A method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive

Abstract

A method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive. The perovskite solar cell comprises a FTO glass substrate, a dense TiO2 layer, a mesoporous TiO2 layer, a CsPbIBr2 perovskite film, and a carbon electrode. The CsPbIBr2 perovskite film is prepared as follows: PbBr2 and CsI are dissolved in dimethyl sulfoxide, and then phenylthiourea is added to dissolve the mixture to obtain a precursor solution. A dense TiO2 layer and a mesoporous TiO2 layer are prepared on the surface of the FTO glass substrate. The precursor solution is then preheated and spin-coated onto the surface of the mesoporous TiO2 layer using a spin coating method. The precursor solution is then heat-treated at 150°C to 300°C to form the CsPbIBr2 perovskite film. The method is simple and easy to operate. By improving the quality and stability of the CsPbIBr2 perovskite film, a stable, high-efficiency CsPbIBr2 perovskite solar cell can be prepared.

Description

Technical Field

[0001] The present invention relates to a method for improving the photoelectric performance and stability of a perovskite solar cell by utilizing a phenylthiourea bifunctional additive, and in particular to a method for improving the photoelectric performance and stability of an inorganic CsPbIBr2 perovskite solar cell by utilizing a phenylthiourea bifunctional additive. Background Art

[0002] Inorganic CsPbIBr2 perovskite is considered to be a promising solar cell light-absorbing material due to its high stability and suitable band gap of 2.03eV. It can be widely used in stacked and semi-transparent solar cells. In 2016, the photoelectric conversion efficiency of CsPbIBr2 perovskite solar cells prepared by dual-source thermal evaporation was 4.7%. In the same year, the efficiency of CsPbIBr2 perovskite solar cells prepared by spray solution deposition reached 6.3%. In 2018, Zhu et al. prepared a dense CsPbIBr2 perovskite film by molecular exchange method, and the photoelectric conversion efficiency of the assembled carbon-based CsPbIBr2 perovskite solar cell reached 9.16%. In 2021, Tang et al. introduced (NiCo) into carbon-based CsPbIBr2 perovskite solar cells 1-y Fe y O x / graphite oxide hybrid system to improve the hole separation and transport efficiency, so that the efficiency of carbon-based CsPbIBr2 perovskite solar cells is increased to 10.95%.

[0003] Although significant progress has been made in the research of CsPbIBr2 perovskite solar cells, their efficiency is still significantly low, far from the theoretical value. A key reason for the low photoelectric conversion efficiency of CsPbIBr2 perovskite solar cells is the poor quality of the prepared CsPbIBr2 perovskite film and the presence of a large number of defects, which cause severe charge recombination within the CsPbIBr2 perovskite solar cell. Furthermore, the CsPbIBr2 perovskite film is susceptible to phase transitions due to water vapor, which also reduces the performance of the CsPbIBr2 perovskite solar cell. Therefore, improving the quality and stability of the CsPbIBr2 perovskite film is key to further improving the photoelectric performance and stability of CsPbIBr2 perovskite solar cells. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for improving the photoelectric performance and stability of perovskite solar cells by using a bifunctional phenylthiourea additive. The method is simple and easy to operate. By improving the quality and stability of the CsPbIBr2 perovskite film, a stable and high-efficiency CsPbIBr2 perovskite solar cell is prepared.

[0005] The technical solution of the present invention is:

[0006] A method for improving the photoelectric performance and stability of a perovskite solar cell using a phenylthiourea bifunctional additive. The perovskite solar cell comprises an FTO glass substrate on which a dense TiO2 layer, a TiO2 mesoporous layer, a CsPbIBr2 perovskite film layer, and a carbon electrode are sequentially provided. The method is special in that the CsPbIBr2 perovskite film layer is prepared as follows:

[0007] (1) Preparation of CsPbIBr2 perovskite precursor solution

[0008] PbBr2 and CsI are dissolved in dimethyl sulfoxide (DMSO) at 70°C with stirring to form a PbBr2 and CsI mixed solution with a concentration of 0.7 mol / L to 1.2 mol / L; phenylthiourea (PTU) is then added to the PbBr2 and CsI mixed solution in an amount of 1% to 5% of the total mass of PbBr2 and CsI, and the mixture is stirred and dissolved to obtain a CsPbIBr2 perovskite precursor solution;

[0009] (2) Preparation of CsPbIBr2 perovskite film

[0010] A TiO2 dense layer and a TiO2 mesoporous layer are sequentially prepared on the surface of an FTO glass sheet to obtain an FTO glass sheet with a titanium dioxide layer; the FTO glass sheet with the titanium dioxide layer is preheated to 50°C, and a CsPbIBr2 perovskite precursor solution is spin-coated onto the surface of the TiO2 mesoporous layer by a spin-coating method at a spin-coating speed of 2500 rpm for 30 seconds, and then heat-treated at 150°C to 300°C for 5 to 20 minutes to form a CsPbIBr2 perovskite film layer.

