Method for preparing SnO2 electron transport layer for CZTSSe solar cell based on sol-gel method
By preparing a SnO2 electron transport layer using the sol-gel method, the problem of high interface defect density in CZTSSe solar cells was solved, the device efficiency was improved, the operation process was simplified, and efficient photoelectric conversion was achieved.
Patent Information
- Application Number
- CN202511250489.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-03
- Publication Date
- 2025-11-25
AI Technical Summary
Existing CZTSSe solar cells suffer from severe bulk and interfacial nonradiative recombination problems, resulting in device efficiency far below the theoretical limit. This is mainly due to the high defect density at the interface between the CZTSSe/CdS layer and the electron transport layer, leading to severe carrier loss.
SnO2 electron transport layers were prepared by sol-gel method. Dense SnO2 films were formed by spin-coating and annealing on CZTSSe/CdS films, replacing ZnO films prepared by traditional magnetron sputtering, in order to reduce interface defects and improve interlayer contact.
It effectively reduces the number of defects between the CZTSSe/CdS layer and the electron transport layer, improves carrier extraction efficiency, reduces energy loss, simplifies the operation process, and reduces costs.
Smart Images
Figure CN121013471A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thin-film solar cells and their preparation methods, specifically a method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method. Background Technology
[0002] In recent years, with increasing attention paid to environmental and energy depletion issues, the solar cell industry has seen a promising future. Thin-film solar cells, in particular, have attracted widespread attention due to their advantages such as low material consumption and flexibility. Among these, CZTSSe cells utilize abundant Cu, Zn, Sn, and S / Se elements found in the Earth's crust and possess an optical bandgap (1.0–1.5 eV) and a high light absorption coefficient (>10⁻¹⁰) similar to CIGS. 4 cm -1 CZTSSe solar cells are considered one of the most promising alternative technologies. However, existing CZTSSe cells still suffer from severe bulk and interfacial nonradiative recombination problems, resulting in device efficiencies far below the theoretical limit. Therefore, reducing the defect density at the interface and minimizing carrier nonradiative recombination at the interface are key to improving the efficiency of CZTSSe solar cells.
[0003] The structure of a CZTSSe solar cell generally includes Mo / CZTSSe / CdS / ZnO / ITO / Al. The ZnO layer, serving as the electron transport layer, is typically fabricated using magnetron sputtering. However, the magnetron sputtering process subjects the CZTSSe / CdS layer to continuous bombardment by high-energy particles, leading to defects such as lattice distortion. As a crucial site for carrier transport, the presence of more defects at the interface between the CZTSSe / CdS layer and the electron transport layer further increases carrier loss at this interface. Therefore, reducing the number of defects at this interface is key to further improving the efficiency of CZTSSe cells.
[0004] In this invention, a dense SnO2 film is obtained by spin-coating and annealing a CZTSSe / CdS film using the sol-gel method, replacing the traditional ZnO film prepared by magnetron sputtering as the electron transport layer. The thickness of the SnO2 film is determined by the concentration of the nano-dispersion. The sol-gel method for preparing the electron transport layer not only avoids lattice distortion caused by high-energy particle bombardment of the CZTSSe / CdS region, but also helps to fill the gaps between the CdS layer and the electron transport layer, improves interlayer contact, and reduces non-radiative convergence at the interface. Furthermore, the sol-gel method is simpler to operate and requires less equipment than sputtering. In addition, the SnO2 electron transport layer has good energy level matching with the CZTSSe / CdS and ITO layers, which can reduce electron energy loss and thus improve the photoelectric conversion efficiency of the device. Summary of the Invention
[0005] The novelty of this invention lies in the use of a sol-gel method to prepare SnO2 material for the electron transport layer of CZTSSe thin-film batteries, thereby reducing the number of defects between the CZTSSe / CdS layer and the electron transport layer, reducing carrier loss, and simplifying the operation.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] Step 1: Clean the magnetic balls, reagent bottles, battery boxes, and ceramic boats used in the experiment by ultrasonic cleaning with deionized water, isopropanol, and anhydrous ethanol, respectively, for 15-20 minutes each, repeating 2-3 times. After ultrasonic cleaning, place them in a drying oven to dry. After drying, seal the reagent bottles, battery boxes, and ceramic boats with sealing film to prepare for the next step.
