An all-inorganic CsPbBr3 perovskite solar cell based on multifunctional polymer-modified SnO2 and its application

Abstract

The present invention provides an all-inorganic CsPbBr3 perovskite solar cell based on multifunctional polymer-modified SnO2 and its application. An electron transport layer is prepared by spin-coating a SnO2 quantum dot solution with polyacrylic acid on FTO. A PAA layer is coated on the electron transport layer as a pre-buried bottom interface. A CsPbBr3 layer is formed on the PAA layer by a multi-step spin coating method. A carbon electrode is coated on the surface of the CsPbBr3 layer to prepare a solar cell. The present invention uses PAA to hinder the aggregation of SnO2 quantum dots in the solution, thereby obtaining a high-quality electron transport layer. The PAA layer can passivate the uncoordinated Sn on the surface of the electron transport layer. 4+ and the uncoordinated Pb in the CsPbBr3 layer 2+ The solar cell of the present invention has high efficiency and good stability, and has practical and economic value in promoting the industrialization of perovskite solar cells.

Description

Technical Field

[0001] The present invention belongs to the field of new materials and new energy technologies, and particularly relates to an all-inorganic CsPbBr3 perovskite solar cell based on multifunctional polymer-modified SnO2 and its application. Background Art

[0002] As one of the main new energy sources, solar energy naturally shoulders the heavy burden of achieving the "carbon peak and carbon neutrality" goals. Among them, solar cells are one of the main ways to directly utilize solar energy. After more than 40 years of development, although the highest certified photoelectric conversion efficiency of single-crystal silicon solar cells has reached 26.1%, it requires single-crystal silicon rods with a purity of up to 99.999% as raw materials, which is costly and has a complex manufacturing process. Perovskite solar cells have attracted widespread attention for their low production cost (half the cost of single-crystal silicon cells) and simple manufacturing process. After only a dozen years of rapid development, organic-inorganic hybrid perovskite solar cells have been comparable to traditional single-crystal silicon cells with their certified photoelectric conversion efficiency of 25.7%.

[0003] Organic-inorganic hybrid perovskite solar cells have poor stability under humid, hot, light and oxygen conditions and have been unable to be put into production. However, all-inorganic perovskite solar cells do not contain easily decomposable organic matter and are much more stable than organic-inorganic hybrid perovskite solar cells. Among them, CsPbBr3 perovskite solar cells can work stably for more than 100 days, and CsPbBr3 perovskite solar cells use cheap carbon electrodes to further reduce costs. By improving perovskite film preparation technology, interface engineering, component engineering, spectral engineering, strain regulation and other methods, the photoelectric conversion efficiency of CsPbBr3 perovskite solar cells has exceeded 11%.

[0004] Tin oxide (SnO2) has been widely used in the preparation of electron transport layers for perovskite solar cells due to its high electron mobility and high transmittance. However, due to van der Waals interactions between nanoparticles, SnO2 quantum dots in solution tend to spontaneously form aggregates, which precipitate at the bottom of the solution. In addition, there is a certain amount of hydroxyl groups on the surface of SnO2 quantum dots. During annealing, the surface hydroxyl groups easily dissociate, forming exposed Sn single bonds, leading to the generation of defects. Therefore, stabilizing the SnO2 quantum dots in the dispersion and reducing the hydroxyl groups on the surface of SnO2 quantum dots are crucial for manufacturing high-quality electron transport layers, promoting electron transport, and reducing carrier recombination. In addition, because the phase transition temperature of the CsPbBr3 layer is as high as 250°C, residual strain will be generated during the cooling process to room temperature. The residual strain has an adverse effect on the morphology of the CsPbBr3 layer, the crystal structure, the carrier transport at the interface, and the photoelectric conversion efficiency and stability of the complete device. Therefore, reducing the residual strain in the CsPbBr3 layer is crucial for fabricating high-efficiency and high-stability all-inorganic CsPbBr3 perovskite solar cells. Summary of the Invention

[0005] The purpose of the present invention is to provide an all-inorganic CsPbBr3 perovskite solar cell based on multifunctional polymer-modified SnO2 and its application, optimize the SnO2 electron transport layer, release the thermal strain in the CsPbBr3 layer, promote the transport of carriers, and improve the performance of the all-inorganic CsPbBr3 perovskite solar cell.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0007] An all-inorganic CsPbBr3 perovskite solar cell based on multifunctional polymer-modified SnO2 is prepared by the following preparation method:

[0008] (1) Dissolving SnCl2 and thiourea (CH4N2S) in deionized water, stirring, centrifuging, removing precipitates, and filtering to obtain a SnO2 quantum dot solution;

[0009] (2) preheating the SnO2 quantum dot solution described in step (1); adding polyacrylic acid (PAA) powder to the preheated SnO2 quantum dot solution and stirring to obtain a PAA-modified SnO2 quantum dot solution, i.e., a PAA-SnO2 quantum dot solution;

[0010] (3) preheating the PAA-SnO2 quantum dot solution and the FTO conductive glass described in step (2); spin-coating the preheated PAA-SnO2 quantum dot solution on the preheated FTO conductive glass to obtain an FTO / PAA-SnO2 substrate;

[0011] (4) spin coating the PAA aqueous solution on the FTO / PAA-SnO2 substrate described in step (3) to obtain a PAA-SnO2 electron transport layer modified with a single layer of PAA, that is, to obtain an FTO / PAA-SnO2 / PAA substrate;

[0012] (5) preheating the FTO / PAA-SnO2 / PAA substrate and the PbBr2 solution described in step (4), spin-coating the preheated PbBr2 solution on the FTO / PAA-SnO2 / PAA substrate, and annealing to obtain a PbBr2 film;

[0013] (6) Spin coating a CsBr solution on the PbBr2 film described in step (5) to obtain a PAA-modified CsPbBr3 layer;

[0014] (7) Coating carbon paste on the CsPbBr3 layer described in step (6), annealing, preparing a carbon electrode, and obtaining an all-inorganic CsPbBr3 perovskite solar cell.

