Reactive ion etched black silicon texturing: A comparative study

We report on significant progress towards the application of reactive ion etched (RIE) black silicon (b-Si) as an alternative to the most commonly applied front-side textures utilized in the crystalline silicon photovoltaics industry - random pyramids and isotexture. The as-etched b-Si surface displays approximately 1% front side reflectance weighted across the solar spectrum, outperforming both random pyramids (2.83%) and isotexture (6.06%) with optimized anti-reflection coatings. The b-Si front surface reflectance reduces to below 0.4% after the application of an Al₂O₃ surface passivation layer. At low injection levels, recombination of charge carriers at the b-Si surface poses no limitation on the minority carrier lifetimes of bulk-limited Cz and multicrystalline samples. At higher injection, or with higher quality substrates, additional recombination at the b-Si surface, characterized by a surface J_os of 20 fA.cm^-2, may play a more significant role. This study provides a rigorous empirical justification for recent advances in b-Si textured solar cells and indicates pathways for further efficiency gains.