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

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 VOC 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. A zwitterion molecule of bis(2-hydroxyethyl)dimethylammonium chloride is introduced in the perovskite surface for simultaneously suppressing both the positive and negative localized defects recombination as well as spontaneously converting the perovskite surface to be more n-type conductive contact layer for facilitated charge separation. With this surface engineering, the power conversion efficiency of perovskite/silicon tandem solar cells is increased from 26.71% to 28.67% with a fill factor from 76.51% to 80.02%.image

Automated summary

This study reports a method to passivate and separate charges on the surface of perovskite in order to enhance the power conversion efficiency and fill factor of perovskite/silicon tandem solar cells.