A phosphorus diffusion control process for photovoltaic cell production and a control system thereof
By employing a five-step diffusion process and a cryogenic gas pumping mechanism, the balance between production efficiency and cell conversion efficiency in cryogenic diffusion has been resolved, achieving efficient production and low-cost diffusion of photovoltaic cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 中润新能源(徐州)有限公司
- Filing Date
- 2023-09-25
- Publication Date
- 2026-06-30
AI Technical Summary
In existing polycrystalline silicon diffusion processes, although low-temperature diffusion improves the conversion efficiency of solar cells, it also prolongs the production time. The question is how to balance the control of temperature and production efficiency on the basis of low-temperature diffusion to optimize the short-wavelength response of solar cells.
A five-step diffusion process is adopted, including heating, low temperature and isothermal diffusion steps. By controlling the temperature and gas flow rate, and using nitrogen, oxygen and phosphorus oxychloride, the phosphorus concentration and dead layer thickness on the silicon wafer surface are optimized. The low temperature gas pumping mechanism and gas pipeline are used for rapid temperature control.
It improves the conversion efficiency of photovoltaic cells, simplifies the diffusion process, reduces gas usage and cost, and optimizes the shortwave response.
Smart Images
Figure CN117117040B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photovoltaic technology, specifically to the phosphorus diffusion process of polycrystalline silicon wafers in solar cell manufacturing, and more specifically to a phosphorus diffusion control process and control system for photovoltaic cell production. Background Technology
[0002] Current traditional polycrystalline silicon diffusion processes involve high temperatures and high flow rates of nitrogen and phosphorus oxychloride. This results in a high phosphorus concentration and a thick "dead layer" on the surface of the diffused silicon wafer, significantly reducing the short-wavelength response of the cell and leading to low conversion efficiency. To address this technical problem, existing patent 201110230914.3 provides a phosphorus diffusion process for polycrystalline silicon wafers, employing a ten-step diffusion process and utilizing low-temperature diffusion to improve the cell's conversion efficiency.
[0003] However, while low-temperature diffusion can protect the diffusion furnace to some extent, extend its service life, reduce electricity consumption, and lower the processing cost of solar cells, the extended time due to the lower temperature also restricts production efficiency. Nevertheless, this low-temperature diffusion approach is still worth learning from and adopting, but a more scientific diffusion method is needed that can both meet production efficiency requirements and improve the conversion efficiency of the solar cells.
[0004] Therefore, how to provide a phosphorus diffusion control process and control system for photovoltaic cell production that can balance temperature and production efficiency based on low-temperature diffusion is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] In view of this, the present invention provides a phosphorus diffusion control process and control system for photovoltaic cell production, aiming to solve the above-mentioned technical problems.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A phosphorus diffusion control process for photovoltaic cell production includes:
[0008] Step 1: Heating and diffusion: Nitrogen gas is introduced, and the diffusion time is 800-1000 seconds. The temperature in the furnace is gradually increased from 800℃ to 900℃.
[0009] The second step is low-temperature diffusion: low-temperature gas is introduced, along with nitrogen and oxygen, for a diffusion time of 300-400 seconds, while the furnace temperature is not lower than 800℃.
[0010] The third step is heating and diffusion: nitrogen, oxygen and phosphorus oxychloride are introduced, and the diffusion time is 800-1200s. The temperature in the furnace is gradually increased from the final temperature of the second step to 900℃.
[0011] Step 4: Low-temperature diffusion: Nitrogen and oxygen are introduced, the diffusion time is 800-1000 seconds, and the temperature in the furnace is not lower than 800℃;
[0012] Step 5: Constant temperature diffusion: Nitrogen gas is introduced, diffusion time is 800-1000s, and furnace temperature is 800℃ to 830℃.
