Reduction of Optical Gain Threshold in CsPbI3 Nanocrystals Achieved by Generation of Asymmetric Hot-Biexcitons

• DOI: 10.1021/acs.nanolett.0c01079
• Publication Date: 2020-04-28T19:23:36Z
• Authors: Etsuki Kobiyama; Hirokazu Tahara; Ryota Sato; Masaki Saruyama; Toshiharu Teranishi; Yoshihiko Kanemitsu
• Keywords: 0301 basic medicine; 03 medical and health sciences; 7. Clean energy

Lead halide perovskite nanocrystals (NCs) are a class of promising light-emitting materials and have been considered as gain media in lasers. Strong exciton-exciton interactions in NCs cause an energy shift of the lowest optical transition and affect the optical gain threshold. Here, we clarify the dynamics of exciton-exciton interactions in highly photoexcited CsPbI3 NCs by double-pump transient absorption spectroscopy. This method provides control over the population of each excited state by varying the time interval between the two pump pulses. We find that the band-edge energy shift induced by the formation of asymmetric hot-biexcitons (comprising one ground-state exciton and one hot exciton) is smaller than that induced by hot excitons and hot biexcitons in the ensemble. We demonstrate that the generation of asymmetric hot-biexcitons reduces the optical gain threshold in the CsPbI3 NC ensemble.