Preparation method of a vanadium oxide-tin oxide core-shell structure nanocrystal electron transport layer material and a perovskite solar cell

Abstract

The present invention provides a preparation method of a vanadium oxide-tin oxide core-shell structure nanocrystal electron transport layer material and a perovskite solar cell. The method includes: adding VO2 nanopowder and a surfactant into a water-alcohol mixed solution, and performing ultrasonic dispersion; then adding SnCl2 and an inorganic salt, stirring, and performing hydrothermal reaction to obtain a VO2@SnO2 core-shell structure nanocrystal electron transport layer material. This method can obtain VO2@SnO2 core-shell structure nanocrystals. As the electron transport layer of a perovskite solar cell, it can improve the photoelectric conversion efficiency of the solar cell; there are nanoscale decomposition structures on the surface of the core-shell structure nanocrystals, which can adsorb the chemical groups of the surfactant, achieving a surface passivation effect between the electrode and the perovskite layer, improving the electron transport efficiency, and increasing the service life of the solar cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite batteries, and particularly relates to a preparation method of a vanadium oxide-tin oxide core-shell structure nanocrystal electron transport layer material and a perovskite battery. Background Art

[0002] The charge transport layer has the function of reducing the energy level barriers between the perovskite and the electrodes, extracting and transporting the corresponding charges (blocking the opposite charges). Therefore, different interfacial gradings are the driving forces for carrier movement. Thus, the characteristics of the interfaces are very important for achieving good device performance because they directly affect carrier extraction / transport / recombination, etc.

[0003] Reasonably selecting the electron / hole transport layer materials is crucial for balancing electron-hole transport, as well as improving the photoelectric conversion efficiency, stability, and lifespan of the device, and reducing or even eliminating the hysteresis phenomenon. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a preparation method of a vanadium oxide-tin oxide core-shell structure nanocrystal electron transport layer material and a perovskite battery. The VO2@SnO2 core-shell structure nanocrystals are used as the electron transport layer of the perovskite battery, enabling the battery to have a high photoelectric conversion efficiency.

[0005] The present invention provides a preparation method of a VO2@SnO2 core-shell structure nanocrystal electron transport layer material, including the following steps:

[0006] Adding VO2 nanopowders and a surfactant into a water-alcohol mixed solution, and performing ultrasonic dispersion; then adding SnCl2 and an inorganic salt, stirring, and carrying out a hydrothermal reaction to obtain the VO2@SnO2 core-shell structure nanocrystal electron transport layer material.

[0007] In the present invention, the VO2 nanopowders are preferably prepared according to the following method:

[0008] Preparing a vanadium-containing precursor solution from a vanadium-containing material; then carrying out a hydrothermal reaction and washing to obtain VO2 nanopowders.

[0009] Specifically, the VO2 nanopowders are prepared according to the following method:

[0010] Dispersing VOSO4 powder in an aqueous solution to obtain a blue transparent solution, heating in a water bath, and dropping a hydrazine hydrate solution to obtain a light blue suspension;

[0011] Mixing the light blue suspension and a NaOH solution, washing the obtained precipitate to obtain a precursor, dispersing it and then carrying out a hydrothermal reaction, cooling and then washing, and drying to obtain VO2 nanopowders.

[0012] In the present invention, the vanadium-containing material is selected from VOSO4 powder.

[0013] In the present invention, the mass ratio of the VOSO4 powder to the volume of the hydrazine hydrate solution is (1.1 - 1.3) g : (0.28 - 0.32) mL, and the concentration of the hydrazine hydrate solution is 75 - 85 wt%. The hydrazine hydrate has a coupling effect.

[0014] In the present invention, the temperature of the hydrothermal reaction of the VOSO4 precursor is 250 - 270 °C, and the time is 20 - 26 h. In specific embodiments, the temperature of the hydrothermal reaction of the VOSO4 precursor is 250 °C or 260 °C.

[0015] In the present invention, the temperature of the hydrothermal reaction of the VO2 nanometer powder and SnCl2 is 140 - 160 °C, and the time is 5.5 - 6.5 h.

[0016] In the present invention, the surfactant is selected from PVP and / or CTAB.

[0017] In the present invention, the inorganic salt is sodium citrate dihydrate.

[0018] In the present invention, the volume ratio of water to alcohol in the water-alcohol mixed solution is (1:9) - (9:1); preferably 1:1;

[0019] The alcohol is selected from one or more of isopropanol, ethanol, and methanol.

