A method for preparing a cerium-doped tin oxide electron transport layer and its application in perovskite solar cells.

Abstract

This invention relates to the field of optoelectronic materials and devices, and in particular to a method for preparing a cerium-doped tin oxide electron transport layer and its application in perovskite solar cells. The method involves depositing a cerium-doped tin oxide electron transport layer using a chemical bath under isothermal conditions, followed by annealing. Based on this transport layer, an organic-inorganic hybrid upright perovskite solar cell with high efficiency and UV resistance is fabricated. The cerium-doped tin oxide electron transport layer disclosed in this invention successfully incorporates cerium ions into the tin oxide lattice, solving not only the problems of excessive oxygen vacancies on the tin oxide surface and excessive defects at the perovskite interface, but also giving the electron transport layer excellent UV resistance.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and devices, and in particular to a method for preparing a cerium-doped tin oxide electron transport layer and its application in perovskite solar cells. Background Technology

[0002] With the continuous depletion of traditional fossil fuels and the increasing prominence of energy crises and environmental problems, solar energy, as a new generation of clean energy, possesses advantages such as abundant reserves, green and clean operation, and economic convenience, and is considered one of the most promising forms of renewable energy. Among them, perovskite solar cells have attracted much attention due to their high performance and low cost. As a representative of third-generation solar cells, perovskite solar cells (PSCs) have achieved a photoelectric conversion efficiency of 26.7%, almost comparable to commercial crystalline silicon solar cells. Furthermore, due to their abundant raw materials, ability to be prepared using low-temperature liquid-phase methods, and low processing costs, perovskite solar cells have become a hot topic in photovoltaic research and application.

[0003] A typical planar perovskite solar cell device structure includes an electron transport layer (ETL), a perovskite light-absorbing layer, a hole transport layer (HTL), and an electrode layer. Among these, the electron transport layer (ETL) plays a crucial role in extracting and transporting photogenerated electrons and blocking holes to reduce carrier recombination at the interface. Chinese patent CN202010283071.2 discloses an inorganic inverted perovskite solar cell, its fabrication method, and its applications. It uses low-temperature cerium oxide as the electron transport layer material, which not only allows for low-temperature processing, effectively preventing damage to the perovskite photosensitive layer from high-temperature annealing, but also allows for dispersion using solvents that do not damage the perovskite photosensitive layer, thus successfully fabricating a highly efficient and stable all-inorganic inverted perovskite solar cell. However, the main problem with this patent is that it does not consider the significant charge recombination phenomenon at the interface due to numerous interface defects between the perovskite photosensitive layer and the electron transport layer. The neodymium-doped titanium oxide prepared by Liu's research group improved the injection and extraction efficiency of photoelectrons, exhibiting higher conductivity and lower electron mobility and trap state density. The final device achieved a photoelectric conversion efficiency of over 19% and better light stability, but this method did not improve the ultraviolet stability of the device.

[0004] Tin oxide is the optimal electron transport layer (ETL) material for planar perovskite solar cells (PSCs) due to its advantages such as wide band gap, high electron mobility, good chemical stability, low photocatalytic activity, and low-temperature fabrication capability. However, oxygen vacancies (V0.05) exist on the surface of tin oxide. O ), Tin gap (Sn) iInherent defects such as tin oxide (TI) lead to the spontaneous formation of high-density defect states at the electron transport layer / perovskite layer interface, causing severe charge recombination at the interface. This affects carrier extraction and transport, severely limiting the photoelectric conversion efficiency of the device. Furthermore, long-term ultraviolet (UV) irradiation causes photochemical reactions in the perovskite material, leading to decomposition or structural changes. These changes not only disrupt the crystal structure but also increase interfacial defects between the perovskite layer and the electron transport layer, adversely affecting the long-term stability of perovskite solar cells. Therefore, fabricating high-performance tin oxide electron transport layers and perovskite solar cells with excellent UV resistance are key challenges in promoting the industrialization of perovskite solar cells. Breakthroughs in these technologies can significantly improve the overall performance of the cells and enhance their stability and durability in practical applications, thus laying a solid foundation for the widespread adoption of perovskite solar cells. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a cerium-doped tin oxide electron transport layer and its application in perovskite solar cells. The method utilizes a cerium-containing tin oxide precursor solution to prepare a high-performance tin oxide electron transport layer, which can reduce the number of oxygen vacancies (V0) on the tin oxide surface. O ) and tin gap (Sn i In addition to addressing defects such as tin oxide, this method can also solve three main problems encountered when using tin oxide as an electron transport layer: First, the numerous surface defects of tin oxide make it easy for high-density defect states to spontaneously form at the interface with the perovskite layer; second, it solves the problem of poor tin oxide film quality, which affects the crystallinity of the perovskite light-absorbing layer during its growth, resulting in smaller grain size; and third, it solves the problem of decomposition or structural changes in perovskite materials caused by long-term ultraviolet irradiation.

