Excitation Intensity Dependence of Photoluminescence Blinking in CsPbBr₃ Perovskite Nanocrystals

Abstract

Perovskite semiconductors have emerged as a promising class of materials for optoelectronic applications. Their favorable device performances can be partly justified by the defect tolerance that originates from their electronic structure. The effect of this inherent defect tolerance, namely the absence of deep trap states, on the photoluminescence (PL) of perovskite nanocrystals (NCs) is currently not well understood. The PL emission of NCs fluctuates in time according to power law kinetics (PL intermittency, or blinking), a phenomenon that has been explored over the past two decades in a vast array of nanocrystal (NC) materials. The kinetics of the blinking process in perovskite NCs have not been widely explored. Here, PL trajectories of individual orthorhombic cesium lead bromide (CsPbBr 3 ) perovskite NCs are measured using a range of excitation intensities. The power law kinetics of the bright NC state are observed to truncate exponentially at long durations, with a truncation time that decreases with increasing intensity before saturating at an intensity corresponding to an average formation of a single exciton. The results indicate that a diffusion-controlled electron transfer (DCET) mechanism is the most likely charge trapping process, while Auger autoionization plays a lesser role. The relevance of the multiple recombination centers (MRC) model to the results presented here cannot be ascertained, since the underlying switching mechanism is not currently available. Further experimentation and theoretical work are needed to gain a comprehensive understanding of the photophysics in these emerging materials.

Instantaneous, room-temperature, open-air atmosphere, solution-phase synthesis of perovskite quantum dots through halide exchange employing non-metal based inexpensive HCl/HI: ensemble and single particle spectroscopy

“…These high ON fraction values are mostly similar to the values obtained for the PQDs synthesized through the inert atmosphere, hot-injection synthesis. [36][37][38] This, in turn, demonstrates the ingenuity of the halide exchange process adopted herein. Thus, the IRTOA halide exchange reaction with inexpensive HX (X ¼ Cl/I) yields PQDs with equally good (if not better) optical properties.…”

“…S9 †). 38,39 The power law exponent (m) is <1.0 for the ON events (m ON ) and >1.50 for the OFF events (m OFF ) for all three PQDs (i.e., for all the samples, the m OFF magnitude is higher than m ON (Table 1)). As can be observed from Table 1, the 'm' value for a particular event (ON or OFF) does not change signicantly from PQD 3 to PQD 5 to PQD 6.…”

Memories in the photoluminescence intermittency of single cesium lead bromide nanocrystals

“…PL intermittency has been observed in cesium lead halide perovskite NCs [ 4 , [21][22][23][24][25] ] over the past few years. Different models that were initially proposed for II-VI semiconductor NCs [ 19 , 26 ] have been invoked to rationalize the PL blinking of these NCs.…”

“…For example, random charging and discharging followed by Auger nonradiative recombination has been used to explain the PL intermittency of cesium lead halide NCs at room temperature [ 21 , 27 ]. Diffusion-controlled electron transfer (DCET) has been proposed for the dominant charge trapping mechanism in order to explain the dependence of power-law kinetics of bright states on the excitation power [ 23 ].…”

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.…”