Method for preparing battery emitter and application thereof

Abstract

The invention belongs to the technical field of photovoltaics, and particularly relates to a method for preparing a battery emitter electrode and application thereof.The method comprises the steps that in an inert gas environment, a silicon wafer coated with a boric acid aqueous solution is heated, and a silicon wafer with the surface being boric oxide is obtained; carrying out boron atom substitution diffusion on the silicon wafer of which the surface is boron oxide to finish boron diffusion; according to the diffusion method, toxic BBr3 is prevented from being generated in the boron diffusion process, and the uniformity of the boron source on the surface of the silicon wafer is ensured; by adopting a solution spin-coating or spraying process, the uniformity of the boron source on the surface of the silicon wafer can be ensured, so that the phenomenon that the boron source is carried by nitrogen to cause a patterned wafer is avoided. A specific temperature programming mode is adopted, so that the stability and uniformity of crystallization of boric acid from an aqueous solution can be ensured; by adopting a novel process, B2O3 can be prevented from being deposited in a tubular furnace, and the influence of B2O3 on equipment is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaics, and in particular relates to a method for preparing a battery emitter and an application thereof. Background Art

[0002] Solar energy is a clean and renewable energy source. The technology of using solar photovoltaic power generation is relatively mature. Among them, the important component of solar photovoltaic power generation - crystalline silicon solar cells, is the dominant product in the photovoltaic cell market. At present, most of the crystalline silicon solar cells on the market are p-type single and multi-crystalline conventional aluminum back surface field cells, which are relatively simple to prepare and low in cost. However, due to the photo-induced degradation problem of p-type silicon materials, the photoelectric conversion efficiency of this cell is relatively low, generally not exceeding 22%. Relatively speaking, the solar cells based on n-type silicon wafers have a higher lifespan of minority carriers, a higher tolerance to metals such as Fe, and are less likely to have LID (Light Induced Degradation) phenomenon. In addition, the conversion efficiency of the cells based on n-type silicon wafers is higher, and the manufacturing cost for photovoltaic power generation is lower. The solar cells based on n-type silicon wafers have more economic advantages.

[0003] At present, there are four main types of industrialized structural cells using n-type silicon wafers as substrates, namely n-IBC, n-HIT, n-PERT and n-TOPCon. Whether it is TOPCon or IBC cells, the electrical properties of the surface pn junction are the key to affecting the efficiency of the cell. The schematic diagram of the IBC cell structure is shown in Figure 1 The preparation of the pn junction is as follows: p-type impurities are doped into the n-type semiconductor so that part of the crystalline silicon is the p-type region and the other part is the n-type region, thereby achieving contact between the p-type semiconductor and the n-type semiconductor to form a pn junction. Boron diffusion is required in the preparation of the pn junction.

[0004] The existing boron diffusion process is generally divided into two steps. The first step is pre-deposition: first, a small flow of nitrogen carrying gaseous BBr3 enters the reaction chamber, and then a large flow of N2 carrying oxygen is introduced. The two react with each other to produce liquid B2O3. The gas flows to the end of the tube, and at the same time, the liquid B2O3 adheres to the surface of the silicon wafer. The second step is propulsion: at high temperature, B2O3 as a boron source reacts chemically with Si to generate B atoms, and then diffuses to the surface of the silicon wafer. The chemical reactions are as follows: BBr3+O2→B2O3+Br2; Si+O2→SiO2; B2O3+Si→B+SiO2. However, the above process has the following disadvantages: (1) The B2O3 generated by the reaction of BBr3 and oxygen is liquid. The temperature required to convert the liquid into gas is 1860°C, while the propulsion temperature is 900-1000°C. In order to distribute the liquid on the surface of the silicon wafer, a large amount of gas is required to assist in turning the liquid into small droplets. (2) Due to the effect of gravity, B2O3 is mainly deposited at the bottom of the diffusion furnace, and only a small part can be deposited on the surface of the silicon wafer. Even if it is deposited on the surface of the silicon wafer, due to the effect of gravity, the B2O3 on the surface of the silicon wafer will be uneven, resulting in uneven B doping. The surface phenomenon caused by this uneven doping is uneven color on the surface of the silicon wafer. (3) Due to the length-to-diameter ratio of the tubular equipment, the diffusion movement is also irregular, which makes the doping of the wafer sources at different positions in the diffusion furnace (before the tube, in the tube, and at the end of the tube) different. (4) During the diffusion process, B2O3 is easy to gather near the exhaust pipe at the end of the furnace due to its high boiling point. When the temperature is low, it is easy to cool and crystallize, thereby blocking the pipe. In severe cases, it causes gas discharge in the pipe. (5) During the diffusion process, B2O3 is easy to cool and crystallize due to its high boiling point. When the temperature is low, it is easy to cool and crystallize, resulting in glue connection between the furnace tube components, making the valve of the quartz path unable to open, affecting production efficiency. (6) It consumes a large amount of gas and auxiliary equipment, and the equipment investment is large.

