Interface modification method of all-inorganic perovskite film and film
By using 3-bromo-N-methylbenzylamine as an interface modifier on the surface of CsPbI2Br perovskite films, the charge trap and environmental sensitivity problems in CsPbI2Br perovskite solar cells were solved, the crystallinity and stability of the films were improved, and the optoelectronic and device performances were enhanced.
Patent Information
- Application Number
- CN202211167331.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-23
- Publication Date
- 2025-09-12
- Estimated Expiration
- 2042-09-23
AI Technical Summary
The uncoordinated Pb2+ and Cs+ in CsPbI2Br perovskite solar cells act as charge traps, leading to the accumulation of photogenerated carriers and inducing non-radiative recombination, which affects the device performance. At the same time, the perovskite solar cells are sensitive to the environment and are prone to phase transition, resulting in a decrease in photoelectric performance.
3-Bromo-N-methylbenzylamine was used as an interface modifier to form hydrogen bonds with I- and Br- through the NH functional group, and to coordinate with uncoordinated Pb2+ and Cs+, thereby enhancing the dipole property, preventing the intrusion of water molecules, and improving the crystallinity and stability of the CsPbI2Br perovskite film.
It reduces the defect state density of CsPbI2Br perovskite films, promotes hole transport, improves optical properties and air stability, delays film degradation, and enhances the photoelectric conversion efficiency and thermal stability of the device.
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Figure CN115697000B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of solar cell modification, and in particular relates to an interface modification method of an all-inorganic perovskite thin film and the thin film. Background Art
[0002] With the development of social economy, environmental pollution and energy shortage are becoming increasingly serious. The use of clean and renewable solar energy is one of the effective ways to solve this problem. The development of photoelectric conversion devices is an important link. The development of silicon solar cells is subject to certain restrictions due to their high energy consumption and complex process. Perovskite solar cells are one of the most promising photovoltaic power generation technologies. Lead halide perovskite materials have excellent photoelectrochemical and electrical properties, such as high light absorption coefficient, low exciton binding energy, long charge carrier diffusion length, high defect tolerance, etc. Although the efficiency of solar cells has increased rapidly, its stability problem cannot be ignored. For organic-inorganic hybrid perovskite solar cells, methylamine ions (MA + ), formamidinium ion (FA + ) can improve its resistance to moisture, but the volatility and poor thermal stability of organic cations are not conducive to its commercialization. The CsPbI3 material in inorganic perovskite solar cells has a narrow band gap (1.73eV), which is suitable for use as the light absorption layer of perovskite solar cells. However, the optically active α phase (black phase) easily transforms into the optically inactive δ phase (yellow phase) at room temperature; at the same time, although CsPbBr3 has good humidity stability, its wide band gap (2.3eV) seriously affects its absorption of visible light. Mixed halide perovskites represented by CsPbI2Br have a suitable band gap (1.92eV). - Partial replacement of Br - It can well balance light absorption and humidity stability, and has great potential for application in perovskite solar cells. In recent years, CsPbI2Br perovskite solar cells have developed rapidly, but CsPbI2Br all-inorganic perovskite solar cells still have a series of problems: ① Uncoordinated Pb in CsPbI2Br perovskite solar cells 2+ and Cs + It will become a charge trap, capturing photogenerated carriers, causing charge accumulation at the interface, triggering severe non-radiative recombination, resulting in severe energy loss and affecting device performance. ②CsPbI2Br perovskite solar cells are highly sensitive to the environment, especially in environments with high humidity, and are prone to phase transition and loss of optical activity, thus affecting the photoelectric performance of the device.
[0003] The interface modifier used in the present invention contains an NH functional group, the H in which can react with I - and Br -The reaction occurs through hydrogen bonding, and the nitrogen in the NH functional group can react with the uncoordinated Pb 2+ and Cs + The interface modifier 3-bromo-N-methylbenzylamine in the present invention contains a bromine group, which helps to form a dipole interlayer to regulate the band structure, thereby promoting the transmission and collection of holes. In addition, the bromine group and the benzene ring structure have a certain hydrophobicity, which can block the intrusion of water molecules and delay the degradation of the CsPbI2Br perovskite film, thereby improving the air stability of the CsPbI2Br perovskite film to a certain extent. Summary of the Invention
[0004] The present invention aims to provide an interface modification method and film for an all-inorganic perovskite film. Using 3-bromo-N-methylbenzylamine as a modifier, the interface of the all-inorganic perovskite film is modified through a specific method, thereby improving the quality and stability of the CsPbI2Br all-inorganic perovskite film. The core of the method is an interface modification process for a planar-structured CsPbI2Br all-inorganic perovskite film. This small-molecule interface-modified all-inorganic perovskite film can be applied to perovskite solar cells.