[0015] The present invention adds polyacrylic acid (PAA) powder to a SnO2 quantum dot solution. The carboxyl ligand units on the PAA long chain are used to bond and regulate the distribution of the SnO2 quantum dots in the solution, as well as the film formation state on FTO after spin coating and annealing. This results in a high-quality, uniform SnO2 electron transport layer, passivating defects within the SnO2 electron transport layer and facilitating charge extraction. A PAA layer is added between the SnO2 electron transport layer and the CsPbBr3 layer to form a pre-buried bottom interface, releasing residual strain in the CsPbBr3 layer and passivating defects.

[0016] The residual strain in the CsPbBr3 layer is because the thermal expansion coefficient of the CsPbBr3 layer is much larger than that of the SnO2 electron transport layer. Therefore, the expansion volume of the CsPbBr3 layer is larger at high temperatures. During cooling and shrinkage, the substrate shrinks very little, while the CsPbBr3 layer shrinks more. At this time, the substrate will hinder the shrinkage of the CsPbBr3 layer, and ultimately the CsPbBr3 layer will be subjected to tensile strain along the in-plane direction, that is, thermal strain.

[0017] The pre-buried bottom interface formed by the PAA layer further passivates the uncoordinated Sn on the surface of the SnO2 electron transport layer through the carboxyl ligand units on the PAA long chain. 4+ On the other hand, the uncoordinated Pb in the CsPbBr3 layer is passivated. 2+, thus playing an anchoring role. This anchoring effect formed by bonding is like a "spring" that provides a compressive strain to hinder the thermal expansion of the CsPbBr3 layer when CsPbBr3 thermally expands. In addition, during the CsPbBr3 film formation process, high temperature will cause PAA to partially volatilize into the CsPbBr3 layer. The carboxyl groups on PAA will react with Pb 2+ The thermal expansion of the CsPbBr3 layer is further hindered by coordination. Finally, the compressive strain provided by PAA at the interface and PAA in the CsPbBr3 layer offsets the tensile strain generated in the CsPbBr3 layer after annealing, achieving the purpose of in-situ compensation of thermal strain. After the residual strain of the perovskite film is released, larger grains can be formed, which reduces carrier recombination and improves the photoelectric conversion efficiency and stability of the device.

[0018] Furthermore, the molar ratio of SnCl2 to CH4N2S in step (1) is 0.8-1.2:1, and the molar concentration of SnCl2 is 0.1 mol / L-0.2 mol / L.

[0019] Furthermore, in step (2), after PAA is added to the preheated SnO2 quantum dot solution, the PAA concentration is 0.5 mg / mL to 5 mg / mL.

[0020] Furthermore, in step (2), after PAA is added to the preheated SnO2 quantum dot solution, the PAA concentration is 1 mg / mL. When modifying SnO2, the optimal PAA concentration is 1 mg / mL.

[0021] Furthermore, in step (2), the preheating temperature of the SnO2 quantum dot solution is 70°C to 90°C, and the preheating time is 3 minutes to 9 minutes; the stirring temperature after the PAA powder is added is 70°C to 90°C, and the stirring time is 5 minutes to 1 hour.

[0022] Furthermore, in step (3), the preheating temperature of the PAA-SnO2 quantum dot solution is 70°C to 90°C, the preheating time of the PAA-SnO2 quantum dot solution is 5 minutes to 30 minutes, the preheating time of the FTO conductive glass is 1 minute to 5 minutes, the spin coating speed is 1000 to 2000 rpm, and the acceleration is 300 to 800 rpm / s.

[0023] Furthermore, the concentration of the PAA aqueous solution in step (4) is 0.05 mg / mL to 0.5 mg / mL, the spin coating speed is 4000 to 6000 rpm, and the acceleration is 2000 to 3000 rpm / s.

[0024] Furthermore, the concentration of the PAA aqueous solution in step (4) is 0.1 mg / mL.

[0025] In this invention, PAA is applied as a single layer onto SnO2 to modify the interface between SnO2 and CsPbBr3. This layer modifying the SnO2 / CsPbBr3 interface is called a buried interface. Because PAA partially evaporates into the CsPbBr3 during this process, it is also called a pre-buried interface. The optimal concentration of a single PAA layer is 0.1 mg / mL.

[0026] Furthermore, in step (6), the CsBr solution is spin-coated multiple times on the PbBr2 film described in step (5) using a multi-step spin-coating method.

[0027] Furthermore, in the step (6), each time the CsBr solution is spin-coated, annealing is performed once, and the annealing temperature is 240° C. to 260° C.

[0028] The present invention also provides the use of the all-inorganic CsPbBr3 perovskite solar cell in preparing battery components and in power stations.

[0029] Furthermore, the open circuit voltage of the all-inorganic CsPbBr3 perovskite solar cell is 1.40-1.75 V, and the short circuit current is 6.5 mA·cm -2 ~9mA·cm -2 , the filling factor is 0.70~0.90, and the photoelectric conversion efficiency is 9%~11.5%.

[0030] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: the present invention prepares an all-inorganic CsPbBr3 perovskite solar cell based on multifunctional polymer-modified SnO2, and by adding PAA to the SnO2 quantum dot solution, the carboxyl ligand units on the PAA long chain are bonded to the SnO2 quantum dots, thereby hindering the aggregation of the SnO2 quantum dots in the solution, and the carboxyl ligand units on the PAA long chain can consume the hydroxyl groups on the SnO2 quantum dots, reducing the uncoordinated Sn in the SnO2 electron transport layer. 4+ During the film formation process, since PAA can form strong hydrogen bonds with metal oxides, PAA can adhere to FTO and bond with the Sn element on the FTO surface, thereby guiding the deposition of SnO2 quantum dots on FTO, improving the wettability of SnO2 quantum dots on FTO, and making the SnO2 electron transport layer more evenly distributed on FTO after PAA modification; in addition, the weakly acidic PAA can reduce the alkalinity of the SnO2 quantum dot solution, which is beneficial to improving the stability of the SnO2 / perovskite interface and charge extraction.

