited through strong hydrogen bonds and low adsorption performance, obtaining high-purity NiO without residual impurity ions. x Nanoparticles.

[0071] Third, the present invention also discloses a hole transport layer, wherein the hole transport layer is made of NiO prepared by the present invention. x The nanoparticles are made of materials. Preferably, the thickness of the hole transport layer is 15-20 nm, which is conducive to the preparation of high-performance inverse perovskite solar cells.

[0072] The NiO in the present invention x When nanoparticles are used to prepare hole transport layers, NiO x Nanoparticles are small, free of residual impurities, uniform, and have good conductivity. x The nanoparticles are used to prepare the hole transport layer, which is dense and uniform, with fewer defects and pores, and its surface defects and grain boundaries are effectively passivated, thereby enhancing the conductivity of the film, reducing the recombination and leakage of charges, and making the hole transport layer have high conductivity and strong hole extraction ability, greatly improving the comprehensive performance of the device product; at the same time, the NiO containing imidazole ionic liquid prepared by the method of the present invention x Nanoparticles as hole transport layer, NiO x The removal of impurity ions in the nanoparticles can effectively inhibit the NiO x The hole transport layer adopts the NiO containing imidazole ionic liquid prepared by the present invention. x Nanoparticles greatly improve the photoelectric performance and stability of perovskite solar cell devices. Preferably, the thickness of the hole transport layer is controlled to 15-20nm, which will not excessively block the incident light, thereby ensuring that the perovskite layer can fully absorb and utilize light energy; at the same time, the thinner hole transport layer helps to reduce charge recombination and leakage at the interface, thereby reducing the degradation rate of the device and improving the stability and service life of the device.

[0073] Fourth, the present invention also discloses an inverted perovskite solar cell, the structure of which is shown in Figure 1 The inverted perovskite solar cell includes a transparent conductive layer, a hole transport layer, a perovskite active layer, an electron transport layer, a cathode buffer layer and a back electrode stacked from bottom to top. Specifically, the transparent conductive layer can be made of a fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) substrate, corresponding to Figure 1 The FTO / ITO layer in the middle, the transparent conductive layer material in other preparation examples can also be selected from other materials; the hole transport layer is made of NiO prepared by the present invention x Nanoparticles are formed by coating materials on a transparent conductive layer. Figure 1 Medium NiO x -RMImIL layer, the thickness of the hole transport layer formed is controlled within 15~20nm; in the embodiment of the present invention, the perovskite active layer ( Figure 1 PVK layer) with Cs x FA 1- x PbI y Br 3-y As an example, the value range of x is 0-0.3, and the value range of y is 1-3; wherein Cs is cesium, FA is formamidine hydroiodide, Pb is lead, I is iodine, and Br is bromine. The perovskite active layer materials in other preparation examples can also be selected from other materials as needed. 60 For example, fullerene C 60 ,correspond Figure 1 Middle C 60 The electron transport layer material in other preparation examples can also be selected from other materials as needed; the cathode buffer layer in the preparation example of the present invention takes 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Bathocuproine, BCP) as an example, corresponding to Figure 1 In the BCP layer, the cathode buffer layer material in other preparation examples can also be selected from other materials as needed; the back electrode is selected from Cu or Ag, corresponding to Figure 1 Cu / Ag. NiO prepared by the present invention x Nanoparticles as hole transport layers in perovskite solar cells can effectively avoid NiO x Ni in nanoparticles 3 + and I in the perovskite layer - The redox reaction at the interface between the hole transport layer and the perovskite layer is inhibited; at the same time, the imidazole ionic liquid changes the NiO x The polarity of nanoparticles can effectively improve the NiO x The wettability of nanoparticles improves the crystallization of the perovskite layer, thereby effectively suppressing the defects of the hole transport layer and the perovskite interface, that is, passivating the interface defects, and further effectively suppressing the NiO x The redox reaction between the hole transport layer and the perovskite film ultimately improves the photoelectric performance and stability of the perovskite solar cell; at the same time, it can efficiently transfer the holes generated by the perovskite light-absorbing layer to the external circuit, thereby improving the photocurrent density and photoelectric conversion efficiency of the battery.

