Perovskite solar cell and preparation method thereof

Abstract

The application provides a perovskite solar cell and a preparation method thereof. The cell comprises an ITO substrate, an SnO2 electron transport layer, a perovskite light absorption layer, a passivation layer, a hole transport layer and a gold electrode layer arranged in sequence. The passivation layer is a halogen salt containing a heterocyclic ammonium salt cation (4,5-dihydroimidazole-2-hydrazine hydrogen). The application deposits the halogen salt containing the heterocyclic ammonium salt cation (4,5-dihydroimidazole-2-hydrazine hydrogen) at the interface between the perovskite light absorption layer and the hole transport layer, passivates the shallow and deep defects, inhibits non-radiative recombination and improves interface charge extraction, so that the device efficiency and stability are improved.

Description

TECHNICAL FIELD

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

[0002] With the vigorous development of organic-inorganic hybrid perovskite materials, the device certification efficiency has reached 25.7%. However, due to the mixed cations and anions in the perovskite material, a large number of adverse defects will be generated in the heat treatment process, which will undoubtedly adversely affect the efficiency and stability of the cell. Among the different types of defects involved in the perovskite material, the point defects with low formation energy are the most obvious, because the point defects with low formation energy are likely to become the location of non-radiative recombination, thereby causing the reduction of open-circuit voltage and device efficiency. At the same time, due to the ionic nature and good ion migration speed of the perovskite material, the charged point defects will migrate to the interface under the action of the electric field, thereby causing the accelerated degradation of the light absorption layer. Therefore, in order to obtain a high-performance and stable perovskite solar cell, not only the interface defects leading to the inhibition of non-radiative recombination need to be passivated, but also the ion migration responsible for long-term stability under different environments needs to be effectively inhibited, which is crucial.

[0003] So far, many functional molecules have been used to passivate lead-based defects. However, the inorganic ions and inherent chemical instability of the organic molecular layer limit their promotion in practical applications. Therefore, it is urgent to develop a simple and effective strategy to deal with lead-based defects at the interface to obtain high-efficiency perovskite photovoltaic devices with good long-term stability. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a perovskite solar cell and a preparation method thereof, which has a higher photoelectric conversion efficiency.

[0005] The present application provides a perovskite solar cell, which comprises an ITO substrate, a SnO2 electron transport layer, a perovskite light absorption layer, a passivation layer, a hole transport layer and a gold electrode layer arranged in sequence.

[0006] The passivation layer is a halide salt containing heterocyclic ammonium salt cation (4,5-dihydroimidazole-2-hydrazine hydrogen).

[0007] The solar cell provided by the present application comprises an ITO substrate. In specific embodiments, the present application uses ITO conductive glass as the ITO substrate. The ITO conductive glass is cleaned and dried before use, and then subjected to UV surface treatment.

[0008] The solar cell provided by the application comprises an SnO2 electron transport layer, which is prepared by annealing after deposition of SnO2 solution.

[0009] The solar cell provided by the application comprises a perovskite light absorption layer; the material of the perovskite light absorption layer is (FAPbI3) 0.95 (MAPbBr3) 0.05 The thickness of the perovskite light absorption layer is not less than 100 nm. The perovskite light absorption layer is prepared from a perovskite precursor solution; the preparation process of the perovskite precursor solution is as follows: methyammonium iodide, methylammonium bromide, lead iodide and lead bromide are weighed and dissolved in an organic solvent, and then filtered after sufficient stirring to obtain the perovskite precursor solution.

[0010] The solar cell provided by the application comprises a passivation layer; the passivation layer is a halogen salt substance containing heterocyclic ammonium salt cations (4,5-dihydroimidazole-2-hydrazine hydrogen); the passivation layer is one or more of 4,5-dihydroimidazole-2-hydrazine hydrogen iodide salt, 4,5-dihydroimidazole-2-hydrazine hydrogen bromide salt and 4,5-dihydroimidazole-2-hydrazine hydrogen chloride salt. The thickness of the passivation layer is 5-20 nm.

[0011] The solar cell provided by the application comprises a hole transport layer; the thickness of the hole transport layer is 150-220 nm.

[0012] The solar cell provided by the application comprises a gold electrode layer; the thickness of the gold electrode layer is 65-85 nm.

[0013] The application provides a preparation method of the perovskite solar cell.