[0011] Furthermore, the molar ratio of PbBr2 to CsI is 1:1.

[0012] Furthermore, the added amount of the phenylthiourea accounts for 2% to 3% of the total mass of PbBr2 and CsI.

[0013] Furthermore, the added amount of the phenylthiourea accounts for 2.5% of the total mass of PbBr2 and CsI.

[0014] Furthermore, the concentration of the mixed solution of PbBr2 and CsI is 0.85 mol / L to 1.1 mol / L.

[0015] Furthermore, the concentration of the mixed solution of PbBr2 and CsI is 1 mol / L.

[0016] Furthermore, when preparing the TiO2 dense layer, a 0.15 mol / L bis(acetylacetonate) diisopropyl titanate ethanol solution was spin-coated onto the cleaned FTO glass surface at a spin-coating speed of 4500 rpm for 45 s, and then heat-treated at 450°C for 30 minutes to form a TiO2 dense layer on the FTO glass surface.

[0017] Furthermore, when preparing the TiO2 mesoporous layer, the ethanol-diluted TiO2 colloid was spin-coated onto the surface of the TiO2 dense layer. The weight ratio of ethanol to colloid in the ethanol-diluted TiO2 colloid was 15:1. The spin-coating speed was 4000 rpm and the spin-coating time was 30 s. Then, the TiO2 mesoporous layer was formed on the surface of the TiO2 dense layer by heat treatment at 450°C for 30 minutes.

[0018] Beneficial effects of the present invention:

[0019] The present invention uses phenylthiourea (PTU) as a bifunctional additive added to the CsPbIBr2 perovskite precursor solution. On the one hand, the C=S group in phenylthiourea (PTU) reacts with the Pb in the precursor solution. 2+ A strong interaction can be formed between Figure 1 ), and the electron-donating properties of the benzene ring in phenylthiourea (PTU) can increase the electron cloud density of the C=S group ( Figure 2 ), thereby increasing the C=S group and Pb in the precursor solution 2+ The interaction between them. Therefore, a metastable PTU-PbBr2 intermediate phase complex is formed in the CsPbIBr2 precursor, which reduces the crystallization rate of CsPbIBr2 perovskite. The crystallization of pure CsPbIBr2 is completed in 10 minutes, while the crystallization time is significantly increased after the addition of phenylthiourea (PTU). The reduced crystallization rate is conducive to the full growth of crystals; thus, a high-quality, dense CsPbIBr2 perovskite film with few defects, high crystallinity and large particle size is formed. On the other hand, during the heat treatment of the CsPbIBr2 perovskite film, phenylthiourea (PTU) decomposes ( Figure 4), resulting in the incorporation of sulfur into the CsPbIBr2 perovskite crystal. The incorporation of sulfur greatly enhances the stability of the CsPbIBr2 perovskite. Therefore, the bifunctional additive phenylthiourea (PTU) can regulate the crystallization of CsPbIBr2 perovskite films and prepare sulfur-doped CsPbIBr2 perovskite films, thereby improving the quality and stability of CsPbIBr2 perovskite films and preparing stable, high-efficiency CsPbIBr2 perovskite solar cells. The prepared CsPbIBr2 perovskite film was used to assemble a carbon-based CsPbIBr2 perovskite solar cell with a structure of FTO / TiO2 / perovskite film / carbon layer. Without any optimization, the cell achieved an efficiency of 10.09%, which is 77% higher than that of the CsPbIBr2 perovskite cell without the addition of phenylthiourea (PTU). Moreover, the prepared perovskite solar cell showed excellent stability in air environment and high humidity (relative humidity 85%). BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FTIR spectra of CsPbIBr2 precursor, PTU, and PTU-CsPbIBr2 precursor;

