Boron diffusion method matched with dense grid on surface of photovoltaic cell and photovoltaic module

Abstract

The invention discloses a boron diffusion method matched with a dense grid on the surface of a photovoltaic cell and a photovoltaic module, which are applied to the photovoltaic field, and the method comprises the following steps: setting the temperature in a furnace as a first source introduction temperature, setting the pressure in the furnace as a first furnace pressure, introducing boron source gas into the furnace at a preset flow, and carrying out first-step deposition diffusion treatment on a cell substrate; raising the temperature in the furnace from the first source temperature to a second source temperature, raising the pressure in the furnace from the first furnace pressure to a second furnace pressure, introducing boron source gas into the furnace at a preset flow rate, and carrying out second-step deposition diffusion treatment on the battery substrate; raising the temperature in the furnace from the second source temperature to a third source temperature, raising the pressure in the furnace from the second furnace pressure to a third furnace pressure, introducing boron source gas into the furnace at a preset flow rate, and carrying out third-step deposition diffusion treatment on the battery substrate; and carrying out knot pushing treatment on the battery substrate. According to the invention, deposition diffusion treatment is carried out by combining corresponding temperature and pressure in a three-step source passing mode, so that the photoelectric conversion efficiency can be improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaics, and in particular to a boron expansion method for matching the dense grid on the surface of a photovoltaic cell and a photovoltaic module. Background Technology

[0002] The characteristic structure of existing tunnel oxide passivated contact (TOPCon) solar cells mainly involves fabricating a 1nm-2nm tunnel oxide layer on the back of the cell, followed by the deposition of a doped polycrystalline silicon layer. After high-temperature annealing, both layers form a passivated contact structure. Utilizing the selective passage of the tunnel oxide layer, allowing only electrons to pass through, it provides excellent interface passivation for the back of the silicon wafer. The upper limit of efficiency for existing TOPCon cells is 28.7%, but current TOPCon cell efficiencies are far below this theoretical value. To improve the photoelectric conversion efficiency, one readily apparent approach is to add printed grid lines on the front side of the cell. However, in current production lines, simply adding printed grid lines on the front side has not yielded significant results.

[0003] Therefore, how to provide a method for adding printed grid lines to the surface of photovoltaic cells to effectively improve the photoelectric conversion efficiency of the cells is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a boron expansion method and a photovoltaic module that matches the dense grid on the surface of a photovoltaic cell, thereby solving the problem that in the prior art, simply increasing the number of front-side printed grid lines does not significantly improve the photoelectric conversion efficiency.

[0005] To address the aforementioned technical problems, this invention provides a boron diffusion method for matching the dense grid on the surface of photovoltaic cells, comprising:

[0006] Step 1: Set the furnace temperature to the first power supply temperature and the furnace pressure to the first furnace pressure. Introduce boron source gas into the furnace at a preset flow rate to perform the first deposition and diffusion treatment on the battery substrate.

[0007] Step 2: Increase the furnace temperature from the first source temperature to the second source temperature, and increase the furnace pressure from the first furnace pressure to the second furnace pressure. Introduce the boron source gas into the furnace at the preset flow rate to perform the second deposition and diffusion treatment on the battery substrate.

[0008] Step 3: Increase the furnace temperature from the second source temperature to the third source temperature, and increase the furnace pressure from the second furnace pressure to the third furnace pressure. Introduce the boron source gas into the furnace at the preset flow rate to perform the third deposition and diffusion treatment on the battery substrate.

[0009] Step 4: After completing the third step of deposition and diffusion treatment on the battery substrate, the battery substrate is subjected to push-bonding treatment to complete the boron diffusion on the battery substrate.

[0010] Optionally, the reaction conditions in step 1 include:

[0011] The furnace temperature was set to 810°C to 830°C, the furnace pressure was set to 110 Pa, and boron source gas was introduced into the furnace at a flow rate of 140 sccm to 200 sccm for 200 seconds.

[0012] The reaction conditions for step 2 include:

[0013] The furnace temperature is raised to 815°C to 835°C, the furnace pressure is raised to 130 Pa, and the boron source gas is introduced into the furnace at a flow rate of 140 sccm to 200 sccm for 180 seconds.

[0014] The reaction conditions for step 3 include:

[0015] The furnace temperature is raised to 820 to 840 degrees Celsius, the furnace pressure is raised to 150 Pa, and the boron source gas is introduced into the furnace at a flow rate of 140 to 200 sccm for 180 seconds.

[0016] Optionally, oxygen is introduced into the furnace at a flow rate of 450 sccm to 650 sccm during the first, second, and third deposition diffusion treatments of the battery substrate.

[0017] Optionally, step 4 includes:

[0018] Step 41: After completing the third deposition and diffusion process on the battery substrate, the furnace temperature is raised from the third source temperature to the bonding temperature, and the furnace pressure is maintained at the third furnace pressure. The boron source gas is introduced into the furnace at the preset flow rate, and nitrogen is introduced into the furnace at the first preset flow rate to perform the first bonding process on the battery substrate.

[0019] Step 42: Maintain the furnace temperature at the bonding temperature and increase the furnace pressure from the third furnace pressure to the fourth furnace pressure. Stop the supply of the boron source gas and supply nitrogen into the furnace at the second preset nitrogen flow rate to perform the second bonding process on the battery substrate.

[0020] Step 43: Maintain the furnace temperature at the bonding temperature and the furnace pressure at the fourth furnace pressure. Introduce nitrogen into the furnace at the second preset nitrogen flow rate to perform the third bonding process on the battery substrate, thus completing the boron diffusion process on the battery substrate.

[0021] Optionally, the reaction conditions in step 41 include:

[0022] The furnace temperature is raised to 850 to 870 degrees Celsius, the furnace pressure is maintained at 150 Pa, the boron source gas is introduced into the furnace at a flow rate of 140 to 200 sccm, and nitrogen is introduced into the furnace at the first preset nitrogen flow rate.

