Low-dimensional perovskite single crystal, low-dimensional / three-dimensional perovskite thin film, perovskite solar cell and preparation methods of low-dimensional perovskite single crystal, low-dimensional / three-dimensional perovskite thin film and perovskite solar cell

Abstract

The invention relates to a low-dimensional perovskite single crystal, a low-dimensional / three-dimensional perovskite thin film, a perovskite solar cell and a preparation method of the low-dimensional perovskite single crystal, the low-dimensional perovskite single crystal is specifically obtained by synthesizing organic spacer molecule benzimidazole or a derivative thereof, so that the variety range of low-dimensional perovskite is widened; meanwhile, the low-dimensional perovskite single crystal is applied to a three-dimensional perovskite material, the three-dimensional perovskite material is modified and improved, a low-dimensional / three-dimensional perovskite thin film with higher crystallinity and stronger hydrophobicity is prepared, and the low-dimensional / three-dimensional perovskite thin film is further used as a light absorption layer of the perovskite solar cell. Finally, the purpose of improving the energy conversion efficiency of the perovskite solar cell is achieved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of perovskite photoelectric materials, and in particular to three-dimensional perovskites, low-dimensional / three-dimensional perovskite materials, perovskite solar cells and preparation methods thereof. Background Art

[0002] As a new type of photovoltaic material, the photoelectric conversion efficiency of perovskite solar cells has increased from 3.9% when it was discovered in 2009 to 26.1%, which is comparable to the efficiency of commercial crystalline silicon cells. Low-dimensional (LD) perovskites provide an exciting way to explore stable perovskite solar cells (PSCs). Low-dimensional (LD) perovskites include zero-dimensional (0D), one-dimensional (1D) and two-dimensional (2D) perovskites, among which one-dimensional (1D) and two-dimensional (2D) perovskites are more widely studied than zero-dimensional (0D). One-dimensional (1D) perovskites have linear or tubular structures; two-dimensional (2D) perovskites have layered structures, which are large-sized organic ligands introduced into three-dimensional (3D) perovskite materials, so that they are sheared along a specific axis into two-dimensional (2D) materials. 2D perovskite structures are divided into three types according to the different molecular structures of organic ligands: Ruddlesden–Popper (RP), Dion–Jacobson (DJ) and Alternating-cation interlayer (ACI). The chemical formulas of the three structures are R2A n- 1B n X3 n+1 , R′A n-1 B n X 3n+1 or R″A n B n X 3n+1 In the above chemical formula, R is a large-sized monoamine organic cation, R′ is a large-sized diamine organic cation, and R″ is a guanidine cation (GA + ), the n value represents the metal halide octahedron between adjacent organic layers [BX6] 4- The number of layers. It can be seen that the low-dimensional perovskite structure is diverse. However, the known low-dimensional perovskite varieties and application research are still relatively small, so it is necessary to further develop new low-dimensional spacer organic molecules to expand the variety and application research scope of low-dimensional perovskites.

[0003] As for three-dimensional perovskites, since they are sensitive to water, which further affects the energy conversion efficiency of PSCs, it is of research significance to increase the hydrophobicity of three-dimensional perovskites to obtain three-dimensional perovskite solar cells with high energy conversion efficiency. Summary of the invention

[0004] In view of this, the present disclosure provides a low-dimensional perovskite, a low-dimensional / three-dimensional perovskite film, a perovskite solar cell and a preparation method to solve the problem that there are few varieties of low-dimensional perovskites and the three-dimensional perovskite has hydrophobicity that affects the energy conversion efficiency of three-dimensional perovskite solar cells.

[0005] The core of the disclosed method is to use benzimidazole or its derivatives to synthesize a new type of low-dimensional perovskite single crystal. At the same time, directly on the three-dimensional perovskite film, benzimidazole or its derivatives interact with the residual lead iodide on the surface of the film to spontaneously form a low-dimensional perovskite single crystal phase, and finally form a low-dimensional / three-dimensional heterojunction perovskite film. The low-dimensional / three-dimensional heterojunction perovskite film is used as the light-absorbing layer of the perovskite solar cell to obtain a perovskite solar cell with high energy conversion efficiency.

[0006] Based on the core of the above method, in the first aspect, the low-dimensional perovskite single crystal disclosed in the present invention has a chemical structural formula of:

[0007] (R)2(M) n Pb n I 3n+1 ;

[0008] In the formula, R is the iodide of benzimidazole or its derivative; M is CH3NH3, CH(NH2)2 or Cs; and n is the number of inorganic layers.

[0009] In the present disclosure and possible embodiments, the benzimidazole derivative is 6-methylbenzimidazole or 6-trifluoromethylbenzimidazole.

