CsPbBr Nanocrystal/MO (M = Si, Ti, Sn) Composites: Insight into Charge-Carrier Dynamics and Photoelectrochemical Applications.

Though coating CsPbBr nanocrystal (NC) with an outer layer has been regarded as an effective strategy to address its instability issues, deep investigations into the electronic interaction between CsPbBr NC and coating layer have yet to be conducted. In this study, the dynamics of hot carrier and charge carrier of CsPbBr nanocrystal with various MO (M = Si, Ti, Sn) coating layers have been comprehensively studied. Combined transient optical characterizations (time-resolved photoluminescence and ultrafast transient absorption) and photoelectrochemical measurements reveal that coating with insulating SiO accelerates the hot carrier relaxation and enhances the radiative recombination by passivating surface traps, whereas efficient charge-carrier separation and extraction are observed after coating with SnO and TiO. The electron injection from CsPbBr NC to SnO (1.14 × 10 s) is 2-fold faster than to TiO (5.4 × 10 s) owing to the lower conduction band edge and the higher electron mobility of SnO. Particularly, the first time fabricated CsPbBr NC/SnO composite exhibits superior stability against UV light and moisture, as well as the best photocurrent response in this study. This work has implied that rational design of the coating layer for perovskite NC can not only improve the stability but also tailor the electronic and optoelectronic properties for various applications.