[0008] Step 2: Weigh an appropriate amount of SnO2 nano-dispersion with a concentration of 12% and a particle size range of 0.1-1 micrometers, and an appropriate amount of deionized water under air. The volume fractions are 25% SnO2 nano-dispersion and 75% deionized water. Pour the deionized water into the SnO2 nano-dispersion and stir thoroughly on a thermostatic magnetic stirrer for 20-30 minutes, maintaining a rotor speed of 100-300 rpm. This yields a SnO2 dispersion of the first concentration, which is designated as the standard concentration of the SnO2 solution and named 1.0-SnO2. Additionally, SnO2 solutions with concentrations of 0.8 and 1.2 times the standard concentration are prepared for different SnO2 film thicknesses and named 0.8-SnO2 and 1.2-SnO2, respectively, for later use.
[0009] Step 3: Place the cleaned CZTSSe / CdS film on an intelligent spin coater. Use a pipette to transfer 100 μl of SnO2 dispersion of the first concentration and evenly drop it onto the center of the front side of the film. The spin coating speed is 2000-6000 rpm, the acceleration is 400-1200 rpm / s, and the spin coating time is 20-40 s.
[0010] Step 4: Place the spin-coated SnO2 film on a 150℃ hot plate and anneal it in air atmosphere for 30 minutes. Then place it in a ceramic boat and cool it in air atmosphere. After cooling to room temperature, deposit the SnO2 electron transport layer to obtain the SnO2 electron transport layer.
[0011] The advantages and beneficial effects of this invention are as follows: the SnO2 material prepared by the sol-gel method for the electron transport layer of CZTSSe thin-film solar cells has good energy level matching, low energy loss, can reduce interlayer defects, improve interface contact, and thus improve the photoelectric performance of the material. The preparation method of this invention is simple, the process is short and the cost is low, providing a certain research idea for thin-film solar cells. Attached Figure Description
[0012] Figure 1 This is the Raman spectrum of the GeO / CZTSSe / CdS / SnO2 device in this invention.
[0013] Figure 2 This is the ultraviolet transmission spectrum of the 1.0-SnO2 thin film in this invention.
[0014] Figure 3 This is the UV-vis absorption spectrum of the 1.0-SnO2 thin film in this invention.
[0015] Figure 4 This is a diagram showing the band gap characterization results of the 1.0-SnO2 thin film in this invention.
[0016] Figure 5 This is a PL fluorescence characterization result of the GeO / CZTSSe / CdS / 1.0-SnO2 device in this invention.
[0017] Figure 6 This is a PL fluorescence characterization result of the GeO / CZTSSe / CdS control group device in this invention.
[0018] Figure 7 This is the ultraviolet transmission spectrum of the 0.8-SnO2 thin film in this invention.
[0019] Figure 8 This is a PL fluorescence characterization result of the GeO / CZTSSe / CdS / 0.8-SnO2 device in this invention.
[0020] Figure 9 This is the ultraviolet transmission spectrum of the 1,2-SnO2 thin film in this invention.
[0021] Figure 10 This is a PL fluorescence characterization result of the GeO / CZTSSe / CdS / 1.2-SnO2 device in this invention. Detailed Implementation
[0022] The present invention will be further described below with reference to the accompanying embodiments.
[0023] Example 1: Preparation of 1.0-SnO2 thin film electron transport layer
[0024] In this embodiment, the preparation steps of the SnO2 electron transport layer include:
[0025] (1-1) Cleaning work before preparation
[0026] Prepare several clean Mo / GeO / CZTSSe / CdS films, sample bottles, magnetic balls, battery boxes for holding devices, and ceramic boats. Clean them sequentially with deionized water, isopropanol, and anhydrous ethanol using ultrasonic cleaning, each for 15-20 minutes, repeating 2-3 times. After ultrasonic cleaning, place them in a drying oven to dry. After drying, seal the reagent bottles, battery boxes, and ceramic boats with sealing film and store them for later use.
[0027] (1-2) Preparation of SnO2 solution with first concentration
[0028] Weigh out an appropriate amount of SnO2 nano-dispersion with a concentration of 12% and a nanoparticle size of 0.1-1 micrometers, and an appropriate amount of deionized water, with a volume fraction of 25% SnO2 nano-dispersion and 75% deionized water. Pour the deionized water into the SnO2 nano-dispersion and place it on a thermostatic magnetic stirrer to stir thoroughly for 20-30 minutes, maintaining a rotor speed of 100-300 rpm. After mixing, a SnO2 nano-dispersion of the first concentration is obtained and set aside for later use.
