Method for analyzing EL black spots generated by PERC battery and preparation method of PERC battery

Abstract

The invention relates to a method for analyzing EL black spots generated by a PERC battery and a preparation method of the PERC battery. The method comprises the following steps: providing a PERC battery which detects EL black spots; removing a surface coating of the PERC battery, recycling a silicon wafer with a PN junction, replacing equipment to perform coating printing and PL test again, and if EL black spots disappear, determining that the EL black spots are caused by coating printing, and completing the detection; if the EL black spots still exist, the surface plating layer is removed again, and the silicon wafer with PN junctions is recycled; the silicon wafer is subjected to texturing to remove PN junctions, then PN junction preparation, film coating printing and PL testing are conducted again in sequence, if the EL black spots disappear, the EL black spots are caused by the PN junctions, and if the EL black spots still exist, the EL black spots are caused by the defects of the silicon wafer. According to the method, the process causing EL black spots can be quickly positioned, and an effective analysis means is provided for improving the yield of PERC batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for analyzing EL black spots generated by a PERC cell and a method for preparing the PERC cell. Background Art

[0002] PERC cells are highly efficient and still dominate large-scale applications and industrial production. At present, the efficiency of PERC cells has almost reached its limit, and improving the yield rate of PERC cells has become a key factor in the competition in the photovoltaic industry.

[0003] The main factors affecting the yield of PERC cells are EL spots and scratches. Among them, the cause of EL spots is difficult to locate. Therefore, it is urgent to develop a method to analyze the EL spots generated by PERC cells, so as to further improve the yield of PERC cells. Summary of the invention

[0004] Based on this, it is necessary to provide a method for analyzing the EL black spots generated by PERC cells and a method for preparing PERC cells to address the above problems. This method can quickly locate the process that causes EL black spots and provide an effective analysis method for improving the yield of PERC cells.

[0005] The present invention discloses a method for analyzing EL black spots generated by a PERC cell, comprising the following steps:

[0006] Provide detection of PERC cells with EL black spots;

[0007] The surface coating of the PERC cell is removed, the silicon wafer with the PN junction is recovered, and the equipment is replaced to re-perform coating printing and PL testing on the silicon wafer. If the EL black spots disappear, the EL black spots are caused by coating printing, and the detection is completed;

[0008] If the EL black spots still exist, remove the surface coating of the PERC battery again, recover the silicon wafer with the PN junction, texturize the silicon wafer to remove the PN junction, and then re-prepare the PN junction, perform coating printing and PL testing in sequence. If the EL black spots disappear, the EL black spots are caused by the PN junction process. If the EL black spots still exist, the EL black spots are caused by defects in the silicon wafer itself.

[0009] In one embodiment, the replacement device includes a furnace tube and a graphite boat for replacing a coating device.

[0010] In one embodiment, the step of removing the surface coating of the PERC cell comprises:

[0011] Removing the grid lines on the front side of the PERC cell using a nitric acid solution and removing the grid lines on the back side of the PERC cell using a hydrochloric acid solution;

[0012] Using hydrofluoric acid to remove the passivation anti-reflection layer on the front and back of the PERC cell;

[0013] Using ammonia water to remove the porous silicon layer on the front and back of the PERC cell to obtain a silicon wafer;

[0014] Neutralizing the residual ammonia on the surface of the silicon wafer using a mixed acid solution of hydrochloric acid and hydrofluoric acid;

[0015] The silicon wafer was cleaned with deionized water.

[0016] In one embodiment, the step of removing the grid lines on the front side of the PERC cell using a nitric acid solution comprises:

[0017] Place the PERC battery in a nitric acid solution with a concentration of 20%-75% for 2min-10min, and remove the residual nitric acid solution after taking it out.

[0018] In one embodiment, the step of removing the grid lines on the back of the PERC cell using a hydrochloric acid solution comprises:

[0019] The PERC battery is placed in a hydrochloric acid solution with a concentration of 10%-49% for 1 min-5 min, and the residual hydrochloric acid solution is removed after being taken out.

