Photoluminescence Blinking Revealing Static and Dynamic Heterogeneity of the Hole Transfer Process in Phenothiazine-Adsorbed FAPbBr3 Single Nanocrystals

Abstract

Lead halide perovskites are perhaps the most important substances for solar photovoltaic applications in recent times. The extraction or transfer of the electrons and holes produced on photoexcitation of these perovskites is a key process in this regard. Here, we investigate how hole transfer from FAPbBr3 to adsorbed phenothiazine (PTZ) influences the photoluminescence (PL) blinking dynamics of FAPbBr3-PTZ single nanocrystals (NCs) in immobilized and fluid conditions. In the immobilized state, while the single FAPbBr3 NCs show two-state (on–off) blinking, the FAPbBr3-PTZ single NCs exhibit a complex blinking pattern with several levels of PL intensity due to the hole transfer process. Analysis of the PL blinking data reveals the dispersive/heterogeneous nature of the hole transfer dynamics. Both particle-to-particle variation and time-dependent variation of the hole transfer rate of any given single NC are observed. Fluorescence correlation spectroscopy studies in the fluid state confirm this dispersive nature of the hole transfer dynamics, indicating the formation of a short-lived (<100 ns) charge-separated state, FAPbBr3–-PTZ+.