Wet-chemical treatment and electronic interface properties of silicon solar cell substrates

摘要

On textured n-type silicon substrates for solar cell manufacturing, the relation between light trapping behav_ior, structural imperfections, energetic distribution of interface state densities and interface recombination losses were investigated by applying surface sensitive techniques. The field-modulated surface photovolt_age (SPV), in-situ photoluminescence (PL) measurements, total hemispherical UV-NIR-reflectance mea_surements and electron microscopy (SEM) were employed to yield detailed information on the influence of wet-chemical treatments on preparation induced micro-roughness and electronic properties of polished and textured silicon substrates. It was shown that isotropic as well as anisotropic etching of light trap_ping structures result in high surface micro-roughness and density of interface states. Removing damaged surface layers in the nm range by wet-chemical treatments, the density of these states and the related inter_face recombination loss can be reduced. In-situ PL measurements were applied to optimise HF-treatment times aimed at undamaged, oxide-free and hydrogen-terminated substrate surfaces as starting material for subsequent solar cell preparations.