[0023] The reaction conditions in step 42 include:

[0024] The furnace temperature is maintained at 850 degrees Celsius to 870 degrees Celsius, the furnace pressure is increased to 300 Pa, the boron source gas is stopped, and nitrogen is introduced into the furnace at the second preset nitrogen flow rate.

[0025] The reaction conditions for step 43 include:

[0026] The furnace temperature is maintained at 850 to 870 degrees Celsius, the furnace pressure is maintained at 300 Pa, and nitrogen is introduced into the furnace at the second preset nitrogen flow rate.

[0027] Optionally, during the first step of bonding treatment of the battery substrate, nitrogen gas is introduced into the furnace at a flow rate of 2500 sccm to 3500 sccm.

[0028] Nitrogen gas was introduced into the furnace at a flow rate of 3000 sccm to 5000 sccm during the second and third bonding processes of the battery substrate.

[0029] Optionally, after the third step of bonding treatment on the battery substrate, the following steps are also included:

[0030] The furnace temperature was lowered to 800-820 degrees Celsius, and the furnace pressure was increased to 600 Pa. Nitrogen gas was introduced into the furnace at a flow rate of 16,000 sccm for 620 seconds to complete the cooling process.

[0031] Optionally, a purging process is performed after the first deposition and diffusion treatment of the battery substrate and after the second deposition and diffusion treatment of the battery substrate.

[0032] Optionally, before step 1, the following steps are also included:

[0033] The furnace temperature is set to the first power supply temperature, and nitrogen and oxygen are introduced into the furnace to prepare an oxide layer on the surface of the battery substrate.

[0034] The present invention also provides a photovoltaic module, including solar cells;

[0035] The solar cell is a solar cell that has undergone boron diffusion using the aforementioned boron diffusion method that matches the dense grid on the surface of a photovoltaic cell.

[0036] As can be seen, the boron diffusion method for matching the dense grid on the surface of photovoltaic cells provided by the present invention includes the following steps: Step 1: Setting the furnace temperature to a first source temperature and the furnace pressure to a first furnace pressure, and introducing boron source gas into the furnace at a preset flow rate to perform a first deposition diffusion treatment on the cell substrate; Step 2: Raising the furnace temperature from the first source temperature to a second source temperature and the furnace pressure from the first furnace pressure to the second furnace pressure, and introducing boron source gas into the furnace at a preset flow rate to perform a second deposition diffusion treatment on the cell substrate; Step 3: Raising the furnace temperature from the second source temperature to a third source temperature and the furnace pressure from the second furnace pressure to the third furnace pressure, and introducing boron source gas into the furnace at a preset flow rate to perform a third deposition diffusion treatment on the cell substrate; Step 4: After completing the third deposition diffusion treatment on the cell substrate, performing a push-bonding treatment on the cell substrate to complete the boron diffusion on the cell substrate. This invention employs a three-step power source approach, combined with corresponding temperature and pressure, to perform deposition and diffusion treatment on the battery substrate. This approach can match the dense grid on the surface of the photovoltaic cell, effectively improving the photoelectric conversion efficiency of the prepared battery cell.

[0037] In addition, the present invention also provides a photovoltaic module that has the same beneficial effects as described above. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 A flowchart illustrating a boron diffusion method for matching the dense grid on the surface of a photovoltaic cell, provided in an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0042] Please refer to Figure 1 , Figure 1A flowchart illustrating a boron diffusion method for matching the dense grid on the surface of a photovoltaic cell, provided as an embodiment of the present invention. The method may include:

[0043] Step 1: Set the furnace temperature to the first power supply temperature and the furnace pressure to the first furnace pressure. Introduce boron source gas into the furnace at a preset flow rate to perform the first deposition and diffusion treatment on the battery substrate.

[0044] The execution subject of this embodiment is a boron diffusion treatment device. In this embodiment, the furnace temperature is set to a first inlet temperature, the furnace pressure is set to a first furnace pressure, and boron source gas is introduced into the furnace at a preset flow rate. At this time, the battery substrate undergoes the first deposition diffusion treatment using the aforementioned parameters. The first inlet temperature for this first deposition diffusion treatment is set lower than the inlet temperature for subsequent deposition diffusion treatment steps. This initial low-temperature stage allows the dopant (such as phosphorus or boron) to slowly penetrate, reducing the problem of abrupt concentration gradient changes on the battery substrate surface. Simultaneously, by setting an initial low-pressure stage, gas phase nucleation is reduced, preventing the reactant gas from forming particles prematurely or causing non-uniform deposition, thus improving the uniformity of the doping treatment, enhancing film quality, and forming a shallow junction structure. This allows for precise control of the doping concentration on the battery substrate surface, avoiding excessively deep dopant diffusion. In this embodiment, the rate of temperature and pressure increase needs to be set according to the battery substrate material to avoid substrate stress or uneven deposition due to excessively rapid increases. Specific parameters can be set according to actual conditions. Furthermore, this embodiment can be applied to the TOPCon battery field, i.e., the battery substrate is a TOPCon battery substrate. In the field of TOPCon batteries, the current upper limit of the photoelectric conversion efficiency of TOPCon cells is 28.7%, which has not reached the theoretical limit. In this embodiment, it can be achieved by increasing the number of front grid lines printed on the screen. However, for cells produced on normal production lines, simply increasing the number of front grid lines does not significantly improve the photoelectric conversion efficiency. In this application, the process of increasing the number of front grid lines is combined with the process of matching boron diffusion with low surface concentration shallow junctions to improve the uniformity of the overall sheet resistance of boron diffusion and thus improve the photoelectric conversion efficiency.

