Article
Chemistry, Physical
M. Greenberg, S. Sanderson, R. D. White, G. Vamvounis, P. L. Burn, B. Philippa
Summary: Phosphorescent organic light emitting diodes (OLEDs) suffer from efficiency roll off at higher luminance. Non-uniform blend ratios within the emissive layer can minimize this loss of efficiency. This study uses a multi-scale modeling framework to investigate the mechanisms behind the performance changes in OLEDs with non-uniform blend ratios. The distribution of guests in the film affects charge carrier mobility and having a graduated guest profile broadens the recombination zone, thereby reducing second order annihilation rates and improving device efficiency.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Inorganic & Nuclear
Meng Wu, Nengquan Li, Chao Shi, Jialiang Song, Ruoqi Zeng, Feiyang Li, Qiuxia Li, Aihua Yuan, Chuluo Yang
Summary: We have designed and synthesized a new B- and N-embedded asymmetric heteroleptic phosphorescent iridium(iii) complex IrBNacac, which exhibits ambipolar characteristics. The complex shows good planarity and rich pi-pi interactions in the crystal state. It also exhibits effective red emission in the thin film state with a very narrow full width at half maximum, even narrower than that of model complexes. Considered the good photophysical properties and solubility, it was used as the emitting layer of an OLED device and showed good performance.
INORGANIC CHEMISTRY FRONTIERS
(2023)
Article
Chemistry, Applied
Chan Hee Ryu, Junseop Lim, Mingi Kim, Ilsup Shin, Jun Yeob Lee, Kang Mun Lee
Summary: Researchers have developed a blue-emitting iridium complex, IrTrz, based on a 1,2,4-triazole ligand, which exhibits stable blue emission, high thermal stability, and excellent electrochemical stability. Multilayer phosphorescent OLEDs using IrTrz as the blue emitter show low turn-on voltages and high external quantum efficiencies, with stable operational lifetimes exceeding 690 h.
Article
Chemistry, Multidisciplinary
So Yeong Jeong, Yongmin Jeon, Eunji Kim, Gibok Lee, Yeon-Wha Oh, Chi Won Ahn, Eun Hae Cho, Yonghee Lee, Kyung Cheol Choi
Summary: Flexible see-through displays, using MXene material as electrodes, have been developed for various applications, offering improved information flow, safety, situational awareness, and overall user experience. The ultraflexible and environmentally stable MXene-based OLED display can stably operate in air condition for over 2000 h, endure repetitive bending deformation, and maintain environmental stability when exposed to wet surroundings. A matrix-addressable transparent OLED display was also demonstrated that could display letters and shapes.
Article
Chemistry, Physical
Makarii I. Kozlov, Kirill M. Kuznetsov, Alexander S. Goloveshkin, Andrei Burlakin, Maria Sandzhieva, Sergey V. Makarov, Elena Ilina, Valentina V. Utochnikova
Summary: An approach to increase the efficiency of europium-based OLEDs was proposed through the formation of a mixed-ligand complex. By designing a series of europium complexes and optimizing the solution deposition process, including host selection and variation of solvent and deposition parameters, the luminance of the OLEDs was significantly increased. The maximum luminance of the Eu-based OLED reached up to 700 cd/m(2), which is one of the highest values for a solution-processed Eu-based OLED. Finally, the stability of the OLED was investigated.
Article
Biochemistry & Molecular Biology
Jie Yan, Ze-Lin Zhu, Chun-Sing Lee, Shih-Hung Liu, Pi-Tai Chou, Yun Chi
Summary: A series of novel Ir(III) metal complexes were synthesized efficiently and their emission hue was fine-tuned by varying the substituents on the coordination entities. Comprehensive examination and discussion of their photophysical, electrochemical, thermal stability, and electroluminescence performance were conducted, with promising potential for OLED applications demonstrated by relatively high electroluminescence efficiencies.
