Perovskite solar cell and preparation method thereof

Abstract

The application provides a perovskite solar cell and a preparation method thereof, and the perovskite solar cell comprises, from bottom to top, an ITO substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode; the perovskite light-absorbing layer is modified by using a thermally activated delayed fluorescence polymer material to form an interface modification layer; the interface modification layer is located between the perovskite light-absorbing layer and the hole transport layer, the perovskite light-absorbing layer is a formamidinium lead triiodide system perovskite, and the wavelength of the thermally activated delayed fluorescence polymer material is 550-700 nm. The TADF polymer material is modified on the surface of the FAPbI3 system perovskite, the residual tensile stress of the FAPbI3 system perovskite in the heat treatment process is compensated, the photoactive alpha phase is stabilized, the reutilization of photo-generated excitons in the QW is realized through the energy transfer process, the radiative recombination loss is inhibited, and the efficiency of the perovskite solar cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of perovskite solar cells, in particular to a perovskite solar cell and a preparation method thereof. BACKGROUND

[0002] Due to the rapid consumption of fossil fuels and the rapid growth of the world population, there is an increasing demand for carbon-free and cost-effective materials to produce sustainable energy, and humans urgently need to develop renewable and clean energy technologies. The sunlight on the earth is very abundant, which can provide inexhaustible clean solar energy, and solar cells can directly convert absorbed sunlight into electrical energy, which is the most promising photovoltaic device to solve the serious environmental and energy problems caused by the use of fossil fuels. In the past decade, the photoelectric conversion efficiency (PCE) of perovskite solar cells (PSC) has increased from the initial 3.8% to 25.7%, which is higher than that of commercial thin-film solar cells and polycrystalline silicon solar cells. Among the perovskite systems reported so far, the formamidinium lead iodide (FAPbI3) system stands out due to its stronger thermal stability and narrow band gap (4.43-4.48 eV) close to the Shockley-Queisser theoretical limit than the MA-containing perovskite system. In addition, the Goldschmidt tolerance factor of FAPbI3 is 0.99, indicating that its perfect cubic crystal structure has negligible distortion. These photoelectric and structural advantages make FAPbI3 the most attractive perovskite system for single-junction PSCs. However, it still faces two major challenges in commercialization and practical application.

[0003] Firstly, FAPbI3 undergoes a spontaneous phase transition from black phase to yellow phase at room temperature, which is due to the ion size mismatch between formamidinium (FA + and [PbI4] 4- octahedra, resulting in tensile stress in the perovskite film to drive phase degradation. In previous attempts, such as smaller ion doping, although α-FAPbI3 has been stabilized at room temperature, the mixed composition of FA / MA, Cs / FA, Cs / FA / MA, Rb / FA / MA, etc. has been reported to have improved phase stability, but it inevitably increases the band gap of the perovskite, which limits the theoretical efficiency of PSCs.

[0004] Secondly, studies have confirmed the existence of twin domains bounded by δ phase in FAPbI3, which can lead to the formation of intrinsic nanostructures and cause quantum confinement effects in the film. To some extent, nanostructures will inherently limit the charge carriers within the photo-generated quantum wells, leading to radiative recombination. This part of energy is usually wasted and cannot be utilized, which can be considered as the main source of photocurrent loss in FAPbI3-based PSCs. At present, such problems have not attracted much attention.

[0005] Therefore, it is crucial to develop a high-efficiency and stable FAPbI3-based PSC while solving the above problems. SUMMARY

[0006] The problem solved by the present application is to provide an interface modification method of a perovskite solar cell capable of inhibiting radiative recombination loss, improving PSC efficiency, and improving the stability of the perovskite solar cell.

[0007] The present application provides a perovskite solar cell, comprising an ITO substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode stacked in order from bottom to top; the perovskite light-absorbing layer is modified by a thermally activated delayed fluorescence polymer material to form an interface modification layer; wherein the interface modification layer is located between the perovskite light-absorbing layer and the hole transport layer, the perovskite light-absorbing layer is a formamidinium lead iodide system perovskite, and the wavelength of the thermally activated delayed fluorescence polymer material is 550-700 nm.

[0008] Preferably, the structure of the thermally activated delayed fluorescence polymer material is as follows:

[0009]

[0010] In the formula, ph is a phenyl group, and n has a value in the range of 3-50.

[0011] Preferably, the ITO substrate comprises an ITO / glass substrate or an ITO / PEN substrate.

[0012] Preferably, the electron transport layer comprises a tin dioxide electron transport layer.