[0031] The present invention releases the residual strain in the CsPbBr3 layer by adding a PAA layer between the interface of the SnO2 electron transport layer and the CsPbBr3 layer to form a pre-buried bottom interface. The carboxyl ligand unit on the PAA long chain can passivate the uncoordinated Sn on the surface of the SnO2 electron transport layer. 4+ On the other hand, it can passivate the uncoordinated Pb in the CsPbBr3 layer. 2+ Moreover, at the phase transition temperature of 250℃, part of PAA will volatilize into the CsPbBr3 layer, further releasing the residual strain of the CsPbBr3 layer and passivating the Pb in the CsPbBr3 layer. 2+ The above strain release and defect passivation help to form large-grain CsPbBr3, reduce the defect state density, reduce the non-radiative recombination of carriers, promote the transmission of carriers at the interface, and significantly improve the battery performance.

[0032] The SnO2 electron transport layer prepared after PAA modification as described in the present invention is more uniform and has higher crystal quality; the maximum grain of the CsPbBr3 layer can reach 3.08μm, and the device structure of the assembled all-inorganic CsPbBr3 perovskite solar cell is FTO / PAA-SnO2 / PAA / CsPbBr3 / carbon electrode. Due to the improvement of carrier extraction and the reduction of carrier recombination, the photoelectric conversion efficiency of the entire device can reach 10.83%, and the open-circuit voltage can reach 1.674V. Moreover, the device can still maintain an initial photoelectric conversion efficiency of more than 90% for more than 120 days under conditions of 80% humidity or in a thermal environment of 80°C, and has good stability. This has important practical and economic value for promoting the industrialization process of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the preparation process and film formation process of the SnO2 quantum dot solution and PAA-SnO2 quantum dot solution proposed in the present invention.

[0034] Figure 2 These are the HRTEM images and surface SEM images of the SnO2 electron transport layer prepared in the present invention; among them, a and b are HRTEM images of SnO2 and PAA-SnO2; c, d, and e are surface SEM images of FTO, SnO2, and PAA-SnO2.

[0035] Figure 3 This is the surface SEM image of PAA-SnO2 prepared in the present invention, with a PAA addition concentration of 2 mg / mL.

[0036] Figure 4 These are AFM images of the SnO2 electron transport layer with different PAA addition concentrations prepared in the present invention.

[0037] Figure 5 These are cross-sectional SEM images of SnO2 and PAA-SnO2 prepared in the present invention.

[0038] Figure 6 These are the XRD patterns and FTIR patterns of the SnO2 electron transport layer prepared in the present invention; wherein, a is the XRD pattern of SnO2 and PAA-SnO2; b is the FTIR pattern of SnO2 and PAA-SnO2.

[0039] Figure 7 These are the XPS graphs of SnO2 and PAA-SnO2 prepared in the present invention; wherein, a is the XPS graph of Sn 3d; b is the XPS graph of O1s; c and d are the oxygen peak XPS graphs of SnO2 and PAA-SnO2.

[0040] Figure 8 UPS diagrams and device energy level diagrams of SnO2 and PAA-SnO2 prepared in the present invention; wherein, a is the secondary electron cutoff edge binding energy diagram; b is the onset binding energy diagram; c and d are the Tauc band gap diagrams of SnO2 and PAA-SnO2; e is the energy level diagram of the charge transfer process in the PAA-modified perovskite solar cell.

[0041] Figure 9 These are the light transmittance graphs and electrical conductivity graphs of the SnO2 electron transport layer with different PAA addition concentrations prepared in the present invention; wherein, a is the light transmittance graph, and b is the electrical conductivity graph.

[0042] Figure 10 Schematic diagram of the PAA layer proposed in the present invention volatilizing part of the PAA into the CsPbBr3 layer to play a defect passivation role.

[0043] Figure 11 Schematic diagram of the PAA layer proposed in the present invention used as a pre-buried bottom interface to passivate the interface between the SnO2 electron transport layer and the CsPbBr3 layer.

[0044] Figure 12 Schematic diagram of the in-situ compensation of thermal strain by the PAA layer proposed in the present invention.

[0045] Figure 13 The XRD pattern of PAA-modified CsPbBr3 prepared in the present invention and the calculated strain diagram.

[0046] Figure 14 The GIXRD patterns of the CsPbBr3 layer prepared by the present invention at different PAA addition concentrations are shown in Figure 2. Residual strain diagram; among them, Figures a, b, d, and e are GIXRD diagrams of the CsPbBr3 layer at different single-layer PAA addition concentrations, and Figures c and f are residual strain distribution diagrams.

[0047] Figure 15 This is the XPS graph of the CsPbBr3 layer prepared in the present invention; wherein, a is the XPS graph of Sn 3d; b is the XPS graph of Pb 4f.

[0048] Figure 16 These are the surface SEM images of the PbBr2 film, the surface SEM image of the CsPbBr3 layer, and the cross-sectional SEM image of the CsPbBr3 layer prepared in the present invention; among them, a, b, and c are not modified with PAA; d, e, and f are modified with PAA.

[0049] Figure 17 This is a diagram of the optical absorbance of the PAA-modified CsPbBr3 layer prepared in the present invention.

[0050] Figure 18 This is a complete device structure diagram of the all-inorganic CsPbBr3 perovskite solar cell modified with PAA prepared in the present invention.

[0051] Figure 19 These are device performance characterization diagrams of the all-inorganic CsPbBr3 perovskite solar cell modified with PAA prepared in the present invention; wherein, a is the JV curve diagram, b is the external quantum efficiency diagram, c is the steady-state output diagram, d is the steady-state photoluminescence diagram, e is the time-resolved photoluminescence diagram, f is the Mott–Schottky curve diagram, g is the space charge limited current diagram, h is the dark-state JV curve diagram, and i is the impedance diagram.