[0045] It should be further noted that in this embodiment, when the conventional boron diffusion method (existing conventional boron diffusion methods include: 1. cleaning and pretreatment of the battery substrate; 2. introduction of boron source; 3. high-temperature diffusion; 4. BSG removal; 5. annealing) is applied to the process of preparing battery cells using a 170 screen printing plate, i.e., when applied to battery cells prepared using a high-density grid line screen printing plate (the number of sub-grid lines in the 170 screen printing plate and the high-density grid line screen printing plate is 170, while the number of sub-grid lines in the conventional screen printing plate is 164), there is no improvement in the photoelectric conversion efficiency of the final prepared battery cell. For details, please refer to Table 1, which is a comparative example table of photoelectric conversion efficiencies of battery cells prepared using the same battery substrate and different boron diffusion processes according to an embodiment of the present invention.

[0046] Table 1

[0047]

[0048] The boron diffusion process provided in this embodiment is applied to solar cells prepared by conventional screen printing, i.e., no increase in the number of grid lines printed on the front side. At this time, the photoelectric conversion efficiency is partially improved. For details, please refer to Table 2. Table 2 is a comparison example table of photoelectric conversion efficiency of solar cells prepared by using different solar cell substrates and applying the same boron diffusion process according to the embodiment of the present invention.

[0049] Table 2

[0050]

[0051] The screen printing plate mentioned in this embodiment for increasing the number of front-side printed grid lines is a 500-7 screen printing plate (the 500-7 screen printing plate has 170 sub-grid lines, a thickness of 16 micrometers, a sub-grid line width of 12 micrometers, and 16 positive electrode main grid lines). Furthermore, the boron diffusion process provided in this embodiment can be applied only to the front side of the battery substrate. Prior to this, texturing of the battery substrate can be performed. After completing the boron diffusion treatment on the front side of the battery substrate, the substrate can be sequentially subjected to back-side boron diffusion treatment, alkaline polishing, polycrystalline silicon deposition, annealing, RCA cleaning, atomic layer deposition, front protective film preparation, back protective film preparation, and grid line printing. In addition, in this embodiment, the diffusion sheet resistance can be set to 190 ohms to 210 ohms, and the number of front-side sub-grid lines can be set to 170 to 180. In summary, this application can produce a uniformly surfaced, low-surface-density, shallow-junction solar cell, matched with a screen printing plate for multiple front-side grid lines, thereby improving the photoelectric conversion efficiency of the solar cell.

[0052] Furthermore, to improve the uniformity control of the boron diffusion treatment, the following steps may be included before step 1 above:

[0053] The furnace temperature is set to the first power supply temperature, and nitrogen and oxygen are introduced into the furnace to prepare an oxide layer on the surface of the battery substrate.

[0054] It should be noted that, in this embodiment, the oxide layer prepared before the first deposition-diffusion process reduces the density of active sites on the battery substrate surface, improving the uniformity of the subsequent boron diffusion process. Furthermore, this oxide layer acts as a catalytic interface, promoting the decomposition of the introduced boron source gas into active boron atoms. In this application, nitrogen is used as a carrier gas to dilute oxygen and prevent excessive oxidation of the battery substrate. Further, in this embodiment, after the oxide layer is prepared, a purging step can be performed to prevent oxygen from interfering with the boron source diffusion during the subsequent deposition-diffusion process.

[0055] Step 2: Increase the furnace temperature from the first source temperature to the second source temperature, and increase the furnace pressure from the first furnace pressure to the second furnace pressure. Introduce boron source gas into the furnace at a preset flow rate to perform the second deposition and diffusion treatment on the battery substrate.

[0056] In this embodiment, the furnace temperature is set to the second source temperature, the furnace pressure is set to the second furnace pressure, and boron source gas is introduced into the furnace at a preset flow rate. At this time, the battery substrate is subjected to the second deposition and diffusion process with the parameters set above. The second source temperature for the second deposition and diffusion process is set to be lower than the source temperature of the subsequent third deposition and diffusion process, but higher than the source temperature of the first deposition and diffusion process. This step is used to adjust the distribution of dopants in the silicon body and balance the longitudinal concentration gradient. By appropriately increasing the pressure in the middle of the deposition process, the collision frequency of the reactive gas can be increased, the deposition rate can be accelerated, and the production efficiency can be improved.

[0057] Step 3: Increase the furnace temperature from the second source temperature to the third source temperature, and increase the furnace pressure from the second furnace pressure to the third furnace pressure. Introduce boron source gas into the furnace at a preset flow rate to perform the third step of deposition and diffusion treatment on the battery substrate.

[0058] In this embodiment, the furnace temperature is set to the third source temperature, the furnace pressure is set to the third furnace pressure, and boron source gas is introduced into the furnace at a preset flow rate. The battery substrate is then subjected to the third-step deposition and diffusion process using the aforementioned parameters. The third source temperature for this third-step deposition and diffusion process is set to a higher temperature than the source temperatures in the previous two deposition and diffusion processes. Combined with the final high-pressure stage, this promotes densification of the diffusion process. This embodiment, by gradually increasing the temperature and performing the boron diffusion process in three steps, avoids the accumulation of thermal stress in the battery substrate (e.g., silicon wafer) due to sudden temperature changes, reducing the risk of lattice defects (such as dislocations and cracks) and improving material integrity. Furthermore, the step-by-step heating method prevents excessively rapid diffusion of dopants at high temperatures, which could lead to excessively deep junctions or insufficient surface concentration. Furthermore, in this embodiment, the temperature and time of each step in the three-step deposition diffusion process can be independently optimized, which facilitates the adjustment of the doping profile and can meet the needs of different battery structures (such as PERC and TOPCon). In addition, the low-temperature initial stage can reduce the accumulation of dopants on the surface of the battery substrate, and the high-temperature stage can fully activate the dopants, thus avoiding the precipitation of metal impurities or dopants that form secondary defects.

[0059] Step 4: After completing the third step of deposition and diffusion treatment on the battery substrate, the battery substrate is subjected to push-bonding treatment to complete the boron diffusion on the battery substrate.

[0060] In this embodiment, the battery substrate that has undergone the three-step deposition and diffusion process is subjected to push-junction processing to improve the uniformity of the fabrication. This embodiment utilizes the TOPCon boron diffusion-based high-resistivity dense-gate technology, which can employ silicon wafers with dimensions of 183.75 mm in length, 182 mm in width, and 130 micrometers in thickness, or larger silicon wafers can be used.