[0020] The present invention provides a perovskite solar cell, including an N-i-P structured perovskite solar cell or a P-i-N structured perovskite solar cell;

[0021] The N-i-P structured perovskite solar cell includes a transparent conductive base layer, an electron transport layer, a perovskite absorption layer, a hole transport layer, and a counter electrode layer;

[0022] The P-i-N structured perovskite solar cell includes a transparent conductive base layer, a hole transport layer, a perovskite absorption layer, an electron transport layer, and a counter electrode layer;

[0023] The electron transport layer is prepared from a dispersion of the VO2@SnO2 core-shell structure nanocrystal electron transport layer material prepared by the preparation method described in the above technical solution.

[0024] Figure 1 It includes an N-i-P structured perovskite solar cell and a P-i-N structured perovskite solar cell.

[0025] In the present invention, the thickness of the electron transport layer is 3 - 5 nm.

[0026] In the present invention, the dispersion of the VO2@SnO2 core-shell structured nanocrystal electron transport layer material includes the VO2@SnO2 core-shell structured nanocrystal electron transport layer material, a solvent, and a surfactant. The solvent is selected from one or more of water, ethanol, and isopropanol; the surfactant is selected from PVP and / or CTAB. The mass ratio of the VO2@SnO2 core-shell structured nanocrystal electron transport layer material to the surfactant in the dispersion of the VO2@SnO2 core-shell structured nanocrystal electron transport layer material is preferably 1:0.01 to 1:0.5, more preferably 1:0.05 to 1:0.3.

[0027] In the present invention, the current density-voltage (JV) curves of the cells prepared in the PCE test examples and comparative examples are tested on a kethley 2400 system; test conditions: the simulated light intensity is 100 mW cm -2 (AM1.5G), the scanning rate is 0.1 V s -1 (step size is 0.02 V, time delay is 200 ms), the scanning range is 1.2 V to -0.2 V, and the power output of the xenon lamp is calibrated by a KG5 standard Si cell of the NERL (National Renewable Energy Laboratory) standard.

[0028] The morphology of the VO2@SnO2 core-shell structured nanocrystal electron transport layer material is tested using a transmission electron microscope.

[0029] The present invention provides a method for preparing a VO2@SnO2 core-shell structured nanocrystal electron transport layer material, which includes the following steps: adding VO2 nanopowder and a surfactant into a water-alcohol mixed solution, and ultrasonically dispersing; then adding SnCl2 and an inorganic salt, stirring, and performing a hydrothermal reaction to obtain the VO2@SnO2 core-shell structured nanocrystal electron transport layer material. This method can obtain VO2@SnO2 core-shell structured nanocrystals. As the electron transport layer of a perovskite solar cell, it can improve the photoelectric conversion efficiency of the cell; there are nano-decomposed structures on the surface of the core-shell structured nanocrystals, which can adsorb the chemical groups of the surfactant, play a surface passivation effect between the electrode and the perovskite layer, improve the electron transport efficiency, and increase the battery life.

[0030] To achieve excellent charge extraction / transfer effects, the metal oxide charge transport layer must have a good energy level matching with the perovskite light absorption layer: 1) The conduction band of the electron transport material is equivalent to or slightly lower than that of the perovskite material, and the valence band of the hole transport material is equivalent to or slightly higher than that of the perovskite material. Photo-generated electrons / holes can be smoothly extracted by the electron / hole transport layer, achieving the purpose of obtaining a high short-circuit current density (Jsc) in perovskite solar cells (PSCs); 2) The valence band of the electron transport material is much lower than that of the perovskite material, and the conduction band of the hole transport material is much higher than that of the perovskite material, blocking the injection of photo-generated holes / electrons into the electron / hole transport layer, thereby obtaining an increase in the fill factor (FF) of PSCs; 3) The charge transport layer should form a good Ohmic contact with the electrode material. At the same time, the energy level difference between the Fermi level of the electron transport layer and the Fermi level of the hole transport layer determines the open-circuit voltage (Voc) of PSCs to a certain extent. In addition, the high electron / hole mobility of the metal oxide thin film determines the rapid transport of carriers, preventing charge accumulation of carriers in the material and causing carrier recombination at the interface. Therefore, adopting strategies such as structural design or chemical modification to optimize the energy level matching between the charge transport layer and the perovskite absorption layer, improve Ohmic contact, and passivate interface defects can effectively improve the optoelectronic conversion characteristics of perovskite solar cell devices. Brief Description of the Drawings

