Syntheses of two-dimensional propylammonium lead halide perovskite microstructures by a solution route

Two-dimensional (2D) perovskite micro/nanostructures have drawn considerable attention worldwide for their unique optoelectronic properties and promising applications in nanoelectronics and nanophotonics. In this article, syntheses of 2D propylammonium lead halide perovskite microstructures are reported. The iodine-containing perovskite exhibits a flower-like hierarchical morphology with the "petals" consisting of approximately vertical-crossing ribbons. This compound possesses the chemical formula (C3H7NH3)(6)Pb4I14, with the structure consisting of both corner-sharing and face-sharing PbI6 octahedra to complete the 2D network. The hydrogen-bonding interactions between organic group C3H7NH3+ and bilateral nearest-neighboring perovskite sheets are deemed to be responsible for this structure. By contrast, the lead bromide perovskite displays a plate-like morphology and bears the formula (C3H7NH3)(2)PbBr4, with its structure containing purely corner-sharing PbBr6 octahedra. Optical measurements indicate that a more evident 2D exciton feature can be observed in (C3H7NH3)(2)PbBr4 than in (C3H7NH3)(6)Pb4I14. For (C3H7NH3)(2)PbBr4, photoluminescence (PL) measurement displays a strong emission peak at 419 nm, stemming from free exciton transition. PL decay analysis of the free exciton in (C3H7NH3)(2)PbBr4 shows its lifetime of about 16.4 ns. Our successful syntheses and preliminary optical investigations on such 2D perovskite nanostructures offer a new material for research on the fundamental properties of 2D perovskites and their potential applications in optoelectronic devices.