[0052] Figure 20 This is a long-term stability diagram of the all-inorganic CsPbBr3 perovskite solar cell modified with PAA prepared in the present invention under conditions of 80% humidity and room temperature; wherein, Figure a is a stability diagram of the photoelectric conversion efficiency, Figure b is a stability diagram of the open-circuit voltage, Figure c is a stability diagram of the short-circuit current density, and Figure d is a stability diagram of the fill factor.

[0053] Figure 21 This is a long-term stability diagram of the all-inorganic CsPbBr3 perovskite solar cell modified with PAA prepared in the present invention under the conditions of 0% humidity and 80°C; among them, Figure a is the stability diagram of the photoelectric conversion efficiency, Figure b is the stability diagram of the open circuit voltage, Figure c is the stability diagram of the short-circuit current density, and Figure d is the stability diagram of the fill factor. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described in detail below in conjunction with specific implementation methods.

[0055] Example 1: Preparation of PAA-modified all-inorganic CsPbBr3 perovskite solar cells

[0056] This embodiment provides an all-inorganic CsPbBr3 perovskite solar cell based on PAA modification, which is obtained by the following preparation method:

[0057] (1) 853 mg of SnCl2 and 338 mg of thiourea (CH4N2S) were dissolved in 30 mL of deionized water. The solution was placed on a magnetic stirrer and stirred at high speed for 36 h at room temperature. The solution was then centrifuged to remove the precipitate and filtered through a PTFE filter to obtain a yellow, transparent SnO2 quantum dot solution.

[0058] (2) 10 mL of SnO2 quantum dot solution was preheated at 80 °C in a beaker for 5 min. Different amounts of polyacrylic acid (PAA) powder were added to the SnO2 quantum dot solution and stirred at high speed for 15 min to obtain PAA-SnO2 quantum dot solutions with PAA concentrations of 0 mg / mL, 0.5 mg / mL, 1 mg / mL, and 2 mg / mL, respectively.

[0059] (3) The FTO conductive glass is first cleaned with an ultrasonic cleaner and then deeply cleaned with a plasma cleaner; the PAA-SnO2 quantum dot solution and the FTO conductive glass described in (2) are then placed on a heating table at 80°C for preheating, the preheating time of the PAA-SnO2 quantum dot solution is 15 minutes, and the preheating time of the FTO conductive glass is 3 minutes; the preheated PAA-SnO2 quantum dot solution is spin-coated on the preheated FTO conductive glass at a speed of 1500 rpm, an acceleration of 500 rpm / s, and a spin-coating time of 30 seconds, and an FTO / PAA-SnO2 substrate is obtained after annealing;

[0060] (4) 10 mL of deionized water was preheated at 80°C in a beaker for 10 min. Different amounts of PAA powder were added to the preheated deionized water and stirred at high speed for 15 min to obtain PAA aqueous solutions with PAA concentrations of 0 mg / mL, 0.05 mg / mL, 0.1 mg / mL, 0.2 mg / mL, and 0.3 mg / mL, respectively. The PAA aqueous solution was spin-coated onto an FTO / PAA-SnO2 substrate at a rotation speed of 5000 rpm, an acceleration of 2500 rpm / s, and a spin-coating time of 30 s. The FTO / PAA-SnO2 / PAA substrate was obtained after annealing at 80°C for 15 min.

[0061] (5) 734 mg of PbBr2 was dissolved in 2 mL of DMF and heated at 90°C until fully dissolved to obtain a 1 mol / L PbBr2 solution; the FTO / PAA-SnO2 / PAA substrate described in (4) was preheated on a 90°C heating table for 5 min, and the PbBr2 solution was preheated on a 90°C heating table for 15 min. The preheated PbBr2 solution was spin-coated on the FTO / PAA-SnO2 / PAA substrate at a speed of 2000 rpm, an acceleration of 1000 rpm / s, and a time of 30 s; after spin coating, the film was annealed on a 90°C heating table for 30 min to evaporate the DMF to obtain a PbBr2 film;

[0062] (6) 149 mg of CsBr was dissolved in 10 mL of anhydrous methanol and ultrasonicated for 30 min to obtain a 0.07 mol / L CsBr solution; the CsBr solution was spin-coated on the PbBr2 film described in (5) multiple times using a multi-step spin coating method at a rotation speed of 2000 rpm, an acceleration of 1000 rpm / s, and a time of 30 s. After each spin coating, the film was annealed on a heating table at 250°C for 5 min. This process was repeated 6 to 8 times until a uniform yellow CsPbBr3 perovskite film was formed;

[0063] (7) The carbon slurry was applied to the CsPbBr3 perovskite film by a blade coating method and annealed on a heating plate at 90°C for 15 min to obtain a complete all-inorganic CsPbBr3 perovskite solar cell. The device structure of the PAA-modified all-inorganic CsPbBr3 perovskite solar cell was FTO / PAA-SnO2 / PAA / CsPbBr3 / carbon electrode.

[0064] Example 2: Performance Characterization of PAA-Modified SnO2 Electron Transport Layer

[0065] 1. By adding PAA to the SnO2 quantum dot solution, the carboxyl ligand unit on the PAA long chain can reduce the agglomeration of SnO2 quantum dots and the hydroxyl groups on the surface of SnO2 quantum dots. During the film formation process, PAA can guide the distribution of SnO2 quantum dots on FTO to obtain a uniform and continuous SnO2 electron transport layer. The principle diagram is as follows: Figure 1 .

[0066] from Figure 1 It can be seen that after the SnO2 quantum dot solution is prepared, the SnO2 quantum dots tend to agglomerate, and there are hydroxyl groups on the surface of the SnO2 quantum dots. During the annealing process, the separation of hydroxyl groups causes oxygen vacancies in SnO2, resulting in the appearance of uncoordinated Sn 4 +By adding PAA to the SnO2 quantum dot solution, the carboxyl ligand units on the PAA long chain can be bonded to the SnO2 quantum dots, thereby hindering the aggregation of SnO2 quantum dots in the solution. In addition, the carboxyl ligand units on the PAA long chain can consume the hydroxyl groups on the SnO2 quantum dots, reducing the uncoordinated Sn on the surface of the SnO2 electron transport layer. 4+ During the film formation process, since PAA can form strong hydrogen bonds with metal oxides, PAA easily adheres to FTO and bonds with the Sn element on the FTO surface, thereby guiding the deposition of SnO2 quantum dots and improving the wettability of SnO2 quantum dots on FTO, so that the PAA-modified SnO2 electron transport layer is evenly distributed on FTO; in addition, the weakly acidic PAA can reduce the alkalinity of the SnO2 quantum dot solution, which is beneficial to improving the stability of the SnO2 / perovskite interface and charge extraction.

