A method for making photovoltaic bc cells using inkjet printing of hot melt inks

Abstract

The application discloses a method for manufacturing photovoltaic BC cells by using inkjet printing hot melt ink, which comprises the following steps: step 1, silicon wafer pretreatment; step 2, hot melt ink preparation; step 3, inkjet printing equipment debugging; step 4, P area mask manufacturing; step 5, etching back process for manufacturing P area; step 6, removing P area mask; step 7, N area mask manufacturing; step 8, etching back process for manufacturing N area; step 9, high-temperature activation and doping optimization; and step 10, subsequent processing. The method can overcome the problems of complex process, high cost and poor mask stability in the prior art, and achieve the goals of simplifying the process, reducing the cost, improving the cell performance and production efficiency.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell manufacturing technology, and in particular to a method for manufacturing photovoltaic BC cells using inkjet printing hot melt ink. Background Technology

[0002] Photovoltaic technology, as a key area for sustainable energy development, has made BC (Browser-Contact) cells a focus of current research and industrial development due to their unique back-contact structure, which effectively reduces light shading by the front electrode and greatly improves photoelectric conversion efficiency. The core step in BC cell manufacturing is to prepare high-quality and precisely distributed back-side P-regions and N-regions.

[0003] Traditional fabrication processes for the P and N regions on the back of BC batteries present numerous challenges. For instance, while photolithography can achieve high-precision patterning, it involves expensive equipment investment and causes some damage to the P and N regions, resulting in a loss of battery efficiency. It also has limitations in doping uniformity and pattern accuracy, making it difficult to meet the growing demand for high-efficiency batteries. Furthermore, conventional inkjet printing combined with ordinary mask materials suffers from insufficient acid resistance and stability in subsequent processes such as etching back, and the lack of precise pattern control can easily lead to pattern deformation or damage, affecting the consistency and reliability of battery performance.

[0004] Hot-melt ink, a special functional material, is solid at room temperature but melts into a liquid state upon heating for inkjet printing, and then rapidly solidifies after printing. It offers advantages such as solvent-free evaporation, fast curing speed, and strong adhesion, providing a new approach to solving the challenges of existing BC battery fabrication processes. By combining inkjet printing hot-melt ink technology with the etchingback process, it is hoped that a highly efficient, low-cost method can be developed to fabricate the P- and N-regions on the back of BC batteries while ensuring battery performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing photovoltaic BC cells using inkjet printing hot melt ink, so as to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for fabricating photovoltaic BC cells using inkjet printing hot melt ink includes the following steps:

[0008] Step 1: Silicon wafer pretreatment;

[0009] 1) Double-sided polishing of silicon wafers: Select high-quality N-type silicon wafers and first perform double-sided polishing to ensure that the surface of the silicon wafers is free of impurities;

[0010] 2) Deposit a tunneling oxide layer and poly-Si, thermally oxidize the back side to form a tunneling oxide layer, and then deposit the amorphous silicon on the wafer;

[0011] 3) Boron diffusion for the preparation of p-poly polar BSG borosilicate glass as a mask;

[0012] 4) P-area etching back groove: The BSG in this area is locally patterned using inkjet printing hot melt ink. Wet etching is then used to etch the areas where no ink was printed to expose the silicon substrate. Due to the protection of the hot melt ink, the protected area of ​​the BSG and the p-poly underneath are preserved.

[0013] Step 2: Prepare hot melt ink;

[0014] The hot melt ink for P-area masking uses thermoplastic resin as the base, with added wax and appropriate additives. The components are uniformly mixed by high-speed stirring, ultrasonic dispersion and filtration. The melting temperature range of this hot melt ink is 60-150℃.

[0015] The hot melt ink for N-area mask uses thermoplastic resin as the base, with added wax and appropriate additives. It is uniformly mixed and filtered by high-speed stirring and ultrasonic dispersion. The melting temperature of this hot melt ink is also controlled between 60-150℃.

[0016] Step 3: Inkjet printer setup;

[0017] High-precision inkjet printing equipment is selected and rigorously calibrated. The nozzle temperature is set to be 20-30℃ higher than the melting temperature of the hot melt ink, i.e., 80-180℃, to ensure that the hot melt ink can melt and be ejected smoothly.