[0010] In a second aspect, the method for preparing the low-dimensional perovskite single crystal according to the first aspect comprises:

[0011] After the mixed solution of the lead source, hydroiodic acid and hypophosphorous acid is stirred and reacted at 100-120° C. for 1-2 hours, the iodide of benzimidazole or its derivative is continuously added, and the stirring reaction is continued for 1-2 hours. During the cooling process of the system after the reaction is completed, crystals are precipitated, and the crystals are obtained to obtain the low-dimensional perovskite single crystal.

[0012] In the present disclosure and possible embodiments, the lead source is lead oxide, lead iodide or lead acetate; the iodide is CH3NH3I, CH(NH2)2I or CsI; in molar ratio, lead source: benzimidazole or its derivative: iodide: HI: H3PO2 = n: 0.5: n: 2n: 2n, n = 1, 2 or 3; and / or,

[0013] The method for preparing the iodide of benzimidazole or its derivative comprises:

[0014] Benzimidazole or its derivative is reacted with hydroiodic acid having a mass content of 50-60% at room temperature with stirring for 2-3 hours in a stoichiometric molar ratio of 1:1 to obtain the iodide of the benzimidazole or its derivative.

[0015] In a third aspect, the low-dimensional / three-dimensional perovskite film has a film structure of:

[0016] Based on the three-dimensional perovskite film, the low-dimensional perovskite single crystal described in the first aspect is formed on the surface of the three-dimensional perovskite film.

[0017] In a fourth aspect, the method for preparing the low-dimensional / three-dimensional perovskite film according to the third aspect comprises:

[0018] Preparation of three-dimensional perovskite films;

[0019] The iodide of benzimidazole or its derivative is prepared into an organic solution, and the organic solution is spin-coated on the three-dimensional perovskite film. The iodide of benzimidazole or its derivative spontaneously reacts with the residual PbI2 on the three-dimensional perovskite film to form a low-dimensional perovskite single crystal, thereby obtaining the low-dimensional / three-dimensional perovskite film.

[0020] In the present disclosure and possible embodiments, the method for preparing a three-dimensional perovskite film includes:

[0021] Dissolving lead iodide in a first organic solvent to obtain a lead iodide precursor solution; dissolving formamidine iodide and methylammonium chloride in a second organic solvent to obtain an organic halide precursor solution;

[0022] The lead iodide precursor solution is spin-coated on the substrate and then annealed at 60-75° C. for 1-3 minutes to obtain a lead iodide film. The organic halide precursor solution is spin-coated on the lead iodide film and then annealed at 140-160° C. for 10-20 minutes to obtain the three-dimensional perovskite film.

[0023] In the present disclosure and possible embodiments, the iodide of the benzimidazole or its derivative is prepared into the organic solution using an organic solvent;

[0024] The first organic solvent is a mixed solvent with a mass ratio of DMF:DMSO=9.5:0.5, and the concentration of the lead iodide precursor solution is 1.3M;

[0025] The second organic solvent is isopropanol;

[0026] The organic solvent is one of isopropanol and N,N-dimethylformamide or a mixed solvent of the two.

[0027] In a fifth aspect, the perovskite solar cell comprises:

[0028] A light absorbing layer, wherein the light absorbing layer is composed of the low-dimensional / three-dimensional perovskite film according to claim 5.

[0029] In a sixth aspect, the method for preparing the perovskite solar cell according to the fifth aspect comprises:

[0030] A transparent conductive substrate is prepared, an electron transport layer or a hole transport layer is prepared on the transparent conductive substrate, a light absorbing layer is prepared on the electron transport layer or the hole transport layer according to the preparation method of the low-dimensional / three-dimensional perovskite film according to any one of claims 6 to 8, and a metal electrode is vacuum evaporated after the electron transport layer or the hole transport layer is prepared on the light absorbing layer to obtain the perovskite solar cell.

[0031] The present invention has the beneficial effects:

[0032] The present disclosure provides a low-dimensional perovskite single crystal, which is synthesized by applying an organic spacer molecule benzimidazole or its derivatives, thereby broadening the variety range of low-dimensional perovskites; at the same time, the low-dimensional perovskite single crystal is applied to a three-dimensional perovskite material, and the three-dimensional perovskite material is modified and improved to prepare a low-dimensional / three-dimensional perovskite film with higher crystallinity and stronger hydrophobicity, and the low-dimensional / three-dimensional perovskite film is further used as a light-absorbing layer of a perovskite solar cell, ultimately achieving the purpose of improving the energy conversion efficiency of the perovskite solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings herein are incorporated into the specification and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and are used to illustrate the technical solutions of the present disclosure together with the specification.