[0020] In one embodiment, the step of removing the passivation anti-reflection layer on the front and back sides of the PERC cell using hydrofluoric acid comprises:

[0021] The PERC cell is placed in hydrofluoric acid with a concentration of 5% to 40% for 1 to 10 minutes, and the residual hydrofluoric acid is removed after being taken out.

[0022] In one embodiment, the step of removing the porous silicon layer of the PERC cell using ammonia water comprises:

[0023] The PERC cell is placed in ammonia water with a concentration of 1%-10% for 1 min-5 min.

[0024] In one embodiment, the step of neutralizing the residual ammonia water on the surface of the silicon wafer with a mixed acid solution of hydrochloric acid and hydrofluoric acid comprises:

[0025] The silicon wafer is cleaned by using a mixed acid solution of hydrochloric acid and hydrofluoric acid, wherein the mass fraction of HCl in the mixed acid solution is 30%-36%, and the mass fraction of HF is 40%-49%.

[0026] A method for preparing a PERC cell includes the step of locating the generation of EL black spots by using the above-mentioned method for analyzing the generation of EL black spots in a PERC cell.

[0027] In one embodiment, the process is adjusted to avoid the generation of EL black spots. When the process generating EL black spots is coating printing, the furnace tube and graphite boat of the coating equipment are replaced. When the process generating EL black spots is a PN junction process, the steps or equipment that introduce pollution in the PN junction process are checked and treated.

[0028] The method for analyzing black spots generated by PERC cells of the present invention comprises the following steps: firstly re-coating and printing the PERC cells, and analyzing whether the EL black spots are caused by coating and printing according to whether the EL black spots still exist; then re-preparing PN junctions and re-coating and printing the PERC cells where the EL black spots still exist, and analyzing whether the EL black spots are caused by PN junction contamination or defects in the silicon wafer itself according to whether the EL black spots still exist. The method can quickly locate the process leading to the EL black spots, timely reduce the generation of defective products, and thus effectively improve the yield rate of the PERC cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is a schematic flow chart of the method for analyzing black spots generated in PERC cells according to Example 1 of the present invention. DETAILED DESCRIPTION

[0031] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0033] The present invention provides a method for analyzing black spots generated by a PERC cell, comprising the following steps:

[0034] S10, provides detection of PERC cells with EL black spots;

[0035] S20, remove the surface coating of the PERC cell, recycle the silicon wafer with PN junction, replace the equipment to re-coat and print the silicon wafer and perform PL test. If the EL black spot disappears, the EL black spot is caused by the coating printing, and the test is completed;

[0036] S30, if the EL black spots still exist, the surface coating of the PERC battery is removed again, the silicon wafer with the PN junction is recovered, the silicon wafer is subjected to texturing to remove the PN junction, and then the PN junction, coating printing and PL testing are re-prepared in sequence. If the EL black spots disappear, the EL black spots are caused by the PN junction process. If the EL black spots still exist, the EL black spots are caused by defects in the silicon wafer itself.

[0037] In the method for analyzing black spots generated in PERC cells of the present invention, first, for the PERC cell with EL black spots provided in step S10, re-plating and printing are performed in step S20, and it is analyzed whether the EL black spots are caused by the plating and printing according to whether the EL black spots still exist.

[0038] It can be understood that the surface coating of the PERC cell includes a passivation anti-reflection layer and grid lines on the front side of the PERC cell, and a passivation anti-reflection layer and grid lines on the back side.

[0039] In one embodiment, in step S20, the step of removing the surface coating of the PERC cell includes:

[0040] S201, removing the grid lines on the front side of the PERC cell using a nitric acid solution and removing the grid lines on the back side of the PERC cell using a hydrochloric acid solution;

[0041] S202, removing the passivation anti-reflection layer on the front and back sides of the PERC cell using hydrofluoric acid;

[0042] S203, removing the porous silicon layer on the front and back sides of the PERC cell using aqueous ammonia to obtain a silicon wafer;

[0043] S204, neutralizing the residual ammonia on the surface of the silicon wafer using a mixed acid solution of hydrochloric acid and hydrofluoric acid;

[0044] S205, cleaning the silicon wafer with deionized water.