[0029] (1-3) Preparation of SnO2 electron transport layer
[0030] Place the cleaned molybdenum-plated conductive glass on an intelligent spin coater, and use a pipette to transfer 100 μl of SnO2 dispersion and evenly drop it onto the center of the front side of the Mo / GeO / CZTSSe / CdS film. The spin coating speed is 2000-6000 rpm, the acceleration is 400-1200 rpm / s, and the spin coating time is 20-40 s.
[0031] (1-4) Characterization of the product
[0032] Characterization of the 1.0mm thick SnO2 thin film is shown in the attached figure. Figure 1-5 As shown. Figure 1 The image shows the Raman spectral analysis of the 1.0-SnO2 thin film. Figure 1 The Raman spectrum shown is at 173 cm⁻¹ -1 197 cm -1 234 cm -1 A scattering peak of CZTSSe was found at 297 cm⁻¹. -1 The presence of CdS scattering peaks indicates that the CZTSSe crystal structure remains unchanged, exhibiting a single zinc studite structure without the formation of other impurity phases. This demonstrates that the SnO2 film prepared through the above steps will not adversely affect the CZTSSe / CdS structure serving as the substrate.
[0033] like Figure 2The image shows the UV transmittance spectrum of the 1.0-SnO2 thin film. The 1.0-thickness SnO2 thin film exhibits high transmittance (>90%) in the 450-800nm wavelength range, which is the main absorption area of the CZTSSe / CdS layer, indicating that the SnO2 thin film of this thickness does not affect the light absorption of the CZTSSe / CdS structure.
[0034] Figures 3-4 The image shows the UV absorption spectrum of the SnO2-1 sample and the calculated band gap of the SnO2 thin film. The absorbance of the film increases sharply in the UV region (<320 nm) and is relatively low in the visible region (400-900 nm). The optical band gap (E) was calculated using the Taucplot method based on the UV-vis measurement results. g The band gap of the SnO2 thin film material was found to be 3.82 eV, indicating that the SnO2 thin film prepared by this method has good energy level matching with both CdS and ITO structures, and is suitable as an electron transport layer.
[0035] Figure 5 The fluorescence spectrum analysis of the 1.0-SnO2 sample is shown. Steady-state fluorescence (PL) was spectrally analyzed on the surface of the prepared GeO2 / CZTSSe / CdS / SnO2 device thin film using 532 nm excitation light. Figure 6 The image shows the sample without a SnO2 layer. The highest PL intensity without a SnO2 layer indicates that without the SnO2 electron transport layer, carriers are difficult to effectively extract, leading to significantly enhanced interfacial recombination. With the addition of SnO2, the PL intensity is the lowest, indicating that SnO2 covers the defect states on the CZTSSe surface, effectively suppressing interfacial recombination and reducing nonradiative recombination. The device using 1.0-SnO2 has the lowest PL intensity, indicating that the SnO2 concentration is optimal, resulting in the highest carrier extraction efficiency. The 0.8-SnO2 layer may be due to its thinness, failing to completely cover the CZTSSe surface, resulting in interfacial defects remaining in some areas. The 1.2-SnO2 layer may be due to its excessive thickness, hindering carrier transport and causing an increase in PL intensity.
[0036] Example 2: Preparation of an electron transport layer of SnO2 thin film with a thickness of 0.8 times
[0037] (2-1) Cleaning of molybdenum-plated conductive glass and equipment: Same as in Example 1.
[0038] (2-2) Preparation of 0.8 times the first concentration SnO2 solution.
[0039] Weigh out an appropriate amount of SnO2 nano-dispersion with a concentration of 12% and a nanoparticle size of 0.1-1 micrometers, and an appropriate amount of deionized water, with a volume fraction of 20% SnO2 nano-dispersion and 880% deionized water. Pour the deionized water into the SnO2 nano-dispersion and place it on a thermostatic magnetic stirrer to stir thoroughly for 20-30 minutes, maintaining the rotor speed at 100-300 rpm. After mixing, a SnO2 nano-dispersion with a concentration of 0.8 times is obtained and set aside.
