A preparation method of a quasi-two-dimensional perovskite film capable of effectively improving carrier transport

Abstract

This invention discloses a method for preparing quasi-two-dimensional perovskite thin films that effectively improve carrier transport, relating to the field of perovskite thin film preparation technology. The method includes: S1, preparing raw materials; S2, preparing a perovskite precursor solution: the raw materials in step S1 are prepared according to a molar ratio of PEAI:MAI:PbI2:CBH = 2:3:4:x; S3, cleaning an ITO substrate; S4, first preheating the ITO substrate treated in step S3 on a hot plate, transferring it to a spin coater, adding the perovskite precursor solution prepared in step S2, spin-coating at a uniform speed, and then annealing on the hot plate to obtain the sample; after reaching room temperature, adding chlorobenzene solution (PC)... 61 The process involves spin-coating the Ag electrode at a uniform speed (BM) and finally thermally evaporating it to obtain a thin-film device. This invention improves the crystallization state of the 3D phase in the two-dimensional perovskite thin film by adding CBH to the precursor solution, increasing the 3D phase content and thus promoting carrier transport within the film and carrier extraction by the transport layer, thereby obtaining a high-performance self-driven photodetector.

Description

Technical Field

[0001] This invention relates to the field of perovskite thin film preparation technology, and more specifically to the field of methods for preparing quasi-two-dimensional perovskite thin films that effectively improve carrier transport. Background Technology

[0002] Quasi-two-dimensional perovskites possess better stability and lower ion migration characteristics than three-dimensional perovskite materials, making them highly promising for applications in optoelectronic thin-film devices. However, quasi-two-dimensional perovskite films prepared by solution methods are not pure phases but consist of multiple phases; this irregular multiphase distribution restricts charge carrier transport and thus affects the performance of thin-film devices. Therefore, improving charge transport in thin films to enhance device performance is a research hotspot for quasi-two-dimensional perovskite materials.

[0003] Current research on improving charge transport in quasi-two-dimensional perovskite thin films mainly focuses on two aspects. First, it involves controlling the grain growth orientation of the quasi-two-dimensional perovskite thin film to align with the charge collection direction of the thin-film device. This creates a rapid charge transport channel along the charge collection direction, thereby improving the electrode's carrier collection efficiency. Second, it involves controlling the phase composition and distribution of the quasi-two-dimensional perovskite thin film to create a gradually changing compositional distribution along the charge collection direction. This generates a spontaneous built-in electric field along the charge collection direction, promoting electron and hole separation and further improving the electrode's carrier collection efficiency. Additionally, existing patents disclose the following technologies:

[0004] The patent with publication number CN113078267B and title "A Quasi-Two-Dimensional Perovskite Solar Cell Doped with Three-Dimensional Perovskite and Its Preparation Method" discloses the following: A quasi-two-dimensional perovskite solar cell doped with three-dimensional perovskite and its preparation method, the preparation method including the following steps: (1) preparation of precursor solution; (2) pretreatment of substrate; (3) spin coating of hole transport layer; (4) spin coating of electron transport layer and perovskite absorber layer; (5) spin coating of PEI modification layer and preparation of finished product. This invention can prepare a quasi-two-dimensional perovskite solar cell doped with three-dimensional perovskite by simply adding three-dimensional perovskite as an additive to a quasi-two-dimensional perovskite precursor solution via spin coating. The performance of this solar cell is significantly improved, especially the photovoltaic cell efficiency is increased by 41%, while effectively improving carrier extraction efficiency and reducing internal defect state density, meeting the current urgent demand for perovskite solar cells.

[0005] Patent publication number CN115594413A, entitled "A Method for Preparing Sodium-Doped Two-Dimensional Perovskite Thin Films," discloses the following: A method for preparing sodium-doped two-dimensional perovskite thin films, comprising the following steps: Cleaning of ITO conductive glass indium tin oxide: Immersing the ITO conductive glass in water with detergent for 10 minutes, then repeatedly rubbing the conductive surface 20 times with hands wearing rubber gloves to remove surface dust; subsequently, ultrasonically cleaning with acetone, deionized water, and anhydrous ethanol for 15 minutes each, and finally soaking in clean anhydrous ethanol for later use. This method for preparing sodium-doped two-dimensional perovskite thin films, through Na ion doping modification, significantly improves the film quality of two-dimensional perovskite (BA)₂MA₃Pb₄I₁₃, enhancing both density and uniformity.