[0031] Figure 1 Schematic structural diagram of the perovskite battery provided by the present invention;

[0032] Figure 2 Scanning electron micrograph of 1 prepared in Example 1 of the present invention;

[0033] Figure 3 Voltage-current density curve of the battery prepared in Example 1 of the present invention;

[0034] Figure 4 Test curve of the photoelectric conversion efficiency of Example 1 of the present invention;

[0035] Figure 5 Voltage-current density curve of the battery prepared in Example 2 of the present invention;

[0036] Figure 6 Voltage-current density curve of the battery prepared in Example 3 of the present invention. Detailed Description of the Invention

[0037] To further illustrate the present invention, the preparation method of a VO2@SnO2 core-shell structure nanocrystal electron transport layer material and a perovskite battery provided by the present invention will be described in detail below in conjunction with examples, but they cannot be understood as limiting the protection scope of the present invention.

[0038] Example 1

[0039] Weigh 1.16 g of VOSO4 powder and disperse it in 20 mL of deionized water. After continuous stirring for 10 min, a blue transparent solution is obtained. Place it in a water bath heated at 70 °C and continue stirring. Then, slowly add 0.3 mL of hydrazine hydrate solution (N2H4·H2O, 80 wt%) to the above solution, which gradually turns into a light blue suspension. Continue stirring for 15 min. After the suspension is stable, add an appropriate amount of 1 mol / L NaOH aqueous solution. Finally, wash the precipitate successively with deionized water, absolute ethanol, and acetone to obtain the precursor. Disperse the precursor in 30 mL of deionized water. After uniform dispersion, transfer it to a 50 mL high-pressure hydrothermal autoclave. Heat the high-pressure hydrothermal autoclave to 260 °C and keep it at a constant temperature for 24 h. After the reaction is completed, naturally cool it to room temperature. Wash the initial product 3 times with deionized water and dry it in a vacuum drying oven at 60 °C for 6 h to obtain VO2 nanometer powder.

[0040] Weigh 0.05 g of VO2 nanometer powder and 0.025 g of PVP and add them to 30 mL of a 1:1 isopropanol and deionized water solution. Ultrasonically disperse the above solution for 1 hour. Then, add 0.17 g of SnCl2 and 0.441 g of trisodium citrate dihydrate (Na3C6H5O7·2H2O) to the above solution and stir magnetically for 1 h. Transfer the above solution to a 50 mL hydrothermal autoclave, heat it to 150 °C, and keep it at a constant temperature for 6 h. After the hydrothermal autoclave cools to room temperature, wash the hydrothermal reaction product with deionized water and ethanol and dry it in a drying oven at 60 °C.

[0041] Weigh 10 mg of the above-mentioned dried VO2@SnO2 powder dispersion solution and 1 mg of PVP, add them to 1 ml of ethanol, and ultrasonically disperse for 3 h to obtain the precursor solution A of the electron transport layer;

[0042] Clean 1.5 * 1.5 cm indium tin oxide (ITO) (glass thickness 2 mm, ITO film thickness 150 nm) glass with ethanol, isopropanol (IPA), and acetone for 30 minutes each, and blow it dry with a nitrogen gun.

[0043] Take 40 μL of the precursor solution A and evenly spread it on the surface of the ITO conductive glass. The parameters of the spin coater are set as: rotation speed 4000 rpm, time 30 s; then place it on a hot plate at 120 °C for annealing for 30 min to obtain the electron transport layer film; samples with the SnO2 electron transport layer spin-coated in the same way are used as the control group to obtain perovskite films (400 nm) respectively.

[0044] Place the above-prepared electron transport layer film in an ultraviolet ozone cleaner (Shanghai Cairong Economic and Trade Development Co., Ltd., UV-O3 / 70N) for treatment for 15 min for subsequent spin coating use.

[0045] Weigh 600 mg of lead iodide (PbI₂) and dissolve it in 900 μL of N,N-dimethylformamide (DMF) and 100 mL of ethylene glycol (2-Me) solution. Heat and stir at 70 °C to dissolve it completely to obtain the PbI₂ precursor solution B. Dissolve 80 mg of formamidinium hydroiodide (FAI) and 8 mg of methylammonium chloride (MACl) in 1 mL of IPA solution, and stir to dissolve it completely to obtain the organic salt solution C.