Article
Chemistry, Physical
Xiangyang Fan, Yu Wang, Xinyu Shen, Zhongkai Yu, Woo Hyeon Jeong, Ji Won Jang, Yeong Gyeong Kim, Seung-Je Woo, Hyungju Ahn, Hyosung Choi, Tae-Woo Lee, Sung Heum Park, Feng Gao, Bo Ram Lee
Summary: In this study, the energy level and hole mobility of the hole-transport layer (HTL) were modulated by incorporating tris(4-trifluoromethylphenyl)phosphine oxide (TMFPPO) into poly(9-vinylcarbazole) (PVK). This resulted in the elimination of the hole-injection barrier and balanced charge injection within the emissive layer (EML), leading to efficient blue PeLEDs with an external quantum efficiency (EQE) of 7.23% at 477 nm. These findings demonstrate the promising method of modulating the energy level and charge injection of the HTL to achieve efficient blue PeLEDs.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Chemistry, Multidisciplinary
Xingyu Feng, Jian-Gong Yang, Jingsheng Miao, Cheng Zhong, Xiaojun Yin, Nengquan Li, Chao Wu, Qizheng Zhang, Yong Chen, Kai Li, Chuluo Yang
Summary: This study demonstrates a strategy to improve the stability of gold(I) complexes by using a highly rigid and groove-like ligand to form dual Au⋅⋅⋅H-C hydrogen bonds. The complex exhibits appealing emission properties and improved stability. OLEDs show promising electroluminescence and operational stability.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Chemistry, Multidisciplinary
Haonan Zhao, Jongchan Kim, Kan Ding, Mina Jung, Yongxi Li, Harald Ade, Jun Yeob Lee, Stephen R. Forrest
Summary: By incorporating a sterically bulky, electron-transporting host material into a conventional single host-guest emissive layer, the phase separation of the host matrix can be suppressed, leading to improved efficiency and operational lifetime of deep-blue phosphorescent organic light-emitting diodes (PHOLEDs). This bulky host allows for homogeneous mixing of the emissive layer molecules while preventing single host aggregation and nonradiative recombination. The controlled amorphous phase morphology of the mixed-host device reduces nonradiative exciton decay and enhances external quantum efficiency by 120 +/- 6% compared to a similar single-host device. Additionally, the mixed host facilitates the conduction of both charge carriers, reducing the probability of exciton annihilation and doubling the operational lifetime of deep-blue PHOLEDs.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Ming-Xing Song, Xi-Lian Guo, Ye Ji, Jia-Yu Yang, Yun-Kai Zhang, Zi-Cong Pan, Mei-Qi Wang, Zheng-Kun Qin
Summary: This study applies density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to investigate cyclometallated Ir(III) complexes for their potential use as OLED light-emitting materials. The analysis includes geometry, molecular orbital properties, ionization potential, electron affinity, absorption and emission spectra, and spin-orbit coupling properties. Through comparison, complexes with reduced efficiency roll-off and enhanced k(ISC) have been identified.
INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
(2023)
Article
Chemistry, Multidisciplinary
Chengjun Wu, Youming Zhang, Jingsheng Miao, Kai Li, Weiguo Zhu, Chuluo Yang
Summary: The design of efficient and stable near-infrared (NIR) electroluminescent materials is challenging due to the high decay rate of non-radiative transitions in long wavelengths. A new tetradentate cyclometalated platinum(II) complex has been developed and used as a dopant for NIR organic light-emitting diodes (OLEDs). The NIR-OLEDs achieved a maximum external quantum efficiency of 5.2% and demonstrated excellent stability with an operational lifetime of 119 hours.
CHINESE CHEMICAL LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Hea Jung Park, Jae-Ho Jang, Ha Lim Lee, Jun Yeob Lee, Do-Hoon Hwang
Summary: Pt-Pytz is a blue phosphorescent Pt (II) complex with high quantum efficiency and excellent electroluminescent properties. In the solid state, Pt-Pytz suppresses molecular aggregation. When used as a blue dopant in organic light-emitting diodes, it exhibits good performance with high external quantum efficiency.
