Controlling the Property of Edges in Layered 2D Perovskite Single Crystals.

Two-dimensional (2D) hybrid perovskites have emerged as promising materials for optoelectronic devices owing to their improved stability. The crystal edges of layered 2D perovskites were found to play an important role in device performance by providing a pathway to dissociate bound excitons into long-lived free charge carriers. However, their formation mechanism and whether they are controllable remain unclear. Herein, we report a photoluminescence (PL) imaging study on layered (BA)(MA)PbI (BA = CH(CH)NH, MA = CHNH) perovskite single crystals before and after treatment with butylammonium iodide (BAI) and methylammonium iodide (MAI) solutions. We find that the crystal edges with exciton dissociation ability are induced by the loss of BA ligands and can be removed by adding additional BA cations and regenerated by BA-to-MA cation exchange. This work presents a simple yet efficient method to develop and control the properties of crystal edges for better applications in 2D perovskite devices.