A self-assembled CuS–MXene bridge for hole-boosting 10.51%-efficiency all-inorganic tri-brominated perovskite solar cells

Abstract

The precise management of interface charge extraction and transport plays a decisive role in enhancing the photovoltaic performance of perovskite solar cells (PSCs). Herein, a composite of CuS–MXene synthesized in situ by molecular self-assembly is efficiently employed as a hole extractor for all-inorganic CsPbBr₃ PSCs. Theoretical and experimental results demonstrate that due to the spontaneous transfer of partial electrons in MXene functional groups to CuS, a p-type doping and a reduced charge localization of MXene are achieved to improve the interface energy level matching and boost hole extraction and transfer. Meanwhile, an interface bridge of CsPbBr₃ → CuS → MXene for rapid hole transport and good interface contact is established because of the formation of the Pb–S bond between CsPbBr₃ and CuS, which together with the electron donor groups of MXene further passivates the trap states on the perovskite surface to substantially minimize interfacial charge recombination. Finally, the encapsulation-free CsPbBr₃ PSCs tailored with CuS–MXene achieve a champion power conversion efficiency of up to 10.51% and a long-term humidity or temperature tolerance with 90% or over efficiency retention rate in air for 30 days.