[0067] 2. HRTEM images of SnO2 quantum dot solutions with or without PAA added, as well as surface SEM images of FTO, SnO2 and PAA-SnO2, are tested separately. Figure 2 shown.

[0068] from Figure 2 As can be seen from Figures a and b, the interplanar spacing of SnO2 quantum dots on the (110) plane with or without PAA is 0.335 nm, which indicates that PAA is not incorporated into SnO2 and it is still rutile SnO2. In addition, the modification of PAA makes the interplanar spacing more obvious, which indicates that the crystallization performance of PAA-SnO2 (the addition concentration of PAA in PAA-SnO2 is 1 mg / mL) is better. Figure 2 It can be seen from Figure c that the FTO surface is an uneven surface with a certain degree of roughness; Figure 2 In Figure d, it can be seen that after SnO2 quantum dots are covered on FTO, the roughness of the substrate is reduced and it becomes smoother, but quantum dot clusters can be seen, confirming the agglomeration phenomenon of SnO2 quantum dots; Figure 2 It can be seen from Figure e that the roughness of the substrate is also reduced after PAA-SnO2 quantum dots are covered on FTO, but the quantum dot clusters are not obvious, which shows that the addition of PAA plays a positive role in the dispersion of SnO2 quantum dots.

[0069] 3. Test the surface SEM image when the PAA concentration is too high, such as Figure 3 shown.

[0070] from Figure 3It can be seen that when the added concentration of PAA reaches 2 mg / mL, chain-distributed SnO2 quantum dots can be seen on the surface of the SnO2 electron transport layer. This may be because when the PAA concentration is too high, the carboxyl groups between PAAs will be connected by hydrogen bonds, thereby forming multiple parallel PAA long chains, which will inevitably affect the quality and roughness of the film.

[0071] 4. Test the AFM images of SnO2 electron transport layer under different PAA addition concentrations, such as Figure 4 shown.

[0072] The concentrations of PAA added were 0 mg / mL, 0.5 mg / mL, 1 mg / mL and 2 mg / mL; Figure 4 It can be seen that the root mean square roughness of the SnO2 electron transport layer without PAA modification is the largest, with a value of 16.3 nm. The root mean square roughness of the SnO2 electron transport layer is the smallest at a PAA addition concentration of 1 mg / mL, with a value of 14.5 nm. The increase in the root mean square roughness of the SnO2 electron transport layer at a PAA addition concentration of 2 mg / mL is due to Figure 3 caused by the phenomenon described above.

[0073] 5. The cross-sectional SEM images of the SnO2 electron transport layer with or without PAA added are shown below. Figure 5 shown.

[0074] from Figure 5 It can be seen that the distribution of SnO2 quantum dots on FTO without the addition of PAA is uneven, and the distribution of SnO2 quantum dots is not seen on some protrusions. The distribution of SnO2 quantum dots on FTO after modification with 1 mg / mL PAA is uniform, smooth and complete.

[0075] 6. Test the XRD patterns and Fourier transform infrared spectra (FTIR) of the SnO2 electron transport layer with or without PAA, as shown in Figure 6. Figure 6 shown.

[0076] from Figure 6 As can be seen from Figure a, the XRD peak position of the SnO2 electron transport layer without PAA is the same as that of the SnO2 electron transport layer with 1 mg / mL PAA added. This once again proves that PAA is not incorporated into SnO2, but only plays a modifying role. In addition, the peak intensity of the SnO2 electron transport layer with 1 mg / mL PAA added is higher, which indicates that the crystallization performance of SnO2 is better after being modified with 1 mg / mL PAA, which is consistent with the Figure 2 The (110) plane has a clear interplanar spacing in Figure b. Figure 6 As can be seen from Figure b, the main C=O peaks and Sn-O peaks are from 1694 to 1691 cm -1and 604~614cm -1 This phenomenon indicates the existence of PAA and its reaction with SnO2, making the arrangement of tin oxide closer.

[0077] 7. Test the XPS graphs of SnO2 electron transport layer with or without PAA, such as Figure 7 shown.

[0078] from Figure 7 As can be seen from Figure a, for the 1 mg / mL PAA-modified SnO2 electron transport layer, the increase in the binding energy of Sn 3d indicates that a chemical interaction occurs between PAA and the SnO2 electron transport layer, and the oxygen vacancies are filled after coordination with Sn; Figure 7 Figure b shows that the peak intensity of the O1s peak of the SnO2 electron transport layer modified with 1 mg / mL PAA increases, which indicates that the oxygen content in the SnO2 electron transport layer increases. The above phenomenon once again proves the presence of PAA; Figure 7 Figures c and d show that the O1s peak can be divided into two peaks, of which the low binding energy peak comes from the lattice oxygen of SnO2 (O Sn ), while the peak with high binding energy belongs to vacancy oxygen (O OH ), from the ratio of the oxygen peak, it can be seen that the ratio of the SnO2 electron transport layer modified with 1 mg / mL PAA is smaller, which once again shows that the presence of PAA passivates the oxygen vacancy defects.

[0079] 8. Test the UPS diagram of SnO2 electron transport layer with or without PAA, such as Figure 8 shown.