[0046] Take 50 μL of solution B and spread it evenly on the surface of the annealed film above. The parameters of the spin coater are set as: speed 2500 rpm, time 30 s; then place it on a hot stage at 75 °C for 1 min to form a coating. Take 80 μL of solution C and spread it evenly on the surface of the coating formed after the prepared solution B. The parameters of the spin coater are set as speed 3000 rpm, time 30 s; then place it on a hot stage at 150 °C for annealing for 15 min to obtain a perovskite film (400 nm).

[0047] Weigh 260 mg of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and dissolve it in 1 mL of acetonitrile (CAN). After stirring well, obtain the Li-TFSI solution. Then weigh 80 mg of 2,2,7,7-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene (Spiro-MeOTAD) and dissolve it in 1 mL of chlorobenzene. Stir well until dissolved; then add 30 μL of 4-tert-butylpyridine (TBP) solution and 35 μL of Li-TFSI solution, and stir well to obtain the hole transport layer solution.

[0048] Take 50 μL of the hole transport layer solution and spread it evenly on the surface of the perovskite film above. The parameters of the spin coater are set as speed 3000 rpm, time 30 s, to obtain the hole transport layer (50 nm).

[0049] Transfer the hole transport layer to a thermal evaporation equipment. Start evaporating the electrode (Au) under the condition that the vacuum degree reaches 1×10 -5 Pa, with a thickness of 100 nm; then place it in an oxygen glove box and leave it overnight for oxidation to obtain the battery.

[0050] Table 1 Photovoltaic test results of the perovskite battery prepared in Example 1

[0051]

[0052] Example 2

[0053] Weigh 1.16 g of VOSO4 powder and disperse it in 20 mL of deionized water. After continuous stirring for 10 min, a blue transparent solution is obtained. Place it in a water bath heated at 70 °C and continue stirring. Then, slowly add 0.35 mL of hydrazine hydrate solution (N2H4·H2O, 80 wt%) to the above solution, which gradually turns into a light blue suspension. Continue stirring for 15 min. After the suspension stabilizes, add an appropriate amount of 1 mol / L NaOH aqueous solution. Finally, wash the precipitate with deionized water, absolute ethanol, and acetone in sequence to obtain the precursor. Disperse the precursor in 30 mL of deionized water. After uniform dispersion, transfer it to a 50 mL high-pressure hydrothermal reactor. Heat the high-pressure hydrothermal reactor to 250 °C and keep it at a constant temperature for 12 h. After the reaction is completed, naturally cool it to room temperature. Wash the initial product 3 times with deionized water, and dry it in a vacuum drying oven at 60 °C for 6 h to obtain VO2 nanometer powder.

[0054] Weigh 0.05 g of VO2 nanometer powder and 0.025 g of PVP and add them to 30 mL of a 1:1 isopropanol and deionized water solution. Ultrasonically disperse the above solution for 1 h. Then, add 0.17 g of SnCl2 and 0.441 g of trisodium citrate dihydrate (Na3C6H5O7·2H2O) to the above solution and stir magnetically for 1 h. Transfer the above solution to a 50 mL hydrothermal reactor, heat it to 150 °C, and keep it at a constant temperature for 6 h. After the hydrothermal reactor cools to room temperature, wash the hydrothermal reaction product with deionized water and ethanol, and dry it in a drying oven at 60 °C.

[0055] Weigh 10 mg of the above dried VO2@SnO2 powder and 1 mg of PVP, add them to 1 mL of ethanol, and ultrasonically disperse for 3 h to obtain the precursor solution A of the electron transport layer;

[0056] Weigh 600 mg of lead iodide (PbI2) and 6 mg of cesium iodide (CsI) and dissolve them in 900 μL of N,N-dimethylformamide (DMF) and 100 mL of dimethyl sulfoxide (DMSO) solution. Heat and stir at 70 °C to fully dissolve them to obtain the PbI2 precursor solution B. Dissolve 80 mg of formamidinium hydroiodide (FAI) and 8 mg of methylammonium chloride (MACl) in 1 mL of IPA solution and stir to fully dissolve them to obtain the organic salt solution C.