[0074] Fifth, the present invention also discloses a method for preparing the above-mentioned inverse perovskite solar cell, which is specifically: 1. Preparation of transparent conductive layer: Place the conductive glass substrate coated with FTO or ITO in ultrapure water with a cleaning agent and ultrasonicate for 30 minutes, then replace the ultrapure water and ultrasonicate for another 30 minutes, repeat twice; blow dry with a nitrogen gun, and clean with ultraviolet light (UV) for 5 to 15 minutes.

[0075] 2. NiO x Preparation of hole transport layer: NiO prepared by the present invention x The nanoparticles are dispersed in isopropanol or ultrapure water according to the required concentration, and the dispersion is coated on the UV-treated FTO or ITO substrate by scraping or spin coating. During spin coating, the spin coating speed is 2000~3000rpm, the spin coating time is 30~40s, and then annealed at 80~120℃ for 10~30min to form the required thickness of NiO on the transparent conductive layer. x Hole transport layer.

[0076] 3. Preparation of perovskite active layer: The perovskite system is Cs x FA 1-x PbI y Br 3-y , where x ranges from 0 to 0.3, and y ranges from 1 to 3; the solvent is a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), where the volume ratio of DMF to DMSO is 4:1, and the molar concentration of the perovskite solution is 0.8 to 1.4 mol / L. The preparation methods of the perovskite active layer include spin coating, scraper coating, slit coating, screen printing, etc.; the perovskite annealing temperature is 100 to 170°C, and the annealing time is 10 to 60 minutes; the perovskite solution is coated on the NiO by spin coating, scraper coating, coating or printing. x On the hole transport layer, annealing is performed to obtain a perovskite active layer.

[0077] 4. Preparation of electron transport layer and cathode buffer layer: Spin coating or evaporation process is used to form C on the perovskite active layer. 60 Electron transport layer and BCP cathode buffer layer. 60 The spin coating process of the electron transport layer or the BCP cathode buffer layer is as follows: the rotation speed is 2500~5000 rpm and the spin coating time is 30~50s. 60 The evaporation conditions of the electron transport layer or BCP cathode buffer layer are: C 60The evaporation thickness is 15~30nm, the evaporation speed is 0.1~0.5A / s, the BCP evaporation thickness is 3~5nm, and the evaporation speed is 0.1A / s.

[0078] 5. Preparation of back electrode layer: Cu or Ag electrode is evaporated on the BCP cathode buffer layer with a thickness of 70~120nm and an evaporation rate of 0.1~0.7A / s.

[0079] The preparation method of the above-mentioned inverse perovskite solar cell of the present invention is described in more detail below through a plurality of specific preparation examples.

[0080] Preparation Example 1 A method for preparing an inverted perovskite solar cell is as follows: 1. Prepare a transparent conductive layer: coat an FTO layer on a conductive glass substrate according to a pre-designed scheme, place the conductive glass substrate coated with FTO in ultrapure water with a cleaning agent and ultrasonicate for 30 minutes, then replace the ultrapure water and ultrasonicate for another 30 minutes, repeat twice; blow dry with a nitrogen gun, and clean with ultraviolet light (UV) for 10 minutes. In other preparation examples, the transparent conductive layer can be selected from one or more of FTO or ITO.

[0081] 2. Preparation of NiO x Hole transport layer: NiO prepared in Example 1 x The nanoparticles were dispersed in isopropanol or ultrapure water. The resulting dispersion had a concentration of 10 mg / ml. The dispersion was applied to the UV-treated FTO substrate by spin coating. After annealing, NiO was formed on the FTO layer. x The hole transport layer has a thickness of 15 nm. During the spin coating, the spin coating speed is 3000 rpm, the spin coating time is 30 s, and during the annealing, the temperature is 120° C., and the time is 10 min.

[0082] 3. Preparation of perovskite active layer: the perovskite system is Cs x FA 1-x PbI y Br 3-y , x is 0.1, y is 3; the solvent is a mixed solvent of DMF and DMSO, the volume ratio of DMF to DMSO is 4:1, and the concentration of the perovskite solution is 1 mol / L. x A perovskite active layer of expected thickness is prepared and annealed on the hole transport layer, wherein the perovskite annealing temperature is 150° C. and the annealing time is 30 min.