[0034] Figure 1-1 , 1-2 , 1-3 are schematic diagrams of the molecular structures of benzimidazole, 6-methylbenzimidazole and 6-trifluoromethylbenzimidazole respectively;

[0035] Figure 2 is a single crystal image of benzimidazole (BIZ)-based perovskite synthesized in Example 1;

[0036] Figure 3 A comparison diagram of the X-ray diffraction spectrum (XRD) of the benzimidazole (BIZ)-based perovskite single crystal synthesized in Example 1 and the fitted X-ray diffraction spectrum (XRD) diagram;

[0037] Figure 4 This is a single crystal image of 6-methylbenzimidazole (6-MeBIm)-based perovskite synthesized in Example 2;

[0038] Figure 5A comparison diagram of the X-ray diffraction spectrum (XRD) of the 6-methylbenzimidazole (6-MeBIm)-based perovskite single crystal synthesized in Example 2 and the fitted X-ray diffraction spectrum (XRD) diagram;

[0039] Figure 6 This is a single crystal image of 6-trifluoromethylbenzimidazole (6-TFBIm) based perovskite synthesized in Example 3;

[0040] Figure 7 A comparison diagram of the X-ray diffraction spectrum (XRD) of the 6-trifluoromethylbenzimidazole (6-TFBIm)-based perovskite single crystal synthesized in Example 3 and a fitted X-ray diffraction spectrum (XRD) diagram;

[0041] Figure 8 The flowchart of the preparation of low-dimensional / three-dimensional heterojunction perovskite film in Example 4;

[0042] Fig. 9 The photoluminescence spectrum (PL) of the low-dimensional / three-dimensional heterojunction perovskite film of Example 4;

[0043] Fig.10 is an X-ray diffraction spectrum (XRD) diagram of the low-dimensional / three-dimensional heterojunction perovskite film of Example 4;

[0044] Fig.11 This is the ultraviolet visible absorption (UV-vis) spectrum of the low-dimensional / three-dimensional heterojunction perovskite film of Example 4;

[0045] Fig.12 This is a scanning electron microscope (SEM) image of the three-dimensional perovskite film of Example 4;

[0046] Fig.13 This is a scanning electron microscope (SEM) image of a low-dimensional / three-dimensional heterojunction perovskite film modified by benzimidazole (BIZ) in Example 4;

[0047] Fig.14 This is a scanning electron microscope (SEM) image of a low-dimensional / three-dimensional heterojunction perovskite film modified with 6-methylbenzimidazole (6-MeBIm) in Example 4;

[0048] Fig.15 This is a scanning electron microscope (SEM) image of a low-dimensional / three-dimensional heterojunction perovskite film modified with 6-trifluoromethylbenzimidazole (6-TFBIm) in Example 4;

[0049] Figure 16-1 , 16-2, 16-3, 16-4 are the corresponding water contact angle diagrams of three-dimensional perovskite film, benzimidazole (BIZ) modified, 6-methylbenzimidazole (6-MeBIm) modified, and 6-trifluoromethylbenzimidazole (6-TFBIm) modified low-dimensional / three-dimensional heterojunction perovskite film, respectively;

[0050] Fig.17 This is a schematic diagram of the structure of a perovskite solar cell device according to Example 5;

[0051] Fig.18 Comparison of the photoelectric conversion efficiency between the control group (pure 3D perovskite) of Example 5 and the target group after adding 6-trifluoromethylbenzimidazole (6-TFBIm). DETAILED DESCRIPTION

[0052] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure.

[0053] Furthermore, unless the context clearly requires otherwise, throughout the specification and claims, the words "include," "comprises," and similar words should be interpreted in an inclusive sense rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to."

[0054] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0055] The method for preparing a low-dimensional perovskite single crystal in the embodiment of the present disclosure comprises the following steps:

[0056] 1. Preparation of iodide of benzimidazole or its derivatives:

[0057] Benzimidazole or its derivative is reacted with hydroiodic acid having a mass content of 50-60% at room temperature with stirring at a stoichiometric molar ratio of 1:1 for 2-3 hours to obtain the iodide of benzimidazole or its derivative.

[0058] In one embodiment, benzimidazole or its derivatives are benzimidazole, 6-methylbenzimidazole and 6-trifluoromethylbenzimidazole; the molecular structure thereof is as follows Figure 1-1 , 1-2 , as shown in 1-3.

[0059] 2. Preparation of low-dimensional perovskite single crystals:

[0060] After the mixed solution of the lead source, hydroiodic acid and hypophosphorous acid is stirred and reacted at 100-120° C. for 1-2 hours, the iodide of benzimidazole or its derivative is continuously added, and the stirring reaction is continued for 1-2 hours. During the cooling process of the system after the reaction is completed, crystals are precipitated, and the crystals are obtained to obtain a low-dimensional perovskite single crystal, whose chemical structure is:

[0061] (R)2(M) n Pb n I 3n+1 ;

[0062] In the formula, R is the iodide of benzimidazole or its derivative; M is CH3NH3, CH(NH2)2 or Cs; and n is the number of inorganic layers.

[0063] In one embodiment, the benzimidazole derivative is 6-methylbenzimidazole or 6-trifluoromethylbenzimidazole.

