An additive-free non-metallic energy efficient industrial texturization process for diamond wire sawn multicrystalline silicon wafers

Abstract

Texturing of diamond wire sawn (DWS) monocrystalline silicon (c-Si) wafers by alkaline process is well established. However, texturing of multicrystalline silicon wafers (mc-Si) is discerned to be a concern. All the DWS mc-Si texturing schemes reported so far either use additives or require additional processing steps which entail additional monetary investment. An additive-free, cost-effective, non-metallic, energy efficient acid based texturing scheme is demonstrated here for the DWS mc-Si wafers. The proposed novel texturing technique recommends hydrofluoric (HF) acid rich acidic solution for obtaining uniform porous silicon (Por-Si) layer, followed by a dilute alkaline dip to obtain a porous inverted rounded structures on the DWS mc-Si wafer surface. The percentage of HF volume in acid texturing solution was varied from 40% to 60% in achieving the best minority carrier lifetime of ∼90 μs in our optimized recipe, therefore suitable for industrial texturing process. The weighted average reflectance (WAR) of our textured mc-Si wafers are ∼29.0% and ∼6.5% after texturing and after final anti-reflective coating, respectively. The cells fabricated using the new acid texturing scheme exhibited an excellent batch average efficiency of 18.46% in industry environment. In the present study, DWS textured wafers are characterized for optoelectronic properties like total reflectance and Photoluminescence (PL) imaging on full wafer area and benchmarked in detail against standard acid textured multi-wire slurry sawn (MWSS) mc-Si wafers, and promising results are reported. A detailed methodology to understand the chemical process of texturing mc-Si wafers using HF-rich acid chemistry is discussed. The reported HF-rich acid texturing process can be easily implemented in any industrial acid texturing tool without any additional investment.