[0083] 4. Preparation of electron transport layer and cathode buffer layer: The materials of the electron transport layer and cathode buffer layer are C 60and BCP, and C 60 Electron transport layer and BCP cathode buffer layer. 60 The spin coating process of BCP is: the rotation speed is 4000 rpm, and the spin coating time is 30s. Other preparation examples can also use the evaporation process, and the evaporation process conditions are: C 60 The evaporation thickness is 25nm, and the evaporation speed is 0.1~0.3A / s; the BCP evaporation thickness is 5nm, and the evaporation speed is 0.1A / s.

[0084] 5. Prepare the back electrode layer: evaporate Cu or Ag back electrode on the BCP cathode buffer layer, the evaporation thickness is 100nm, and the evaporation rate is 0.1~0.7A / s. After completion, an inverse perovskite solar cell is obtained.

[0085] Preparation Example 2 This preparation example discloses a method for preparing a perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x As the hole transport layer, the NiO prepared in Example 2 x Nanoparticles are used as materials to prepare a hole transport layer with a thickness of 15 nm, wherein the annealing temperature is 80°C and the time is 30 min.

[0086] Preparation Example 3 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x As the hole transport layer, the NiO prepared in Example 3 x Nanoparticles are prepared as materials, the spin coating speed is 2600 rpm, and the thickness of the hole transport layer formed is 17 nm. The annealing temperature is 100°C and the time is 15 min.

[0087] Preparation Example 4 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x As the hole transport layer, the NiO prepared in Example 4 x Nanoparticles are used as materials for preparation, the spin coating speed is 2800 rpm, and the thickness of the hole transport layer formed is 16 nm.

[0088] Preparation Example 5 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x As the hole transport layer, the NiO prepared in Example 5x Nanoparticles are used as materials for preparation, the spin coating speed is 2200 rpm, and the thickness of the hole transport layer formed is 19 nm.

[0089] Preparation Example 6 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x As the hole transport layer, the NiO prepared in Example 6 x Nanoparticles are used as materials for preparation, the spin coating speed is 2000 rpm, and the thickness of the hole transport layer formed is 20 nm.

[0090] Preparation Example 7 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x As the hole transport layer, the NiO prepared in Example 7 x Nanoparticles are used as materials for preparation, the spin coating speed is 2400 rpm, and the thickness of the hole transport layer formed is 18.5 nm.

[0091] Preparation Example 8 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x As the hole transport layer, the NiO prepared in Example 8 x Nanoparticles are used as materials for preparation, the spin coating speed is 2600 rpm, and the thickness of the hole transport layer formed is 17 nm.

[0092] Preparation Example 9 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x When the hole transport layer is used, the NiO prepared in Example 9 x Nanoparticles are used as materials for preparation, the spin coating speed is 2200 rpm, and the thickness of the hole transport layer formed is 16 nm.

[0093] Preparation Example 10 This preparation example discloses a method for preparing an inverse perovskite solar cell, which differs from Preparation Example 1 in that: In the preparation of NiO x When the hole transport layer is used, the NiO prepared in Example 10 x Nanoparticles are used as materials to prepare the hole transport layer with a thickness of 15 nm.

[0094] Comparative Example: This comparative example is an inverted perovskite solar cell prepared by the prior art. The main difference from the preparation example 1 of the present invention is that the material of the hole transport layer is NiO. x The nanoparticles are prepared by conventional methods, that is, without doping, and the annealing temperature of the hole transport layer is high. The specific preparation process is as follows: 1. Preparation of transparent conductive layer: Place FTO conductive glass in ultrapure water with detergent and ultrasonicate for 30 minutes, then replace ultrapure water and ultrasonicate for another 30 minutes, repeat twice; blow dry with a nitrogen gun, and clean with ultraviolet light (UV) for 10 minutes.

[0095] 2. Preparation of NiO x Hole transport layer: 0.5 mol Ni(NO3)2·6H2O was dissolved in 100 mL ultrapure water, ultrasonicated for 10 min, and then NaOH solution was added to adjust the pH value to 10 to obtain Ni(OH)2 precipitate. After heat treatment, NiO x Nanoparticles; a dispersion was obtained according to the method of Preparation Example 1, and then spin-coated on a UV-treated FTO substrate at a spin-coating speed of 3000 rpm and a spin-coating time of 30 s. During annealing, the temperature was 150° C. and the time was 10 min.