[0057] Take 50 μL of solution B and evenly spread it on the surface of the annealed film above. The parameters of the spin coater are set as follows: speed 2500 rpm, time 30 s; then place it on a hot stage at 75 °C for 1 min to form a coating. Take 80 μL of solution C and evenly spread it on the surface of the coating formed after the prepared solution B. The parameters of the spin coater are set as: speed 3000 rpm, time 30 s; then place it on a hot stage at 150 °C for annealing for 15 min to obtain a perovskite film (400 nm).

[0058] Weigh 260 mg of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and dissolve it in 1 mL of acetonitrile (CAN). After stirring well, a Li-TFSI solution is obtained. Then weigh 80 mg of 2,2,7,7-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene (Spiro-MeOTAD) and dissolve it in 1 mL of chlorobenzene. Stir well until it is dissolved; then add 30 μL of 4-tert-butylpyridine (TBP) solution and 35 μL of Li-TFSI solution. After stirring well, a hole transport layer solution is obtained.

[0059] Take 50 μL of the hole transport layer solution and evenly spread it on the surface of the above-mentioned perovskite thin film. The parameters of the spin coater are set as speed 3000 rpm and time 30 s to obtain a hole transport layer (50 nm).

[0060] Transfer the hole transport layer to a thermal evaporation device. When the vacuum reaches 1×10 -5 Pa, start evaporating the electrode (Au) with a thickness of 100 nm; then place it in an oxygen glove box and leave it overnight for oxidation to obtain a battery.

[0061] Table 2 Photovoltaic performance test results of the battery prepared in Example 2

[0062]

[0063] Example 3

[0064] Weigh 1.16 g of VOSO4 powder and disperse it in 20 mL of deionized water. After continuous stirring for 10 min, a blue transparent solution is obtained. Place it in a 70 °C water bath heating environment and continue stirring. Then slowly drip 0.3 mL of hydrazine hydrate solution (N2H4·H2O, 80 wt%) into the above solution, and it gradually becomes a light blue suspension. Continue stirring for 15 min. After the suspension is stable, add an appropriate amount of 1 mol / L NaOH aqueous solution. Finally, wash the precipitate with deionized water, absolute ethanol, and acetone in sequence to obtain a precursor. Disperse the precursor in 30 mL of deionized water. After dispersing evenly, transfer it to a 50 mL high-pressure hydrothermal autoclave. Heat the high-pressure hydrothermal autoclave to 260 °C and keep it at a constant temperature for 24 h. After the reaction is completed, let it cool naturally to room temperature. Wash the initial product with deionized water 3 times and place it in a vacuum drying oven at 60 °C for drying for 6 h to obtain VO2 nanometer powder;

[0065] Weigh 0.05 g of VO2 nanometer powder and 0.03 g of PVP, and add them to 30 mL of a 1:1 isopropanol and deionized water solution. Ultrasonically disperse the above solution for 1 hour, then add 0.17 g of SnCl2 and 0.441 g of sodium citrate dihydrate (Na3C6H5O7·2H2O) to the above solution, and stir magnetically for 1 h. Transfer the above solution to a 50 mL hydrothermal autoclave, heat it to 150 °C and keep it warm for 6 h; wait for the hydrothermal autoclave to cool to room temperature, wash the hydrothermal reaction product with deionized water and ethanol, and dry it in an oven at 60 °C.

[0066] Weigh 10 mg of the above dried VO2@SnO2 powder and 1 mg of PVP, add them to 1 ml of ethanol, and ultrasonically disperse for 3 h to obtain the electron transport layer precursor solution A;

[0067] Wash the 1*1 cm FTO thin film (glass thickness 2 mm, FTO film layer thickness 100 nm) glass with ethanol, isopropanol (IPA), and acetone for 30 minutes each, and blow it dry with a nitrogen gun. Sputter a dense NiO x thin film (thickness 20 nm, x≤1) on the surface of the FTO thin film glass by magnetron sputtering. The sputtering power is 80 W for 30 min. Treat the above sputtered thin film with oxygen plasma for 10 min at a power of 2 kW.

[0068] Weigh 600 mg of lead iodide (PbI2) and 6 mg of cesium iodide (CsI), dissolve them in 900 μL of N,N-dimethylformamide (DMF) and 100 μL of dimethyl sulfoxide (DMSO) solution, heat and stir at 70 °C to fully dissolve, and obtain the PbI2 precursor solution B. Dissolve 80 mg of formamidinium hydroiodide (FAI) and 8 mg of methylammonium chloride (MACl) in 1 mL of IPA solution, and stir to fully dissolve to obtain the organic salt solution C.

