Strongly Confined and Spectrally Tunable CsPbBr₃ Quantum Dots for Deep Blue QD‐LEDs

Abstract

Despite recent advances, it is still difficult to fabricate deep blue‐emitting perovskite light‐emitting diodes (LEDs) that are immune to the color instability caused by halide mixing. This is largely because it is still challenging to achieve bright, stable, pure bromide perovskite materials with deep blue emission. Here, a novel strategy is reported for synthesizing ultrasmall CsPbBr3 quantum dots (QDs) under ambient conditions. Precise size control is used to tune the peak emission wavelengths, via the confinement effect, from 433 to 501 nm. These ultrasmall QDs, with sizes of 2–6 nm, exhibit ultralow trap density and stable photoluminescence quantum yields up to 94%, particularly in the deep blue spectral region (440–465 nm). QD‐LEDs fabricated with these materials achieve an external quantum efficiency of 1.0% at 459 nm. The exceptional control of the emission properties demonstrated here suggests a new strategy for building stable, efficient blue QD‐LEDs.

Color Tuning in Cesium Lead Halide Nanocrystals via A-Site Substitution as an Alternative Method for Achieving Spectrally Stable Blue Perovskite Nanocrystal Light-Emitting Diodes

“…Recently, a high-efficiency pure blue (465 nm) halide perovskite QD-LED with an EQE of 10% was reportedly produced using an in situ synthesis method . Nevertheless, colloidal quantum-confined CsPbBr 3 quantum dots generally require complex synthesis and separation methods and a large amount of insulating organic ligands such as oleic acid (OA) and oleylamine (OAm) that may hinder the performance of the resulting LEDs. − Additionally, size control for such samples can be challenging to achieve, and the sizes must remain stable during processing. A third, infrequently explored strategy to tune pure bromide perovskite NCs from green to blue is changing the A-site cations from the larger Cs + cations to smaller Rb + cations.…”

Cesium lead bromide perovskite nanocrystals synthesized via supersaturated recrystallization at room temperature: comparison of one-step and two-step processes

“…Green-emitting CsPbBr 3 NCs were tuned to a blue emitter by adjusting the stoichiometry of halide (bromide and chloride) anions. 12,13 However, LHP NCs with mixed halides are known to have drawbacks such as low defect tolerance of chlorine anions and phase instability upon exposure to light and/or voltage when applied as a blue light source in lighting and display technology. 13 The other strategy for blue-emitting LHP NCs relies on the quantum confinement effect, a unique property of low-dimensional semiconductors.…”

“…12,13 However, LHP NCs with mixed halides are known to have drawbacks such as low defect tolerance of chlorine anions and phase instability upon exposure to light and/or voltage when applied as a blue light source in lighting and display technology. 13 The other strategy for blue-emitting LHP NCs relies on the quantum confinement effect, a unique property of low-dimensional semiconductors. For example, strongly quantum-confined CsPbBr 3 NCs, such as dots, nanowires, nanoplatelets, and nanocubes, have been demonstrated as blue emitters.…”