A method for preparing a trans-solar cell based on seed crystal induced growth of perovskite thin film

Abstract

The application discloses a preparation method of a trans solar cell based on seed crystal induced growth of a perovskite film. A chemical general formula of a seed crystal solution of the application is CsPbBr3 / DMSO, the seed crystal solution contains self-dispersed CsPbBr3 small crystal lattices or seed crystals, and the seed crystal solution can be added into a perovskite precursor solution to prepare a perovskite film through seed crystal induced growth. The application can realize a perovskite bottom-up crystallization growth process, realize large-size through-crystals, and effectively inhibit the perovskite from being converted from an alpha photovoltaic phase into a delta phase at room temperature, so that a long-term stable perovskite film can be obtained. The application also uses the seed crystal solution to prepare a preparation method of a perovskite solar cell with a trans (p-i-n) structure, the preparation method is compatible with a low-temperature annealing process of other functional layers, and the preparation method can realize a whole-process low-temperature (≦100 DEG C) preparation of the trans perovskite solar cell.

Description

Technical Field

[0001] The invention belongs to the field of perovskite solar cells and relates to the induction growth of a perovskite film through a seed crystal and the application of the perovskite film in the preparation of a trans-structured perovskite solar cell. Background Art

[0002] Perovskite solar cells are a new type of solar cell technology. Perovskite materials offer excellent optoelectronic properties, solution processing, and high defect tolerance, demonstrating the advantages of low processing costs and scalable production. However, the development of perovskite cells has been plagued by poor quality of the prepared perovskite films, hysteresis effects caused by the migration of methylammonium (MA) ions under operating bias, and device instability. Therefore, obtaining highly crystalline, low-defect, methylammonium-free, and controllable methylammonium-based perovskite films is a key issue.

[0003] A methylammonium (MA)-free FAPbI3 perovskite, where FA is formamidinium HC(NH2)2, has been initially considered a candidate for a highly efficient perovskite component due to its theoretically calculated optical band gap of approximately 1.45 eV, one of the closest theoretical band gap values ​​to the Shockey-Queisser limit. However, at temperatures below 150°C, FAPbI3 perovskite undergoes a transition from a black α-phase to a yellow δ-phase, resulting in photoinactivation of the perovskite and thus affecting device efficiency. Therefore, stabilizing the α-phase FAPbI3 perovskite at ambient temperatures is of great significance for the fabrication of solar cells.

[0004] During the preparation of single-crystal silicon solar cells, a three-dimensionally oriented single-crystal silicon material is grown from a silicon melt around a seed crystal using the Czochralski method. This results in very low concentrations of dislocations and defects, effectively reducing carrier recombination in photovoltaic devices and exhibiting excellent photovoltaic performance. Drawing on this concept, the present invention employs a seed-induced growth method to prepare formamidine-based perovskite thin films, achieving high crystallinity and stabilizing the α phase at room temperature. Summary of the Invention

[0005] The purpose of the present invention is to address the above-mentioned technical problems of poor crystallization quality of formamidine-based perovskite and the problem that the α photovoltaic phase is easily transformed into the δ phase in a room temperature environment, thereby proposing a method for preparing an inverted solar cell based on seed-induced growth of perovskite thin films.

[0006] The specific technical solutions adopted in the present invention are as follows:

[0007] In a first aspect, the present invention provides a method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film, comprising:

[0008] S1, dispersing CsPbBr3 nanocrystals in dimethyl sulfoxide solvent to obtain a self-dispersible seed crystal solution, dissolving lead iodide PbI2 and formamidine iodide FAI in dimethylformamide DMF solution to obtain a FAPbI3 precursor solution, mixing the FAPbI3 precursor solution with the self-dispersible seed crystal solution to form a seed crystal-containing perovskite precursor solution, and allowing the solution to stand for aging;

[0009] S2. Preparing a hole transport layer on the surface of the ITO substrate, and then forming a film of a seed crystal-containing perovskite precursor solution on the hole transport layer after static aging to form a perovskite film. The perovskite film is annealed and used as a light absorbing layer;

[0010] S3, evaporate C on the light absorbing layer 60 Materials, forming an electron transport layer;

[0011] S4, evaporating a bath of copper on the electron transport layer to form a hole blocking layer;

[0012] S5. Vapor-depositing a metal material on the hole blocking layer to form a back electrode layer.