[0005] In summary, it is particularly important to design a method for preparing a boron diffused emitter that can improve the uniformity within and between wafers, while reducing the use of gas and reducing production costs. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a battery emitter and its application. This method comprises heating a silicon wafer coated with a boric acid aqueous solution in an inert gas environment to obtain a silicon wafer with a surface of boron oxide; performing substitution diffusion of boron atoms on the silicon wafer with a surface of boron oxide; and the above diffusion method avoids the generation of toxic BBr3 during the boron diffusion process and ensures the uniformity of the boron source on the surface of the silicon wafer.

[0007] In order to achieve the above objectives, this application provides the following technical solutions:

[0008] A method for preparing a battery emitter comprises the following steps:

[0009] In an inert gas environment, the silicon wafer coated with the boric acid solution is heated in a range of 0-350° C. to obtain a silicon wafer with a surface of boron oxide;

[0010] Boron diffusion is completed by performing substitution diffusion of boron atoms on a silicon wafer with a boron oxide surface.

[0011] Furthermore, the boric acid solution is an aqueous boric acid solution, and heating the silicon wafer coated with the aqueous boric acid solution includes: precipitating boric acid crystals by high temperature and dehydrating the boric acid crystals by high temperature to generate boron oxide.

[0012] Further, the precipitation of boric acid crystals comprises the following steps:

[0013] Raise the temperature to 40-60°C and keep the temperature for 60-100 minutes to pre-evaporate the water;

[0014] After the pre-evaporation is completed, the temperature is raised to 90-100° C. for 60-100 minutes until the boric acid crystals are completely precipitated.

[0015] Furthermore, the dehydration of the boric acid crystals to generate boron oxide includes a thermal decomposition reaction of boric acid, a thermal decomposition reaction of metaboric acid, and a thermal decomposition reaction of pyroboric acid;

[0016] The boric acid thermal decomposition reaction step is to raise the temperature to 105° C.-110° C. after the boric acid crystals are precipitated, and maintain the temperature for 30 min-45 min, the boric acid crystals undergo a boric acid dehydration reaction to generate metaboric acid, and the temperature is maintained for 30 min-45 min;

[0017] Preferably, the metaboric acid thermal decomposition reaction step is: after the boric acid thermal decomposition reaction is completed, the temperature is raised to 140-160° C., the metaboric acid undergoes a metaboric acid dehydration reaction to generate pyroboric acid, and the temperature is maintained for 30 min-45 min;

[0018] Preferably, the step of thermal decomposition reaction of pyroboric acid is that after the thermal decomposition reaction of metaboric acid is completed, the temperature is raised to 280-320° C., pyroboric acid is thermally decomposed to obtain boron oxide, and the temperature is maintained for 30 min-45 min.

[0019] Furthermore, the mass fraction of the boric acid solution is 5%-50%.

[0020] Furthermore, before coating the silicon wafer with the boric acid aqueous solution, the following silicon wafer processing steps are also included:

[0021] Silicon wafer pretreatment: remove damage and stains from n-type silicon wafers, and then soak them in KOH solution;

[0022] Silicon wafer texturing: Mix the pre-treated silicon wafer with KOH and texturing additives to make texturing;

[0023] Silicon wafer post-processing: The silicon wafer that has completed silicon wafer texturing is cleaned with HCl and HF, and dried in an inert gas atmosphere to complete the silicon wafer processing.

[0024] Furthermore, the silicon wafer is pretreated by soaking in a 20-30% KOH solution for 300s-400s at a temperature of 40-60°C.

[0025] Preferably, the KOH concentration in the silicon wafer texturing is 1%-5%, the texturing additive is 1‰-5‰, the time is 600-800s, and the texturing temperature is 60-80°C;

[0026] Preferably, in the silicon wafer post-treatment, the HCl concentration is 1%-3%, the HF concentration is 2%-4%, the cleaning time is 400s-600s, and the cleaning temperature is 25°C.