[0040] (2-3) Preparation of SnO2 electron transport layer: Same as in Example 1.
[0041] (2-4) Characterization of the product
[0042] Characterization of the 0.8 times thick SnO2 film is shown in the attached figure. Figure 7-8 As shown.
[0043] Figure 7 The UV-UV transmittance spectrum shown indicates that the SnO2 film with a thickness of 0.8 times exhibits high transmittance (>90%) in the 450-800nm wavelength range, which is the main absorption area of the CZTSSe / CdS layer. This suggests that the SnO2 film of this thickness does not affect the light absorption of the CZTSSe / CdS layer.
[0044] Figure 8 The PL test results show that the carrier extraction efficiency of the 0.8-SnO2 film is lower than that of the 1.0-SnO2 film. This may be because the SnO2 is too thin and fails to completely cover the CZTSSe surface, resulting in interface defects in some areas.
[0045] Example 3: Preparation of an electron transport layer of SnO2 thin film with a thickness of 1.2 times
[0046] (3-1) Cleaning of molybdenum-plated conductive glass and equipment: Same as in Example 1.
[0047] (3-2) Preparation of 1.2 times the first concentration SnO2 solution
[0048] Weigh out an appropriate amount of SnO2 nano-dispersion with a concentration of 12% and a nanoparticle size of 0.1-1 micrometers, and an appropriate amount of deionized water, with a volume fraction of 30% SnO2 nano-dispersion and 70% deionized water. Pour the deionized water into the SnO2 nano-dispersion and place it on a thermostatic magnetic stirrer to stir thoroughly for 20-30 minutes, maintaining a rotor speed of 100-300 rpm. After mixing, a SnO2 nano-dispersion with a first concentration of 1.2 times is obtained and set aside.
[0049] (3-3) Preparation of SnO2 electron transport layer: Same as in Example 1.
[0050] (3-4) Characterization of the product
[0051] Characterization of the 1.2 times thick SnO2 film is shown in the attached figure. Figure 9-10 As shown.
[0052] Figure 9 The UV transmittance spectrum shown indicates that the SnO2 film with a thickness of 1.2 times exhibits high transmittance (>90%) in the 450-800nm wavelength range, where the CZTSSe / CdS layer mainly absorbs light, indicating that the SnO2 film of this thickness does not affect the light absorption of the CZTSSe / CdS layer.
[0053] Figure 10 The PL test results show that the carrier extraction efficiency of the 1.2-SnO2 film is lower than that of the 1.0-SnO2 film. This may be because the SnO2 film is too thick, which hinders the carrier transport and leads to an increase in PL intensity.
[0054] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformations based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method, characterized in that, Includes the following steps: (1) Mix SnO2 nano-dispersion with a certain amount of deionized water and stir to obtain SnO2 nano-dispersion of the first concentration; (2) Spin-coating the film treated in (1) with SnO2 nano-dispersion of the first concentration; (3) Anneal the film obtained in (1) in an air environment; (4) The thin film obtained in (2) is placed in a ceramic boat and cooled in air. After cooling to room temperature, a SnO2 electron transport layer for CZTSSe solar cells is obtained.
2. The method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method according to claim 1, characterized in that: The SnO2 nano-dispersion used had a concentration of 12%, the solvent was deionized water, the nanoparticle size was 0.1 μm to 1 μm, the amount of dispersion used was 200 μl, and the amount of deionized water used was 600 μl.
3. The method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method according to claim 1, characterized in that: The stirring time was 30 minutes, the spin coating speed was 4000 rpm, the acceleration was 800 rpm / s, and the spin coating time was 30 s.
4. The method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method according to claim 1, characterized in that: The magnetic balls, reagent bottles, battery boxes, and ceramic boats used in steps (1), (2), (3), and (4) were all ultrasonically cleaned for 20 minutes each with deionized water, isopropanol, and anhydrous ethanol.
5. The method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method according to claim 1, characterized in that: The annealing temperature is 150℃ and the time is 30 minutes.
6. The method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method according to claim 1, characterized in that: Steps (1), (2), (3), and (4) were all carried out at room temperature and in an air environment.
7. The method for preparing a SnO2 electron transport layer for CZTSSe solar cells based on the sol-gel method according to claim 1, characterized in that: The substrate structure used is: molybdenum-plated glass / GeO2 / CZTSSe / CdS.