[0018] Precisely controlling the stage temperature between 0-30℃ ensures stable silicon wafer temperature during printing, which is beneficial for the rapid curing and good adhesion of hot melt ink;

[0019] The printing accuracy is calibrated to a high level of ±5μm to ensure that the required P and N area patterns can be printed accurately. At the same time, the ink jet volume is precisely controlled at 5-50pL / drop to ensure the thickness and quality uniformity of the mask.

[0020] Step 4: P-area mask fabrication;

[0021] Based on the pre-designed pattern of the P area on the back of the BC battery, with a width of 200-500μm and a spacing of 200-400μm, a precise printing path file is generated using professional computer-aided design (CAD) software and then imported into the inkjet printing equipment.

[0022] The prepared P-area mask is loaded into the ink cartridge of the inkjet printer using hot melt ink. The printer is started and inkjet printed on the back of the silicon wafer according to the design pattern. During the printing process, the print head is kept at a stable distance of 0.1-2mm from the silicon wafer surface to ensure the uniformity and accuracy of inkjet printing.

[0023] After printing, the silicon wafer is allowed to cool naturally to room temperature in 1-120 seconds. The hot melt ink solidifies rapidly, forming a strong P-area acid-resistant mask on the back of the silicon wafer. The mask thickness is controlled between 5-50 μm.

[0024] Step 5: Using the etching back process to create the P area;

[0025] The silicon wafer with the P-area hot melt mask is placed in the etching equipment, and the etching back process is performed using an etchant to etch the silicon wafer;

[0026] Precise control of parameters such as etching time and temperature is achieved. During the etching process, the etchant reacts chemically with the silicon wafer area not covered by the mask, selectively removing silicon material to form P-type doped regions with specific depth and shape. The etching depth can be precisely controlled by adjusting the etching time and etchant concentration.

[0027] After etching is complete, remove the silicon wafer from the etching equipment and immediately rinse it in a large amount of deionized water for at least 5 minutes to thoroughly remove the residual etchant and reaction products on the surface of the silicon wafer and avoid affecting subsequent processes.

[0028] Step 6: Remove the mask from the P region;

[0029] The hot melt mask in the P-region is removed by ultrasonic cleaning with organic solvent. A solvent with good solubility in hot melt ink is selected. The silicon wafer is placed in an ultrasonic cleaning tank containing the solvent. Under the action of ultrasound, the organic solvent can quickly dissolve the hot melt mask and remove it from the surface of the silicon wafer without damaging the formed P-region structure.

[0030] After cleaning, the silicon wafer is placed in deionized water again for ultrasonic cleaning to remove residual solvent from the surface of the silicon wafer. Finally, the silicon wafer is placed in a drying oven to ensure that the surface of the silicon wafer is dry and clean.

[0031] Step 7: N-region mask fabrication;

[0032] Based on the design pattern of alternating N and P areas, the corresponding print path file is generated using CAD software and imported into the inkjet printer.

[0033] On the back of the silicon wafer where the P-area has been fabricated and cleaned, inkjet printing is performed according to the design pattern. Similarly, printing parameters are strictly controlled during the printing process to ensure printing quality.

[0034] After printing, the silicon wafer cools naturally, allowing the hot melt ink to solidify and form an acid-resistant mask in the N-region. It is important to ensure that the alignment accuracy between the N-region mask and the edge of the P-region is ±10μm to guarantee the accurate layout of the P-region and the N-region.

[0035] Step 8: Using the etching back process to create area N;

[0036] The silicon wafer with the N-region hot melt mask is placed back into the etching equipment and the etching back process is performed using etching conditions similar to those used to create the P-region, but with some parameter adjustments.

[0037] After etching, following the same method as removing the P-region mask, the N-region hot melt mask was first removed by ultrasonic cleaning with organic solvent, and then the silicon wafer was cleaned and dried with deionized water.

[0038] Step 9: High-temperature activation and doping optimization;

[0039] The silicon wafers treated as described above are placed in a high-temperature furnace for high-temperature activation and doping optimization. Under the protection of nitrogen or argon inert gas, boron and phosphorus elements diffuse further into the silicon wafer and are activated at high temperature, optimizing the electrical properties of the P-region and N-region, making the doping concentration more uniform, and improving carrier mobility and lifetime.

