Texturization and rounded process of silicon wafers for heterojunction with intrinsic thin-layer solar cells

Abstract

Heterojunction with intrinsic thin-layer (HIT) solar cells are sensitive to interface state density. Traditional texture process for silicon solar cells is not suitable for HIT one. Thus, sodium hydroxide (NaOH), isopropanol (IPA) and mixed additive were tentatively introduced for the texturization of HIT solar cells in this study. Then, a mixture including nitric acid (HNO3), hydrofluoric acid (HF) and glacial acetic acid (CH3COOH) was employed to round pyramid structure. The morphology of textured surface and the influence of etching time on surface reflectance were studied, and the relationship between etching time and surface reflectance, vertex angle of pyramid structure was analyzed. It was found that the mixture consisting of 1.1 wt% NaOH, 3 vol% IPA and 0.3 vol% additives with etching time of 22.5 min is the best for HIT solar cells under the condition of 80°C. Uniform pyramid structure was observed and the base width of pyramid was about 2–4 μm. The average surface reflectance was 11.68%. Finally the effect of different processes on the performance of HIT solar cells was investigated. It was shown that these texturization and rounding techniques used in this study can increase short circuit current (Jsc), but they have little influence on fill factor (FF) and open circuit voltage (Voc) of HIT solar cells.