[0045] Through the cleaning process of the present invention, the gate lines and the passivation anti-reflection layer on the front and back sides can be removed cleanly, so that the silicon wafer can be returned to the processes of texturing, coating and printing, etc., thereby ensuring that the method provided by the present invention can be used to study and analyze the battery cells and improve the yield of the production line.

[0046] The grid lines on the front of the PERC cell are usually selected from silver grid lines, and the grid lines on the back are usually selected from aluminum grid lines. Therefore, in step S201, the grid lines on the front of the PERC cell are removed using a nitric acid solution, and the grid lines on the back of the PERC cell are removed using a hydrochloric acid solution.

[0047] Optionally, the step of removing the grid lines on the front side of the PERC cell by using a nitric acid solution includes: placing the PERC cell in a nitric acid solution with a concentration of 20%-75% for 2 minutes to 10 minutes, and removing the residual nitric acid solution after taking the cell out.

[0048] Optionally, the step of removing the grid lines on the back of the PERC cell by using a hydrochloric acid solution includes: placing the PERC cell in a hydrochloric acid solution with a concentration of 10%-49% for 1 min-5 min, and removing the residual hydrochloric acid solution after taking the cell out.

[0049] The passivation anti-reflection layer on the front side of the PERC cell is usually selected from SiN x Thin film, the passivation anti-reflection layer on the back of the PERC cell is usually selected from aluminum oxide and SiN x Therefore, in step S202, the step of removing the passivation anti-reflection layer on the front and back sides of the PERC cell by using hydrofluoric acid includes: placing the PERC cell in a hydrofluoric acid with a concentration of 5%-40% for 1 min-10 min, and removing the residual hydrofluoric acid after taking it out.

[0050] In step S203, the step of removing the porous silicon layer on the front and back of the PERC cell by using ammonia water includes: placing the PERC cell in ammonia water with a concentration of 1%-10% for 1 min-5 min. It should be noted that the PERC cell does not originally include a porous silicon layer, and the porous silicon layer is generated during step S203.

[0051] In step S204, the step of using a mixed acid solution of hydrochloric acid and hydrofluoric acid to neutralize the residual ammonia water on the surface of the silicon wafer includes: using a mixed acid solution of hydrochloric acid and hydrofluoric acid to clean the silicon wafer, wherein the mass fraction of HCl in the mixed acid solution is 30%-36%, and the mass fraction of HF is 40%-49%.

[0052] In one embodiment, the adjustment process includes replacing a furnace tube and a graphite boat of the coating equipment.

[0053] In one embodiment, the re-coating step includes forming a passivation anti-reflection layer and gate lines on the front side of the silicon wafer, and forming a passivation anti-reflection layer and gate lines on the back side of the silicon wafer.

[0054] Again, for the PERC cell where the EL black spots still exist, the surface coating is removed again in step S30 to recover the silicon wafer with the PN junction.

[0055] The step of removing the surface coating of the PERC cell in step S30 is performed with reference to step S20.

[0056] Finally, step S30 is used to re-prepare the PN junction, coating printing and PL test on the recycled silicon wafers in sequence. According to whether the EL black spots still exist, it is analyzed whether the EL black spots are caused by PN junction contamination or defects in the silicon wafer itself. This method can quickly locate the process that causes the EL black spots, timely reduce the generation of defective products, and thus effectively improve the yield of PERC cells.

[0057] It should be noted that texturing the silicon wafer can remove the original PN junction on the silicon wafer.

[0058] In one embodiment, the step of re-preparing the PN junction includes sequentially performing high temperature diffusion and annealing on the silicon wafer.

