Non-Convergence of Blinking Timescale of Twelve-Faceted Perovskite Nanocrystals Observed through Scanning Fluorescence Correlation Spectroscopy (sFCS) Study

Single-particle photoluminescence (PL) measurements have been extensively utilized to investigate the charge carrier dynamics and recombination processes in quantum dots (QDs). Among these techniques, single dot blinking studies are effective for probing relatively slower processes with timescales >10 milliseconds (ms), whereas fluorescence correlation spectroscopy (FCS) studies are suited for recording faster processes with timescales typically <1 ms. In this study, we utilized scanning FCS (sFCS) to bridge the ms gap, thereby enabling the tracking of carrier dynamics across an extended temporal window ranging from microsecond (µs) to subsecond. We compared our sFCS data recorded on surface-immobilized twelve-faceted CsPbBr3 dodecahedron perovskite nanocrystals (d-PNCs) with that of the solution phase FCS study, revealing qualitatively similar yet quantitatively different results. Latter is primarily attributed to the significantly varying immediate environments of PNCs in these two techniques, as well as the different temporal lengths of the observation windows available for the recording of carrier dynamics. The most intriguing finding of our study lies in the non-converging behavior of the blinking timescale (τR) even in sFCS, despite this technique providing an extended temporal window size (≤440 ms) for studying carrier dynamics. We attribute this observation to PL blinking following power law statistics. The consequence of power law blinking includes the mean ON/OFF duration of blinking persuasive to the experimental integration time, making blinking occur across all timescales.