Microstructured ZnO coatings for improved performance in Cu(In,Ga)Se2 photovoltaic devices

Abstract

The performance of thin film Cu(In,Ga)Se2 (CIGS) photovoltaics is typically degraded by light lost due to the high reflectivity of the transparent top contact and by recombination resulting from carrier generation far from the junction. Traditional antireflective (AR) coatings are insufficient to address the former issue, particularly at non-normal incidence. We present a novel microstructured ZnO coating that serves two functions; it acts an AR layer with superior non-normal performance in comparison to thin film AR coatings, and it scatters a significant fraction of the incoming radiation at a large angle, resulting in absorption that is on average closer to the junction. This coating, formed via a wet etch process, results in performance comparable to that of uncoated films at normal incidence and an increase of up to 25% in the short circuit current and 18% in device efficiency at non-normal incidence.