A method for preparing SnO2 thin film in iodine vapor environment and application

Abstract

The application discloses a method for preparing SnO2 thin film in iodine vapor environment and application thereof, and belongs to the technical field of battery device preparation. The preparation method comprises the following steps: (1) dissolving SnCl2 in isopropyl alcohol and stirring in air to obtain a SnO2 precursor solution; (2) performing ultraviolet ozone treatment on a substrate, and rotating and coating the SnCl2 precursor solution on the obtained substrate; after the spin coating, the substrate is placed in a closed iodine vapor environment for standing, and heating annealing treatment is performed to obtain the SnO2 thin film. On the basis of the solution preparation method, the SnO2 thin film is innovatively obtained by using iodine vapor oxidation and low-temperature heating, the method for preparing the SnO2 thin film is simple, and the preparation cost is relatively low; the prepared perovskite thin film will not be decomposed, the service life of the device can be prolonged on the basis that the efficiency of the perovskite battery device is kept close to the initial performance of the control group.

Description

Technical Field

[0001] This invention relates to the field of battery device fabrication technology, specifically to a method and application for preparing SnO2 thin films in an iodine vapor environment. Background Technology

[0002] The electron transport layer is the core functional layer of perovskite solar cells (PSCs), playing a crucial role in improving the cell's photoelectric conversion performance. Tin dioxide (SnO2), a semiconductor oxide, possesses both excellent conductivity and optical transparency, making it a commonly used material for the electron transport layer of current perovskite solar cells.

[0003] Traditional SnO2 thin film fabrication techniques mainly include spray pyrolysis, sol-gel method, atomic layer deposition (ALD), electron beam evaporation, electrochemical deposition, chemical bath deposition, and solution methods. In spray pyrolysis, a series of influencing factors such as spray pressure, temperature, and flow rate are difficult to control precisely, and the high temperature can cause ablation of the film, resulting in defects. ALD and electron beam evaporation require high vacuum environments and precise gas control systems, leading to high fabrication costs. Electrochemical deposition has a slow deposition rate and is easily affected by control conditions, potentially causing difficulties in controlling film quality and thickness, thus impacting device efficiency. Solution methods have received widespread attention due to their simplicity and low cost; however, most SnO2 films prepared using solution methods currently require high-temperature annealing (>150°C) in oxygen or air. In inverted perovskite solar cells, the electron transport layer is fabricated after the perovskite thin film is prepared. Oxygen or air environments can cause the perovskite thin film to oxidize and decompose, and heating in an environment >150°C further leads to thermal decomposition of the perovskite thin film. Therefore, there is an urgent need to explore a method for preparing a SnO2 thin film electron transport layer in an inverted perovskite solar cell. Summary of the Invention

[0004] To address the above technical problems, this invention provides a method and application for preparing SnO2 thin films in an iodine vapor environment. Based on solution preparation methods, this invention innovatively utilizes iodine vapor oxidation at low temperature to obtain SnO2 thin films. This method for preparing SnO2 thin films is simple and has low preparation costs. It not only avoids decomposing the prepared perovskite thin film but also extends the device's lifespan while maintaining the efficiency of the perovskite solar cell device close to the initial performance of the control group. This invention uses a SnCl2 solution as a precursor, first forming a precursor layer on the substrate surface, then inducing the precursor to oxidize in an iodine vapor environment, followed by heat treatment to form the SnO2 thin film.

[0005] The first objective of this invention is to provide a method for preparing SnO2 thin films in an iodine vapor environment, comprising the following steps:

[0006] (1) Dissolve SnCl2 in isopropanol and stir in air to obtain SnO2 precursor solution;

[0007] (2) The substrate is subjected to ultraviolet ozone treatment, and the SnCl2 precursor solution is spin-coated on the obtained substrate; after spin coating, the substrate is placed in a closed iodine vapor environment and left to stand, and then heated and annealed to obtain the SnO2 film.