[0013] Preferably, the preparation method of the CsPbBr3 nanocrystals is: under sufficient stirring, a CsBr aqueous solution is added dropwise to a PbBr2 hydrobromic acid solution to react and form a precipitate, and the molar amount of CsBr in all the added CsBr aqueous solution is the same as the molar amount of PbBr2 in the PbBr2 hydrobromic acid solution; after solid-liquid separation, the precipitate is washed and dried to obtain CsPbBr3 nanocrystals.

[0014] Preferably, the concentration of CsPbBr3 in the self-dispersed seed crystal solution is 0.35 mol / L, the concentration of lead iodide PbI2 in the FAPbI3 precursor solution is 1.75M mol / L, and the concentration of formamidine iodide FAI is 1.57 mol / L; the mixing volume ratio of the FAPbI3 precursor solution to the self-dispersed seed crystal solution is 4:1.

[0015] Preferably, the standing aging time of the seed crystal-containing perovskite precursor solution is 0.5 to 2 hours.

[0016] Preferably, in the self-dispersed seed crystal solution, CsPbBr3 exists in the form of a microcrystalline lattice with a particle size distribution of 1 to 3 nm.

[0017] Preferably, the material of the hole transport layer is PTAA, 2PACZ or MeO-2PACZ.

[0018] Preferably, the seed crystal-containing perovskite precursor solution is formed into a film on the hole transport layer by any one of spin coating, blade coating, and spray coating; the annealing temperature of the perovskite film is controlled to be 30°C to 100°C, the annealing time is controlled to be 10 to 60 minutes, and the thickness of the perovskite film is 300nm to 1μm.

[0019] Preferably, the electron transport layer, the hole blocking layer and the back electrode layer are all evaporated by a vapor phase vacuum thermal evaporation method, and the thicknesses are preferably 25 nm, 5 nm and 10 nm, respectively.

[0020] Preferably, the metal material used for the back electrode layer is copper, silver, aluminum or gold.

[0021] In a second aspect, the present invention provides an inverted solar cell prepared by the preparation method described in any one of the solutions of the first aspect.

[0022] The purpose of the present invention is to address the above-mentioned technical problems of poor crystallization quality of formamidite perovskite and the easy transition from α photovoltaic phase to δ phase in a room temperature environment. A seed crystal induced growth of formamidite perovskite thin film is proposed, and applied to the preparation of inverted (pin) structure perovskite solar cells. Since the seed crystal is located at the bottom of the precursor solution, a bottom-up crystallization growth mode is induced, so that the formamidite perovskite grains present large-sized through-crystals, effectively reducing the grain boundaries between adjacent grains; suppressing the non-radiative recombination of carriers at the grain boundaries, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. In addition, since there are no methylammonium (MA) ions in the formamidite perovskite component, the forward and reverse scanning hysteresis phenomenon caused by the migration of methylammonium ions under the working bias is suppressed. The seed crystal induced growth of formamidine-based perovskite film is applied to a trans (pin) structured perovskite solar cell, which matches the energy bands of other functional layers and is compatible with the low-temperature annealing process of other functional layers, and can realize the preparation of trans perovskite solar cells at low temperatures (≦100°C) throughout the entire process.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In the present invention, since the seed crystal is located at the bottom of the precursor solution, a bottom-up crystallization growth mode is induced, so that the formamidinium-based perovskite grains present large-sized through-crystals, effectively reducing the grain boundaries between adjacent grains; inhibiting the non-radiative recombination of carriers at the grain boundaries, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. In addition, since there are no methylammonium (MA) ions in the formamidinium-based perovskite component, the forward and reverse scanning hysteresis phenomenon caused by the migration of methylammonium ions under the working bias is suppressed. The formamidinium-based perovskite film induced by the seed crystal is applied to a perovskite solar cell with an inverted (pin) structure, matching the energy bands of other functional layers and being compatible with the low-temperature annealing process of other functional layers, and can realize the whole process of low temperature (≦100°C) to prepare an inverted perovskite solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Comparative SEM images of the cross sections of FAPbI3 perovskite films prepared using seed solution, directly adding seed crystals, and without adding seed solution;

