Strongly luminescent and highly stable CsPbBr3/Cs4PbBr6 core/shell nanocrystals and their ultrafast carrier dynamics

All-inorganic lead halide perovskites nanocrystals (NCs) have been demonstrated to be promising candi-dates for optoelectronic devices, but preparing perovskite NCs with high photoluminescence quantum yields (PLQYs) and excellent stability has been a challenge. In this work, CsPbBr3/Cs4PbBr6 core/shell NCs with a PLQYs of 87.23% and long-term stability in ambient environments was prepared by room tem-perature inverse microemulsion method. The excellent stability of the sample was attributed to the pro-tection of Cs4PbBr6, and higher PLQYs could be owing to the passivation effect of the core/shell structure. To illustrate the distribution of photogenerated carrier in the core/shell structure, a confined excitons model was proposed based on time-resolved PL and temperature dependent PL measurements. Femtosecond time-resolved transient absorption spectra measurements were performed upon different excitation wa-velength to unveil the photogenerated carrier dynamics in core/shell NCs. Upon 300 nm excitation, a carrier transfer process with the time of 3.18 ps from shell to core layer was observed. Furthermore, both two-and three-photon absorption PL was discovered in core/shell NCs, further verifying the carrier transfer process.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

This work successfully prepared CsPbBr3/Cs4PbBr6 core/shell nanocrystals with high photoluminescence quantum yields (87.23%) and long-term stability in ambient environments using a room temperature inverse microemulsion method. The stability was attributed to the protection of Cs4PbBr6, while the high photoluminescence quantum yields were due to the passivation effect of the core/shell structure.