[0013] Preferably, the hole transport layer comprises a 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene hole transport layer.

[0014] Preferably, the metal electrode comprises a gold electrode or a silver electrode.

[0015] Preferably, the ITO substrate is an anode electrode, and the metal electrode is a cathode electrode.

[0016] The present application modifies a thermal activation delayed fluorescence (TADF) polymer material on the surface of a formamidinium lead triiodide (FAPbI3) system perovskite to form an interface modification layer. Since the thermal expansion coefficient of the TADF polymer material is greater than that of FAPbI3, the residual tensile stress of the FAPbI3 system perovskite during heat treatment can be compensated, and the photoactive alpha phase is stabilized. The wavelength of the TADF polymer material is 550-700 nm, and the photoluminescence (PL) spectrum has a large overlapping part with the absorption spectrum of the band gap quantum well (QW) in the FAPbI3 system perovskite, which meets the standard of Förster energy transfer from the polymer to the QW in FAPbI3, stimulates the Dexter energy transfer in the FAPbI3 system perovskite, and realizes the reutilization of the photo-generated excitons in the QW through the above energy transfer process, thereby inhibiting the radiative recombination loss and improving the efficiency of the perovskite solar cell.

[0017] In another aspect, the present application provides a preparation method of a perovskite solar cell, for preparing the perovskite solar cell as described above, comprising the following steps:

[0018] Step S1, spin coating an electron transport layer solution on the surface of an ITO substrate, and then performing heat treatment to obtain an electron transport layer;

[0019] Step S2, dissolving formamidinium lead triiodide in a first solvent to prepare a perovskite precursor solution, spin coating the perovskite precursor solution on the surface of the electron transport layer in a nitrogen glove box, and then performing annealing treatment to obtain a perovskite light-absorbing layer;

[0020] Step S3, dissolving a thermal activation delayed fluorescence polymer material in a second solvent to prepare a thermal activation delayed fluorescence polymer material solution, spin coating the thermal activation delayed fluorescence polymer material solution on the surface of the perovskite light-absorbing layer, and performing annealing treatment to obtain an interface modification layer;

[0021] Step S4, spin coating a hole transport layer solution on the surface of the interface modification layer to obtain a hole transport layer;

[0022] Step S5, preparing a metal electrode on the surface of the hole transport layer by a vacuum thermal evaporation method, and then placing it in a drying oven for oxidation to obtain a perovskite solar cell.

[0023] Preferably, in the step S2, N,N-dimethylformamide and dimethyl sulfoxide are prepared into the first solvent in a proportion of 4:1 by volume ratio, the formamidinium lead iodide is dissolved in the first solvent to prepare the perovskite precursor solution, the concentration of the formamidinium lead iodide in the perovskite precursor solution is 1.3 mol / L; the perovskite precursor solution is spin-coated at a spin-coating rate of 4000-5000 rpm for 20 s in a nitrogen glove box, 0.2 mL of chlorobenzene anti-solvent is added dropwise at the 12th-15th s, and the perovskite light-absorbing layer is obtained by annealing at 150℃ for 10-30 min.

[0024] Preferably, in the step S3, the hot activated delayed fluorescence polymer material is dissolved in chlorobenzene to prepare a hot activated delayed fluorescence polymer material solution, the concentration of the hot activated delayed fluorescence polymer material in the hot activated delayed fluorescence polymer material solution is 0.01-8 mg / mL, the hot activated delayed fluorescence polymer material solution is spin-coated on the surface of the perovskite light-absorbing layer at a spin-coating rate of 5000-6000 rpm, and the interface modification layer is obtained by annealing at 80-150℃ for 8-15 min.

[0025] The preparation method of the perovskite solar cell provided by the application can release residual stress in the FAPbI3 system perovskite, improve the efficiency of the perovskite solar cell through exciton reutilization, and improve the stability of the perovskite solar cell, and the method is easy to operate, has good repeatability, and is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 FIG. 1 is a structural schematic diagram of a perovskite solar cell in Example 1 of the application;

[0027] Figure 2 FIG. 6 is a comparative analysis diagram of photoluminescence spectra of P1 material and M1 material and FAPbI3 absorption spectrum;

[0028] Figure 3 FIG. 8 is a comparative diagram of J-V curves of perovskite solar cells in Example 1 and Comparative Example 1;

[0029] Figure 4 FIG. 10 is a comparative diagram of water contact angles on perovskite surfaces in Example 1 and Comparative Example 1;

[0030] Figure 5 FIG. 12 is a comparative analysis diagram of depth-resolved grazing incidence X-ray diffraction of perovskite solar cells in Example 1 and Comparative Example 1 at different depths;

[0031] Figure 6 FIG. 14 is a diagram of the change trend of photoelectric conversion efficiency of perovskite solar cells in Example 1 and Comparative Example 1 with time. DETAILED DESCRIPTION

[0032] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below.

