Quantum‐Dot Light‐Emitting Diodes for Outdoor Displays with High Stability at High Brightness

Abstract

Quantum dot light‐emitting diodes (QLEDs) are considered to be the candidate light sources with the most potential for applications in displays. Recent advances in luminance, external quantum efficiency (EQE), and even the operation lifetime of QLEDs have already satisfied the requirements for low‐light‐level displays. However, the short operation lifetime under high brightness limits the application of QLEDs for outdoor displays and lightings. Here, demonstrated are green QLEDs with a T95 operation lifetime reaching up to 2500 h at high brightness (1000 cd m−2) with a high peak EQE of 23.9%, current efficiency of 100.5 cd A−1, and low efficiency roll‐off at high current. Both the EQE and lifetime of the QLEDs are superior to those reported to date for all solution‐processed green QLEDs. These major advances are qualitatively attributed to the use of a shell‐tailoring strategy for producing compositional graded CdZnSe/ZnSe/ZnSeS/ZnS quantum dots with a high photoluminescence quantum yield, suppressed nonradiative Förster resonant energy transfer and Auger recombination, and favorable valence band alignment for enhanced hole injection. Collectively, this work represents a huge step forward in eventually realizing QLEDs for high‐brightness display and lighting applications.

Suppressing Förster Resonance Energy Transfer in Close‐Packed Quantum‐Dot Thin Film: Toward Efficient Quantum‐Dot Light‐Emitting Diodes with External Quantum Efficiency over 21.6%

“…When considering the additional light extraction caused by light interference, over 29% out‐coupling efficiency in QLEDs is reasonable. [ 44,45 ] To examine the repeatability, the EQE of 16 QLEDs from different fabrication batches were measured. As shown in Figure 4f, these devices exhibit a mean EQE of 20.63% with a low standard deviation of 0.6, indicating excellent device reproducibility.…”

Simple Synthesis of CuInS2/ZnS Core/Shell Quantum Dots for White Light-Emitting Diodes

“…The related size distribution of CIS/ZnS QDs ( Figure 2D ) is wide from 2.0 to 7.0 nm and the average size is about 4.37 nm. On the other hand, although CuInS 2 and ZnS have different crystal structures, their lattice mismatch is small, so that the ZnS shell is able to grow well on the surface of CuInS 2 crystals (Li et al, 2019 ). This small-lattice mismatch probably makes the core-shell structure difficult to observe.…”

Highly Efficient Near-Infrared Light-Emitting Diodes Based on Chloride Treated CdTe/CdSe Type-II Quantum Dots

“…As an alternative material, II-VI semiconductor quantum dots (QDs) demonstrate unique superiorities as NIR emitters, due to high PL QY, easily tunable size-dependent emissions, lowcost solution processability and scalable production of highquality QDs (Kwak et al, 2012;Shirasaki et al, 2012;Chen et al, 2013;Qin et al, 2013;Zhang et al, 2019). Recent advances in visible LEDs based on II-VI QDs (especially type I structure) have already satisfied the requirements for display and solid-state lighting (Dai et al, 2014;Yang et al, 2015;Zhang et al, 2017;Li et al, 2019;Shen et al, 2019;Song J. et al, 2019). In particular, very recently, the novel strategy that optimizes shell materials to get a better energy level matching with the highest occupied molecular orbital (HOMO) of the hole transport layers facilitates their industrialization (Yang et al, 2015;Li et al, 2019;Shen et al, 2019).…”

“…Recent advances in visible LEDs based on II-VI QDs (especially type I structure) have already satisfied the requirements for display and solid-state lighting (Dai et al, 2014;Yang et al, 2015;Zhang et al, 2017;Li et al, 2019;Shen et al, 2019;Song J. et al, 2019). In particular, very recently, the novel strategy that optimizes shell materials to get a better energy level matching with the highest occupied molecular orbital (HOMO) of the hole transport layers facilitates their industrialization (Yang et al, 2015;Li et al, 2019;Shen et al, 2019). However, simple tuning the size of high-quality type-I QDs could not modulate their emission wavelengths to deepred or near-infrared regions, which restricted their application in NIR fields.…”