Method for modifying the buried interface of a perovskite solar cell

Abstract

The application discloses a method for modifying a buried bottom interface of a perovskite solar cell, and specifically comprises the following steps: 1) dissolving potassium stannate powder in deionized water to prepare an aqueous solution with a concentration of 1-5 mg / mL, and filtering; 2) coating the aqueous solution on a tin dioxide film by using a spin coating method; and 3) performing annealing treatment on the tin dioxide film coated with potassium stannate to form a potassium stannate interface modification layer. Compared with the prior art, the method has the advantages that PS is used as a SnO2 / perovskite interface modification layer, stannate ions can passivate oxygen vacancies on the surface of SnO2, reduce surface defects of SnO2, balance energy levels between SnO2 and perovskite, and inhibit accumulation and recombination of electrons between interfaces. + Promote better perovskite crystallization, reduce grain boundary defects; fill A-site cation vacancies, enhance the stability of the perovskite crystal structure, form a more stable crystal phase, improve the quality of the perovskite film, and further improve the device performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic technology, in particular to a method for modifying the buried interface of a perovskite solar cell (PSCs), aiming to optimize the device structure and improve the photoelectric conversion performance by introducing potassium stannate (PS) as an interface modification layer. BACKGROUND

[0002] Photovoltaic technology, as a clean and renewable energy source, plays a crucial role in addressing climate change and achieving sustainable development. Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted significant attention due to their unique optoelectronic properties, low-cost fabrication process, and excellent defect tolerance, making them an important development direction after the third generation of photovoltaic technology. In recent years, the certified energy conversion efficiency of PSCs has broken through 26.7%, comparable to commercial monocrystalline silicon cells, showing a broad application prospect. However, there is still a certain gap between this efficiency value and the theoretical Shockley-Queisser limit (30.5%) of single-junction PSCs. Optimizing device structure and improving functional layer performance are key to further efficiency improvement. In PSCs devices, tin dioxide (SnO2) is commonly used as an electron transport layer (ETL) material, which has higher electron mobility and better energy level matching than titanium dioxide (TiO2) and zinc oxide (ZnO), facilitating interface charge transport and improving device efficiency. However, the oxygen vacancy defects on the surface of SnO2 can capture photo-generated charge carriers, inducing non-radiative energy loss at the SnO2 / perovskite interface, thereby reducing the photoelectric conversion performance of the cell. Therefore, how to effectively alleviate the negative impact of SnO2 defects on device performance is a key issue that needs to be addressed.

[0003] To this end, researchers have proposed various SnO2 interface passivation strategies, including the introduction of alkali metal cations or functional anions, etc. For example, Gao (GAO D, YANG L, MA X, et al. Passivating Interface with Multifunctional Ionic Liquid Containing Simultaneously Fluorinated Anion and Cation Yielding Stable Perovskite Solar Cells over 23% Efficiency [J]. Journal of Energy Chemistry, 2022, 69: 659-666.) et al. introduced 4-fluoro-phenyl ammonium tetrafluoroborate (FBABF4) at the SnO2 and perovskite interface, utilizing the BF4 -The way of forming coordination bonds with the SnO2 surface inhibits oxygen vacancy defects and promotes charge transport; Zhu (ZHU S, WU J, SUN W, et al. Interlayer Modification Using Phenylethylamine Tetrafluoroborate for Highly Effective Perovskite Solar Cells [J]. ACS Applied Energy Materials, 2022, 5(1): 658-666.) et al. introduced a molecular modification layer of phenylethylamine tetrafluoroborate (PEABF4) at the ETL / perovskite interface, which promotes electron extraction and passivates interface defects, and inhibits carrier non-radiative recombination. In addition, structural defects present at the bottom of the perovskite layer are also potential non-radiative recombination centers, especially in thin films prepared by the two-step method. For this reason, researchers have developed a buried interface engineering strategy to regulate the energy level alignment and defect distribution between the transport layer and the active layer by embedding an interfacial modification layer, achieving comprehensive optimization of charge transport and device performance. For example, Wu (WU S, ZHANG J, LI Z, et al., Modulation of Defects and Interfaces Through Alkylammonium Interlayer for Efficient Inverted Perovskite Solar Cells. Joule, 2022, 4, 1248-1262.) et al. used a large alkylammonium interlayer (LAI) to reduce the energy loss between the transport layer and the perovskite, not only inhibiting interface non-radiative recombination, but also improving charge selectivity and extraction efficiency, allowing the device PCE to break through 22%. Xu (XU H, MIAO Y, WEI N, et al., CsI Enhanced Buried Interface for Efficient and Uv-robust Perovskite Solar Cells. Advanced Energy Materials, 2021, 12, 2103151.) et al. used CsI-SnO2 composite material as ETL to promote perovskite film growth and effectively passivate interface defects. Cs + The gradient distribution of Cs optimizes the band alignment, significantly improving the efficiency of FAPbI3-based PSCs to 23.3%.

