Preparation method of crystalline silicon solar cell based on MXene transparent conductive electrode

Abstract

The invention discloses a preparation method of a crystalline silicon solar cell with an MXene transparent electrode, and belongs to the technical field of photovoltaic manufacturing. The method comprises the following steps: firstly, preparing an MXene dispersion liquid; then, on the crystalline silicon substrate on which the passivation layer and the carrier transmission layer are prepared, the MXene dispersion liquid is coated on the carrier transmission layer by adopting a solution method (such as spraying and slit coating); performing drying and low-temperature heat treatment to form an MXene transparent conductive layer; and finally preparing a metal grid line. According to the method, the solution machinability of MXene is utilized, plasma damage caused by a traditional sputtering process is avoided, low-temperature and low-cost electrode preparation is achieved, and the process is compatible with an existing production line. The method is particularly suitable for an SHJ battery with high passivation requirement and a temperature-sensitive structure, can effectively improve the open-circuit voltage and the conversion efficiency of the battery, and has remarkable industrial application value.

Description

Technical Field

[0001] This application relates to the field of photovoltaic manufacturing technology, specifically to a method for preparing a crystalline silicon solar cell, and more particularly to a method for preparing a crystalline silicon solar cell with an MXene transparent conductive electrode. Background Technology

[0002] In the fabrication of crystalline silicon solar cells, especially high-efficiency heterojunction (SHJ) and TOPCon cells, the deposition of transparent conductive electrodes (TCOs) is a crucial step. Currently, the industry commonly uses magnetron sputtering to deposit TCO thin films such as ITO. However, this technology has the following inherent drawbacks:

[0003] 1) Plasma damage: High-energy sputtered particles bombard and damage the underlying delicate passivation layer (such as intrinsic amorphous silicon) and carrier transport layer, leading to increased interfacial recombination and reduced battery open-circuit voltage and efficiency.

[0004] 2) High process cost: It requires a high vacuum environment, the equipment is expensive, energy consumption is high, maintenance is complicated, and ITO target material is expensive.

[0005] 3) Limited material utilization: The sputtering utilization rate of planar targets in sputtering processes is usually less than 30%.

[0006] MXene materials (such as Ti3C2T) x As an emerging two-dimensional conductive material, MXene possesses high conductivity and solution processability, offering a new approach to solving the aforementioned problems. While its potential as a transparent electrode has been recognized, a mature and reliable fabrication method remains lacking for its efficient, non-destructive integration into existing crystalline silicon solar cell production lines. Current research largely remains at the laboratory spin-coating stage, making scale-up difficult, and it has not systematically addressed the entire process from MXene dispersion preparation to integration with the cell's functional layers. Therefore, developing a low-cost, scalable fabrication method to replace sputtering and achieve high-performance MXene transparent electrodes has significant industrial value. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing sputtering processes and provide a method for fabricating crystalline silicon solar cells with MXene transparent electrodes. This method achieves low-damage, low-cost integration of the MXene electrode through optimized solution processing, resulting in high-performance crystalline silicon solar cells.

[0008] To achieve the above objectives, the technical solution adopted by the present invention includes the following steps:

[0009] A method for fabricating a crystalline silicon solar cell with an MXene transparent electrode, characterized by comprising the following steps:

[0010] S1: Preparation of MXene dispersion: By etching and exfoliating the MAX phase of the MXene precursor, a dispersion of monolayer or few-layer MXene nanosheets is obtained, and it is adjusted to a concentration and viscosity suitable for coating.

[0011] S2: Provide a crystalline silicon substrate and form a passivation layer and a carrier transport layer on at least one surface thereon;

[0012] S3: Coating MXene film: The MXene dispersion is coated onto the carrier transport layer using a solution method to form a wet film;

[0013] S4: Drying and heat treatment: The wet film is dried and subjected to low-temperature heat treatment to form the MXene transparent conductive layer;

[0014] S5: Forming metal grid line electrodes: Metal grid lines are fabricated on the MXene transparent conductive layer.

[0015] Preferably, in step S1, the solvent of the MXene dispersion is one or more of water, ethanol, isopropanol, and N-methylpyrrolidone; the concentration of the MXene dispersion is 0.5-50 mg / mL.

[0016] Preferably, in step S1, a surfactant or film-forming aid is added to the MXene dispersion. The surfactant is one or more of Triton X-100, sodium dodecyl sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate, and the amount added is 0.01%-1%.

[0017] Preferably, in step S1, a surfactant or film-forming aid is added to the MXene dispersion. The surfactant is one or more of Triton X-100, sodium dodecyl sulfate, and sodium fatty alcohol polyoxyethylene ether sulfate, and the amount added is 0.01%-1%.

