Photoluminescence Flickering and Blinking of Single CsPbBr₃ Perovskite Nanocrystals: Revealing Explicit Carrier Recombination Dynamics

Abstract

To obtain an in-depth understanding of the dynamics and mechanism of carrier recombination in CsPbBr 3 nanocrystals (NCs), we have investigated the photoluminescence (PL) of this material at the single-particle level using the time-tagged−time-resolved method. The study reveals two distinct types of PL fluctuations of the NCs, which are assigned to flickering and blinking. The flickering is found to be due to excess surface trap on the NCs, and the flickering single particles are transformed into blinking ones with significant enhancement of PL intensity and stability on postsynthetic surface treatment. Intensitycorrelated lifetime analysis of the PL time trace reveals both trapmediated nonradiative band-edge carrier recombination and positive trion recombination in single NCs. Dynamical and statistical analysis suggests a diffusive nature of the trap states to be responsible for the PL intermittency of the system. These findings throw light on the nature of the trap states, reveal the manifestation of these trap states in PL fluctuation, and provide an effective way to control the dynamics of CsPbBr 3 NCs.

Verification of Type-A and Type-B-HC Blinking Mechanisms of Organic–Inorganic Formamidinium Lead Halide Perovskite Quantum Dots by FLID Measurements

“…This may have occurred because the hot electrons relaxed much faster to RCs than to band-edges. It is interesting to note that among caesium (Cs), methylammonium (MA) and formarmidinium (FA) based lead halide perovskites, type B-HC is found for MA- 27 and FA-based perovskite (this work) but not for Cs-based perovskites 13,[22][23][24][25]28 . These results may suggest the different influence between organic (FA, MA) and inorganic cation (Cs) to PQD blinking behaviors.…”

“…These two types of blinking mechanisms could be used for conventional semiconductor QDs 15-20 and also, possibly, for PQDs 13,21-23 . In addition, several researchers have suggested in their recent publications, that the two types of blinking simultaneously contribute to PQD blinking [24][25][26][27] .Analysis of fluorescence lifetime intensity distribution (FLID) has been regarded as a very effective experimental approach to distinguish between these two types of blinking mechanisms 18,19 . While the FLID trajectory for type-A blinking is typically a curved line 18,19 , that of type-B blinking can be further divided into two sub www.nature.com/scientificreports www.nature.com/scientificreports/ algorithms, coded utilizing the MATLAB software, and fitted employing the ORIGIN 2016 software.…”

“…These two types of blinking mechanisms could be used for conventional semiconductor QDs 15-20 and also, possibly, for PQDs 13,21-23 . In addition, several researchers have suggested in their recent publications, that the two types of blinking simultaneously contribute to PQD blinking [24][25][26][27] .…”

“…Several scholars identified type-A blinking for PQDs using the FLID characteristics and assigned the observed short lifetimes to the trion 13,21,24 . However, the lifetimes of the PQD trion states have been reported to be vastly different, such as 170 ps 21 , 410 ps 28 , 2 ns 24,25 , and 5.8 ns 29 . These values could be comparable with the low-emission state lifetime in type B-BC blinking [23][24][25] .…”

“…However, the lifetimes of the PQD trion states have been reported to be vastly different, such as 170 ps 21 , 410 ps 28 , 2 ns 24,25 , and 5.8 ns 29 . These values could be comparable with the low-emission state lifetime in type B-BC blinking [23][24][25] . Moreover, the FLID trajectories of type-A blinking of PQDs in previous studies were not clearly verified compared to the conventional (cadmium chalcogenides) QD.…”