[0013] Through the above technical solution, the phosphorus diffusion control process for photovoltaic cell production provided by this invention simplifies the process of low-temperature diffusion. By switching between heating and cooling, the diffusion temperature of the photovoltaic silicon wafer is adjusted. By utilizing temperature changes, nitrogen, oxygen, and phosphorus oxychloride are introduced in a coordinated manner. This not only overcomes the defect of high nitrogen and phosphorus oxychloride flow rates due to high temperatures, but also prevents high phosphorus concentration and thick "dead layer" on the surface of the diffused silicon wafer, thus optimizing the short-wavelength response of the cell and further improving the conversion efficiency of the photovoltaic cell.
[0014] Preferably, in the phosphorus diffusion control process for photovoltaic cell production described above, in the first step of heating diffusion, the time taken to raise the furnace temperature from 800°C to 900°C is controlled within 500–600 seconds.
[0015] Preferably, in the phosphorus diffusion control process for photovoltaic cell production described above, the temperature of the low-temperature gas introduced in the second step of low-temperature diffusion is 10 to 20°C.
[0016] Preferably, in the phosphorus diffusion control process for photovoltaic cell production described above, in the third step of heating diffusion, the time taken to raise the temperature to 900°C is controlled within 500–800 seconds.
[0017] Preferably, in the phosphorus diffusion control process for photovoltaic cell production described above, the furnace temperature is 800–850°C in the fourth step of low-temperature diffusion.
[0018] Preferably, in the phosphorus diffusion control process for photovoltaic cell production described above, in the first step of heating diffusion, the nitrogen flow rate is 50,000–70,000 ml; in the second step of low-temperature diffusion, the nitrogen flow rate is 8,000–9,000 ml and the oxygen flow rate is 800–1,200 ml; in the third step of heating diffusion, the nitrogen flow rate is 6,000–8,000 ml, the phosphorus oxychloride flow rate is 1,200–1,400 ml, and the oxygen flow rate is 600–800 ml; in the fourth step of low-temperature diffusion, the nitrogen flow rate is 700–900 ml and the oxygen flow rate is 1,500–3,000 ml; and in the fifth step of isothermal diffusion, the nitrogen flow rate is 50,000–70,000 ml.
[0019] The present invention also provides a control system for phosphorus diffusion control process in photovoltaic cell production, including a furnace body, a diffusion furnace chamber inside the furnace body, a process gas pipeline at the tail end of the diffusion furnace chamber, a waste discharge pipe, a thermocouple and a low-temperature gas pipeline inside the diffusion furnace chamber; and a low-temperature gas pumping mechanism connected to the low-temperature gas pipeline is provided on the outside of the furnace body.
[0020] Through the above technical solutions, the control system provided by the present invention can meet the heating requirements on the basis of conventional diffusion process, and can also control the cooling by introducing low temperature gas through low temperature gas pumping mechanism and low temperature gas pipeline, so as to quickly adjust the temperature inside the furnace. At the same time, it can reduce the flow rate to prevent the problem of thick "dead layer" caused by excessive flow rate. The present invention has a simple structure and can effectively cooperate with the diffusion process for control.
[0021] Preferably, in the control system of the phosphorus diffusion control process for photovoltaic cell production described above, the cryogenic gas pipeline is arranged in the upper part of the inner cavity of the diffusion furnace, and the cryogenic gas pipeline has multiple gas outlets, all of which face upwards. Utilizing the principle of cold air sinking, the temperature can be rapidly reduced, and the upward-facing gas outlets prevent disturbance to the airflow within the furnace.
[0022] Preferably, in the control system of the phosphorus diffusion control process for photovoltaic cell production described above, the waste discharge pipe and the thermocouple are arranged in the lower part of the inner cavity of the diffusion furnace. The thermocouple can detect and monitor the temperature inside the furnace.
[0023] Preferably, in the control system of the phosphorus diffusion control process in the above-mentioned photovoltaic cell production, the cryogenic gas pumping mechanism is a combination of a gas pump and a cooler. The cryogenic gas pumping mechanism can be achieved by using an air conditioning refrigeration unit in conjunction with the gas pump.