[0014] SnO2 precursor solution is deposited on the ITO substrate, and annealing is performed to obtain the SnO2 electron transport layer;

[0015] The perovskite precursor solution is spin-coated on the SnO2 electron transport layer and heated to obtain the perovskite light absorption layer;

[0016] The passivation layer solution is spin-coated on the perovskite light absorption layer and heated to obtain the passivation layer, and the passivation layer is a halogen salt substance containing heterocyclic ammonium salt cations (4,5-dihydroimidazole-2-hydrazine hydrogen);

[0017] The hole transport layer solution is spin-coated on the passivation layer to obtain the hole transport layer;

[0018] A gold electrode layer is prepared on the hole transport layer by a vacuum evaporation method to obtain the perovskite solar cell.

[0019] The SnO2 precursor solution is deposited on the ITO substrate, and annealing is performed to obtain the SnO2 electron transport layer.

[0020] The perovskite precursor solution is spin-coated on the SnO2 electron transport layer and heated to obtain the perovskite light absorption layer. 2 The spin-coating speed of the perovskite precursor solution is 3000-5000 rpm. The concentration of the perovskite precursor solution is 1.4-1.8 mol / mL. The perovskite precursor solution is an organic mixed solvent of dimethyl sulfoxide and dimethylformamide. The volume of dimethylformamide in the perovskite precursor solution is 4 times that of dimethyl sulfoxide.

[0021] The passivation layer solution is spin-coated on the perovskite light absorption layer and heated to obtain the passivation layer. The passivation layer solution is prepared by dissolving a halogen salt containing heterocyclic ammonium cation (4,5-dihydroimidazole-2-hydrazine hydrogen) in a solvent and stirring. The concentration of the halogen salt containing heterocyclic ammonium cation (4,5-dihydroimidazole-2-hydrazine hydrogen) in the passivation layer solution is 10-50 mmol / mL. The solvent is isopropyl alcohol. The use amount of the passivation layer solution is 15-25 μL / cm 2 The spin-coating speed of the passivation layer solution is 3000-5000 rpm. The heating temperature of the passivation layer solution is 90-120 ℃, and the heating time of the passivation layer solution is 5-10 min.

[0022] The hole transport layer solution is spin-coated on the passivation layer to obtain the hole transport layer. The hole transport layer solution is prepared by adding tributyl phosphate (TBP), lithium bis-trifluoromethylsulfonylimide (LiTFSI), and bis-trifluoromethanesulfonylimide salt (FK209Co(III)) to spiro-OMeTAD and dissolving in chlorobenzene solvent. In a specific embodiment, the formula of the hole transport layer solution is: spiro-OMeTAD is 72.3 mg / mL, tributyl phosphate (TBP) is 28.8 μL, lithium bis-trifluoromethylsulfonylimide (LiTFSI) is 17.5 μL, bis-trifluoromethanesulfonylimide salt (FK209Co(III)) is 8 μL, and 1 mL of chlorobenzene solvent is used. The use amount of the hole transport layer solution is 10-15 μL / cm 2The spin coating speed is 3000-5000 rpm.

[0023] The application provides a perovskite solar cell, which comprises an ITO substrate, an SnO2 electron transport layer, a perovskite light absorption layer, a passivation layer, a hole transport layer and a gold electrode layer arranged in sequence; the passivation layer is a halogen salt substance containing heterocyclic ammonium salt cations (4, 5-dihydroimidazole-2-hydrazine hydrogen). BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a whole structure diagram of the perovskite solar cell of the embodiment 4-6 of the application with the passivation layer prepared in the application;

[0025] Figure 2 It is an X-ray diffraction image of the perovskite solar cell of the embodiment 2, the comparative example 1, 4, 5-dihydroimidazole-2-hydrazine hydrogen iodate and lead iodide single reaction and the thin film of 4, 5-dihydroimidazole-2-hydrazine hydrogen iodate of the application;

[0026] Figure 3 It is an SEM image of the perovskite surface of the comparative example 1 and the embodiment 2 of the application;

[0027] Figure 4 It is an ultraviolet-visible absorption spectrum of the perovskite thin film of the embodiment 1-3 of the application and the comparative example 1 of the passivation treatment;

[0028] Figure 5 It is an I-V test result of the perovskite solar cell of the embodiment 4-6 of the application with different concentrations of 4, 5-dihydroimidazole-2-hydrazine hydrogen iodate passivation treatment and the comparative example 2. DETAILED DESCRIPTION

[0029] In order to further illustrate the application, the perovskite solar cell and the preparation method thereof provided by the application are described in detail below in combination with the embodiments, but they should not be understood as limiting the protection scope of the application.

[0030] The thin film structure of ITO / SnO2 / perovskite light absorption layer / passivation layer prepared by the method of the application

[0031] Embodiment 1

[0032] 1) ITO conductive glass is cut into 25mm x 25mm size, and is cleaned with conductive glass cleaning solution, deionized water and ethanol respectively, and is placed into an oven for drying, and is subjected to UV surface treatment to obtain an ITO substrate.