[0026] Figure 2 The SEM comparison of the cross section of FAPbI3 perovskite film prepared using seed solution and without seed method;

[0027] Figure 3 JV curves of perovskite solar cells prepared using seed crystals (Example 1) and without seed crystals (Comparative Example 1);

[0028] Figure 4 This is the JV curve of the perovskite solar cell prepared in Comparative Example 1. DETAILED DESCRIPTION

[0029] The specific implementation of the method for preparing an inverse perovskite solar cell of the present invention is further described below with reference to specific embodiments.

[0030] The core of the present invention is that when preparing a perovskite film on a hole transport layer, a self-dispersed seed crystal solution with the chemical formula CsPbBr3 / DMSO is added to the perovskite precursor solution. The seed crystal solution contains self-dispersed CsPbBr3 micro-crystals with a particle size distribution of 1 to 3 nm, and the seed crystal solution has a characteristic fluorescence of about 560 nm, which proves the existence of the lattice. This self-dispersed seed crystal solution can be added to the perovskite precursor solution to prepare the perovskite film through seed-induced growth, thereby realizing the bottom-up crystallization growth process of the perovskite, achieving large-sized through-crystals, and effectively inhibiting the α photovoltaic phase transition of the formamidinium-based perovskite to the δ phase at room temperature, thereby obtaining a long-term stable perovskite film. Moreover, in the process of preparing a trans (pin) structured perovskite solar cell using the seed-containing perovskite precursor solution of the present invention, it is compatible with the low-temperature annealing process in other functional layers, and can achieve a low-temperature (≦100°C) preparation of the trans perovskite solar cell throughout the entire process.

[0031] The present invention will first specifically describe a method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film, the steps of which are as follows:

[0032] S1. Disperse CsPbBr3 nanocrystals in dimethyl sulfoxide solvent to obtain a self-dispersed seed crystal solution, dissolve lead iodide PbI2 and formamidine iodide FAI in dimethylformamide DMF solution to obtain a FAPbI3 precursor solution without methylammonium component, mix the FAPbI3 precursor solution with the self-dispersed seed crystal solution to form a seed crystal-containing perovskite precursor solution, and let it stand for aging.

[0033] It should be noted that the CsPbBr3 nanocrystals of the present invention can be synthesized using inorganic CsPb and PbBr2 as raw materials using a solution method or an antisolvent capture method. A method for preparing CsPbBr3 nanocrystals using a solution method is provided below: A CsBr aqueous solution is dropwise added to a PbBr2 hydrobromic acid solution under sufficient stirring to react and form a precipitate, wherein the molar amount of CsBr in the total dropwise added CsBr aqueous solution is the same as the molar amount of PbBr2 in the PbBr2 hydrobromic acid solution; after solid-liquid separation, the precipitate is washed and dried to obtain CsPbBr3 nanocrystals.

[0034] It should be noted that when preparing the above-mentioned seed-containing perovskite precursor solution, the components need to be properly proportioned. As a preferred embodiment of the present invention, the components can be proportioned within the following range: the concentration of CsPbBr3 in the self-dispersible seed solution is 0.35 mol / L, the concentration of lead iodide (PbI2) in the FAPbI3 precursor solution is 1.75 M mol / L, and the concentration of formamidine iodide (FAI) is 1.57 mol / L; the volume ratio of the FAPbI3 precursor solution to the self-dispersible seed solution is 4:1.