[0008] In this invention, in step (1), the concentration of the SnO2 precursor solution is 0.5 mg / mL to 5 mg / mL.

[0009] In this invention, in step (1), the stirring temperature is 25℃~30℃; the stirring time is 30min~1h.

[0010] In this invention, in step (2), the substrate is selected from ITO glass or silicon wafer.

[0011] In this invention, in step (2), the ultraviolet ozone treatment time is 20 min to 1 h.

[0012] In this invention, in step (2), the rotational speed of the spin coating is 2000 rpm to 4000 rpm, and the time is 30 s to 40 s.

[0013] In this invention, in step (2), the iodine vapor environment is formed by placing iodine particles in a sealed cavity, and the iodine particles sublimate at room temperature to form a sealed iodine vapor environment.

[0014] In this invention, in step (2), the settling time is 30 min to 1 h.

[0015] In this invention, in step (2), the temperature of the heating annealing treatment is 100℃~150℃, and the heating annealing treatment time is 15min~20min.

[0016] The second objective of this invention is to provide a method for fabricating a perovskite solar cell device based on an electron transport layer SnO2 thin film, comprising sequentially depositing a PEDOT:PSS thin film layer, a perovskite active layer, a PCBM layer, a SnO2 electron transport layer, and an electrode evaporation layer on a substrate surface, wherein the SnO2 electron transport layer is prepared by the method described in the first objective.

[0017] The beneficial effects of this invention are:

[0018] Compared to the commonly used inverted ITO / PEDOT:PSS / CH3NH3PbI3 / PCBM / BCP / Ag structure as a reference device, the SnO2 electron transport layer prepared by the present invention in an iodine vapor environment can significantly improve the stability and lifespan of perovskite solar cell devices while ensuring that the initial photoelectric performance of the device is basically acceptable. The battery device retained 92% of its initial efficiency after being placed under environmental conditions (relative temperature = 25±5℃) for 60 days. The preparation method proposed in this invention is relatively simple, and the obtained SnO2 film can be effectively applied to the electron transport layer of inverted perovskite solar cells, providing favorable support for improving the long-term operational stability of the device.

[0019] This invention employs an iodine vapor environment to treat the SnCl2 precursor, unlike traditional methods that use oxygen or air to heat and oxidize the SnO2 film. This method promotes the conversion of the precursor to SnO2 under milder conditions. Since the SnO2 electron transport layer in inverted perovskite solar cells is located above the functional layer, heating and oxidation in oxygen or air can easily adversely affect the underlying perovskite layer and organic functional layer, thus impacting device performance and stability. The iodine vapor treatment in this invention reduces damage to the underlying functional layer. Furthermore, SnO2, as an inorganic electron transport layer, exhibits superior chemical stability compared to commonly used organic interface layers. Therefore, the SnO2 film prepared using this method not only ensures good initial device performance but also significantly slows down device degradation, improving long-term stability and lifespan. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0021] Figure 1 This is the preparation process of the SnO2 thin film in Example 1 of the present invention.

[0022] Figure 2 This is a comparison chart of the device efficiency and lifetime of the perovskite solar cells obtained in Example 1 and the comparative example of the present invention.

[0023] Figure 3 This is the infrared absorption spectrum of the SnO2 thin film obtained in Example 1. Detailed Implementation

[0024] To address the technical problems identified in the background section, the present invention is implemented through the following solution:

[0025] This invention provides a method for preparing SnO2 thin films in an iodine vapor environment, comprising the following steps:

[0026] (1) Dissolve SnCl2 in isopropanol and stir in air to obtain SnO2 precursor solution;

[0027] (2) The substrate is subjected to ultraviolet ozone treatment, and the SnCl2 precursor solution is spin-coated on the obtained substrate; after spin coating, the substrate is placed in an iodine vapor environment and heated for annealing to obtain the SnO2 film.

