Byung Soon Kim

Bio: Byung Soon Kim is an academic researcher from Kyung Hee University. The author has contributed to research in topics: Materials science & Thin-film transistor. The author has an hindex of 7, co-authored 9 publications receiving 219 citations.

High-Efficiency, Blue, Green, and Near-Infrared Light-Emitting Diodes Based on Triple Cation Perovskite

Abstract: Quick View Other Sources By Kim, Hyeong Pil; Kim, Jeongmo; Kim, Byung Soon; Kim, Hyo-Min; Kim, Jeonggi; bin Mohd. Yusoff, Abd. Rashid; Jang, Jin; Nazeeruddin, Mohammad Khaja From Advanced Optical Materials (2017), Ahead of Print.

Efficient colloidal quantum dot light-emitting diodes operating in the second near-infrared biological window

Abstract: Semiconductor colloidal quantum dots (CQDs) offer size- and composition-tunable luminescence of high colour purity. Importantly, their emission can be tuned deep into the second biological near-infrared (NIR-II) window (1,000–1,700 nm). However, applications are hindered by the low efficiencies achieved to date. Here, we report NIR-II CQD light-emitting diodes with an external quantum efficiency of 16.98% and a power conversion efficiency of 11.28% at wavelength 1,397 nm. This performance arises from device engineering that delivers a high photoluminescence quantum yield and charge balance close to unity. More specifically, we employed a binary emissive layer consisting of silica-encapsulated silver sulfide (Ag2S@SiO2) CQDs dispersed in a caesium-containing triple cation perovskite matrix that serves as an additional passivation medium and a carrier supplier to the emitting CQDs. The hole-injection contact also features a thin porphyrin interlayer to balance the device current and enhance carrier radiative recombination. Semiconductor nanocrystals with efficient tunable emission in the 1,000–1,700 nm window could prove useful for applications in deep biological imaging and sensing.

High-Performance Flexible TFT Circuits Using TIPS Pentacene and Polymer Blend on Plastic

Abstract: We report the high-performance circuit on 25-μm polyimide substrate with organic thin-film transistors (TFTs) (OTFTs) using 6,13-bis(triisopropyl-silylethynyl) pentacene and polymer blending. Because of high mobility (0.64 cm2/V·s) and low threshold voltage (<;|1 V|) of the TFTs, an 11-stage ring oscillator (RO) made of these TFTs exhibits the switching speed of 31.4 kHz at the supply voltage of 20 V. The output waveforms of the RO change little after 5000 times bending with a radius of curvature of 2 mm, and thus, the OTFT circuits can be applied to very flexible electronics.

67.1: Distinguished Student Paper: 40 um‐pitch IGZO TFT Gate Driver for High‐resolution Rollable AMOLED

Abstract: We report the design and fabrication of an amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT)-based high-speed and ultra-narrow shift register on a plastic substrate. The shift register consisting 5 TFTs and 1 capacitor is small in physical size which is only 40 μm in width (pitch). At the supply voltage (VDD) of 15 V, the clock frequency of the shift register approaches 166.7 kHz, corresponding to a pulse width of 3 μs. The shift register could be operated under mechanical bending radius of 2mm, making it applicable to flexible high resolution active-matrix displays.

20.1: Invited Paper : Robust TFT Backplane for Flexible AMOLED

Abstract: We report the fabrication and flexibility of the TFTs based on poly-Si and a-IGZO on polyimide (PI). The performances of the TFTs do not degrade upon 10,000 times rolling with 2 mm radius for a-IGZO and 4 mm for poly-Si TFTs. It is found that there is no electrostatic damage for the TFT backplane on PI with a conducting backbone.

Metal halide perovskites for light-emitting diodes.

Abstract: 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. The development of perovskite emitters, their use in light-emitting devices, and the challenges in enhancing the efficiency and stability, as well as reducing the potential toxicity of this technology are discussed in this Review.

Perovskites for Next-Generation Optical Sources.