[0006] To achieve the above objectives, this invention provides a method for preparing a cerium-doped tin oxide electron transport layer. The method involves depositing a cerium-containing precursor solution under isothermal conditions via a chemical bath, followed by annealing, to prepare the cerium-doped tin oxide electron transport layer. The method includes the following steps:

[0007] S1. Clean and dry the FTO substrate, and treat the surface of the FTO substrate with ultraviolet-ozone for 5 to 20 minutes or plasma cleaning for 1 to 5 minutes.

[0008] S2. After measuring deionized water and freezing it to form an ice-water mixture, urea, concentrated hydrochloric acid, mercaptoacetic acid and stannous dichloride dihydrate are slowly added to the ice-water mixture in sequence and stirred until completely dissolved to obtain a tin oxide precursor solution.

[0009] S3. Weigh out the cerium salt and add it to the tin oxide precursor solution obtained in S2 to obtain a tin oxide precursor solution containing cerium salt.

[0010] S4. The FTO substrate treated in S1 is immersed in the cerium-containing tin oxide precursor solution in S3, and deposition is carried out under constant temperature conditions by chemical bath method. After deposition is completed, the substrate is taken out and subjected to ultrasonic cleaning, drying and annealing treatment in sequence to obtain the cerium-doped electron transport layer.

[0011] Preferably, in S2, the pH of the tin oxide precursor solution is 0.5–2.0, and the amounts of each component are 6.250–25.000 g / L of urea, 6.250–25.000 mL / L of concentrated hydrochloric acid, 125–500 μL / L of mercaptoacetic acid, and 1.375–5.500 g / L of stannous dichloride dihydrate.

[0012] Preferably, in S3, the cerium salt is one or more cerium salts selected from cerium chloride, cerium phosphate, cerium nitrate, and cerium acetate; the concentration ratio of cerium ions to tin ions in the cerium-containing tin oxide precursor solution is 1% to 10%.

[0013] Preferably, in S4, the deposition temperature is 80–100°C and the reaction time is 1–5 h;

[0014] Preferably, in S4, the ultrasonic cleaning solution is one of ethanol, isopropanol, ethylene glycol, and propylene glycol; the ultrasonic cleaning time is 2–10 min; the annealing temperature is 140–200 °C; the annealing time is 30–90 min; and the thickness of the cerium-doped electron transport layer is 10–100 nm.

[0015] Preferably, if a thicker tin oxide film is required, the substrate surface after drying in step S4 is subjected to ultraviolet-ozone treatment for 15 minutes or plasma cleaning treatment for 3 minutes, and then step S4 is repeated to obtain a thicker cerium-doped electron transport layer.

[0016] An application of a cerium-doped tin oxide electron transport layer: The cerium-doped tin oxide electron transport layer prepared by the above method is applied to an organic-inorganic hybrid upright perovskite solar cell.

[0017] Preferably, the method for fabricating the organic-inorganic hybrid upright perovskite solar cell includes the following steps:

[0018] T1. Prepare a cerium-doped tin oxide electron transport layer on the surface of an FTO substrate and treat it with ultraviolet-ozone for 15 min or plasma cleaning for 3 min.

[0019] T2. Prepare an APbX3 structured perovskite light-absorbing layer on the surface of a cerium-doped tin oxide electron transport layer, wherein A is one or more of ammonium methylamine, formamidinium, cesium ions, and potassium ions, and X is one or more of I, Br, and Cl.

[0020] T3. A hole transport layer is prepared directly on the surface of a perovskite light-absorbing layer by spin coating.

