Advances and Challenges in Heavy-Metal-Free InP Quantum Dot Light-Emitting Diodes

Abstract

Light-emitting diodes based on colloidal quantum dots (QLEDs) show a good prospect in commercial application due to their narrow spectral linewidths, wide color range, excellent luminance efficiency, and long operating lifetime. However, the toxicity of heavy-metal elements, such as Cd-based QLEDs or Pb-based perovskite QLEDs, with excellent performance, will inevitably pose a serious threat to people’s health and the environment. Among heavy-metal-free materials, InP quantum dots (QDs) have been paid special attention, because of their wide emission, which can, in principle, be tuned throughout the whole visible and near-infrared range by changing their size, and InP QDs are generally regarded as one of the most promising materials for heavy-metal-free QLEDs for the next generation displays and solid-state lighting. In this review, the great progress of QLEDs, based on the fundamental structure and photophysical properties of InP QDs, is illustrated systematically. In addition, the remarkable achievements of QLEDs, based on their modification of materials, such as ligands exchange of InP QDs, and the optimization of the charge transport layer, are summarized. Finally, an outlook is shown about the challenge faced by QLED, as well as possible pathway to enhancing the device performance. This review provides an overview of the recent developments of InP QLED applications and outlines the challenges for achieving the high-performance devices.

Synthesis, Surface Chemistry, and Fluorescent Properties of InP Quantum Dots

“…There are a number of recent reviews that have focused either more broadly on multiple semiconductor QD materials ,− or more exclusively on InP QD’s use in a specific application such as QLEDs, , displays, solar cells, or green chemistry . This review will focus on InP QD synthesis, surface chemistry, and inherent fluorescent properties.…”

“…31 Since the discovery that ZnSe can grow a thick intermediary shell because of its reduced lattice mismatch with InP, the field has seen significant improvements in the photophysical properties of InP-based QDs with photoluminescent quantum yields (PLQYs) greater than 95%, emission line widths (fwhm) down to 35 nm, and QLEDS with external quantum efficiencies >20%. 14,32−35 There are a number of recent reviews that have focused either more broadly on multiple semiconductor QD materials 30,36−39 or more exclusively on InP QD's use in a specific application such as QLEDs, 40,41 displays, 42 solar cells, 43 or green chemistry. 44 This review will focus on InP QD synthesis, surface chemistry, and inherent fluorescent properties.…”

Quantum-Dot Light-Emitting Diodes Exhibiting Narrow-Spectrum Green Electroluminescence by Using Ag–In–Ga–S/GaSx Quantum Dots

“…The organic ligands attached to surface of QDs prevent the aggregation of particles and enable QDs to disperse in a solvent. Applications of the electroluminescence (EL) of QDs have also been studied. − QD light-emitting diodes (QD-LEDs) are fabricated using a QD film as an emitting layer (EML). When a dc voltage is applied to electrodes, electrons and holes are injected into EML and emit light from QDs.…”

Control of the Reaction Kinetics of Monodispersed InP/ZnSeS/ZnS-Based Quantum Dots Using Organophosphorus Compounds for Electroluminescent Devices

“…The development of high-quantum yield (QY) light-emitting materials with better color purity and tunability to visualize colors more distinctly in displays have emerged as an important field of research. − Among different colloidal quantum dots (QDs), Cd-based QDs have shown better results, but the biotoxicity of Cd, which adversely affects human health and the environment, has severely limited their commercial applications. , Researchers are focusing on developing nontoxic and environmentally friendly QD materials. , InP-based QDs are considered ideal light-emitting materials, as their emissions cover nearly the full range of natural colors. − InP-based QDs are typically synthesized from two major phosphorus sources, tris­(dimethylamino)­phosphine [(DMA) 3 P] and tris­(trimethylsilyl)­phosphine [(TMS) 3 P]. , (TMS) 3 P shows a better QY and a homogeneous size distribution compared to those of (DMA) 3 P. However, this phosphorus source is expensive and hazardous, which limits its widespread application . In contrast, (DMA) 3 P is considerably inexpensive and safe to use.…”

“…1−5 Among different colloidal quantum dots (QDs), Cd-based QDs have shown better results, but the biotoxicity of Cd, which adversely affects human health and the environment, has severely limited their commercial applications. 6,7 Researchers are focusing on developing nontoxic and environmentally friendly QD materials. 8,9 InP-based QDs are considered ideal light-emitting materials, as their emissions cover nearly the full range of natural colors.…”