Double-layer electron transport layer, preparation method thereof and perovskite solar cell

Abstract

The application relates to the technical field of photovoltaic and semiconductor device manufacturing, and particularly provides a double-layer electron transport layer, a preparation method thereof and a perovskite solar cell. The double-layer electron transport layer comprises a tin dioxide layer and a stannous carboxylate layer with a structure shown in formula (I); wherein R is n-octyl or iso-octyl. The stannous carboxylate with the structure shown in formula (I) can form an n-type semiconductor, the energy level arrangement of the electron transport layer can be improved after the SnO2 is modified, the electron extraction can be faster, the recombination of the electrons at the interface can be reduced, the device performance can be improved, and the hysteresis phenomenon can be reduced.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic and semiconductor device manufacturing technology, specifically to a double-layer electron transport layer and its preparation method, and a perovskite solar cell. Background Technology

[0002] Currently, perovskite solar cell devices exhibit diverse configurations. From the working principle and basic structure of perovskite solar cells, it is clear that the electron transport layer (ETL) is one of the most critical functional layers, playing a crucial role in improving device efficiency and stability. In NIP-type perovskite solar cells, the electron transport layer is located between the transparent conductive glass and the perovskite light-absorbing layer. The primary optical requirement is excellent visible light transmittance. The light absorption cutoff wavelength of the light-absorbing layer material is generally in the 800–900 nm range, with stronger absorption of shorter wavelengths within the visible light spectrum. Therefore, from an optical perspective, to improve efficiency, the electron transport layer material needs strong transmittance in the visible light region and even higher transmittance in the shorter wavelength range of the visible light spectrum. This allows more photons to pass through the electron transport layer and be absorbed by the perovskite layer, thereby generating more photogenerated carriers and improving device performance. Furthermore, appropriate modifications to the morphology and roughness of the electron transport layer can produce an anti-reflection effect, enhancing the light intensity, increasing the light absorption of the light-absorbing layer, and increasing the short-circuit current density of the device, thus improving device performance. The electron transport layer plays a crucial role in electron extraction, collection, and transport, while simultaneously blocking photogenerated holes. Therefore, from an electrical perspective, the electron transport layer needs to meet two key conditions: First, the energy levels of the transport layer and the perovskite absorber layer must be compatible, with the transport layer's conduction band position slightly lower than that of the absorber layer to better drive electron injection. Its valence band position should be deeper than that of the absorber layer to effectively block photogenerated holes and reduce the probability of interfacial recombination. Second, the electron transport layer material needs to possess excellent electron mobility. A suitable energy level position enables charge extraction, but whether the extracted electrons can be successfully collected to the electrode depends on the electron mobility of the transport layer. High mobility results in low series resistance and a low probability of electron recombination, thereby improving the device's fill factor and efficiency. Furthermore, in NIP (non-in-line photovoltaic) solar cells, the electron transport layer also determines the growth of the upper perovskite film. How to promote the growth of the perovskite film and thus improve its quality is currently one of the key research areas regarding the electron transport layer and the perovskite interface.

[0003] SnO2 is the most commonly used electron transport layer in high-efficiency perovskite solar cells in recent years. The main factors determining the performance of the SnO2 electron transport layer are conductivity and energy level structure. As an n-type metal oxide semiconductor, SnO2 contains a large number of oxygen vacancies in its crystal. Theoretically, one oxygen vacancy can provide two electrons. Therefore, increasing the oxygen vacancy concentration can, to a certain extent, increase the carrier concentration in the SnO2 film, thereby increasing its conductivity. Another important factor affecting the conductivity of SnO2 is carrier mobility. When SnO2 films contain a large number of defects such as impurity ions, vacancies, grain boundaries, and dislocations, the carrier mobility inside the film will decrease, resulting in very low film conductivity. Furthermore, the concentration of defect states in the SnO2 film also affects the band structure of the material.

[0004] Charge accumulation at the perovskite-electron transport layer interface generates a sharp electric field that can promote or hinder charge transfer at the interface. When there is a band mismatch, charge extraction is suppressed, confining more charge within the perovskite layer and thus altering the accumulation of mobile charge and the distribution of the electric field. Furthermore, recombination at the perovskite-electron transport layer interface is also a significant factor affecting device performance. This trap-assisted recombination process is highly correlated with the quality of the interface, including the coverage of the electron transport layer, band structure, and trap density.

