Jeonghun Kwak

We report highly bright and efficient inverted structure quantum dot (QD) based light-emitting diodes (QLEDs) by using solution-processed ZnO nanoparticles as the electron injection/transport layer and by optimizing energy levels with the organic hole transport layer. We have successfully demonstrated highly bright red, green, and blue QLEDs showing maximum luminances up to 23,040, 218,800, and 2250 cd/m(2), and external quantum efficiencies of 7.3, 5.8, and 1.7%, respectively. It is also notice

Abstract Quantum dot light‐emitting diodes (QLEDs) are one of the most promising candidates for next‐generation displays and lighting sources, but they are barely used because vulnerability to electrical and thermal stresses precludes high brightness, efficiency, and stability at high current density ( J ) regimes. Here, bright and stable QLEDs on a Si substrate are demonstrated, expanding their potential application boundary over the present art. First, a tailored interface is granted to the qu

Transition metal based layered double hydroxides are important energy storage materials. The overall performances of the electrodes are dependent on conductivity, crystallinity, morphology, and surface area.

The remarkable progress of virtual reality, augmented reality, quantum dot light-emitting diode, and organic light-emitting diode as next-generation displays has overcome the leadership of the liquid crystal display during the last two years. This paper discusses the key technological advancements and performance of these new-generation display devices.

Abstract Conventional stretchable electronics that adopt a wavy design, a neutral mechanical plane, and conformal contact between abiotic and biotic interfaces have exhibited diverse skin‐interfaced applications. Despite such remarkable progress, the evolution of intelligent skin prosthetics is challenged by the absence of the monolithic integration of neuromorphic constituents into individual sensing and actuating components. Herein, a bioinspired stretchable sensory‐neuromorphic system, compri

Thin-film ultraviolet (UV) light-emitting diodes (LEDs) with emission wavelengths below 400 nm are emerging as promising light sources for various purposes, from our daily lives to industrial applications. However, current thin-film UV-emitting devices radiate not only UV light but also visible light. Here, we introduce genuine UV-emitting colloidal nanocrystal quantum dot (NQD) LEDs (QLEDs) using precisely controlled NQDs consisting of a 2.5-nm-sized CdZnS ternary core and a ZnS shell. The effe

Quantum dot/conducting polymer hybrid films are used to prepare light-emitting diodes (LEDs). The hybrid films (CdSe@ZnS quantum dots excellently dispersed in a conducting polymer matrix, see figure) are readily prepared by various solution-based processes and are also easily micropatterned. The LEDs exhibit a turn-on voltage of 4 V, an external quantum efficiency greater than 1.5%, and almost pure-green quantum-dot electroluminescence.

Abstract InP quantum dots (QDs) based light‐emitting diodes (QLEDs) are considered as one of the most promising candidates as a substitute for the environmentally toxic Cd‐based QLEDs for future displays. However, the device architecture of InP QLEDs is almost the same as the Cd‐based QLEDs even though the properties of Cd‐based and InP‐based QDs are quite different in their energy levels and shapes. Thus, it is highly required to develop a proper device structure for InP‐based QLEDs to improve

Abstract Inkjet printing of colloidal quantum dots (QDs) is considered a promising technology for application in full‐color quantum dot light‐emitting diode (QLED) displays. However, QLEDs that are inkjet printed in a pixel‐defining bank structure generally exhibit a low performance, mainly due to the nonuniformity in its QD morphology. In this study, an enhanced performance of inkjet‐printing‐based pixelated QLEDs is achieved by introducing small amounts of poly(methyl methacrylate) (PMMA) of d

In 2019, the device performances of the display technologies were largely advanced by the development of new materials and of the device architecture and driving scheme. The recent progress in the areas of virtual reality (VR), augmented reality (AR), quantum dot light-emitting diode (QLED), and organic light-emitting diode (OLED) is comprehensively summarized and discussed in this paper.

We demonstrated highly efficient inverted bottom-emission organic light-emitting diodes (IBOLEDs) using tin dioxide (SnO2) nanoparticles (NPs) as an electron injection layer at the interface between the indium tin oxide (ITO) cathode and the organic electron transport layer. The SnO2 NP layer can facilitate the electron injection since the conduction band energy level of SnO2 NPs (-3.6 eV) is located between the work function of ITO (4.8 eV) and the lowest unoccupied molecular orbital (LUMO) ene

Virtual reality, augmented reality, quantum dot light-emitting diodes, and organic light-emitting diodes have progressed over the last two years. Key achievements in these displays are discussed in terms of device performance.

A semicrystalline p-type thermoelectric conjugated polymer based on a polymer backbone of cyclopentadithiophene and benzothiadiazole, poly[(4,4′-(bis(hexyldecylsulfanyl)methylene)cyclopenta[2,1-b:3,4-b′]dithiophene)-alt-(benzo[c][1,2,5]thiadiazole)] (PCPDTSBT), is designed and synthesized by replacing normal alkyl side-chains with bis(alkylsulfanyl)methylene substituents. The sp2-hybridized olefinic bis(alkylsulfanyl)methylene side-chains and the sulfur–sulfur (S–S) chalcogen interactions extend