Abstract: Next-generation displays and lighting technologies require efficient optical sources that combine brightness, color purity, stability, substrate flexibility. Metal halide perovskites have potential use in a wide range of applications, for they possess excellent charge transport, bandgap tunability and, in the most promising recent optical source materials, intense and efficient luminescence. This review links metal halide perovskites' performance as efficient light emitters with their underlying materials electronic and photophysical attributes.

Room-Temperature Triple-Ligand Surface Engineering Synergistically Boosts Ink Stability, Recombination Dynamics, and Charge Injection toward EQE-11.6% Perovskite QLEDs

Abstract: Developing low-cost and high-quality quantum dots (QDs) or nanocrystals (NCs) and their corresponding efficient light-emitting diodes (LEDs) is crucial for the next-generation ultra-high-definition flexible displays. Here, there is a report on a room-temperature triple-ligand surface engineering strategy to play the synergistic role of short ligands of tetraoctylammonium bromide (TOAB), didodecyldimethylammonium bromide (DDAB), and octanoic acid (OTAc) toward "ideal" perovskite QDs with a high photoluminescence quantum yield (PLQY) of >90%, unity radiative decay in its intrinsic channel, stable ink characteristics, and effective charge injection and transportation in QD films, resulting in the highly efficient QD-based LEDs (QLEDs). Furthermore, the QD films with less nonradiative recombination centers exhibit improved PL properties with a PLQY of 61% through dopant engineering in A-site. The robustness of such properties is demonstrated by the fabrication of green electroluminescent LEDs based on CsPbBr3 QDs with the peak external quantum efficiency (EQE) of 11.6%, and the corresponding peak internal quantum efficiency (IQE) and power efficiency are 52.2% and 44.65 lm W-1 , respectively, which are the most-efficient perovskite QLEDs with colloidal CsPbBr3 QDs as emitters up to now. These results demonstrate that the as-obtained QD inks have a wide range application in future high-definition QD displays and high-quality lightings.

Modulation of recombination zone position for quasi-two-dimensional blue perovskite light-emitting diodes with efficiency exceeding 5

Abstract: In recent years, substantial progress has been made in developing perovskite light-emitting diodes with near-infrared, red and green emissions and over 20% external quantum efficiency. However, the development of perovskite light-emitting diodes with blue emission remains a great challenge, which retards further development of full-color displays and white-light illumination based on perovskite emissive materials. Here, firstly, through composition and dimensional engineering, we prepare quasi-two-dimensional perovskite thin films with improved blue emission, taking advantages of reduced trap density and enhanced photoluminescence quantum yield. Secondly, we find a vertically non-uniform distribution of perovskite crystals in the PEDOT:PSS/perovskite hybrid film. Through modulating the position of the recombination zone, we activate the majority of quasi-two-dimensional perovskite crystals, and thus demonstrate the most efficient blue perovskite light-emitting diode to date with emission peak at 480 nm, record luminance of 3780 cd m−2 and record external quantum efficiency of 5.7%. Halide perovskite based light-emitting diodes attracted intensive research interest recently but the efficiency of blue diodes is much lower than the green and red ones. Here Li et al. push up the efficiency of blue diodes through composition engineering and vertical morphology control.

Perovskites for Light Emission.

Abstract: Next-generation displays require efficient light sources that combine high brightness, color purity, stability, compatibility with flexible substrates, and transparency. Metal halide perovskites are a promising platform for these applications, especially in light of their excellent charge transport and bandgap tunability. Low-dimensional perovskites, which possess perovskite domains spatially confined at the nanoscale, have further extended the degree of tunability and functionality of this materials platform. Herein, the advances in perovskite materials for light-emission applications are reviewed. Connections among materials properties, photophysical and electrooptic spectroscopic properties, and device performance are established. It is discussed how incompletely solved problems in these materials can be tackled, including the need for increased stability, efficient blue emission, and efficient infrared emission. In conclusion, an outlook on the technologies that can be realized using this material platform is presented.