[0021] T4. An electrode layer is prepared on the surface of the hole transport layer using thermal evaporation or magnetron sputtering processes.

[0022] Preferably, the material of the hole transport layer in T3 is 2,2',7,7'-tetratetra(4-methoxydiphenylamine)-9,9'-spirofluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], nickel oxide, copper thiocyanate, or copper iodide.

[0023] Preferably, the electrode layer in T4 is one or more of gold, silver, copper, indium tin oxide, and aluminum-doped zinc oxide, and the electrode thickness is 50-300 nm.

[0024] Mechanism of the invention:

[0025] This invention utilizes cerium salts to dope the electron transport layer of tin oxide. During the doping process, cerium ions interact with the lattice structure of tin oxide, suppressing the formation of defects such as oxygen vacancies on the surface of the tin oxide electron transport layer, improving the energy level alignment between tin oxide and the perovskite layer, and lowering the electron transport barrier. Furthermore, this electron transport layer not only effectively suppresses the generation of reactive oxygen species under ultraviolet light irradiation but also enhances the absorption capacity of ultraviolet light. This dual mechanism helps reduce the direct damage of ultraviolet light to the perovskite layer, thereby significantly improving the ultraviolet stability of perovskite solar cells. Simultaneously, cerium doping can effectively regulate the crystallization of tin oxide, making the electron transport layer flat and dense, thus promoting the growth of a larger grain size and fewer defects in the perovskite light-absorbing layer on its surface. This will effectively reduce the loss of photogenerated carriers, significantly improving the photoelectric conversion efficiency and ultraviolet resistance of perovskite solar cells.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] (1) Effectively suppressing oxygen vacancies and tin gaps in the electron transport layer: This invention discloses a cerium-doped electron transport layer. In-situ lattice doping of tin oxide is performed by cerium salt. Cerium ions are embedded in the tin oxide lattice and interact with its structure, suppressing the generation of defects such as surface oxygen vacancies. This significantly reduces the nonradiative recombination rate of charge carriers at the perovskite solar cell interface and improves the efficiency of charge carrier extraction and transport.

[0028] (2) Reducing the density of interface defect states and improving the crystallinity of perovskite films: The cerium-doped electron transport layer of this invention forms a good energy level match with the perovskite light-absorbing layer. At the same time, the upward shift of the conduction band top position of the cerium-doped tin oxide electron transport layer reduces the energy barrier of carriers at the interface, optimizing the extraction and transport behavior of carriers at the interface; in addition, it promotes the conformal growth of the tin oxide electron transport layer on the FTO substrate surface, making its surface smoother, improving the wettability of the electron transport layer, and helping the perovskite light-absorbing layer to grow epitaxially on its surface, generating a light-absorbing layer with larger grains and fewer defects, thereby significantly improving the photoelectric conversion efficiency of the device.

[0029] (3) Improved UV stability: Due to the in-situ lattice doping of tin oxide with cerium salt, the electron transport layer has a good UV resistance effect, which effectively reduces the direct damage of UV light to perovskite materials, thereby improving the UV stability of perovskite solar cells. In addition, the preparation method of the UV-resistant electron transport layer provided by the present invention is simple, low-cost, highly repeatable, highly scalable, and can be mass-produced, which helps to promote the commercial application of perovskite solar cells.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the upright perovskite solar cell structure containing a cerium-doped tin oxide electron transport layer according to the present invention;

[0032] Figure 2 This is the JV curve of the perovskite solar cell based on the cerium-doped tin oxide electron transport layer in Embodiment 1 of the present invention under AM 1.5G test conditions;

[0033] Figure 3 This is the JV curve of the perovskite solar cell based on the cerium-doped tin oxide electron transport layer in Embodiment 2 of the present invention under AM 1.5G test conditions;

[0034] Figure 4 This is the JV curve of the perovskite solar cell based on the cerium-doped tin oxide electron transport layer in Embodiment 3 of the present invention under AM 1.5G test conditions;

[0035] Figure 5 This is the JV curve of the perovskite solar cell based on the cerium-free tin oxide electron transport layer in Comparative Example 1 of the present invention under AM 1.5G test conditions.

