Wet-etch texturing of ZnO:Ga back layer on superstrate-type microcrystalline silicon solar cells

Surface wet etching is applied to the ZnO:Ga (GZO) back contact in mu c-Si thin film solar cells. GZO transparency increases with increasing deposition substrate temperature. Texturing enhances reflective scattering, with etching around 5-6 s producing the best scattering, whereas etching around 5 s produces the best fabricated solar cells. Etching beyond these times produces suboptimal performance related to excessive erosion of the GZO. The best mu c-Si solar cell achieves FF=68%, V(OC)=471 mV and J(SC)=21.48 mA/cm(2) (eta=6.88%). Improvement is attributed to enhanced texture-induced scattering of light reflected back into the solar cell, increasing the efficiency of our lab-made single mu c-Si solar cells from 6.54% to 6.88%. Improved external quantum efficiency is seen primarily in the longer wavelengths, i.e. 600-1100 nm. However, variation of the fabrication conditions offers opportunity for significant tuning of the optical absorption spectrum. (C) 2011 Elsevier B.V. All rights reserved.