[0059] The present invention also provides a method for preparing a PERC battery, comprising a step of locating the generation of black spots using the above-mentioned method for analyzing the generation of black spots in a PERC battery.

[0060] In one embodiment, the process is adjusted to avoid the generation of EL black spots. When the process that generates EL black spots is film coating and printing, the furnace tube and graphite boat of the film coating equipment are replaced. When the process that generates EL black spots is a PN junction process, the steps or equipment that introduce pollution in the PN junction process are checked and treated. It can be understood that the furnace tube, exhaust, air intake, exhaust and quartz boat may all introduce pollution.

[0061] Hereinafter, the method for analyzing EL black spots generated by PERC cells and the method for preparing PERC cells will be further described through the following specific examples.

[0062] Example 1

[0063] like Figure 1 As shown in (A), the PERC cell with EL black spots detected is placed in a container containing a nitric acid solution with a concentration of 40%, and reacted at room temperature for 7 minutes. After the silver grid lines of the PERC cell are completely removed, it is taken out and washed with deionized water to remove the residual nitric acid solution. The PERC cell is placed in a container containing a hydrochloric acid solution with a concentration of 20%, and reacted at room temperature for 5 minutes. After the aluminum grid lines of the PERC cell are completely removed, it is washed with deionized water to remove the residual hydrochloric acid solution.

[0064] like Figure 1 As shown in (B), the PERC cell is placed in a container containing hydrofluoric acid with a concentration of 20%, and reacted at room temperature for 8 minutes. After the passivation anti-reflection layer is completely removed, it is washed with deionized water to remove the residual hydrofluoric acid.

[0065] The PERC battery was placed in a container containing ammonia water with a stable concentration of 4%. The reaction was carried out at room temperature for 4.5 minutes. After the porous silicon layer of the PERC battery was completely removed, a silicon wafer was obtained.

[0066] The silicon wafer is cleaned with a mixed acid solution of hydrochloric acid and hydrofluoric acid to remove residual alkali solution on the surface of the silicon wafer, and the silicon wafer is dried. In the mixed acid solution, the mass fraction of HCl is 36%, and the mass fraction of HF is 49%.

[0067] Rinse the silicon wafer using deionized water.

[0068] like Figure 1 As shown in (C), the silicon wafer with PN junction is recovered, the furnace tube and graphite boat of the coating equipment are replaced, and the silicon wafer is re-coated and printed and PL tested. If the EL black spots disappear, the EL black spots of the PERC battery are caused by the coating printing. If the EL black spots still exist, the above steps are used again to remove the silver grid lines, aluminum grid lines, passivation anti-reflection layer and porous silicon layer of the PERC battery to recover the silicon wafer with PN junction.

[0069] The silicon wafer is sequentially subjected to texturing, high-temperature diffusion and annealing to prepare the PN junction, and then subjected to coating printing and PL testing. If the EL black spots disappear, the EL black spots of the PERC battery are caused by the PN junction process. If the EL black spots still exist, the EL black spots of the PERC battery are caused by defects in the silicon wafer itself.

[0070] Example 2

[0071] The PERC cell with EL black spots was placed in a container containing nitric acid solution with a concentration of 50%. The solution was reacted at room temperature for 5 minutes. After the silver grid lines of the PERC cell were completely removed, it was taken out and washed with deionized water to remove the residual nitric acid solution.

[0072] The PERC battery was placed in a container containing a hydrochloric acid solution with a concentration of 30%. The solution was reacted at room temperature for 3 minutes. After the aluminum grid line of the PERC battery was removed, it was washed with deionized water to remove the residual hydrochloric acid solution.

[0073] The PERC cell was placed in a container containing hydrofluoric acid with a concentration of 30%. The reaction was carried out at room temperature for 6 minutes. After the passivation anti-reflection layer was completely removed, it was washed with deionized water to remove the residual hydrofluoric acid.