[0027] Furthermore, the silicon wafer with the boron oxide surface is subjected to substitution diffusion of boron atoms in a diffusion furnace, the temperature of the diffusion furnace is 900-1000° C., and the time is 15 min-40 min.

[0028] The present invention also protects a battery emitter, which is prepared by the above method.

[0029] The present invention also protects a battery comprising the battery emitter as claimed in claim 9.

[0030] The present invention also provides a method for boron diffusion of an IBC solar cell, comprising the following steps:

[0031] Step 1: Pre-prepare a boric acid aqueous solution of a certain concentration;

[0032] Step 2: Spray or spin-coat the new boron source on the surface of the silicon wafer;

[0033] Step 3: The silicon wafer enters a heating furnace with programmable temperature rise to complete the process of converting boric acid to boron oxide;

[0034] Step 4: Promote diffusion and complete the substitution diffusion of B atoms;

[0035] Step 5: Cool down and take out the silicon wafer.

[0036] A further technical solution is to use liquid boric acid as a liquid boron source, so that the boron source on the surface of the silicon wafer can be evenly distributed.

[0037] In a further technical solution, the mass fraction of the boric acid in step 2 is 5%-50%, and the mass fraction of the boric acid can be adjusted according to the surface concentration of the silicon wafer after boron diffusion.

[0038] Further technical solutions, in step three, a heating furnace with programmable temperature rise is used, and the program temperature rise can complete the accurate temperature control of 0-300°C. The silicon wafer after spraying enters the heating furnace with programmable temperature control. The initial temperature of the heating furnace is 50°C, and the water is pre-evaporated at this temperature. The heating time is 60min-100min. After that, the temperature is raised to 100°C, and during this period, boric acid crystals are precipitated to the surface of the silicon wafer. When the temperature is raised to 105°C, the boric acid crystals lose 1 molecule of water to form metaboric acid, which is maintained for 30min. Continue to heat up to 150°C and become pyroboric acid, which is maintained for 30min. Continue to heat up to 300°C, maintain the temperature for 30min, and pyroboric acid becomes boron oxide. Further technical solutions, the nitrogen flow rate introduced in step three is 5L / min-20L / min. The introduction time is 15min-60min.

[0039] According to a further technical solution, in step 4, the temperature of the diffusion furnace is 900°C-1000°C.

[0040] The present invention has the following beneficial effects: the boron diffusion method of the present application adopts an aqueous solution of boric acid as a boron source, thereby avoiding the use of toxic gas BBr3; the solution method spin coating or spraying process is adopted to ensure the uniformity of the boron source on the surface of the silicon wafer, thereby avoiding flower chips caused by nitrogen carrying the boron source; the boron diffusion method of the present application adopts a specific programmed heating mode, thereby ensuring the stability and uniformity of the crystallization of boric acid from the aqueous solution; the boron diffusion method of the present application avoids the deposition of B2O3 in a tubular furnace, thereby reducing the impact of B2O3 on the equipment; the boron diffusion method of the present application does not require oxygen gas flow, thereby better increasing the stability of the process; the use of the boron diffusion method of the present application can reduce the investment in equipment, thereby reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a schematic diagram of the IBC battery in this application;

[0043] Figure 2 This is a boron diffusion process flow chart of Comparative Example 1 in the specific implementation manner of this application;

[0044] Figure 3 This is the IBC battery efficiency distribution diagram in Comparative Example 1 in the specific implementation manner of this application;

[0045] Figure 4This is the IBC battery efficiency distribution diagram in Example 1 in the specific implementation manner of this application. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] In the embodiment of the present application, the boron diffusion comprises the following steps:

[0048] A boric acid aqueous solution of a certain concentration is prepared in advance.

[0049] Spray or spin-coat the boric acid aqueous solution on the surface of the silicon wafer.

[0050] The silicon wafer enters a programmable temperature heating furnace to complete the process of converting boric acid to boron oxide.

[0051] Promote diffusion and complete the replacement diffusion of B atoms.

[0052] Example 1

[0053] Step 1: Pretreatment process: The n-type silicon wafer is subjected to a process of removing damage and stains by soaking in a 20% KOH solution for 300 seconds at a temperature of 40°C.