[0021] Figure 2 HOMO electron distribution diagram of PTU;

[0022] Figure 3 Photos of the precursor films of Comparative Example 1 CsPbIBr2 and Example 2 PTU-CsPbIBr2 at different time points during the crystallization process of heat treatment at 200°C;

[0023] Figure 4 Thermal decomposition curve of PTU;

[0024] Figure 5 SEM photo of the CsPbIBr2 perovskite film prepared in Comparative Example 1 of the present invention;

[0025] Figure 6 1 is an XRD pattern of the CsPbIBr2 perovskite films prepared in Comparative Example 1 (0 wt% PTU), Example 1 (1 wt% PTU), Example 2 (2.5 wt% PTU), and Example 3 (5 wt% PTU) of the present invention;

[0026] Figure 7 is a SEM photograph of the CsPbIBr2 perovskite film prepared in Example 1 of the present invention;

[0027] Figure 8 is a SEM photograph of the CsPbIBr2 perovskite film prepared in Example 2 of the present invention;

[0028] Figure 9 is a SEM photograph of the CsPbIBr2 perovskite film prepared in Example 3 of the present invention;

[0029] Figure 10 Graph showing the change in photoelectric conversion efficiency over time of the carbon-based CsPbIBr2 perovskite solar cells prepared in Example 2 of the present invention and Comparative Example 1 in an air environment (30° C., relative humidity 35%);

[0030] Figure 11 Graph showing the change in photoelectric conversion efficiency over time of the carbon-based CsPbIBr2 perovskite solar cells prepared in Example 2 of the present invention and Comparative Example 1 in a high humidity environment (humidity of 85%);

[0031] Figure 12 is the EDS spectrum of the CsPbIBr2 perovskite film prepared in Example 2 of the present invention;

[0032] Figure 13 is a cross-sectional SEM photograph of the CsPbIBr2 perovskite film prepared in Example 2 of the present invention;

[0033] Figure 14 is a SEM photograph of the CsPbIBr2 perovskite film prepared in Example 8 of the present invention;

[0034] Figure 15 is a SEM photograph of the CsPbIBr2 perovskite film prepared in Example 9 of the present invention;

[0035] Figure 16 This is a SEM photograph of the CsPbIBr2 perovskite film prepared in Example 10 of the present invention. DETAILED DESCRIPTION

[0036] Example 1

[0037] (1) Preparation of FTO / TiO2 substrate

[0038] A 0.15 mol / L bis(acetylacetonato) diisopropyl titanate ethanol solution was spin-coated onto the cleaned FTO glass surface at a spin-coating speed of 4500 rpm for 45 seconds, followed by heat treatment at 450°C for 30 minutes to form a TiO2 dense layer on the FTO glass surface; an ethanol-diluted TiO2 colloid was spin-coated onto the TiO2 dense layer, wherein the ethanol-to-colloid weight ratio in the ethanol-diluted TiO2 colloid was 15:1, at a spin-coating speed of 4000 rpm for 30 seconds, followed by heat treatment at 450°C for 30 minutes to form a TiO2 mesoporous layer, thereby obtaining an FTO / TiO2 substrate;

[0039] (2) Preparation of CsPbIBr2 perovskite film

[0040] 0.367 g of PbBr2 and 0.259 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70 °C by stirring, and then phenylthiourea (PTU) (6.26 mg) accounting for 1 wt% of the total amount of PbBr2 and CsI was added and dissolved to obtain a CsPbIBr2 perovskite precursor solution;

[0041] The FTO / TiO2 substrate of step (1) was preheated to 50°C, and the CsPbIBr2 perovskite precursor solution was spin-coated onto the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate by spin coating at a speed of 2500 rpm for 30 seconds, and then heat treated at 200°C for 15 minutes to form a CsPbIBr2 perovskite film. The XRD pattern of the CsPbIBr2 perovskite film is shown in FIG. Figure 6 Its SEM photos are shown as follows: Figure 7 As shown, the CsPbIBr2 perovskite film is smooth and has no small holes, but the crystal grains are small and have many boundaries;

[0042] (3) Preparation of carbon-based inorganic CsPbIBr2 perovskite solar cells using FTO / TiO2 / CsPbIBr2 / carbon electrodes

[0043] A carbon layer was applied to the surface of the CsPbIBr2 perovskite film to prepare a carbon-based CsPbIBr2 perovskite solar cell with a structure of FTO / TiO2 / CsPbIBr2 / carbon electrode; the photoelectric performance of the cell was 100mW / cm 2 Under simulated sunlight (AM1.5), the cell efficiency was measured using a Keithley 2400 digital source meter and was found to be 7.41%.

