Article
Chemistry, Multidisciplinary
Xiaoqi Tian, Kazutaka Shoyama, Bernhard Mahlmeister, Felix Brust, Matthias Stolte, Frank Wuerthner
Summary: Two heliceno-bis(naphthalimides) compounds with electron-accepting naphthalimide moieties attached at both ends of helicene core were synthesized by an effective two-step strategy. Their enantiomers were successfully resolved using chiral stationary-phase high-performance liquid chromatography (HPLC). The helical structure and absolute configuration of the compounds were confirmed through single-crystal X-ray diffraction analysis and experimental and calculated circular dichroism (CD) spectra. Both compounds exhibited high molar extinction coefficients and fluorescence quantum yields, and compound 2 demonstrated potential for applications in chiral optoelectronics due to its red circularly polarized luminescence emission and high brightness.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Multidisciplinary
Alexander C. Brannan, Hwan-Hee Cho, Antti-Pekka M. Reponen, Mikko Linnolahti, Manfred Bochmann, Neil C. Greenham, Alexander S. Romanov
Summary: A series of carbene-gold-acetylide complexes have been synthesized and found to exhibit deep-blue to blue-green phosphorescence in various media. The increase of carbene-gold moieties in these complexes leads to higher extinction coefficients and stronger oscillator strength coefficients in the UV-vis spectra.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Weili Li, Aoyun Wu, Tiliang Fu, Xin Gao, Ying Wang, Dandan Xu, Cong Zhang, Zhengyi Sun, Yannan Lu, David James Young, Hongbo Li, Xiao-Chun Hang
Summary: The secondary kinetic isotope effects (KIEs) on red phosphorescent Ir(III) complexes and their corresponding devices were investigated. Selectively deuterated red emitters showed minimal influence on luminescent spectra, but had positive effects on quantum efficiencies and device stabilities. The findings highlight the importance of isotopic effects in improving the performance of organic light emitting devices and suggest future exploration of isotopic tools in organic optoelectronic materials.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Multidisciplinary Sciences
Lei Hua, Yuchao Liu, Binbin Liu, Zhennan Zhao, Lei Zhang, Shouke Yan, Zhongjie Ren
Summary: By designing emitters with different TADF units on a TNP core, concentration quenching of TADF units is reduced in the stacking structure of TNPs, resulting in high-efficiency orange-red emission and increased photoluminescence quantum yield. This study provides a universal strategy for designing high-performance TADF emitters.
NATURE COMMUNICATIONS
(2022)
Review
Chemistry, Inorganic & Nuclear
Pavel S. Chelushkin, Julia R. Shakirova, Ilya S. Kritchenkov, Vadim A. Baigildin, Sergey P. Tunik
Summary: The application of NIR emitting transition metal complexes in biomedicine has expanded to include oxygen sensing, visualization of biological models, and various therapeutic applications. Challenges remain in improving the photophysical and physico-chemical characteristics of these compounds for further advancements in biomedical applications.
DALTON TRANSACTIONS
(2022)
Review
Chemistry, Inorganic & Nuclear
Maria L. Buil, Miguel A. Esteruelas, Ana M. Lopez
Summary: The application of new procedures in organometallic synthesis using alternative starting complexes has significantly enhanced the preparation of osmium(IV), osmium(II), and iridium(III) emitters since 2012. The choice of precursors should consider the ligands, as they play a role in emitter synthesis. Three different functions of ligands in the revised procedures have been identified, including directing selectivity in sigma-bond ruptures, participating in new coordinated groups, and acting as internal bases in activation reactions. Additionally, the ability of polyhydrides OsH6((PPr3)-Pr-i)(2) and IrH5((PPr3)-Pr-i)(2) to activate C-H bonds is highlighted as a key factor in the success of many cases.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2021)
Article
Engineering, Electrical & Electronic
D. Tselekidou, K. Papadopoulos, A. Zachariadis, V. Kyriazopoulos, S. Kassavetis, A. Laskarakis, M. Gioti
Summary: In this study, Bis(2-(3,5-dimethylphenyl)quinoline-C,N)(acetylacetonato)iridium(III), (Ir(dmpq)2(acac)) was doped into four small molecule host materials and used as the active layer in OLED devices. All tested devices emitted red light with a maximum wavelength of approximately 620 nm, providing insights into the selection of the best host materials for PhOLEDs.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Review
Chemistry, Inorganic & Nuclear
Jayaraman Jayabharathi, Venugopal Thanikachalam, Shanmugam Thilagavathy
Summary: This review presents a low-cost fabrication process for efficient phosphorescent organic light-emitting diodes (PhOLEDs) based on Ir(III) complexes. The excellent charge transportation and injection abilities of Ir (III) complexes contribute to their usage as both charge transport materials and emissive materials in PhOLEDs. The reduced intermolecular aggregation and excellent hole and electron transporting abilities of Ir(III) complexes lead to highly efficient PhOLEDs. In doped PhOLEDs, the efficiency is determined by exciton confinement, charge trapping, and dopant concentration.