[0024] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a phosphorus diffusion control process and control system for photovoltaic cell production, which has the following beneficial effects:
[0025] 1. The phosphorus diffusion control process for photovoltaic cell production provided by this invention simplifies the process of low-temperature diffusion. By switching between heating and cooling, the diffusion temperature of the photovoltaic silicon wafer is adjusted. By utilizing temperature changes, nitrogen, oxygen, and phosphorus oxychloride are introduced in a coordinated manner. This not only overcomes the defect of high nitrogen and phosphorus oxychloride flow rates due to high temperatures, but also prevents high phosphorus concentration and thick "dead layer" on the surface of the diffused silicon wafer. This optimizes the short-wavelength response of the cell and further improves the conversion efficiency of the photovoltaic cell.
[0026] 2. The control system provided by the present invention can use the furnace body for heating during the diffusion process, and can also control the cooling by introducing low-temperature gas through a low-temperature gas pumping mechanism and a low-temperature gas pipeline, so as to quickly adjust the temperature inside the furnace. The structure is simple and can effectively cooperate with the diffusion process for control.
[0027] 3. The phosphorus diffusion control process for photovoltaic cell production provided by this invention saves electrical energy, reduces the flow rate of process gases, and lowers costs. Attached Figure Description
[0028] 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.
[0029] Figure 1 The attached figure is a flow chart of the phosphorus diffusion control process for photovoltaic cell production provided by the present invention.
[0030] Figure 2 The attached figure is a component layout diagram of the control system for the phosphorus diffusion control process in photovoltaic cell production provided by the present invention.
[0031] Figure 3 The attached figure is an exploded view of the control system of the phosphorus diffusion control process for photovoltaic cell production provided by the present invention.
[0032] Figure 4 The attached figure is a schematic diagram of the structure of the cryogenic gas pipeline provided by the present invention;
[0033] in:
[0034] 1-Diffusion furnace chamber; 2-Process gas pipeline; 3-Waste discharge pipe; 4-Thermocouple; 5-Cryogenic gas pipeline; 6-Cryogenic gas pumping mechanism; 7-Gas outlet. Detailed Implementation
[0035] 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.
[0036] This invention discloses a phosphorus diffusion control process for photovoltaic cell production, comprising:
[0037] Step 1: Heating and diffusion: Nitrogen gas is introduced, and the diffusion time is 800-1000 seconds. The temperature in the furnace is gradually increased from 800℃ to 900℃.
[0038] The second step is low-temperature diffusion: low-temperature gas is introduced, along with nitrogen and oxygen, for a diffusion time of 300-400 seconds, while the furnace temperature is not lower than 800℃.
[0039] The third step is heating and diffusion: nitrogen, oxygen and phosphorus oxychloride are introduced, and the diffusion time is 800-1200s. The temperature in the furnace is gradually increased from the final temperature of the second step to 900℃.
[0040] Step 4: Low-temperature diffusion: Nitrogen and oxygen are introduced, the diffusion time is 800-1000 seconds, and the temperature in the furnace is not lower than 800℃;
[0041] Step 5: Constant temperature diffusion: Nitrogen gas is introduced, diffusion time is 800-1000s, and furnace temperature is 800℃ to 830℃.
[0042] To further optimize the above technical solution, the time required to raise the furnace temperature from 800℃ to 900℃ was controlled within 500-600 seconds.
[0043] To further optimize the above technical solution, the temperature of the introduced low-temperature gas is between 10 and 20°C.
[0044] To further optimize the above technical solution, the time required to raise the temperature to 900℃ is controlled within 500-800 seconds.
[0045] To further optimize the above technical solution, the furnace temperature is 800-850℃.
[0046] To further optimize the above technical solution, the nitrogen flow rate is 50,000–70,000 ml; in the second step of low-temperature diffusion, the nitrogen flow rate is 8,000–9,000 ml, and the oxygen flow rate is 800–1,200 ml; in the third step of heating diffusion, the nitrogen flow rate is 6,000–8,000 ml, the phosphorus oxychloride flow rate is 1,200–1,400 ml, and the oxygen flow rate is 600–800 ml; in the fourth step of low-temperature diffusion, the nitrogen flow rate is 700–900 ml, and the oxygen flow rate is 1,500–3,000 ml; and in the fifth step of isothermal diffusion, the nitrogen flow rate is 50,000–70,000 ml.