[0054] Step 2: Texturing process: The silicon wafer is placed in an alkaline washing tank for polishing, the formula is: KOH concentration is 5%, texturing additive is 5‰, the time is 600s, and the temperature is 80°C.

[0055] Step 3: Post-treatment process: The silicon wafer is cleaned with HCl and HF, with the HCl concentration being 1% and the HF concentration being 2%, for 400 seconds and the temperature being 25°C.

[0056] Step 4: Drying: Dry the material under a nitrogen atmosphere.

[0057] Step 5: Place the dried silicon wafers on a chain conveyor belt for later use.

[0058] Step 6: Pre-prepare a boric acid aqueous solution of a certain concentration. The mass fraction of boric acid can be adjusted according to the ECV curve. In this embodiment, the mass fraction of boric acid in the boric acid aqueous solution is 30%.

[0059] Step 7: Nitrogen is introduced into the programmable heating furnace and push furnace in advance to exhaust the air in the furnace.

[0060] Step 8: Pressurize a 30% boric acid aqueous solution into the spray device.

[0061] Step 9: Start the conveyor belt, turn on the spray device, and spray the boric acid solution evenly on the surface of the silicon wafer

[0062] Step 10: After being sprayed, the silicon wafer enters a programmable temperature-controlled heating furnace with an initial temperature of 40°C. The water is pre-evaporated at this temperature for 60 minutes. The temperature is then raised to 90°C, during which time boric acid crystals are precipitated on the surface of the silicon wafer for 80 minutes. The temperature is then raised to 105°C, and the boric acid crystals lose one molecule of water to form metaboric acid, which is maintained for 30 minutes. The temperature is then raised to 140°C, maintained for 30 minutes, and converted into pyroboric acid. The temperature is finally raised to 280°C, maintained for 30 minutes, and pyroboric acid is converted into boric oxide. The chemical reactions that occur in this process are as follows;

[0063] Metaboric acid generation: H3BO3→HBO2+H2O;

[0064] Pyroboric acid generation: 4HBO2→H2B4O7+H2O;

[0065] Boron oxide production: H2B4O7→2B2O3+H2O.

[0066] Step 11: After the boron oxide is formed, it is passed through a diffusion furnace at a temperature of 900° C. for 15 minutes.

[0067] Step 12: Cool down, take out the silicon wafer, and get the silicon wafer p + Emitter, complete the test. Silicon wafer p + The square resistance of the emitter is shown in Table 1 (nine-point probe test).

[0068] Table 1

[0069] Point 1 Point 2 Point 3 Point 4 Point 5 Point 6 Point 7 Point 8 Point 9 average 91 89 93 87 95 85 94 86 90 90±5

[0070] Step 13: Remove BSG; remove the borosilicate glass oxide layer on the silicon wafer surface using HF solution

[0071] Step 14: SiN x Mask; through PECVD equipment, a layer of SiN is deposited on the surface of the silicon wafer under the ratio of silane and ammonia x Mask.

[0072] Step 15: Grooving: Grooving the silicon wafer using laser.

[0073] Step 16: Texturing: Texturing the silicon wafer using a trough-type device.

[0074] Step 17: Phosphorus diffusion: Through the phosphorus diffusion process, a layer of high-low junction is formed on the surface of the silicon wafer.

[0075] Step 18: Remove PSG; remove the phosphorus silicon glass oxide layer on the silicon wafer surface by HF solution

[0076] Step 19: SiN x Anti-reflection layer: A layer of silicon nitride anti-reflection layer is coated on both sides of the silicon wafer using PECVD equipment.

[0077] Step 20: Screen printing: forming electrodes on the surface of the silicon wafer through screen printing and sintering;

[0078] PSG is phosphosilicate glass, SiN x For silicon nitride, the IBC cell efficiency distribution is shown in Figure 4 .

[0079] Example 2

[0080] Step 1: Pretreatment process: The n-type silicon wafer is subjected to a process of removing damage and stains by soaking in a 30% KOH solution for 400 seconds at a temperature of 60°C.

[0081] Step 2: Texturing process: The silicon wafer is placed in a texturing tank for texturing. The texturing formula is: KOH concentration is 5%, texturing additive is 5‰, time is 800s, and texturing temperature is 80℃.

