Non-convergence of the blinking timescale of twelve-faceted perovskite nanocrystals observed through an advanced fluorescence correlation spectroscopy study

Abstract

Single-particle photoluminescence measurements have been extensively utilized to investigate the charge carrier dynamics in quantum dots (QDs). Among these techniques, single dot blinking studies are effective for probing relatively slower processes with timescales >10 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 μs to subsecond. We compared the sFCS data recorded on surface-immobilized twelve-faceted CsPbBr₃ dodecahedron perovskite nanocrystals (d-PNCs) with the FCS data of the same nanocrystals in the solution phase. Although the two datasets exhibited similarities in a qualitative sense, they revealed notable quantitative differences. This is primarily attributed to the significantly varying immediate environments of PNCs in these two techniques, as well as the different temporal sizes of the observation windows available for the recording of carrier dynamics. The most intriguing finding of our study lies in the non-converging blinking timescale (τ_R) of d-PNCs in sFCS, despite this technique providing an extended temporal window size (≤328 ms) for studying carrier dynamics. We attribute this observation to PL blinking following power-law statistics, which causes the mean ON/OFF duration of blinking persuasive to the experimental integration time, making blinking occur across all timescales.