[0061] Furthermore, to improve the uniform inward distribution of boron atoms during the bonding process, the bonding process performed on the battery substrate after the third deposition and diffusion process to complete the boron diffusion on the battery substrate may include:

[0062] Step 41: After completing the third deposition and diffusion process on the battery substrate, the furnace temperature is raised from the third source temperature to the push-bonding temperature, and the furnace pressure is maintained at the third furnace pressure. Boron source gas is introduced into the furnace at a preset flow rate, and nitrogen is introduced into the furnace at a first preset flow rate to perform the first push-bonding process on the battery substrate.

[0063] Step 42: Maintain the furnace temperature at the bonding temperature and increase the furnace pressure from the third furnace pressure to the fourth furnace pressure. Stop the introduction of boron source gas and introduce nitrogen into the furnace at the second preset nitrogen flow rate to perform the second bonding process on the battery substrate.

[0064] Step 43: Maintain the furnace temperature at the bonding temperature and the furnace pressure at the fourth furnace pressure. Introduce nitrogen into the furnace at the second preset nitrogen flow rate to perform the third bonding process on the battery substrate, thus completing the boron diffusion process on the battery substrate.

[0065] It should be noted that this embodiment employs a three-step push-bond process. By further increasing the temperature beyond the third source temperature, boron atoms are activated to diffuse deeper into the crystal lattice of the battery substrate. Simultaneously, the boron source gas is maintained to prevent a sudden drop in boron atom concentration at the substrate surface. During the first push-bond process, only the temperature is increased to the push-bond temperature, while the furnace pressure remains constant at the third furnace pressure to avoid pressure fluctuations interfering with the stability of the temperature-increasing push-bond process. After the initial temperature increase, subsequent push-bond processes do not require further temperature increases; the temperature can be maintained at the push-bond temperature. During the second push-bond process, the furnace pressure is increased to the fourth furnace pressure, enhancing the solubility and diffusion driving force of boron atoms on the substrate surface. At this point, the introduction of boron source gas is stopped to ensure sufficient diffusion of the introduced boron atoms while preventing excessive boron doping. Subsequently, during the third push-bond process, the furnace pressure is maintained at the fourth furnace pressure to promote uniform distribution of boron atoms within the substrate, reducing surface defects. By employing the step-by-step bonding method described above, lattice damage can be reduced, thus mitigating the problem of substrate warping caused by single-step high-temperature and high-pressure bonding. In this embodiment, the heating step is completed first, followed by increasing the furnace pressure under high-temperature conditions, which can suppress boron volatilization. Furthermore, in this application, boron source gas is continuously introduced during the heating and bonding step to compensate for the heat consumption of surface boron atoms.

[0066] Furthermore, to ensure the successful completion of the three-step debonding process, the reaction conditions in step 41 above may include:

[0067] The furnace temperature is raised to 850 to 870 degrees Celsius, the furnace pressure is maintained at 150 Pa, boron source gas is introduced into the furnace at a flow rate of 140 to 200 sccm, and nitrogen is introduced into the furnace at a first preset flow rate to perform the first step of bonding process on the battery substrate.

[0068] Accordingly, the reaction conditions for step 42 may include:

[0069] The furnace temperature is maintained at 850 to 870 degrees Celsius, the furnace pressure is increased to 300 Pa, the boron source gas is stopped, and nitrogen is introduced into the furnace at a second preset nitrogen flow rate to perform the second step of bonding process on the battery substrate.

[0070] Accordingly, the reaction conditions for step 43 may include:

[0071] The furnace temperature is maintained at 850 to 870 degrees Celsius, and the furnace pressure is maintained at 300 Pa. Nitrogen gas is introduced into the furnace at a second preset nitrogen flow rate to perform the third step of bonding treatment on the battery substrate, thereby completing the boron diffusion process on the battery substrate.

[0072] It should be noted that in this embodiment, the junction-pushing temperature is set to 850-870℃, instead of the conventional setting of above 900℃. By extending the junction-pushing time (using a three-step junction-pushing process), the diffusion depth is compensated, achieving the target junction depth while reducing thermal stress damage to the silicon wafer. In this embodiment, during the first junction-pushing process, the furnace pressure is maintained at 150Pa to avoid pressure changes interfering with the gas phase balance during the heating and junction-pushing process. Subsequently, in this embodiment, the furnace pressure is increased from 150Pa to 300Pa, which can quickly establish a high diffusion driving force, while stopping the source prevents the boron concentration on the surface of the battery substrate from becoming too high. Finally, in this embodiment, the high pressure of 300Pa is maintained for further junction-pushing to ensure sufficient junction depth. In addition, in this embodiment, oxygen supply is stopped during the junction-pushing stage to avoid the problem of boron atom concentration in the battery substrate becoming too low due to boron source loss. In the three-step junction-pushing process of this embodiment, the first step achieves boron atom pre-activation through low-temperature source supply, the second step drives boron atoms to distribute to deeper layers through a high-pressure jump, and the third step maintains a constant pressure to ensure a uniform concentration gradient.

[0073] Furthermore, in order to avoid the problem of uneven boron atom distribution due to excessively high concentration in local deposition diffusion treatment, nitrogen gas can be introduced into the furnace at a flow rate of 2500 sccm to 3500 sccm during the first step of bonding treatment of the battery substrate.

[0074] Nitrogen gas was introduced into the furnace at a flow rate of 3000 sccm to 5000 sccm during the second and third bonding processes of the battery substrate.

[0075] It should be noted that in this embodiment, during the first step of the bonding process, nitrogen gas is introduced into the furnace at a flow rate of 2500 sccm-3500 sccm to dilute the boron source gas to the ideal concentration, avoid local oversaturation deposition, and promote uniform gas phase transport. In the second step of the bonding process, the flow rate of nitrogen gas is increased to 3000 sccm-5000 sccm to accelerate the removal of residual boron source gas in the furnace, prevent secondary deposition, and at the same time, by enhancing gas phase flow, promote the diffusion of adsorbed boron atoms into the depth of the silicon lattice.