[0004] Given the significant effect of buried interface engineering on improving device performance, it is crucial to find a modification molecule that can eliminate both oxygen vacancies on the SnO2 surface and defects at the bottom of the perovskite film. SUMMARY

[0005] In view of the problem that the bottom surface defects of the perovskite thin film and the surface oxygen defects of the electron transport layer SnO2 reduce the performance of the PSCs, the application provides a method for modifying a buried bottom interface of a perovskite solar cell, which introduces potassium stannate (PS) as a SnO2 / perovskite interface modification layer into a PSC device structure, passivates the surface oxygen defects of SnO2 and the bottom defects of the perovskite thin film, and further improves the performance of the PSCs.

[0006] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0007] The method for modifying a buried bottom interface of a perovskite solar cell specifically comprises the following steps:

[0008] 1) Preparation of a solution: potassium stannate powder is dissolved in deionized water to prepare an aqueous solution with a concentration of 1-5 mg / mL, and the aqueous solution is filtered;

[0009] 2) Coating: the aqueous solution is coated on a tin dioxide thin film by using a spin coating method;

[0010] 3) Annealing to form an interface modification layer: the tin dioxide thin film coated with the potassium stannate is subjected to annealing treatment to form a potassium stannate interface modification layer.

[0011] The structure of the potassium stannate is as follows:

[0012]

[0013] As a preferred scheme, in the step 1), the potassium stannate powder is added to the deionized water, stirred at room temperature for 0.5 h, and filtered by using a 0.22 μm filter membrane to obtain the aqueous solution.

[0014] As a preferred scheme, in the step 2), the spin coating parameters of the spin coating method are 3500-4500 rpm and 40-60 s.

[0015] As a preferred scheme, in the step 3), the annealing temperature is 100 ℃, and the annealing time is 10 min.

[0016] As a preferred scheme, the method further comprises the steps of preparing a perovskite active layer, a hole transport layer and a metal electrode on the tin dioxide thin film.

[0017] As a preferred scheme, the perovskite active layer is prepared by a two-step method.

[0018] The PS interface modification layer can passivate the oxygen vacancies on the surface of SnO2, reduce the surface defects of SnO2, balance the energy levels between SnO2 and the perovskite, inhibit the accumulation and recombination of electrons between the interfaces, and the potassium ions (K+) can promote the crystallization of the perovskite, reduce the grain boundary defects, fill the A-site cation vacancies, and enhance the stability of the crystal structure of the perovskite.

[0019] The present application has the advantages compared with the prior art that: using PS as the SnO2 / perovskite interface modification layer, stannate ions can passivate the oxygen vacancies on the surface of SnO2, reduce the surface defects of SnO2, and inhibit the accumulation and recombination of electrons between the interfaces by balancing the energy levels between SnO2 and perovskite. + Promote better perovskite crystallization, reduce grain boundary defects; fill A-site cation vacancies, enhance the stability of the perovskite crystal structure, form a more stable crystal phase, improve the quality of the perovskite thin film, and further improve the device performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The conductivity of the SnO2 thin film of the control group and the SnO2-PS thin film of the experimental group of the present application.

[0021] Figure 2 The transmission spectrum of the SnO2 thin film and the SnO2-PS thin film on the ITO substrate of the present application.

[0022] Figure 3 The surface SEM image of the perovskite thin film of the control group and the perovskite thin film modified by PS of the present application. DETAILED DESCRIPTION

[0023] In order to better understand the present application, the content of the present application will be further illustrated below in combination with examples, but the content of the present application is not limited to the following examples only.

[0024] A method for modifying the buried interface of a perovskite solar cell, the specific formula and steps are as follows.

[0025] I. Solution preparation:

[0026] Electron transport layer: dilute the SnO2 colloid solution (12wt%) with deionized water to a ratio of 1:3, stir at room temperature for 30 minutes, and then filter with a syringe and filter membrane to obtain the required SnO2 solution.

[0027] Perovskite thin film: dissolve 599.3mg PbI2 powder in 900μL DMF and 100μL DMSO, stir at 70℃ for 3 hours, and then filter with a syringe and filter membrane to obtain the required PbI2 solution. In addition, dissolve 90mg FAI and 12mg MACl in 1mL isopropanol (IPA), stir at room temperature for 30 minutes. Then filter with a syringe and filter membrane to obtain the required organic salt solution.