[0044] Example 2

[0045] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0046] (2) Preparation of CsPbIBr2 perovskite film

[0047] 0.367 g of PbBr2 and 0.259 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70 °C by stirring, and then phenylthiourea (PTU) (15.65 mg) accounting for 2.5 wt% of the total amount of PbBr2 and CsI was added and dissolved to obtain a CsPbIBr2 perovskite precursor solution;

[0048] The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50°C, and the CsPbIBr2 perovskite precursor solution was spin-coated onto the substrate surface at a spin coating speed of 2500 rpm for 30 seconds, followed by heat treatment at 200°C for 15 minutes to form a CsPbIBr2 perovskite film. The XRD pattern of the CsPbIBr2 perovskite film is shown in FIG. Figure 6 Its SEM photos are shown as follows: Figure 8 As shown by Figure 8 It can be seen that the CsPbIBr2 perovskite film is flat, dense, without small holes, with large crystal particle size, uniform distribution and few boundaries; the cross-sectional SEM photo of the CsPbIBr2 perovskite film is shown in Figure 2. Figure 13 As shown, the thickness of the CsPbIBr2 perovskite film is about 400nm; Figure 12 This is the EDS scan of the prepared CsPbIBr2 perovskite film. It can be seen from the figure that sulfur is doped into the perovskite and is evenly distributed.

[0049] (3) Preparation of carbon-based inorganic CsPbIBr2 perovskite solar cells with FTO / TiO2 / CsPbIBr2 / carbon electrode. A carbon layer was applied to the surface of the CsPbIBr2 perovskite film to prepare a carbon-based CsPbIBr2 perovskite solar cell with the structure of FTO / TiO2 / CsPbIBr2 / carbon electrode. The photoelectric performance of the cell was 100 mW / cm 2 Under simulated sunlight (AM1.5), the cell efficiency was measured using a Keithley 2400 digital source meter and was found to be 10.09%.

[0050] Example 3

[0051] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0052] (2) Preparation of CsPbIBr2 perovskite film

[0053] 0.367 g of PbBr2 and 0.259 g of CsI were dissolved in 1 ml of dimethyl sulfoxide (DMSO) at 70° C. by stirring, and then phenylthiourea (PTU) (31.4 mg) accounting for 5 wt% of the total amount of PbBr2 and CsI was added to dissolve to obtain a CsPbIBr2 perovskite precursor solution; the FTO / TiO2 substrate prepared according to Example 1 was preheated to 50° C., and the above-mentioned CsPbIBr2 perovskite precursor solution was applied to the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate by spin coating at a spin coating speed of 2500 rpm for 30 s, and then heat treated at 200° C. for 15 minutes to form a CsPbIBr2 perovskite film layer; the XRD pattern of the CsPbIBr2 perovskite film is shown in FIG. Figure 6 Its SEM photos are shown as follows: Figure 9 As shown by Figure 9 It can be seen that the CsPbIBr2 perovskite film is dense and has no pinholes, but the surface is rough and the boundaries increase;

[0054] (3) Preparation of carbon-based inorganic CsPbIBr2 perovskite solar cells using FTO / TiO2 / CsPbIBr2 / carbon electrodes

[0055] A carbon layer was applied to the surface of the CsPbIBr2 perovskite film to prepare a carbon-based CsPbIBr2 perovskite solar cell with a structure of FTO / TiO2 / CsPbIBr2 / carbon electrode; the photoelectric performance of the cell was 100mW / cm 2 Under simulated sunlight (AM1.5), the cell efficiency was measured using a Keithley 2400 digital source meter and was found to be 6.80%.