[0006] Patent publication number CN114540023A, entitled "Method for Controlling the Phase Purity of Quasi-Two-Dimensional Perovskite Thin Films," discloses the following: A method for controlling the phase purity of quasi-two-dimensional perovskite thin films, belonging to the field of chemical materials technology, involves dissolving a quasi-two-dimensional perovskite precursor salt in a polar solvent to obtain a precursor solution; adding an organic small molecule ester at an appropriate concentration to an antisolvent to obtain an organic small molecule ester additive; dropping the precursor solution onto a substrate and spin-coating it at a uniform speed; during spin-coating, dropping the organic small molecule ester additive onto the precursor solution to form a film; and then heating and annealing to obtain a quasi-two-dimensional perovskite thin film. Compared with traditional control techniques, the preparation process of this invention using organic small molecule ester additives to control the phase purity of quasi-two-dimensional perovskite thin films is simple to operate, not limited by equipment and experimental conditions, uses inexpensive materials, and has high reproducibility.

[0007] The aforementioned patents all improve carrier transport in quasi-two-dimensional perovskite thin films, thereby enhancing the performance of corresponding thin-film devices. However, the performance of quasi-two-dimensional perovskite thin-film devices is still lower than that of their corresponding three-dimensional perovskites. Therefore, new strategies are needed to improve the carrier transport performance of quasi-two-dimensional perovskites and overcome the performance bottleneck of these devices. Summary of the Invention

[0008] The purpose of this invention is to address the technical problem that the carrier transport of existing two-dimensional perovskite films is lower than that of three-dimensional perovskites. This invention provides a method for preparing quasi-two-dimensional perovskite films that effectively improves carrier transport.

[0009] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0010] A method for preparing quasi-two-dimensional perovskite thin films that effectively improve carrier transport includes the following steps:

[0011] S1. Prepare raw materials: Prepare lead iodide (PbI2), phenylethyl ammonium iodide (PEAI), methyl ammonium iodide (MAI), N,N-dimethylformamide (DMF) and carbazide (CBH);

[0012] S2. Preparation of perovskite precursor solution: The raw materials in step S1 are prepared according to the molar ratio of PEAI:MAI:PbI2:CBH = 2:3:4:x to obtain PEA2MA3Pb4I 13 In addition to preparing a perovskite precursor solution, a DMF solution with a Pb concentration of 0.4 M was also prepared.

[0013] S3, ITO substrate cleaning: Clean the ITO substrate and transfer the cleaned ITO substrate to a nitrogen glove box.

[0014] S4. Thin Film Device Fabrication: First, the ITO substrate treated in step S3 is placed on a hot plate for preheating, then transferred to a spin coater, and PEA2MA3Pb4I prepared in step S2 is added dropwise. 13 The perovskite precursor solution was spin-coated at a uniform speed, and then annealed on a hot stage to obtain the sample.

[0015] After cooling the sample to room temperature, add PC dropwise. 61 A chlorobenzene solution of BM was spin-coated at a uniform speed, and finally the Ag electrode was thermally evaporated to obtain a thin film device.

[0016] Further, in step S1, the purity of lead iodide is 96.0%–99.6%, the purity of phenylethyl iodide is 98.0%–99.6%, the purity of methyl iodide is 98.0%–99.6%, the purity of N,N-dimethylformamide is 98.0%–99.9%, and the purity of carbazide is 95%–99%.

[0017] Specifically, the preferred purities for the above-mentioned raw material purity ranges are as follows: lead iodide (PbI2) with a purity of 99.5%, phenylethyl ammonium iodide (PEAI) with a purity of 99.5%, methyl ammonium iodide (MAI) with a purity of 99.5%, N,N-dimethylformamide (DMF) with a purity of 99.9%, and carbazide (CBH) with a purity of 97%.

[0018] Further, in step S2, x is set to 0, 0.5%, 1%, 1.5%, and 2%, respectively, and the resulting thin-film devices are denoted as C0, C10, C20, C30, C40, C50, C60, C70, C80, C9 ... 0.5 C1, C 1.5 And C2.