[0033] It should be noted that the features in the embodiments of the present application can be combined with each other without conflict. The terms "comprise", "include", "contain", "have" are non-limiting, that is, other steps and other components that do not affect the results can be added. The above terms encompass the terms "consist of" and "consist essentially of". Unless otherwise specified, the materials, devices, reagents are commercially available.

[0034] The embodiment of the present application provides a perovskite solar cell, which comprises an ITO substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode stacked in order from bottom to top; the perovskite light-absorbing layer is modified by using a thermally activated delayed fluorescence polymer material to form an interface modification layer; wherein the interface modification layer is located between the perovskite light-absorbing layer and the hole transport layer, the perovskite light-absorbing layer is a formamidinium lead iodide system perovskite, and the wavelength of the thermally activated delayed fluorescence polymer material is 550-700 nm.

[0035] For the problem of improving the phase stability of FAPbI3, introducing external compressive stress on the FAPbI3 film to compensate for its residual stress is a promising way. Organic polymer materials (thermal expansion coefficient is about 3×10 -4 K -1 ) have a larger thermal expansion coefficient than perovskite (thermal expansion coefficient is 3.3~8.4×10 -5 K -1 ), so that the perovskite film in the perovskite solar cell can be applied with compressive stress by coating organic polymer materials.

[0036] The thermally activated delayed fluorescence (TADF) polymer material is a polymer material, which has a higher thermal expansion coefficient than FAPbI3. Coating it on the surface of the FAPbI3 system perovskite can compensate for its residual stress and stabilize its photoactive alpha phase. In addition, the wavelength of the TADF polymer material is 550-700 nm, and its PL spectrum has more overlap with the absorption spectrum of the band gap QW (700-750 nm) in the FAPbI3 system perovskite, which meets the standard of Förster energy transfer from polymer to QW in FAPbI3, stimulates the Dexter energy transfer in the FAPbI3 system perovskite, from QW to interband transition. Through the above energy transfer process, the reutilization of photoexcitons in QW is realized, thereby inhibiting the radiative recombination loss and improving the efficiency of the perovskite solar cell.

[0037] It should be understood that the wavelength of the TADF polymer material and the absorption spectrum of the band gap QW in the FAPbI3 system perovskite refer to the peak of the PL spectrum or the absorption spectrum, and the PL spectrum or the absorption spectrum extends on both sides of the peak, and there is much overlap in the extended area of the PL spectrum and the absorption spectrum.

[0038] In one preferred embodiment, the structure of the thermally activated delayed fluorescence polymer material is as follows:

[0039]

[0040] In the formula, ph is a phenyl group, and n is in the range of 3-50.

[0041] The compound of the above structure is referred to as P1, and the wavelength of P1 is 550 nm. The PL spectrum of P1 has much overlapping part with the band gap QW in the FAPbI3 system perovskite, and P1 has a high thermal expansion coefficient, which can compensate for the residual stress of the FAPbI3 system perovskite, realize the reutilization of photo-generated excitons in the QW, inhibit the radiative recombination loss, and improve the efficiency of the perovskite solar cell.

[0042] Further, the ITO substrate includes an ITO / glass substrate or an ITO / PEN substrate. When the ITO substrate is an ITO / glass substrate, the perovskite solar cell is a rigid device, and when the ITO substrate is an ITO / PEN substrate, the perovskite solar cell is a flexible device.

[0043] The electron transport layer includes a tin dioxide (SnO2) electron transport layer, and the hole transport layer includes a 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD) hole transport layer. Among them, SnO2 as a new type of electron transport layer material has the advantages of high mobility, anti-reflection and low-temperature preparation, and the use of Spiro-OMeTAD as a hole transport layer can improve the efficiency of the perovskite solar cell and is easy to coat.

[0044] The metal electrode includes a gold electrode or a silver electrode, and the metal electrode serves as an output terminal of the perovskite solar cell. The use of a gold electrode or a silver electrode helps to improve the output efficiency.

[0045] In the above perovskite battery, the ITO substrate is an anode electrode, and the metal electrode is a cathode electrode. That is, the perovskite solar cell provided by the embodiment of the present application is a positive type device.