[0028] In some embodiments of the present invention, in step (1), the concentration of the SnO2 precursor solution is 0.5 mg / mL to 5 mg / mL. Exemplarily, it can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mg / mL, or any range between any two values. In the present invention, if the precursor concentration is too high, particulate matter will form in the resulting SnO2 film, resulting in poor film formation; if the concentration is too low, the SnO2 film will be too thin to provide good protection for the underlying film, affecting its lifespan.

[0029] In some embodiments of the present invention, in step (1), the stirring temperature is 25°C to 30°C and the stirring time is 30 min to 1 h.

[0030] In some embodiments of the present invention, in step (2), the substrate is selected from ITO glass or silicon wafer.

[0031] In some embodiments of the present invention, in step (2), the ultraviolet ozone treatment time is 20 min to 1 h.

[0032] In some embodiments of the present invention, in step (2), the rotational speed of the spin coating is 2000 rpm to 4000 rpm and the time is 30 s to 40 s.

[0033] In some embodiments of the present invention, in step (2), the iodine vapor environment is formed by placing iodine particles in a sealed cavity, where the iodine particles sublimate at room temperature to form a sealed iodine vapor environment. The present invention utilizes iodine vapor to... 2+ Oxidized to Sn 4+ Combined with heating and annealing, a uniform SnO2 film was finally obtained.

[0034] In some embodiments of the present invention, in step (2), the settling time is 30 min to 1 h. Too short a settling time may lead to incomplete reaction; more than 1 h will increase costs. Therefore, a settling time of 30 min is preferred.

[0035] In some embodiments of the present invention, in step (2), the temperature of the heating annealing treatment is 100℃~150℃, and the heating annealing treatment time is 15min~20min.

[0036] The present invention also provides a method for fabricating a perovskite solar cell device based on an electron transport layer SnO2 thin film, comprising sequentially depositing a PEDOT:PSS thin film layer, a perovskite active layer, a PCBM layer, a SnO2 electron transport layer, and an electrode evaporation on a substrate surface, wherein the SnO2 electron transport layer is prepared by the method described in the first objective.

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0038] Example 1

[0039] This embodiment provides a method for fabricating a perovskite solar cell, as detailed below:

[0040] I. The method for preparing SnO2 thin films in an iodine vapor environment is as follows:

[0041] (1) Preparation of SnO2 precursor solution: Dissolve SnCl2 in isopropanol at a concentration ratio of 1 mg / mL to form SnCl2 isopropanol solution. Stir at room temperature for 30 min in air to obtain SnO2 precursor solution with a concentration ratio of 1 mg / mL.

[0042] (2) SnO2 thin film preparation process: First, a clean ITO glass substrate was subjected to ultraviolet ozone treatment for 20 min. Then, a SnCl2 precursor solution was spin-coated onto the treated substrate at 2000 rpm for 30 s. After spin-coating, the substrate was placed in a glove box iodine vapor environment (5 g of iodine particles were placed in the chamber, and the iodine particles would sublimate at room temperature to form a closed iodine vapor environment), and after standing for 30 min, it was annealed in the glove box at 100℃ for 15 min to form a SnO2 thin film. The structure of the obtained SnO2 thin film was characterized, and the results are shown in the figure. Figure 3 ,Depend on Figure 3 Infrared spectral characterization results show that the obtained film has a wavelength of approximately 545 cm⁻¹. -1 and 640 cm -1 The presence of characteristic absorption peaks at these locations corresponds to the angular vibration of O-Sn-O and the stretching vibration of Sn-O, respectively, indicating the formation of distinct Sn-O bonds in the sample. These results demonstrate that the precursor has undergone transformation after treatment using the method of this invention, and the resulting film matches the characteristic peaks of SnO2.

[0043] II. Fabrication of perovskite solar cell devices based on SnO2 thin films with electron transport layers:

[0044] Device structure: Indium tin oxide (ITO) / PEDOT:PSS / CH3NH3PbI3 / PCBM / SnO2 / Ag.