[0040] After the high-temperature treatment is completed, the silicon wafer is cooled to room temperature with the furnace to avoid the adverse effects of sudden temperature changes on the silicon wafer structure and performance.

[0041] Step 10, Post-processing;

[0042] Passivation layer deposition involves depositing a passivation layer on the back of the battery to reduce surface recombination and improve the open-circuit voltage and fill factor. First, an alumina passivation layer is deposited on the back of the silicon wafer using atomic layer deposition (ALD). During deposition, parameters such as reactant gas flow rate, temperature, and deposition cycle are precisely controlled to ensure the quality and uniformity of the alumina layer. Then, a silicon nitride layer is deposited on the surface of the alumina layer using plasma-enhanced chemical vapor deposition (PECVD). The SiN passivation layer is optimized by adjusting PECVD process parameters such as RF power, gas flow rate, and deposition temperature. x The optical and electrical properties of the layer are improved to enhance its anti-reflection and passivation effects;

[0043] The metallization process uses laser grooving technology to precisely form contact holes on the passivation layer, ensuring accurate alignment between the contact holes and the P- and N-region patterns. Laser grooving parameters, such as laser energy, pulse width, and frequency, need to be optimized based on the passivation layer thickness and silicon wafer characteristics to guarantee grooving quality and avoid excessive damage to the silicon wafer. Subsequently, the back electrode is fabricated using electronic paste screen printing or electroplating. For screen printing, highly conductive silver paste is selected, and precision screen printing equipment is used to print the silver paste onto corresponding positions in the P- and N-regions, forming interdigitated metal contacts. After printing, the silicon wafer is placed in a sintering furnace and sintered under a nitrogen protective atmosphere, allowing the silver electrode to form a good ohmic contact with the silicon wafer, reducing contact resistance and improving the battery's conductivity.

[0044] In step 2, the hot-melt ink used for the P-area mask has a base of 60-80% thermoplastic resin and 15-30% wax by weight. Appropriate additives, including plasticizers and dispersants, account for 5-10% by weight. The high-speed stirring speed is 1000-3000 rpm, and the stirring time is 1-3 hours. The ultrasonic dispersion and filtration power is 200-500W, and the ultrasonic time is 30-60 minutes. The hot-melt ink used for the N-area mask also has a base of 60-80% thermoplastic resin and 15-30% wax by weight. Appropriate additives, including plasticizers and dispersants, account for 5-10% by weight. The high-speed stirring speed is 1000-3000 rpm, and the stirring time is 1-3 hours. The ultrasonic dispersion and filtration power is 200-500W, and the ultrasonic time is 30-60 minutes.

[0045] In step 5, the etchant is a hydrofluoric acid solution with a concentration of 5-10 wt%; the etching time is 1-10 minutes, the temperature is controlled at 20-50℃, and the etching depth can be precisely controlled to 0-1 μm by adjusting the etching time and etchant concentration.

[0046] In step 6, the silicon wafer is placed in an ultrasonic cleaning tank containing solvent. The ultrasonic power is set to 100-300W, the cleaning temperature is controlled at 15-50℃, and the cleaning time is 30-300 seconds. After cleaning, the silicon wafer is placed in deionized water for ultrasonic cleaning again to remove the residual solvent on the surface of the silicon wafer. The cleaning time is 3-5 minutes. Finally, the silicon wafer is placed in a drying oven and dried at 80-120℃ for 10-20 minutes.

[0047] In step 8, the etching back process is performed using etching conditions similar to those used for creating the P region, but with some parameter adjustments. The etchant concentration is adjusted to 5-10 wt% for HF and the etching time to 1-8 minutes to form the required N-type doped region. The etching temperature is still controlled at 20-50℃.

[0048] In step 9, the temperature is raised to 800-1000℃ under the protection of nitrogen or argon inert gas, and the temperature is held for 10-30 minutes in a high-temperature environment.

[0049] In step 10, an aluminum oxide passivation layer is deposited on the back of the silicon wafer using an atomic layer deposition device, with a thickness controlled at 3-8 nm. The silicon nitride layer has a thickness of 70-90 nm. In the metallization process, the silicon wafer is placed in a sintering furnace and sintered at 600-900℃ for 10-30 seconds under a nitrogen protective atmosphere.