[0046] Another embodiment of the present application provides a preparation method of a perovskite solar cell, which is used to prepare the perovskite solar cell as described above, and includes the following steps:

[0047] Step S1, spin coating an electron transport layer solution on the surface of an ITO substrate, and then performing heat treatment to obtain an electron transport layer;

[0048] Step S2, dissolving formamidinium lead iodide in a first solvent to prepare a perovskite precursor solution, spin coating the perovskite precursor solution on the surface of the electron transport layer in a nitrogen glove box, and then performing annealing treatment to obtain a perovskite light-absorbing layer;

[0049] Step S3, dissolving a thermally activated delayed fluorescence polymer material in a second solvent to prepare a thermally activated delayed fluorescence polymer material solution, spin coating the thermally activated delayed fluorescence polymer material solution on the surface of the perovskite light-absorbing layer, and performing annealing treatment to obtain an interface modification layer;

[0050] Step S4, spin coating a hole transport layer solution on the surface of the interface modification layer to obtain a hole transport layer;

[0051] Step S5, preparing a metal electrode on the surface of the hole transport layer by a vacuum thermal evaporation method, and then placing it in a drying oven for oxidation to obtain a perovskite solar cell.

[0052] Before step S1, the ITO substrate is cleaned with a cleaning agent, deionized water, acetone and isopropanol in sequence, and dried using a nitrogen gun, and then treated with air plasma for 10 min to fully remove impurities on the ITO substrate and improve the subsequent spin coating effect.

[0053] The thickness of the ITO layer in the ITO substrate is about 100 nm, and the ITO serves as an anode electrode in the perovskite solar cell device.

[0054] In step S1, a 15wt% tin dioxide nanodispersion solution is diluted to a concentration of 10wt% with deionized water, i.e., an electron transport layer solution, which is spin coated on the surface of an ITO substrate in an air atmosphere at a spin coating rate of 5500-6500 rpm for 10-30 s, and then heat treated at 150℃ for 20-40 min.

[0055] Since the electron transport layer solution contains water, high-temperature annealing is required to rapidly evaporate the water and promote crystal crystallization to form a smooth and dense electron transport layer. Therefore, heat treatment is performed at 150℃.

[0056] In step S2, N,N-dimethylformamide and dimethyl sulfoxide are prepared into the first solvent in a proportion of 4:1 by volume, the formamidinium lead iodide is dissolved in the first solvent to prepare the perovskite precursor solution, and the concentration of the formamidinium lead iodide in the perovskite precursor solution is 1.3 mol / L; the perovskite precursor solution is spin-coated at a spin-coating rate of 4000-5000 rpm for 20 s in a nitrogen glove box, 0.2 mL of chlorobenzene anti-solvent is added dropwise at 12-15 s, and annealing is performed at 150℃ for 10-30 min to obtain the perovskite light-absorbing layer. In the nitrogen glove box, O2<0.1 ppm, and H2O<0.1 ppm.

[0057] The phase transition temperature of FAPbI3 is about 150℃, and therefore annealing is performed at 150℃. The dropwise addition time of the anti-solvent can be selected to be between 12-15 s according to the ambient temperature in the glove box.

[0058] In step S3, the hot activated delayed fluorescence polymer material is dissolved in chlorobenzene to prepare a hot activated delayed fluorescence polymer material solution, the concentration of the hot activated delayed fluorescence polymer material in the hot activated delayed fluorescence polymer material solution is 0.01-8 mg / mL, the hot activated delayed fluorescence polymer material solution is spin-coated on the surface of the perovskite light-absorbing layer at a spin-coating rate of 5000-6000 rpm, and annealing is performed at 80-150℃ for 8-15 min to obtain the interface modification layer.

[0059] The interface modification layer is relatively thin, and spin-coating can be performed at a relatively high spin-coating rate. Annealing is performed at 80-150℃ after spin-coating to evaporate the solvent and introduce compressive stress on the surface of the perovskite light-absorbing layer during annealing to release residual tensile stress in the perovskite, thereby improving stability.

[0060] In step S4, the hole transport layer solution is spin-coated on the surface of the interface modification layer at a spin-coating rate of 3500-4000 rpm, and the spin-coating time is 30-50 s, thereby obtaining a smooth and flat hole transport layer.

