https://scholar.dgist.ac.kr/handle/20.500.11750/231 Sat, 03 Oct 2026 21:40:01 GMT 2026-10-03T21:40:01Z https://scholar.dgist.ac.kr/handle/20.500.11750/60863 Title: High-efficiency and long-lifetime solution-processed red PHOLEDs using n-type host materials and an Ir(III) complex Author(s): Park, Ho-Yeol; Hwang, Youngjun; Jung, Hyeonwoo; Song, Donghyeng; Kim, Hyerin; Kumaresan, Raja; Lee, Youngu; Jin, Sung-Ho Abstract: High-performance solution-processed red phosphorescent organic light-emitting diodes (PHOLEDs) are required to reduce energy consumption and fabrication costs. However, solution-processed red PHOLEDs have low performance and short operating lifetimes. We designed and synthesized a red phosphor and two n-type hosts to achieve highly efficient solution-processed red PHOLEDs. The developed red phosphor, Red12 has high thermal stability and a photoluminescence quantum yield of exceeding 95%. Naphthalene-based n-type host materials, namely 2-(4-(naphthalen-1-yl)phenyl)-4,6-diphenyl-1,3,5-triazine (DPTPN) and 2-(4-(2-methylnaphthalen-1-yl) phenyl)-4,6-diphenyl-1,3,5-triazine (DPTPMN) have a suitable LUMO energy level, high charge carrier mobility, and excellent thermal stability. In particular, the matched LUMO levels between DPTPN and the red dopant minimized charge trapping and exciton quenching, leading to improved device efficiency and operational stability. The optimized red PHOLEDs based on DPTPN or DPTPMN exhibited maximum external quantum efficiencies of 29.5 and 28.9%, current efficiencies of 43.1 and 42.5 cd/A, and power efficiencies of 33.8 and 33.4 lm/W, respectively. Furthermore, a device with a TCTA:DPTPN:Red12 emitting layer had a 50-fold greater lifetime than TCTA:TPBi:Red12. Sun, 31 May 2026 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60863 2026-05-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58943 Title: Boosting Efficiency and Longevity of Quantum Dot Light-Emitting Diodes with Dibenzofuran-Incorporated Hole Transport Materials Featuring High Bond Dissociation Energy Author(s): Hwang, Youngjun; Jung, Hyeonwoo; Kim, Jongyoun; Lee, Dongwoo; Lee, Youngu Abstract: The intrinsic degradation of quantum dot light-emitting diodes (QLEDs) is often attributed to the insufficient stability of hole transport materials (HTMs), which adversely affects both efficiency and operational lifetime. Despite efforts to address this issue, HTMs with high bond dissociation energy (BDE) for enhanced QLED performance remain underdeveloped. Here, a series of dibenzofuran (DBF)-incorporated HTMs with high BDE is synthesized to improve QLED efficiency and longevity. Among them, poly(9,9-dioctylfluorene-co-N,N-diphenyldibenzo[b,d]furan-1-amine) (1-PFDBF) exhibits superior hole mobility, high BDE, extended exciton lifetime, and reduced trap density. Green QLEDs employing 1-PFDBF achieve a maximum external quantum efficiency (EQEmax) of 25.71%, a maximum current efficiency of 102.98 cd A(-)(1), and a maximum power efficiency of 75.69 lmW(-)(1), significantly outperforming poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)diphenylamine) (TFB)-based QLEDs. Notably, the EQEmax of 1-PFDBF-based green QLEDs ranks among the highest for devices utilizing triarylamine-based HTMs. Furthermore, the operational half-lifetime of the 1-PFDBF-based QLEDs is approximate to 15 900 h at 1 000 cd m(-)2 and approximate to 1 460 000 h at 100 cd m(-)2, making a significant increase of 3 600% and 6 600%, respectively, compared to TFB-based QLEDs. These findings establish DBF incorporation as an effective strategy for enhancing HTM BDE and hole mobility, optimizing charge balance within QLEDs, and ultimately enabling high-efficiency and long-lasting QLEDs. Sun, 31 Aug 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58943 2025-08-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58944 Title: Anisotropic Dynamic Disorder of π-Stacking and Static Disorder in Organic Electron Transporting Materials with Isomorphic Crystal Structures Author(s): Lee, Chae-Won; Puc, Uros; Lee, Jeong Hyeon; Cho, Na Young; Lee, Jong Bum; Lee, Yun-Sang; Kim, Jin Chul; Yoon, Woojin; Yun, Hoseop; Jang, Seokhoon; Lee, Youngu; Kim, Jong H.; Kwak, Sang Kyu; Jazbinsek, Mojca; Kwon, O-Pil Abstract: In organic semiconductors, charge transport is strongly correlated with intermolecular π–π interactions and the dynamic disorder caused by solid-state phonon vibrations. However, for pure π–π stacking of semiconducting cores, solid-state phonon vibrations and their directional characteristics are relatively unexplored. In this work, solid-state phonon vibrations using experimental and theoretical phonon-resolved analyses of single crystals are studied, for which a series of organic electron-transporting naphthalene diimide (NDI) analogs as a model system is designed. The three NDI analogs in this series exhibit isomorphic crystal structures with a brickwork-type assembly characterized by pure face-to-face π–π stacking, but different π–π stacking distances. The as-grown NDI single crystals exhibit strong anisotropic phonon vibrations, with substantial differences observed between the directions parallel and perpendicular to the π–π stacking, appearing in two distinct THz frequency ranges (below and above 7 THz). These vibrations originate from the out-of-plane and in-plane movements of the NDI cores, respectively. For vacuum-deposited polycrystalline films, despite having isomorphic crystal structures with equivalent dominant (001) facets, the static disorder, which is influenced by crystalline perfection and trap density, varied markedly among the three NDI analogs. Sun, 31 Aug 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58944 2025-08-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58317 Title: Electronic Nose Based on a Multi-Thin Film Transistor Sensor Array Structure for Detecting Odorants with High Selectivity Author(s): Kim, Sohee; Pyo, Goeun; Choi, Wonhyuk; Jang, Hyun Woo; Kwon, Hyeokjin; Kim, Kwangsu; Heo, Su Jin; Kim, Dong Su; Kim, Jongyoun; Lee, Youngu; Kang, Hongki; Kwon, Hyuk-Jun; Moon, Cheil; Jang, Jae Eun; Kim, Sohee Abstract: Electrical noses that mimic the human olfactory system have been developed to detect odors or flavors. Unfortunately, little research on sensing reactions to various odors like a human nose can be found in the literature. Herein, an electronic nose is proposed using a multi-thin film transistor (TFT) sensor array with various polymer selectors and multi-output signal processing to detect various odorants with high selectivity. Through the combination of multi-output produced by eight polymer variables based on indium gallium zinc oxide (IGZO) TFTs, a specific radar pattern and its selectivity are generated for the eight different odor substances. Eight multi-output signal processing reduced the correlation coefficient of similarity from 77.9% to 45% relative to the case of four multi-output processing. Because the polymers have different functional groups, polymers showed specific reactions to various odorants, like the human's system, and multi-output analysis could distinguish various odors, even if polymers did not show single selectivity to a specific odor. And the sensitivity improved when compared to two-terminal structures by using TFTs based on IGZO. The advantage is that it can classify multiple odors with good selectivity and sensitivity. This sensor and signal processing concept can be applied to E-nose systems capable of odor monitoring. © 2025 Wiley-VCH GmbH. Sun, 31 Aug 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58317 2025-08-31T15:00:00Z