Dynamic and giant bandgap renormalization dictates the transient optical response in perovskite quantum dots

Abstract

Transient optical response in perovskite quantum dots (QDs) has remained elusive until now, which hinders their full utilization in optoelectronics. Herein, we reveal that the bandgap renormalization (BGR) dictates the main spectral and dynamical features of transient response in CsPbBr3 QDs. By monitoring the absorption spectral evolution of the monodispersed QDs, the representative BGR is explicitly observed, giving rise to the photoinduced absorption at the higher energy side of the lowest exciton peak in transient absorption spectroscopy. The BGR gradually increases upon photoexcitation as a result of the carrier distribution dependent screening effect. We further demonstrate that the BGR arises from both Coulomb screening and phonon heating under high pump intensities in CsPbBr3 QDs. The synergistic effect leads to the giant BGR energy (ΔE > 60 meV) and the unconventional relationship of ΔE ∝ n1/2, where n is the carrier density. These findings are important for the fundamental understanding and potential applications of the emerging halide perovskite semiconductors.