[0061] The hole transport layer solution is prepared as follows: 72.3 mg of Spiro-OMeTAD is dissolved in 1 ml of chlorobenzene, then 28 µl of 4-TBP, 17 µl of Li-TFSI (520 mg of Li-TFSI is dissolved in 1 ml of acetonitrile), and 8 µl of Co salt (360 mg of FK-209 Co is dissolved in 1 ml of acetonitrile) are added, to obtain a Spiro-OMeTAD solution, which is the hole transport layer solution.

[0062] Since the hole transport layer needs to have a certain thickness, the spin coating rate cannot be too high, and heating is not required, and the spin coating rate is controlled in the range of 35000-4000 rpm, and a hole transport layer meeting the requirements can be obtained.

[0063] In step S5, a metal electrode is prepared on the surface of the hole transport layer by a vacuum thermal evaporation method, and then placed in a drying box for oxidation for 12 hours to obtain a perovskite solar cell. The thickness of the metal electrode is 100 nm.

[0064] The preparation method of the perovskite solar cell provided by the embodiment of the present application can release residual stress in the FAPbI3 system perovskite, improve the efficiency of the perovskite solar cell through exciton recombination, and improve the stability of the perovskite solar cell, and is easy to operate, has good repeatability, and is suitable for large-scale production.

[0065] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods in the following examples without specific conditions are generally according to the conditions recommended by the manufacturer.

[0066] Example 1

[0067] 1.1, the etched ITO / glass substrate is sequentially cleaned with cleaning agent, deionized water, acetone and isopropanol, and dried with nitrogen, and then the ITO / glass substrate is treated with air plasma for 10 min, wherein the thickness of the ITO layer in the ITO / glass substrate is 100 nm;

[0068] 1.2, dilute the tin dioxide nanodispersion solution with a concentration of 15wt% to 10wt% with deionized water to obtain a SnO2 precursor solution, and spin coat the SnO2 precursor solution on the surface of the ITO / glass substrate in an air atmosphere by spin coating at a spin coating rate of 6500 rpm for 10 s, and then heat treat at 150 DEG C for 30 min to obtain a SnO2 electron transport layer;

[0069] 1.3, prepare a mixed solvent by mixing N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1, dissolve FAPbI3 in the mixed solvent to prepare a perovskite precursor solution, and the concentration of FAPbI3 in the perovskite precursor solution is 1.3mol / L; spin coat the perovskite precursor solution at a spin coating rate of 5000 rpm for 20 s in a nitrogen glove box, and add 0.2 mL of chlorobenzene anti-solvent at the 12th second, and anneal at 150 DEG C for 10 min to obtain the perovskite light absorbing layer; wherein O2<0.1 ppm, H2O<0.1 ppm in the nitrogen glove box;

[0070] 1.4. Dissolve P1 in chlorobenzene to prepare a P1 solution with a concentration of mg / mL. Spin-coat the P1 solution onto the surface of the perovskite light-absorbing layer at a spin-coating rate of 5000 rpm. Anneal at 100℃ for 10 min to obtain the interface modification layer. The structural formula of P1 is shown below:

[0071]

[0072] In the formula, ph represents phenyl, and n ranges from 3 to 50;

[0073] 1.5 Dissolve 72.3 mg Spiro-OMeTAD in 1 ml of chlorobenzene, then add 28 µl of 4-TBP, 17 µl of Li-TFSI (520 mg Li-TFSI dissolved in 1 ml of acetonitrile) and 8 µl of Co salt (360 mg FK-209 Co dissolved in 1 ml of acetonitrile) to obtain the Spiro-OMeTAD solution, which is the hole transport layer solution;

[0074] 1.6 The hole transport layer solution was spin-coated onto the surface of the interface modification layer at a spin-coating rate of 4000 rpm for 30 s to obtain a smooth and flat hole transport layer.

[0075] 1.7 A silver electrode with a thickness of 100 nm was prepared on the surface of the hole transport layer by vacuum thermal evaporation, and then placed in a drying oven for drying and oxidation for 12 h to obtain a perovskite solar cell.

[0076] Figure 1 This is a schematic diagram of the perovskite solar cell structure in this embodiment. Figure 1 In this context, Ag represents the silver electrode, Spiro-OMeTAD represents the Spiro-OMeTAD hole transport layer, TADF represents the TADF polymer material interface modification layer, Perovskite represents the FAPbI3 perovskite light-absorbing layer, SnO2 represents the SnO2 electron transport layer, and ITO / Glass represents the ITO / glass substrate.