ORGANIC ELECTRONICS
(2021)
Article
Chemistry, Multidisciplinary
Xiaolong Yang, Shipan Xu, Yan Zhang, Chengyun Zhu, Linsong Cui, Guijiang Zhou, Zhao Chen, Yuanhui Sun
Summary: This study reports two NIR phosphorescent Ir(III) complexes with emission peaks around 730 nm and narrow full width at half maximum of only 43 nm. Pure NIR luminescence can be obtained without a very long emission wavelength, thus overcoming the restriction of the energy gap law and achieving impressively high photoluminescence quantum yield up to 0.70. Moreover, pure NIR organic light-emitting diodes (OLEDs) fabricated by solution-processing method show outstanding device performance with the highest external quantum efficiency of 16.43%, setting a new record for solution-processed NIR-OLEDs based on different emitters.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Parisa Sharif, Eda Alemdar, Soner Ozturk, Omer Caylan, Tugba Haciefendioglu, Goknur Buke, Murat Aydemir, Andrew Danos, Andrew P. Monkman, Erol Yildirim, Gorkem Gunbas, Ali Cirpan, Ahmet Oral
Summary: Observation of thermally activated delayed fluorescence (TADF) has revolutionized the molecular design of highly efficient OLEDs. The effectiveness of TADF is largely determined by the first-order mixing coefficient (lambda) and the difference between singlet and triplet excited state energies (Delta E-ST). While Delta E-ST has been the main focus, the influence of spin-orbit coupling (H-SO) has been overlooked. In this study, TADF materials with increased H-SO are achieved by substituting heteroatoms with heavy-atom selenium, resulting in remarkable EQEs.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Geochemistry & Geophysics
Yu Zhang, Yan Zhang, Ruigang Fu, Zhiguang Shi, Jinghua Zhang, Di Liu, Jinming Du
Summary: This article proposes a learnable feature modulation module that utilizes prior knowledge to enhance feature representation in target detection. By converting local contrast measure into nonlocal quadrature difference measure and using a self-attentive approach to determine potential target locations, features are enhanced. In addition, a multiscale single-stage detector is designed to consider scale changes of aircraft targets. Experimental results demonstrate the superiority of this method in highly complex and low-contrast scenes.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2022)
Article
Nanoscience & Nanotechnology
Vasudevan Thangaraji, Pachaiyappan Rajamalli, Jayachandran Jayakumar, Min-Jie Huang, Yu-Wei Chen, Chien-Hong Cheng
ACS APPLIED MATERIALS & INTERFACES
(2019)
Article
Chemistry, Multidisciplinary
Ya-Chun Hong, Rajagopal Santhoshkumar, Chien-Hong Cheng
JOURNAL OF THE CHINESE CHEMICAL SOCIETY
(2019)
Article
Chemistry, Organic
Lin-Chieh Cheng, Wei-Chen Chen, Rajagopal Santhoshkumar, Tzu-Hsuan Chao, Mu-Jeng Cheng, Chien-Hong Cheng
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
(2020)
Article
Chemistry, Organic
Vijaykumar H. Thorat, Jen-Chieh Hsieh, Chien-Hong Cheng
Article
Chemistry, Organic
Joydip De, Rohit Ashok Kumar Yadav, Rahul Singh Yadav, Santosh Prasad Gupta, Mayank Joshi, Angshuman Roy Choudhury, Jayachandran Jayakumar, Jwo-Huei Jou, Chien-Hong Cheng, Santanu Kumar Pal
Summary: A unique strategy involving a central benzene core with specific attachments led to the attainment of discotic nematic phase in the reported compounds. These compounds exhibit high solid-state emission and act as efficient deep-blue emitters in OLEDs with CIEx,y coordinates of (0.16, 0.07).
JOURNAL OF ORGANIC CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Krishan Kumar, Kiran Kishore Kesavan, Diksha Thakur, Subrata Banik, Jayachandran Jayakumar, Chien-Hong Cheng, Jwo-Huei Jou, Subrata Ghosh
Summary: The performance of newly developed functional pyrene derivatives with different functionalized pyridine units as hole-transporting materials for OLED applications was studied, showing stable performance and desirable characteristics in terms of electro-optical properties and device performance.