[0096] 3. Preparation of perovskite active layer: the perovskite system is Cs x FA 1-x PbI y Br 3-y , x is 0.1, y is 3; the solvent is a mixed solvent of DMF and DMSO, the volume ratio of DMF to DMSO is 4:1, the concentration of the perovskite solution is 1 mol / L, and a perovskite active layer of the same thickness is prepared on the hole transport layer by the same method as in Preparation Example 1; the perovskite annealing temperature is 150°C, and the annealing time is 30 min; 4. Preparation of electron transport layer and cathode buffer layer: The preparation process is the same as that in Preparation Example 1, and an electron transport layer and a cathode buffer layer are sequentially formed on the perovskite active layer. The materials of the electron transport layer and the cathode buffer layer are C 60 and BCP, prepared by spin coating or evaporation process.

[0097] 5. Preparation of back electrode layer: The preparation process is consistent with that of Preparation Example 1. A Cu or Ag back electrode is formed on the BCP by evaporation. The evaporation thickness is 100 nm and the evaporation rate is 0.1-0.7 A / s.

[0098] The main performance parameters of solar cells include: Power Conversion Efficiency (PCE), open-circuit voltage (V OC)、Short-circuit current density(Short-circuit current density,J SC ), Fill Factor (FF). The quality of photovoltaic performance is mainly reflected in the PCE value, and the PCE value is closely related to V OC , J SC And FF are closely related to each other. OC , J SC The higher the values ​​of these three parameters, the higher the photoelectric conversion efficiency PCE, and the better the performance of the solar cell. Table 1 is a performance comparison table of the inverse perovskite solar cell devices prepared by each preparation example of the present invention and the comparative example. It can be seen from Table 1 that the open circuit voltage Voc value of the perovskite solar cell prepared by the preparation example of the present invention increases, the short circuit current Jsc value increases, the fill factor FF value increases, and the energy conversion efficiency PCE increases; the performance of the inverse perovskite solar cell device prepared by the present invention is obviously better than the device performance presented by the data in the comparative example. Therefore, the in-situ functionalized NiO prepared by the present invention is x Nanoparticles, as hole transport layer materials, improve the photoelectric performance of perovskite solar cells.

[0099] Table 1 Comparison of the performance of the inverse perovskite solar cell devices prepared in the preparation examples of the present invention and the comparative examples

[0100] Figure 2 NiO doped with imidazole ionic liquid EMImCl prepared in Example 1 of the present invention x Nanoparticles and undoped NiO prepared in the comparative example x The conductivity comparison of nanoparticles, NiO doped with imidazole ionic liquid EMImCl in the present invention x Nanoparticles are a type of NiO x Nanoparticles, that is, doping represents in-situ functionalization. As can be seen from the figure, the EMImCl-doped NiO x The slope of the curve of the nanoparticles is greater than that of the undoped NiO prepared in the comparative example. x The slope of the curve of the nanoparticles shows that the conductivity is increased by more than 2 times, indicating that EMImCl-doped NiO x Nanoparticles have more excellent electrical conductivity. The NiOx nanoparticles prepared by the present invention are applied to prepare the hole transport layer, so that the hole transport layer has high conductivity and strong hole extraction ability, which greatly improves the comprehensive performance of the inverse perovskite solar cell device product. x The removal of impurity ions in the nanoparticles can effectively inhibit the NiO xThe redox reaction between the NiO and the perovskite film can slow down the degradation of device performance. x The conductivity curve of the nanoparticles is similar to that of Example 1, which can be referred to Figure 2 The correlation curve.

[0101] Figure 3 EMImCl-doped NiO prepared in Example 1 of the present invention x Nanoparticles and undoped NiO prepared in the comparative example x X-ray diffraction (XRD) comparison of nanoparticles shows that EMImCl-doped NiO x The XRD peak intensity of the nanoparticles is enhanced and there is no impurity peak, indicating that there are no impurity ions on the surface of the particles after EMImCl doping; 38° corresponds to the diffraction peak of the (111) crystal plane, 43° corresponds to the diffraction peak of the (200) crystal plane, and 63° corresponds to the diffraction peak of the (220) crystal plane. Therefore, the EMImCl-doped NiO prepared by the present invention x There is no impurity ion residue on the surface of the nanoparticles. x The X-ray diffraction pattern (XRD) of the nanoparticles is similar to that of Example 1, which can be referred to Figure 3 Related graphs in .

