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.

Reversible CsPbBr3 ↔ CsPb2Br5 Transformation via Reverse Micellar Aqueous Solution

“…We further performed time-resolved PL spectroscopy to understand the excited state dynamics of the CsPbBr 3 /AOT/hexane solution before and after the treatment with the reverse micellar aqueous solution (Figure S2). The pristine CsPbBr3/AOT solution shows a biexponential decay with average lifetime of ∼8 ns, which agrees well with the lifetime of the CsPbBr 3 NCs. , In contrast, upon treatment with the reverse micellar aqueous solution, the lifetime decreases drastically, which can be fitted with a triexponential function, and an average lifetime of ∼1.6 ns is observed, agreeing with the fast nonradiative relaxation in the CsPb 2 Br 5 system. Importantly, the lifetime is found to be independent of the w 0 values, indicating that no further chemical transformation from the CsPb 2 Br 5 phase is happening.…”

Probing the Structural Degradation of CsPbBr3 Perovskite Nanocrystals in the Presence of H2O and H2S: How Weak Interactions and HSAB Matter

“…The emission spectrum is recorded by exciting the samples at 350 nm by keeping the slit widths in the emission and excitation chambers at 1 nm. The shorter FWHM is a clear indication that the synthesized nanocrystals are monodispersed with fewer surface defects. − Furthermore, the emission yield of the perovskite nanocrystals is obtained by following a relative method. The aqueous solution of fluorescein dye in 0.1 N NaOH (quantum yield 0.925) is used as the standard, and the quantum yield of the present perovskite nanocrystals is estimated as 0.55.…”

Weakly Confined Organic–Inorganic Halide Perovskite Quantum Dots as High-Purity Room-Temperature Single Photon Sources

“…CsPbBr 3 PQDs with size (3–7 nm) exhibit an average g (2) (0) ∼ 0.1 due to AR and low signal-to-noise ratio . Furthermore, reducing PQD sizes below their exciton Bohr diameter (BD) exacerbates blinking. ,− ,,,− This arises from the increased trap depth and higher carrier density at the surface of smaller QDs, rendering trapping more likely and detrapping more difficult …”

“…Until now, the most effective approach to achieve high-purity single photon emission with inorganic CsPbX 3 (X = Cl, Br, or I) PQDs is through employing strong quantum confinement to enhance the Auger recombination (AR) of biexcitons. 3,[9][10][11][12][13][14][15]22,23 The metric defining the single photon purity of a SPS is the second-order intensity correlation function, g (2) (0) ≈ 4τ XX /τ X , where g (2) (0) = 0 reflects the ideal case. 24 Here, τ XX (τ X ) is the biexciton (exciton) lifetime.…”