[0035] It should be noted that the standing aging time of the above-mentioned seed-containing perovskite precursor solution can be optimized according to the actual process. As a preferred embodiment of the present invention, the standing aging time of the seed-containing perovskite precursor solution can be controlled to be 0.5 to 2 hours.

[0036] S2. A hole transport layer is prepared on the surface of the ITO substrate, and then a seed crystal-containing perovskite precursor solution that has been statically aged is formed into a film on the hole transport layer to form a perovskite film. The perovskite film is annealed and used as a light absorption layer.

[0037] It should be noted that the hole transport layer material in the present invention can be PTAA, 2PACZ, or MeO-2PACZ. The hole transport layer material can be applied to the ITO substrate by spin coating, blade coating, etc. To ensure film formation reliability, the surface of the ITO substrate is preferably subjected to lattice UV ozone treatment.

[0038] It should be noted that the seed crystal-containing perovskite precursor solution is formed into a film on the hole transport layer by any of spin coating, doctor blade coating, and spray coating. If a spin coating process is adopted, the perovskite precursor solution can be spin-coated on the substrate at a spin coating rate of 3000 to 6000 rpm. If a doctor blade coating process is adopted, the perovskite precursor solution can be doctor blade coated on the substrate at a doctor blade coating rate of 200 nm to 1 μm / s. The doctor blade coating process requires air flow to blow the film so that the perovskite precursor solution achieves a supersaturated solution and precipitates crystals.

[0039] It should be noted that the annealing temperature of the above perovskite film is controlled to be 30° C. to 100° C., the annealing time is controlled to be 10 to 60 minutes, and the thickness of the perovskite film is 300 nm to 1 μm.

[0040] S3, evaporate C on the light absorbing layer 60 material, forming an electron transport layer.

[0041] S4. Vapor-depositing a bath of copper on the electron transport layer to form a hole blocking layer.

[0042] S5. Vapor-depositing a metal material on the hole blocking layer to form a back electrode layer.

[0043] It should be noted that the above-mentioned electron transport layer, hole blocking layer and back electrode layer are preferably evaporated by vapor phase vacuum thermal evaporation, and the thickness of the electron transport layer, hole blocking layer and back electrode layer are preferably 25nm, 5nm and 10nm respectively.

[0044] It should be noted that the metal material used for the back electrode layer is preferably copper, silver, aluminum or gold.

[0045] The inverted solar cell prepared by the above preparation method has a multi-layer inverted (pin) structure, which comprises, from bottom to top, an ITO substrate, a hole transport layer, a light absorbing layer, an electron transport layer, a hole blocking layer and a back electrode layer.

[0046] In order to better demonstrate the device performance of the inverted solar cell prepared by the above preparation method, its technical effects are presented below through corresponding examples and comparative examples.

[0047] Example 1

[0048] This embodiment provides a method for preparing an inverted solar cell based on seed-induced growth of a perovskite film. The method utilizes a self-dispersed seed solution to induce the growth of a methylammonium (MA)-free perovskite film, and is applied to an inverted (pin) structure perovskite solar cell. The method specifically includes the following process steps:

[0049] 1) ITO substrate preparation:

[0050] A 15 mm × 15 mm Sn-doped In2O3 (ITO) conductive glass with a transmittance of ≥84%, a square resistance of ≤15 Ω was used as the device substrate material. The ITO substrate was treated with UV ozone and set aside.

[0051] 2) Preparation of hole transport layer:

[0052] A polymer PTAA material is used as a hole transport layer material and is spin-coated on an ITO substrate treated with UV ozone to form a hole transport layer.

