Cryogenic‐Temperature Thermodynamically Suppressed and Strongly Confined CsPbBr₃ Quantum Dots for Deeply Blue Light‐Emitting Diodes

Abstract

Suppressing the naturally ultrafast nucleation and growth rates of perovskite nanocrystals is a big challenge to develop high‐performance deeply blue perovskite light‐emitting diodes. Here, a cryogenic temperature thermodynamically suppressed synthetic strategy using liquid nitrogen is designed to obtain ultrasmall CsPbBr3 quantum dots (QDs; ≈3 nm). Due to its strong confinement effect, the as‐obtained CsPbBr3 QDs present strong deeply blue emission (≈460 nm) with a high quantum yield value of up to 98%, a large exciton binding energy of 301.6 meV, and excellent spectra stability for 60 d under atmosphere environment. This unprecedented regime indicates that cryogenic temperature can eliminate pre‐existing trap states and suppress the nonradiative process. Besides, the resultant perovskite light‐emitting diodes based on ultrasmall CsPbBr3 QDs show deeply blue emission (≈ 460 nm) with a Commission Internationale de l'Eclairage (CIE) color coordinate of (0.145, 0.054), better than the blue National Television Standards Committee (NTSC) standard. Evidently, this cryogenic temperature synthetic strategy will pave the way for the large‐scale synthesis of the strongly confined ultrasmall quantum dots systems and open the door for the development of next generation solid‐state lighting and displays.

Highly Efficient Pure‐Blue Perovskite Light‐Emitting Diode Leveraging CsPbBrxCl3−x/Cs4PbBrxCl6−x Nanocomposite Emissive Layer with Shallow Valence Band

“…Incorporation of Cl is a straightforward strategy to realize blue emission in perovskite materials. [8][9][10] Blue emissions can be obtained by simply adjusting the Cl ratio of the mixed halide (Br/Cl). However, because Cl vacancies are easily formed in the mixed halide (Br/Cl) perovskite system and can degrade the PLQY via defectmediated nonradiative recombination, it is pivotal to suppress Cl vacancies in highly luminescent blue-emitting perovskites.…”

Recent Advances in Blue Perovskite Quantum Dots for Light‐Emitting Diodes

“…[67] For PQDs, the excitons are strongly confined in three dimensions to form localized excitons that cannot migrate (Figure 3b). As a result, the excitons exhibit large binding energy up to hundreds of meV [69] and can achieve the maximum radiative recombination probability since the less dependence on charge carrier density. [67,70] In quantum-confined PQDs, the experimental and theoretical analyses confirm that the first-order excitonic radiative recombination of small-size PQDs dominates over non-radiative trap-assisted recombination at the low excitation density level.…”

“…Cao et al proposed a cryogenic temperature thermodynamically suppressed strategy via a liquid nitrogen treated solution to achieve defect-free CsPbBr 3 PQDs (Figure 7j). [69] The low reaction energy at cryogenic temperature suppressed the formation of defects, promoting the PL QY of ultrasmall PQDs (≈3 nm) up to 98%.…”

“…Up to now, only several successful PeLEDs based on quantum-confined CsPbBr 3 PQDs have been performed. [28,69,125] Bipolar-shell-resurfaced CsPbBr 3 PQDs presented excellent PL QY exceeding 90% and superior stability against ion exchange. [28] More importantly, the TEM images of the film indicated the highly ordered selfassembly of the PQDs.…”

“…j) Schematic illustration of liquid nitrogen-treated solution for ultrasmall CsPbBr 3 PQDs (left) and cryogenic temperature thermodynamically suppressed effect. Reproduced with permission [69]. Copyright 2021, Wiley-VCH.…”