[0028] Hole transport layer: 520 mg Li-TFSI in 1 ml acetonitrile was taken first, then 72.3 mg Spiro-OMeTAD was weighed, 17.5 μL Li-TFSI acetonitrile solution and 29 μL 4-tBP were taken together in 1 ml chlorobenzene, and the hole transport layer solution was obtained by filtering through a syringe and filter membrane.

[0029] PS modification layer solution: 0-8 mg PS powder was dissolved in 1 mL of deionized water, and stirred at room temperature for 0.5 hours to completely dissolve.

[0030] II. Device preparation process:

[0031] 1. Cleaning of ITO glass: the ITO glass substrate was wiped with a cleaning agent, and then ultrasonically cleaned in deionized water, acetone and IPA for 30 minutes in turn.

[0032] 2. Preparation of electron transport layer: SnO2 thin film was prepared on the substrate by spin coating process at 3000 rpm for 50 seconds in air environment, and heat treated at 150°C for 25 minutes.

[0033] 3. Preparation of PS buried interface modification layer: PS modification solution (80 μL) was coated on the SnO2 thin film by spin coating process at 4000 rpm for 50 seconds in air environment, and heat treated at 100°C for 10 minutes.

[0034] 4. Preparation of perovskite active layer: PbI2 mixed solution (70 μL, 2000 rpm, 30 s) was first spin-coated in nitrogen environment, heat treated at 70°C for 1 minute and cooled for 10 minutes, then 70 μL of FAI+MACl solution (1800 rpm, 30 s) was spin-coated, and finally heat treated at 150°C for 30 minutes in air environment with humidity of 30%-40%.

[0035] 5. Preparation of hole transport layer: Spiro-OMeTAD solution (50 μL) was coated on the perovskite thin film by spin coating process at 3000 rpm for 30 seconds in nitrogen environment.

[0036] 6. Preparation of gold electrode: 80 nm thick metal electrode was deposited by thermal evaporation process in vacuum environment of 5x10 -4 Pa.

[0037] III. Control device preparation process:

[0038] Step (3) of preparing PS buried interface modification layer was not performed, and the remaining steps were consistent with the device preparation process.

[0039] IV. Performance test:

[0040] 1. SnO2 film conductivity test:

[0041] To evaluate the effect of PS modification on the conductivity of SnO2 film, ITO / SnO2 / Au and ITO / SnO2 / PS / Au diode structures were used, and the conductivity of the film was calculated by measuring the current-voltage curve in the voltage range of -1 to 1 V. The conductivity can be obtained by the following formula:

[0042]

[0043] Where σ represents the conductivity, I is the current density, L is the thickness of the SnO2 film, V is the voltage in the device, and S is the cross-sectional area of the device.

[0044] As shown in Figure 1 , the conductivities of the control group SnO2 film and the experimental group SnO2-PS film were calculated to be 2.30 x 10-3 and 3.23 x 10-3 S cm-1, respectively. The enhancement of conductivity is mainly due to the interaction between stannate ions and SnO2, which reduces the oxygen vacancies, thereby improving the charge transport efficiency and enhancing the device performance.

[0045] 2. SnO2 film light transmittance test:

[0046] To prove that the introduction of PS modification layer will not hinder the absorption of perovskite film in the visible light region, the light transmittance of the control group SnO2 film and the experimental group SnO2-PS film was compared, and the results are shown in Figure 2 . The introduction of PS modification layer significantly improves the visible light transmittance, ensuring the excellent utilization rate of the device in the visible light band.

[0047] 3. Time-resolved photoluminescence (TRPL) test of perovskite film:

[0048] The performance of perovskite film under different interface layer conditions was compared, i.e. ITO / SnO2 / PVSK substrate and ITO / SnO2-PS / PVSK substrate. The results show that the fluorescence lifetime of the perovskite film modified by PS is shortened from 224.3 nanoseconds to 139.1 nanoseconds (see Table 1). The introduction of PS interface layer effectively suppresses non-radiative recombination and improves the extraction efficiency of carriers at the electron transport layer interface.

