Inorganic Ruddlesden-Popper Faults in Cesium Lead Bromide Perovskite Nanocrystals for Enhanced Optoelectronic Performance

While the layered hybrid Ruddlesden-Popper (RP) halide perovskites have already established themselves as the frontrunners among the candidates in optoelectronics, their all-inorganic counterparts remain least explored in the RP-type perovskite family. Herein, we study and compare the optoelectronic properties of all-inorganic CsPbBr₃ perovskite nanocrystals (PNCs) with and without RP planar faults. We find that the RP-CsPbBr₃ PNCs possess both higher exciton binding energy and longer exciton lifetimes. The former is ascribed to a quantum confinement effect in the PNCs induced by the RP faults. The latter is attributed to a spatial electron–hole separation across the RP faults. A striking difference is found in the up-conversion photoluminescence response in the two types of CsPbBr₃ PNCs. For the first time, all-inorganic RP-CsPbBr₃ PNCs are tested in light-emitting devices and shown to significantly outperform the non-RP CsPbBr₃ PNCs.