[0033] SnO2 compact layer preparation: 1 mL SnO2 colloidal dispersion solution was diluted 7 times with deionized water to obtain a SnO2 solution. Further, the solution method operation method is: depositing the SnO2 precursor solution on the ITO substrate; the annealing temperature is 150°C, and the annealing time is 40 min.

[0034] 2) Perovskite light absorption layer preparation:

[0035] 2-1) Take 1.33 mol of formamidinium hydriodide, 0.07 mol of methylammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide, and dissolve them in 1 mL of dimethyl sulfoxide and dimethylformamide, with a volume ratio of dimethyl sulfoxide to dimethylformamide of 1:4, to obtain a solution with a concentration of 1.4 mol / mL. After stirring on a stirring table for 5 h to fully dissolve, filter the solution with a 45 μm filter head to obtain a perovskite precursor solution;

[0036] 2-2) Take 90 μL of the above perovskite precursor solution and drop it on the ITO substrate covered with the SnO2 compact layer preheated at 70°C, spin it at 1000 rpm for 10 s, spin it at 4500 rpm for 30 s in the second step, and add 150 μl of chlorobenzene 15-20 s before the end of the spin coating, and then place it on a 150°C heating table for 15 min.

[0037] 3) Passivation layer preparation

[0038] 3-1) Dissolve 10 mmol of 4,5-dihydroimidazole-2-hydrazine hydriodide powder in 1 mL of IPA to obtain a solution of 10 mmol / mL, and stir it on a stirring table at room temperature for 2 h to fully dissolve, and then filter the solution with a 45 μm filter head.

[0039] 3-2) Take 90 μL of the perovskite solution and drop it on the cooled perovskite light absorption layer obtained from step 2), spin it at 4000 rpm for 30 s, and then place it on a 100°C heating table for 5 min.

[0040] The prepared device is from bottom to top: ITO substrate, SnO2 compact layer (i.e., electron transport layer), perovskite light absorption layer ((FAPbI3) 0.95 (MAPbBr3) 0.05 perovskite material), passivation layer (4,5-dihydroimidazole-2-hydrazine hydriodide).

[0041] Example 2

[0042] 1) Cut ITO conductive glass into 25 mm x 25 mm size, and wash it with conductive glass cleaning solution, deionized water, and ethanol, and then dry it in an oven, and perform UV surface treatment to obtain an ITO substrate.

[0043] Sn02dense layer preparation: 1 mL Sn02colloidal dispersion was diluted 7 times with deionized water to obtain a Sn02solution. Further, the solution method operation method is: Sn02precursor solution is deposited on the ITO substrate; the annealing temperature is 150°C, and the annealing time is 40 min.

[0044] 2) Perovskite light absorption layer preparation:

[0045] 2-1) 1.33 mol of formamidinium hydriodide, 0.07 mol of methylammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide were weighed and dissolved in 1 mL of dimethyl sulfoxide and dimethylformamide, the volume ratio of dimethyl sulfoxide and dimethylformamide was 1:4, the concentration of the obtained solution was 1.4 mol / mL, after stirring for 5 h to fully dissolve, the solution was filtered with a 45 pm filter head to obtain a perovskite precursor solution.

[0046] 2-2) 90 μL of the above perovskite precursor solution was dropped on the ITO substrate covered with the Sn02dense layer preheated at 70°C, and was spin-coated at 1000 rpm for 10 s, 4500 rpm for 30 s in the second step, 150 μl of chlorobenzene was added 15-20 s before the end of spin-coating, and after spin-coating, it was placed on a heating stage at 150°C for 15 min.

[0047] 3) Passivation layer preparation

[0048] 3-1) 20 mmol of 4,5-dihydroimidazole-2-hydrazine hydriodide powder was dissolved in 1 mL of IPA, the obtained solution was 20 mmol / mL, and after stirring for 2 h to fully dissolve, the solution was filtered with a 45 pm filter head.

[0049] 3-2) 90 μL of the perovskite solution was dropped on the cooled perovskite light absorption layer obtained from step 2), and was spin-coated at 4000 rpm for 30 s, and after spin-coating, it was placed on a heating stage at 100°C for 5 min.

[0050] The prepared device is from bottom to top: ITO substrate, Sn02dense layer (i.e., electron transport layer), perovskite light absorption layer ((FAPbI3) 0.95 (MAPbBr3) 0.05 perovskite material), passivation layer (4,5-dihydroimidazole-2-hydrazine hydriodide).

[0051] Example 3

[0052] 1) ITO conductive glass was cut into 25 mm x 25 mm size, washed with conductive glass cleaning solution, deionized water and ethanol respectively, and dried in an oven, and treated with UV surface treatment to obtain an ITO substrate.