[0074] The PERC battery was placed in a container containing ammonia water with a stable concentration of 5%. The reaction was carried out at room temperature for 3 minutes. After the porous silicon layer of the PERC battery was completely removed, a silicon wafer was obtained.

[0075] The silicon wafer is cleaned with a mixed acid solution of hydrochloric acid and hydrofluoric acid to remove residual alkali solution on the surface of the silicon wafer, and the silicon wafer is dried. In the mixed acid solution, the mass fraction of HCl is 36%, and the mass fraction of HF is 49%.

[0076] Rinse the silicon wafer using deionized water.

[0077] Recycle the silicon wafers, replace the furnace tubes and graphite boats of the coating equipment, re-coat and print the silicon wafers and perform PL tests. If the EL black spots disappear, the EL black spots of the PERC battery are caused by coating printing. If the EL black spots still exist, use the above steps again to remove the silver grid lines, aluminum grid lines, passivation anti-reflection layer and porous silicon layer of the PERC battery and recycle the silicon wafers.

[0078] The silicon wafer is sequentially subjected to texturing, high-temperature diffusion and annealing to prepare the PN junction, and then subjected to coating printing and PL testing. If the EL black spots disappear, the EL black spots of the PERC battery are caused by the PN junction process. If the EL black spots still exist, the EL black spots of the PERC battery are caused by defects in the silicon wafer itself.

[0079] Example 3

[0080] The PERC cell with EL black spots was placed in a container containing nitric acid solution with a concentration of 60%. The solution was reacted at room temperature for 3 minutes. After the silver grid lines of the PERC cell were removed, it was taken out and washed with deionized water to remove the residual nitric acid solution.

[0081] The PERC battery was placed in a container containing a hydrochloric acid solution with a concentration of 40%. The solution was reacted at room temperature for 1 minute. After the aluminum grid line of the PERC battery was removed, it was washed with deionized water to remove the residual hydrochloric acid solution.

[0082] Place the PERC cell in a container containing hydrofluoric acid with a concentration of 40% and react at room temperature for 1 minute. After the passivation anti-reflection layer is completely removed, wash with deionized water to remove residual hydrofluoric acid.

[0083] The PERC cell was placed in a container containing ammonia water with a stable concentration of 8%. The reaction was carried out at room temperature for 1 minute. After the porous silicon layer of the PERC cell was completely removed, a silicon wafer was obtained.

[0084] The silicon wafer is cleaned with a mixed acid solution of hydrochloric acid and hydrofluoric acid to remove residual alkali solution on the surface of the silicon wafer, and the silicon wafer is dried. In the mixed acid solution, the mass fraction of HCl is 36%, and the mass fraction of HF is 49%.

[0085] Rinse the silicon wafer using deionized water.

[0086] Recycle the silicon wafers, replace the furnace tubes and graphite boats of the coating equipment, re-coat and print the silicon wafers and perform PL tests. If the EL black spots disappear, the EL black spots of the PERC battery are caused by coating printing. If the EL black spots still exist, use the above steps again to remove the silver grid lines, aluminum grid lines, passivation anti-reflection layer and porous silicon layer of the PERC battery and recycle the silicon wafers.

[0087] The silicon wafer is sequentially subjected to texturing, high-temperature diffusion and annealing to prepare the PN junction, and then subjected to coating printing and PL testing. If the EL black spots disappear, the EL black spots of the PERC battery are caused by the PN junction process. If the EL black spots still exist, the EL black spots of the PERC battery are caused by defects in the silicon wafer itself.

[0088] The present invention locates the process of generating EL black spots of PERC cells through the above method. When the EL black spots are generated due to the coating printing process, the furnace tube and the graphite boat of the coating equipment are replaced. When the EL black spots are generated due to the PN junction process, the steps or equipment that introduce pollution in the PN junction process are checked and treated, thereby reducing the proportion of EL black spots from 0.8% to 0.2% and increasing the yield by 0.6%.