[0102] Figure 4 EMImCl-doped NiO prepared in Example 1 of the present invention x Transmission electron microscopy (TEM) of the nanoparticles shows that the diameter of the nanoparticles is ≤10nm, which is much smaller than the existing nickel oxychloride nanoparticles with a size of 200~400nm. The smaller nanoparticles help NiO x The nanoparticles are evenly dispersed in the solvent to prepare smoother NiO x The small size of NiO is conducive to forming a more compact and uniform hole transport layer in the preparation of solar cells. The improvement of compactness and uniformity helps to reduce defects and pores in the hole transport layer, thereby reducing the risk of charge recombination and leakage and improving charge transfer efficiency. In addition, the small size of NiO x Nanoparticles have a larger specific surface area, which is conducive to forming more contact points with surrounding materials, thereby enhancing conductivity. The enhancement of conductivity helps to improve the charge transport capacity of the hole transport layer in perovskite solar cells, thereby improving the photoelectric conversion efficiency of the battery. Figure 6 It can be seen that EMImCl-doped NiO x The perovskite film prepared by nanoparticles is dense and has large grains running through it, which means that the perovskite film is relatively flat, so the perovskite grains can grow through it. Smaller-sized nanoparticles can prepare a film with good flatness and uniform surface.x The transmission electron microscopy (TEM) image of the nanoparticles is similar to that of Example 1, which can be referred to Figure 4 Chinese atlas.

[0103] Figure 5 The EMImCl-doped NiO prepared in Example 1 of the present invention x Nanoparticles and undoped NiO prepared using Comparative Example 1 x NiO nanoparticles were prepared x layer, and tested each NiO x The water contact angle diagram obtained by Figure 5 It can be seen that the EMImCl-doped NiO x Nanoparticles prepared from NiO x The contact angles of the layers are 18.4° and 19.2°, while the undoped NiO x The contact angles of the nanoparticles are 28.1° and 28.9°. In comparison, the contact angles obtained in the present invention are smaller, indicating that the NiO doped with the imidazole ionic liquid EMImCl of the present invention x Nanoparticles prepared from NiO x The layer has good wettability and is applied to the hole transport layer material of perovskite solar cells. x When the layer wettability is improved, the perovskite crystallization is improved accordingly, which in turn improves the quality of the perovskite film, thereby suppressing the defects of the hole transport layer and the perovskite interface.

[0104] Figure 6 The EMImCl-doped NiO prepared in Example 1 of the present invention x Surface SEM images (upper right) and cross-sectional SEM images (lower right) of the perovskite film prepared by nanoparticles, as well as the undoped NiO in the comparative example. x The surface SEM images (upper left) and cross-sectional SEM images (lower left) of the perovskite film prepared by the nanoparticle layer show that the EMImCl-doped NiO x The perovskite prepared by nanoparticles has an increased grain size, a dense film and a large grain. The hole transport layer of the present invention uses imidazole-containing ionic liquid doped nickel oxide nanoparticles. On the one hand, the imidazole cations in the nickel oxide can reduce the binding energy on the surface of the nickel oxide film, thereby reducing the defect state of the nickel oxide film and increasing its hole extraction rate. The nitrogen atoms and electron-donating alkyl chains in the imidazole cations contained in the ionic liquid can passivate the uncoordinated Pb 2+These ionic bonds can passivate the defects of the perovskite film and inhibit the recombination of carriers at the interface; on the other hand, the anions in the nickel oxide can passivate the defects on the nickel oxide side, increase the wettability of the nickel oxide substrate, and make the nickel oxide contact with the perovskite film better, which is beneficial to promote the growth of perovskite grains.

[0105] Figure 7 For example 1 (i.e., the hole transport layer is EMImCl-doped NiO x The perovskite film prepared by the hole transport layer is compared with the comparative example (i.e., the hole transport layer is undoped NiO x The XRD spectrum comparison diagram of the perovskite film prepared by the present invention is shown in Figure 1. As can be seen from the figure, the XRD peak intensity of the perovskite film prepared by the present invention is significantly enhanced, and there is no impurity peak, indicating that the EMImCl-doped NiO x The perovskite film formed on the hole transport layer is well crystallized, with high film quality and few defects.