[0005] In summary, the current shortcomings of applying SnO2 electron transport layers in perovskite solar cells are as follows: (1) The commonly used preparation method of SnO2 electron transport layers requires high-temperature post-annealing, but post-annealing will result in a large number of defect states on the SnO2 surface, making it difficult to prepare high-efficiency perovskite solar cells. (2) Charge accumulation at the interface between perovskite and SnO2, and when the charge extraction and transport capabilities of SnO2 are mismatched, electrons or holes will accumulate at the interface, which will also have an adverse effect on the built-in electric field, leading to the generation of hysteresis effect. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects of low efficiency and severe hysteresis effect in the existing perovskite solar cells, thereby providing a double-layer electron transport layer, its preparation method and a perovskite solar cell.

[0007] This invention provides a double-layer electron transport layer comprising a tin dioxide layer and a tin carboxylate layer with the structure shown in formula (I);

[0008]

[0009] (I); where R is n-octyl or isooctyl.

[0010] Furthermore, the stannous carboxylate layer is a stannous isooctanoate layer.

[0011] Furthermore, the thickness ratio of the tin dioxide layer to the tin carboxylate layer is 1:1 to 1.2:1.

[0012] Furthermore, the thickness of the tin dioxide layer is 12-28 nm, preferably 14-18 nm.

[0013] Furthermore, the thickness of the tin carboxylate layer is 10-30 nm, preferably 15-18 nm.

[0014] The present invention also provides a method for preparing any of the above-described double-layer electron transport layers, comprising the following steps:

[0015] A tin dioxide layer was prepared by reactive plasma deposition, and a tin carboxylate layer was prepared on the tin dioxide layer by spin coating.

[0016] Furthermore, during the reactive plasma deposition process, tin dioxide particles are used as the target material, and the chamber pressure is evacuated to 7 × 10⁻⁶ before growth. -4 ~6×10 -4 Argon gas at 75–85 sccm and 28–32 sccm is introduced into the electron gun and chamber respectively as glow discharge gas. During deposition, the chamber pressure is maintained at 0.5–0.6 Pa, the deposition time is controlled at 40–90 s, the oxygen flux is controlled at 8–10 sccm, and the deposition power is controlled at 23 A–27 A. Preferably, the deposition time is controlled at 50–60 s.

[0017] Furthermore, in the process of preparing the stannous carboxylate layer, an anhydrous ethanol solution of stannous carboxylate is mixed with cyclohexane to obtain a mixed solution, and then the mixed solution is coated onto a tin dioxide layer by spin coating. After annealing, the stannous carboxylate layer is obtained. Preferably, the concentration of stannous carboxylate in the mixed solution is 2wt%-7wt%; preferably, the spin coating speed is 5000-6000 rpm; preferably, the annealing temperature is 150-180℃ and the time is 20-30 minutes.

[0018] The present invention also provides a perovskite solar cell, comprising any of the described double-layer electron transport layers or a double-layer electron transport layer prepared by any of the described methods, preferably further comprising a transparent conductive substrate, a perovskite light-absorbing layer, a perovskite passivation layer, a hole transport layer, and an electrode.

[0019] Furthermore, the transparent conductive substrate is selected from FTO conductive glass or ITO conductive glass; and / or, the perovskite light-absorbing layer is a perovskite thin film with a thickness of 500-800 nm; and / or, the perovskite passivation layer is selected from PEAI, MABr, or GuaBr; and / or, the hole transport layer is selected from Spiro-OMeTAD, PTAA, or NiO. Xor MoO X One or more of the following; and / or, the electrode is a gold electrode with a thickness of 80–120 nm.

[0020] The technical solution of this invention has the following advantages:

[0021] 1. The charge extraction and transport capabilities of RPD-SnO2 are insufficient, leading to a large accumulation of charge at the electron transport layer and perovskite interface. This negatively impacts the built-in electric field, resulting in relatively low device performance and hysteresis. The bilayer electron transport layer provided by this invention comprises a tin dioxide layer and a tin carboxylate layer with the structure shown in Formula (I). The tin carboxylate layer with the structure shown in Formula (I) can form an n-type semiconductor. Modifying SnO2 improves the energy level arrangement of the electron transport layer, enabling faster electron extraction, thereby reducing electron recombination at the interface, improving device performance, and mitigating hysteresis.

[0022] 2. The double-layer electron transport layer provided by the present invention, wherein the stannous carboxylate layer is a stannous isooctanoate (CSCO) layer, studies have found that combining CSCO and RPD-SnO2 can more effectively improve the charge extraction capability and transport speed, which is beneficial to obtaining higher open-circuit voltage and reducing the hysteresis effect of perovskite devices.