[0089] All possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for analyzing EL black spots generated by PERC cells, It is characterized in that The following steps are involved: Provide detection of PERC cells with EL black spots; The surface coating of the PERC cell is removed, the silicon wafer with the PN junction is recovered, and the equipment is replaced to re-perform coating printing and PL testing on the silicon wafer. If the EL black spots disappear, the EL black spots are caused by coating printing, and the detection is completed; If the EL black spots still exist, remove the surface coating of the PERC battery again, recover the silicon wafer with the PN junction, texturize the silicon wafer to remove the PN junction, and then re-prepare the PN junction, perform coating printing and PL testing in sequence. If the EL black spots disappear, the EL black spots are caused by the PN junction process. If the EL black spots still exist, the EL black spots are caused by defects in the silicon wafer itself.

2. The method for analyzing EL black spots generated by PERC cells according to claim 1, It is characterized in that The replacement equipment includes replacing the furnace tube and the graphite boat of the coating equipment.

3. The method for analyzing EL black spots generated by PERC cells according to claim 1, It is characterized in that The step of removing the surface coating of the PERC cell comprises: Removing the grid lines on the front side of the PERC cell using a nitric acid solution and removing the grid lines on the back side of the PERC cell using a hydrochloric acid solution; Using hydrofluoric acid to remove the passivation anti-reflection layer on the front and back of the PERC cell; Using ammonia water to remove the porous silicon layer on the front and back of the PERC cell to obtain a silicon wafer; Neutralizing the residual ammonia on the surface of the silicon wafer using a mixed acid solution of hydrochloric acid and hydrofluoric acid; The silicon wafer was cleaned with deionized water.

4. The method for analyzing EL black spots generated by PERC cells according to claim 3, It is characterized in that The steps of removing the grid lines on the front of the PERC cell using a nitric acid solution include: Place the PERC battery in a nitric acid solution with a concentration of 20%-75% for 2min-10min, and remove the residual nitric acid solution after taking it out.

5. The method for analyzing EL black spots generated by PERC cells according to claim 3, It is characterized in that The step of removing the grid lines on the back of the PERC cell by using a hydrochloric acid solution comprises: The PERC battery is placed in a hydrochloric acid solution with a concentration of 10%-49% for 1 min-5 min, and the residual hydrochloric acid solution is removed after being taken out.

6. The method for analyzing EL black spots generated by PERC cells according to claim 3, It is characterized in that The step of removing the passivation anti-reflection layer on the front and back of the PERC cell by using hydrofluoric acid comprises: The PERC cell is placed in hydrofluoric acid with a concentration of 5% to 40% for 1 to 10 minutes, and the residual hydrofluoric acid is removed after being taken out.

7. The method for analyzing EL black spots generated by PERC cells according to claim 3, It is characterized in that The step of removing the porous silicon layer of the PERC cell by using ammonia water comprises: The PERC cell is placed in ammonia water with a concentration of 1% to 10% for 1 min to 5 min.

8. The method for analyzing EL black spots generated by PERC cells according to claim 3, It is characterized in that The step of neutralizing the residual ammonia water on the surface of the silicon wafer with a mixed acid solution of hydrochloric acid and hydrofluoric acid comprises: The silicon wafer is cleaned by using a mixed acid solution of hydrochloric acid and hydrofluoric acid, wherein the mass fraction of HCl in the mixed acid solution is 30%-36%, and the mass fraction of HF is 40%-49%.

9. A method for preparing a PERC battery, It is characterized in that The method comprises the step of locating the generation of EL black spots by using the method for analyzing the generation of EL black spots in PERC cells as described in any one of claims 1 to 8.

10. The method for preparing a PERC cell according to claim 9, It is characterized in that Adjust the process to avoid the generation of EL black spots. When the process that generates EL black spots is coating printing, replace the furnace tube and graphite boat of the coating equipment. When the process that generates EL black spots is a PN junction process, check and treat the steps or equipment that introduce pollution in the PN junction process.

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