[0056] Comparative Example 1

[0057] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0058] (2) Preparation of CsPbIBr2 perovskite film

[0059] 0.367 g PbBr2 and 0.259 g CsI were dissolved in 1 mL dimethyl sulfoxide (DMSO) at 70 °C with stirring to form a 1 mol / L CsPbIBr2 perovskite precursor solution;

[0060] The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50°C, and the above-mentioned pure CsPbIBr2 perovskite precursor solution was applied to the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate by spin coating at a speed of 2500 rpm for 30 seconds, and then heat treated at 200°C for 15 minutes to form a CsPbIBr2 perovskite film. The XRD pattern of the CsPbIBr2 perovskite film is shown in FIG. Figure 6 Its SEM photos are shown as follows: Figure 5 As shown, the CsPbIBr2 perovskite film has small grain size, many grain boundaries, and many small pores; (3) Preparation of carbon-based inorganic CsPbIBr2 perovskite solar cells with FTO / TiO2 / CsPbIBr2 / carbon electrode. A carbon layer is applied to the surface of the CsPbIBr2 perovskite film to prepare a carbon-based inorganic CsPbIBr2 perovskite solar cell with the structure of FTO / TiO2 / CsPbIBr2 / carbon electrode; the photoelectric performance of the cell is 100mW / cm 2 Under simulated sunlight (AM1.5), the cell efficiency was measured using a Keithley 2400 digital source meter and was found to be 5.70%.

[0061] Comparative Example 1 and Examples 1-3 are parallel experimental examples of preparing CsPbIBr2 perovskite films without adding phenylthiourea (PTU), adding 1%, 2.5% and 5% phenylthiourea (PTU). Figure 6 It can be seen that the CsPbIBr2 perovskite film prepared in Comparative Example 1 of the present invention has a low degree of crystallinity; after 1% phenylthiourea (PTU) is added in Example 1, the crystallinity of the prepared CsPbIBr2 perovskite film is improved compared with Comparative Example 1; after 2.5% phenylthiourea (PTU) is added in Example 2, the CsPbIBr2 perovskite film prepared has the highest crystallinity compared with Example 1, Example 3 and Comparative Example 1; after 5% phenylthiourea (PTU) is added in Example 3, the crystallinity of the prepared CsPbIBr2 perovskite film decreases compared with Examples 1 and 2.

[0062] Comparative Example 1 and Examples 1-3 respectively assembled solar cells using CsPbIBr2 perovskite films prepared without adding phenylthiourea (PTU), with adding 1%, 2.5% and 5% phenylthiourea (PTU). The cell efficiency in Comparative Example 1 was relatively low, only 5.70%. After adding 1% phenylthiourea (PTU) in Example 1, the efficiency of the prepared cell increased to 7.41%. After adding 2.5% phenylthiourea (PTU) in Example 2, the cell efficiency was the highest, reaching 10.09%. After adding 5% PTU in Example 3, the cell efficiency was 6.80%, which was lower than that of Examples 1 and 2.

[0063] 1. Performance stability of perovskite solar cells in air environment and high humidity (relative humidity 85%) The carbon-based CsPbIBr2 perovskite solar cells prepared in Comparative Example 1 and Example 2 were placed in an air environment (30°C, relative humidity 35%), and their photoelectric conversion efficiency changed over time as shown in the figure. Figure 10 The efficiency of the battery prepared in Example 2 remained above 80% after 800 hours, while the efficiency of the battery prepared in Comparative Example 1 only remained at 52%.

[0064] The carbon-based CsPbIBr2 perovskite solar cells prepared in Comparative Example 1 and Example 2 were placed in an environment with a humidity of 85%, and the changes in their photoelectric conversion efficiency over time were as follows: Figure 11 The efficiency of the battery prepared in Comparative Example 1 dropped rapidly. The efficiency of the battery prepared in Example 2 remained above 95% after 120 minutes. This indicates that the carbon-based CsPbIBr2 perovskite solar cell prepared in Example 2 of the present invention has good performance stability in air environment and high humidity (relative humidity 85%) conditions.