[0005] The technical solution of the present invention is:
[0006] A method for modifying the interface of an all-inorganic perovskite film is to spin-coat an interface modifier, 3-bromo-N-methylbenzylamine, on the surface of the CsPbI2Br all-inorganic perovskite film. The preparation method includes the following steps:
[0007] (1) Preparation of transparent conductive substrate / SnO2 / SnCl2 / CsPbI2Br film.
[0008] (2) Weighing an interface modifier and dissolving it in isopropanol, stirring until completely dissolved, to obtain an interface modifier / isopropanol solution, spin-coating the interface modifier / isopropanol solution on the transparent conductive substrate / SnO2 / SnCl2 / CsPbI2Br film prepared in step (1), and annealing at a constant temperature for a certain period of time to obtain a transparent conductive substrate / SnO2 / SnCl2 / CsPbI2Br / interface modifier film.
[0009] Furthermore, in step (2), the mass concentration of the interface modifier / isopropanol solution does not exceed 5 mg / mL, the stirring temperature is 15-40° C., and the stirring time is 50-150 min.
[0010] Furthermore, the spin coating volume of the interface modifier / isopropanol solution in step (2) is 100-150 μL, the spin coating speed is 2000-5000 rpm, and the spin coating time is 10s-60s.
[0011] Furthermore, the constant temperature annealing temperature in step (2) is 50-150° C., and the annealing time is 1-5 minutes.
[0012] Taking FTO as an example (but not limited to FTO), the preparation method of the present invention includes the following steps:
[0013] (1) Preparation of FTO / SnO2 / SnCl2 / CsPbI2Br thin film.
[0014] (2) Dissolve an appropriate amount of 3-bromo-N-methylbenzylamine in a certain volume of isopropanol and stir with a magnetic stirrer at 15-40°C until completely dissolved to obtain a 3-bromo-N-methylbenzylamine / isopropanol solution with a concentration of 0-5 mg / mL. Spin-coat 100-150 μL of the 3-bromo-N-methylbenzylamine / isopropanol solution onto the FTO / SnO2 / SnCl2 / CsPbI2Br film prepared in step (1) at a spin-coating speed of 2000-5000 rpm for 10-60 seconds. Subsequently, anneal the film on a constant temperature heating platform at 50-150°C for 1-5 minutes to obtain a FTO / SnO2 / SnCl2 / CsPbI2Br / 3-bromo-N-methylbenzylamine film.
[0015] In the above step (2), the 3-bromo-N-methylbenzylamine has a purity of 97% (chromatographically pure GC).
[0016] The specifications of the above-mentioned FTO conductive glass are 20mm*25mm, the square resistance is 14Ω, and the transmittance is ≥90%.
[0017] The present invention uses 3-bromo-N-methylbenzylamine as an interface modifier to be spin-coated on the surface of the CsPbI2Br all-inorganic perovskite film. NH functional groups are introduced on the surface of the CsPbI2Br film to form a hydrogen bond with I - and Br - reaction, and the N in the NH functional group can react with the uncoordinated Pb 2+ and Cs +The bromine groups in the 3-bromo-N-methylbenzylamine modifier enhance dipole activity, promoting charge extraction. The hydrophobic bromine groups and benzene rings help inhibit perovskite film degradation caused by water infiltration. Research results show that the surface modification of CsPbI2Br all-inorganic perovskite films using 3-bromo-N-methylbenzylamine improves the quality, phase stability, and optical properties of the CsPbI2Br all-inorganic perovskite films. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 Field emission scanning electron microscopy images of unmodified CsPbI2Br film (a) and 3-bromo-N-methylbenzylamine modified CsPbI2Br perovskite film (b).
[0019] Figure 2 X-ray diffraction patterns of unmodified CsPbI2Br thin film and 3-bromo-N-methylbenzylamine modified CsPbI2Br thin film.
[0020] Figure 3 UV-visible absorption spectra of unmodified CsPbI2Br thin film and 3-bromo-N-methylbenzylamine modified CsPbI2Br thin film.
[0021] Figure 4 Fluorescence spectra of unmodified CsPbI2Br thin film and 3-bromo-N-methylbenzylamine modified CsPbI2Br thin film.
[0022] Figure 5 Optical stability diagrams of unmodified CsPbI2Br film (a) and 3-bromo-N-methylbenzylamine modified CsPbI2Br film (b) stored in air for 0 to 30 min, respectively.
[0023] Figure 6 These are the stability photos of unmodified CsPbI2Br film and 3-bromo-N-methylbenzylamine modified CsPbI2Br film stored in air for 0 to 30 minutes. DETAILED DESCRIPTION
[0024] The present invention will be described in detail below with reference to specific embodiments.