[0023] 3. The double-layer electron transport layer provided by the present invention, wherein the thickness ratio of the tin dioxide layer to the tin carboxylate layer is 1:1-1.2:1, not only further improves the electron transport layer's ability to extract charge carriers and the conductivity of the transport layer, but also shifts the energy band of SnO2 upward, increases the n-type properties of the thin film, which is beneficial for obtaining higher open-circuit voltage and reducing the hysteresis effect of perovskite solar cells, thereby further improving the accuracy of test results.

[0024] 4. The double-layer electron transport layer provided by the present invention has a tin dioxide layer with a thickness of 12-28 nm, preferably 14-18 nm; it not only has good transmittance in the visible light region, but also has good extraction and transport function for electrons, thereby further improving the accuracy of test results.

[0025] 5. The method for preparing a double-layer electron transport layer provided by the present invention uses reactive plasma deposition to prepare a tin dioxide layer. In particular, during the reactive plasma deposition process, tin dioxide particles are used as the target material, and the chamber pressure is evacuated to 7 × 10⁻⁶ before growth. -4 ~6×10 -4Argon gas at 75–85 sccm and 28–32 sccm is introduced into the electron gun and chamber respectively as glow discharge gases. During deposition, the chamber pressure is maintained at 0.5–0.6 Pa, the deposition time is controlled at 40–90 s, the oxygen flux is controlled at 8–10 sccm, and the deposition power is controlled at 23–27 A. Preferably, the deposition time is controlled at 50–60 s. This method not only yields dense SnO2 films but also ensures that the films possess good optical transmittance and electrical properties, which is beneficial for electron extraction and transport, further improving the accuracy of test results. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell based on CSCO and RPD-SnO2 according to a specific embodiment of the present invention;

[0028] Figure 2 This is a photoluminescence spectrum curve based on CSCO and RPD-SnO2 according to a specific embodiment of the present invention;

[0029] Figure 3 This is a dark-state JV characteristic curve based on CSCO and RPD-SnO2 according to a specific embodiment of the present invention;

[0030] Figure 4 The specific embodiments of the present invention are based on the CSCO and RPD-SnO2 thin film transmittance curves;

[0031] Figure 5 This is the JV curve of the RPD-SnO2-based perovskite solar cell prepared in Comparative Example 7 of this invention.

[0032] Figure 6 This is the JV curve of the CSCO-based perovskite solar cell prepared in Comparative Example 8 of this invention.

[0033] Figure 7 The JV curves of the RPD-SnO2 and CSCO double electron transport layer based perovskite solar cells prepared in Example 4 of this invention are shown.

[0034] Figure 8 The optimal JV curve for perovskite solar cells based on tin dioxide thin films of different thicknesses is shown.

[0035] Figure label:

[0036] 1. Metal electrode; 2. Hole transport layer; 3. Passivation layer; 4. Perovskite light-absorbing layer; 5. Stannous isooctanoate film; 6. Tin dioxide film; 7. Conductive substrate. Detailed Implementation

[0037] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0038] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0039] Example 1: Double-layer electron transport layer

[0040] This embodiment provides a double-layer electron transport layer and its preparation method, including the following steps:

[0041] 1. The area of ​​the ITO substrate is 2cm×2cm. The surface treatment sequence is: ultrasonic cleaning with deionized water and isopropanol, then drying with nitrogen gas, and finally ultraviolet ozone treatment for 20 minutes.

[0042] 2. Place the ITO and the crucible containing the SnO2 target in the reactive plasma deposition apparatus, and use a mechanical pump to evacuate the vacuum chamber to a medium vacuum state, and then use a molecular pump to evacuate the vacuum chamber to a high vacuum state.

[0043] 3. When the vacuum state reaches 6×10 -4 Argon gas at 80 sccm and 30 sccm was introduced into the electron gun and chamber respectively as glow gas. The chamber pressure was maintained at about 0.5 Pa. The deposition time was controlled at 60 s, the oxygen flux was 9 sccm, and the working current was 25 A to obtain a tin dioxide thin film.