[0049] Table 1. TRPL lifetime parameters of ITO / SnO2 / PVSK substrate and ITO / SnO2-PS / PVSK substrate

[0050] Films [A1 (%)] [tau1 (ns)] [A2(%)] [tau]2 (ns) av (ns)]]> ​ ITO / SnO2 / PVSK 0.36 55.5 0.63 245.1 224.3 ITO / SnO2-PS / PVSK 0.70 47.2 0.42 179.4 139.1

[0051] 4. Scanning electron microscopy characterization of perovskite film:

[0052] The surface morphology of the perovskite film was observed by scanning electron microscopy (SEM). Figure 3 The results showed that all the perovskite films could completely cover the substrate. In contrast, the grain size of the perovskite film modified by PS was larger, mainly due to the interaction between potassium ions and perovskite promoting the formation of high crystallinity films. High crystallinity and fewer grain boundaries are conducive to the migration and extraction of carriers, thereby improving the device performance.

[0053] 5. Photovoltaic performance test of perovskite device:

[0054] The unmodified and PS-modified devices were compared and tested using a solar simulator, and the results showed that the PS modification at an optimal concentration of 5 mg / mL could significantly improve the photovoltaic performance of the device, increasing the energy conversion efficiency from 21.32% to 24.58% (see the table below).

[0055]

Device photovoltaic performance test result list

[0056] PS (mg / mL) V oc (V) J sc (mA cm -2 )]]> FF (%) PCE (%) 0 1.13 24.55 76.85 21.32 0.5 1.135 24.68 77.67 21.75 1 1.145 24.96 78.79 22.51 2 1.144 25.10 78.88 22.65 3 1.152 25.23 79.25 23.03 4 1.169 25.36 80.05 23.73 5 1.179 25.67 81.2 24.58 6 1.171 25.54 80.79 24.17

[0057] Experimental results:

[0058] As can be seen from the above test results, by introducing the PS bifunctional modifier, the present application passivates the defect states at the interface between SnO2 and perovskite, effectively suppresses the interface recombination, and promotes the charge transport, thereby significantly improving the performance of PSCs.

[0059] The unique molecular structure and component characteristics of PS enable it to have multiple synergistic functions: the stannate ion not only passivates the oxygen vacancies on the surface of SnO2, but also adjusts the energy level matching between SnO2 and perovskite, optimizing the energy band arrangement of the device. By passivating oxygen defects and improving the energy level, the introduction of PS can also promote the crystallinity of the SnO2 film and improve the charge mobility inside and outside the SnO2 layer. At the same time, K + can effectively promote the crystallization process of the perovskite layer, reduce the grain boundary defects, fill the A-site ion vacancies, and enhance the stability of the perovskite crystal structure. Through the synergistic effect of PS, it is expected to achieve the synchronous optimization of the components at the two interfaces of SnO2 and perovskite, and comprehensively improve the photoelectric performance of PSCs.

[0060] The above describes the present application and its embodiments, which are not limiting, and the embodiments shown in the drawings are only one of the embodiments of the present application, and the actual structure is not limited thereto. In summary, if a person of ordinary skill in the art is inspired thereby, without departing from the spirit of the present application, without creating a similar structure and embodiment of the technical solution, all of which should belong to the protection scope of the present application.

Claims

1. A method for modifying the buried interface of a perovskite solar cell, characterized in that, Specifically, the following steps are included: 1) Solution preparation: Dissolve potassium stannate powder in deionized water to prepare an aqueous solution with a concentration of 1-5 mg / mL, and then filter. 2) Coating: The aqueous solution is coated onto a tin dioxide film using a spin coating method; 3) Annealing to form an interface modification layer: The tin dioxide film coated with potassium stannate is annealed to form a potassium stannate interface modification layer.

2. The method for modifying the buried interface of a perovskite solar cell according to claim 1, characterized in that: The structural formula of the potassium stannate is: 。 3. The method for modifying the buried interface of a perovskite solar cell according to claim 1, characterized in that: In step 1), potassium stannate powder is added to deionized water, stirred at room temperature for 0.5 h, and filtered through a 0.22 μm filter membrane to obtain an aqueous solution.

4. The method for modifying the buried interface of a perovskite solar cell according to claim 1, characterized in that: In step 2), the spin coating parameters are 3500~4500 rpm and 40~60s.

5. The method for modifying the buried interface of a perovskite solar cell according to claim 1, characterized in that: In step 3), the annealing temperature is 100°C and the time is 10 minutes.

6. The method for modifying the buried interface of a perovskite solar cell according to claim 1, characterized in that: It also includes the steps of preparing a perovskite active layer, a hole transport layer, and a metal electrode on a tin dioxide thin film.

7. The method for modifying the buried interface of a perovskite solar cell according to claim 6, characterized in that: The perovskite active layer was prepared by a two-step method.

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