[0036] Figure 6 This is a schematic diagram comparing the JV curves of the perovskite solar cells in Comparative Example 1 and Example 2 of the present invention under AM 1.5G test conditions.

[0037] Figure 7 These are high-resolution energy dispersive spectra of the tin oxide electron transport layer O1s prepared in Comparative Example 1 and Example 2 of this invention;

[0038] Figure 8 These are high-resolution energy dispersive spectroscopy (EDS) spectra of the tin oxide electron transport layer Ce3d prepared in Comparative Example 1 and Example 2 of this invention.

[0039] Figure 9 These are SEM images of the cross-sections of the tin oxide electron transport layers prepared in Comparative Example 1 and Example 2 of this invention, wherein... Figure 9 Image (a) in the image is the SEM image of Comparative Example 1, with a scale bar of 400 nm. Figure 9 (b) is the SEM image of Example 2, with a scale bar of 400 nm;

[0040] Figure 10 This is a schematic diagram comparing the electrical properties of the tin oxide electron transport layer prepared in Comparative Example 1 and Example 2 of this invention, wherein... Figure 10 (a) in the diagram is the conductivity diagram. Figure 10 (b) in the figure is the electron mobility diagram;

[0041] Figure 11 These are contact angle diagrams of the tin oxide electron transport layers prepared in Comparative Example 1 and Example 2 of this invention, wherein... Figure 11 (a) in the diagram is the contact angle diagram of Comparative Example 1. Figure 11 (b) in the figure is the contact angle diagram of Example 2;

[0042] Figure 12 These are SEM images of the perovskite light-absorbing layer surfaces prepared in Comparative Example 1 and Example 2 of this invention, wherein... Figure 12 Image (a) in the image is the SEM image of Comparative Example 1, with a scale bar of 500 nm. Figure 12 (b) is the SEM image of Example 2, with a scale bar of 500 nm;

[0043] Figure 13 This is a schematic diagram comparing the defect state density of the perovskite light-absorbing layer prepared in Comparative Example 1 and Example 2 of this invention, wherein, Figure 13 In Figure (a), the defect state density plot of Comparative Example 1 is shown. Figure 13 (b) in the figure is the defect state density diagram of Example 2;

[0044] Figure 14 This is a schematic diagram comparing the ultraviolet stability of the perovskite solar cells prepared in Comparative Example 1 and Example 2 of this invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0046] Example 1

[0047] This invention provides a cerium-doped tin oxide electron transport layer, the preparation method of which includes the following steps:

[0048] S1: Cleaning the FTO substrate: The substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, isopropanol, and anhydrous ethanol, each for 20 minutes. After cleaning and drying, it underwent UV-ozone treatment for 15 minutes or plasma treatment for 3 minutes to improve the hydrophilicity of the substrate surface. The FTO substrate dimensions were 15mm × 15mm × 2.2mm.

[0049] S2: After measuring 200 mL of deionized water and freezing it to form an ice-water mixture, slowly add 2.500 g of urea, 2.5 mL of concentrated hydrochloric acid, 50 μL of mercaptoacetic acid and 0.550 g of stannous dichloride dihydrate to the ice-water mixture in sequence, and stir until completely dissolved to obtain a tin oxide precursor solution.

[0050] S3. Weigh 14.8 mg of cerium chloride and add it to the tin oxide precursor solution obtained in S2 to obtain a tin oxide precursor solution containing cerium salt, wherein the concentration ratio of cerium ions to tin ions is 2.5%.

[0051] S4. The FTO substrate treated in S1 is immersed in the cerium-containing tin oxide precursor solution in S3, and then deposition is carried out at a constant temperature of 90°C. After deposition for 3.5 hours, the substrate is removed, ultrasonically cleaned with isopropanol for 5 minutes, dried, and annealed at 180°C for 1 hour to finally obtain the cerium-doped tin oxide electron transport layer.

[0052] Figure 1 This is a schematic diagram of the upright perovskite solar cell structure containing a cerium-doped tin oxide electron transport layer according to the present invention, as shown below. Figure 1 As shown, this embodiment provides a positive perovskite solar cell containing the above-mentioned cerium-doped tin oxide electron transport layer, the preparation method of which includes the following steps:

[0053] T1. Anneal the cerium-doped tin oxide electron transport layer deposited on the surface of the FTO substrate on a heating stage at 180°C for 10 min. After cooling to room temperature, treat with ultraviolet-ozone for 15 min or with plasma for 3 min for later use.