[0064] In a specific embodiment, the lead source is lead oxide, lead iodide or lead acetate; the iodide is CH3NH3I, CH(NH2)2I or CsI; in molar ratio, the lead source: benzimidazole or its derivative: iodide: HI: H3PO2 = n: 0.5: n: 2n: 2n, n = 1, 2 or 3.

[0065] The method for preparing a low-dimensional / three-dimensional perovskite film in the embodiment of the present disclosure comprises the following steps:

[0066] 1. Preparation of three-dimensional perovskite films:

[0067] (1) Lead iodide is dissolved in a first organic solvent to obtain a lead iodide precursor solution; and formamidine iodide and methylammonium chloride are dissolved in a second organic solvent to obtain an organic halide precursor solution.

[0068] In a specific embodiment, the first organic solvent is a mixed solvent with a mass ratio of DMF:DMSO=9.5:0.5, and the concentration of the obtained lead iodide precursor solution is 1.3M; the second organic solvent is isopropanol.

[0069] (2) spin coating a lead iodide precursor solution on a substrate to obtain a lead iodide film, and annealing the film at 60-75° C. for 1-3 min to form a lead iodide layer; continue to spin coating an organic halide precursor solution on the lead iodide layer to obtain an organic halide film, and annealing the film at 140-160° C. for 10-20 min to form an organic halide layer. In the above process, the organic halide reacts with lead iodide (PbI2) to generate a 3D perovskite film, and the 3D perovskite film is an α-FAPbI3 perovskite film.

[0070] 2. Preparation of low-dimensional / three-dimensional perovskite films:

[0071] The iodide of benzimidazole or its derivative is prepared into an organic solution, and the organic solution is spin-coated on the 3D perovskite film. The iodide of benzimidazole or its derivative reacts spontaneously with the residual PbI2 on the 3D perovskite film to form a low-dimensional perovskite single crystal, thereby obtaining a low-dimensional / three-dimensional perovskite film based on the 3D perovskite film and with low-dimensional perovskite single crystals formed on the surface of the film.

[0072] In a specific embodiment, the iodide of benzimidazole or its derivative is prepared into an organic solution by using an organic solvent; the organic solvent is one of isopropanol and N,N-dimethylformamide or a mixed solvent of the two.

[0073] The disclosed embodiment prepares a perovskite solar cell, the structure of which is, from top to bottom, a transparent conductive substrate, an electron transport layer, a perovskite light absorption layer, a hole transport layer and a metal electrode; or a transparent conductive substrate, a hole transport layer, a perovskite light absorption layer, an electron transport layer and a metal electrode; the preparation steps are as follows:

[0074] 1. Take a transparent conductive substrate and prepare an electron transport layer or a hole transport layer on the transparent conductive substrate;

[0075] In a specific embodiment, the transparent conductive substrate includes two parts: a transparent substrate and a conductive layer, wherein the transparent substrate is one of a glass substrate, a quartz substrate, a PET substrate, a PEN substrate, and a PI substrate; and the conductive layer is one of an indium tin oxide film, a fluorine-doped tin dioxide film, or a metal grid film prepared on the transparent substrate.

[0076] In a specific embodiment, the electron transport layer material is one or more of ZnO, TiO2, SnO2, PCBM, fullerene, and fullerene derivatives.

[0077] In a specific embodiment, the hole transport layer material is one or more of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly-3,4-ethylenedioxythiophene / polystyrene sulfonate, nickel oxide, copper oxide, 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene, cuprous thiocyanate, and molybdenum oxide.

[0078] 2. Prepare a metal halide lead iodide precursor solution, and prepare a lead iodide layer on the electron transport layer or the hole transport layer; apply an organic halide precursor solution on the lead iodide layer to obtain an organic halide layer; dissolve the iodide of the benzimidazole or its derivative in an organic solvent and spin-coat it on the organic halide layer to form a low-dimensional phase, thereby obtaining a perovskite light-absorbing layer.

[0079] 3. After preparing an electron transport layer or a hole transport layer on the perovskite light absorbing layer, a metal electrode is vacuum evaporated to complete the preparation of the perovskite solar cell disclosed in the present invention.

[0080] In a specific embodiment, the metal electrode is one or more of an Au electrode, an Ag electrode, an Al electrode, a Cu electrode, and a metal oxide electrode.

[0081] The following are specific embodiments of the present disclosure:

[0082] Example 1

[0083] 1. The method for preparing low-dimensional perovskite single crystals based on benzimidazole (BIZ) as a spacer molecule is as follows:

[0084] (1) Preparation of benzimidazole iodide:

[0085] Benzimidazole (BIZ) and hydroiodic acid (HI aqueous solution) with a mass content of 50-60% are stirred and reacted at room temperature for 2-3 hours according to a stoichiometric molar ratio to obtain a benzimidazole iodide (BIZI) solution; the reaction process is: BIZ+HI→BIZI+1 / 2H2; the benzimidazole iodide (BIZI) solution is subjected to rotary evaporation and washing to obtain a benzimidazole iodide (BIZI) solid.