[0047] The control system for phosphorus diffusion control process in photovoltaic cell production provided in this embodiment includes a furnace body, a diffusion furnace chamber 1 inside the furnace body, a process gas pipeline 2 at the tail of the diffusion furnace chamber 1, a waste discharge pipe 3, a thermocouple 4 and a low-temperature gas pipeline 5 inside the diffusion furnace chamber 1; and a low-temperature gas pumping mechanism 6 connected to the low-temperature gas pipeline 5 is provided on the outside of the furnace body.
[0048] To further optimize the above technical solution, the cryogenic gas pipeline 5 is arranged in the upper part of the inner cavity of the diffusion furnace 1, and multiple gas outlets 7 are opened on the cryogenic gas pipeline 5, with the gas outlets 7 facing upward.
[0049] To further optimize the above technical solution, the waste discharge pipe 3 and the thermocouple 4 are arranged in the lower part of the inner cavity of the diffusion furnace 1.
[0050] To further optimize the above technical solution, the cryogenic gas pumping mechanism 6 is a combination structure of a gas pump and a refrigerator.
[0051] Example 1:
[0052] Step 1: Heating and diffusion: Nitrogen gas is introduced at a rate of 50,000 ml; diffusion time is 800 s, and the furnace temperature is gradually increased from 800 ℃ to 900 ℃ within 500 s.
[0053] The second step is low-temperature diffusion: introduce a 20°C low-temperature gas, and introduce nitrogen and oxygen. The amount of nitrogen introduced is 8000ml, and the amount of oxygen introduced is 800ml; the diffusion time is 300s, and the temperature in the furnace is not lower than 800°C.
[0054] The third step is heating and diffusion: nitrogen, oxygen and phosphorus oxychloride are introduced. The amount of nitrogen introduced is 6000ml, the amount of phosphorus oxychloride introduced is 1200ml, and the amount of oxygen introduced is 600ml; the diffusion time is 800s, and the temperature in the furnace gradually increases from the final temperature of the second step to 900℃ in 500s.
[0055] Step 4: Low-temperature diffusion: Nitrogen and oxygen are introduced, with a nitrogen flow rate of 700 ml and an oxygen flow rate of 1500 ml; the diffusion time is 800 s, and the furnace temperature is not lower than 800℃.
[0056] Step 5: Constant temperature diffusion: Nitrogen gas is introduced at a rate of 50,000 ml; diffusion time is 800 s; furnace temperature is 800 ℃.
[0057] The sheet resistance of the photovoltaic silicon wafer in this embodiment is 55Ω after diffusion.
[0058] Example 2:
[0059] Step 1: Heating and diffusion: Nitrogen gas is introduced at a rate of 70,000 ml; diffusion time is 1000 s; the furnace temperature is gradually increased from 800 ℃ to 900 ℃ within 600 s.
[0060] The second step is low-temperature diffusion: a 10°C low-temperature gas is introduced, along with nitrogen and oxygen. The amount of nitrogen introduced is 9000ml, and the amount of oxygen introduced is 1200ml. The diffusion time is 400s, and the temperature in the furnace is not lower than 800°C.
[0061] The third step is heating and diffusion: nitrogen, oxygen and phosphorus oxychloride are introduced. The amount of nitrogen introduced is 8000 ml, the amount of phosphorus oxychloride introduced is 1400 ml, and the amount of oxygen introduced is 800 ml; the diffusion time is 1200 s, and the temperature in the furnace gradually increases from the final temperature of the second step at 800 s to 900 ℃.
[0062] Step 4: Low-temperature diffusion: Nitrogen and oxygen are introduced, with a nitrogen flow rate of 900 ml and an oxygen flow rate of 3000 ml; the diffusion time is 1000 s, and the furnace temperature is not lower than 800℃.
