Quantum dots are a unique class of emitters with size‐tunable emission wavelengths, saturated emission colors, near‐unity luminance efficiency, inherent photo‐ and thermal‐ stability and excellent ...solution processability. Quantum dots have been used as down‐converters for back‐lighting in liquid‐crystal displays to improve color gamut, leading to the booming of quantum‐dot televisions in consumer market. In the past few years, efficiency and lifetime of electroluminescence devices based on quantum dots achieved tremendous progress. These encouraging facts foreshadow the commercialization of quantum‐dot light‐emitting diodes (QLEDs), which promises an unprecedented generation of cost‐effective, large‐area, energy‐saving, wide‐color‐gamut, ultra‐thin and flexible displays. Here we provide a Progress Report, covering interdisciplinary aspects including material chemistry of quantum dots and charge‐transporting layers, optimization and mechanism studies of prototype devices and processing techniques to produce large‐area and high‐resolution red‐green‐blue pixel arrays. We also identify a few key challenges facing the development of active‐matrix QLED displays.
The dawn of commercialization for large‐area quantum‐dot light‐emitting‐diode (QLED) displays is coming, as indicated by the recent impressive advancements of both the efficiency and lifetime of QLEDs. The progress in materials chemistry of quantum dots and charge‐transporting layers, device engineering and quenching mechanisms of QLEDs, and patterning techniques to realize high‐resolution arrays of red‐green‐blue pixels is discussed.
Metal halide perovskites have shown promising optoelectronic properties suitable for light-emitting applications. The development of perovskite light-emitting diodes (PeLEDs) has progressed rapidly ...over the past several years, reaching high external quantum efficiencies of over 20%. In this Review, we focus on the key requirements for high-performance PeLEDs, highlight recent advances on materials and devices, and emphasize the importance of reliable characterization of PeLEDs. We discuss possible approaches to improve the performance of blue and red PeLEDs, increase the long-term operational stability and reduce toxicity hazards. We also provide an overview of the application space made possible by recent developments in high-efficiency PeLEDs.
Colloidal quantum dots are promising emitters for quantum-dot-based light-emitting-diodes. Though quantum dots have been synthesized with efficient, stable, and high colour-purity photoluminescence, ...inheriting their superior luminescent properties in light-emitting-diodes remains challenging. This is commonly attributed to unbalanced charge injection and/or interfacial exciton quenching in the devices. Here, a general but previously overlooked degradation channel in light-emitting-diodes, i.e., operando electrochemical reactions of surface ligands with injected charge carriers, is identified. We develop a strategy of applying electrochemically-inert ligands to quantum dots with excellent luminescent properties to bridge their photoluminescence-electroluminescence gap. This material-design principle is general for boosting electroluminescence efficiency and lifetime of the light-emitting-diodes, resulting in record-long operational lifetimes for both red-emitting light-emitting-diodes (T
> 3800 h at 1000 cd m
) and blue-emitting light-emitting-diodes (T
> 10,000 h at 100 cd m
). Our study provides a critical guideline for the quantum dots to be used in optoelectronic and electronic devices.
We introduce stoichiometry control within both core and shell regions of InP/ZnSe/ZnS core/shell/shell quantum dots (QDs) to advance their properties drastically, approaching those of ...state-of-the-art CdSe-based QDs. The resulting QDs possess near-unity photoluminescence quantum yield, monoexponential decay dynamics, narrow line width, and nonblinking at a single-dot level. Quantum-dot light-emitting diodes (QLEDs) with the InP/ZnSe/ZnS core/shell/shell QDs as emitters exhibit a peak external quantum efficiency of 12.2% and a maximum brightness of >10 000 cd m–2, greatly exceeding those of the Cd/Pb-free QLEDs reported in literature. These results pave the way toward Cd/Pb-free QDs as outstanding optical and optoelectronic materials.
Quantum Dots for Display Applications Shu, Yufei; Lin, Xing; Qin, Haiyan ...
Angewandte Chemie International Edition,
December 7, 2020, Letnik:
59, Številka:
50
Journal Article
Recenzirano
This article offers a materials‐chemistry perspective for colloidal quantum dots (QDs) in the field of display, including QD‐enhanced liquid‐crystal‐display (QD‐LCD) and QD‐based ...light‐emitting‐diodes (QLEDs) display. The rapid successes of QDs for display in the past five years are not accidental but have a deep root in both maturity of their synthetic chemistry and their unique chemical, optical, and optoelectronic properties. This article intends to discuss the natural match of QD emitters for display and chemical means to eventually bring about their full potential.
