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

Abstract

The present disclosure relates to a low-dimensional perovskite single crystal, a low-dimensional / three-dimensional perovskite film, a perovskite solar cell and a preparation method, the low-dimensional perovskite single crystal is synthesized by using an organic spacer molecule benzimidazole or a derivative thereof, thereby widening the variety range of low-dimensional perovskite; meanwhile, the low-dimensional perovskite single crystal is applied to three-dimensional perovskite material, the three-dimensional perovskite material is modified, a low-dimensional / three-dimensional perovskite film with higher crystallinity and stronger hydrophobicity is prepared, the low-dimensional / three-dimensional perovskite film is used as a light-absorbing layer of a perovskite solar cell, and 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 material, in particular to three-dimensional perovskite, low-dimensional / three-dimensional perovskite material, perovskite solar cell and a preparation method thereof. BACKGROUND

[0002] As a new type of photoelectric material, the photoelectric conversion efficiency of perovskite solar cell has been improved from 3.9% when it was discovered in 2009 to 26.1%, which is comparable to the efficiency of commercialized crystalline silicon solar cells. Low-dimensional (LD) perovskite provides an exciting way to explore stable perovskite solar cells (PSCs). Low-dimensional (LD) perovskite includes zero-dimensional (0D), one-dimensional (1D) and two-dimensional (2D) perovskite, among which one-dimensional (1D) and two-dimensional (2D) perovskite are more widely studied than zero-dimensional (0D) perovskite. One-dimensional (1D) perovskite has a linear or tubular structure; two-dimensional (2D) perovskite has a layered structure, which is obtained by introducing large-size organic ligands into three-dimensional (3D) perovskite material to shear it into two-dimensional (2D) material along a certain specific axis. According to the difference in molecular structure of organic ligands, 2D perovskite structure is divided into Ruddlesden-Popper (RP), Dion-Jacobson (DJ) and Alternating-cation interlayer (ACI) three structures, and the chemical structural 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-size monoamine organic cation, R' is a large-size diamine organic cation, and R'' is a guanidinium cation (GA + ), and n represents the number of adjacent organic layers of metal halide octahedron [BX6] 4- . As can be seen, low-dimensional perovskite structure has diversity. At present, the variety and application research of known low-dimensional perovskite are still relatively few, so it is necessary to further develop new low-dimensional spacer organic molecules to expand the variety and application research range of low-dimensional perovskite.

[0003] As for three-dimensional perovskite, it is sensitive to water, which further affects the energy conversion efficiency of PSCs, so it is expected to increase the hydrophobicity of three-dimensional perovskite to obtain three-dimensional perovskite solar cells with high energy conversion efficiency, which has research significance. SUMMARY

[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 that the hydrophobicity of three-dimensional perovskites affects the energy conversion efficiency of three-dimensional perovskite solar cells.

[0005] The core of the method disclosed in the present invention 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 film surface 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 the chemical structural formula:

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

[0008] In the formula, R is an 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, the 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 derivatives comprises:

[0014] Benzimidazole or its derivative is reacted with hydroiodic acid having a mass content of 50-60% at a stoichiometric molar ratio of 1:1 under stirring at room temperature for 2-3 hours 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 a 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 obtained is 1.3M;

[0025] The second organic solvent is isopropyl alcohol;

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

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

[0028] The light absorbing layer is composed of the above-mentioned low-dimensional / three-dimensional perovskite film.

[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 above-mentioned low-dimensional / three-dimensional perovskite film preparation method, 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 specifically synthesized using 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. 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 accompanying drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and, together with the specification, are used to explain the technical solutions of the present disclosure.

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

[0036] Figure 3 1 is 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) pattern;

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

[0038] Figure 51 is a 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) pattern;

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

[0040] Figure 7 1 is 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 the fitted X-ray diffraction spectrum (XRD) pattern;

[0041] Figure 8 This is a flow chart for preparing a low-dimensional / three-dimensional heterojunction perovskite film according to Example 4;

[0042] Figure 9 1 is a photoluminescence spectrum (PL) of the low-dimensional / three-dimensional heterojunction perovskite film of Example 4;

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

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

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

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

[0047] Figure 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] Figure 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 、 16-2Fig. 16-3, 16-4 are the corresponding water contact angle diagrams of low-dimensional / three-dimensional heterojunction perovskite thin film with three-dimensional perovskite thin film, benzimidazole (BIZ) modification, 6-methylbenzimidazole (6-MeBIm) modification, 6-trifluoromethylbenzimidazole (6-TFBIm) modification, respectively;

[0050] Figure 17 Fig. 17 is a schematic diagram of perovskite solar cell device structure of Example 5;

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

[0052] The present disclosure is described below based on examples, but it is worth noting that the present disclosure is not limited to these examples. In the following detailed description of the present disclosure, some specific details are described in detail. However, those skilled in the art can also fully understand the present disclosure without detailed description of the parts.

