Distinctive Bulk- and Surface-Specific Photoluminescence and Photocarrier Dynamics in CH3NH3PbI3 Perovskite

A precise understanding of the intrinsic photoluminescence (PL) and photocarrier dynamics of lead halide perovskites remains elusive, largely due to the heterogeneities at multiple length scales associated with the solution-processed sample preparation. We report the slow solvent-evaporation-assisted crystallization, yielding a high-quality CH3NH3PbI3 single crystal with crack-free flat pristine surfaces. The single crystal demonstrated photoluminescence as a function of wavelength with two components, which represent the bulk- and surface-specific emissions, respectively. By time-resolved photoluminescence analysis as a function of probed wavelengths, we revealed distinctive bulk- versus surface-specific photocarrier dynamics. The remarkably long and dominating photocarrier lifetime of ∼2.4 μs probed at the bulk-PL peak position, as opposed the counterpart associated with the surface-PL peak, strongly indicated a much delocalized physical scheme for photocarrier dynamics in the lattice interior, as opposed to the periphery. The lattice-periphery-induced local confinement effect on the photocarrier dynamics was further verified with a polycrystalline thin film sample, which demonstrated much shorter photocarrier lifetimes.