[0086] (2) Synthesis of benzimidazole (BIZ)-based perovskite single crystal materials:

[0087] A lead source (lead oxide PbO), a hydroiodic acid (HI aqueous solution) with a mass content of 50-60%, and a hypophosphorous acid (H3PO2) aqueous solution with a mass content of 50-55% are mixed and stirred to form a uniform solution, and the temperature is controlled at 100-120°C for stirring and reacting for 0.5h; then iodide (CH(NH2)2I) is added to the above solution, and then BIZI solid is added. After the reaction is completed, the temperature is controlled at 100-120°C for stirring and reacting for 2h; the solution is placed on a hot plate and cooled to room temperature at 3°C / h. Crystals are precipitated during the cooling process. Finally, after washing and filtering, (BIZ)2(M) is obtained. n Pb n I 3n+1 Single crystal material.

[0088] The reaction process is: nPbO+BIZI+nMI+2nHI→(BIZ)2(M) n-1 Pb n I 3n+1 +nH2O, in addition to this embodiment, M can also be CH3NH3 or Cs.

[0089] Among them, the amount of BIZI solution is measured by the BIZI provided, the amount of HI is measured by the HI provided, and the amount of H3PO2 aqueous solution is measured by the H3PO2 provided; the molar ratio of PbO:BIZI:iodide:HI:H3PO2 is =n:0.5:n:2n:2n, n=1, 2 or 3.

[0090] 2. (BIZI)2(M) n Pb n I 3n+1 Single crystal material testing:

[0091] The single crystal structure of this embodiment 1 is as follows Figure 2 As shown, it can be seen that benzimidazole (BIZ) finally forms a one-dimensional (1D) perovskite single crystal structure. Figure 3 By comparing the single crystal X-ray diffraction spectrum (XRD) pattern with the fitted X-ray diffraction spectrum (XRD) pattern, it can be proved that the one-dimensional (1D) perovskite single crystal was successfully synthesized in Example 1 (Zeitschrift füranorganische und allgemeine Chemie, 2016, 642(23): 1369-1376.).

[0092] Example 2

[0093] 1. The method for preparing low-dimensional perovskite single crystals based on 6-methylbenzimidazole (6-MeBIm) as a spacer molecule is as follows:

[0094] (1) Preparation of 6-methylbenzimidazole (6-MeBIm) iodide:

[0095] 6-Methylbenzimidazole (6-MeBIm) and hydroiodic acid (HI aqueous solution) with a mass content of 50-60% are reacted at room temperature for 3 hours with stirring according to a stoichiometric molar ratio to obtain a 6-methylbenzimidazole (6-MeBImI) solution; the reaction process is: 6-MeBIm+HI→6-MeBImI+1 / 2H2; the 6-methylbenzimidazole (6-MeBImI) solution is subjected to rotary evaporation and washing to obtain a 6-methylbenzimidazole iodide (6-MeBImI) solid.

[0096] (2) Synthesis of 6-methylbenzimidazole (6-MeBIm) based perovskite single crystal materials:

[0097] A lead source (lead oxide PbO), a hydroiodic acid (HI aqueous solution) with a mass content of 50-60%, and a hypophosphorous acid (H3PO2) aqueous solution with a mass content of 50-55% are mixed and stirred to form a uniform solution (the solvent here is N,N-dimethylformamide), and the temperature is controlled at 100-120°C and stirred for 0.5h; then iodide (CH(NH2)2I) is added to the above solution, and then 6-MeBImI solid is added. After the reaction is completed, the temperature is controlled at 100-120°C and stirred for 2h; the solution is placed on a hot plate and cooled to room temperature at 3°C / h, and crystals are precipitated during the cooling process. Finally, after washing and filtering, (6-MeBIm)2(M)nPbnI is obtained. 3n+1 Single crystal material.

[0098] The reaction process is: nPbO+6-MeBImI+nMI+2nHI→(6-MeBIm)2(M) n-1 Pb n I 3n+1 +nH2O, in addition to this embodiment, M can also be CH3NH3 or Cs.

[0099] The amount of 6-TFBImI solution used is measured by the 6-MeBImI it provides, the amount of HI used is measured by the HI it provides, the amount of H3PO2 aqueous solution used is measured by the H3PO2 it provides, and the molar ratio of PbO:6-MeBImI:iodide:HI:H3PO2 is =n:0.5:n:2n:2n, n=1, 2 or 3.