[0053] In addition, unless the context clearly requires otherwise, the terms "comprise", "comprising", and the like in the specification and claims are to be construed as having an inclusive, but not exclusive, meaning; that is, the process, method, object or apparatus that "comprises", "comprising", or "includes" something are not limited to the steps, processes, objects, members, or apparatuses that "comprise", "comprising" or "include" only those elements but can also "comprise" or "include" other elements not expressly listed or inherent to such process, method, object or apparatus.

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

[0055] The method for preparing low-dimensional perovskite single crystals according to the embodiments of the present disclosure comprises the following steps:

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

[0057] The benzimidazole or its derivative is stirred with hydriodic acid with a mass content of 50-60% at room temperature in a stoichiometric molar ratio of 1:1 for 2-3h to obtain the iodide of benzimidazole or its derivative.

[0058] In a specific embodiment, the benzimidazole or its derivative is benzimidazole, 6-methylbenzimidazole and 6-trifluoromethylbenzimidazole, respectively. The molecular structure thereof is shown in Figure 1-1 、 1-2 1-3.

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

[0060] The mixed solution of the lead source, hydroiodic acid, and hypophosphorous acid is stirred and reacted at 100-120° C. for 1-2 hours, and then the iodide of benzimidazole or its derivative is added and the stirring reaction is continued for 1-2 hours. During the cooling process of the system after the reaction, crystals are precipitated and 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 an 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 one 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 according to the embodiment of the present disclosure comprises the following steps:

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

[0067] (1) 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.

[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 isopropyl alcohol.

[0069] (2) spin coating a lead iodide precursor solution on a substrate to obtain a lead iodide film, annealing the film at 60-75°C for 1-3 minutes to form a lead iodide layer; continuing to spin coating an organic halide precursor solution on the lead iodide layer to obtain an organic halide film, annealing the film at 140-160°C for 10-20 minutes to form an organic halide layer. In the above process, the organic halide reacts with lead iodide (PbI2) to form a 3D perovskite film, which 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 spontaneously reacts 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 using an organic solvent; the organic solvent is one of isopropyl alcohol and N,N-dimethylformamide, or a mixture of the two.

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

[0074] 1. Prepare a transparent conductive substrate and 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 one 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-bis(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 the resultant solution 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 spacer molecules 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 reacted in a stoichiometric molar ratio at room temperature with stirring for 2-3 hours 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), 50-60% by weight hydroiodic acid (HI aqueous solution), and 50-55% by weight hypophosphorous acid (H3PO2) aqueous solution were mixed and stirred to form a uniform solution, and the mixture was stirred and reacted at 100-120°C for 0.5 hours. Then, iodide (CH(NH2)2I) was added to the above solution, and then BIZI solid was added. After the reaction, the mixture was stirred and reacted at 100-120°C for 2 hours. The solution was placed on a hot plate and cooled at 3°C / hour to room temperature. Crystals precipitated during the cooling process. Finally, the mixture was washed and filtered to obtain (BIZ)2(M). 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] 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, where 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 Comparison of the single crystal X-ray diffraction spectrum (XRD) pattern with the fitted X-ray diffraction spectrum (XRD) pattern shows that this embodiment 1 successfully synthesized a one-dimensional (1D) perovskite single crystal (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 in water) with a mass content of 50-60% are reacted in a stoichiometric molar ratio at room temperature with stirring for 3 hours 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), 50-60% by mass hydroiodic acid (HI aqueous solution), and 50-55% by mass hypophosphorous acid (H3PO2) aqueous solution were mixed and stirred to form a uniform solution (the solvent here is N,N-dimethylformamide), and the temperature was controlled at 100-120°C and stirred for 0.5 hours. Then, iodide (CH(NH2)2I) was added to the above solution, and then 6-MeBImI solid was added. After the reaction, the temperature was controlled at 100-120°C and stirred for 2 hours. The solution was placed on a hot plate and cooled to room temperature at 3°C / h. Crystals precipitated during the cooling process. Finally, after washing and filtration, (6-MeBIm)2(M)nPbnI was 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 provided, the amount of HI used is measured by the HI provided, the amount of H3PO2 aqueous solution used is measured by the H3PO2 provided, 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 Comparing the single crystal X-ray diffraction spectrum (XRD) pattern with the fitted X-ray diffraction spectrum (XRD) pattern, it can be found that this embodiment 2 successfully synthesized a one-dimensional (1D) perovskite single crystal. 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 crystals 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 50-60% by weight hydroiodic acid (HI aqueous solution) 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), 50-60% by weight hydroiodic acid (HI aqueous solution), and 50-55% by weight hypophosphorous acid (H3PO2) aqueous solution were mixed and stirred to form a uniform solution, and the mixture was stirred and reacted at 100-120°C for 0.5 h. Then, iodide (CH(NH2)2I) was added to the solution, and then 6-TFBImI solid was added. After the mixture was stirred and reacted at 100-120°C for 2 h, the temperature was controlled at 3°C / h to room temperature. Crystals precipitated during the cooling process, and the mixture was washed and filtered to obtain (6-TFBIm)2(M)nPbnI. 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] 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 Example 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 Comparison of the single crystal X-ray diffraction (XRD) pattern with the fitted X-ray diffraction (XRD) pattern demonstrates that a 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 low-dimensional / three-dimensional perovskite films. The specific process is as follows: Figure 8 As shown:

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

[0119] (2) 60 mg of formamidine iodide (FAI) and 14 mg of methylammonium chloride (MACl) were dissolved in 1 mL of isopropyl alcohol (IPA) solvent and stirred until dissolved to obtain an organic halide precursor solution; the organic halide precursor solution was then spin-coated on the PbI2 layer at 1500 rpm / 30 s to obtain an organic halide film, which was annealed at 150°C for 15 min to obtain an organic halide layer, and the organic halide reacted with lead iodide (PbI2) to obtain a 3D perovskite film;

[0120] (3) Based on 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. The iodide of benzimidazole or its derivatives 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 Figure 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 transport of carriers.

[0123] (2) From Figure 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 , 7, which proves the formation of the corresponding low-dimensional perovskite phase, and the crystallinity of the film increased after modification by BIZI, 6-MeBImI, and 6-TFBImI, among which the crystallinity of the film increased more significantly after modification by 6-TFBImI, indicating that its modification effect is better.

[0124] (3) Figure 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 Figure 12 、 13 From the SEM images of the corresponding films, it can be seen 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 is significantly improved compared with other films.

[0127] Example 5

[0128] 1. This embodiment provides a method for preparing a LD / 3D heterojunction perovskite solar cell. Based on the above characterization, it is concluded that 6-TFBImI modification has better effect. Thus, a 6-TFBImI modified perovskite solar cell is prepared. The device structure is as follows: Figure 17 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 then spin-coated on the ITO substrate at a speed of 4000 r / min for 30 s. 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 nitrogen-filled glove box, the PbI2 precursor solution was filtered and purified, and the PbI2 precursor solution was aspirated with a pipette and spin-coated on the SnO2 layer to obtain a PbI2 thin film at a rotation speed of 1500 r / min for 30 s. The obtained PbI2 thin film was annealed at 70°C. The annealing process parameters were: annealing temperature of 70°C, annealing time of 1 min.

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

[0135] (6) The organic solution containing 6-TFBImI was then 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 μL 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 conditions, Metal Ag was evaporated on the hole transport layer at a speed of , to form a 100 nm Ag electrode, thereby obtaining the LD / 3D heterojunction perovskite solar cell of Example 5.

[0138] 2. Prepare 3D perovskite solar cells as a control group. The preparation method is based on omitting step (6). The other steps are the same as the above-mentioned LD / 3D heterojunction perovskite solar cell preparation method.

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

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

[0141] While various embodiments of the present disclosure have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technical improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A low-dimensional perovskite single crystal, characterized in that Its chemical structure is: (BIZ)2 (M) n-1 Pb n I 3n+1 , low-dimensional perovskite single crystal C prepared based on 6-methylbenzimidazole as spacer molecule 14 H 23 N4O2PbI3 and low-dimensional perovskite single crystal C prepared based on 6-trifluoromethylbenzimidazole as spacer molecule 16 H 12 One or more types of F6N4PbI4; In the formula, BIZ is benzimidazole; the 6-methylbenzimidazole and 6-trifluoromethylbenzimidazole are benzimidazole derivatives; M is CH3NH3, CH(NH2)2 or Cs; and n is the number of inorganic layers.

2. The method for preparing the low-dimensional perovskite single crystal according to claim 1, characterized in that: include: The mixed solution of the lead source, hydroiodic acid, and hypophosphorous acid is stirred and reacted at 100-120° C. for 1-2 hours, and then the iodide of benzimidazole or its derivative is 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.

3. The method for preparing a low-dimensional perovskite single crystal according to claim 2, wherein: 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, where n = 1, 2 or 3.

4. The method for preparing a low-dimensional perovskite single crystal according to any one of claims 2 or 3, characterized in that: The method for preparing the iodide of benzimidazole or its derivatives comprises: Benzimidazole or its derivative is reacted with 50-60% by mass of hydroiodic acid at a stoichiometric molar ratio of 1:1 under stirring at room temperature for 2-3 hours 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 a three-dimensional perovskite film, the low-dimensional perovskite single crystal according to claim 1 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 a 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 thin 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 obtained is 1.3 M; The second organic solvent is isopropyl alcohol; The organic solvent is one of isopropyl alcohol 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 thin 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 after the electron transport layer or the hole transport layer is prepared on the light absorbing layer, a metal electrode is vacuum evaporated to obtain the perovskite solar cell.

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