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 Cu
₂
(Zn,Sn)(S,Se)
₄
(CZTSSe) cells to demonstrate its potential for other thin-film technologies. Therefore, ultrathin CZTS cells with an Al
₂
O
₃
rear 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 (V
_OC
; +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.