[0045] (1) Cleaning and pretreatment: Clean ITO is treated with ultraviolet ozone for 20 minutes to remove residual impurities on the surface and activate the surface.

[0046] (2) Preparation of PEDOT:PSS thin film: After filtering the PEDOT:PSS solution through a filter membrane, spin-coat it onto the surface of the pretreated ITO substrate at a speed of 4000 rpm for 40 s. Then place it in an air atmosphere and anneal at 100°C for 15 min. Cool it to room temperature for later use.

[0047] (3) Preparation of perovskite active layer: The ITO substrate cooled in step (2) was transferred to a nitrogen glove box, and a perovskite film was prepared by a two-step spin coating method: First, the perovskite precursor solution was spin coated at 1500 rpm for 20 s, and then the speed was increased to 4000 rpm and spin coated for another 40 s; when there were 20 s left in the spin coating process, 180 μL of chlorobenzene solvent was uniformly added to the surface of the substrate; after spin coating, the substrate was placed in a glove box and annealed at 110 °C for 10 min to obtain a dense perovskite film. The perovskite precursor solution was prepared by the following method: 470.9 mg of PbI2 and 162.4 mg of methyl iodide (CH3NH3I) were weighed and dissolved in 1 ml of a mixed solution of γ-butyrolactone and dimethyl sulfoxide. The volume ratio of butyrolactone to dimethyl sulfoxide solution was 7:3. Then the prepared solution was heated and stirred at 60 °C for 24 h on a heating stage in a nitrogen-filled glove box.

[0048] (4) PCBM layer deposition: PCBM chlorobenzene solution (20 mg / mL) was spin-coated onto the surface of the perovskite film at 1500 rpm for 30 s, and then annealed at 100 °C for 5 min to obtain the PCBM deposition layer.

[0049] (5) Preparation of SnO2 electron transport layer: 1.0 mg / mL SnCl2 precursor solution was spin-coated onto the surface of PCBM deposition layer at 2000 rpm for 30 s; after spin-coating, the substrate was placed in the iodine vapor atmosphere in the glove box and left to stand for 30 min; then annealed at 100 °C for 15 min in the glove box atmosphere to form SnO2 electron transport layer.

[0050] (6) Electrode evaporation: The substrate prepared in step (5) is transferred to an evaporation coating apparatus and coated under high vacuum conditions (vacuum degree 8×10). -4 A silver electrode with a thickness of 100 nm was deposited by vapor deposition to complete the fabrication of indium tin oxide (ITO) / PEDOT:PSS / CH3NH3PbI3 / PCBM / SnO2 / Ag (PEDOT:PSS-SnO2) devices.

[0051] Example 2

[0052] This embodiment is similar to Embodiment 1, except that in step (1), the concentration of the SnCl2 precursor solution is 0.5 mg / mL.

[0053] Example 3

[0054] This embodiment is similar to Embodiment 1, except that in step (1), the concentration of the SnCl2 precursor solution is 5 mg / mL.

[0055] Comparative Example 1

[0056] This comparative example provides an ITO / PEDOT:PSS / CH3NH3PbI3 / PCBM / Ag device (PEDOT:PSS), which is prepared in a similar manner to Example 1. The difference is that step (5) in the second part is missing, i.e., the SnO2 electron transport layer is not formed.

[0057] Comparative Example 2

[0058] This comparative example provides an ITO / PEDOT:PSS / CH3NH3PbI3 / PCBM / BCP / Ag device (PEDOT:PSS-BCP), prepared using a method similar to that of Example 1, with the difference being: in step (5) of the second part, the preparation of the BCP electron transport layer: the BCP solution is spin-coated onto the PCBM surface at 2000 rpm without annealing. Other steps are identical to those in Example 1. Specifically, the preparation method of the BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) solution is as follows: 2 mg of BCP powder is dissolved in 1 ml of anhydrous ethanol solution and stirred at room temperature until completely dissolved.