[0100] (3)(6-MeBIm)2(M)nPbnI 3n+1 Single crystal material testing:

[0101] The single crystal structure of Example 2 is as follows Figure 4 As shown, it can be seen that 6-methylbenzimidazole (6-MeBIm) finally forms a one-dimensional (1D) perovskite single crystal structure. Figure 5 By comparing the single crystal X-ray diffraction spectrum (XRD) diagram with the fitted X-ray diffraction spectrum (XRD) diagram, it can be proved that the one-dimensional (1D) perovskite single crystal was successfully synthesized in Example 2, and the single crystal structure information is shown in Table 1:

[0102] Table 1 Single crystal structure information

[0103]

[0104] Example 3

[0105] 1. The steps of preparing low-dimensional perovskite single crystal based on 6-trifluoromethylbenzimidazole (6-TFBIm) as a spacer molecule are as follows:

[0106] (1) Preparation of 6-trifluoromethylbenzimidazole iodide (6-TFBImI):

[0107] 6-Trifluoromethylbenzimidazole (6-TFBIm) and hydroiodic acid (HI aqueous solution) with a mass content of 50-60% are heated under reflux at 120° C. for 3 hours in a stoichiometric molar ratio to obtain a 6-trifluoromethylbenzimidazole iodide (6-TFBImI) solution; the reaction process is: 6-TFBIm+HI→6-TFBImI+1 / 2H2; the 6-trifluoromethylbenzimidazole iodide (6-TFBImI) solution is subjected to rotary evaporation and washing to obtain a 6-trifluoromethylbenzimidazole iodide (6-TFBImI) solid.

[0108] (2) Synthesis of 6-trifluoromethylbenzimidazole-based perovskite single crystal material:

[0109] A lead source (lead oxide PbO), a hydroiodic acid (HI aqueous solution) with a mass content of 50-60%, and a hypophosphorous acid (H3PO2) aqueous solution with a mass content of 50-55% are mixed and stirred to form a uniform solution, and the temperature is controlled at 100-120° C. and stirred for 0.5 h; then iodide (CH(NH2)2I) is added to the above solution, and then 6-TFBImI solid is added. After the temperature is controlled at 100-120° C. and stirred for 2 h; the solution is placed on a hot plate and cooled to room temperature at 3° C. / h, and crystals are precipitated during the cooling process. Finally, after washing and filtering, (6-TFBIm)2(M)nPbnI is obtained. 3n+1 Single crystal material.

[0110] The reaction process is: nPbO+6-TFBImI+nMI+2nHI→(6-TFBIm)2(M) n-1 Pb n I 3n+1 +nH2O, in addition to this embodiment, M can also be CH3NH3 or Cs.

[0111] Among them, the amount of 6-TFBImI solution is measured by the 6-TFBImI provided, the amount of HI is measured by the HI provided, the amount of H3PO2 aqueous solution is measured by the H3PO2 provided, and the molar ratio of PbO:6-TFBImI:iodide:HI:H3PO2 is =n:0.5:n:2n:2n, n=1, 2 or 3.

[0112] 2. (6-TFBIm)2(M)nPbnI 3n+1 Single crystal material testing:

[0113] The single crystal structure of this embodiment 3 is as follows Figure 6 As shown, it can be seen that 6-trifluoromethylbenzimidazole iodide (6-TFBImI) finally forms a two-dimensional perovskite single crystal structure (n=1). Figure 7 The comparison between the single crystal X-ray diffraction spectrum (XRD) and the fitted X-ray diffraction spectrum (XRD) shows that the two-dimensional perovskite single crystal (n=1) was successfully synthesized in Example 3. The single crystal structure information is shown in Table 2.

[0114] Table 2 Single crystal structure information

[0115]

[0116] Example 4

[0117] 1. This embodiment provides a method for preparing a low-dimensional / three-dimensional perovskite film. The specific process is as follows: Figure 8 As shown:

[0118] (1) Dissolving lead iodide (PbI2) in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a molar concentration ratio of 9.5:0.5, and heating the solution at 60°C on a mixer until the solid is completely dissolved, thereby obtaining a lead iodide (PbI2) precursor solution with a concentration of 1.3 M; spin coating the prepared PbI2 precursor solution on a glass substrate at a speed of 1500 rpm / 30 s to obtain a PbI2 thin film, and annealing on a hot plate at 70°C for 1 min to form a PbI2 layer;

[0119] (2) dissolving 60 mg of formamidine iodide (FAI) and 14 mg of methylammonium chloride (MACl) in 1 mL of isopropanol IPA solvent and stirring until dissolved to obtain an organic halide precursor solution; then spin coating the organic halide precursor solution on the PbI2 layer at 1500 rpm / 30 s to obtain an organic halide film, annealing at 150° C. for 15 min to obtain an organic halide layer, and the organic halide reacts with lead iodide (PbI2) to obtain a 3D perovskite film;

[0120] (3) On the basis of the 3D perovskite film, BIZI, 6-MeBImI, and 6-TFBImI were dissolved in isopropanol, respectively, and the resulting solutions were spin-coated on the 3D perovskite film by spin coating. The iodide of benzimidazole or its derivatives therein combined with the residual PbI2 on the 3D film, and finally spontaneously formed a low-dimensional / three-dimensional perovskite film (α-FAPbI3 perovskite film).