[0053] 3) Preparation of light-absorbing layer:

[0054] Preparation of CsPbBr3 nanocrystals: Dissolve 10 mmol of PbBr2 in 8 ml of hydrobromic acid to obtain a PbBr2 hydrobromic acid solution. Dissolve 10 mmol of CsBr in 12 ml of deionized water to obtain a CsBr aqueous solution. The entire CsBr aqueous solution is then added dropwise to the entire PbBr2 hydrobromic acid solution while maintaining sufficient stirring. At the end of the reaction, remove the supernatant of the resulting orange-red precipitate, centrifuge, and rinse several times with anhydrous isopropanol. The resulting precipitate is dried in a vacuum oven at 90°C for 12 hours to obtain CsPbBr3 nanocrystals.

[0055] Preparation of a self-dispersible seed crystal solution: CsPbBr3 nanocrystals were dispersed in a dimethyl sulfoxide (DMSO) solution to produce a self-dispersible colorless solution containing a CsPbBr3 concentration of 0.35 mM. This self-dispersible seed crystal solution contained microscopic CsPbBr3 lattices or seeds. Measurement of the seed crystal size distribution using a laser particle size analyzer revealed a distribution of approximately 2 nm. Spectral analysis of the self-dispersible seed crystal solution using a fluorescence spectrometer revealed characteristic fluorescence at approximately 560 nm, confirming that the CsPbBr3 in the solution existed in the form of microscopic lattices.

[0056] Preparation of a seed-containing perovskite precursor solution: Dissolve 490.5 mg of PbI2 and 164 mg of FAI in 0.608 ml of dimethylformamide (DMF) to obtain a FAPbI3 precursor solution. Add a pre-prepared 0.35 mM CsPbBr3 / DMSO self-dispersible seed solution to the FAPbI3 precursor solution at a volume ratio of 1:4. Mix thoroughly to obtain a seed-containing perovskite precursor solution with a total concentration of 1.4 mol / L. The seed-containing perovskite precursor solution was thoroughly stirred and aged for 30 minutes before use.

[0057] Perovskite film formation annealing: The seed crystal perovskite precursor solution was spin-coated on the PTAA hole transport layer on the ITO substrate at a speed of 4000 rpm. The perovskite film was deposited by the anti-solvent method during the spin coating process, and then annealed at 100°C for 20 minutes. The thickness of the perovskite film was 800 nm. The SEM cross-section of the film was as follows: Figure 1 As shown in a), the film X-ray diffraction pattern is as follows Figure 2 As shown in "Adding Seed Solution".

[0058] 4) Preparation of electron transport layer:

[0059] The C 60 The material is evaporated on the light absorbing layer, and the evaporation rate An electron transport layer was formed to a thickness of 25 nm.

[0060] 5) Preparation of hole blocking layer:

[0061] Bathocuproin (BCP) material was evaporated onto the electron transport layer by vapor phase vacuum thermal evaporation method, and the evaporation rate was A hole blocking layer with a thickness of 5 nm was formed.

[0062] 6) Preparation of back electrode layer:

[0063] Copper (Cu) or silver (Ag) is deposited on the hole blocking layer by vapor phase vacuum thermal evaporation method, and the evaporation rate is A back electrode layer with a thickness of 100 nm was formed.

[0064] The test results show that the inverted (pin) perovskite solar cell prepared in this embodiment has good photoelectric conversion performance under standard simulated sunlight, with an open circuit voltage of 1.10 V and a short circuit current density of 24.24 mA / cm 2 , the filling factor is 82.3%, and the photoelectric conversion efficiency is 21.94%. Figure 3 As shown in the "add seed crystal" group; no hysteresis phenomenon was shown in the JV forward and reverse scan test, and its steady-state photoelectric conversion efficiency was 21.81% under maximum power point tracking.