[0076] Furthermore, to ensure rapid and uniform cooling of the battery substrate after the boron diffusion treatment, the above-mentioned third-step bonding process for the battery substrate may further include:

[0077] The furnace temperature was lowered to 800-820 degrees Celsius, and the furnace pressure was increased to 600 Pa. Nitrogen gas was introduced into the furnace at a flow rate of 16,000 sccm for 620 seconds to complete the cooling process.

[0078] It should be noted that in this embodiment, the temperature is rapidly reduced from the bonding temperature to 800℃-820℃. This allows boron atoms in the silicon lattice to rearrange in an orderly manner during the cooling process, reducing dislocation defects caused by thermal stress. Furthermore, the 600Pa high pressure prevents boron atoms from escaping from the surface during the cooling phase. High-pressure nitrogen enhances the heat transfer efficiency to the battery substrate, increasing the cooling rate. In this embodiment, the furnace pressure and nitrogen flow rate need to be comprehensively considered and set to specified parameter values ​​to ensure preparation efficiency. It should be further noted that if only the furnace pressure is increased while the nitrogen flow rate remains constant, the cooling rate decreases, requiring a longer cooling time. Conversely, if only the nitrogen flow rate is increased while the furnace pressure remains constant, boron will be lost through volatilization. In addition, in this embodiment, after completing the third bonding process, the cooling step needs to be initiated as soon as possible to avoid excessive boron diffusion due to prolonged exposure to high temperatures. For example, the cooling step can be performed within 30 seconds after completing the third bonding process, and after cooling, the material can be directly cooled to room temperature at atmospheric pressure.

[0079] Furthermore, to ensure the efficiency and uniformity of the deposition diffusion treatment, the reaction conditions in step 1 above may include:

[0080] The furnace temperature was set to 810°C to 830°C, the furnace pressure was set to 110 Pa, and boron source gas was introduced into the furnace at a flow rate of 140 sccm to 200 sccm for 200 seconds to perform the first step of deposition and diffusion treatment on the battery substrate.

[0081] Accordingly, the reaction conditions for step 2 may include:

[0082] The furnace temperature is raised to 815 to 835 degrees Celsius, the furnace pressure is raised to 130 Pa, and boron source gas is introduced into the furnace at a flow rate of 140 to 200 sccm for 180 seconds to perform the second-step deposition and diffusion treatment on the battery substrate.

[0083] Accordingly, the reaction conditions in step 3 may include:

[0084] The furnace temperature is raised to 820 to 840 degrees Celsius, the furnace pressure is raised to 150 Pa, and boron source gas is introduced into the furnace at a flow rate of 140 to 200 sccm for 180 seconds to perform the third-step deposition and diffusion treatment on the battery substrate.

[0085] It should be noted that, in this embodiment, the first source temperature is set to 810°C to 830°C, the second source temperature to 815°C to 835°C, and the third source temperature to 820°C to 840°C. The initial deposition diffusion treatment temperature is set to 810°C to 830°C to ensure a moderate initial decomposition rate of the boron source gas and to prevent uneven deposition of the diffusion layer. Furthermore, during the process of increasing the source temperature from the first source temperature to the second source temperature, and from the second source temperature to the third source temperature, the minimum and maximum source temperatures are increased by only 5°C at a time. This small, gradual temperature increase avoids thermal stress cracking of the battery substrate caused by sudden temperature changes. In addition, in this embodiment, the initial low pressure is set to 110 Pa to reduce gas-phase nucleation and ensure orderly adsorption of boron atoms. In the subsequent diffusion steps, the furnace pressure is set to 130 Pa and 150 Pa respectively to enhance gas-phase transport efficiency, promote deep diffusion, ensure linear increase of furnace pressure, and improve the uniformity of deposition diffusion. In this application, if only the temperature is increased without increasing the pressure (e.g., maintaining 110 Pa and raising it to 840°C), it will lead to excessively high concentration and insufficient junction depth in the battery substrate. On the other hand, if only the pressure is increased without increasing the temperature (e.g., maintaining 810°C at 150 Pa), the diffusion rate will be low and the production efficiency will decrease. Therefore, this application needs to combine the above-mentioned furnace pressure parameters and source temperature parameters to perform deposition diffusion on the battery substrate. In this embodiment, boron source gas is introduced into the furnace at a preset flow rate in the three-step deposition and diffusion process. This flow rate range can maintain the stability of the boron partial pressure in the furnace and avoid the problem of uneven doping concentration caused by fluctuations in the boron source flow rate. It should be further noted that the preset flow rate in this embodiment must ensure a sufficient supply of boron source gas, while preventing the waste of boron source gas or the generation of side reactions, such as avoiding the generation of parasitic deposition.

[0086] Furthermore, in order to improve the uniformity of boron diffusion doping, oxygen can be introduced into the furnace at a flow rate of 450 sccm to 650 sccm during the first, second, and third deposition diffusion processes on the battery substrate.

[0087] It should be noted that the oxygen introduced in this embodiment can react with excess boron source gas to generate Box (boron oxide) intermediate product, which inhibits the parasitic deposition of gaseous boron particles, thereby improving doping uniformity and achieving the effect of oxidation inhibition. In addition, in this embodiment, the flow rate of oxygen introduced into the furnace is set to 450 sccm to 650 sccm. At this time, the flow rate of oxygen introduced needs to meet the following requirements: (1) effectively inhibit the parasitic deposition of BCl3 (boron trichloride) and avoid the adhesion of boron particles on the furnace wall and the edge of the substrate; (2) avoid excessive oxidation reaction consuming too much boron source, which would lead to insufficient boron concentration on the surface of the battery substrate. In this embodiment, oxygen is introduced into the furnace at a flow rate of 450 sccm to 650 sccm, covering all the above-mentioned first step deposition diffusion treatment, second step deposition diffusion treatment, and third step deposition diffusion treatment processes.

