Conductive passivating contact for high fill factor monolithic perovskite/silicon tandem solar cells

Abstract

Perovskite/silicon tandem solar cells (PK/Si TSCs) blaze the way in pushing power conversion efficiency (PCE) beyond the single-junction Shockley–Queisser limit. Meanwhile, localized defects in perovskite subcells result in a lower fill factor (FF), which limits further improvement of PCE in PK/Si TSCs. Herein, we report a conductive passivation contact layer by posttreatment of bis(2-hydroxyethyl)dimethylammonium chloride (BDAC) zwitterion molecule on the perovskite surface. It can passivate the positive and negative localized defects, inhibit the formation of Pb⁰, and spontaneously convert the perovskite surface to be a more n-type conductive contact layer for charge separation. These combined enhancements enabled a PCE of 21.4% with an enhanced V_OC of 80 mV and an FF of 82.84% for the inverted single-junction device prepared by the two-step method. Moreover, BDAC passivation achieved a PCE of 28.67% with an FF of 80.02% for PK/Si TSCs. In addition, the scaling-up device with an active area of 11.879 cm² delivers a PCE of 24.46%, and a minimodule with power conversion over 2 W is designed and fabricated.