[0019] Further, in step S3, when cleaning the ITO substrate, it is ultrasonically cleaned with deionized water, acetone, and ethanol for 15-22 minutes respectively, then dried with a nitrogen gun, treated with air plasma for 8-12 minutes before use, and then the ITO substrate is transferred to a nitrogen glove box.

[0020] Further, in step S4, the ITO substrate treated in step S3 is first placed on a hot plate for preheating at a temperature of 105℃~115℃ for 3min~7min. Then, it is transferred to a spin coater, and 50~65μL of the PEA2MA3Pb4I prepared in step S2 is added. 13 The perovskite precursor solution was spin-coated at a constant speed of 4500 rpm to 5500 rpm for 25 to 35 seconds, and then annealed on a hot plate to obtain the sample.

[0021] Further, in step S4, the ITO substrate treated in step S3 is first placed on a hot plate for preheating at 100°C for 5 minutes. Then, it is transferred to a spin coater, and 60 μL of the PEA2MA3Pb4I prepared in step S2 is added. 13 The perovskite precursor solution was spin-coated at a constant speed of 5000 rpm for 30 seconds, and then annealed on a hot plate to obtain the sample.

[0022] Further, in step S4, after cooling the sample to room temperature, PC is added dropwise. 61 The chlorobenzene solution of BM was spin-coated at a constant speed of 1500 rpm to 2500 rpm for 35 s to 45 s, and finally the Ag electrode was thermally evaporated to obtain the thin film device.

[0023] Further, in step S4, after cooling the sample to room temperature, PC is added dropwise. 61 The chlorobenzene solution of BM was spin-coated at a constant speed of 2000 rpm for 40 seconds, and finally the Ag electrode was thermally evaporated to obtain the thin film device.

[0024] Furthermore, in step S4, PC 61 The mass concentration of BM's chlorobenzene solution is 18–22 mg / mL.

[0025] Furthermore, in step S4, PC 61 The mass concentration of BM's chlorobenzene solution is 20 mg / mL.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This invention improves the crystallization state of the 3D phase in a two-dimensional perovskite film by adding CBH to the precursor solution, increases the content of the 3D phase, and thus promotes carrier transport inside the film and the extraction of carriers by the transport layer, thereby obtaining a high-performance self-driven photodetector.

[0028] 2. Systematically study the interaction between additive molecules and perovskite, characterize the chemical interaction between specific functional groups in additive molecules and perovskite atoms, analyze its influence on the perovskite crystallization process, and thus guide the selection of additive molecules. Attached Figure Description

[0029] Figure 1 The graph shows the effect of CBH doping on the crystallization state and microstructure of the thin film before and after the doping process. Figure 1 (a) XRD patterns characterizing the structure and phase composition of C0 and C1 thin films. Figure 1 (b) shows the UV-Vis absorption spectra of the C0 and C1 thin film structures and phase compositions. Figure 1 (c) shows the steady-state photoluminescence spectra of the C0 and C1 thin film structures and phase compositions. Figure 1 (d) is an electron diffraction pattern of the C0 thin film. Figure 1 (g) is a selected electron diffraction photograph of the C1 thin film. Figure 1 (e, f) are high-resolution TEM images of the CO thin film. Figure 1 (h, i) is a high-resolution TEM image of the C1 thin film.

[0030] Figure 2 A graph showing the effect of CBH doping on the carrier transport properties of thin films. Figure 2 (a) Spin-coated PC 61 Transient absorption spectrum of CO thin film before BM, Figure 2 (b) Spin-coated PC 61 Transient absorption spectrum of BMC1 thin film, Figure 2 (c) Spin-coated PC 61 Transient fluorescence lifetime of CO thin film before BM, Figure 2 (d) is spin-coated PC 61 Transient fluorescence lifetime of C1 film after BM Figure 2 (e) represents the defect state density of C0 and C1 thin films. Figure 2 (f) shows the impedance spectra of the C0 and C1 thin films in the dark state;

[0031] Figure 3 This is a characterization diagram showing the change in crystallization of the precursor solution on a hot stage over time. Figure 3 (a) Photographs showing the changes in crystallization of C0 and C1 precursor solutions on a hot stage over time. Figure 3 (b) shows the infrared absorption spectra of C0, C1, and CBH. Figure 3 (c) XPS spectra of N1s, (d) Pb and (e) I.