COORDINATION CHEMISTRY REVIEWS
(2023)
Article
Chemistry, Inorganic & Nuclear
Johannes Soellner, Thomas Strassner
Summary: Iridium(III) complexes with cyclometalating ligands have excellent properties for use as phosphorescent emitters in organic light emitting diodes. A series of complexes with 2-phenyl-pyridine and bis(pyrazolyl)borate ligands showed nearly unitary quantum yields and short excited state lifetimes in sky-blue to green emissions.
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
(2021)
Article
Chemistry, Inorganic & Nuclear
Guijie Li, Jianfeng Wen, Feng Zhan, Weiwei Lou, Yun-Fang Yang, Ying Hu, Yuanbin She
Summary: Pt(II) complexes are promising materials for OLED applications in various fields. A series of novel Pt(II) emitters based on biphenyl (bp) were designed and their properties were studied. Ligand modification and linking group control could effectively regulate their properties, while the emission spectra remained constant. The emitters exhibited vibronically featured spectra and achieved high photoluminescent quantum yields. Green OLED using Pt(bp-12) achieved a maximum brightness of 16,644 cd/m(2).
INORGANIC CHEMISTRY
(2022)
Article
Engineering, Electrical & Electronic
Jing Wang, Menglan Xie, Huiqing Pang, Cuifang Zhang, Ming Sang, Qi Zhang, Wei Cai, Raymond Kwong, Sean Xia
Summary: This work investigates the potential of phosphorescent emitters to achieve the BT.2020 color standard in displays. New deep green and deep red phosphorescent emitters were designed and synthesized, and OLEDs built with these emitters achieved high performance and satisfied the BT.2020 color gamut.
JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY
(2023)
Article
Chemistry, Physical
Sadiara Fall, Nicolas Zimmerman, Denis Tondelier, Bernard Geffroy, Nicolas Leclerc, Thomas Heiser, Christophe Lebreton, Emmanuel Jacques, Cassandre Quinton, Fabien Lucas, Cyril Poriel, Clement Brouillac, Joelle Rault-Berthelot
Summary: In this study, a green-emitting SL-PhOLED with a high external quantum efficiency is reported, achieved through a rational molecular design of the EML. The EML displays all the required characteristics for efficient charge injection, transport, and recombination. The new phosphorescent emitter, Ir(ppy)(2)acac, shows high potential and significantly impacts the ambipolarity of charge transport.
CHEMISTRY OF MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Maho Kitahara, Seika Suzuki, Kana Matsudaira, Shigeyuki Yagi, Michiya Fujiki, Yoshitane Imai
Summary: The study demonstrates the development of phosphorescent organometallic molecules that exhibit full-color circularly polarised luminescence without chiral chemical influences, presenting a significant scientific and engineering challenge. Four optically inactive Iridium(III) complexes were shown to produce red-green-blue-yellow (RGBY) colored magnetic circularly polarised luminescence (MCPL) in organic solvents, with almost identical anisotropy factors in the presence of a magnetic field but exhibiting inverted signs when using the same Faraday geometries.
Article
Chemistry, Multidisciplinary
Yang Liu, Xin Xiao, You Ran, Zhengyang Bin, Jingsong You
Summary: By attaching a cyano functionality at the lowest unoccupied molecular orbital location of the MR-TADF skeleton, the red-shifted emission and good color purity of orange-red MR-TADF emitters can be achieved. The coplanar conformation of the CN group helps to restrict structure relaxation and maintain the high-quality emission characteristics in orange-red TADF-OLEDs.
Article
Chemistry, Inorganic & Nuclear
Yongjun Song, Renyou Yu, Mengzhen Chen, Lei He
Summary: This study reports the development of fluorine-free cyan to deep blue emissive cationic Ir(III) complexes with phenylimidazole-type cyclometalated ligands, showing good emission properties in both solution and diluted films, as well as promising applications in OLEDs and solid-state LEECs.