[0053] SnO2 dense layer preparation: 1 mL of SnO2 colloidal dispersion was diluted 7 times with deionized water to obtain a SnO2 solution. Further, the solution method operation method is: depositing the SnO2 precursor solution on the ITO substrate; the annealing temperature is 150°C, and the annealing time is 40 min.

[0054] 2) Perovskite light absorption layer preparation:

[0055] 2-1) 1.33 mol of formamidinium hydriodide, 0.07 mol of methylammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide were weighed and dissolved in 1 mL of a mixed solvent of dimethyl sulfoxide and dimethylformamide, the volume ratio of dimethyl sulfoxide and dimethylformamide being 1:4, to obtain a solution with a concentration of 1.4 mol / mL, which was stirred on a stirring table for 5 h for complete dissolution, and then filtered with a 45 μm filter head to obtain a perovskite precursor solution.

[0056] 2-2) 90 μL of the perovskite precursor solution was taken and dropped on the ITO substrate covered with the SnO2 dense layer preheated at 70°C, which was spin-coated at 1000 rpm for 10 s, and at 4500 rpm for 30 s in the second step, 150 μl of chlorobenzene was added 15-20 s before the end of the spin-coating, and the spin-coated product was placed on a heating table at 150°C for heating for 15 min.

[0057] 3) Passivation layer preparation

[0058] 3-1) 30 mmol of 4,5-dihydroimidazole-2-hydrazine hydriodide powder was dissolved in 1 mL of IPA to obtain a solution with a concentration of 30 mmol / mL, which was stirred on a stirring table at room temperature for 2 h for complete dissolution, and then filtered with a 45 μm filter head.

[0059] 3-2) 90 μL of the perovskite solution was taken and dropped on the cooled perovskite light absorption layer obtained from step 2), which was spin-coated at 4000 rpm for 30 s, and then placed on a heating table at 100°C for heating for 5 min. The prepared device, from bottom to top, was an ITO substrate, a SnO2 dense layer (i.e., an electron transport layer), a perovskite light absorption layer ((FAPbI3) 0.95 (MAPbBr3) 0.05 perovskite material), and a passivation layer (4,5-dihydroimidazole-2-hydrazine hydriodide).

[0060] Comparative Example 1

[0061] 1) ITO conductive glass was cut into 25mm x 25mm size, respectively washed with conductive glass cleaning solution, deionized water, ethanol, and put into the oven to dry, UV surface treatment was adopted, and ITO substrate was obtained.

[0062] SnO2 dense layer preparation: 1 mL SnO2 colloidal dispersion was diluted 7 times with deionized water to obtain SnO2 solution. Further, the solution method operation method is: SnO2 precursor solution is deposited on the ITO substrate; the annealing temperature is 150℃, and the annealing time is 40 min.

[0063] 2) Perovskite light absorption layer preparation:

[0064] 2-1) 1.33 mol of formamidinium hydriodide, 0.07 mol of methylammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide were weighed and dissolved in 1 mL of a mixed solvent of dimethyl sulfoxide and dimethylformamide, the volume ratio of dimethyl sulfoxide and dimethylformamide was 1:4, the concentration of the solution was 1.4 mol / mL, after stirring for 5 h to fully dissolve, the solution was filtered with a 45 μm filter head to obtain a perovskite precursor solution.

[0065] 2-2) 90 μL of the above perovskite precursor solution was dropped on the ITO substrate covered with the SnO2 dense layer preheated at 70℃, and was spin-coated at 1000 rpm for 10 s, and at 4500 rpm for 30 s in the second step, 150 μl of chlorobenzene was added 15-20 s before the end of spin-coating, and after spin-coating, it was placed on a heating stage at 150℃ for 15 min.

[0066] The prepared device is ITO substrate, SnO2 dense layer (i.e., electron transport layer), perovskite light absorption layer ((FAPbI3) 0.95 (MAPbBr3) 0.05 perovskite material) from bottom to top.

[0067] The solar cell structure of ITO / SnO2 / perovskite light absorption layer / passivation layer / gold electrode layer provided with a passivation layer prepared by the method of the application

[0068] Example 4

[0069] 1) ITO conductive glass was cut into 25mm x 25mm size, respectively washed with conductive glass cleaning solution, deionized water, ethanol, and put into the oven to dry, UV surface treatment was adopted, and ITO substrate was obtained;

[0070] SnO2 compact layer preparation: 1 mL SnO2 colloidal dispersion solution was diluted 7 times with deionized water to obtain a SnO2 solution. Further, the solution method operation method is: SnO2 precursor solution is deposited on an ITO substrate; the annealing temperature is 150°C, and the annealing time is 40 min.