[0063] Step 5: Constant temperature diffusion: Nitrogen gas is introduced at a rate of 70,000 ml; diffusion time is 1000 s; furnace temperature is 830 ℃.
[0064] The sheet resistance of the photovoltaic silicon wafer in this embodiment is 60Ω after diffusion.
[0065] 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 they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.
[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A phosphorus diffusion control process for photovoltaic cell production, characterized in that, include: Step 1: Heating and diffusion: Nitrogen gas is introduced, and the diffusion time is 800~1000s. The temperature in the furnace is gradually increased from 800℃ to 900℃. The second step is low-temperature diffusion: low-temperature gas is introduced, along with nitrogen and oxygen, for a diffusion time of 300-400 seconds, while the furnace temperature is not lower than 800℃. The third step is heating and diffusion: nitrogen, oxygen and phosphorus oxychloride are introduced, and the diffusion time is 800~1200s. The temperature in the furnace is gradually increased from the final temperature of the second step to 900℃. Step 4: Low-temperature diffusion: Nitrogen and oxygen are introduced, diffusion time is 800~1000s, and the temperature in the furnace is not lower than 800℃; Step 5: Isothermal diffusion: Nitrogen gas is introduced, diffusion time is 800~1000s, furnace temperature is 800℃ to 830℃; In the first step of heating diffusion, the nitrogen flow rate is 50,000~70,000 ml; in the second step of low-temperature diffusion, the nitrogen flow rate is 8,000~9,000 ml and the oxygen flow rate is 800~1,200 ml; in the third step of heating diffusion, the nitrogen flow rate is 6,000~8,000 ml, the phosphorus oxychloride flow rate is 1,200~1,400 ml, and the oxygen flow rate is 600~800 ml; in the fourth step of low-temperature diffusion, the nitrogen flow rate is 700~900 ml and the oxygen flow rate is 1,500~3,000 ml; and in the fifth step of isothermal diffusion, the nitrogen flow rate is 50,000~70,000 ml.
2. The phosphorus diffusion control process for photovoltaic cell production according to claim 1, characterized in that, In the first step of heating and diffusion, the time taken to raise the furnace temperature from 800℃ to 900℃ is controlled within 500~600s.
3. The phosphorus diffusion control process for photovoltaic cell production according to claim 1, characterized in that, In the second step of low-temperature diffusion, the temperature of the introduced low-temperature gas is 10~20℃.
4. The phosphorus diffusion control process for photovoltaic cell production according to claim 1, characterized in that, In the third step of heating and diffusion, the time taken to raise the temperature to 900℃ is controlled within 500~800s.
5. The phosphorus diffusion control process for photovoltaic cell production according to claim 1, characterized in that, In the fourth step of low-temperature diffusion, the furnace temperature is 800~850℃.
6. A control system for the phosphorus diffusion control process in the production of photovoltaic cells according to any one of claims 1-5, characterized in that, The furnace includes a furnace body, which is equipped with a diffusion furnace chamber (1). The diffusion furnace chamber (1) has a process gas pipeline (2) at its tail end. The diffusion furnace chamber (1) is equipped with a waste discharge pipe (3), a thermocouple (4), and a low-temperature gas pipeline (5). The furnace body is equipped with a low-temperature gas pumping mechanism (6) connected to the low-temperature gas pipeline (5) on its outer side.
7. The control system for phosphorus diffusion control process in photovoltaic cell production according to claim 6, characterized in that, The cryogenic gas pipeline (5) is arranged in the upper part of the inner cavity of the diffusion furnace (1), and multiple gas outlets (7) are provided on the cryogenic gas pipeline (5), with the gas outlets (7) facing upward.
8. The control system for phosphorus diffusion control process in photovoltaic cell production according to claim 6, characterized in that, The waste discharge pipe (3) and the thermocouple (4) are arranged in the lower part of the inner cavity of the diffusion furnace (1).
9. The control system for phosphorus diffusion control process in photovoltaic cell production according to claim 6, characterized in that, The cryogenic gas pumping mechanism (6) is a combination structure of a gas pump and a refrigerator.