Carrier recombination dynamics in [MAPbCl3]x[CsPbBr3]1-x shell-passivated CsPbBr3 single crystals

As one of the commonly used methods for surface passivation of semiconductors, a heterostructure method was developed in this work to passivate surface traps of CsPbBr3 single crystals (SCs), and further, this method was correlated with carrier recombination processes. Herein, carrier recombination processes in bare and [MAPbCl3]0.34[CsPbBr3]0.66-covered CsPbBr3 SCs were studied using time-resolved spectroscopic techniques, including steady-state and time-resolved photoluminescence (TRPL) spectroscopy and time-resolved microwave photoconductivity (TRMC). By comparing the kinetics of TRPL and TRMC, we concluded that surface hole-trapping process dominates the TRPL kinetics of bare CsPbBr3 SCs and surface electron-trapping process dominates the slower decay component in TRMC. By studying carrier recombination processes of CsPbBr3 SCs with and without choline bromide (CB) additives, we found that the use of CB could introduce additional surface electron and hole traps. For CsPbBr3 SCs with a shell, we observed charge carrier transfer from the shell to the CsPbBr3 crystal. We found that the [MAPbCl3]0.34[CsPbBr3]0.66 shell can reduce the electron-trapping and hole-trapping rates by 2.2 times and 5.2 times, respectively, indicating that the [MAPbCl3]0.34[CsPbBr3]0.66 shell can passivate the surface traps of CsPbBr3 crystals effectively.