[0082] Step 3: Post-treatment process: The silicon wafer is cleaned with HCl and HF, with the HCl concentration being 1%-3% and the HF concentration being 4%, for 600 seconds and the temperature being 25°C.

[0083] Step 4: Drying: Dry the material under a nitrogen atmosphere.

[0084] Step 5: Place the dried silicon wafers on a chain conveyor belt for later use.

[0085] Step 6: Pre-prepare a boric acid aqueous solution of a certain concentration. The mass fraction of boric acid can be adjusted according to the ECV curve. In this embodiment, the mass fraction of boric acid in the boric acid aqueous solution is 50%.

[0086] Step 7: Nitrogen is introduced into the programmable heating furnace and push furnace in advance to exhaust the air in the furnace.

[0087] Step 8: Pressurize a 50% boric acid aqueous solution into the spray device.

[0088] Step 9: Start the conveyor belt, turn on the spray device, and spray the boric acid solution evenly on the surface of the silicon wafer

[0089] Step 10: The sprayed silicon wafer enters a programmable temperature-controlled heating furnace with an initial temperature of 60°C. Water is pre-evaporated at this temperature for 100 minutes. The temperature is then raised to 100°C for 100 minutes. During this period, boric acid crystals precipitate on the surface of the silicon wafer. The temperature is then raised to 110°C, and the boric acid crystals lose one molecule of water to form metaboric acid, which is maintained for 30 minutes. The temperature is then raised to 160°C and maintained for 30 minutes to be converted into pyroboric acid. Finally, the temperature is raised to 320°C and maintained for 30 minutes, and the pyroboric acid is converted into boric oxide.

[0090] Step 11: After the boron oxide is formed, it is passed through a diffusion furnace with a temperature of 1000° C. and a time of 40 minutes.

[0091] Step 12: Cool down, take out the silicon wafer, complete the test, and get the p + Emitter.

[0092] Step 13: Remove BSG; remove the borosilicate glass oxide layer on the silicon wafer surface using HF solution

[0093] Step 14: SiN x Mask; through PECVD equipment, a layer of SiN is deposited on the surface of the silicon wafer under the ratio of silane and ammonia x Mask.

[0094] Step 15: Grooving: Grooving the silicon wafer using laser.

[0095] Step 16: Texturing: Texturing the silicon wafer using a trough-type device.

[0096] Step 17: Phosphorus diffusion: Through the phosphorus diffusion process, a layer of high-low junction is formed on the surface of the silicon wafer.

[0097] Step 18: Remove PSG; remove the phosphorus silicon glass oxide layer on the silicon wafer surface by HF solution

[0098] Step 19: SiN x Anti-reflection layer: A layer of silicon nitride anti-reflection layer is coated on both sides of the silicon wafer using PECVD equipment.

[0099] Step 20: Screen printing: Electrodes are formed on the surface of the silicon wafer through screen printing and sintering.

[0100] Example 3

[0101] Step 1: Pretreatment process: The n-type silicon wafer is subjected to a process of removing damage and stains by soaking in a 20% KOH solution for 300 seconds at a temperature of 40°C.

[0102] Step 2: Texturing process: The silicon wafer is placed in a texturing tank for texturing. The texturing formula is: KOH concentration is 1%, texturing additive is 1‰, time is 600s, and texturing temperature is 60°C.

[0103] Step 3: Post-treatment process: The silicon wafer is cleaned with HCl and HF, with the HCl concentration being 1% and the HF concentration being 2%, for 400 seconds and the temperature being 25°C.

[0104] Step 4: Drying: Dry the material under a nitrogen atmosphere.

[0105] Step 5: Place the dried silicon wafers on the chain conveyor for later use

[0106] Step 6: Pre-prepare a boric acid aqueous solution of a certain concentration. The mass fraction of boric acid can be adjusted according to the ECV curve. In this embodiment, the mass fraction of boric acid in the boric acid aqueous solution is 5%.

[0107] Step 7: Nitrogen is introduced into the programmable heating furnace and push furnace in advance to exhaust the air in the furnace.

[0108] Step 8: Pressurize a 5% boric acid aqueous solution into the spray device.