[0077] Example 2

[0078] 2.1 The etched ITO / PEN substrate was cleaned sequentially with cleaning agent, deionized water, acetone and isopropanol, and dried with nitrogen gas. Then the ITO / PEN substrate was treated with air plasma for 10 min. The thickness of the ITO layer in the ITO / PEN substrate was 100 nm.

[0079] 2.2 Dilute the 15wt% tin dioxide nano-dispersion solution with deionized water to 10wt% to prepare the SnO2 precursor solution. Spin-coat the SnO2 precursor solution onto the surface of the ITO / PEN substrate in air atmosphere at a spin coating rate of 5500 rpm for 30 s. Then heat-treat at 150℃ for 40 min to obtain the SnO2 electron transport layer.

[0080] 2.3. N,N-dimethylformamide and dimethyl sulfoxide were mixed in a volume ratio of 4:1 to prepare a perovskite precursor solution. FAPbI3 was dissolved in the mixed solvent to prepare a perovskite precursor solution with a concentration of 1.3 mol / L. In a nitrogen glove box, the perovskite precursor solution was spin-coated at a speed of 4000 rpm for 20 s, and 0.2 mL of chlorobenzene antisolvent was added dropwise at the 15th s. The solution was then annealed at 150 °C for 30 min to obtain the perovskite light-absorbing layer. The concentrations of O2 and H2O in the nitrogen glove box were <0.1 ppm and <0.1 ppm, respectively.

[0081] 2.4. Dissolve P1 in chlorobenzene to prepare a P1 solution with a concentration of 0.01-8 mg / mL. Spin-coat the P1 solution onto the surface of the perovskite light-absorbing layer at a spin-coating rate of 5000-6000 rpm. Anneal at 80-150℃ for 8-15 min to obtain the interface modification layer. The structural formula of P1 is shown below:

[0082]

[0083] In the formula, ph represents phenyl, and n ranges from 3 to 50;

[0084] 2.5 Dissolve 72.3 mg Spiro-OMeTAD in 1 ml of chlorobenzene, then add 28 µl of 4-TBP, 17 µl of Li-TFSI (520 mg Li-TFSI dissolved in 1 ml of acetonitrile) and 8 µl of Co salt (360 mg FK-209 Co dissolved in 1 ml of acetonitrile) to obtain a Spiro-OMeTAD solution, which is the hole transport layer solution.

[0085] 2.6 The hole transport layer solution was spin-coated onto the surface of the interface modification layer at a spin-coating rate of 3500 rpm for 50 s to obtain a smooth and flat hole transport layer.

[0086] 2.7 A silver electrode with a thickness of 100 nm was prepared on the surface of the hole transport layer by vacuum thermal evaporation, and then placed in a drying oven for drying and oxidation for 12 h to obtain a perovskite solar cell.

[0087] Example 3

[0088] 3.1 The etched ITO / glass substrate was cleaned sequentially with cleaning agent, deionized water, acetone and isopropanol, and dried with nitrogen gas. Then the ITO / glass substrate was treated with air plasma for 10 min. The thickness of the ITO layer in the ITO / glass substrate was 100 nm.

[0089] 3.2 Dilute the 15wt% tin dioxide nano-dispersion solution with deionized water to 10wt% to prepare the SnO2 precursor solution. Spin-coat the SnO2 precursor solution onto the surface of ITO / glass substrate in air atmosphere at a spin coating rate of 6000 rpm for 20 s. Then heat-treat at 150℃ for 20 min to obtain the SnO2 electron transport layer.

[0090] 3.3. N,N-dimethylformamide and dimethyl sulfoxide were mixed in a volume ratio of 4:1 to prepare a perovskite precursor solution. FAPbI3 was dissolved in the mixed solvent to prepare a perovskite precursor solution with a concentration of 1.3 mol / L. In a nitrogen glove box, the perovskite precursor solution was spin-coated at a spin coating rate of 4500 rpm for 20 s, and 0.2 mL of chlorobenzene antisolvent was added dropwise at the 13th s. The solution was then annealed at 150 °C for 20 min to obtain the perovskite light-absorbing layer. The nitrogen glove box contained O2 < 0.1 ppm and H2O < 0.1 ppm.

