Visualizing Carrier Diffusion in Individual Single-Crystal Organolead Halide Perovskite Nanowires and Nanoplates

Single-crystal CH3NH3PbX3 (X = I–, Cl–, Br–) perovskite nanowires (NWs) and nanoplates (NPs), which demonstrate ultracompact sizes and exceptional photophysical properties, offer promises for applications in nanoscale photonics and optoelectronics. However, traditional electronic and transient techniques are limited by the dimensions of the samples, and characterizations of the carrier behavior (diffusion coefficient, charge mobility and diffusion length) in these NWs and NPs are extremely difficult. Herein, we report the direct visualization of the carrier diffusion process in individual single-crystal CH3NH3PbI3 and CH3NH3PbBr3 NWs and NPs using time-resolved and photoluminescence-scanned imaging microscopy. We report the diffusion coefficient (charge motility), which varies significantly between different NWs and NPs, ranging from 1.59 to 2.41 cm2 s–1 (56.4 to 93.9 cm2 V–1 s–1) for CH3NH3PbI3 and 0.50 to 1.44 cm2 s–1 (19.4 to 56.1 cm2 V–1 s–1) for CH3NH3PbBr3 and find this variation is independent of the shape and size of the sample. The average diffusion length is 14.0 ± 5.1 μm for CH3NH3PbI3 and 6.0 ± 1.6 μm for CH3NH3PbBr3. These results provide information that is essential for the practical applications of the single-crystal perovskite NWs and NPs, and the imaging microscopy may also be applicable to other optoelectronic materials.