Single-component damage-etch process for improved texturization of monocrystalline silicon wafer solar cells

Abstract

A new saw damage-etch process based on a hot sodium hypochlorite (NaOCl) solution is reported here. This process performs simultaneous damage removal and oxide masking of raw c-Si wafers in a single step. NaOCl is a strong oxidizing agent, and during the NaOCl damage-etch process, the oxide grown remains present even after the completion of the process. This oxide layer acts as protective mask during alkaline texture to form uniform and small (∼2-4 μm height) pyramids on the 1 0 0 Si wafer surface. Unlike chemical vapor deposited silicon nitride or silicon dioxide protective masking processes reported by other researchers, this new damage-etch process is cost effective. It is also a single-component damage-etch process using only NaOCl solution. Thus, it involves easy bath preparation and performs in situ chlorine cleaning. Using the new damage-etch process, optimized texturing of the wafers is ascertained by electron microscopy and reflectivity studies of the textured surfaces. This new process is applied in the industrial R&D pilot line of the Solar Energy Research Institute of Singapore (SERIS) to fabricate screen-printed 156-mm pseudosquare p-type solar cells with tube-diffused emitters to yield efficiencies of over 18%. © 2011-2012 IEEE.