[0032] Figure 4 The effect of CBH doping on the photoelectric properties of thin-film devices. Figure 4 (a) is a schematic diagram of the thin-film device structure. Figure 4 (b) shows the relationship between the dark current density of C0 and C1 thin films and the bias voltage. Inset: Schematic diagram of the change of current density over time at 0V. Figure 4 (c) is a schematic diagram showing the change of responsivity with wavelength. Figure 4 (d) is a schematic diagram showing the change of detectivity with wavelength.

[0033] Figure 5 This is a schematic diagram illustrating the effect of CBH doping on the stability of thin films and thin film devices. Figure 5 (a) shows the XRD patterns of C0 and C1 thin films. Figure 5 (b) shows the UV-Vis absorption spectra of the C0 and C1 films. Figure 5 (c) represents the contact angles of C0 and C1 films. Figure 5 (d) is a photograph of the surface of CO and C1 thin films after deionized water treatment. Figure 5 (e) shows the stability diagrams of C0 and C1 films. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0038] Example 1

[0039] This embodiment provides a method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport, comprising the following steps:

[0040] S1. Prepare raw materials: Prepare lead iodide (PbI2) with a purity of 96.0%, phenylethyl ammonium iodide (PEAI) with a purity of 98.0%, methyl ammonium iodide (MAI) with a purity of 98.0%, N,N-dimethylformamide (DMF) with a purity of 98.0%, and carbazide (CBH) with a purity of 95%.

[0041] S2. Preparation of perovskite precursor solution: The raw materials in step S1 are prepared according to the molar ratio of PEAI:MAI:PbI2:CBH = 2:3:4:x to obtain PEA2MA3Pb4I 13 In addition to preparing a perovskite precursor solution, a DMF solution with a Pb concentration of 0.4 M was also prepared.

[0042] S3. ITO substrate cleaning: When cleaning the ITO substrate, use deionized water, acetone and ethanol for ultrasonic cleaning for 15 minutes respectively, then blow it dry with a nitrogen gun. Before use, treat it with air plasma for 8 minutes, and then transfer the ITO substrate to a nitrogen glove box.

[0043] S4. Thin Film Device Fabrication: First, the ITO substrate treated in step S3 is placed on a hot stage for preheating at 105℃ for 3 minutes. Then, it is transferred to a spin coater, and 50 μL of the PEA2MA3Pb4I prepared in step S2 is added. 13 The perovskite precursor solution was spin-coated at a constant speed of 4500 rpm for 25 seconds, and then annealed on a hot plate to obtain the sample.

[0044] After cooling the sample to room temperature, PC with a mass concentration of 18 mg / mL was added dropwise. 61 The chlorobenzene solution of BM was spin-coated at a constant speed of 1500 rpm for 35 seconds, and finally the Ag electrode was thermally evaporated to obtain the thin film device.

[0045] Where x is set to 0%, 0.5%, 1%, 1.5%, and 2%, respectively, and the resulting thin-film devices are denoted as C0, C10, C20, and C30, respectively. 0.5 C1, C 1.5 And C2.

[0046] Example 2

[0047] This embodiment provides a method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport, comprising the following steps:

[0048] S1. Prepare raw materials: Prepare lead iodide (PbI2) with a purity of 99.6%, phenylethyl ammonium iodide (PEAI) with a purity of 99.6%, methyl ammonium iodide (MAI) with a purity of 99.6%, N,N-dimethylformamide (DMF) with a purity of 99.9%, and carbazide (CBH) with a purity of 99%.

[0049] S2. Preparation of perovskite precursor solution: The raw materials in step S1 are prepared according to the molar ratio of PEAI:MAI:PbI2:CBH = 2:3:4:x to obtain PEA2MA3Pb4I 13 In addition to preparing a perovskite precursor solution, a DMF solution with a Pb concentration of 0.4 M was also prepared.

[0050] S3. ITO substrate cleaning: When cleaning the ITO substrate, use deionized water, acetone and ethanol for ultrasonic cleaning for 22 minutes respectively, then blow it dry with a nitrogen gun. Before use, treat it with air plasma for 12 minutes, and then transfer the ITO substrate to a nitrogen glove box.