[0121] 2. Low-dimensional / three-dimensional perovskite film testing:

[0122] (1) By Fig. 9 It can be seen from the PL graph that the photoluminescence of the 3D perovskite film modified by the three molecules is enhanced, indicating that the non-radiative recombination of the modified film is reduced, which is beneficial to the transmission of carriers.

[0123] (2) From Fig.10 From the XRD patterns, it can be seen that the films treated with BIZI, 6-MeBImI, and 6-TFBImI all have low-dimensional peaks before 10°, which are respectively Figure 3 , 5 Compared with 7, the formation of the corresponding low-dimensional perovskite phase is proved, and the crystallinity of the film is increased after modification by BIZI, 6-MeBImI and 6-TFBImI, among which the crystallinity increase effect of the film after 6-TFBImI modification is more obvious, indicating that its modification effect is better.

[0124] (3) Fig.11 As shown in the UV-vis absorption spectrum, it shows that the absorbance of the film increases after treatment, which is more conducive to the transmission of carriers.

[0125] (4) By Fig.12 , 13 , 14, and 15 show that linear 1D perovskite is generated on the films modified with BIZI and 6-MeBImI, while layered 2D perovskite is generated on the films modified with 6-TFBImI. The grain size of the perovskite is also larger than that of the 3D perovskite film, indicating that 6-TFBImI modification is beneficial to increase the size of the perovskite grains and form a 2D phase perpendicular to the 3D perovskite, which is beneficial to the transport of carriers.

[0126] (5) By Figure 16-1 , 16-2 , 16-3, and 16-4 show that the hydrophobicity of the films modified with the three molecules is improved. It is particularly noteworthy that the water contact angle of the 6-TFBImI modified film can reach 94°, which significantly improves the hydrophobicity compared with other films.

[0127] Example 5

[0128] 1. This embodiment provides a method for preparing a LD / 3D heterojunction perovskite solar cell. The above characterization shows that the 6-TFBImI modification has a better effect. Thus, a 6-TFBImI modified perovskite solar cell is prepared. The device structure is as follows: Fig.17 As shown, the specific steps are as follows:

[0129] (1) The ITO substrate was ultrasonically cleaned for 15 min using detergent, deionized water, ethanol, and isopropyl ketone, respectively. After cleaning, it was blown dry with nitrogen and placed in a UV ozone cleaning machine for 20 min.

[0130] (2) A SnO2 aqueous solution was prepared with a volume ratio of 1:6, filtered, and spun at a speed of 4000 r / min for 30 s to coat the SnO2 electron transport layer on the ITO substrate. The substrate was then moved to a heating table at 150°C and annealed for 30 min. After cooling, the substrate was placed in a UV ozone cleaning machine for 10 min.

[0131] (3) Weigh lead iodide (PbI2) and dissolve it in a solvent of DMF:DMSO = 9.5:0.5. Place the solution on a mixer and heat it at 60°C until the solid is completely dissolved to obtain a lead iodide (PbI2) precursor solution with a concentration of 1.3 M.

[0132] 60 mg of formamidine iodide (FAI) and 14 mg of methylammonium chloride (MACl) were dissolved in 1 mL of IPA solvent and stirred until dissolved to obtain an organic halide precursor solution.

[0133] (4) In a glove box filled with nitrogen, filter and purify the PbI2 precursor solution, use a pipette to absorb the PbI2 precursor solution, and spin-coat it on the SnO2 layer to obtain a PbI2 thin film at a rotation speed of 1500 r / min for 30 s. Anneal the obtained PbI2 thin film at 70°C. The annealing process parameters are: annealing temperature of 70°C and annealing time of 1 min.

[0134] (5) Spin coating the organic halide precursor solution on the lead iodide film at a rotation speed of 1500 r / min for 30 seconds, and annealing in air at a temperature of 150° C. (humidity of 30-40%) for 15 minutes to obtain a 3D perovskite film.

[0135] (6) Then, an organic solution containing 6-TFBImI was spin-coated on the 3D perovskite film at a rotation speed of 5000 r / min for 30 s.

[0136] (7) Weigh 520 mg of lithium bis(trifluoromethanesulfonyl)imide and dissolve it in 1 mL of acetonitrile to prepare a lithium bis(trifluoromethanesulfonyl)imide solution as a hole transport layer solution; take 72.3 mg of Spiro-OMeTAD and dissolve it in 1 mL of chlorobenzene, add 28.8 μL of 4-tert-butylpyridine solution and 17.5 μL of lithium bis(trifluoromethanesulfonyl)imide solution as additives; use a pipette to draw 35 uL of solar cell hole transport layer spin coating liquid precursor solution, set the speed to 3000 r / min, and the time to 30 s to spin coat the hole transport layer.

[0137] (8) When the vacuum degree is less than 1×10 -5 Under Tor, Metal Ag was evaporated on the hole transport layer at a speed of 100 nm to form a 100 nm Ag electrode, thereby obtaining the LD / 3D heterojunction perovskite solar cell of this embodiment 5.