This Minireview offers a materials‐chemistry perspective on colloidal quantum dots (QD) for display applications, including QD‐enhanced liquid‐crystal‐displays (QD‐LCD) and QD‐based light‐emitting‐diodes (QLEDs) displays. By illustrating correlations between various display key parameters and QD structures/properties, this perspective further demonstrates the importance of tailored design of QDs for specific applications.
Electroluminescence of colloidal nanocrystals promises a new generation of high-performance and solution-processable light-emitting diodes. The operation of nanocrystal-based light-emitting diodes ...relies on the radiative recombination of electrically generated excitons. However, a fundamental question-how excitons are electrically generated in individual nanocrystals-remains unanswered. Here, we reveal a nanoscopic mechanism of sequential electron-hole injection for exciton generation in nanocrystal-based electroluminescent devices. To decipher the corresponding elementary processes, we develop electrically-pumped single-nanocrystal spectroscopy. While hole injection into neutral quantum dots is generally considered to be inefficient, we find that the intermediate negatively charged state of quantum dots triggers confinement-enhanced Coulomb interactions, which simultaneously accelerate hole injection and hinder excessive electron injection. In-situ/operando spectroscopy on state-of-the-art quantum-dot light-emitting diodes demonstrates that exciton generation at the ensemble level is consistent with the charge-confinement-enhanced sequential electron-hole injection mechanism probed at the single-nanocrystal level. Our findings provide a universal mechanism for enhancing charge balance in nanocrystal-based electroluminescent devices.
Solution-processed optoelectronic and electronic devices are attractive owing to the potential for low-cost fabrication of large-area devices and the compatibility with lightweight, flexible plastic ...substrates. Solution-processed light-emitting diodes (LEDs) using conjugated polymers or quantum dots as emitters have attracted great interest over the past two decades. However, the overall performance of solution-processed LEDs--including their efficiency, efficiency roll-off at high current densities, turn-on voltage and lifetime under operational conditions-remains inferior to that of the best vacuum-deposited organic LEDs. Here we report a solution-processed, multilayer quantum-dot-based LED with excellent performance and reproducibility. It exhibits colour-saturated deep-red emission, sub-bandgap turn-on at 1.7 volts, high external quantum efficiencies of up to 20.5 per cent, low efficiency roll-off (up to 15.1 per cent of the external quantum efficiency at 100 mA cm(-2)), and a long operational lifetime of more than 100,000 hours at 100 cd m(-2), making this device the best-performing solution-processed red LED so far, comparable to state-of-the-art vacuum-deposited organic LEDs. This optoelectronic performance is achieved by inserting an insulating layer between the quantum dot layer and the oxide electron-transport layer to optimize charge balance in the device and preserve the superior emissive properties of the quantum dots. We anticipate that our results will be a starting point for further research, leading to high-performance, all-solution-processed quantum-dot-based LEDs ideal for next-generation display and solid-state lighting technologies.
Solution-processed metal-halide perovskites are emerging as one of the most promising materials for displays, lighting and energy generation. Currently, the best-performing perovskite optoelectronic ...devices are based on lead halides and the lead toxicity severely restricts their practical applications. Moreover, efficient white electroluminescence from broadband-emission metal halides remains a challenge. Here we demonstrate efficient and bright lead-free LEDs based on cesium copper halides enabled by introducing an organic additive (Tween, polyethylene glycol sorbitan monooleate) into the precursor solutions. We find the additive can reduce the trap states, enhancing the photoluminescence quantum efficiency of the metal halide films, and increase the surface potential, facilitating the hole injection and transport in the LEDs. Consequently, we achieve warm-white LEDs reaching an external quantum efficiency of 3.1% and a luminance of 1570 cd m
at a low voltage of 5.4 V, showing great promise of lead-free metal halides for solution-processed white LED applications.
The emergence of inorganic–organic hybrid perovskites, a unique class of solution-processable crystalline semiconductors, provides new opportunities for large-area, low-cost and colour-saturated ...light-emitting diodes (LEDs) ideal for display and solid-state lighting applications1. However, the performance of blue perovskite LEDs (PeLEDs)2–11 is far inferior to that of their near-infrared, red and green counterparts12–19, strongly limiting the practicality of the PeLED technology. Here, we demonstrate blue PeLEDs emitting at 483 nm with colour coordinates of (0.094, 0.184) and operating with a peak external quantum efficiency of up to 9.5% at a luminance of 54 cd m–2. The devices have a T50 lifetime of 250 s for an initial brightness of 100 cd m–2. The efficient blue electroluminescence originates from a structure of quantum-confined perovskite nanoparticles embedded within quasi-two-dimensional phases with higher bandgaps, prepared by an antisolvent processing scheme. Our work paves the way towards high-performance PeLEDs in the blue region.
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