[0051] S4. Thin Film Device Fabrication: First, the ITO substrate treated in step S3 is placed on a hot plate for preheating at 115℃ for 7 minutes. Then, it is transferred to a spin coater, and 65 μL of the PEA2MA3Pb4I prepared in step S2 is added. 13 The perovskite precursor solution was spin-coated at a constant speed of 5500 rpm for 35 seconds, and then annealed on a hot plate to obtain the sample.

[0052] After cooling the sample to room temperature, PC with a mass concentration of 22 mg / mL was added dropwise. 61 The chlorobenzene solution of BM was spin-coated at a constant speed of 2500 rpm for 45 seconds, and finally the Ag electrode was thermally evaporated to obtain the thin film device.

[0053] Where x is set to 0%, 0.5%, 1%, 1.5%, and 2%, respectively, and the resulting thin-film devices are denoted as C0, C10, C20, and C30, respectively. 0.5 C1, C 1.5 And C2.

[0054] Example 3

[0055] This embodiment provides a method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport, comprising the following steps:

[0056] S1. Prepare raw materials: Prepare lead iodide (PbI2) with a purity of 99.5%, phenylethyl ammonium iodide (PEAI) with a purity of 99.5%, methyl ammonium iodide (MAI) with a purity of 99.5%, N,N-dimethylformamide (DMF) with a purity of 99.9%, and carbazide (CBH) with a purity of 97%.

[0057] S2. Preparation of perovskite precursor solution: The raw materials in step S1 are prepared according to the molar ratio of PEAI:MAI:PbI2:CBH = 2:3:4:x to obtain PEA2MA3Pb4I 13 Prepare a perovskite precursor solution, and also prepare a DMF solution with a Pb concentration of 0.4 M.

[0058] S3. ITO substrate cleaning: When cleaning the ITO substrate, use deionized water, acetone and ethanol for ultrasonic cleaning for 20 minutes respectively, then blow it dry with a nitrogen gun. Before use, treat it with air plasma for 10 minutes, and then transfer the ITO substrate to a nitrogen glove box.

[0059] S4. Thin Film Device Fabrication: First, the ITO substrate treated in step S3 is placed on a hot stage for preheating at 110℃ for 5 minutes. Then, it is transferred to a spin coater, and 60 μL of the PEA2MA3Pb4I2 prepared in step S2 is added. 13 The perovskite precursor solution was spin-coated at a constant speed of 5000 rpm for 30 seconds, and then annealed on a hot plate to obtain the sample.

[0060] After cooling the sample to room temperature, add PC at a concentration of 20 g / mL. 61 The chlorobenzene solution of BM was spin-coated at a constant speed of 2000 rpm for 40 seconds, and finally the Ag electrode was thermally evaporated to obtain the thin film device.

[0061] Where x is set to 1%, the thin film devices obtained are denoted as C1.

[0062] Comparative Example 1

[0063] The other steps and data are the same as in Example 3, except that the perovskite precursor solution does not contain carbazide (CBH) doping. That is, x is set to 0, and the resulting thin film devices are denoted as C0.

[0064] The effects of carbazide (CBH) doping on the crystallization state and microstructure of the thin film were studied using Example 3 and Comparative 1 as examples. Figure 1 The graph shows the effect of CBH doping on the crystallization state and microstructure of the thin film before and after the doping process. Figure 1 (a) XRD patterns characterizing the structure and phase composition of C0 and C1 thin films. Figure 1 (b) shows the UV-Vis absorption spectra of the C0 and C1 thin film structures and phase compositions. Figure 1 (c) shows the steady-state photoluminescence spectra of the C0 and C1 thin film structures and phase compositions. Figure 1 (d) is an electron diffraction pattern of the C0 thin film. Figure 1 (g) is a selected electron diffraction photograph of the C1 thin film. Figure 1(e, f) are high-resolution TEM images of the CO thin film. Figure 1 (h, i) is a high-resolution TEM image of the C1 thin film.