[0109] Step 9: Start the conveyor belt, turn on the spray device, and spray the boric acid solution evenly on the surface of the silicon wafer

[0110] Step 10: The sprayed silicon wafer enters a programmable temperature-controlled heating furnace with an initial temperature of 50°C. The water is pre-evaporated at this temperature for 80 minutes. The temperature is then raised to 100°C for 80 minutes. During this period, boric acid crystals precipitate on the surface of the silicon wafer. The temperature is raised to 105°C, and the boric acid crystals lose one molecule of water to form metaboric acid, which is maintained for 30 minutes. The temperature is then raised to 150°C and maintained for 30 minutes to become pyroboric acid. Finally, the temperature is raised to 300°C and maintained for 30 minutes to convert pyroboric acid into boric oxide.

[0111] Step 11: After the boron oxide is formed, it is passed through a diffusion furnace at a temperature of 900° C. for 15 minutes.

[0112] Step 12: Cool down, take out the silicon wafer, complete the test, and get the p + Emitter.

[0113] Step 13: Remove BSG; remove the borosilicate glass oxide layer on the silicon wafer surface using HF solution

[0114] Step 14: SiN x Mask; through PECVD equipment, a layer of SiN is deposited on the surface of the silicon wafer under the ratio of silane and ammonia x Mask.

[0115] Step 15: Grooving: Grooving the silicon wafer using laser.

[0116] Step 16: Texturing: Texturing the silicon wafer using a trough-type device.

[0117] Step 17: Phosphorus diffusion: Through the phosphorus diffusion process, a layer of high-low junction is formed on the surface of the silicon wafer.

[0118] Step 18: Remove PSG; remove the phosphorus silicon glass oxide layer on the silicon wafer surface by HF solution

[0119] Step 19: SiN x Anti-reflection layer: A layer of silicon nitride anti-reflection layer is coated on both sides of the silicon wafer using PECVD equipment.

[0120] Step 20: Screen printing: Electrodes are formed on the surface of the silicon wafer through screen printing and sintering.

[0121] The texturing additive is IPA (isopropyl alcohol).

[0122] Comparative Example 1

[0123] Step 1: Pretreatment process: The n-type silicon wafer is subjected to a process of removing damage and stains by soaking in a 20% KOH solution for 300 seconds at a temperature of 40°C.

[0124] Step 2: Texturing process: The silicon wafer is put into alkaline washing for polishing, the formula is: KOH concentration is 5%, texturing additive is 5‰, the time is 600s, and the texturing temperature is 80℃.

[0125] Step 3: Post-treatment process: The silicon wafer is cleaned with HCl and HF, with the HCl concentration being 1% and the HF concentration being 2%, the time being 400s, and the temperature being 25°C.

[0126] Step 4: The silicon wafer undergoes a boron diffusion process. Nitrogen is initially purged into the furnace tube, and the temperature is raised to 850°C for a leak test. Then, at 850°C, a boron source is passed through for 30 minutes. The boron source is boron trichloride, and a certain proportion of oxygen is added for pre-deposition. Then the temperature is raised to 980°C for aerobic advancement, and finally the temperature is lowered and the process is exited to obtain a silicon wafer. + Emitter.

[0127] Step 5: Go to PSG, SiN x , texturing, phosphorus diffusion, PSG removal, SiN plating x , screen printing, IBC battery, using traditional high temperature boron diffusion, traditional high temperature B diffusion, silicon wafer p + The square resistance of the emitter is shown in Table 2 (nine-point probe test).

[0128] Table 2

[0129] Point 1 Point 2 Point 3 Point 4 Point 5 Point 6 Point 7 Point 8 Point 9 average 91 89 97 83 100 80 95 85 90 90±10

[0130] Comparative Example 1 Conventional high temperature boron diffusion process diagram Figure 2 .

[0131] Comparative Example + The IBC cell efficiency of the emitter is shown in Figure 3 .

[0132] Depend on Figure 4 and Figure 3 Visible comparison

[0133] Example 1 Preparation of p + The average efficiency of the emitter is better than that of the p prepared in Comparative Example 1. + The emitter, and the lowest efficiency in Example 1 (23.64%) is significantly greater than that in Comparative Example 1 (23.51%).

[0134] Comparison between Table 1 and Table 2 shows that in Example 1, p + The upper and lower error values ​​of the emitter's square resistance are smaller than those in comparative example 1. + The upper and lower error values ​​of the emitter's square resistance.

[0135] Comparative Example 2

[0136] The only difference between Comparative Example 2 and Example 1 is that the mass fraction of boric acid in the boric acid solution is 3%, and the other preparation methods and conditions are consistent with those of Example 1.