[0059] Performance testing

[0060] The efficiency and lifespan performance of the perovskite solar cell device obtained in Example 1, and the devices obtained in Comparative Examples 1 and 2, are tested as follows:

[0061] During efficiency testing, the device was not packaged; it was removed from the glove box and measured in air (measurement time 5 minutes) (temperature 20℃, humidity 70%). Experimental results are shown below. Figure 3 ,Depend on Figure 3As shown in Figure A, the solar cell device without an electron transport layer (Comparative Example 1) exhibits lower overall performance. Its short-circuit current density, open-circuit voltage, and fill factor are significantly weaker than the other two groups. This indicates that without an effective electron transport layer, electron extraction and transport within the device are limited, thus affecting overall output performance. In contrast, the JV curves of the devices significantly improved after introducing BCP (Comparative Example 2) or SnO2 (Example 1) electron transport layers, demonstrating that both materials effectively promote electron extraction and transport. Furthermore, the initial performance of the SnO2 group and the BCP group is relatively similar, indicating that the SnO2 thin film prepared using the method of this invention already possesses good application performance as an electron transport layer.

[0062] During the stability study of the device, it was not encapsulated and was stored in a nitrogen glove box. The device was removed from the glove box on days 1, 10, 30, and 60 and measured in air (each measurement took 5 minutes). The experimental results are shown below. Figure 3 ,Depend on Figure 3 As shown in Figure B, after 60 days, the device obtained in Example 1 based on PEDOT:PSS-SnO2 thin film still retains more than 90% of its efficiency, while the device obtained in Comparative Document 2 based on PEDOT:PSS-BCP has reduced its efficiency to about 30% of its original value. Therefore, the stability of SnO2 thin film devices based on 10 min of treatment is greatly improved.

[0063] The embodiments described above are merely preferred embodiments for fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for preparing SnO2 thin films in an iodine vapor environment, characterized in that, Includes the following steps: (1) Dissolve SnCl2 in isopropanol and stir in air to obtain SnO2 precursor solution; (2) The substrate is subjected to ultraviolet ozone treatment, and the SnCl2 precursor solution is spin-coated on the obtained substrate; after spin coating, the substrate is placed in a closed iodine vapor environment and left to stand, and then heated and annealed to obtain the SnO2 film.

2. The method according to claim 1, characterized in that, In step (1), the concentration of the SnO2 precursor solution is 0.5 mg / mL to 5 mg / mL.

3. The method according to claim 1, characterized in that, In step (1), the stirring temperature is 25℃~30℃; the stirring time is 30min~1h.

4. The method according to claim 1, characterized in that, In step (2), the substrate is selected from ITO glass or silicon wafer.

5. The method according to claim 1, characterized in that, In step (2), the ultraviolet ozone treatment time is 20 min to 1 h.

6. The method according to claim 1, characterized in that, In step (2), the rotational speed of the spin coating is 2000 rpm to 4000 rpm, and the time is 30 s to 40 s.

7. The method according to claim 1, characterized in that, In step (2), the iodine vapor environment is formed by placing iodine in a sealed cavity, where the iodine sublimates at room temperature.

8. The method according to claim 1, characterized in that, In step (2), the settling time is 30 min to 1 h.

9. The method according to claim 1, characterized in that, In step (2), the temperature of the heating annealing treatment is 100℃~150℃, and the heating annealing treatment time is 15min~20min.

10. A method for fabricating a perovskite solar cell device based on an electron transport layer SnO2 thin film, characterized in that, The method includes sequentially preparing a PEDOT:PSS thin film layer, a perovskite active layer, a PCBM layer deposition, a SnO2 electron transport layer, and an electrode evaporation on a substrate surface, wherein the SnO2 electron transport layer is prepared by the method described in any one of claims 1 to 9.

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