Effects of many-body interactions on the transient optical properties of lead halide perovskites

Lead halide perovskites (LHPs) are emerging as promising candidates for use in various high-performance optoelectronic applications, yet their photophysics remains a topic of debate. Here, we theoretically investigated how the ultrafast optical properties of a few prototype LHPs are affected by many-body interactions, including the bandgap renormalization (BGR) effect, the band-filling (BF) effect, the free-carrier absorption effect, and the exciton effect, at carrier densities ranging from 10(16) to 10(19) cm(-3). The results show that the exciton absorption becomes more obvious near the bandgap with increasing exciton energy (as the halogen component of the LHP is varied from I to Cl). Transient reflectivity results indicate that the signal has one peak below the bandgap as a result of the BGR effect at low carrier densities and one valley above the bandgap originating from the BF effect at high carrier densities. In addition, the absorbance decreases with increasing the carrier density as a result of the BF effect because the filled energy levels are observed at 2 meV above the bottom of the conduction band. The results of the present work are expected to promote the application of LHPs in solar cells, light-emitting diodes, and other photoelectric devices.