Bifunctional Metal Oleate as an Alternative Method to Remove Surface Oxide and Passivate Surface Defects of Aminophosphine-Based InP Quantum Dots

Suppression of Interfacial Oxidation in Core/Shell InP Quantum Dots through Solvent Assisted Core-Etching Strategy for Efficient Green Light-Emitting Diodes

Indium phosphide (InP) quantum dots (QDs) are promising alternative heavy-metal CdSe QDs for light-emitting diode (LED) application. However, their highly reactive core surface is prone to oxidation, which reduces the photoluminescence quantum yield (PL QY) and impedes subsequent shell growth. Traditional etching methods using HF aqueous solution are problematic as water can induce reoxidation during or after etching. Herein, we present HF pyridine solution as a more effective etching reagent to enhance luminous properties of InP QDs. Pyridine molecules replace the bulky carboxyl ligand, reducing steric hindrance and allowing HF easier access to the core for removing surface oxides. This ligand exchange promotes rapid shell growth, minimizing core exposure to the reaction environment and thereby reoxidation risk. Consequently, the as-prepared core/shell QDs exhibit a high PL QY of ∼90%, and the corresponding LEDs achieve an external quantum efficiency of 15.4% along with a long operational lifetime of 6819 h, outperforming the control devices.

High-Performance Giant InP Quantum Dots with Stress-Released Morphological ZnSe-ZnSeS-ZnS Shell

Indium phosphide (InP) quantum dots (QDs) are increasingly considered potent alternatives to traditional cadmium-based QDs. Notwithstanding, the material stability of InP, especially when juxtaposed with its cadmium-based counterparts, poses significant challenges in its application. Generally, a thick ZnS shell is applied to InP cores to thwart photo-oxidation and diminish nonradiative recombination. Yet, the pronounced lattice mismatch between the InP core and the ZnS shell can introduce lattice defects, consequently attenuating the luminescence efficiency. This makes the cultivation of a flawless thick shell a paramount challenge. In the present research, a synthetic methodology is elucidated to fabricate highly efficient InP QDs with dimensions exceeding 20 nm, achieved by alleviating the lattice mismatch strain during the shell growth. By regulating the shell composition and morphology, InP/ZnSe/ZnSeS/ZnS QDs with shield-like morphology are prepared and demonstrate a photoluminescence quantum yield (PLQY) of ≈90%, exhibiting significantly enhanced photostability and thermal stability. This discovery is expected to greatly advance the preparation of highly efficient InP-based or other QDs, expanding their potential in various applications such as environmentally friendly displays and energy-saving lighting.

Repercussions of the Inner Shell Layer on the Performance of Cd-Free Quantum Dots and Their Light-Emitting Diodes

Indium phosphide (InP) and zinc selenium tellurium (ZnSeTe) quantum dots (QDs) as less toxic alternatives have received substantial attention. The structure of QDs generally consists of a QD core, inner shell layer, and outer shell layer. We reckon that the inner shell layer, especially its components and thickness, have a significant influence on the optical and electronic performances of QDs. In this Perspective, we compare optical properties of these QDs with different inner shells and summarize how typical inner shell components and thickness influence their optical properties. The impact of the inner shell on the performance of QD light-emitting diodes (QLEDs) has also been discussed. The appropriate components and thickness of the inner shell both contribute to alleviate valence or lattice mismatch, thereby enhancing the performance of QDs. We expect that this Perspective could heighten awareness of the significance and impact of the inner shell layer in QDs and facilitate further development of QDs and QLEDs.

Recent Applications of Quantum Dots in Pharmaceutical Analysis

Nanotechnology has emerged as one of the most potential areas for pharmaceutical analysis. The need for nanomaterials in pharmaceutical analysis is comprehended in terms of economic challenges, health and safety concerns. Quantum dots (QDs)or colloidal semiconductor nanocrystals are new groups of fluorescent nanoparticles that bind nanotechnology to drug analysis. Because of their special physicochemical characteristics and small size, QDs are thought to be promising candidates for the electrical and luminescent probes development. They were originally developed as luminescent biological labels, but are now discovering new analytical chemistry applications, where their photo-luminescent properties are used in pharmaceutical, clinical analysis, food quality control and environmental monitoring. In this review, we discuss QDs regarding properties and advantages, advances in methods of synthesis and their recent applications in drug analysis in the recent last years.

Enhanced Photostability of Core/Shell Quantum Dots under Intense Blue Light Irradiation through Positive Photoaging Mechanism

Photostability of semiconductor core/shell quantum dots (QDs) has historically been perceived as intricate and unpredictable. Notably, the long-term luminescence stability of QDs under light exposure does not seem to consistently correspond with their characteristics in the absence of light. In this study, we propose a positive photoaging mechanism of QDs, integrating both ligand/shell-induced photobrightening and surface photo-oxidation, to deal with the photostability nuances. When QDs are subjected to higher energy light, their photobrightening and photodarkening conjointly determine the photostability. Enhanced photostability may not be simply attributed to a thicker shell or the presence of ligands. When adjusted with an optimal shell thickness and supplemented with negatively charged ligands, QDs exhibit enhanced photostability in both solvents and polymers.

Top-Emitting Active-Matrix Quantum Dot Light-Emitting Diode Array with Optical Microcavity for Micro QLED Display

An electroluminescent quantum-dot light-emitting diode (QLED) device and a micro QLED device array with a top-emitting structure were demonstrated in this study. The QLED device was fabricated in the normal structure of [ITO/Ag/ITO anode]/PEDOT:PSS/PVK/QDs/[ZnO nanoparticles]/Ag/MoO₃, in which the semi-transparent MoO₃-capped Ag cathode and the reflective ITO/metal/ITO (IMI) anode were designed to form an optical microcavity. Compared with conventional bottom-emitting QLED, the microcavity-based top-emitting QLED possessed enhanced optical properties, e.g., ~500% luminance, ~300% current efficiency, and a narrower bandwidth. A 1.49 inch micro QLED panel with 86,400 top-emitting QLED devices in two different sizes (17 × 78 μm² and 74 × 40.5 μm²) on a low-temperature polysilicon (LTPS) backplane was also fabricated, demonstrating the top-emitting QLED with microcavity as a promising structure in future micro display applications.

ZnF2-Assisted Synthesis of Highly Luminescent InP/ZnSe/ZnS Quantum Dots for Efficient and Stable Electroluminescence

High-quality InP-based quantum dots (QDs) have become very promising, environmentally benign light emitters for display applications, but their synthesis generally entails hazardous hydrofluoric acid. Here, we present a highly facile route to InP/ZnSe/ZnS core/shell/shell QDs with a near-unity photoluminescence quantum yield. As the key additive, the inorganic salt ZnF₂ mildly reacts with carboxylic acid at a high temperature and in situ generates HF, which eliminates surface oxide impurities, thus facilitating epitaxial shell growth. The resulting InP/ZnSe/ZnS QDs exhibit a narrower emission line width and better thermal stability in comparison with QDs synthesized with hydrofluoric acid. Light-emitting diodes using large-sized InP/ZnSe/ZnS QDs without replacing original ligands achieve the highest peak external quantum efficiency of 22.2%, to the best of our knowledge, along with a maximum brightness of >110 000 cd/m² and a T₉₅ lifetime of >32 000 h at 100 cd/m². This safe approach is anticipated to be applied for a wide range of III-V QDs.