[0065] Figure 1 (a) shows that the full width at half maximum (FWHM) of the XRD diffraction peak decreased from 0.240 to 0.227, indicating that the addition of an appropriate concentration of carbazide (CBH) can improve the crystallization quality of the thin film. Figure 1 (b) Mid-UV-Vis absorption spectrum and Figure 1 (c) The steady-state PL spectra of the front and back sides show that the spectral intensity of the 3D phase in the C1 film is significantly enhanced in the wavelength range, indicating that the content of the 3D phase in the C1 film is increased. Figure 1 Electron diffraction characterization in (d) shows that the CO thin film exhibits diffraction ring characteristics and is polycrystalline. Figure 1 (g) Selective electron diffraction of the C1 film showed sharp diffraction spots, and diffraction rings with higher diffraction orders could be observed, indicating that the C1 film has better crystallinity and significantly improved crystal orientation. Figure 1 High-resolution TEM images of the top and bottom regions of the C0 film cross-section in (e, f) show that the C0 film has small grains, and 2D perovskite grains and unequal regions can be observed. Figure 1 In the high-resolution TEM images of the C1 thin film in (h, i), large-area, uniform, and uniformly oriented 3D phase lattice fringes were observed, indicating that the crystallization state and orientation of the 3D phase in the C1 thin film were significantly improved, and the content of the 3D phase was also increased. Appropriate concentrations of CBH doping can improve the crystallization state and content of the 3D phase in quasi-two-dimensional perovskite thin films.

[0066] Taking Example 3 and Comparison 1 as examples, the effect of CBH doping on the carrier transport performance of thin films is studied. Figure 2 A graph showing the effect of CBH doping on the carrier transport properties of thin films. Figure 2 (a) Spin-coated PC 61 Transient absorption spectrum of CO thin film before BM, Figure 2 (b) Spin-coated PC 61 Transient absorption spectrum of BMC1 thin film, Figure 2 (c) Spin-coated PC 61 Transient fluorescence lifetime of CO thin film before BM, Figure 2 (d) is spin-coated PC 61 Transient fluorescence lifetime of C1 film after BM Figure 2 (e) represents the defect state density of C0 and C1 thin films. Figure 2 (f) shows the impedance spectra of the C0 and C1 thin films in the dark state.

[0067] Figure 2 (a) and Figure 2(b) Transient absorption data indicate that the addition of CBH can accelerate the transfer of charge carriers from the 2D phase to the 3D phase, while PC 61 BM improves electron extraction efficiency by 1.54 times. TRPL reflects long-term carrier dynamics of thin films. Figure 2 (c) The average lifetimes of the C0 and C1 films in this example are 354.8 ns and 393.8 ns, respectively. This is because the addition of CBH improves the crystallinity of the films. After PCBM coating, Figure 2 (d) The transient fluorescence lifetimes of C0 and C1 films decreased to 331.4 and 284.2 ns, respectively, indicating that the charge at the C1 film / PCBM interface was generated faster. Figure 2 (e) The space charge confinement current measurement of the defect state densities of the C0 and C1 films is 1.02 × 10⁻⁶. 16 cm -3 and 3.59×10 15 cm -3 Impedance spectrum in the dark state ( Figure 2 (f) indicates that the C1 film has a larger recombination resistance, suggesting that nonradiative recombination in the C1 film is effectively suppressed. CBH doping significantly improves carrier transport performance in quasi-two-dimensional perovskite films.

[0068] Taking Example 3 and Comparative Example 1 as examples, the mechanism of CBH is discussed. By observing the changes in the crystallization of CO and C1 precursor solutions on the hot stage over time, Figure 3 This is a characterization diagram showing the change in crystallization of the precursor solution on a hot stage over time. Figure 3 (a) Photographs showing the changes in crystallization of C0 and C1 precursor solutions on a hot stage over time. Figure 3 (b) shows the infrared absorption spectra of C0, C1, and CBH. Figure 3 (c) XPS spectra of N1s, (d) Pb and (e) I.

[0069] Figure 3 (a) It can be clearly seen that C1 crystallization is slower. Figure 3 The infrared absorption spectrum in (b) shows that the characteristic C=O absorption peak was observed in the CBH and C1 films, but not in the C0 film. This indicates that CBH was successfully doped into the quasi-two-dimensional perovskite film. Furthermore, the shift of the characteristic C=O peak in the C1 film compared to that in CBH suggests a chemical interaction between CBH and the perovskite. Further characterization using XPS... Figure 3 (c)c The N1s spectrum also indicates that CBH was successfully doped into the C1 thin film. Figure 3 (d) shows that, compared to the C0 film, the position of the Pb 4f characteristic peak of the C1 film shifts towards the lower binding energy direction. This is because C=O in CBH acts as an electron donor and forms a complex with the lone pair electrons of Pb. Figure 3(e) The position of the I 3d5 characteristic peak also shifts towards lower binding energies. This is due to the chemical interaction between the amino groups and the I positions on the perovskite surface. Therefore, specific functional groups such as carbonyl and amino groups in CBH chemically interact with Pb and I in the perovskite, respectively, delaying the perovskite crystallization process and thus improving the crystallinity and content of the 3D phase in the film. This, in turn, improves the carrier transport and electron transport layer PC within the film. 61 BM's ability to extract electrons aims to improve the performance of optoelectronic thin-film devices.