[0065] Comparative Example 1

[0066] The preparation method of the inverted solar cell in this comparative example is basically the same as that in Example 1, with the only difference being that the seed crystal powder (non-self-dispersed solution) is directly introduced to prepare the methylammonium (MA)-free perovskite precursor solution, and applied to the preparation of the light absorption layer in the inverted (pin) structure perovskite solar cell, that is, the light absorption layer in step 3) in Example 1 is prepared as follows:

[0067] Preparation of the perovskite precursor solution: 490.5 mg of PbI2, 164 mg of FAI, and 30.8 mg of CsPbBr3 seed crystals were weighed and dissolved in 0.76 ml of a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (0.608 ml of DMF and 0.152 ml of DMSO) at a molar ratio of 1:0.95:0.05. This solution containing seed crystals was stirred thoroughly and aged for 30 minutes before use.

[0068] The perovskite precursor solution containing the seed crystal was spin-coated at 4000 rpm on the PTAA hole transport layer sprinkled on the ITO substrate. During the spin-coating process, the perovskite film was deposited using the anti-solvent method, and then annealed at 100°C for 20 minutes to form a light-absorbing layer.

[0069] The preparation method of other functional layers in the inverted (pin) structured perovskite solar cell is the same as that in Example 1 and will not be repeated here.

[0070] In this comparative example 1, Figure 1As shown in (b), the perovskite film thickness is 800 nanometers, the same as in Example 1. However, the film cross-section shows a stack of small perovskite grains, which cannot form through-crystals. Consequently, there are too many grain boundaries in the perovskite film, causing carrier recombination at the grain boundaries. This is reflected in the device's reduced photoelectric conversion performance, with an open-circuit voltage of 1.03 V and a short-circuit current density of 23.51 mA / cm. 2 , the filling factor is 83.1%, and the photoelectric conversion efficiency is 20.15%. Figure 4 shown.

[0071] Comparative Example 2

[0072] The method for preparing the inverted solar cell in this comparative example is basically the same as that in Example 1, except that neither a seed crystal solution nor seed crystal powder is directly added to prepare the perovskite precursor solution, and the solution is applied to prepare the light absorption layer in the inverted (pin) perovskite solar cell. That is, the light absorption layer in step 3) in Example 1 is prepared as follows:

[0073] Preparation of methylammonium (MA)-free perovskite precursor solution: 465.9 mg of PbI2 (0.95 mmol), 164.6 mg of FAI (0.95 mmol), 19.52 mg of PbBr2 (0.05 mmol), 13.82 mg of CsI2 (0.05 mmol), and 11.32 mg of PbBr2 (0.95 mmol) were weighed separately and dissolved in 0.76 ml of a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (containing 0.608 ml of DMF and 0.152 ml of DMSO). The solution was stirred and mixed thoroughly to obtain a methylammonium (MA)-free perovskite precursor solution with a concentration of 1.4 mol / L. The solution was aged for 30 minutes before use.

[0074] The perovskite precursor solution was spin-coated on the PTAA hole transport layer on the ITO substrate at a speed of 4000 rpm. The perovskite was deposited by the anti-solvent method during the spin-coating process, and then annealed at 100°C for 20 minutes to form a light-absorbing layer.

[0075] The preparation method of other functional layers in the inverted (pin) structured perovskite solar cell is the same as that in Example 1 and will not be repeated here.

[0076] The thickness of the perovskite film in the light-absorbing layer obtained in Comparative Example 2 is 800 nanometers, and the SEM cross-section of the film is as follows: Figure 1 As shown in c), the film X-ray diffraction pattern is as follows Figure 2The test results show that the inverted (pin) perovskite solar cell has good photoelectric conversion performance under standard simulated sunlight, with an open circuit voltage of 1.01V and a short circuit current density of 23.60mA / cm 2 , the fill factor is 80.2%, the photoelectric conversion efficiency is 19.14%, and it shows obvious hysteresis in the JV forward and reverse scan test, such as Figure 3 As shown in the "no seed crystal" group.