[0065] 2. Comparative Example 1 CsPbIBr2 and Example 2 PTU-CsPbIBr2 precursor films were heat-treated at 200°C at different time points during crystallization. The CsPbIBr2 precursor films prepared in Comparative Example 1 and Example 2 were photographed with a camera. Figure 3 The crystallization speed of CsPbIBr2 was analyzed based on the rate of change of the precursor film color. Figure 3 It can be seen that the newly prepared comparative example 1 CsPbIBr2 precursor film has produced light brown areas, indicating that crystallization has begun before heating. The CsPbIBr2 precursor film of Example 2 is completely white, indicating that no crystallization occurs. The CsPbIBr2 film of Comparative Example 1 all turns light brown after 5 minutes of heat treatment, indicating a high degree of crystallization. After 10 minutes of heat treatment, the CsPbIBr2 film of Comparative Example 1 turns into a uniform dark red, indicating that CsPbIBr2 is completely crystallized into a perovskite structure. However, a small amount of light brown areas only appear in the CsPbIBr2 film of Example 2 after 5 minutes of heat treatment, indicating that crystallization has begun. The CsPbIBr2 film of Example 2 only turns into a uniform dark red after 15 minutes of heat treatment, indicating that it has completely transformed into a perovskite structure. This shows that the addition of PTU significantly reduces the crystallization rate of CsPbIBr2.

[0066] In Example 2, a PTU-PbBr2 intermediate phase complex is formed in the CsPbIBr2 precursor, which reduces the crystallization rate of the CsPbIBr2 perovskite ( Figure 3 ), the crystallization of pure CsPbIBr2 was completed in 10 minutes, while the addition of phenylthiourea (PTU) significantly increased the crystallization time.

[0067] Example 4

[0068] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0069] (2) Preparation of CsPbIBr2 perovskite film

[0070] 0.257 g of PbBr2 and 0.181 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70°C with stirring to form a 0.7 mol / L solution; phenylthiourea (PTU) (10.95 mg) was then added at 2.5 wt% of the total amount of PbBr2 and CsI and stirred to dissolve to form a CsPbIBr2 perovskite precursor solution;

[0071] The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50°C. The CsPbIBr2 perovskite precursor solution was spin-coated onto the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate at a speed of 2500 rpm for 30 seconds. The substrate was then heat-treated at 200°C for 15 minutes to form a CsPbIBr2 perovskite film. The CsPbIBr2 perovskite film had many small pores and low coverage.

[0072] Example 5

[0073] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0074] (2) Preparation of CsPbIBr2 perovskite film

[0075] 0.440 g of PbBr2 and 0.311 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70°C with stirring to form a 1.2 mol / L solution; phenylthiourea (PTU) (18.775 mg) was then added at 2.5 wt% of the total amount of PbBr2 and CsI and stirred to dissolve to form a CsPbIBr2 perovskite precursor solution;

[0076] The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50°C. The CsPbIBr2 perovskite precursor solution was spin-coated onto the TiO2 mesoporous layer of the FTO / TiO2 substrate at a speed of 2500 rpm for 30 seconds. The film was then heat-treated at 200°C for 15 minutes to form a CsPbIBr2 perovskite film. The resulting CsPbIBr2 perovskite film exhibited no pinholes but exhibited increased roughness, a wide particle size distribution, and numerous particle boundaries.

[0077] Examples 2, 4, and 5 are parallel experimental examples of preparing CsPbIBr2 perovskite films under different precursor solution concentration conditions. Compared with Example 2, the precursor solution concentration of Example 4 is lower, and the prepared CsPbIBr2 perovskite film has many small holes and poor coverage. The precursor solution concentration of Example 5 is higher, and the prepared CsPbIBr2 perovskite film has coarse particles and many boundaries. The precursor concentration in Example 2 is appropriate, and the prepared CsPbIBr2 perovskite film has the best quality.

[0078] Example 6

[0079] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0080] (2) Preparation of CsPbIBr2 perovskite film

[0081] 0.367 g of PbBr2 and 0.259 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70 °C by stirring, and then phenylthiourea (PTU) (15.65 mg) accounting for 2.5 wt% of the total amount of PbBr2 and CsI was added and dissolved;

[0082] The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50°C. The CsPbIBr2 perovskite precursor solution was spin-coated onto the TiO2 mesoporous layer of the FTO / TiO2 substrate at a speed of 2500 rpm for 30 seconds. The film was then heat-treated at 150°C for 5 minutes to form a CsPbIBr2 perovskite film. The film was smooth and dense, but had small crystal grains and numerous boundaries.

[0083] Example 7

[0084] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0085] (2) Preparation of CsPbIBr2 perovskite film

[0086] 0.367 g of PbBr2 and 0.259 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70 °C by stirring, and then phenylthiourea (PTU) (15.65 mg) accounting for 2.5 wt% of the total amount of PbBr2 and CsI was added and dissolved;

[0087] The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50°C. The CsPbIBr2 perovskite precursor solution was spin-coated onto the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate at a speed of 2500 rpm for 30 seconds. The film was then heat-treated at 300°C for 20 minutes to form a CsPbIBr2 perovskite film. The film had numerous small pores, a rough surface, and numerous grain boundaries.