Article
Chemistry, Multidisciplinary
Yi-Kuan Chen, Jayachandran Jayakumar, Chia-Min Hsieh, Tien-Lin Wu, Chun-Cheng Liao, Jayabalan Pandidurai, Chang-Lun Ko, Wen-Yi Hung, Chien-Hong Cheng
Summary: The TPAmPPC compound is a highly efficient TADF material with excellent optical properties, demonstrating high photoluminescence quantum yields and superior device performance in OLEDs.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Organic
Vijaykumar H. Thorat, Yu-Lin Tsai, Yong-Ran Huang, Chien-Hong Cheng, Jen-Chieh Hsieh
Summary: In this study, a nickel-catalyzed cyclization reaction was reported, which allowed the generation of polysubstituted biaryl sultams by reacting 1,2,3,4-benzothiatriazine-1,1-dioxides with arynes. The reaction exhibited high tolerance towards substituents on every subunit. Mechanistic investigation revealed the formation of a diradical intermediate, which reacted with a nickel complex to form a nickelacycle intermediate and underwent subsequent cyclization through aryne insertion.
Article
Nanoscience & Nanotechnology
Sheng-Lin Deng, Yi-Kuan Chen, Jian Lei, Jayachandran Jayakumar, Chang-Lun Ko, Wen-Yi Hung, Tien-Lin Wu, Chien-Hong Cheng
Summary: The acceptor modification strategy is an effective method for tuning the emission color of TADF emitters. In this study, three TADF emitters with donor-acceptor structures were successfully synthesized, demonstrating greenish-yellow to orange-red emissions with high photoluminescent quantum yields in thin films. The nondoped OLEDs based on TPAmbPPC exhibited a remarkable EQE(max) of 21.6%, indicating its promising potential for OLED applications. Orange-red OLED devices based on TPAmCPPC showed high EQE(max), CE, and PE values.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Materials Science, Multidisciplinary
Chia-Min Hsieh, Yi-Kuan Chen, Jian Lei, Pang-Yu Chou, Song-Ting Hsieh, Chang-Lun Ko, Wen-Yi Hung, Tien-Lin Wu, Chien-Hong Cheng
Summary: In this study, a diboron-based molecule, PhCzDBA, is designed and its OLED device exhibits high EQE and stability, with low efficiency roll-off and long operational lifetimes. It shows potential and diverse applications in future display technology.
ACS MATERIALS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Yi-Kuan Chen, Jayachandran Jayakumar, Chang-Lun Ko, Wen-Yi Hung, Tien-Lin Wu, Chien-Hong Cheng
Summary: Three pyridine-carbonitrile (PPC) fluorophores with amine-type donors were designed and synthesized, showing high photoluminescence quantum yields, thermally activated delayed fluorescence (TADF) and thermal stability. By modifying the donors, the horizontal dipole orientation ratios were successfully increased. One of the dopants exhibited high external quantum efficiency and low driving voltage in a green OLED.
JOURNAL OF MATERIALS CHEMISTRY C
(2022)
Article
Materials Science, Multidisciplinary
Jayabalan Pandidurai, Jayachandran Jayakumar, Yi-Kuan Chen, Chia-Min Hsieh, Chien-Hong Cheng
Summary: This study focuses on the design, synthesis, and investigation of four new TADF emitters, aiming to achieve high internal quantum efficiency and external quantum efficiency through optimizing molecular structures and controlling intermolecular interactions. The results show that the Y-shaped emitters exhibit high photoluminescence quantum yields and efficient TADF, with important roles played by intramolecular interactions and hydrogen bonds in enhancing molecular rigidity and improving efficiency.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)
Article
Materials Science, Multidisciplinary
Indu Bala, Rohit Ashok Kumar Yadav, Manisha Devi, Joydip De, Nitya Singh, Kamalakannan Kailasam, Jayachandran Jayakumar, Jwo-Huei Jou, Chien-Hong Cheng, Santanu Kumar Pal
JOURNAL OF MATERIALS CHEMISTRY C
(2020)
Article
Materials Science, Multidisciplinary
Jayabalan Pandidurai, Jayachandran Jayakumar, Natarajan Senthilkumar, Chien-Hong Cheng
JOURNAL OF MATERIALS CHEMISTRY C
(2019)
Article
Chemistry, Organic
Yu-Che Chang, Sekar Prakash, Chien-Hong Cheng
ORGANIC CHEMISTRY FRONTIERS
(2019)