[0025] Example 1
[0026] (1) Preparation of FTO / SnO2 / SnCl2 / CsPbI2Br thin film. The preparation method can be as follows:
[0027] 1) The FTO conductive glass was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water, respectively, dried in a vacuum drying oven, and then treated in an ultraviolet ozone cleaning machine for 30 minutes; a SnO2 hydrocolloid dispersion, deionized water, and isopropyl alcohol were mixed, stirred evenly, and filtered through a polytetrafluoroethylene filter to obtain a SnO2 precursor solution, which was spin-coated onto the FTO conductive glass that had been treated with ultraviolet ozone. The spin coating was repeated several times, and then annealed to obtain a SnO2 thin film based on the FTO conductive glass, which was recorded as an FTO / SnO2 thin film;
[0028] 2) dissolving SnCl2 in anhydrous ethanol to obtain a SnCl2 solution, spin-coating the SnCl2 solution on the FTO / SnO2 film, and annealing to obtain a FTO / SnO2 / SnCl2 film; the surface passivation of the SnO2 electron transport layer by SnCl2 not only effectively reduces the recombination of the CsPbI2Br perovskite and SnO2 interface, but also accelerates the extraction of electrons from the perovskite film, which can significantly improve the efficiency, open circuit voltage and thermal stability of the device; the annealing can be preferably performed by first annealing at 80-120°C for 5-25 minutes and then continuing annealing at a higher temperature (150-200°C) for 50-100 minutes, which is more conducive to obtaining a film with high crystalline quality;
[0029] 3) Weighing CsI, PbI2, and PbBr2, dissolving them in dimethyl sulfoxide (DMSO), heating and stirring at a constant temperature until completely dissolved, then filtering the solution through a polytetrafluoroethylene filter to obtain a CsPbI2Br precursor solution; treating the FTO / SnO2 / SnCl2 film prepared in step 2) in a UV-ozone cleaning chamber for at least 30 minutes, spin-coating the CsPbI2Br precursor solution onto the UV-ozone-treated FTO / SnO2 / SnCl2 film, and annealing the film after spin-coating to obtain a FTO / SnO2 / SnCl2 / CsPbI2Br film; the annealing is preferably a gradient annealing, first annealing at a lower temperature of 30-80°C for 1-5 minutes, then annealing at a higher temperature of 120-180°C for 5-10 minutes. The gradient annealing can improve the quality of the perovskite film, increase the film coverage, crystallinity, grain size, and distribution uniformity, and reduce defect density.
[0030] (2) Dissolve an appropriate amount of 3-bromo-N-methylbenzylamine in a certain volume of isopropanol and stir magnetically at 25°C for 30 minutes until completely dissolved. Prepare a 3-bromo-N-methylbenzylamine / isopropanol solution with a mass concentration of 4 mg / mL. Take 140 μL of the 3-bromo-N-methylbenzylamine / isopropanol solution and spin-coat it on the FTO / SnO2 / SnCl2 / CsPbI2Br film at a spin-coating speed of 2500 rpm for 35 seconds. Then anneal the film at 100°C on a constant temperature heating table for 3 minutes to obtain the FTO / SnO2 / SnCl2 / CsPbI2Br / 3-bromo-N-methylbenzylamine film.
[0031] The present invention will be described in detail below with reference to the accompanying drawings:
[0032] Attachment Figure 1 (a) and attached Figure 1 (b) Field emission scanning electron micrographs of an unmodified CsPbI2Br film and a CsPbI2Br film modified with 3-bromo-N-methylbenzylamine. The results show that the unmodified CsPbI2Br film has poor crystallinity, small grain size, numerous grain boundary defects, and uneven grain size distribution. After modification with 3-bromo-N-methylbenzylamine, the grain size of the CsPbI2Br film is significantly larger, grain boundary defects are reduced, the grain size distribution is more uniform, and the crystallinity is increased, significantly improving the quality of the CsPbI2Br film.
[0033] Attachment Figure 2 The X-ray diffraction patterns of unmodified CsPbI2Br film and 3-bromo-N-methylbenzylamine modified CsPbI2Br film are shown in Figure 2. Figure 2 It can be seen that in the XRD pattern of unmodified CsPbI2Br, the diffraction peak intensity corresponding to the optical phase α phase is low, indicating that the unmodified CsPbI2Br film has poor crystallinity. In the XRD pattern of CsPbI2Br modified with 3-bromo-N-methylbenzylamine, the diffraction peak intensity corresponding to the α phase is significantly increased compared to that of unmodified CsPbI2Br, indicating that the crystallization properties of CsPbI2Br are significantly improved after 3-bromo-N-methylbenzylamine modification, and the room temperature stability of the black phase is improved.
