19.2%-Efficient Multicrystalline Silicon Solar Cells via Additive-Free Mechanical Grinding Surface Pretreatment for Diamond-Wire-Sawn Wafers

Abstract

The introduction of diamond wire sawing (DWS) technology has resulted in significant cost reduction in the fabrication of crystalline silicon wafers. However, the DWS process results in parallel wheel marks, saw damage, and formation of an amorphous silicon layer on the surface, which causes difficultly in effectively forming the desired surface texture using conventional acidic etching (also known isotropic etching) techniques for multicrystalline silicon (mc-Si) wafers. In this study, we propose a novel pretreatment grinding (NPTG) technique as a method to address such issues. This is a relatively simple and inexpensive method that does not utilize processes that require the use of expensive equipment, such as vacuum equipment. Additionally, it makes use of environment-friendly procedures that do not require materials such as metal catalysts and additives that cause environmental pollution. The proposed NPTG method provides a good surface topology for effective texturing using a conventional acidic etching solution, and as a result, a uniform texture can be applied to DWS mc-Si wafers. Under the optimized experimental conditions in this study, a weighted average reflectance of 22.63% was achieved after the NPTG was applied. This reflected 6.67% less light than the 29.3% after conventional acidic texturing without the NPTG using DWS mc-Si wafers. Further, a solar cell fabricated using the DWS mc-Si wafers treated with the NPTG method achieved a cell efficiency of approximately 19.2%.