Stable High-Efficiency Two-Dimensional Perovskite Solar Cells Via Bromine Incorporation.

Two-dimensional (2D) organic-inorganic perovskites as one of the most important photovoltaic material used in solar cells have attracted remarkable attention. These 2D perovskites exhibit superior environmental stability and wide tunability of their optoelectronic properties. However, their photovoltaic performance is far behind those of traditional three-dimensional (3D) perovskites. In this work, we demonstrate the power conversion efficiency (PCE) of 2D perovskite solar cells (PVSCs) is greatly improved from 3.01% for initial to 12.19% by the incorporation of PbBr. The enhanced efficiency is attributed to superior surface quality, enhanced crystallinity, and the resulting reduced trap-state density. Furthermore, PbBr incorporated devices without encapsulation show excellent humidity stability, illumination stability, and thermal stability. This work provides a universal and viable avenue toward efficient and stable 2D PVSCs.