[0091] 3.4. Dissolve P1 in chlorobenzene to prepare a P1 solution with a concentration of 0.01-8 mg / mL. Spin-coat the P1 solution onto the surface of the perovskite light-absorbing layer at a spin-coating rate of 5000-6000 rpm. Anneal at 150℃ for 8 min to obtain the interface modification layer. The structural formula of P1 is shown below:

[0092]

[0093] In the formula, ph represents phenyl, and n ranges from 3 to 50;

[0094] 3.5 Dissolve 72.3 mg Spiro-OMeTAD in 1 ml of chlorobenzene, then add 28 µl of 4-TBP, 17 µl of Li-TFSI (520 mg Li-TFSI dissolved in 1 ml of acetonitrile) and 8 µl of Co salt (360 mg FK-209 Co dissolved in 1 ml of acetonitrile) to obtain a Spiro-OMeTAD solution, which is the hole transport layer solution.

[0095] 3.6 The hole transport layer solution was spin-coated onto the surface of the interface modification layer at a spin-coating rate of 3800 rpm for 40 s to obtain a smooth and flat hole transport layer.

[0096] 3.7 A gold electrode with a thickness of 100 nm was prepared on the surface of the hole transport layer by vacuum thermal evaporation, and then placed in a drying oven for drying and oxidation for 12 h to obtain a perovskite solar cell.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 1 is that it does not include an interface decoration layer; all other features are the same as in Example 1.

[0099] Comparative Example 2

[0100] The difference between this comparative example and Example 1 is that the interface modification layer uses material M1. All other characteristics are the same as in Example 1. M1 is a monomer of P1, and its structural formula is the same as that of P1, but n=1 in the structural formula.

[0101] Experimental Example 1

[0102] The efficiencies of the perovskite solar cells obtained in Example 1 and Comparative Example 2 were compared, and the photoluminescence spectra of the P1 material used in Example 1 and the M1 material used in Comparative Example 2 were compared with the absorption spectrum of FAPbI3.

[0103] Figure 2 (a) shows a comparison of the normalized photoluminescence spectra of P1 and M1 materials with the normalized absorption spectrum of FAPbI3. Figure 2 (b) shows the UV-Vis absorption spectrum of FAPbI3.

[0104] from Figure 2 It can be seen that the photoluminescence spectrum of P1 material has a large spectral overlap with the absorption spectrum of FAPbI3, while the photoluminescence spectrum of M1 material has less overlap with the absorption spectrum of FAPbI3.

[0105] Furthermore, according to the efficiency test results, the perovskite solar cell in Example 1 has a higher efficiency, while the perovskite solar cell in Comparative Example 2 has a lower efficiency. This is mainly because the interface modification using P1 material in Example 1 caused energy transfer between the P1 material and FAPbI3, which is beneficial for exciton recovery and reuse, thereby improving the efficiency of the perovskite solar cell.

[0106] Experiment Example 2

[0107] The JV curves and water contact angles of the perovskite solar cells obtained in Example 1 and Comparative Example 1 were tested separately at different depths (200 and 500 nm) using 2θ-sin 2 (ψ) Depth-resolved grazing-incidence X-ray diffraction was performed, and the photoelectric conversion efficiency of the perovskite solar cells in Example 1 and Comparative Example 1 was tested over time. The test results are as follows: Figures 3-6 As shown.

[0108] in, Figure 3 This is a comparison graph of the JV curves of the perovskite solar cells in Example 1 and Comparative Example 1. Figure 4 This is a comparison diagram of the water contact angles on the perovskite surfaces in Example 1 and Comparative Example 1. Figure 4 Figure (a) shows the water contact angle analysis of the perovskite surface in Comparative Example 1. Figure 4 (b) is a diagram showing the water contact angle analysis of the perovskite surface in Example 1. Figure 5 The images show a comparison of depth-resolved grazing incidence X-ray diffraction patterns of perovskite solar cells in Example 1 and Comparative Example 1 at different depths. Figure 5 (a) shows a comparison of depth-resolved grazing incidence X-ray diffraction patterns of perovskite solar cells in Example 1 and Comparative Example 1 at a depth of 200 nm. Figure 5 (b) shows a depth-resolved grazing incidence X-ray diffraction comparison of the perovskite solar cells in Example 1 and Comparative Example 1 at a depth of 500 nm. Figure 6 The graph shows the photoelectric conversion efficiency of the perovskite solar cells in Example 1 and Comparative Example 1 over time. It should be noted that... Figures 3-6 In the text, Control represents Comparative Example 1, and With P1 represents Example 1.