[0088] Furthermore, to avoid residual gas affecting the accuracy of the boron diffusion process, a purging process can be performed after the first deposition diffusion process on the battery substrate and after the second deposition diffusion process on the battery substrate.

[0089] It should be noted that in this embodiment, a purging process is performed after the first and second deposition-diffusion treatments to remove residual boron source gas in the furnace, preventing it from interfering with the concentration gradient during the second deposition-diffusion treatment. Additionally, if oxygen was introduced in the preceding steps, the purging process eliminates free oxygen atoms, preventing the formation of an oxide barrier layer during the second deposition-diffusion treatment. Furthermore, the next deposition-diffusion treatment should be performed immediately after the purging process to avoid fluctuations in the furnace environment. The time interval between the purging and deposition-diffusion treatments can be set to 10 seconds or less.

[0090] The boron diffusion method for matching the dense grid on the surface of photovoltaic cells provided in this invention includes the following steps: Step 1: Setting the furnace temperature to a first source temperature and the furnace pressure to a first furnace pressure, and introducing boron source gas into the furnace at a preset flow rate to perform a first deposition diffusion treatment on the cell substrate; Step 2: Raising the furnace temperature from the first source temperature to a second source temperature and the furnace pressure from the first furnace pressure to the second furnace pressure, and introducing boron source gas into the furnace at a preset flow rate to perform a second deposition diffusion treatment on the cell substrate; Step 3: Raising the furnace temperature from the second source temperature to a third source temperature and the furnace pressure from the second furnace pressure to the third furnace pressure, and introducing boron source gas into the furnace at a preset flow rate to perform a third deposition diffusion treatment on the cell substrate; Step 4: After completing the third deposition diffusion treatment on the cell substrate, performing a push-bonding treatment on the cell substrate to complete the boron diffusion on the cell substrate. This invention employs a three-step power source approach, combined with corresponding temperature and pressure, to perform deposition and diffusion treatment on the battery substrate. This approach can match the dense grid on the surface of the photovoltaic cell, effectively improving the photoelectric conversion efficiency of the prepared battery cell.

[0091] Furthermore, in this embodiment of the invention, before the deposition and diffusion treatment of the battery substrate, nitrogen and oxygen are introduced into the furnace by setting the furnace temperature to the first source temperature to prepare an oxide layer on the surface of the battery substrate, thereby improving the uniformity and ease of control of the boron diffusion treatment. By employing a three-step push-bonding process to push the deposited and diffused battery substrate, the uniform inward distribution of boron atoms in the push-bonding step is improved. By setting specific parameters for the three-step push-bonding process, the smooth completion of the three-step push-bonding steps is ensured, achieving the target junction depth while reducing thermal stress damage to the silicon wafer. By introducing nitrogen into the furnace at a flow rate of 2500 sccm-3500 sccm during the first push-bonding process, local oversaturation deposition can be avoided, while promoting uniform gas phase transport. By increasing the nitrogen flow rate to 3000 sccm-5000 sccm during the second push-bonding process, the removal of residual boron source gas in the furnace can be accelerated. To prevent secondary deposition, after the third step of the bonding process on the battery substrate, the furnace temperature is lowered to 800-820 degrees Celsius, the furnace pressure is increased to 600 Pa, and nitrogen gas is introduced into the furnace at a flow rate of 16000 sccm for 620 seconds to complete the cooling process. This allows boron atoms in the silicon lattice to rearrange in an orderly manner during the cooling process, reducing dislocation defects caused by thermal stress and preventing boron atoms from escaping from the surface of the battery substrate, thereby improving cooling efficiency and the yield of products undergoing boron diffusion treatment. By setting specific parameters in the three-step deposition and diffusion process, the efficiency and uniformity of the deposition and diffusion process can be guaranteed. Introducing oxygen during the three-step deposition and diffusion process can further improve the uniformity of boron diffusion doping. By performing a purging process after the first and second steps of the deposition and diffusion process, the accuracy of the boron diffusion process can be avoided by residual gas.

[0092] In one feasible embodiment, the above-described boron diffusion method for matching the dense grid on the surface of a photovoltaic cell may specifically include the following steps:

[0093] It should be noted that in this embodiment, a 500-7 screen is used to prepare the grid lines. The total thickness of the grid lines in the solar cell prepared by this 500-7 screen is 16 μm, the number of sub-grid lines is 170, the width of the grid lines is 12 μm, and the number of positive electrode main grid lines is 16. The sheet resistance of the pre-boron diffusion process is set to 190-210 ohms per square, and the sheet resistance of the post-boron diffusion process is set to 2000 ohms per square. The solar cell with uniform surface and low surface concentration shallow junction produced by this invention, matched with a screen printing plate with added sub-grid lines on the front side, thereby improving the conversion efficiency of the solar cell. Furthermore, in this embodiment, the optimal selection of the pre-boron diffusion sheet resistance can be set to 200 ohms per square, and the optimal selection of the post-boron diffusion sheet resistance can be set to 450 ohms per square.

[0094] The boron diffusion method for matching the dense grid on the surface of photovoltaic cells in this embodiment is as follows:

[0095] Step S1: Perform the first deposition diffusion treatment (to achieve low-temperature source induction and improve the uniformity of sheet resistance), wherein the source induction temperature is set to 810℃ to 830℃, the source induction duration is set to 200s, the boron source flow rate is set to 140sccm to 200sccm, the oxygen flow rate is set to 450sccm to 650sccm, and the pressure inside the furnace tube is set to 110pa.

[0096] Step S2: Perform the second deposition and diffusion treatment (to achieve variable temperature and pressure source), wherein the source temperature is set to 815℃ to 835℃, the source duration is set to 180s, the boron source flow rate is set to 140sccm to 200sccm, the oxygen flow rate is set to 450sccm to 650sccm, and the furnace tube pressure is set to 130pa.

