Rear surface optimization of CZTS solar cells by use of a passivation layer with nano-sized point openings

Previously, an innovative way to reduce rear interface recombination of Cu(In,Ga)(S,Se)₂ (CIGSSe) solar cells has been successfully developed. In this work, this concept is established in Cu₂(Zn,Sn)(S,Se)₄ (CZTSSe) cells, to demonstrate its potential for other thin-film technologies. Therefore, ultra-thin CZTS cells with an Al₂O₃ rear surface passivation layer having nano-sized point openings are fabricated. The results indicate that introducing such a passivation layer can have a positive impact on open circuit voltage (Voc; +49%rel.) or short circuit current (Jsc; +17%rel.), compared to corresponding unpassivated cells. Hence, a promising efficiency improvement of 52%rel. is obtained for the rear passivated cells.