[0034] Attachment Figure 3 The UV-visible absorption spectra of unmodified CsPbI2Br thin films and CsPbI2Br thin films modified with 3-bromo-N-methylbenzylamine are shown. The results show that after modification with 3-bromo-N-methylbenzylamine, the absorbance of the CsPbI2Br thin film significantly increases in the wavelength range of 500nm-900nm, and the absorption edge red-shifts from 655.12nm to 656.37nm, indicating that the light absorption properties of the CsPbI2Br thin film are improved after modification with 3-bromo-N-methylbenzylamine.
[0035] Attachment Figure 4 The fluorescence spectra of unmodified CsPbI2Br film and 3-bromo-N-methylbenzylamine modified CsPbI2Br film are shown in Figure 2. Figure 4 It can be seen that after modification with 3-bromo-N-methylbenzylamine, the PL intensity of the CsPbI2Br film is significantly enhanced, indicating that 3-bromo-N-methylbenzylamine passivates the surface defects of the CsPbI2Br film, inhibits non-radiative recombination, and improves the quality of the CsPbI2Br film.
[0036] Attachment Figure 5 The optical stability diagrams of unmodified CsPbI2Br film and 3-bromo-N-methylbenzylamine modified CsPbI2Br film stored in air for 0 to 30 minutes (RH ~ 50%). Figure 5 It can be seen that after the unmodified CsPbI2Br film was placed in the environment for 20 minutes, its absorbance in the 500-900nm range decreased sharply, and then it was almost completely decomposed. However, after the CsPbI2Br film modified with 3-bromo-N-methylbenzylamine was placed in the environment for 20 minutes, its absorbance in the 500-900nm range decreased more slowly, but the absorption edge still corresponded to the characteristic absorption edge of CsPbI2Br, indicating that it was not completely decomposed. Only after 30 minutes did obvious degradation appear. This result shows that 3-bromo-N-methylbenzylamine modification can inhibit the infiltration of water, inhibit the degradation process of CsPbI2Br film under environmental conditions to a certain extent, and improve its optical stability.
[0037] Attachment Figure 6 The following are photos of the stability of unmodified CsPbI2Br film and 3-bromo-N-methylbenzylamine modified CsPbI2Br film stored in air for 0 to 30 minutes (RH ~ 50%). Figure 6 It can be seen that the color of the unmodified CsPbI2Br film photo became significantly lighter after 10 minutes, indicating that the unmodified perovskite film showed more severe degradation. However, after the CsPbI2Br film modified with 3-bromo-N-methylbenzylamine was placed in the environment for 10 minutes, the color of the photo became slightly lighter, indicating that the degradation of the CsPbI2Br film was not obvious. In the following 20 minutes, the color of the unmodified CsPbI2Br film photo became lighter than that of the film modified with 3-bromo-N-methylbenzylamine, indicating that the unmodified CsPbI2Br film was more severely degraded. The results show that the interface modification of 3-bromo-N-methylbenzylamine can delay the degradation process of the perovskite film and improve the environmental stability of the CsPbI2Br film.
Claims
1. A method for interface modification of an all-inorganic perovskite film, characterized in that A small molecule interface modifier is spin-coated on the surface of the CsPbI2Br all-inorganic perovskite film, wherein the interface modifier is 3-bromo-N-methylbenzylamine.
2. The interface modification method of the all-inorganic perovskite thin film according to claim 1, characterized in that: The following steps are involved: (1) Preparation of transparent conductive substrate / SnO2 / SnCl2 / CsPbI2Br film; (2) Weighing an interface modifier and dissolving it in isopropanol, stirring until completely dissolved, to obtain an interface modifier / isopropanol solution, spin-coating the interface modifier / isopropanol solution on the transparent conductive substrate / SnO2 / SnCl2 / CsPbI2Br film prepared in step (1), and annealing at a constant temperature for a certain period of time to obtain a transparent conductive substrate / SnO2 / SnCl2 / CsPbI2Br / interface modifier film.
3. The method for interface modification of an all-inorganic perovskite thin film according to claim 2, wherein: The mass concentration of the interface modifier / isopropanol solution in step (2) does not exceed 5 mg / mL, the stirring temperature is 15-40° C., and the stirring time is 50-150 min.
4. The method for interface modification of an all-inorganic perovskite thin film according to claim 2, wherein: The spin coating speed of the interface modifier / isopropanol solution in step (2) is 2000-5000 rpm, and the spin coating time is 10s-60s.
5. The method for interface modification of an all-inorganic perovskite thin film according to claim 2, wherein: The constant temperature annealing temperature in step (2) is 50-150° C., and the annealing time is 1-5 minutes.
6. An all-inorganic perovskite film, characterized in that The method is prepared by the method according to any one of claims 1 to 5.