[0080] from Figure 8 As can be seen from Figure a, the Fermi levels of different SnO2 electron transport layers were calculated by measuring the energy of the cutoff edge. After modification with 1 mg / mL PAA, the Fermi level increased from -4.76 to -4.51 eV; Figure 8 As can be seen from Figure b, the valence band of the SnO2 electron transport layer can be obtained by measuring the onset energy. After modification with 1 mg / mL PAA, the valence band increases from 3.52 to 3.64 eV. Figure 8 Figures c and d can be used to calculate the band gap values ​​of different SnO2 electron transport layers. Through the above calculations, it can be finally determined that the conduction band increases from -4.48 to -4.36 eV after 1 mg / mL PAA modification, which indicates that electrons are more likely to jump from the CsPbBr3 layer to the SnO2 electron transport layer, effectively inhibiting the electron accumulation in the CsPbBr3 layer, thereby reducing the recombination loss and improving the voltage output; the detailed energy level diagram is shown in Figure 4. Figure 8 As shown in Figure e.

[0081] 9. Test the light transmittance and conductivity of the SnO2 electron transport layer at different PAA concentrations. Figure 9 shown.

[0082] from Figure 9 As can be seen from Figure a, when the concentration of PAA is 1 mg / mL, the transmittance of the SnO2 electron transport layer to light is the highest, which allows the CsPbBr3 layer to fully and effectively utilize the incident photons; therefore, Figure 9 As can be seen from Figure b, by recording the IV curve of FTO / SnO2 or (PAA-SnO2), it can be seen that the slope of the SnO2 electron transport layer is the largest at 1 mg / mL, so the conductivity of the SnO2 electron transport layer is the largest at 1 mg / mL. This result shows that the oxygen vacancies are improved after modification by PAA, so PAA-SnO2 has good charge extraction ability and high conductivity.

[0083] Example 3: Characterization of the in-situ compensation of thermal strain in the CsPbBr3 layer by the PAA layer

[0084] 1. A PAA layer is coated on the SnO2 electron transport layer to form a pre-buried bottom interface. During the high-temperature annealing process, a portion of the PAA evaporates into the CsPbBr3 layer, thereby regulating the formation of the CsPbBr3 layer. The principle diagram is shown in the figure. Figure 10 shown.

[0085] from Figure 10 It can be seen that the PAA layer is sandwiched between the SnO2 electron transport layer and the PbBr2 film as a pre-buried bottom interface. Since the phase transition temperature of CsPbBr3 is as high as 250°C, and the boiling point of PAA is only 116°C, part of the PAA in the single-layer PAA will evaporate to the CsPbBr3 layer within 5 minutes of annealing, thereby regulating the formation of the CsPbBr3 layer. After cooling to room temperature, a PAA-modified CsPbBr3 layer is formed.

[0086] 2. The PAA layer forms a pre-buried bottom interface, passivating the defects at the interface of the CsPbBr3 layer. The PAA volatilized into the CsPbBr3 layer further modifies the vacancy defects inside the CsPbBr3 layer. The principle diagram is shown in the figure. Figure 11 .

[0087] from Figure 11 It can be seen that, on the one hand, there are Sn single bonds formed after the separation of hydroxyl groups during annealing on the surface of SnO2 electron transport layer, and the carboxyl ligand units on the long chain of monolayer PAA can passivate the uncoordinated Sn on the surface of SnO2 electron transport layer. 4+ On the other hand, it can passivate the uncoordinated Pb in the CsPbBr3 layer. 2+The PAA layer reduces the recombination of carriers at the interface by passivating the vacancy defects at the interface, thereby enhancing the binding energy between the SnO2 electron transport layer and the CsPbBr3 layer; in addition, the PAA volatilized into the CsPbBr3 layer further modifies the vacancy defects inside the CsPbBr3 layer, which is conducive to obtaining high-quality large-grain CsPbBr3.

[0088] 3. The PAA layer is used to form a pre-buried bottom interface to release the residual strain in the CsPbBr3 layer and form a low-strain CsPbBr3 layer. The principle diagram is as follows Figure 12 .

[0089] from Figure 12 It can be seen that the residual strain in the CsPbBr3 layer is because the thermal expansion coefficient of the CsPbBr3 layer is much larger than that of the SnO2 electron transport layer. Therefore, the expansion volume of the CsPbBr3 layer is larger at high temperature. When cooling and shrinking, the shrinkage of the substrate is very small, and the shrinkage of the CsPbBr3 layer is relatively large. At this time, the substrate will hinder the shrinkage of the CsPbBr3 layer, and ultimately the CsPbBr3 layer will be subjected to tensile strain in the in-plane direction, that is, thermal strain; the pre-buried bottom interface formed by the PAA layer is connected to the SnO2 electron transport layer through the carboxyl ligand unit on the PAA long chain and the uncoordinated Sn 4+ connected, and on the other hand, with the uncoordinated Pb in the CsPbBr3 layer 2+ The PAA is connected to the Pb3 layer, thus playing an anchoring role. This anchoring effect formed by bonding acts like a "spring" and provides a compressive strain to hinder the thermal expansion of the CsPbBr3 layer when the CsPbBr3 layer expands thermally. In addition, during the CsPbBr3 film formation process, the high temperature will cause the PAA to partially volatilize into the CsPbBr3 layer. The carboxyl groups on the PAA will react with the Pb3 layer to form a compressive strain. 2+ The coordination further hinders the thermal expansion of the CsPbBr3 layer. Ultimately, the compressive strain provided by the PAA at the interface and the PAA in the CsPbBr3 layer offsets the tensile strain generated in the CsPbBr3 layer after annealing, achieving the purpose of in-situ compensation of thermal strain.

[0090] 4. The XRD patterns of the CsPbBr3 layer with or without PAA were tested respectively, and the strain of the CsPbBr3 layer was calculated by the Williamson-Hall equation, as shown in Figure 4. Figure 13 shown.

[0091] from Figure 13As can be seen from Figure a, 0.1 mg / mL PAA pre-buried bottom interface can improve the crystallization strength of the CsPbBr3 layer, and no impurity peaks appear. The strain value of the CsPbBr3 layer is calculated by the Williamson-Hall equation based on the data in the XRD diagram. After PAA modification, the strain of the CsPbBr3 layer is only 0.00178.

[0092] 5. The GIXRD patterns of the CsPbBr3 layer with different PAA layer addition concentrations were tested, and the residual strain distribution obtained from GIXRD (2θ data as function), such as Figure 14 shown.