[0054] T2, Preparation of FA1-x MA x The specific steps for creating a perovskite light-absorbing layer with a PbI3 structure are as follows:

[0055] T2.1: Dissolve 691.5 mg of lead iodide in 1 mL of a mixed solvent of N,N-dimethylformamide (DMF) and N,N-dimethyl sulfoxide (DMSO), and stir on a magnetic stirrer until completely dissolved to obtain a lead iodide solution; wherein the volume ratio of DMF to DMSO solvent is 9:1.

[0056] T2.2: Dissolve 90 mg formammonium iodide (FAI), 6.4 mg methylammonium iodide (MAI), and 9 mg methylammonium chloride (MACl) in 1 mL of isopropanol (IPA) solvent and stir at room temperature until completely dissolved to obtain a mixed organic salt solution of FAI, MAI, and MACl.

[0057] T2.3: Under a nitrogen atmosphere, 50 μL of the lead iodide solution obtained in T2.1 was spin-coated onto the surface of a cerium-doped tin oxide electron transport layer; wherein the spin-coating speed was 1500 rpm, the spin-coating acceleration was 750 rpm / s, the spin-coating time was 35 s, and then annealed on a hot stage at 70 °C for 60 s to obtain a lead iodide film.

[0058] T2.4: Under a nitrogen atmosphere, 80 μL of the mixed organic salt solution obtained in T2.2 was spin-coated onto a lead iodide film. The spin-coating speed was 2000 rpm, the spin-coating acceleration was 2000 rpm / s, and the spin-coating time was 35 s. Then, the film was quickly transferred to an environment with a relative humidity of 30% to 40% and annealed at 150°C for 15 min to prepare a perovskite light-absorbing layer with a thickness of 700 nm.

[0059] T3. Preparation of the hole transport layer: First, 72.3 mg of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD) was dissolved in 1 mL of chlorobenzene (CB) solvent. Then, 28.8 μL of 4-tert-butylpyridine (tBP) and 17.5 μL of lithium bis(trifluoromethanesulfonate) imide (LiTFSI) solution were added and mixed evenly to prepare the hole transport layer solution. The solubility of LiTFSI solution was 520 mg / mL, and the solvent was acetonitrile. Finally, the prepared hole transport layer solution was spin-coated onto the surface of the passivation layer. The spin-coating speed was 2500 rpm, the spin-coating acceleration was 1250 rpm / s, and the spin-coating time was 40 s.

[0060] T5. Electrode layer preparation: Under high vacuum (below 10°C) -4 In a Pa environment, a silver electrode is deposited onto the hole transport layer by thermal evaporation. The electrode layer thickness is 100 nm.

[0061] Performance testing: The perovskite solar cell prepared in this embodiment was placed under AM 1.5G, 100mW cm⁻¹ heat. -2 Tested under illumination conditions, such as Figure 2 As shown, the reverse-scan photoelectric conversion efficiency of the perovskite solar cell is 23.35%, with an open-circuit voltage of 1.17V and a short-circuit current density of 25.01mA / cm². -2 The fill factor is 79.66%.

[0062] Example 2

[0063] Based on Example 1, the difference from Example 1 is that the concentration ratio of cerium ions to tin ions in the cerium salt-containing tin oxide precursor solution in S3 is 5%.

[0064] Performance testing: The perovskite solar cell prepared in this embodiment was placed under AM 1.5G, 100mW cm⁻¹ heat. -2 Tested under illumination conditions, such as Figure 3 As shown, the reverse-scan photoelectric conversion efficiency of the perovskite solar cell is 24.19%, with an open-circuit voltage of 1.17V and a short-circuit current density of 25.31mA / cm². -2 The fill factor is 81.98%.

[0065] Example 3

[0066] Based on Example 1, the difference is that the concentration ratio of cerium ions to tin ions in the cerium salt-containing tin oxide precursor solution in S3 is 10%.

