Blinking suppression and biexcitonic emission in thick-shell CdSe/CdS nanocrystals at cryogenic temperature

Abstract

The fluorescence of single colloidal thick-shell CdSe/CdS nanocrystals (NCs), at cryogenic temperature (4 K) and room temperature (RT), is studied using the intensity autocorrelation function (ACF) and lifetime measurements. The radiative and Auger decay rates corresponding to the desexcitation of the charged biexcitonic state are determined through an original method of photon postselection. Especially, the charged biexciton quantum yield increases from about 15% at RT to 60% at 4 K. The high inhibition of Auger recombination already observed for the trion state of CdSe/CdS NCs at low temperature is also demonstrated for the charged biexcitonic state. At 4 K, the ACF is equal to 1 for time scales ranging from 50 ns to 200 ms. In contrast with RT operation, the intensity of the trion emission is then perfectly stable and no blinking is observed. All the results highlight the strong confinement of the charge carriers in the CdSe core.

Evidence in Support of Exciton to Ligand Vibrational Coupling in Colloidal Quantum Dots

“…154,160 The Dubertret group displayed a new way for analyzing blinking statistics 161 using CdSe/giant-CdS CQDs, showing non-zero emission for single and biexciton and their charged analogs. 162 The Klimov group displayed nearly unity yield of biexciton emission, 163 and decent emission intensity (so called "gray" emission) from positive and negatively charged exaction. 59 The Guyot-Sionnest group investigated the emission intensity of alloyed CdSeS/ZnS heterostructure under electrochemical control.…”

CdSe/CdS Dot‐in‐Rods Nanocrystals Fast Blinking Dynamics.

“…[28,29,30,31,32,33,34,35] The autocorrelation method is less straightforward than the distribution of event durations, but it does not suffer from any a priori assumptions due to the time bin and it yields information at short timescales not reachable when binning the signal. [28,29,30,31,32,33,34,35] The autocorrelation method is less straightforward than the distribution of event durations, but it does not suffer from any a priori assumptions due to the time bin and it yields information at short timescales not reachable when binning the signal.…”

Autocorrelation Analysis for the Unbiased Determination of Power-Law Exponents in Single-Quantum-Dot Blinking

“…In fact, residual OFF state emission manifests itself in the contour plot of Fig. 3 As a consequence, the approach is also suitable for analyzing recently developed types of giantshell [41][42][43] or alloyed QDs, 44 both of which having a high dark-state-emission efficiency.…”