[0071] 2) Perovskite light absorption layer preparation:

[0072] 2-1) 1.33 mol of formamidinium hydriodide, 0.07 mol of methylammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide were weighed and dissolved in 1 mL of a mixed solvent of dimethyl sulfoxide and dimethylformamide, the volume ratio of dimethyl sulfoxide and dimethylformamide being 1:4, to obtain a solution with a concentration of 1.4 mol / mL, which was stirred on a stirring table for 5 h for complete dissolution, and then filtered with a 45-μm filter head to obtain a perovskite precursor solution.

[0073] 2-2) 90 μL of the perovskite precursor solution was dropped on an ITO substrate covered with a SnO2 compact layer preheated at 70°C, and spin-coated at 1000 rpm for 10 s, 4500 rpm for 30 s in the second step, 150 μL of chlorobenzene was added 15-20 s before the end of spin-coating, and then placed on a 150°C heating table for heating for 15 min.

[0074] 3) Passivation layer preparation

[0075] 3-1) 10 mmol of 4,5-dihydroimidazole-2-hydrazine hydriodide powder was dissolved in 1 mL of IPA, and the obtained solution was 30 mmol / mL, which was stirred on a stirring table at room temperature for 2 h for complete dissolution, and then filtered with a 45-μm filter head.

[0076] 3-2) 90 μL of the perovskite solution was dropped on the cooled perovskite light absorption layer obtained from step 2), and spin-coated at 4000 rpm for 30 s, and then placed on a 100°C heating table for heating for 5 min.

[0077] 4) Hole transport layer preparation:

[0078] Spiro-OMeTAD hole transport layer preparation: The hole transport layer solution was configured two hours before use, wherein the solvent was chlorobenzene 1 mL, spiro-OMeTAD powder 72.3 mg, TBP 28.8 μL, LiTFSI 17.5 μL, and Co(III)TFSI 8 μL. After the above sample was cooled to room temperature, 50 μL of the hole transport layer solution was dropped on the above sample for spin-coating (3000 rpm, 30 s).

[0079] 5) Evaporation of gold electrode layer: A vacuum coating machine was used to evaporate a gold electrode layer on the perovskite light absorption layer at a pressure of 1 x 10 -5A 70 nm thick gold film was evaporated as an electrode on the Pa.

[0080] The prepared device from bottom to top is ITO substrate, Sn02dense layer (i.e., electron transport layer), perovskite light absorption layer ((FAPbI3) 0.95 (MAPbBr3) 0.05 perovskite material), passivation layer (4,5-dihydroimidazole-2-hydrazinium hydriodide), hole transport layer (spiro-OMeTAD), gold electrode layer.

[0081] Example 5

[0082] 1) ITO conductive glass was cut into 25 mm x 25 mm size, washed with conductive glass cleaning solution, deionized water and ethanol respectively, and dried in an oven, and treated with UV surface treatment to obtain an ITO substrate.

[0083] Sn02dense layer preparation: 1 mL of Sn02colloidal dispersion was diluted 7 times with deionized water to obtain a Sn02solution. Further, the solution method operation method is: depositing the Sn02precursor solution on the ITO substrate; the annealing temperature is 150°C, and the annealing time is 40 min.

[0084] 2) Perovskite light absorption layer preparation:

[0085] 2-1) 1.33 mol of formamidinium hydriodide, 0.07 mol of methylammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide were weighed and dissolved in 1 mL of a mixed solvent of dimethyl sulfoxide and dimethylformamide, the volume ratio of dimethyl sulfoxide and dimethylformamide was 1:4, the concentration of the obtained solution was 1.4 mol / mL, after stirring for 5 h to fully dissolve, the solution was filtered with a 45 μm filter head to obtain a perovskite precursor solution.

[0086] 2-2) 90 μL of the above perovskite precursor solution was dropped on the ITO substrate covered with the Sn02dense layer preheated at 70°C, and was spin-coated at 1000 rpm for 10 s, and at 4500 rpm for 30 s, 150 μl of chlorobenzene was added 15-20 s before the end of spin-coating, and after spin-coating, it was placed on a heating stage at 150°C for 15 min.

[0087] 3) Passivation layer preparation

[0088] 3-1) 20 mmol of 4,5-dihydroimidazole-2-hydrazinium hydriodide powder was dissolved in 1 mL of IPA, the obtained solution was 30 mmol / mL, and was stirred on a constant temperature stirring table for 2 h to fully dissolve, and then the solution was filtered with a 45 μm filter head.