[0044] 4. A mixed solution containing 4 wt% stannous isooctanoate was prepared by mixing an anhydrous ethanol solution of stannous isooctanoate and cyclohexane at a volume ratio of 8:2. Subsequently, the mixed solution was coated onto a tin dioxide film using a spin-coating method to prepare a stannous isooctanoate layer. The spin-coating speed was 6000 rpm for 30 s. Then, annealing was performed at a temperature of 150℃ for 30 minutes to obtain a double electron transport layer (abbreviated as RPD-SnO2+CSCO), in which the thickness of the tin dioxide layer was 17.85 nm and the thickness of the stannous isooctanoate layer was 17.50 nm.

[0045] Example 2: Double-layer electron transport layer and metal electrode

[0046] This embodiment provides a composite layer of a bilayer electron transport layer and a metal electrode, the preparation method of which includes the following steps:

[0047] A double electron transport layer was prepared according to the method in Example 1, and then an 80 nm thick metal electrode Au was deposited using a thermal evaporation method.

[0048] Example 3: Double-layer electron transport layer and perovskite light-absorbing layer

[0049] This embodiment provides a composite layer consisting of a bilayer electron transport layer and a perovskite light-absorbing layer, the preparation method of which includes the following steps:

[0050] A double electron transport layer was prepared according to the method in Example 1, and then the following operations were performed: (1) 691.5 mg of PbI2 was dissolved in N,N at a volume ratio of 9:1. In a mixed solvent of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), stir until completely dissolved;

[0051] (2) Dissolve 90 mg formamidin iodine (FAI), 6.39 mg methylamine iodine (MAI) and 9 mg methylamine chloride (MACl) in 1 mL of isopropanol solvent and stir until all the powder is dissolved;

[0052] (3) Take the PbI2 solution obtained in step (1) and coat it on the surface of the double electron transport layer. After rotating it at 1500 rpm for 30 seconds, remove it and anneal it at 70°C for 1 minute to obtain a PbI2 film.

[0053] (4) Take the organic salt solution obtained in step (2) and coat it on the surface of the PbI2 film obtained in step (3). Rotate it at 2000 rpm for 30 seconds and then remove it. Anneal it at 150°C for 15 minutes in an air environment with a humidity of 30% to 40% to obtain a composite layer of double electron transport layer and perovskite light absorption layer.

[0054] Example 4: Perovskite Solar Cell

[0055] This embodiment provides a perovskite solar cell and its fabrication method, such as... Figure 1 As shown, the structure includes, from bottom to top, a transparent conductive substrate 7, a tin dioxide thin film 6 prepared by RPD, a tin isooctanoate thin film 5, a perovskite light-absorbing layer 4, a passivation layer 3, a hole transport layer 2, and a metal electrode 1.

[0056] The preparation method includes preparing a composite layer of a bilayer electron transport layer and a perovskite light-absorbing layer according to the method in Example 3, and then performing the following operations:

[0057] (1) Dissolve 5 mg of PEAI in 1 mL of isopropanol solvent and stir until all the powder is dissolved;

[0058] (2) Take the solution obtained in step (1) and spin-coat it onto the surface of the perovskite composite layer of the double electron transport layer and the perovskite light-absorbing layer, and spin at a speed of 5000 rpm for 30s.

[0059] (3) Dissolve 260 mg Li-TFSI in 1 mL of acetonitrile solvent and stir until all the powder is dissolved; dissolve 72.3 mg Spiro-OMeTAD, 30 μL 4-tert-butylpyridine and 35 μL of the above Li salt in 1 mL of chlorobenzene solvent and stir until all the powder is dissolved.

[0060] (4) Take the solution obtained in step (3) and spin-coat it onto the passivated perovskite light absorption layer to form a film. The rotation speed is 3000 rpm and the time is 30 s.

[0061] (5) An 80 nm thick metal electrode Au was deposited using a thermal evaporation method.

[0062] Comparative Examples 1-2

[0063] Comparative Example 1 provides a single-layer electron transport layer and its preparation method, which includes only a tin dioxide (RPD-SnO2) thin film. The preparation method is basically the same as that of Example 1, except that step 4 is omitted.

[0064] Comparative Example 2 provides a single-layer electron transport layer and its preparation method, which only includes a stannous isooctanoate (CSCO) thin film. The preparation method is basically the same as that of Example 1, except that step 3 is omitted.

[0065] Comparative Examples 3-4

[0066] Comparative Example 3 provides a composite layer of a single-layer electron transport layer and a metal electrode. Its preparation method is basically the same as that of Example 2, except that the single-layer electron transport layer of Comparative Example 1 is used instead of the double-layer electron transport layer of Example 2.