[0077] Example 2

[0078] This embodiment provides a method for preparing an inverted solar cell based on seed-induced growth of a perovskite film. The method utilizes a self-dispersed seed solution to induce the growth of a methylammonium (MA)-free perovskite film, and is applied to an inverted (pin) structure perovskite solar cell. The method specifically includes the following process steps:

[0079] 1) ITO substrate preparation:

[0080] A 15 mm × 15 mm Sn-doped In2O3 (ITO) conductive glass with a transmittance of ≥84%, a square resistance of ≤15 Ω was used as the device substrate material. The ITO substrate was treated with UV ozone and set aside.

[0081] 2) Preparation of hole transport layer:

[0082] A small molecule organic material 2PACZ is used as a hole transport layer material. The small molecule organic material 2PACZ is dissolved in ethanol to form a solution with a concentration of 0.35 mmol / L. The solution is spin-coated on an ITO substrate treated with UV ozone to form a hole transport layer.

[0083] 3) Preparation of light-absorbing layer:

[0084] Preparation of CsPbBr3 nanocrystals: Dissolve 10 mmol of PbBr2 in 8 ml of hydrobromic acid to obtain a PbBr2 hydrobromic acid solution. Dissolve 10 mmol of CsBr in 12 ml of deionized water to obtain a CsBr aqueous solution. The entire CsBr aqueous solution is then added dropwise to the entire PbBr2 hydrobromic acid solution while maintaining sufficient stirring. At the end of the reaction, remove the supernatant of the resulting orange-red precipitate, centrifuge, and rinse several times with anhydrous isopropanol. The resulting precipitate is dried in a vacuum oven at 90°C for 12 hours to obtain CsPbBr3 nanocrystals.

[0085] Preparation of a self-dispersible seed crystal solution: CsPbBr3 nanocrystals were dispersed in a dimethyl sulfoxide (DMSO) solution to produce a self-dispersible colorless solution containing a CsPbBr3 concentration of 0.35 mM. This self-dispersible seed crystal solution contained microscopic CsPbBr3 lattices or seeds. Measurement of the seed crystal size distribution using a laser particle size analyzer revealed a distribution of approximately 2 nm. Spectral analysis of the self-dispersible seed crystal solution using a fluorescence spectrometer revealed characteristic fluorescence at approximately 560 nm, confirming that the CsPbBr3 in the solution existed in the form of microscopic lattices.

[0086] Preparation of a seed-containing perovskite precursor solution: Dissolve 490.5 mg of PbI2 and 164 mg of FAI in 0.608 ml of dimethylformamide (DMF) to obtain a FAPbI3 precursor solution. Add a pre-prepared 0.35 mM CsPbBr3 / DMSO self-dispersible seed solution to the FAPbI3 precursor solution at a volume ratio of 1:4. Mix thoroughly to obtain a seed-containing perovskite precursor solution with a total concentration of 1.4 mol / L. The seed-containing perovskite precursor solution was thoroughly stirred and aged for 30 minutes before use.

[0087] Perovskite film formation annealing: The seed crystal perovskite precursor solution was spin-coated on the PTAA hole transport layer on the ITO substrate at a speed of 4000 rpm. The perovskite film was deposited by the anti-solvent method during the spin coating process, and then annealed at 100°C for 20 minutes. The thickness of the perovskite film was 800 nm. The SEM cross-section of the film was as follows: Figure 1 As shown in a), the film X-ray diffraction pattern is as follows Figure 2 As shown in "Adding Seed Solution".

[0088] 4) Preparation of electron transport layer:

[0089] The C 60 The material is evaporated on the light absorbing layer, and the evaporation rate An electron transport layer was formed to a thickness of 25 nm.

[0090] 5) Preparation of hole blocking layer:

[0091] Bathocuproin (BCP) material was evaporated onto the electron transport layer by vapor phase vacuum thermal evaporation method, and the evaporation rate was A hole blocking layer with a thickness of 5 nm was formed.