[0089] 3-2) Take 90 μL perovskite solution and drop it on the cooled perovskite light absorption layer obtained from step 2), spin it at 4000 rpm for 30 s, and place it on a 100 °C heating stage for 5 min after spin coating.

[0090] 4) Hole transport layer preparation:

[0091] Spiro-OMeTAD hole transport layer preparation: The hole transport layer solution was configured two hours before use, in which the solvent was chlorobenzene 1 mL, spiro-OMeTAD powder 72.3 mg, TBP 28.8 μL, LiTFSI 17.5 μL, Co(III)TFSI 8 μL. After the above sample was cooled to room temperature, 50 μL of the hole transport layer solution was dropped on the above sample for spin coating (3000 rpm, 30 s).

[0092] 5) Evaporation of gold electrode layer: A 70 nm thick gold film was evaporated as an electrode using a vacuum coater at 1 x 10 -5 Pa.

[0093] The prepared device, from bottom to top, is ITO substrate, Sn02dense layer (i.e., electron transport layer), perovskite light absorption layer ((FAPbI3) 0.95 (MAPbBr3) 0.05 perovskite material), passivation layer (4,5-dihydroimidazole-2-hydrazine hydroiodide), hole transport layer (spiro-OMeTAD), gold electrode layer.

[0094] Example 6

[0095] 1) Cut the ITO conductive glass into 25 mm x 25 mm size, wash it with conductive glass cleaning solution, deionized water, and ethanol respectively, and dry it in an oven, and use UV surface treatment to obtain an ITO substrate.

[0096] Sn02dense layer preparation: Dilute 1 mL of Sn02colloidal dispersion with deionized water by 7 times to obtain a Sn02solution. Further, the solution method operation method is: deposit the Sn02precursor solution on the ITO substrate; the annealing temperature is 150 °C, and the annealing time is 40 min.

[0097] 2) Perovskite light absorption layer preparation:

[0098] 2-1) Take 1.33 mol of formamidinium hydriodide, 0.07 mol of methyl ammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide, and dissolve them in 1 mL of a mixed solvent of dimethyl sulfoxide and dimethylformamide at a volume ratio of 1:4 to obtain a solution having a concentration of 1.4 mol / mL. After stirring on a stirring table for 5 h to completely dissolve, the solution is filtered using a filter head of 45 pm to obtain a perovskite precursor solution.

[0099] 2-2) Take 90 pL of the perovskite precursor solution described above and drop it on an ITO substrate covered with a dense SnO2 layer preheated at 70°C. Spin it at 1000 rpm for 10 s, and then spin it at 4500 rpm for 30 s. Add 150 pL of chlorobenzene dropwise 15-20 s before the end of the spinning, and then place it on a heating table at 150°C for 15 min after spinning.

[0100] 3) Preparation of a passivation layer

[0101] 3-1) Dissolve 30 mmol of 4,5-dihydroimidazole-2-hydrazine hydriodide powder in 1 mL of IPA to obtain a solution having a concentration of 30 mmol / mL. After stirring on a stirring table at room temperature for 2 h to completely dissolve, the solution is filtered using a filter head of 45 pm.

[0102] 3-2) Take 90 pL of the perovskite solution and drop it on the perovskite light-absorbing layer obtained in step 2) that has been cooled. Spin it at 4000 rpm for 30 s, and then place it on a heating table at 100°C for 5 min after spinning.

[0103] 4) Preparation of a hole transport layer:

[0104] Preparation of a hole transport layer of spiro-OMeTAD: A hole transport layer solution is prepared two hours before use, in which 1 mL of chlorobenzene is used as a solvent, 72.3 mg of spiro-OMeTAD powder, 28.8 pL of TBP, 17.5 pL of LiTFSI, and 8 pL of Co(III)TFSI are used. After the above sample is cooled to room temperature, 50 pL of the hole transport layer solution is dropped on the sample and spin-coated (3000 rpm, 30 s).

[0105] 5) Evaporation of a gold electrode layer: A 70-nm-thick gold film is evaporated as an electrode using a vacuum evaporation coater at 1 x 10 -5 Pa.

[0106] The prepared device is from bottom to top: an ITO substrate, a dense SnO2 layer (i.e., an electron transport layer), a perovskite light-absorbing layer ((FAPbI3) 0.95 (MAPbBr3) 0.05Perovskite material), passivation layer (4,5-dihydroimidazole-2-hydrazinium hydriodide), hole transport layer (spiro-OMeTAD), gold electrode layer.

[0107] The solar cell structure of ITO / SnO2 / perovskite light absorption layer / gold electrode layer without passivation layer prepared by the method of the present application

[0108] Comparative Example 2

[0109] 1) ITO conductive glass was cut into 25mm x 25mm size, and was cleaned with conductive glass cleaning solution, deionized water and ethanol respectively, and was dried in an oven, and was subjected to UV surface treatment to obtain an ITO substrate.