INORGANIC CHEMISTRY
(2021)
Article
Physics, Applied
Ik-Su Byun, Danil W. Boukhvalov, Sangik Lee, Wondong Kim, Jaeyoon Baik, Hyun-Joon Shin, Changhee Lee, Young-Woo Son, Quanxi Jia, Bae Ho Park
Summary: Room-temperature ferromagnetism was observed in nanoscale functionalized graphene using atomic force microscope lithography, demonstrating potential for high-density graphene-based spintronic devices. Magnetic force microscope measurements confirmed the presence of local ferromagnetic signals in selectively functionalized graphene, indicating its suitability as a spin injector or detector in such devices.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Physics, Applied
Jaehoon Kim, Yeonkyung Lee, Jun Young Kim, Hyung-Jun Song, Jiyun Song, Hyunho Lee, Changhee Lee
Summary: Research has shown that organic solar cells (OSCs) with Al-doped ZnO (AZO) as an electron transport layer exhibit improved thermal stability, maintaining high efficiency at high temperatures. By analyzing oxygen defects and the space-charge limited current region, the mechanism underlying the enhanced stability of OSCs with AZO was identified.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Physical
Jung-Hwa Park, Jaehoon Kim, Jin Hong Kim, Dong Won Kim, Chi Hyun Ryoo, Oh Kyu Kwon, Changhee Lee, Ji Eon Kwon, Soo Young Park
Summary: The study investigates the impact of alkyl chain length on the performance of all-small-molecule organic solar cells. It was found that increasing alkyl chain length led to a gradual increase in open-circuit voltage, attributed to the denser blend film formation with longer alkyl chain acceptors resulting in reduced voltage loss from nonradiative recombination.
ACS APPLIED ENERGY MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Heebum Roh, Donghyun Ko, Dong Yeol Shin, Jun Hyuk Chang, Donghyo Hahm, Wan Ki Bae, Changhee Lee, Jun Young Kim, Jeonghun Kwak
Summary: By introducing PMMA into QD inks, this study achieved enhanced performance of inkjet-printed QLEDs. The uniform droplets formed and reduced nonuniformity in QD morphology, showing potential application prospects in the fabrication process of full-color QLED displays.
ADVANCED OPTICAL MATERIALS
(2021)
Article
Physics, Applied
Jaehoon Kim, Taesoo Lee, Jeonghun Kwak, Changhee Lee
Summary: Polymer light-emitting diodes (PLEDs) have unique advantages but are hindered in commercialization by low stability. Analysis of PLEDs degradation using photovoltaic impedance characteristics reveals that degradation results in a shift of the center of DOS rather than broadening. Trap-assisted recombination is implied throughout the degradation process based on experimental results.
APPLIED PHYSICS LETTERS
(2021)
Article
Energy & Fuels
Jaehoon Kim, Hyung-Jun Song, Changhee Lee
Summary: The use of hydrophobic cyclized transparent optical polymer (CYTOP) as an encapsulation layer significantly improves the shelf lifetime of OSCs, maintaining 96% of initial performance compared to unencapsulated devices which decreased to 82%. CYTOP encapsulation effectively inhibits unfavorable changes of parasitic resistive components and trap-assisted recombination, indicating a promising strategy for enhancing the commercialization of OSCs.
Article
Chemistry, Physical
Byeong Guk Jeong, Jun Hyuk Chang, Donghyo Hahm, Seunghyun Rhee, Myeongjin Park, Sooho Lee, Youngdu Kim, Doyoon Shin, Jeong Woo Park, Changhee Lee, Doh C. Lee, Kyoungwon Park, Euyheon Hwang, Wan Ki Bae
Summary: This study presents an approach to control the potential profile of III-V-II-VI h-NCs by steering dipole densities at the interface, allowing for control of the optical and electrical characteristics of these heterostructured nanocrystals. The synthesis of h-NCs with atomic precision enables correlation of interfacial dipole moments with the crystals' photochemical stability and optoelectronic performance. Controlled synthesis of heterostructured III-V-II-VI nanocrystals demonstrates that dipole moments formed at the core-shell interface can tune the optoelectronic properties of these nanomaterials and their performance in light-emitting devices.
Article
Nanoscience & Nanotechnology
Jung Bae Son, Jooyoun Kang, Sohyeon Bae, Key Young Yang, Jongseok Han, Kyung Suk Min, Changhee Lee, Soohwan Sul, Seong Keun Kim
Summary: The irreversible loss of emission intensity in organic light-emitting diode (OLED) devices after extended operation is a significant issue in OLED technology and industry. A new method for in situ, layer-specific analysis of OLED devices demonstrates the predominant role of bleaching in influencing OLED performance.