[0097] Step S3: Perform the third step of deposition and diffusion treatment (to achieve variable temperature and pressure source), wherein the source temperature is set to 820℃ to 840℃, the source duration is set to 180s, the flow rate of the boron source is set to 140sccm to 200sccm, the flow rate of the oxygen source is set to 450sccm to 650sccm, and the pressure inside the furnace tube is set to 150pa.

[0098] Step S4: Perform the first step of the knot-pushing process, which includes:

[0099] S41: First heating and pushing treatment (to achieve oxygen-free propulsion and reduce surface concentration), heating duration is set to 120S, boron source flow rate is set to 140sccm to 200sccm, nitrogen flow rate is set to 2500sccm to 3500sccm, and furnace tube pressure is set to 150pa.

[0100] S42: Perform the second heating and pushing treatment (to achieve heating and pushing, increase the bonding depth, and improve uniformity through back pressure), wherein the bonding temperature is set to 850℃ to 870℃, the heating duration is 600S, the nitrogen flow rate is set to 3000sccm to 5000sccm, and the pressure inside the furnace tube is set to 300pa.

[0101] It should be noted that in steps S4 and S5 above, the temperature of the push junction is raised to 850°C to 870°C through a second heating process. That is, the common heating goal of steps S4 and S5 is to ultimately raise the temperature of the push junction to 850°C to 870°C.

[0102] Step S5: Perform the second step of the bonding process (to achieve constant temperature bonding and increase bonding depth), wherein the bonding temperature is set to 850℃ to 870℃, the heating duration is set to 200S, the nitrogen flow rate is set to 3000sccm to 5000sccm, and the pressure inside the furnace tube is set to 300pa.

[0103] Step S6: Perform cooling treatment (achieve cooling), wherein the temperature is set to 800℃ to 820℃, the cooling duration is set to 620S, the nitrogen flow rate is set to 16000sccm, and the pressure inside the furnace tube is set to 600pa.

[0104] The photovoltaic module provided in the embodiments of the present invention is described below. The photovoltaic module described below and the boron diffusion method for matching the dense grid on the surface of the photovoltaic cell described above can be referred to in correspondence.

[0105] The photovoltaic module provided in this embodiment of the invention may include solar cells;

[0106] The solar cell is a solar cell in which boron diffusion is completed using the aforementioned boron diffusion method that matches the dense grid on the surface of the photovoltaic cell.

[0107] It should be noted that the solar cell provided in this embodiment is a solar cell prepared by boron diffusion through the boron diffusion method that matches the dense grid on the surface of the photovoltaic cell. Therefore, the photovoltaic module also possesses the beneficial effects of the above method.

[0108] The photovoltaic module provided by the embodiments of the present invention includes a solar cell, which is a solar cell that has undergone boron diffusion through the aforementioned boron diffusion method that matches the dense grid on the surface of the photovoltaic cell. The present invention uses a three-step power supply method, combined with corresponding temperature and pressure, to perform deposition and diffusion treatment on the solar cell substrate, which can match the dense grid on the surface of the photovoltaic cell and effectively improve the photoelectric conversion efficiency of the prepared solar cell.

[0109] The following describes an electronic device provided by an embodiment of the present invention. The electronic device described below can be referred to in correspondence with the boron diffusion method for matching the dense grid on the surface of a photovoltaic cell described above.

[0110] Please refer to Figure 2 , Figure 2 A schematic diagram of the structure of an electronic device provided in an embodiment of the present invention may include:

[0111] Memory 10 is used to store computer programs;

[0112] Processor 20 is used to execute a computer program to implement the steps of the boron diffusion method described above for matching the dense grid on the surface of a photovoltaic cell;

[0113] The diffusion furnace 30 is connected in communication with the control unit in the diffusion furnace.

[0114] The memory 10, processor 20, and communication interface 31 all communicate with each other through the communication bus 32.

[0115] In this embodiment of the invention, the memory 10 is used to store one or more programs. The programs may include program code, which includes computer operation instructions. In this embodiment, the memory 10 may store programs for implementing the following functions:

[0116] Step 1: Set the furnace temperature to the first power supply temperature and the furnace pressure to the first furnace pressure. Introduce boron source gas into the furnace at a preset flow rate to perform the first deposition and diffusion treatment on the battery substrate.

[0117] Step 2: Increase the furnace temperature from the first source temperature to the second source temperature, and increase the furnace pressure from the first furnace pressure to the second furnace pressure. Introduce the boron source gas into the furnace at the preset flow rate to perform the second deposition and diffusion treatment on the battery substrate.

[0118] Step 3: Increase the furnace temperature from the second source temperature to the third source temperature, and increase the furnace pressure from the second furnace pressure to the third furnace pressure. Introduce the boron source gas into the furnace at the preset flow rate to perform the third deposition and diffusion treatment on the battery substrate.

[0119] Step 4: After completing the third step of deposition and diffusion treatment on the battery substrate, the battery substrate is subjected to push-bonding treatment to complete the boron diffusion on the battery substrate.

[0120] In one possible implementation, the memory 10 may include a program storage area and a data storage area, wherein the program storage area may store the operating system and applications required for at least one function; and the data storage area may store data created during use.

[0121] Furthermore, memory 10 may include read-only memory and random access memory, providing instructions and data to the processor. A portion of the memory may also include NVRAM. The memory stores operating systems and operating instructions, executable modules, or data structures, or subsets thereof, or extended sets thereof, wherein the operating instructions may include various operating instructions for implementing various operations. The operating system may include various system programs for implementing various basic tasks and handling hardware-based tasks.

[0122] Processor 20 can be a central processing unit (CPU), an application-specific integrated circuit, a digital signal processor, a field-programmable gate array, or other programmable logic device. Processor 20 can be a microprocessor or any conventional processor. Processor 20 can call programs stored in memory 10.

