Abstract
As one of the emerging two-dimensional lead halide materials,lead iodide(PbI2)nanosheets have proven to possess strong application potential in the fields of high-energy radiation detection and highly efficient perovskite solar cells.However,the underlying photophysical properties such as hot-exciton-related carrier dynamics remain unclear for PbI2 nanosheets.Here,we report the exciton dynamics of a single PbI2 nanoflake prepared by an aqueous solution method.Through a three-dimensional(3D)diffusion model,we obtain the exciton annihilation radius and diffusion coefficient of a single PbI2 nanoflake under non-resonant and resonant excitation conditions of band-edge exciton state.As initial exciton densities increase,we find the carrier recombination mechanism for a single PbI2 nanoflake gradually changes from exciton-exciton annihilation to free-carrier recombination.Finally,we reveal the room-temperature circular polarization of a single PbI2 nanoflake is due to free-carrier recombination with a band-edge exciton dissociation time of～120 fs under the resonant excitation condition.
基金项目
National Natural Science Foundation of China(62175088)
National Natural Science Foundation of China(61927814)
National Natural Science Foundation of China(21773087)
National Natural Science Foundation of China(21603083)
National Natural Science Foundation of China(21903035)
China Postdoctoral Science Foundation(2016M590259)
万方数据