Article
Energy & Fuels
Jeongkyun Roh, Swarup Biswas, Hyeong Won Lee, Yongju Lee, Jaeyeop Lee, Jaeyoul Kim, Changhee Lee, Hyeok Kim
Summary: Light-induced performance degradation is a major obstacle to the commercialization of organic solar cells (OSCs). This paper proposes a method using a field-effect transistor as a test platform to evaluate the photostability of OSC materials. The proposed platform enables rapid evaluation of the photostability of newly developed materials, boosting the development of photostable OSC materials.
Article
Materials Science, Multidisciplinary
Hyeyoung Ha, Hayoung Lee, Inhye Heo, Young-jun Seo, Hyosun Kim, Yongwoo Yi, Jaejoong Kwon, Changhee Lee
Summary: The study proposes a method for predicting image brightness on a display based on its color gamut, and verifies its performance through experiments. The results show that the image appears brighter with an increase in color gamut, indicating the effectiveness of the proposed method.
JOURNAL OF INFORMATION DISPLAY
(2022)
Article
Engineering, Electrical & Electronic
Myoungjin Park, Young Il Kim, Yun Ku Jung, Jin-goo Kang, Sehun Kim, Jaekook Ha, Yeo-geon Yoon, Changhee Lee
Summary: Electroluminescence quantum dot devices (QD-LEDs) hold great promise for future display technology, particularly the top emission device structure which allows for high aperture ratio full color displays. This study successfully demonstrates the fabrication of all inkjet-printed Cd-free active matrix QD-LED devices, overcoming the challenges of the inkjet printing process. Factors influencing QD efficiency and printing, as well as the impact of ETL solvent on QD, were investigated. The inkjet-printed QD-LED devices achieved high current efficiencies, marking an important step towards the practical application of Cd-free QD-LED displays.
JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY
(2022)
Article
Multidisciplinary Sciences
Mihyang Sheen, Yunhyuk Ko, Dong-uk Kim, Jongil Kim, Jin-ho Byun, YongSeok Choi, Jonghoon Ha, Ki Young Yeon, Dohyung Kim, Jungwoon Jung, Jinyoung Choi, Ran Kim, Jewon Yoo, Inpyo Kim, Chanwoo Joo, Nami Hong, Joohee Lee, Sang Ho Jeon, Sang Ho Oh, Jaekwang Lee, Nari Ahn, Changhee Lee
Summary: In this study, a blue nanorod LED with high external quantum efficiency (EQE) was demonstrated by reducing the size-dependent efficiency reduction through passivation. This work paves the way for manufacturing self-emissive nanorod LED displays for next-generation display technologies.
Article
Materials Science, Multidisciplinary
Chi Hyun Ryoo, Jongseok Han, Jung-hoon Yang, Kwangmo Yang, Illhun Cho, Seyoung Jung, Sehun Kim, Hyein Jeong, Changhee Lee, Ji Eon Kwon, Illia E. Serdiuk, Soo Young Park
Summary: By introducing substituent groups, efficient blue TADF materials can be developed, exhibiting high external quantum efficiency in OLEDs.
ADVANCED OPTICAL MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Sadia Sayed Urmi, Mohammad Masum Billah, Sunaina Priyadarshi, Jinbaek Bae, Byunglib Jung, Suhui Lee, Keunwoo Kim, Jiyeong Shin, Sangun Choi, Junhyung Lim, Taewook Kang, Changhee Lee, Jin Jang
Summary: We present a novel active split structure of low-temperature polysilicon (LTPS) thin film transistor (TFT) on polyimide (PI) substrate, which exhibits robust electrical performance under mechanical strain. Compressive and tensile bending tests were conducted with cylinders of radii 3, 2, and 1 mm, respectively. Compared to the conventional TFT, the active split TFT shows much more stable electrical performance. The conventional LTPS TFT experiences electrical failure when subjected to tensile or compressive bending with a 1 mm radius cylinder, while the split poly-Si islands in the active split TFT resist crack formation/propagation, resulting in robust electrical performance.
IEEE ELECTRON DEVICE LETTERS
(2023)
Review
Chemistry, Multidisciplinary
Jaehoon Kim, Jeongkyun Roh, Myoungjin Park, Changhee Lee
Summary: Colloidal quantum dots (QDs) have great potential in display technologies due to their unique optical properties. Significant improvements have been achieved in quantum dot light-emitting diodes (QLEDs) in the past decade, primarily through the development of high-quality QDs and optimized device architectures. This review provides insights into the current status and development direction of QLEDs, guiding the way towards their commercialization.
ADVANCED MATERIALS
(2023)