[0067] Performance testing: The perovskite solar cell prepared in this embodiment was placed under AM 1.5G, 100mW cm⁻¹ heat. -2 Tested under illumination conditions, such as Figure 4 As shown, the reverse-scan photoelectric conversion efficiency of the perovskite solar cell is 22.84%, with an open-circuit voltage of 1.15V and a short-circuit current density of 24.31mA / cm². -2 The fill factor is 81.66%.

[0068] Comparative Example 1

[0069] Based on Example 1, the difference from Example 1 is that step S3 is omitted, that is, cerium salt is not added to the tin oxide precursor solution, thus obtaining a cerium-free tin oxide electron transport layer and a perovskite solar cell.

[0070] Performance testing: The perovskite solar cell prepared in Comparative Example 1 was placed under AM 1.5G, 100mW cm⁻¹ -2 Tested under illumination conditions, such as Figure 5As shown, the reverse-scan photoelectric conversion efficiency of the perovskite solar cell is 21.34%, with an open-circuit voltage of 1.13V and a short-circuit current density of 23.40 mA / cm². -2 The fill factor is 80.54%.

[0071] Figure 6 This is a schematic diagram comparing the JV curves of the perovskite solar cells in Comparative Example 1 and Example 2 of the present invention under AM 1.5G test conditions. Figure 6 As shown, the photoelectric conversion efficiency of perovskite solar cells based on cerium-doped tin oxide electron transport layers was significantly improved, from the initial 21.34% to 24.19%.

[0072] Figure 7 These are high-resolution energy dispersive spectroscopy (EDS) spectra of the tin oxide electron transport layer O1s prepared in Comparative Example 1 and Example 2 of this invention, as shown in the figure. Figure 7 As shown, by targeting vacant oxygen (V O The calculation of the peak area, compared to the undoped tin oxide electron transport layer, shows that the vacant oxygen (V0) in the cerium-doped tin oxide electron transport layer... O The reduction in peak area indicates that the defect states such as oxygen vacancies on its surface are significantly suppressed, which is beneficial for the extraction and transport of photogenerated carriers.

[0073] Figure 8 These are high-resolution energy dispersive spectroscopy (EDS) images of the tin oxide electron transport layer Ce3d prepared in Comparative Example 1 and Example 2 of this invention; as shown... Figure 8 As shown, by performing Ce element analysis on the surface of the tin oxide electron transport layer prepared in Example 2 and Comparative Example 1, Ce element signals were found on the surface of the tin oxide electron transport layer prepared in Example 2, indicating that cerium ions exist on the surface of the tin oxide electron transport layer.

[0074] Figure 9 These are SEM images of the cross-sections of the tin oxide electron transport layer prepared in Comparative Example 1 and Example 2 of this invention; as shown Figure 9 (a) and Figure 9 As shown in (b) of Example 2, the surface of the tin oxide electron transport layer is smoother.

[0075] Figure 10 This is a schematic diagram comparing the electrical properties of the tin oxide electron transport layer prepared in Comparative Example 1 and Example 2 of this invention; Figure 10 (a) in the diagram is the conductivity diagram; Figure 10 (b) in the figure is the electron mobility diagram, which is derived from... Figure 10 It is known that cerium-doped tin oxide electron transport layer has higher conductivity and electron mobility, indicating that cerium-doped tin oxide electron transport layer is more conducive to carrier transport.

[0076] Figure 11These are contact angle diagrams of the tin oxide electron transport layer prepared in Comparative Example 1 and Example 2 of this invention; as shown Figure 11 (a) and Figure 11 As shown in (b), compared with the tin oxide electron transport layer prepared in Comparative Example 1, the wetting contact angle of the cerium-doped tin oxide electron transport layer prepared in Example 2 is 32.5°, indicating that the wettability of the electron transport layer surface is further improved after cerium doping, which is conducive to the epitaxial growth of the perovskite light-absorbing layer on the surface of the tin oxide electron transport layer.

[0077] Figure 12 These are SEM images of the perovskite light-absorbing layer surfaces prepared in Comparative Example 1 and Example 2 of this invention; as shown Figure 12 (a) and Figure 12 As shown in (b), the perovskite light-absorbing layer prepared on the surface of the cerium-doped tin oxide electron transport layer has a larger average grain size and fewer pores, indicating that the perovskite light-absorbing layer is of higher quality.

