Analyze the impact of silicon wafer quality on the performance of solar cells

Silicon ingot grinding and polishing have a large impact on the function of solar cells. After the polycrystalline silicon ingot is cut squarely, there is a mechanical danger layer on the surface of the small silicon ingot, which is a brittle material, including broken crystal area, dislocation network area and elastic strain area. Its structure is shown in Figure 1. The micro-crack zone is also called the micro-crack zone, which is composed of broken silicon particles. There are many dislocations in the dislocation network area. There is elastic strain in the elastic strain zone, and the silicon atoms are not arranged neatly. Due to the existence of the dangerous layer, there are especially many micro-cracks in the broken crystal zone. In the subsequent battery processing and component processing, it is easy to become the starting point of cracks, causing hidden cracks, micro-cracks, edge collapse and fragmentation of silicon wafers or batteries. Therefore, when the steel ingot is cut into small steel ingots, mechanical grinding or chemical polishing is generally used to remove or reduce the harmful layer on the surface of the steel ingot. Figure 2 On the battery line, the average crushing rate of silicon ingots supplied by suppliers that have not been mechanically polished or chemically polished is about 1.5%, while the average crushing rate of silicon ingots after mechanical polishing is only 0.7%, which is two of the two after mechanical polishing. Times more. The impact of saw marks, steps and uneven thickness of silicon wafers on the function of solar cells A batch test was carried out on a supplier's defective silicon wafers such as saw teeth, steps, and uneven thickness. During this period, the uneven depth of the saw blade is greater than 30um, the depth of the stepped blade is 30-40um, and the thickness of the uneven blade is planned to be 130-330um. Due to the difference in roughness and thickness in some areas on the silicon wafer, in the various processes of battery manufacturing, due to the unevenness of the stress, the fragmentation rate will increase. In the screen printing process, especially the sawing and stepping of the height variation of the silicon wafer in certain areas, it is easy to form electrodes or back field leakage, resulting in poor electrodes. Fragmentation rate, electrode defect rate and total waste and defect rate are seen as signs, steps and uneven wafer thickness are significantly higher than normal wafers, and the total waste and defect rate during this period is 4%-10% higher than normal wafers . Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Explain the advantages of 220V large-capacity portable UPS power supply