LAUSR

Hybrid organic–inorganic perovskites (CH3NH3PbI3) have gained prominence in recent years due to their fascinating electronic properties and potential for commercial application in photovoltaics and optoelectronics. One of their intriguing features is in the structure itself and the role played by the organic cation CH3NH3+ (MA+). In this study, we implement first-principles-based methods to take a static look at this dynamic system, which may shed some light on the preferential orientation of MA+ and its impact. We find there is a lattice energy gain in cubic CH3NH3PbI3, when going from a pristine host supercell with [100] MA+ orientation to a distorted host consisting of preferentially aligned MA+ and tilted PbI6 octahedra. Reoriented MA+ and octahedral tilting are also accompanied by larger number of (N–H3)···I hydrogen bonds. This lattice reconfiguration may support charge localization as evidenced by larger 216-atom supercell calculations. The localization behavior is a consequence of lattice polariza...