[0050] The beneficial effects of this invention are: Simplified process: This invention combines inkjet printing of hot melt ink to form an acid-resistant mask with an etching-back process. Compared to traditional complex processes such as photolithography and multiple diffusion, this significantly reduces process steps and equipment usage, shortens the production cycle, and improves production efficiency. For example, traditional photolithography processes may require multiple steps such as coating, exposure, development, and etching, while this invention can complete the initial fabrication of P and N regions through simple inkjet printing and etching, reducing process steps by approximately 30-50%.

[0051] Cost reduction: On the one hand, the use of hot-melt ink avoids expensive and environmentally harmful chemical reagents such as photoresist and developer, significantly reducing material costs. On the other hand, the simplified process reduces equipment investment and energy consumption, lowering production costs. It is estimated that using the method of this invention, the production cost of each battery can be reduced by approximately 20-30%.

[0052] High mask stability: The acid-resistant mask formed after the hot-melt ink has cured exhibits excellent stability and adhesion. It remains intact in the acidic etching environment of the etching back process, resisting deformation or detachment, thus ensuring the accuracy and quality of the P- and N-region patterns. Experimental verification shows that using the hot-melt mask of this invention, the pattern integrity retention rate during etching can reach over 98%, effectively improving the consistency and reliability of battery performance.

[0053] Battery performance enhancement: Precisely controlled inkjet printing and etching-back processes, along with optimized high-temperature activation and subsequent processing, result in P- and N-regions with excellent electrical properties and precise geometry. The battery's open-circuit voltage, short-circuit current, and fill factor are all significantly improved, effectively enhancing the battery's conversion efficiency. Actual testing shows that the BC battery prepared using this method achieves a conversion efficiency 1-2 percentage points higher than batteries prepared using traditional processes, reaching a high efficiency level of 24-26%.

[0054] Environmentally friendly: This invention reduces the use and emissions of chemical reagents, and the organic solvents can be recycled, meeting the requirements of green manufacturing and promoting the sustainable development of the photovoltaic industry. Detailed Implementation

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] Example 1

[0057] Silicon wafer pretreatment;

[0058] Select resistivity N-type monocrystalline silicon wafers were texturized on both sides for 15 minutes at 75°C using a 3wt% KOH solution to form a pyramidal textured surface. They were then ultrasonically cleaned sequentially in deionized water, acetone, and ethanol for 5 minutes each, and dried in a 100°C oven for 20 minutes. Finally, an ICP etching apparatus was used to... Flow rate 20 sccm The back side of the silicon wafer was etched using a flow rate of 10 sccm, an etching power of 200 W, and an etching time of 5 minutes. Finally, a 10 nm thick intrinsic amorphous silicon buffer layer was deposited on the back side of the wafer using a PECVD system. Flow rate 30 sccm, deposition temperature 250℃, deposition time 10 minutes.

[0059] Hot melt ink preparation;

[0060] Preparation of hot-melt ink for P-area mask: 70 parts by weight of polyamide resin and 25 parts by weight of... Mix with 5 parts by weight of additives, stir at 2000 rpm for 2 hours, and then ultrasonically disperse at 300W for 45 minutes. Prepare hot-melt ink for N-area masks: Mix 75 parts by weight of polyester resin and 20 parts by weight of... Mix with 5 parts by weight of the additive, and stir and disperse as before.

[0061] Inkjet printer setup;

[0062] Set the nozzle temperature of the inkjet printer to 130℃, the stage temperature to 30℃, calibrate the printing accuracy to ±5μm, and control the ink volume to 20pL / drop.

[0063] P-area mask fabrication;

[0064] Design the P-area pattern with a width of 400μm and a spacing of 400μm, generate the printing path file, and import it into the device. After printing, the silicon wafer cools naturally to form the P-area mask, with a thickness of approximately 10-20μm.

[0065] Etching back process for P-zone – BSG removal;

[0066] The silicon wafer is placed in an etching apparatus and etched for 3 minutes at 25°C using a 10wt% HF etchant. After etching, it is rinsed thoroughly with plenty of deionized water for 5 minutes. The P-area is fabricated using the etching back process – hot melt wax removal.

