Photogeneration and recombination dynamics of trions and biexcitons in CsPbX₃nanocrystals revealed by double-pump transient-absorption spectroscopy

Lead halide perovskite nanocrystals (NCs) attract much attention because of their excellent optical properties such as high photoluminescence quantum yields. However, detailed dynamical processes of excitons, trions, and biexcitons have not been understood yet [1]. Here, we investigate the photogeneration and recombination dynamics of trions and biexcitons in all-inorganic perovskite CsPbX₃ (X = Cl, Br, I) NCs by conducting double-pump transient-absorption spectroscopy. In this method, the population of trions and biexcitons in NCs can be controlled by changing excitation intensity and time interval of two pump pulses. We revealed that Auger recombination of biexcitons and radiative and nonradiative recombination of trions determines ionization and neutralization processes in halide perovskite NCs [2]. In addition, we examined the difference in optical gain between single- and double-pump conditions. Our findings provide essential insights for low-threshold lasing.

[1] As a review, Y. Kanemitsu, J. Chem. Phys. (2019) in press.
[2] S. Nakahara et al., J. Phys. Chem. Lett., 10, 4731 (2019).