[0078] Figure 13 This is a schematic diagram comparing the defect state densities of the perovskite light-absorbing layers prepared in Comparative Example 1 and Example 2 of this invention; as shown Figure 13 (a) and Figure 13 As shown in (b), the perovskite light-absorbing layer prepared on the surface of the cerium-doped tin oxide electron transport layer has a lower space charge confinement voltage (0.19V), indicating that the perovskite light-absorbing layer prepared by it has fewer defects.

[0079] Figure 14 This is a schematic diagram comparing the ultraviolet stability of the perovskite solar cells prepared in Comparative Example 1 and Example 2 of this invention. Figure 14 As shown, the perovskite solar cell based on the cerium-doped tin oxide electron transport layer maintained 77% of its initial efficiency after 260 h of ultraviolet light irradiation, indicating that the perovskite solar cell has good UV resistance.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a cerium-doped tin oxide electron transport layer, characterized in that: Includes the following steps: S1. Clean and dry the FTO substrate, and treat the surface of the FTO substrate with ultraviolet-ozone for 5~20 min or plasma cleaning for 1~5 min; S2. After measuring deionized water and freezing it to form an ice-water mixture, urea, concentrated hydrochloric acid, mercaptoacetic acid and stannous dichloride dihydrate are slowly added to the ice-water mixture in sequence and stirred until completely dissolved to obtain a tin oxide precursor solution. S3. Weigh out the cerium salt and add it to the tin oxide precursor solution obtained in S2 to obtain a tin oxide precursor solution containing cerium salt. S4. The FTO substrate treated by S1 is immersed in the cerium salt-containing tin oxide precursor solution of S3 and deposited under constant temperature conditions by chemical bath method. After the deposition is completed, the substrate is taken out and subjected to ultrasonic cleaning, drying and annealing treatment in sequence to obtain the cerium-doped electron transport layer. In S2, the pH of the tin oxide precursor solution is 0.5~2.0, and the amounts of each component are 6.250~25.000 g / L of urea, 6.250~25.000 mL / L of concentrated hydrochloric acid, 125~500 μL / L of mercaptoacetic acid, and 1.375~5.500 g / L of stannous dichloride dihydrate. In S3, the cerium salt is one or more cerium salts selected from cerium chloride, cerium phosphate, cerium nitrate, and cerium acetate; the concentration ratio of cerium ions to tin ions in the cerium-containing tin oxide precursor solution is 1% to 10%. In S4, the deposition temperature is 80~100℃ and the reaction time is 1~5h; In S4, the ultrasonic cleaning solution is one of ethanol, isopropanol, ethylene glycol, and propylene glycol. The ultrasonic cleaning time is 2-10 min, the annealing temperature is 140-200℃, the annealing time is 30-90 min, and the thickness of the cerium-doped electron transport layer is 10-100 nm.

2. An application of a cerium-doped tin oxide electron transport layer, characterized in that: The cerium-doped tin oxide electron transport layer prepared by the method described in claim 1 is applied to a perovskite solar cell, characterized in that: its application in preparing an organic-inorganic hybrid upright perovskite solar cell with UV resistance includes the following steps: T1. Prepare a cerium-doped tin oxide electron transport layer on the surface of an FTO substrate and treat it with ultraviolet-ozone for 15 min or plasma cleaning for 3 min. T2. Prepare an APbX3 structured perovskite light-absorbing layer on the surface of a cerium-doped tin oxide electron transport layer, wherein A is one or more of ammonium methylamine, formamidinium, cesium ions, and potassium ions, and X is one or more of I, Br, and Cl. T3. A hole transport layer is prepared directly on the surface of a perovskite light-absorbing layer by spin coating. T4. An electrode layer is prepared on the surface of the hole transport layer by thermal evaporation or magnetron sputtering. The hole transport layer in T3 is made of 2,2',7,7'-tetra(4-methoxydiphenylamine)-9,9'-spirofluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], nickel oxide, copper thiocyanate, or copper iodide.

3. The application of the cerium-doped tin oxide electron transport layer according to claim 2, characterized in that: The electrode layer in T4 is one or more of gold, silver, copper, indium tin oxide, and aluminum-doped zinc oxide, and the thickness of the electrode is 50~300nm.

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