[0018] More preferably, when using the spraying method, the working air pressure is 0.1-0.5 MPa, the distance from the nozzle to the substrate is 1-100 cm, and the substrate temperature is 50-200 °C.

[0019] More preferably, when using slit extrusion coating, the slit width is 10-100 μm and the coating speed is 0.1-2 m / min.

[0020] Preferably, in step S4, the drying is baking on a hot plate at 50-200°C for 1-100 minutes; the heat treatment is annealing at 50-500°C for 1-100 minutes under inert gas or nitrogen protection.

[0021] Preferably, in step S2, the crystalline silicon substrate is an SHJ structure or a TOPCon structure; for the SHJ structure, the carrier transport layer is doped a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, or a-SiCxNy:H, and the heat treatment temperature in step S4 is not higher than 200℃; for the TOPCon structure, the carrier transport layer is doped poly-Si, poly-SiOx, poly-SiCx, poly-SiNx, poly-SiNxOy, poly-SiCxOy, or poly-SiCyNy, or a combination of several of them.

[0022] Preferably, before step S3, the crystalline silicon substrate on which the passivation layer and the carrier transport layer are formed is further subjected to surface treatment, wherein the surface treatment is ultraviolet ozone treatment, oxygen plasma treatment or treatment with a coupling agent, and the treatment time is 10-300 seconds.

[0023] Preferably, in step S5, the metal electrode is prepared by physical vapor deposition, screen printing, or electroplating.

[0024] The advantages and positive effects of this invention are as follows:

[0025] 1) Plasma damage is fundamentally avoided: The entire MXene electrode fabrication process is carried out in a mild solution and low temperature environment, which completely eliminates the physical bombardment and damage to the underlying sensitive functional layer (such as intrinsic / doped amorphous silicon) caused by the sputtering process, perfectly maintaining the passivation effect and laying the foundation for obtaining a high open circuit voltage.

[0026] 2) Significantly reduced process costs: The method does not require high vacuum equipment and has low energy consumption; the cost of MXene raw materials is much lower than that of ITO; the solution method has high material utilization and is easy to achieve large-area, continuous production, making it very suitable for industrial scale-up.

[0027] 3) Excellent film quality and performance: By adjusting the properties of the dispersion and coating process parameters, the thickness, sheet resistance and transmittance of MXene films can be precisely controlled, resulting in high-quality electrodes that are uniform, dense and have good interfacial contact with the underlying layer.

[0028] 4) Good compatibility with existing production lines: processes such as spraying and slot coating are compatible with existing photovoltaic coating technologies, and low-temperature heat treatment is also compatible with low-temperature process chains such as SHJ, which facilitates technology transfer and production line upgrades. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the overall process flow of the preparation method of the present invention.

[0030] Figure 2 Photoluminescence (PL) image of the SHJ battery prepared in Example 1 of this invention (MXene spraying).

[0031] Figure 3 This is a PL diagram of the SHJ battery prepared by conventional sputtering ITO in Comparative Example 1 of this invention. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments.

[0033] Example 1: Spraying method applied to SHJ batteries. This example provides a method for preparing an MXene transparent electrode for SHJ batteries.

[0034] a) Precursor preparation: Provide one N-type SHJ semi-finished cell with a pre-prepared double-sided intrinsic a-Si:H and doped a-Si:H layer.

[0035] b) Surface treatment: The battery cells are treated with ultraviolet ozone for 120 seconds to enhance surface hydrophilicity.

[0036] c) Preparation of dispersion: The Ti3AlC2MAX phase was etched using LiF / HCl solution, and a monolayer of Ti3C2T was obtained after multiple water washings and centrifugation. x The MXene aqueous dispersion was prepared and diluted to a concentration of 5 mg / mL. Subsequently, 0.05% Triton X-100 was added as a film-forming aid.

[0037] d) Spray coating: Transfer the above dispersion to an ultrasonic spray coating system. Set the working air pressure to 0.3 MPa, nozzle distance to 20 cm, and substrate temperature to 60°C. Perform multiple scanning sprays until a uniform wet film is formed on the doped a-Si:H layer.

[0038] e) Heat treatment: First, place the sample on a hot plate at 100°C and bake for 3 minutes to remove most of the solvent. Then, transfer it to a nitrogen-protected oven and anneal at 180°C for 30 minutes to form an MXene transparent conductive layer with a thickness of about 10 nm and a sheet resistance of about 50 Ω / Sq.

[0039] f) Printed electrodes: Finally, silver grid lines are formed on the MXene layer by screen printing and the battery is completed after low-temperature curing.

[0040] Example 2: Slit coating method applied to TOPCon batteries. This example provides a method for preparing an MXene transparent electrode for TOPCon batteries.