[0137] The silicon wafer p obtained in Comparative Example 2 + Emitter detection, silicon wafer p + The square resistance of the emitter is shown in Table 3. The square resistance value error is large and the square resistance value is not within the standard range.

[0138] Table 3

[0139] Point 1 Point 2 Point 3 Point 4 Point 5 Point 6 Point 7 Point 8 Point 9 average 160 140 170 174 130 190 211 150 180 167±23

[0140] Comparative Example 3

[0141] The only difference between Comparative Example 2 and Example 1 is that the mass fraction of boric acid in the boric acid solution is 55%, and the other preparation methods and conditions are consistent with those of Example 1.

[0142] When carrying out the preparation method of comparative example 3, it is found that a boron-rich layer is formed on the silicon wafer, which has a great influence on the safety and stability of the battery.

Claims

1. A method for preparing a battery emitter, comprising the following steps: In an inert gas environment, the silicon wafer coated with the boric acid solution is heated in a range of 0-350° C. to obtain a silicon wafer with a surface of boron oxide; Boron diffusion is completed by performing substitution diffusion of boron atoms on a silicon wafer with a boron oxide surface.

2. The method according to claim 1, characterized in that The boric acid solution is boric acid solution water, and the step of heating the silicon wafer coated with the boric acid solution includes: precipitating boric acid crystals and dehydrating the boric acid crystals.

3. The method according to claim 2, characterized in that Precipitating boric acid crystals comprises the following steps: Raise the temperature to 40-60°C and keep the temperature for 60-100 minutes to pre-evaporate the water; After the pre-evaporation is completed, the temperature is raised to 90-100° C. for 60-100 minutes until the boric acid crystals are completely precipitated.

4. The method according to claim 2, characterized in that: The dehydration of boric acid crystals includes the thermal decomposition reaction of boric acid, the thermal decomposition reaction of metaboric acid and the thermal decomposition reaction of pyroboric acid; The boric acid thermal decomposition reaction step is: after the boric acid crystals are precipitated, the temperature is raised to 105°C-110°C, maintained for 30min-45min, the boric acid crystals undergo a boric acid dehydration reaction to generate metaboric acid, and the temperature is maintained for 30min-45min; and\or, the step of thermal decomposition of metaboric acid is as follows: after the thermal decomposition of boric acid is completed, the temperature is raised to 140-160° C., metaboric acid undergoes metaboric acid dehydration reaction to generate pyroboric acid, and the temperature is maintained for 30 min-45 min; And\or, the step of thermally decomposing pyroboric acid is as follows: after the thermal decomposition reaction of metaboric acid is completed, the temperature is raised to 280-320° C., the pyroboric acid is thermally decomposed to obtain boron oxide, and the temperature is maintained for 30 min-45 min.

5. The method according to claim 2, characterized in that: The mass fraction of the boric acid solution is 5%-50%.

6. The method according to claim 1, characterized in that Before coating the silicon wafer with the boric acid aqueous solution, the following silicon wafer processing steps are also included: Wafer pretreatment: remove damage and stains from n-type silicon wafers, and then soak them in KOH solution; Silicon wafer texturing: Mix the pre-treated silicon wafer with KOH and texturing additives to make texturing; Silicon wafer post-processing: The silicon wafer that has completed silicon wafer texturing is cleaned with HCl and HF, and dried in an inert gas atmosphere to complete the silicon wafer processing.

7. The method according to claim 6, characterized in that During the pretreatment of silicon wafers, 20-30% KOH solution is used for soaking for 300s-400s at a temperature of 40-60°C. And\or, the KOH concentration in silicon wafer texturing is 1%-5%, the texturing additive is 1‰-5‰, the time is 600-800s, and the texturing temperature is 60-80℃; And\or, in the post-treatment of the silicon wafer, the HCl concentration is 1%-3%, the HF concentration is 2%-4%, the cleaning time is 400s-600s, and the cleaning temperature is 25°C.

8. The method according to claim 1, characterized in that: The silicon wafer with a surface of boron oxide is subjected to substitution diffusion of boron atoms in a diffusion furnace. The temperature of the diffusion furnace is 900-1000°C and the time is 15min-40min.

9. A battery emitter, characterized in that: The battery emitter is prepared by the method according to any one of claims 1 to 9.

10. A battery, characterized in that: The battery comprises the battery emitter of claim 9.

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