[0088] Examples 2, 6, and 7 are parallel experimental examples of preparing CsPbIBr2 perovskite films under different heat treatment temperature and treatment time conditions. Compared to Example 2, Example 6 had a lower heat treatment temperature and shorter treatment time, resulting in imperfect CsPbIBr2 perovskite crystallization. Example 7 had a higher heat treatment temperature and longer treatment time, resulting in agglomeration of CsPbIBr2 perovskite film particles, the formation of small pores, and increased roughness. Example 2 had the most optimal heat treatment temperature and time, resulting in the highest quality CsPbIBr2 perovskite.

[0089] Example 8

[0090] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0091] (2) Preparation of CsPbIBr2 perovskite film

[0092] 0.367 g of PbBr2 and 0.259 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70 °C by stirring, and then phenylthiourea (PTU) (12.52 mg) accounting for 2 wt% of the total amount of PbBr2 and CsI was added and dissolved;

[0093] The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50°C, and the CsPbIBr2 perovskite precursor solution was applied to the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate by spin coating at a speed of 2500 rpm for 30 seconds, followed by heat treatment at 200°C for 15 minutes to form a CsPbIBr2 perovskite film. The SEM photograph of the CsPbIBr2 perovskite film is shown in FIG. Figure 14 As shown, the CsPbIBr2 perovskite film is dense and pore-free;

[0094] (3) Preparation of carbon-based inorganic CsPbIBr2 perovskite solar cells using FTO / TiO2 / CsPbIBr2 / carbon electrodes

[0095] A carbon layer was applied to the surface of the CsPbIBr2 perovskite film to prepare a carbon-based battery with a structure of FTO / TiO2 / CsPbIBr2 / carbon electrode; the photoelectric performance of the battery was 100mW / cm 2 Under simulated sunlight (AM1.5), the cell efficiency was measured using a Keithley 2400 digital source meter and was found to be 9.21%.

[0096] Example 9

[0097] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0098] (2) Preparation of CsPbIBr2 perovskite film

[0099] 0.367 g of PbBr2 and 0.259 g of CsI were dissolved in 1 ml of dimethyl sulfoxide (DMSO) at 70° C. by stirring, and then phenylthiourea (PTU) (18.78 mg) accounting for 3 wt% of the total amount of PbBr2 and CsI was added to dissolve the FTO / TiO2 substrate prepared according to Example 1. The FTO / TiO2 substrate prepared according to Example 1 was preheated to 50° C. and the CsPbIBr2 perovskite precursor solution was applied to the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate by spin coating at a spin coating speed of 2500 rpm for 30 s. The perovskite film was then heat treated at 200° C. for 15 minutes to form a CsPbIBr2 perovskite film. The SEM photograph of the CsPbIBr2 perovskite film is shown in FIG. Figure 15As shown, the CsPbIBr2 perovskite film is dense and pore-free;

[0100] (3) Preparation of carbon-based inorganic CsPbIBr2 perovskite solar cells using FTO / TiO2 / CsPbIBr2 / carbon electrodes

[0101] A carbon layer was applied to the surface of the CsPbIBr2 perovskite film to prepare a carbon-based battery with a structure of FTO / TiO2 / CsPbIBr2 / carbon electrode; the photoelectric performance of the battery was 100mW / cm 2 Under simulated sunlight (AM1.5), the cell efficiency was measured using a Keithley 2400 digital source meter and was found to be 9.87%.