[0123] Communication interface 31 can be an interface for the communication module, used to connect with other devices or systems.

[0124] Of course, it should be noted that, Figure 2 The structure shown does not constitute a limitation on the electronic device in the embodiments of this application. In practical applications, the electronic device may include more than Figure 2 More or fewer components as shown, or combinations of certain components.

[0125] The following describes the computer-readable storage medium provided in the embodiments of the present invention. The computer-readable storage medium described below can be referred to in correspondence with the boron diffusion method for matching the dense grid on the surface of photovoltaic cells described above.

[0126] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the boron diffusion method for matching the dense grid on the surface of a photovoltaic cell.

[0127] The computer-readable storage medium may include various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0128] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0129] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0130] Finally, it should be noted that in this document, relationships such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0131] The present invention provides a detailed description of a boron expansion method for matching the surface grid of a photovoltaic cell and a photovoltaic module. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A boron diffusion method for matching the dense grid on the surface of a photovoltaic cell, characterized in that, include: Step 1: Set the furnace temperature to the first power supply temperature and the furnace pressure to the first furnace pressure. Introduce boron source gas into the furnace at a preset flow rate to perform the first deposition and diffusion treatment on the battery substrate. Step 2: Increase the furnace temperature from the first source temperature to the second source temperature, and increase the furnace pressure from the first furnace pressure to the second furnace pressure. Introduce the boron source gas into the furnace at the preset flow rate to perform the second deposition and diffusion treatment on the battery substrate. Step 3: Increase the furnace temperature from the second source temperature to the third source temperature, and increase the furnace pressure from the second furnace pressure to the third furnace pressure. Introduce the boron source gas into the furnace at the preset flow rate to perform the third deposition and diffusion treatment on the battery substrate. Step 4: After completing the third step of deposition and diffusion treatment on the battery substrate, the battery substrate is subjected to push-bonding treatment to complete the boron diffusion on the battery substrate.

2. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 1, characterized in that, The reaction conditions in step 1 include: The furnace temperature was set to 810°C to 830°C, the furnace pressure was set to 110 Pa, and boron source gas was introduced into the furnace at a flow rate of 140 sccm to 200 sccm for 200 seconds. The reaction conditions for step 2 include: The furnace temperature is raised to 815°C to 835°C, the furnace pressure is raised to 130 Pa, and the boron source gas is introduced into the furnace at a flow rate of 140 sccm to 200 sccm for 180 seconds. The reaction conditions for step 3 include: The furnace temperature is raised to 820 to 840 degrees Celsius, the furnace pressure is raised to 150 Pa, and the boron source gas is introduced into the furnace at a flow rate of 140 to 200 sccm for 180 seconds.

3. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 2, characterized in that, Oxygen was introduced into the furnace at a flow rate of 450 sccm to 650 sccm during the first, second, and third deposition diffusion processes on the battery substrate.

4. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 1, characterized in that, Step 4 includes: Step 41: After completing the third deposition and diffusion process on the battery substrate, the furnace temperature is raised from the third source temperature to the bonding temperature, and the furnace pressure is maintained at the third furnace pressure. The boron source gas is introduced into the furnace at the preset flow rate, and nitrogen is introduced into the furnace at the first preset flow rate to perform the first bonding process on the battery substrate. Step 42: Maintain the furnace temperature at the bonding temperature and increase the furnace pressure from the third furnace pressure to the fourth furnace pressure. Stop the supply of the boron source gas and supply nitrogen into the furnace at the second preset nitrogen flow rate to perform the second bonding process on the battery substrate. Step 43: Maintain the furnace temperature at the bonding temperature and the furnace pressure at the fourth furnace pressure. Introduce nitrogen into the furnace at the second preset nitrogen flow rate to perform the third bonding process on the battery substrate, thus completing the boron diffusion process on the battery substrate.

5. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 4, characterized in that, The reaction conditions in step 41 include: The furnace temperature is raised to 850 to 870 degrees Celsius, the furnace pressure is maintained at 150 Pa, the boron source gas is introduced into the furnace at a flow rate of 140 to 200 sccm, and nitrogen is introduced into the furnace at the first preset nitrogen flow rate. The reaction conditions in step 42 include: The furnace temperature is maintained at 850 degrees Celsius to 870 degrees Celsius, the furnace pressure is increased to 300 Pa, the boron source gas is stopped, and nitrogen is introduced into the furnace at the second preset nitrogen flow rate. The reaction conditions for step 43 include: The furnace temperature is maintained at 850 to 870 degrees Celsius, the furnace pressure is maintained at 300 Pa, and nitrogen is introduced into the furnace at the second preset nitrogen flow rate.

6. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 5, characterized in that, During the first step of bonding the battery substrate, nitrogen gas is introduced into the furnace at a flow rate of 2500 sccm to 3500 sccm. Nitrogen gas was introduced into the furnace at a flow rate of 3000 sccm to 5000 sccm during the second and third bonding processes of the battery substrate.

7. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 5, characterized in that, After the third step of bonding the battery substrate, the process also includes: The furnace temperature was lowered to 800-820 degrees Celsius, and the furnace pressure was increased to 600 Pa. Nitrogen gas was introduced into the furnace at a flow rate of 16,000 sccm for 620 seconds to complete the cooling process.

8. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 1, characterized in that, After the first deposition and diffusion process on the battery substrate, and after the second deposition and diffusion process on the battery substrate, a purging process is performed respectively.

9. The boron diffusion method for matching the dense grid on the surface of a photovoltaic cell according to claim 1, characterized in that, Before step 1, the following is also included: The furnace temperature is set to the first power supply temperature, and nitrogen and oxygen are introduced into the furnace to prepare an oxide layer on the surface of the battery substrate.

10. A photovoltaic module, characterized in that, Including battery cells; The solar cell is a solar cell in which boron diffusion is completed by the boron diffusion method for matching the dense grid on the surface of a photovoltaic cell as described in any one of claims 1 to 9.

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