[0067] The silicon wafer was placed in a 2% KOH + 5% BDG solvent and cleaned at 25°C for 3 minutes, followed by a 3-minute rinse with deionized water.

[0068] Etching back process to create P-zone – p-Poly removal;

[0069] The silicon wafer with the hot melt wax removed is placed in a pre-prepared solution (volume ratio of KOH:DI water:NI10V09 additive 69L / 415L / 3L), the temperature is set to 80 degrees, and the etching is carried out for 3 minutes to form p-poly except for the p-region.

[0070] Etching back process for BSG removal in P-zone – n-zone;

[0071] The silicon wafer is placed in an etching apparatus and etched for 3 minutes at 25°C using an etchant with an HF concentration of 5-10 wt%. After etching, it is rinsed with plenty of deionized water for 5 minutes. This ultimately forms P / N tower base structures.

[0072] N-region mask fabrication;

[0073] Design the N-region pattern: 300μm wide and 400μm pitch, generate the printing path file, and import it into the device. After printing, the silicon wafer cools naturally to form the N-region mask, with a thickness of approximately 10-20μm.

[0074] Etching back process for N-zone – PSG removal;

[0075] The silicon wafer was placed in an etching apparatus and etched for 3 minutes at 25°C using an etchant with a 10wt% HF concentration. After etching, it was rinsed with plenty of deionized water for 5 minutes.

[0076] Etching back process creates N-zone – hot melt wax removal;

[0077] The silicon wafer was placed in a 2% KOH + 5% BDG solvent and cleaned at 25°C for 3 minutes, followed by a 3-minute rinse with deionized water.

[0078] Etching back process to create P-zone – p-Poly removal;

[0079] The silicon wafer with the hot melt wax removed is placed in a pre-prepared solution (volume ratio of KOH:DI water:NI10V09 additive 69L / 415L / 3L), the temperature is set to 80 degrees, and the etching is carried out for 3 minutes to form an n-poly except for the n-region.

[0080] Etching back process for PSG removal in n-zone – p-zone;

[0081] The silicon wafer is placed in an etching apparatus and etched for 3 minutes at 25°C using an etchant with an HF concentration of 5-10 wt%. After etching, it is rinsed with plenty of deionized water for 5 minutes. This ultimately forms P / N tower base structures.