[0106] Figure 8 The figure is a comparison diagram of the device efficiency of the inverse perovskite solar cell prepared in Preparation Example 1 of the present invention and the inverse perovskite solar cell prepared in the comparative example. As can be seen from the figure, the open circuit voltage V oc Value, short circuit current J sc The value and filling factor FF value are significantly improved compared with the comparative example, indicating that the NiO doped with the imidazole ionic liquid of the present invention x The inverse perovskite solar cell prepared by nanoparticles has better device performance. The ionic liquid acts as a bridge, promoting the extraction of charge from perovskite to nickel oxide, enhancing the interface contact, thereby increasing the battery current density and opening voltage, and ultimately improving the photoelectric performance and stability performance of the perovskite solar cell device.

[0107] The present invention provides a method for preparing a hole transport layer material NiO x A new and unique method, namely, in NiO x The introduction of imidazole ionic liquid into the nanoparticles can effectively inhibit the adsorption of impurity ions on Ni(OH)2. x Nanoparticles are used in perovskite solar cells to obtain a hole transport layer (HTL) with high conductivity and strong hole extraction ability; importantly, the removal of impurity ions can effectively inhibit the NiO x The redox reaction between the perovskite film and the perovskite film can slow down the deterioration of the performance of the perovskite solar cell device and improve the photoelectric performance and stability of the device.

Claims

1. A NiO x The method for preparing nanoparticles is characterized in that: The following steps are involved: S1: dissolving nickel nitrate hexahydrate and imidazole ionic liquid in water in molar ratio, stirring evenly, adjusting the pH value of the solution system to 9-11, stirring and reacting until the solution becomes turbid, and obtaining Ni(OH)2-RMImIL precipitate; S2: After the Ni(OH)2-RMImIL precipitate is dried, it is calcined at 270-330°C for 1-3h to obtain NiO x Nanoparticles; In step S1, the structural formula of the imidazole ionic liquid is: Wherein, R1 is any one of methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl; R2 is any one of methyl, ethyl, propyl, butyl and pentyl; X - It is any one of chloride, bromide, iodide, tetrafluoroborate, hexafluorophosphate, acetate, bis(trifluoromethanesulfonyl)imide, nitrate, perchlorate, hydrogen sulfate, dihydrogen phosphate, trifluoromethanesulfonate, trifluoroacetate and p-toluenesulfonate.

2. A NiO according to claim 1 x The method for preparing nanoparticles is characterized by: In step S1, the molar ratio of the nickel nitrate hexahydrate to the imidazole ionic liquid is 1:(0.05-0.2).

3. A NiO according to claim 1 or 2 x The method for preparing nanoparticles is characterized by: In step S1, after stirring the reaction until the solution becomes turbid, the reaction system is centrifuged to obtain the Ni(OH)2-RMImIL precipitate; During the centrifugal treatment, the rotation speed is 800-3000 rpm and the centrifugal time is 10-20 min.

4. A NiO according to claim 3 x The method for preparing nanoparticles is characterized by: In step S2, the drying temperature is 80-100°C and the drying time is 8-16 hours.

5. A NiO according to claim 4 x The method for preparing nanoparticles is characterized by: R1 is methyl; R2 is ethyl; X - For chloride ion.

6. A NiO x Nanoparticles, characterized in that: Prepared by the method described in any one of claims 1 to 5; the NiO x The average size of nanoparticles is 5~10nm.

7. A hole transport layer, characterized in that: With the NiO described in claim 6 x Nanoparticles are made of materials.

8. The hole transport layer according to claim 7, characterized in that: The thickness of the hole transport layer is 15-20 nm.

9. An inverted perovskite solar cell, comprising a transparent conductive layer, a hole transport layer, a perovskite active layer, an electron transport layer, a cathode buffer layer and a back electrode stacked from bottom to top, characterized in that: The hole transport layer is the hole transport layer according to claim 7 or 8.

10. A method for preparing an inverse perovskite solar cell according to claim 9, characterized in that: The following steps are involved: Step 1: NiO as claimed in claim 6 x The nanoparticles are dispersed in a dispersion according to the required concentration, and the dispersion is coated on the pre-treated transparent conductive layer by blade coating or spin coating. After annealing at 80-120° C. for 10-30 min, a hole transport layer of the required thickness is formed on the transparent conductive layer. Step 2: sequentially preparing a perovskite active layer, an electron transport layer, a cathode buffer layer and a back electrode on the hole transport layer to obtain an inverted perovskite solar cell.

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