[0102] Example 10

[0103] (1) Preparation of FTO / TiO2 substrate is the same as in Example 1;

[0104] (2) Preparation of CsPbIBr2 perovskite film

[0105] 0.404 g of PbBr2 and 0.285 g of CsI were dissolved in 1 mL of dimethyl sulfoxide (DMSO) at 70° C. by stirring to form a 1.1 mol / L concentration solution; then phenylthiourea (PTU) (17.225 mg) accounting for 2.5 wt% of the total amount of PbBr2 and CsI was added and dissolved; the FTO / TiO2 substrate prepared according to Example 1 was preheated to 50° C., and the CsPbIBr2 perovskite precursor solution was applied to the surface of the TiO2 mesoporous layer of the FTO / TiO2 substrate by spin coating at a spin coating speed of 2500 rpm for 30 s, and then heat treated at 200° C. for 15 minutes to form a CsPbIBr2 perovskite film layer; the SEM photograph of the CsPbIBr2 perovskite film is shown in FIG. Figure 16 As shown, the CsPbIBr2 perovskite film is uniform, dense, and has no pinholes;

[0106] (3) Preparation of carbon-based inorganic CsPbIBr2 perovskite solar cells using FTO / TiO2 / CsPbIBr2 / carbon electrodes

[0107] A carbon layer was applied to the surface of the CsPbIBr2 perovskite film to prepare a carbon-based battery with a structure of FTO / TiO2 / CsPbIBr2 / carbon electrode; the photoelectric performance of the battery was 100mW / cm 2 Under simulated sunlight (AM1.5), the cell efficiency was measured using a Keithley 2400 source meter and was found to be 9.16%.

[0108] The above are merely specific embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for improving the photoelectric performance and stability of a perovskite solar cell using a phenylthiourea bifunctional additive, wherein the perovskite solar cell comprises an FTO glass substrate, on which a dense TiO2 layer, a TiO2 mesoporous layer, a CsPbIBr2 perovskite film layer, and a carbon electrode are sequentially provided, characterized in that: The preparation process of the CsPbIBr2 perovskite film layer is as follows: (1) Preparation of CsPbIBr2 perovskite precursor solution PbBr2 and CsI are dissolved in dimethyl sulfoxide (DMSO) at 70°C with stirring to form a PbBr2 and CsI mixed solution with a concentration of 0.7 mol / L to 1.2 mol / L; phenylthiourea (PTU) is then added to the PbBr2 and CsI mixed solution in an amount of 1% to 5% of the total mass of the PbBr2 and CsI, and the mixture is stirred and dissolved to obtain a CsPbIBr2 perovskite precursor solution; (2) Preparation of CsPbIBr2 perovskite film A TiO2 dense layer and a TiO2 mesoporous layer are sequentially prepared on the surface of an FTO glass sheet to obtain an FTO glass sheet with a titanium dioxide layer; the FTO glass sheet with the titanium dioxide layer is preheated to 50°C, and a CsPbIBr2 perovskite precursor solution is spin-coated onto the surface of the TiO2 mesoporous layer by a spin-coating method at a spin-coating speed of 2500 rpm for 30 seconds, and then heat-treated at 150°C to 300°C for 5 to 20 minutes to form a CsPbIBr2 perovskite film layer.

2. The method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive according to claim 1, wherein: The molar ratio of PbBr2 to CsI is 1:

1.

3. The method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive according to claim 1, wherein: The added amount of the phenylthiourea accounts for 2% to 3% of the total mass of PbBr2 and CsI.

4. The method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive according to claim 1, wherein: The added amount of the phenylthiourea accounts for 2.5% of the total mass of PbBr2 and CsI.

5. The method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive according to claim 1, wherein: The concentration of the mixed solution of PbBr2 and CsI is 0.85 mol / L~1.1 mol / L.

6. The method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive according to claim 1, wherein: The concentration of the mixed solution of PbBr2 and CsI is 1 mol / L.

7. The method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive according to claim 1, wherein: When preparing the TiO2 dense layer, a 0.15 mol / L bis(acetylacetonate) diisopropyl titanate ethanol solution was spin-coated onto the cleaned FTO glass surface at a spin-coating speed of 4500 rpm for 45 seconds, and then heat-treated at 450°C for 30 minutes to form a TiO2 dense layer on the FTO glass surface.

8. The method for improving the photoelectric performance and stability of perovskite solar cells using a phenylthiourea bifunctional additive according to claim 1, wherein: When preparing the TiO2 mesoporous layer, the ethanol-diluted TiO2 colloid is spin-coated onto the surface of the TiO2 dense layer. The weight ratio of ethanol to colloid in the ethanol-diluted TiO2 colloid is 15:

1. The spin-coating speed is 4000 rpm and the spin-coating time is 30 s. Then, the TiO2 mesoporous layer is formed on the surface of the TiO2 dense layer after heat treatment at 450°C for 30 minutes.

Images