[0138] 2. A 3D perovskite solar cell was prepared as a control group. The preparation method thereof was based on omitting step (6). The other steps were the same as the above-mentioned LD / 3D heterojunction perovskite solar cell preparation method.

[0139] 3. Test of the 3D perovskite solar cell of the control group and the LD / 3D heterojunction perovskite solar cell of Example 5:

[0140] Depend on Fig.18 From the comparison chart of photoelectric conversion efficiency, it can be seen that the efficiency of 6-TFBIm-modified LD / 3D heterojunction perovskite solar cells has been significantly improved.

[0141] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A low-dimensional perovskite single crystal, characterized in that: Its chemical structure is: (R)2(M) n Pb n I 3n+1 ; In the formula, R is the iodide of benzimidazole or its derivative; M is CH3NH3, CH(NH2)2 or Cs; and n is the number of inorganic layers.

2. The low-dimensional perovskite single crystal according to claim 1, characterized in that: The benzimidazole derivative is 6-methylbenzimidazole or 6-trifluoromethylbenzimidazole.

3. The method for preparing the low-dimensional perovskite single crystal according to claim 1 or 2, characterized in that: include: After the mixed solution of the lead source, hydroiodic acid and hypophosphorous acid is stirred and reacted at 100-120° C. for 1-2 hours, the iodide of benzimidazole or its derivative is continuously added, and the stirring reaction is continued for 1-2 hours. During the cooling process of the system after the reaction is completed, crystals are precipitated, and the crystals are obtained to obtain the low-dimensional perovskite single crystal.

4. The method for preparing a low-dimensional perovskite single crystal according to claim 3, characterized in that: The lead source is lead oxide, lead iodide or lead acetate; the iodide is CH3NH3I, CH(NH2)2I or CsI; in terms of molar ratio, the lead source: benzimidazole or its derivative: iodide: HI: H3PO2 = n: 0.5: n: 2n: 2n, n = 1, 2 or 3; and / or, The method for preparing the iodide of benzimidazole or its derivative comprises: Benzimidazole or its derivative is reacted with hydroiodic acid having a mass content of 50-60% at room temperature with stirring for 2-3 hours in a stoichiometric molar ratio of 1:1 to obtain the iodide of the benzimidazole or its derivative.

5. A low-dimensional / three-dimensional perovskite film, characterized in that: The film structure is: Based on the three-dimensional perovskite film, the low-dimensional perovskite single crystal according to claim 1 or 2 is formed on the surface of the three-dimensional perovskite film.

6. The method for preparing the low-dimensional / three-dimensional perovskite film according to claim 5, characterized in that: include: Preparation of three-dimensional perovskite films; The iodide of benzimidazole or its derivative is prepared into an organic solution, and the organic solution is spin-coated on the three-dimensional perovskite film. The iodide of benzimidazole or its derivative spontaneously reacts with the residual PbI2 on the three-dimensional perovskite film to form a low-dimensional perovskite single crystal, thereby obtaining the low-dimensional / three-dimensional perovskite film.

7. The method for preparing a low-dimensional / three-dimensional perovskite film according to claim 6, characterized in that: The method for preparing a three-dimensional perovskite film comprises: Dissolving lead iodide in a first organic solvent to obtain a lead iodide precursor solution; dissolving formamidine iodide and methylammonium chloride in a second organic solvent to obtain an organic halide precursor solution; The lead iodide precursor solution is spin-coated on the substrate and then annealed at 60-75° C. for 1-3 minutes to obtain a lead iodide film. The organic halide precursor solution is spin-coated on the lead iodide film and then annealed at 140-160° C. for 10-20 minutes to obtain the three-dimensional perovskite film.

8. The method for preparing a low-dimensional / three-dimensional perovskite film according to claim 6 or 7, characterized in that: The iodide of the benzimidazole or its derivative is prepared into the organic solution by using an organic solvent; The first organic solvent is a mixed solvent with a mass ratio of DMF:DMSO=9.5:0.5, and the concentration of the lead iodide precursor solution is 1.3M; The second organic solvent is isopropanol; The organic solvent is one of isopropanol and N,N-dimethylformamide or a mixed solvent of the two.

9. A perovskite solar cell, characterized in that: include: A light absorbing layer, wherein the light absorbing layer is composed of the low-dimensional / three-dimensional perovskite film according to claim 5.

10. The method for preparing a perovskite solar cell according to claim 9, characterized in that: include: A transparent conductive substrate is prepared, an electron transport layer or a hole transport layer is prepared on the transparent conductive substrate, a light absorbing layer is prepared on the electron transport layer or the hole transport layer according to the preparation method of the low-dimensional / three-dimensional perovskite film according to any one of claims 6 to 8, and a metal electrode is vacuum evaporated after the electron transport layer or the hole transport layer is prepared on the light absorbing layer to obtain the perovskite solar cell.

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