[0041] a) Precursor fabrication: Provide an N-type silicon wafer with a pre-fabricated backside TOPCon structure (tunneling oxide layer + phosphorus-doped polysilicon layer) and a frontside boron emitter.

[0042] b) Preparation of dispersion: Ti3C2T x MXene powder was dispersed in isopropanol and then sonicated with a probe to obtain a stable dispersion with a concentration of 5 mg / mL.

[0043] Slit coating: The dispersion was coated onto the doped polysilicon layer of the TOPCon structure using a slit extrusion coating device. The slit width was set to 50 μm and the coating speed to 0.5 m / min.

[0044] Heat treatment: After initial drying in air at 80°C, anneal at 220°C for 20 minutes in a nitrogen atmosphere to form an MXene transparent conductive layer.

[0045] Fabrication of back electrode: Metal electrode is formed on the MXene layer by vapor deposition or printing.

[0046] Comparative Example 1: An ITO electrode (80 nm thick) was deposited on the same SHJ semi-finished product as in Example 1 using a conventional magnetron sputtering process, with the remaining steps being the same.

[0047] Performance verification: The batteries prepared in Example 1 and Comparative Example 1 were tested. The average open-circuit voltage (Voc) of the battery in Example 1 was 740 mV, which was 7 mV higher than that of Comparative Example 1 (733 mV).

[0048] Photoluminescence (PL) spectroscopy was performed on the semiconductor structures prepared in Example 1 and Comparative Example 1 (intermediate products after deposition of transparent electrodes and before fabrication of metal gate lines). The test results showed that the PL spectral intensity of the sample in Example 1 (using the MXene spraying method of this invention) was significantly higher than that of the sample in Comparative Example 1. Figure 2 The result was significantly higher than that of the control sample (using the conventional ITO sputtering method). Figure 3 The solution-based MXene electrode fabrication process employed in this invention completely avoids the bombardment damage to the underlying precision passivation layer (such as the intrinsic amorphous silicon layer) caused by high-energy particles from magnetron sputtering, perfectly preserving the original high passivation level of the crystalline silicon substrate. The significant reduction in PL intensity in the comparative example quantitatively reveals the irreversible plasma damage caused by the sputtering process, leading to an increase in interface defect states and intensified recombination.

[0049] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for fabricating a crystalline silicon solar cell with an MXene transparent electrode, characterized in that, Includes the following steps: S1) Prepare MXene dispersion; S2) A crystalline silicon substrate is provided, and a passivation layer and a carrier transport layer are sequentially formed on at least one surface thereon; S3) The MXene dispersion is coated onto the carrier transport layer using a solution method to form a wet film; S4) The wet film is dried and heat-treated to form an MXene transparent conductive layer; S5) Prepare a metal electrode on the MXene transparent conductive layer.

2. The preparation method according to claim 1, characterized in that, In step S1, the solvent of the MXene dispersion is one or more of water, ethanol, isopropanol, and N-methylpyrrolidone, with a concentration of 0.5-50 mg / mL.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, a surfactant or film-forming aid is added to the MXene dispersion.

4. The preparation method according to claim 1, characterized in that, In step S2, the crystalline silicon substrate is a silicon heterojunction (SHJ) structure or a tunnel oxide passivated contact (TOPCon) structure.

5. The preparation method according to claim 1, characterized in that, When the crystalline silicon substrate is an SHJ structure, the carrier transport layer is a doped a-Si:H, a-SiOx:H, a-SiCx:H, a-SiNx:H, a-SiNxOy:H, a-SiCxOy:H, a-SiCxNy:H, or one or more of oxides, nitrides, oxynitrides and fluorides, and the heat treatment temperature in step S4 is not higher than 200°C.

6. The preparation method according to claim 1, characterized in that, Prior to step S3, the process further includes a surface treatment step on the crystalline silicon substrate on which the passivation layer and carrier transport layer are formed, wherein the surface treatment is ultraviolet ozone treatment, oxygen plasma treatment, or treatment using a coupling agent.

7. The preparation method according to claim 1, characterized in that, The solution method mentioned in step S3 is one of spin coating, spray coating, slot extrusion coating, screen printing, or dip coating.

8. The preparation method according to claim 7, characterized in that, When using the spraying method, the working air pressure is 0.1-0.5MPa, the distance from the nozzle to the substrate is 1-100 cm, and the substrate temperature is 40-80℃.

9. The preparation method according to claim 1, characterized in that, In step S4, the drying temperature is 50-200℃ and the time is 1-100 minutes; the heat treatment is carried out under an inert atmosphere or nitrogen protection, at a temperature of 50-500℃ and for 1-100 minutes.

10. The preparation method according to claim 1, characterized in that, In step S5, the metal electrode is prepared by physical vapor deposition, screen printing, or electroplating.

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