Polymer-Controlled Growth and Wrapping of Perovskite Single Crystals Leading to Better Device Stability and Performance

A commodity-scale polymer is used for controlling the nucleation and growth of single crystals of organolead halide perovskite. The polymer [polystyrene (PS)] cross-links and strongly interacts with PbI2 and MAI (MAPbI3 perovskite precursors) resulting in the control of the crystallization process. The PS concentration modulates the nucleation time, crystal size, and the number of perovskite single crystals. In addition, the PS-based MAPbI3 crystals show an enhanced performance as well as improved thermal and environmental stability. Specifically, the PS-MAPbI3 crystals show 3 times higher photocurrent than plain MAPbI3 crystals and maintain a stable structure for more than 50 days (1200 h) under continuous 0.1 sun illumination in the air with a relative humidity of 40–45%. The improved performance and stability are attributed to the direct interaction between the PS and perovskite, which greatly reduces the ion migration, defect traps, and charge recombination and improves the carrier mobility and lifetime.