[0070] Using Example 3 and Comparison 1 as examples, the influence of CBH doping on the photoelectric performance of thin film devices is verified. Figure 4 The effect of CBH doping on the photoelectric properties of thin-film devices. Figure 4 (a) is a schematic diagram of the thin-film device structure. Figure 4 (b) shows the relationship between the dark current density of C0 and C1 thin films and the bias voltage. Inset: Schematic diagram of the change of current density over time at 0V. Figure 4 (c) is a schematic diagram showing the change of responsivity with wavelength. Figure 4 (d) is a schematic diagram showing the change of detectivity with wavelength.

[0071] Figure 4 (a) shows a schematic diagram of a self-driven photodetector structure, which is ITO / PEA2MA3Pb4I 13 / PC 61 BM / Ag. Figure 4 (b) After CHB doping, the dark current is reduced by an order of magnitude, and the C1 thin film device exhibits lower noise at 0V. Figure 4 (c) Showing the responsivity as a function of wavelength under 0V bias, the responsivity of the C0 thin film device reaches a peak of 0.28AW at 610nm. -1 Compared to C0 thin-film devices, C1 thin-film devices exhibit increased responsivity across the entire wavelength range, with a peak responsivity reaching 0.4 AW. -1 . Figure 4 In (d), the detectivity varies with wavelength and its responsivity, with the peak detectivity of the C0 and C1 thin-film devices being 0.68 × 10⁻⁶ respectively. 12 Jones and 1.29×10 12 Jones. CBH doping significantly improves the detection performance of self-driven detectors.

[0072] Taking Example 3 and Comparative 1 as examples, the effect of CBH doping on the stability of thin films and thin film devices was studied. Figure 5 This is a schematic diagram illustrating the effect of CBH doping on the stability of thin films and thin film devices. Figure 5 (a) shows the XRD patterns of C0 and C1 thin films. Figure 5 (b) shows the UV-Vis absorption spectra of the C0 and C1 films. Figure 5 (c) represents the contact angles of C0 and C1 films. Figure 5 (d) is a photograph of the surface of CO and C1 thin films after deionized water treatment. Figure 5 (e) shows the stability diagrams of C0 and C1 films.

[0073] After 180 days of storage in air (room temperature, 20% relative humidity), the C0 film surface turned yellow, and the XRD pattern showed PEAI and PbI2 diffraction peaks. Simultaneously, the UV-Vis absorption showed a PEAI absorption peak, indicating that the degradation of the C0 film in air was due to the volatilization of the MAI component. The C1 film, however, remained dark brown after 180 days, and no new peaks appeared in the XRD and UV-Vis absorption, demonstrating the superior air stability of the C1 film. Figure 5 (c) The deionized water contact angles of the C0 and C1 films were 69.4° and 72.8°, respectively, in the first 10 seconds. However, as time increased, Figure 5 In (d), the C0 film is continuously decomposed by deionized water, while the deionized water on the surface of the C1 film does not change until it evaporates completely, indicating that the C1 film surface has better water stability. This is because the amino groups in the CBH molecules remaining in the film form hydrogen bonds with the I position on the surface of the perovskite film, increasing the hydrophobicity of the film surface. Figure 5 (e) Demonstrating the stability of thin-film devices, the C1 thin-film device showed no degradation after approximately 1000 hours, while the C0 thin-film device exhibited approximately 30% degradation, indicating that the C1 thin-film device exhibits better stability.

[0074] In summary, this invention improves the crystallization state of the 3D phase in a two-dimensional perovskite film by adding CBH to the precursor solution, thereby increasing the content of the 3D phase and promoting carrier transport within the film and carrier extraction by the transport layer, thus obtaining a high-performance self-driven photodetector.

