Exciton states in metal halide perovskites under the effect of carrier-longitudinal optical phonon coupling

Abstract

Exciton states are essential to comprehend the basal photoelectric properties in metal halide perovskites (MHPs) and provide reference for their future research, in which the exciton binding energy (EBE), determining the balance of the populations between excitons and free carriers, plays an important role in defining the optoelectronic utilization of MHPs. Thereby, we theoretically study the effects of bound potentials, due to the exciton coupling with the longitudinal optical (LO) phonon, between the electron and hole of the exciton on the EBE applying the variational method by using different effective potentials and two trail wavefunctions. We find that the EBE of this kind of materials is not only related to the chemical composition, but also remains inseparable from the space size, dielectric constant and LO-phonon energy, moreover, these correlations are better described by Barentzen potential. In addition, the results also show that the effects of carriers-LO-phonon coupling can explain the relationships between the EBE and exciton active range and effective Bohr radius to a certain extent, and can analyze their intrinsic correlation among these factors. These findings enable us to explain some experimental results and provide some help to understand optical electric dynamics in MHPs.