Optical properties of smooth anti-reflective three-dimensional textures for silicon thin-film solar cells

In recent years, thin-film silicon solar cells on glass prepared by liquid-phase crystallization have made progress towards high efficiency solar cells. Current record cells reach wafer-equivalent material quality and morphology using thin-film technologies. However, short-circuit current densities and hence, efficiencies, are still limited. The reflection at the interface between glass superstrate and silicon absorber layer has been identified as one major loss mechanism. These optical losses can be reduced by nanostructuring of the interface. It is important, however, that this nanostructured interface does not lead to a deterioration of silicon material quality simultaneously. Recently, we introduced SMooth Anti-Reflective Three-dimensional (SMART) textures, which consist of temperature-stable SiOx, sal-gel nanostructures and a smoothing layer of spin-coated TiOx. These SMART textures on glass superstrates exhibit a smooth interface morphology and hence allow growing high-quality silicon absorber layers by liquid phase crystallization. Here, we investigate the optical properties of the SMART textures with and without an additional SiNx, layer in experiment and by l-dimensional optical simulations. It is shown that both, the SMART textures with and without additional SiNx, layer, can outperform the optimized planar interlayer system of current record solar cell devices. Very low mean reflectance values of 11.2% are found in the wavelength regime from 400 nm to 600 nm for an optimized texture consisting of a 50 nm thick SMART texture with additional 15 nm SiNx layer. (C) 2016 The Authors. Published by Elsevier Ltd.