Claims

1. A method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport, characterized in that, Includes the following steps: S1. Prepare raw materials: Prepare lead iodide, phenylethyl iodide, methyl iodide, N,N-dimethylformamide, and carbazide; S2. Preparation of perovskite precursor solution: The raw materials in step S1 are prepared according to the molar ratio of phenylethylamine iodide: methylamine iodide: lead iodide: carbazide = 2:3:4:x to obtain PEA2MA3Pb4I 13 Perovskite precursor solutions were prepared, with x set to 0, 0.5%, 1%, 1.5%, and 2%, respectively; in addition, a 0.4 M N,N-dimethylformamide solution with Pb concentration was prepared. S3, ITO substrate cleaning: Clean the ITO substrate and transfer the cleaned ITO substrate to a nitrogen glove box. S4. Thin Film Device Fabrication: First, the ITO substrate treated in step S3 is placed on a hot plate for preheating, then transferred to a spin coater, and PEA2MA3Pb4I prepared in step S2 is added dropwise. 13 The perovskite precursor solution was spin-coated at a uniform speed, and then annealed on a hot stage to obtain the sample. After cooling the sample to room temperature, add PC dropwise. 61 A chlorobenzene solution of BM was spin-coated at a uniform speed, and finally the Ag electrode was thermally evaporated to obtain a thin film device.

2. The method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport according to claim 1, characterized in that, In step S1, the purity of lead iodide is 96.0%~99.6%, the purity of phenylethyl iodide is 98.0%~99.6%, the purity of methyl iodide is 98.0%~99.6%, the purity of N,N-dimethylformamide is 98.0%~99.9%, and the purity of carbazide is 95%~99%.

3. The method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport according to claim 1, characterized in that, In step S3, when cleaning the ITO substrate, it is ultrasonically cleaned with deionized water, acetone, and ethanol for 15-22 minutes respectively, then dried with a nitrogen gun, and treated with air plasma for 8-12 minutes before use. Then the ITO substrate is transferred to a nitrogen glove box.

4. The method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport according to claim 1, characterized in that, In step S4, the ITO substrate treated in step S3 is first placed on a hot plate for preheating at a temperature of 105℃~115℃ for 3 to 7 minutes. Then, it is transferred to a spin coater, and 50~65 μL of the PEA2MA3Pb4I prepared in step S2 is added. 13 The perovskite precursor solution was spin-coated at a constant speed of 4500 rpm to 5500 rpm for 25 to 35 seconds, and then annealed on a hot plate to obtain the sample.

5. The method for preparing a quasi-two-dimensional perovskite thin film with effective improved carrier transport according to claim 4, characterized in that, In step S4, the ITO substrate treated in step S3 is first placed on a hot plate for preheating at 100 °C for 5 min. Then, it is transferred to a spin coater, and 60 μL of the PEA2MA3Pb4I prepared in step S2 is added. 13 The perovskite precursor solution was spin-coated at a constant speed of 5000 rpm for 30 seconds, and then annealed on a hot plate to obtain the sample.

6. The method for preparing a quasi-two-dimensional perovskite thin film with effective improved carrier transport according to claim 1, characterized in that, In step S4, after cooling the sample to room temperature, PC is added dropwise. 61 The chlorobenzene solution of BM was spin-coated at a constant speed of 1500 rpm to 2500 rpm for 35 to 45 seconds, and finally the Ag electrode was thermally evaporated to obtain the thin film device.

7. The method for preparing a quasi-two-dimensional perovskite thin film with effective improved carrier transport according to claim 6, characterized in that, In step S4, after cooling the sample to room temperature, PC is added dropwise. 61 The chlorobenzene solution of BM was spin-coated at a constant speed of 2000 rpm for 40 seconds, and finally the Ag electrode was thermally evaporated to obtain the thin film device.

8. The method for preparing a quasi-two-dimensional perovskite thin film that effectively improves carrier transport according to claim 1, characterized in that, In step S4, PC 61 The mass concentration of BM's chlorobenzene solution is 18~22 mg / mL.

9. The method for preparing a quasi-two-dimensional perovskite thin film with effective improved carrier transport according to claim 8, characterized in that, In step S4, PC 61 The mass concentration of BM's chlorobenzene solution is 20 mg / mL.

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