[0067] Comparative Example 4 provides a composite layer of a single-layer electron transport layer and a metal electrode. Its preparation method is basically the same as that of Example 2, except that the single-layer electron transport layer of Comparative Example 2 is used instead of the double-layer electron transport layer of Example 2.

[0068] Comparative Examples 5-6

[0069] Comparative Example 5 provides a composite layer of a single-layer electron transport layer and a perovskite light-absorbing layer. Its preparation method is basically the same as that of Example 3, except that the single-layer electron transport layer of Comparative Example 1 is used instead of the double-layer electron transport layer of Example 3.

[0070] Comparative Example 6 provides a composite layer of a single-layer electron transport layer and a perovskite light-absorbing layer. Its preparation method is basically the same as that of Example 3, except that the single-layer electron transport layer of Comparative Example 2 is used instead of the double-layer electron transport layer of Example 3.

[0071] Comparative Examples 7-8

[0072] Comparative Example 7 provides an RPD-SnO2-based perovskite solar cell, which is prepared in a manner that is basically the same as that of Example 4, except that the single-layer electron transport layer of Comparative Example 1 is used instead of the double-layer electron transport layer of Example 4.

[0073] Comparative Example 8 provides a CSCO-based perovskite solar cell, which is prepared in a manner that is basically the same as that of Example 4, except that the single-layer electron transport layer of Comparative Example 2 is used instead of the double-layer electron transport layer of Example 4.

[0074] Experimental Example 1

[0075] Transmission spectroscopy tests were performed on the films obtained in Example 1 and Comparative Examples 1-2 using a Varian Cary 5000 UV-VIS spectrophotometer. The results are shown below. Figure 4 As shown.

[0076] In the visible light range, the optical transmittance of RPD-SnO2+CSCO first increases and then decreases compared to RPD-SnO2 and CSCO alone, indicating that the addition of CSCO does not cause significant optical loss.

[0077] Experimental Example 2

[0078] The conductivity of the thin films obtained in Example 2 and Comparative Examples 3-4 was tested using a solar simulator (CS-20, ASAHI SPECTRA Co., Ltd., Japan) under dark conditions. The device structure used in the tests was ITO / ETL / Au. The results are shown in [Figure number missing]. Figure 3 As shown.

[0079] Under dark conditions, the conductivity of the RPD-SnO2+CSCO film prepared in Example 2 was significantly higher than that of the CSCO and RPD-SnO2 films, indicating that the RPD-SnO2+CSCO film has better conductivity.

[0080] Experimental Example 3

[0081] Photoluminescence spectroscopy was performed on the thin films obtained in Example 3 and Comparative Examples 5-6 using an FLS980 instrument. The results are shown below. Figure 2 As shown.

[0082] The ITO / RPD-SnO2+CSCO / perovskite device prepared in Example 3 exhibited significant photoluminescence quenching and the lowest PL peak, indicating that the RPD-SnO2+CSCO film has a stronger electron extraction capability.

[0083] Experiment Example 4

[0084] The perovskite solar cells obtained in Example 4 and Comparative Examples 7-8 were subjected to IV testing using a solar simulator (CS-20, ASAHISPECTRA Co., Ltd., Japan) at AM 1.5G and 100mW / cm². 2 JV curves were obtained at room temperature. The scan initiation voltage was set from 1200mV to -200mV, and the battery was placed on a metal template to ensure an effective illumination area of ​​0.089cm². 2 The results are shown Figure 5-7 As shown.

[0085] like Figure 5 and 6 The JV curves are shown for RPD-SnO2-based and CSCO-based perovskite solar cells, respectively. The highest efficiency of the RPD-SnO2-based cell is 21.27%. SC 23.36 mA / cm 2 V OC The voltage was 1112 mV, and the FF was 81.85%; the best efficiency of 21.61% was achieved with a single-layer CSCO device and a Jsc of 23.21 mA / cm. 2 V OC The voltage was 1147 mV, and the FF was 81.13%.

[0086] Figure 7 The JV curves for RPD-SnO2+CSCO-based perovskite solar cells show a maximum efficiency of 22.15% and a Jsc of 23.91 mA / cm². 2 V OC With a voltage of 1147 mV and an electron filtration efficiency (FF) of 80.72%, it can be seen that the introduction of CSCO significantly increases the photoelectric conversion efficiency of the device. Furthermore, with RPD-SnO2+CSCO as the electron transport layer, the hysteresis of the JV curve is smaller. The device based on RPD-SnO2+CSCO exhibits a hysteresis coefficient of 3.69%, far lower than the hysteresis of the device based on RPD-SnO2 (24.04%).

