Revealing Explicit Microsecond Carrier Diffusion from One Emission Center to Another in an All-Inorganic Perovskite Nanocrystal.

Abstract

Blinking of freely diffusing CsPbBr3 nanocrystals (NCs) is studied using fluorescence lifetime correlation spectroscopy (FLCS). Emitted photons from each NCs are assigned to an emission state (exciton or trap) based on their lifetime. Subsequently, an intrastate autocorrelation function (ACF) and an interstate cross-correlation function (CCF) are constructed. Fitting of the AFCs with an analytical model shows that, at low excitation power, the microsecond blinking timescale of the exciton state matches well with that of the trap state. Most interestingly, both of those timescales further correlate with the microsecond growth timescale of the CCF. The strong anti-correlation of the CCF along with the stretched exponential nature of the blinking kinetics confirms the involvement of carrier diffusion and dispersive trap states in NC blinking. At high excitation power, enhanced sample heterogeneity causes a more dispersive blinking. To the best of our knowledge, this is the first report of a NC blinking study using a single-molecule-based FLCS technique.