The orientation and optical properties of inverted-pyramid-like structures on multi-crystalline silicon textured by Cu-assisted chemical etching

An effective low-cost texturing method based on the Cu-assisted chemical etching (CACE) technique was adopted to thoroughly texture diamond wire sawn (DWS) multi-crystalline silicon (mc-Si) wafers to form inverted-pyramid-like (IPL) structures on different grains. A mathematical model was first established to confirm the orientation of the IPL structures on grains 〈1 1 0〉, grains 〈1 1 2〉 and grains 〈1 1 3〉; this confirmation enables one to deeply understand the CACE process for mc-Si. In addition, the optical properties of IPL structures on different grains were investigated. We reveal that the IPL texture reduces the wafer reflectance to a much lower level of 22.4% and 4.4% before and after SiNx deposition, respectively. Due to the lower reflectance, the average cell efficiency for IPL textured wafers is as high as 19.03%, which is 0.52% absolute higher than that for wafers textured using HF/HNO3 mixture solutions. This CACE technique paves new insight to promote the industrial application of DWS mc-Si solar cells.