[0093] The concentrations of PAA added to the layer were 0 mol / L, 0.05 mol / L, 0.1 mol / L, and 0.2 mol / L respectively; Figure 14 As can be seen from Figures a, b, d, and e, the peaks all shift to the left with the increase of the grazing incidence angle, indicating that the film is tensile strained in the in-plane direction. As the concentration of the PAA layer increases, the offset of the peak corresponding to the large grazing incidence angle decreases, indicating that PAA releases the residual strain of the CsPbBr3 layer. In addition, when the concentration of the PAA layer is 0.1 mol / L, the peak intensity is significantly improved, indicating that the crystallization performance of the CsPbBr3 layer is best at this concentration. Figure 14 Figures c and f show that the 2θ data is used as The residual strain of the CsPbBr3 layer can be calculated by the function. The larger the slope, the larger the residual strain. It can be found that the slope is the smallest when the concentration of the PAA layer is 0.1 mol / L, that is, when the concentration of the PAA layer is 0.1 mol / L, the tensile strain of the film is the smallest.

[0094] 6. Test the XPS graphs of SnO2 electron transport layer and CsPbBr3 layer with or without PAA layer, such as Figure 15 shown.

[0095] from Figure 15 As can be seen from Figure a, the binding energy of Sn 3d in the SnO2 electron transport layer modified with 0.1 mg / mL PAA layer is significantly increased, indicating that chemical interaction occurs between the PAA layer and the SnO2 electron transport layer, and the binding energy of Sn 3d in the SnO2 electron transport layer is significantly increased. 4+ The Pb 4f of the CsPbBr3 layer grown on the 0.1 mg / mL PAA layer moves to a higher binding energy, indicating that the PAA layer and the CsPbBr3 layer also interact chemically, that is, the uncoordinated Pb 2+ interaction; the above XPS conclusion is the principle Figure 11 Provided evidence.

[0096] 7. The SEM images of the PbBr2 film and CsPbBr3 layer with or without the PAA layer are tested respectively, as shown in Figure 16 shown.

[0097] from Figure 16 The surface SEM images of the PbBr2 films (a) and (d) show that the 0.1 mg / mL PAA layer has little effect on the pores in the PbBr2 film, but the size of the PbBr2 grains increases to a certain extent, which lays the foundation for the large grains of CsPbBr3. The CsPbBr3 layer modified with the 0.1 mg / mL PAA layer has a larger grain size, and the maximum grain of the CsPbBr3 layer can reach 3.08 μm, which is inseparable from the strain release and defect passivation effect of PAA. The cross-sectional SEM image of the CsPbBr3 layer also shows that it is consistent with the above conclusion.

[0098] 8. Test the optical absorbance of the CsPbBr3 layer with or without PAA, such as Figure 17 shown.

[0099] from Figure 17 It can be seen that after modification with a 0.1 mg / mL PAA layer, the CsPbBr3 layer with large grains has a higher light absorption, which undoubtedly makes it easier for the CsPbBr3 layer to effectively utilize incident photons.

[0100] Example 4: Performance test of PAA-modified all-inorganic CsPbBr3 perovskite solar cells

[0101] 1. The device structure of the all-inorganic CsPbBr3 perovskite solar cell modified with PAA prepared in Example 1 is FTO / PAA-SnO2 / PAA / CsPbBr3 / carbon electrode, as shown in FIG. Figure 18 shown.

[0102] 2. Test the photoelectric performance of the whole device with or without PAA and the photoluminescence spectrum of the CsPbBr3 layer respectively. Figure 19 shown.

[0103] from Figure 19 As can be seen from Figure a, the photoelectric conversion efficiency of the entire device without PAA modification is only 8.13%. After 1 mg / mL PAA modifies the SnO2 electron transport layer, the photoelectric conversion efficiency is greatly improved to 10.36%. When 0.1 mg / mL single layer PAA passivates the defects of the CsPbBr3 layer and releases the strain, the photoelectric conversion efficiency is further improved to 10.83%, which is due to the high-quality SnO2 electron transport layer and the CsPbBr3 layer with large grains.

[0104] from Figure 19As can be seen in Figure b (there are two types of PAA modifications in the present invention: one is PAA modified only with SnO2 (1 mg / mL), represented by PAA-SnO2, and the other is modified with SnO2 (1 mg / mL) and then used as a single layer of PAA (0.1 mg / mL), represented by PAA-SnO2 / PAA). The external quantum efficiency of the full device after the two PAA modifications is higher, indicating that the integrated current density of the full device is also higher. In addition, the integrated current density of the full device under the PAA-SnO2 / PAA condition is 7.89 mA cm -2 This is consistent with the 7.93 mA cm under PAA-SnO2 / PAA conditions in the JV curve. -2 matches the current density.

[0105] from Figure 19 As can be seen from Figure c, the steady-state output performance of the entire device after PAA modification is better and the attenuation is lower. Whether PAA only modifies SnO2 or PAA modifies SnO2 as a single layer, the effect is better than that of the group without PAA.

[0106] from Figure 19 As can be seen from Figure d, after the PAA layer modifies the CsPbBr3 layer, the decrease in PL intensity indicates that PAA effectively suppresses carrier recombination and improves charge transfer, and the blue shift of the PL peak also proves that the internal defects of the device are reduced and carrier recombination is suppressed.

[0107] from Figure 19 As can be seen from the e-graph, the lifetime of the TRPL spectrum of the device modified by PAA is shorter, from the average lifetime of 1.99ns of the unmodified device to 1.22ns under the PAA-SnO2 / PAA condition. This indicates that the electrons generated by the CsPbBr3 layer can be extracted into the SnO2 electron transport layer more quickly, thereby reducing the non-radiative recombination between the SnO2 electron transport layer and the CsPbBr3 layer. Figure 19 As can be seen from the f figure, according to the CV curve converted by the Mott-Schottky equation, the built-in electric field (V bi ) increases after PAA modification, which also confirms that the electrons are transferred to the SnO2 electron transport layer instead of being captured by defects and undergoing non-radiative recombination.

