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

Abstract

Quantum confined CsPbBr3 nanocrystals (NCs) with adjustable photoluminescence (PL) in the range of 470–500 nm are particularly desirable for applications in light-emitting diodes and many quantum technologies. Exploration of the full potential of these perovskite NCs requires an understanding of the random fluctuation of their PL at the single-particle level, commonly termed as blinking. In this work, we study the PL blinking of quantum confined single NCs of CsPbBr3 of three different sizes between 3.80 and 5.90 nm in immobilized and fluid conditions to understand the recombination pathways and dynamics of the photogenerated charge carriers. In the immobilized state, the PL intensity trajectories and PL lifetime-intensity distributions of these single NCs reveal the contributions of both Auger recombination and trapping of hot carriers to the PL fluctuation. The results suggest a higher carrier trapping rate constant for smaller NCs. The fluorescence correlation spectroscopy and fluorescence lifetime correlation spectroscopy measurements on freely diffusing NCs show a higher off-state fraction and lower per-particle brightness of the smaller NCs. It is concluded that a larger trap depth and higher probability density of the carriers at the surface in smaller NCs make the trapping process more feasible and detrapping more difficult. The results provide first information on the effect of size on PL blinking of the quantum confined CsPbBr3 NCs, and this knowledge is expected to be useful in better designing photoluminescent samples of this class for optoelectronic applications.