[0069] Take 40 μL of solution B and evenly spread it on the surface of the above dried hole transport layer thin film. The parameters of the spin coater are set as: speed 2000 rpm, time 30 s; then place it on a hot stage at 75 °C for 1 min to form a coating. Take 70 μL of solution C and evenly spread it on the surface of the coating formed after coating solution B. The parameters of the spin coater are set as: speed 3000 rpm, time 30 s; then transfer the above device to a hot stage at 150 °C for annealing for 15 min.

[0070] Take 50 μL of solution A and evenly spread it on the surface of the above perovskite thin film. The parameters of the spin coater are set as: speed 2500 rpm, time 30 s; then place it on a heating stage at 120 °C and dry it for 15 min.

[0071] Transfer the device with the spin-coated electron transport layer to a thermal evaporation equipment, and the vacuum degree reaches 1×10 -5Under the condition of [[Pa]], the electrode (Au) was deposited by evaporation with a thickness of 100 nm to obtain the battery.

[0072] Table 3 Photovoltaic performance test results of the battery prepared in Example 3

[0073]

[0074] As can be seen from the above examples, the present invention provides a preparation method of a VO2@SnO2 core-shell structure nanocrystal electron transport layer material, which includes the following steps: adding VO2 nanopowder and a surfactant into a water-alcohol mixed solution, and ultrasonically dispersing; then adding SnCl2 and an inorganic salt, stirring, and performing a hydrothermal reaction to obtain VO2@SnO2 core-shell structure nanocrystals. This method can obtain a VO2@SnO2 core-shell structure nanocrystal electron transport layer material, which, as the electron transport layer of a perovskite battery, can improve the photoelectric conversion efficiency of the battery; can also passivate the interface; improve the electron transport efficiency; and increase the battery life.

[0075] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a VO2@SnO2 core-shell structure nanocrystal electron transport layer material, comprising the following steps: Weigh 1.16 g of VOSO4 powder and disperse it in 20 mL of deionized water. After continuous stirring for 10 min, a blue transparent solution is obtained. Place it in a water bath at 70 °C and heat it with continuous stirring. Then, add 0.3 mL of 80 wt% hydrazine hydrate solution N2H4·H2O to the above solution, and it gradually becomes a light blue suspension. Continue stirring for 15 min. After the suspension is stable, add 1 mol / L NaOH aqueous solution. Finally, wash the precipitate with deionized water, absolute ethanol, and acetone in sequence to obtain the precursor. Disperse the precursor in 30 mL of deionized water. After uniform dispersion, transfer it to a high-pressure hydrothermal reactor. Heat it to 260 °C and keep it at a constant temperature for 24 h. After the reaction is completed, cool it naturally to room temperature. Wash the initial product with deionized water and dry it to obtain VO2 nanometer powder. Weigh 0.05 g of VO2 nanometer powder and 0.025 g of PVP and add them to 30 mL of a 1:1 isopropanol and deionized water solution. Ultrasonically disperse the above solution for 1 hour. Then, add 0.17 g of SnCl2 and 0.441 g of sodium citrate dihydrate to the above solution and stir magnetically for 1 h. Transfer the above solution to a 50 mL hydrothermal reactor, heat it to 150 °C, and keep it warm for 6 h. After the hydrothermal reactor cools to room temperature, wash the hydrothermal reaction product with deionized water and ethanol, and dry it to obtain the VO2@SnO2 core-shell structure nanocrystal electron transport layer material.

2. A perovskite solar cell, including an N-i-P structured perovskite solar cell or a P-i-N structured perovskite solar cell; The N-i-P structured perovskite solar cell includes a transparent conductive base layer, an electron transport layer, a perovskite absorption layer, a hole transport layer, and a counter electrode layer; The P-i-N structured perovskite solar cell includes a transparent conductive base layer, a hole transport layer, a perovskite absorption layer, an electron transport layer, and a counter electrode layer; The electron transport layer is prepared from a dispersion of the VO2@SnO2 core-shell structure nanocrystal electron transport layer material prepared by the preparation method described in claim 1.

3. The perovskite cell according to claim 2, wherein, The thickness of the electron transport layer is 3 - 5 nm.

4. The perovskite cell according to claim 2, wherein The dispersion of the VO2@SnO2 core-shell structure nanocrystal electron transport layer material includes the VO2@SnO2 core-shell structure nanocrystal electron transport layer material, a solvent, and a surfactant.

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