Incorporation of Two-Dimensional WSe₂ into MAPbI₃ Perovskite for Efficient and Stable Photovoltaics

Achieving reduced defect density and efficient charge carrier extraction plays a vital role for efficient and stable perovskite solar cells (PSCs). Over the course of technical development, it is desired to use one single material or approach to synergistically passivate defects and enhance the charge extraction. In this work, we developed an effective strategy for obtaining efficient and stable PSCs via incorporating quasi-monolayer two-dimensional WSe₂ into the MAPbI₃ perovskite layer. The addition of WSe₂ helps with the formation of perovskite film with higher quality and also passivates the Pb-related defects through Pb-Se coordination bonding. MAPbI₃/WSe₂ shows a more matched energy-level alignment between the perovskite layer and hole transport layer for accelerated hole extraction. Consequently, the performances of PSCs significantly improved with power conversion efficiency increase from 19.2% to 21.2% after the incorporation of WSe₂. Accordingly, the MAPbI₃/WSe₂-based PSCs exhibit well-improved photostability with suppression of Pb⁰ defect formation.