[0092] 6) Preparation of back electrode layer:

[0093] Copper (Cu) or silver (Ag) is deposited on the hole blocking layer by vapor phase vacuum thermal evaporation method, and the evaporation rate is A back electrode layer with a thickness of 100 nm was formed.

[0094] The test showed that the inverted (pin) perovskite solar cell has good photoelectric conversion performance under standard simulated sunlight, with an open circuit voltage of 1.08V and a short circuit current density of 24.83mA / cm 2 , the filling factor is 80.01%, and the photoelectric conversion efficiency is 21.37%.

[0095] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that the technical solutions described in the above-described embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film, characterized in that: include: S1, dispersing CsPbBr3 nanocrystals in dimethyl sulfoxide solvent to obtain a self-dispersible seed crystal solution, dissolving lead iodide PbI2 and formamidine iodide FAI in dimethylformamide DMF solution to obtain a FAPbI3 precursor solution, mixing the FAPbI3 precursor solution with the self-dispersible seed crystal solution to form a seed crystal-containing perovskite precursor solution, and allowing the solution to stand for aging; The preparation method of the CsPbBr3 nanocrystals comprises: adding a CsBr aqueous solution dropwise to a PbBr2 hydrobromic acid solution under sufficient stirring to react and form a precipitate, wherein the molar amount of CsBr in the entire added CsBr aqueous solution is the same as the molar amount of PbBr2 in the PbBr2 hydrobromic acid solution; after solid-liquid separation, washing and drying the precipitate to obtain CsPbBr3 nanocrystals; In the self-dispersed seed crystal solution, CsPbBr3 exists in the form of a microcrystalline lattice with a particle size distribution of 1 to 3 nm; S2. Preparing a hole transport layer on the surface of the ITO substrate, wherein the material of the hole transport layer is PTAA or 2PACZ, and then forming a film of a seed crystal-containing perovskite precursor solution on the hole transport layer after static aging to form a perovskite film, and the perovskite film is annealed to serve as a light absorption layer; S3, evaporate C on the light absorbing layer 60 Materials, forming an electron transport layer; S4, evaporating a bathcopper ion (BCP) material on the electron transport layer to form a hole blocking layer; S5. Vapor-depositing a metal material on the hole blocking layer to form a back electrode layer.

2. The method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film according to claim 1, wherein: The concentration of CsPbBr3 in the self-dispersed seed crystal solution is 0.35 mol / L, the concentration of lead iodide PbI2 in the FAPbI3 precursor solution is 1.75M mol / L, and the concentration of formamidine iodide FAI is 1.57 mol / L; the mixing volume ratio of the FAPbI3 precursor solution to the self-dispersed seed crystal solution is 4:

1.

3. The method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film according to claim 1, wherein: The standing aging time of the seed crystal-containing perovskite precursor solution is 0.5 to 2 hours.

4. The method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film according to claim 1, wherein: The seed crystal-containing perovskite precursor solution is formed into a film on the hole transport layer by any one of spin coating, blade coating, and spray coating; the annealing temperature of the perovskite film is controlled to be 30°C to 100°C, the annealing time is controlled to be 10 to 60 minutes, and the thickness of the perovskite film is 300nm to 1μm.

5. The method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film according to claim 1, wherein: The electron transport layer, the hole blocking layer and the back electrode layer are all evaporated by a vapor phase vacuum thermal evaporation method.

6. The method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film according to claim 5, characterized in that: The thicknesses of the electron transport layer, the hole blocking layer and the back electrode layer are 25 nm, 5 nm and 10 nm respectively.

7. The method for preparing an inverted solar cell based on seed-induced growth of a perovskite thin film according to claim 1, wherein: The metal material used for the back electrode layer is copper, silver, aluminum or gold.

8. An inverted solar cell prepared by the preparation method according to any one of claims 1 to 7.

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