[0110] SnO2 dense layer preparation: 1 mL of SnO2 colloidal dispersion solution was diluted 7 times with deionized water to obtain a SnO2 solution. Further, the solution method operation method is: the SnO2 precursor solution is deposited on the ITO substrate; the annealing temperature is 150°C, and the annealing time is 40 min.

[0111] 2) Perovskite light absorption layer preparation:

[0112] 2-1) 1.33 mol of formamidinium hydriodide, 0.07 mol of methylammonium bromide, 1.4 mol of lead iodide, and 0.07 mol of lead bromide were weighed and dissolved in 1 mL of a mixed solvent of dimethyl sulfoxide and dimethylformamide, the volume ratio of dimethyl sulfoxide and dimethylformamide was 1:4, the concentration of the solution was 1.4 mol / mL, after stirring for 5 h to fully dissolve, the solution was filtered with a 45 μm filter head to obtain a perovskite precursor solution.

[0113] 2-2) 90 μL of the above perovskite precursor solution was dropped on the ITO substrate covered with the SnO2 dense layer preheated at 70°C, and was spin-coated at 1000 rpm for 10 s, and at 4500 rpm for 30 s in the second step, 150 μl of chlorobenzene was added 15-20 s before the end of spin-coating, and after spin-coating, it was placed on a heating stage at 150°C for 15 min.

[0114] 3) Hole transport layer preparation:

[0115] Preparation of the spiro-OMeTAD hole transport layer: the hole transport layer solution was prepared two hours before use, wherein the solvent was chlorobenzene 1 mL, spiro-OMeTAD powder 72.3 mg, TBP 28.8 μL, LiTFSI 17.5 μL, and Co(III)TFSI 8 μL. After the above sample was cooled to room temperature, 50 μL of the hole transport layer solution was dropped on the above sample for spin-coating (3000 rpm, 30 s);

[0116] 4) Gold electrode layer: 70 nm thick gold film was evaporated as electrode at 1x10 -5 Pa.

[0117] The prepared device from bottom to top is ITO substrate, SnO2 dense layer (i.e., electron transport layer), perovskite light absorption layer ((FAPbI3) 0.95 (MAPbBr3) 0.05 perovskite material), hole transport layer (spiro-OMeTAD), gold electrode layer.

[0118] The products obtained from Examples 1-3 and Comparative Example 1 were compared to explore the effect of the passivation layer

[0119] The perovskite thin film with 4,5-dihydroimidazole-2-hydrazinium hydriodide as passivation layer of Example 2 and the standard sample perovskite thin film prepared without setting the passivation layer of Comparative Example 1 were subjected to X-ray diffraction test, and the results are shown in Figure 2 From the X-ray diffraction patterns of the standard sample and the sample after passivation, it can be clearly seen that the passivation treatment of 4,5-dihydroimidazole-2-hydrazinium hydriodide does not change the bulk perovskite structure. The standard sample has a PbI2 characteristic peak near 12.7°, however, after passivation treatment, 4,5-dihydroimidazole-2-hydrazinium hydriodide reacts with the remaining PbI2 in the perovskite, resulting in a significant decrease in the intensity of the PbI2 characteristic peak, and a new diffraction peak appears near 4.9°, representing the formation of a new low-dimensional phase on the surface of the bulk perovskite, which is consistent with the low-dimensional perovskite phase formed when the molar ratio of 4,5-dihydroimidazole-2-hydrazinium hydriodide and lead iodide is 2:1.

[0120] Figure 3 The surface scanning electron microscope images of the perovskite thin film with (right side image) and without (left side image) 4,5-dihydroimidazole-2-hydrazinium hydriodide as passivation layer treatment are shown, from which it can be clearly seen that the thin film without passivation layer shows a dense surface, but the grain boundaries are clearly visible, while the thin film with 4,5-dihydroimidazole-2-hydrazinium hydriodide as passivation layer shows a smoother, denser and more uniform surface, with fewer grain boundaries, which is conducive to effective charge transport and excellent photovoltaic performance.

[0121] Figure 4 The ultraviolet-visible absorption spectra of the perovskite thin film with different concentrations of 4,5-dihydroimidazole-2-hydrazinium hydriodide as passivation layer treatment and the standard sample are shown, and the light absorption capacity of the passivated thin film is slightly enhanced, which is related to the increase in short-circuit current density of the perovskite device with different concentrations of 4,5-dihydroimidazole-2-hydrazinium hydriodide as passivation layer and the standard sample in Table 1.

