Role of wet chemical saw damage removal process in texturing of c-Si and performance of a-Si:H/c-Si heterojunction solar cells

Silicon heterojunction (SHJ) solar cells' performance primarily depends on silicon surface conditioning. Therefore, it is necessary to control the uniformity of the textured silicon surface by any means, either by the initial saw damage removal (SDR) or during the texturing. In this work, we have explored the effect of SDR treatment on as-cut silicon wafers for controlling the textured silicon surface morphology in SHJ device performance. We find a direct correlation between the alkali concentration of the SDR solution and the resulting surface morphology after subsequent texturing, as well as the silicon surface passivation and SHJ device performance. It is reflected that better device performance can be achieved by initially controlling the silicon surface obtained by choosing an appropriate concentration of the SDR solution. An intermediate concentration of 30 wt.% NaOH solution formed uniform square pits, which led to the formation of nearly homogeneous pyramidal distribution after texturing. This optimized SDR process yielded an arithmetic average reflectance of ~ 12% from textured silicon surfaces and an effective minority carrier lifetime of > 1 ms of symmetrically passivated samples. SHJ solar cells are fabricated with the optimized SDR-processed wafers, and a power conversion efficiency of ~ 18.2% with an open-circuit voltage of 701 mV is achieved.