[0087] Experimental Example 5: Thickness of SnO2 Thin Film

[0088] Perovskite solar cells were prepared according to Example 4, with the only difference being the glow time. The glow times were controlled at 40s, 50s, 60s, 70s, 80s, and 90s, respectively, yielding SnO2 films with average thicknesses of 12.43nm, 14.71nm, 17.91nm, 21.47nm, 24.26nm, and 27.82nm. The effect of different SnO2 film thicknesses on the performance of the perovskite solar cells was investigated.

[0089] See results Figure 8 As shown in the figure, the JV curve of the perovskite solar cell shows that the device performance is best when the average SnO2 thickness is 17.91 nm. This indicates that considering the optical properties, electrical properties and device performance of the SnO2 film in perovskite solar cells, 17.91 nm is the optimal thickness for the RPD-SnO2 film as an electron transport layer.

[0090] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A double-layer electron transport layer, characterized in that, It includes a tin dioxide layer and a tin carboxylate layer with the structure shown in formula (I); （I）； Wherein, R is n-octyl or isooctyl, the thickness ratio of the tin dioxide layer to the tin carboxylate layer is 1:1-1.2:1, the thickness of the tin dioxide layer is 14-18 nm, the thickness of the tin carboxylate layer is 15-18 nm, and the preparation method of the double-layer electron transport layer includes the following steps: Tin dioxide layers were prepared using reactive plasma deposition (RPD), and tin carboxylate layers were then prepared on top of the tin dioxide layers using spin coating. During RPD, tin dioxide particles were used as the target material, and the chamber pressure was evacuated to 7 × 10⁻⁶ before growth. -4 ~6×10 -4 Argon gas at 75-85 sccm and 28-32 sccm was introduced into the electron gun and chamber as glow discharge gases, respectively. During deposition, the chamber pressure was maintained at 0.5-0.6 Pa, the oxygen flux was controlled at 8-10 sccm, the deposition power was controlled at 23-27 A, and the deposition time was controlled at 50-60 s.

2. The double-layer electron transport layer according to claim 1, characterized in that, The stannous carboxylate layer is a stannous isooctanoate layer.

3. The double-layer electron transport layer according to claim 1, characterized in that, In the reactive plasma deposition process, tin dioxide particles are used as the target material, and the chamber pressure is evacuated to 7 × 10⁻⁶ before growth. -4 ~6×10 -4 Argon gas at 75-85 sccm and 28-32 sccm was introduced into the electron gun and chamber as glow discharge gases, respectively. During the deposition process, the chamber pressure was maintained at 0.5-0.6 Pa, the deposition time was controlled at 40-90 s, the oxygen flux was controlled at 8-10 sccm, and the deposition power was controlled at 23-27 A.

4. The double-layer electron transport layer according to claim 3, characterized in that, The deposition time was controlled to be 50 s to 60 s.

5. The double-layer electron transport layer according to claim 1, characterized in that, In the process of preparing the stannous carboxylate layer, an anhydrous ethanol solution of stannous carboxylate is mixed with cyclohexane to obtain a mixed solution, and then the mixed solution is coated onto a tin dioxide layer by spin coating. After annealing, the stannous carboxylate layer is obtained.

6. The double-layer electron transport layer according to claim 5, characterized in that, The concentration of stannous carboxylate in the mixed solution is 2 wt%-7 wt%.

7. The double-layer electron transport layer according to claim 5, characterized in that, The spin coating speed is 5000-6000 rpm.

8. The double-layer electron transport layer according to claim 5, characterized in that, The annealing temperature is 150-180℃, and the time is 20-30 minutes.

9. A perovskite solar cell, characterized in that, Includes the double-layer electron transport layer as described in any one of claims 1-8.

10. The perovskite solar cell according to claim 9, characterized in that, It also includes a transparent conductive substrate, a perovskite light-absorbing layer, a perovskite passivation layer, a hole transport layer, and electrodes.

11. The perovskite solar cell according to claim 10, characterized in that, The transparent conductive substrate is selected from FTO conductive glass or ITO conductive glass; and / or, the perovskite light-absorbing layer is a perovskite thin film with a thickness of 500~800 nm; and / or, the perovskite passivation layer is selected from PEAI, MABr or GuaBr; and / or, the hole transport layer is selected from Spiro-OMeTAD, PTAA, NiO X or MoO X One or more of the following; and / or, the electrode is a gold electrode with a thickness of 80~120 nm.

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