[0122] The products prepared in Comparative Example 2 and Examples 4-6 are compared:

[0123] Figure 5 Table 1 is the J-V curve and corresponding photovoltaic parameters of perovskite solar cells with different concentrations of 4,5-dihydroimidazole-2-hydrazine hydroiodide as a passivation layer treatment and standard samples under standard AM1.5G (100 mW·cm -2 ) illumination. By optimizing the concentration of the passivation layer used in the preparation process of the perovskite film, the enhanced photoelectric conversion efficiency is obtained.

[0124] (FAPbI3) 0.95 (MAPbBr3) 0.05 The current density (J sc ) of the perovskite solar cell with a thin film and passivation layer treatment is increased from 24.54 mA·cm -2 to 25.08 mA·cm -2 , the open circuit voltage (V oc ) is increased from 1.08 V to 1.16 V, the photoelectric conversion efficiency is increased from 20.46% to 23.09%, the fill factor (FF) is increased to 78.95%, and the photoelectric performance is obviously improved. In summary, the treatment of this passivation layer makes the (FAPbI3) 0.95 (MAPbBr3) 0.05 thin film play a great degree of matching and additive effect in the field of solar cells.

[0125] Table 1 Influence of passivation layer on performance of solar cells

[0126]

[0127] From the above examples, by depositing a halogen salt containing heterocyclic ammonium salt cation (4,5-dihydroimidazole-2-hydrazine hydrogen) at the interface between the perovskite light absorption layer and the hole transport layer, the surface defects of the perovskite light absorption layer are passivated, non-radiative recombination is inhibited, and the interface charge extraction is improved, thereby realizing the improvement of device efficiency and stability.

[0128] The above description is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A perovskite solar cell, comprising an ITO substrate, a SnO 2 electron transport layer, a perovskite light absorption layer, a passivation layer, a hole transport layer and a gold electrode layer arranged in sequence. The passivation layer is a halogen salt of 4,5-dihydroimidazole-2-hydrazine.

2. The perovskite solar cell according to claim 1, characterized in that, The passivation layer is one or more of 4,5-dihydroimidazole-2-hydrazine hydriodate, 4,5-dihydroimidazole-2-hydrazine hydrobromide and 4,5-dihydroimidazole-2-hydrazine hydrochloride. 3.The perovskite solar cell of claim 1, wherein, The material of the perovskite light absorption layer is (FAPbI3) 0.95 (MAPbBr3) 0.05 . 4.The perovskite solar cell of claim 1, wherein, The thickness of the SnO 2 electron transport layer is 20-30 nm. The thickness of the perovskite light absorption layer is not less than 100 nm. The thickness of the passivation layer is 5-20 nm. The thickness of the hole transport layer is 150-220 nm. The thickness of the gold electrode layer is 65-85 nm. 5.A method for preparing the perovskite solar cell of any one of claims 1-4, comprising the following steps: depositing a SnO 2 precursor solution on the ITO substrate, annealing to obtain a SnO 2 electron transport layer; spin-coating a perovskite precursor solution on the SnO 2 electron transport layer and heating to obtain a perovskite light absorption layer; spin-coating a passivation layer solution on the perovskite light absorption layer and heating to obtain a passivation layer, the passivation layer being a halogen salt of 4,5-dihydroimidazole-2-hydrazine; spin-coating a hole transport layer solution on the passivation layer to obtain a hole transport layer; preparing a metal electrode layer on the hole transport layer by vacuum evaporation to obtain a perovskite solar cell.

6. The preparation method according to claim 5, characterized in that, The amount of the passivation layer solution is 15-25 μL / cm 2 ; The spin-coating speed of the passivation layer solution is 3000-5000 rpm. The heating temperature of the passivation layer solution is 90-120 ℃, and the heating time of the passivation layer solution is 5-10 min.

7. The preparation method according to claim 5, characterized in that, The amount of the perovskite precursor solution is 15-25 μL / cm 2 The rotation speed of the spin coating is 3000-5000 rpm. The heating temperature of the perovskite precursor solution is 120-150 ℃, and the heating time of the perovskite precursor solution is 10-15 min.

8. The preparation method according to claim 5, characterized in that, The concentration of the halogen salt of 4,5-dihydroimidazole-2-hydrazine in the passivation layer solution is 10-50 mmol / mL, and the solvent in the passivation layer solution is isopropanol. The concentration of the perovskite precursor solution is 1.4-1.8 mol / mL, and the perovskite precursor solution is an organic mixed solvent of dimethyl sulfoxide and dimethylformamide, and the volume of dimethylformamide in the organic mixed solvent per unit volume is 4-9 times the volume of dimethyl sulfoxide.

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