[0109] from Figure 3 It can be seen that the photoelectric conversion efficiency of the perovskite solar cell in Example 1 is higher than that in Comparative Example 1; from Figure 4 It can be seen that the water contact angle on the perovskite surface is significantly increased in Example 1, indicating that modification with TADF polymer material is beneficial to improving the hydrophobicity of the perovskite, thereby preventing water vapor intrusion and improving the stability of perovskite solar cells in humid environments; from Figure 5 It can be seen that in Example 1, the scattering peaks of the perovskite absorbing layer at different depths are closer (with smaller slopes), indicating that the introduction of the TADF polymer material compensates for the residual tensile stress in the perovskite absorbing layer and makes the residual stress distribution in the thickness direction more uniform. Figure 6It can be seen that the perovskite solar cell in Comparative Example 1 shows a significant decreasing trend in its power conversion efficiency (PCE) over time, while the perovskite solar cell in Example 1 does not show a significant decreasing trend in its PCE over time, indicating that the perovskite solar cell in Example 1 has higher stability.

[0110] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A perovskite solar cell, characterized in that, The device comprises, from bottom to top, an ITO substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode. The perovskite light-absorbing layer is modified with a thermally activated delayed fluorescence polymer material to form an interface modification layer. The interface modification layer is located between the perovskite light-absorbing layer and the hole transport layer. The perovskite light-absorbing layer is a formamidinium lead triiodide perovskite, and the thermally activated delayed fluorescence polymer material has a wavelength of 550-700 nm.

2. The perovskite solar cell according to claim 1, characterized in that, The structural formula of the thermally activated delayed fluorescence polymer material is shown below: In the formula, ph represents phenyl, and n ranges from 3 to 50.

3. The perovskite solar cell according to claim 1, characterized in that, The ITO substrate includes an ITO / glass substrate or an ITO / PEN substrate.

4. The perovskite solar cell according to claim 1, characterized in that, The electron transport layer includes a tin dioxide electron transport layer.

5. The perovskite solar cell according to claim 1, characterized in that, The hole transport layer includes a 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene hole transport layer.

6. The perovskite solar cell according to claim 1, characterized in that, The metal electrode includes a gold electrode or a silver electrode.

7. The perovskite solar cell according to claim 1, characterized in that, The ITO substrate is the anode electrode, and the metal electrode is the cathode electrode.

8. A method for preparing a perovskite solar cell, used to prepare a perovskite solar cell as described in any one of claims 1-7, characterized in that, Includes the following steps: Step S1: Spin-coat the electron transport layer solution onto the surface of the ITO substrate, and then perform heat treatment to obtain the electron transport layer; Step S2: Dissolve lead triiodide formamidinium in a first solvent to prepare a perovskite precursor solution. In a nitrogen glove box, spin-coat the perovskite precursor solution onto the surface of the electron transport layer, and then perform annealing treatment to obtain a perovskite light-absorbing layer. Step S3: Dissolve the thermally activated delayed fluorescence polymer material in a second solvent to prepare a thermally activated delayed fluorescence polymer material solution, spin-coat the thermally activated delayed fluorescence polymer material solution onto the surface of the perovskite light-absorbing layer, and perform annealing treatment to obtain an interface modification layer; Step S4: Spin-coat the hole transport layer solution onto the surface of the interface modification layer to obtain the hole transport layer; Step S5: A metal electrode is prepared on the surface of the hole transport layer by vacuum thermal evaporation, and then placed in a drying oven for drying and oxidation to obtain a perovskite solar cell.

9. The method for preparing a perovskite solar cell according to claim 8, characterized in that, In step S2, N,N-dimethylformamide and dimethyl sulfoxide are prepared into the first solvent at a volume ratio of 4:

1. The formamidine lead triiodide is dissolved in the first solvent to prepare the perovskite precursor solution, wherein the concentration of formamidine lead triiodide in the perovskite precursor solution is 1.3 mol / L. In a nitrogen glove box, the perovskite precursor solution is spin-coated at a spin-coating rate of 4000-5000 rpm for 20 s, and 0.2 mL of chlorobenzene antisolvent is added dropwise at the 12th-15th s. The solution is then annealed at 150°C for 10-30 min to obtain the perovskite light-absorbing layer.

10. The method for preparing a perovskite solar cell according to claim 8, characterized in that, In step S3, the thermally activated delayed fluorescence polymer material is dissolved in chlorobenzene to prepare a thermally activated delayed fluorescence polymer material solution. The concentration of the thermally activated delayed fluorescence polymer material in the solution is 0.01-8 mg / mL. The thermally activated delayed fluorescence polymer material solution is spin-coated onto the surface of the perovskite light-absorbing layer at a spin-coating rate of 5000-6000 rpm. The solution is then annealed at 80-150℃ for 8-15 min to obtain the interface modification layer.

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