[0108] from Figure 19 As can be seen from the g graph, after PAA modification, the trap filling limit voltage (V TFL ) directly indicates that the defect state density of the CsPbBr3 layer is reduced and the electron mobility is improved, which is consistent with Figure 19 The results of TRPL analysis are consistent with those of Figure e. Figure 19 As can be seen from the h figure, the leakage current of the whole device is smaller after PAA modification, which is attributed to Figure 19 Figure i shows that the composite resistance of the entire device increases after PAA modification.

[0109] 3. Test the long-term stability of the whole device at room temperature with and without PAA. The test results are as follows: Figure 20 shown.

[0110] from Figure 20 It can be seen that at room temperature with a humidity of 80%, the stability of the full device modified with 1 mg / mL PAA to modify SnO2 and then with a 0.1 mg / mL single layer PAA is significantly higher than that of the full device without PAA modification. This is mainly attributed to the more stable filling factor after PAA modification. After 120 days, the PAA-modified full device still maintains more than 80% of the initial photoelectric conversion efficiency.

[0111] 4. Test the long-term stability of the whole device under continuous high temperature with or without PAA. The test results are as follows: Figure 21 shown.

[0112] from Figure 21 It can be seen that in an environment with a temperature of 80°C and a humidity of 0%, the stability of the full device modified with 1 mg / mL PAA to modify SnO2 and then with a 0.1 mg / mL single layer PAA is also higher than that of the full device without PAA modification. After 120 days, the PAA-modified full device still maintains more than 80% of the initial photoelectric conversion efficiency.

[0113] The above 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 aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present invention.

Claims

1. An all-inorganic CsPbBr3 perovskite solar cell based on multifunctional polymer-modified SnO2, characterized in that: Prepared by the following preparation method: (1) Dissolving SnCl2 and thiourea in deionized water, stirring, centrifuging, removing precipitates, and filtering to obtain a SnO2 quantum dot solution; (2) preheating the SnO2 quantum dot solution described in step (1); adding polyacrylic acid powder to the preheated SnO2 quantum dot solution and stirring to obtain a PAA-modified SnO2 quantum dot solution, i.e., a PAA-SnO2 quantum dot solution; (3) preheating the PAA-SnO2 quantum dot solution and the FTO conductive glass described in step (2); spin-coating the preheated PAA-SnO2 quantum dot solution on the preheated FTO conductive glass to obtain an FTO / PAA-SnO2 substrate; (4) spin coating the PAA aqueous solution on the FTO / PAA-SnO2 substrate described in step (3) to obtain a PAA-SnO2 electron transport layer modified with a single layer of PAA, that is, to obtain an FTO / PAA-SnO2 / PAA substrate; (5) preheating the FTO / PAA-SnO2 / PAA substrate and the PbBr2 solution described in step (4), spin-coating the preheated PbBr2 solution on the FTO / PAA-SnO2 / PAA substrate, and annealing to obtain a PbBr2 film; (6) Spin coating a CsBr solution on the PbBr2 film described in step (5) to obtain a PAA-modified CsPbBr3 layer; (7) Coating carbon paste on the CsPbBr3 layer described in step (6), annealing, preparing a carbon electrode, and obtaining an all-inorganic CsPbBr3 perovskite solar cell.

2. The all-inorganic CsPbBr3 perovskite solar cell according to claim 1, characterized in that: The molar ratio of SnCl2 to CH4N2S in step (1) is 0.8-1.2:1, and the molar concentration of SnCl2 is 0.1 mol / L-0.2 mol / L.

3. The all-inorganic CsPbBr3 perovskite solar cell according to claim 1, characterized in that: In the step (2), after PAA is added to the preheated SnO2 quantum dot solution, the PAA concentration is 0.5 mg / mL to 5 mg / mL.

4. The all-inorganic CsPbBr3 perovskite solar cell according to claim 3, characterized in that: In the step (2), the preheating temperature of the SnO2 quantum dot solution is 70°C to 90°C, and the preheating time is 3 minutes to 9 minutes; the stirring temperature after the PAA powder is added is 70°C to 90°C, and the stirring time is 5 minutes to 1 hour.

5. The all-inorganic CsPbBr3 perovskite solar cell according to claim 1, characterized in that: In the step (3), the preheating temperature of the PAA-SnO2 quantum dot solution is 70°C to 90°C, the preheating time of the PAA-SnO2 quantum dot solution is 5 minutes to 30 minutes, the preheating time of the FTO conductive glass is 1 minute to 5 minutes, the spin coating speed is 1000 to 2000 rpm, and the acceleration is 300 to 800 rpm / s.

6. The all-inorganic CsPbBr3 perovskite solar cell according to claim 1, characterized in that: The concentration of the PAA aqueous solution in step (4) is 0.05 mg / mL to 0.5 mg / mL, the spin coating speed is 4000 to 6000 rpm, and the acceleration is 2000 to 3000 rpm / s.

7. The all-inorganic CsPbBr3 perovskite solar cell according to claim 1, characterized in that: In the step (6), the CsBr solution is spin-coated multiple times on the PbBr2 film described in the step (5) using a multi-step spin-coating method.

8. The all-inorganic CsPbBr3 perovskite solar cell according to claim 7, characterized in that: In the step (6), each time the CsBr solution is spin-coated, annealing is performed once, and the annealing temperature is 240° C. to 260° C.

9. Use of the all-inorganic CsPbBr3 perovskite solar cell according to any one of claims 1 to 8 in preparing battery components and in power stations.

10. The use of the all-inorganic CsPbBr3 perovskite solar cell according to claim 9 in preparing a battery component and in a power station, characterized in that: The all-inorganic CsPbBr3 perovskite solar cell has an open circuit voltage of 1.40-1.75 V and a short circuit current of 6.5 mA·cm -2 ~9mA·cm -2 , the filling factor is 0.70~0.90, and the photoelectric conversion efficiency is 9%~11.5%.

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