Rear Surface Optimization of CZTS Solar Cells by Use of a Passivation Layer With Nanosized Point Openings

Previously, an innovative way to reduce rear interface recombination in 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, ultrathin CZTS cells with an Al2O3rear surface passivation layer having nanosized point openings are fabricated. The results indicate that introducing such a passivation layer can have a positive impact on open-circuit voltage (VOC; +17%rel.), short-circuit current (JSC ; +5%rel.), and fill factor (FF; +9%rel.), compared with corresponding unpassivated cells. Hence, a promising efficiency improvement of 32%rel. is obtained for the rear passivated cells.