Photoluminescence Blinking of Quantum Confined CsPbBr3 Perovskite Nanocrystals: Influence of Size

Quantum confined CsPbBr3 nanocrystals (NCs)with adjustablephotoluminescence (PL) in the range of 470-500 nm are particularlydesirable for applications in light-emitting diodes and many quantumtechnologies. Exploration of the full potential of these perovskiteNCs requires an understanding of the random fluctuation of their PLat the single-particle level, commonly termed as blinking. In thiswork, we study the PL blinking of quantum confined single NCs of CsPbBr3 of three different sizes between 3.80 and 5.90 nm in immobilizedand fluid conditions to understand the recombination pathways anddynamics of the photogenerated charge carriers. In the immobilizedstate, the PL intensity trajectories and PL lifetime-intensity distributionsof these single NCs reveal the contributions of both Auger recombinationand trapping of hot carriers to the PL fluctuation. The results suggesta higher carrier trapping rate constant for smaller NCs. The fluorescencecorrelation spectroscopy and fluorescence lifetime correlation spectroscopymeasurements on freely diffusing NCs show a higher off-state fractionand lower per-particle brightness of the smaller NCs. It is concludedthat a larger trap depth and higher probability density of the carriersat the surface in smaller NCs make the trapping process more feasibleand detrapping more difficult. The results provide first informationon the effect of size on PL blinking of the quantum confined CsPbBr3 NCs, and this knowledge is expected to be useful in betterdesigning photoluminescent samples of this class for optoelectronicapplications.