[0082] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for fabricating photovoltaic BC cells using inkjet printing hot melt ink, characterized in that, Includes the following steps: Step 1: Silicon wafer pretreatment; 1) Double-sided polishing of silicon wafers: Select high-quality N-type silicon wafers and first perform double-sided polishing to ensure that the surface of the silicon wafers is free of impurities; 2) Deposit a tunneling oxide layer and poly-Si, thermally oxidize the back side to form a tunneling oxide layer, and then deposit the amorphous silicon on the wafer; 3) Boron diffusion for the preparation of p-poly polar BSG borosilicate glass as a mask; 4) P-area etching back groove: The BSG in this area is locally patterned using inkjet printing hot melt ink. Wet etching is then used to etch the areas where no ink was printed to expose the silicon substrate. Due to the protection of the hot melt ink, the protected area of ​​the BSG and the p-poly underneath are preserved. Step 2: Prepare hot melt ink; The hot melt ink for P-area masking uses thermoplastic resin as the base, with added wax and appropriate additives. The components are uniformly mixed by high-speed stirring, ultrasonic dispersion and filtration. The melting temperature range of this hot melt ink is 60-150℃. The hot melt ink for N-area mask uses thermoplastic resin as the base, with added wax and appropriate additives. It is uniformly mixed and filtered by high-speed stirring and ultrasonic dispersion. The melting temperature of this hot melt ink is also controlled between 60-150℃. Step 3: Inkjet printer setup; High-precision inkjet printing equipment is selected and rigorously calibrated. The nozzle temperature is set to be 20-30℃ higher than the melting temperature of the hot melt ink, i.e., 80-180℃, to ensure that the hot melt ink can melt and be ejected smoothly. Precisely controlling the stage temperature between 0-30℃ ensures stable silicon wafer temperature during printing, which is beneficial for the rapid curing and good adhesion of hot melt ink; The printing accuracy is calibrated to a high level of ±5μm to ensure that the required P and N area patterns can be printed accurately. At the same time, the ink volume is precisely controlled at 5-50pL / drop to ensure the thickness and quality uniformity of the mask. Step 4: P-area mask fabrication; Based on the pre-designed pattern of the P area on the back of the BC battery, with a width of 200-500μm and a spacing of 200-400μm, a precise printing path file is generated using professional computer-aided design (CAD) software and then imported into the inkjet printing equipment. The prepared P-area mask is loaded into the ink cartridge of the inkjet printer using hot melt ink. The printer is started and inkjet printed on the back of the silicon wafer according to the design pattern. During the printing process, the print head is kept at a stable distance of 0.1-2mm from the silicon wafer surface to ensure the uniformity and accuracy of inkjet printing. After printing, the silicon wafer is allowed to cool naturally to room temperature in 1-120 seconds. The hot melt ink solidifies rapidly, forming a strong P-area acid-resistant mask on the back of the silicon wafer. The mask thickness is controlled between 5-50 μm. Step 5: Using the etching back process to create the P area; The silicon wafer with the P-area hot melt mask is placed in the etching equipment, and the etching back process is performed using an etchant to etch the silicon wafer; Precise control of parameters such as etching time and temperature is achieved. During the etching process, the etchant reacts chemically with the silicon wafer area not covered by the mask, selectively removing silicon material to form P-type doped regions with specific depth and shape. The etching depth can be precisely controlled by adjusting the etching time and etchant concentration. After etching is complete, remove the silicon wafer from the etching equipment and immediately rinse it in a large amount of deionized water for at least 5 minutes to thoroughly remove the residual etchant and reaction products on the surface of the silicon wafer and avoid affecting subsequent processes. Step 6: Remove the mask from the P region; The hot melt mask in the P-region is removed by ultrasonic cleaning with organic solvent. A solvent with good solubility in hot melt ink is selected. The silicon wafer is placed in an ultrasonic cleaning tank containing the solvent. Under the action of ultrasound, the organic solvent can quickly dissolve the hot melt mask and remove it from the surface of the silicon wafer without damaging the formed P-region structure. After cleaning, the silicon wafer is placed in deionized water again for ultrasonic cleaning to remove residual solvent from the surface of the silicon wafer. Finally, the silicon wafer is placed in a drying oven to ensure that the surface of the silicon wafer is dry and clean. Step 7: N-region mask fabrication; Based on the design pattern of alternating N and P areas, the corresponding print path file is generated using CAD software and imported into the inkjet printer. On the back of the silicon wafer where the P-area has been fabricated and cleaned, inkjet printing is performed according to the design pattern. Similarly, printing parameters are strictly controlled during the printing process to ensure printing quality. After printing, the silicon wafer cools naturally, allowing the hot melt ink to solidify and form an acid-resistant mask in the N-region. It is important to ensure that the alignment accuracy between the N-region mask and the edge of the P-region is ±10μm to guarantee the accurate layout of the P-region and the N-region. Step 8: Using the etching back process to create area N; The silicon wafer with the N-region hot melt mask is placed back into the etching equipment and the etching back process is performed using etching conditions similar to those used to create the P-region, but with some parameter adjustments. After etching, following the same method as removing the P-region mask, the N-region hot melt mask was first removed by ultrasonic cleaning with organic solvent, and then the silicon wafer was cleaned and dried with deionized water. Step 9: High-temperature activation and doping optimization; The silicon wafers treated as described above are placed in a high-temperature furnace for high-temperature activation and doping optimization. Under the protection of nitrogen or argon inert gas, boron and phosphorus elements diffuse further into the silicon wafer and are activated at high temperature, optimizing the electrical properties of the P and N regions, making the doping concentration more uniform, and improving carrier mobility and lifetime. After the high-temperature treatment is completed, the silicon wafer is cooled to room temperature with the furnace to avoid the adverse effects of sudden temperature changes on the silicon wafer structure and performance. Step 10, Post-processing; Passivation layer deposition involves depositing a passivation layer on the back of the battery to reduce surface recombination and improve the open-circuit voltage and fill factor. First, an alumina passivation layer is deposited on the back of the silicon wafer using atomic layer deposition (ALD). During deposition, parameters such as reactant gas flow rate, temperature, and deposition cycle are precisely controlled to ensure the quality and uniformity of the alumina layer. Then, a silicon nitride layer is deposited on the surface of the alumina layer using plasma-enhanced chemical vapor deposition (PECVD). The SiN passivation layer is optimized by adjusting PECVD process parameters such as RF power, gas flow rate, and deposition temperature. x The optical and electrical properties of the layer are improved to enhance its anti-reflection and passivation effects; The metallization process uses laser grooving technology to precisely form contact holes on the passivation layer, ensuring accurate alignment between the contact holes and the P- and N-region patterns. Laser grooving parameters, such as laser energy, pulse width, and frequency, need to be optimized based on the passivation layer thickness and silicon wafer characteristics to guarantee grooving quality and avoid excessive damage to the silicon wafer. Subsequently, the back electrode is fabricated using electronic paste screen printing or electroplating. For screen printing, highly conductive silver paste is selected, and precision screen printing equipment is used to print the silver paste onto corresponding positions in the P- and N-regions, forming interdigitated metal contacts. After printing, the silicon wafer is placed in a sintering furnace and sintered under a nitrogen protective atmosphere, allowing the silver electrode to form a good ohmic contact with the silicon wafer, reducing contact resistance and improving the battery's conductivity.

