Fluorescence Blinking Beyond Nanoconfinement: Spatially Synchronous Intermittency of Entire Perovskite Microcrystals

Abstract

Abrupt fluorescence intermittency or blinking is long recognized to be characteristic of single nano-emitters. Extended quantum-confined nanostructures also undergo spatially heterogeneous blinking; however, there is no such precedent in dimensionally unconfined (bulk) materials. Herein, we report multi-level blinking of entire individual organo-lead bromide perovskite microcrystals (volume=0.1-3 μm ) under ambient conditions. Extremely high spatiotemporal correlation (>0.9) in intracrystal emission intensity fluctuations signifies effective communication amongst photogenerated carriers at distal locations (up to ca. 4 μm) within each crystal. Fused polycrystalline grains also exhibit this intriguing phenomenon, which is rationalized by correlated and efficient migration of carriers to a few transient nonradiative traps, the nature and population of which determine blinking propensity. Observation of spatiotemporally correlated emission intermittency in bulk semiconductor crystals opens the possibility of designing novel devices involving long-range (mesoscopic) electronic communication.

Synthesis and Localized Photoluminescence Blinking of Lead‐Free 2D Nanostructures of Cs3Bi2I6Cl3 Perovskite

“…Notably, the nature of photoluminescence fluctuation does not allow us to define a clear on, and off‐state for the emissive domains as the intensity fluctuations do not follow a typical two‐step process with a sharp transition between a distinct on and off state. Similar nature of PL fluctuation in perovskite microcrystals has been observed in a few recent studies, but a clear understanding of their origin is still under investigation . There are few possible explanations to this fact: (1) as discussed in the case of NCs, the time duration of completely not‐emissive off state could be much shorter than our experimental integration time.…”

Microscopic insight into non-radiative decay in perovskite semiconductors from temperature-dependent luminescence blinking

“…Figure 1j), they cannot be the only source of irregularities in the temperature dependent PL quantum yield. Direct evidence for the influence of individual quenching sites is also given by the pronounced blinking behavior 23,25–30 . Below we will characterize the temperature dependence of blinking in order to establish its connection to the PL quantum yield.…”

“…Dependence of non-radiative recombination on local properties becomes apparent in the spatially inhomogeneous PL 7,9,23,24 . Some of these PL quenching channels are of extraordinary efficiency (therefore called ‘super traps’) leading to PL blinking observed in individual crystals and films 23,25–30 . Obviously, there are several sources of non-radiative recombination which are, to a large extent, unexplained.…”

“…This means that the non-radiative decay in the particle undergoes large fluctuations due to, for example, a few non-radiative centers switching between their active and passive states. PL blinking has also been observed in quite large objects such as perovskite microrods 23 , microcrystals 30 , and graphene oxide layers 35 , where concentration and spatial distribution of the non-radiative centers can be assessed by luminescence microscopy either directly or using optical super-resolution methods 23,25,36 . As fluorescence blinking of individual molecules allowed for breaking of the diffraction limit in optical microscopy 37 , fluctuating quenching processes in a semiconductor can potentially allow for resolving the properties of individual recombination channels that otherwise are convoluted in the ensemble-averaged rates.…”

Revealing Dynamic Effects of Mobile Ions in Halide Perovskite Solar Cells Using Time‐Resolved Microspectroscopy

“…Different from the conventional semiconductor QDs, significant fluorescence intermittency has been observed in perovskite grains and rods that have a size of hundreds of nanometers or even micrometers. [ 69–72 ] Wen et al. [ 69 ] found fluorescence intermittency in individual perovskite grains in vapor‐assisted fabricated MAPbBr 3 thin film via a confocal microscopy, which is composed of nanoparticles (grains) in close contact with each other, as shown in Figure A.…”