2. The method for fabricating photovoltaic BC cells using inkjet printing hot melt ink as described in claim 1, characterized in that, In step 2, the hot-melt ink used for the P-area mask has a base of 60-80% thermoplastic resin and 15-30% wax by weight. Appropriate additives, including plasticizers and dispersants, account for 5-10% by weight. The high-speed stirring speed is 1000-3000 rpm, and the stirring time is 1-3 hours. The ultrasonic dispersion and filtration power is 200-500W, and the ultrasonic time is 30-60 minutes. The hot-melt ink used for the N-area mask also has a base of 60-80% thermoplastic resin and 15-30% wax by weight. Appropriate additives, including plasticizers and dispersants, account for 5-10% by weight. The high-speed stirring speed is 1000-3000 rpm, and the stirring time is 1-3 hours. The ultrasonic dispersion and filtration power is 200-500W, and the ultrasonic time is 30-60 minutes.

3. The method for fabricating photovoltaic BC cells using inkjet printing hot melt ink as described in claim 1, characterized in that, In step 5, the etchant is a hydrofluoric acid solution with a concentration of 5-10 wt%; the etching time is 1-10 minutes, the temperature is controlled at 20-50℃, and the etching depth can be precisely controlled to 0-1 μm by adjusting the etching time and etchant concentration.

4. The method for fabricating photovoltaic BC cells using inkjet printing hot melt ink as described in claim 1, characterized in that, In step 6, the silicon wafer is placed in an ultrasonic cleaning tank containing solvent. The ultrasonic power is set to 100-300W, the cleaning temperature is controlled at 15-50℃, and the cleaning time is 30-300 seconds. After cleaning, the silicon wafer is placed in deionized water for ultrasonic cleaning again to remove the residual solvent on the surface of the silicon wafer. The cleaning time is 3-5 minutes. Finally, the silicon wafer is placed in a drying oven and dried at 80-120℃ for 10-20 minutes.

5. The method for fabricating photovoltaic BC cells using inkjet printing hot melt ink as described in claim 1, characterized in that, In step 8, the etching back process is performed using etching conditions similar to those used for creating the P region, but with some parameter adjustments. The etchant concentration is adjusted to 5-10 wt% for HF and the etching time to 1-8 minutes to form the required N-type doped region. The etching temperature is still controlled at 20-50℃.

6. The method for fabricating photovoltaic BC cells using inkjet printing hot melt ink as described in claim 1, characterized in that, In step 9, the temperature is raised to 800-1000℃ under the protection of nitrogen or argon inert gas, and the temperature is held for 10-30 minutes in a high-temperature environment.

7. The method for fabricating photovoltaic BC cells using inkjet printing hot melt ink as described in claim 1, characterized in that, In step 10, an aluminum oxide passivation layer with a thickness of 3-8 nm is deposited on the back of the silicon wafer using atomic layer deposition equipment, and a silicon nitride layer with a thickness of 70-90 nm is deposited. The metallization process involves placing the silicon wafer in a sintering furnace and sintering it at 600-900℃ for 10-30 seconds under a nitrogen protective atmosphere.