Article
Chemistry, Multidisciplinary
Yanping Wang, Yusen Yang, Dingke Zhang, Tong Zhang, Shiyi Xie, Yu Zhang, Yong-Biao Zhao, Xiaoyun Mi, Xiuling Liu
Summary: This study reports an exciton sensitizing approach to improve the performance of quantum-dot light-emitting diodes (QLEDs) by forming excitons on a phosphorescent-dye-doped layer and transferring their energies to adjacent quantum-dot layer. The fabricated red QLEDs using this method achieve record high efficiency and good stability.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Kwangmo Yang, Sungho Nam, Joonghyuk Kim, Eun Suk Kwon, Yongsik Jung, Hyeonho Choi, Ji Whan Kim, Jaesang Lee
Summary: Despite decades of research, the cause of short lifetimes in blue PHOLEDs remains elusive. This study investigates how the electrical properties of the EML in blue PHOLEDs affect device degradation, finding that a high density of dopant carriers is the major factor triggering TPA-induced defects. To achieve long device lifetimes, minimizing dopant carrier density and controlling the non-uniform distribution of defects are crucial. These factors can be predetermined and controlled by the charge mobilities of the PHOLED EML, allowing for the realization of long-lifetime blue PHOLEDs.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Review
Multidisciplinary Sciences
Yanqin Miao, Mengna Yin
Summary: UEMLs have been widely applied to fabricate OLEDs and have advantages of simplified device structure and preparation process, more flexible design, lower material consumption, and complete exciton utilization.
Article
Chemistry, Multidisciplinary
Baoxi Li, Jingli Lou, Han Zhang, Ganggang Li, Xin He, Yu Huang, Nan Zheng, Zhiming Wang, Dongge Ma, Ben Zhong Tang
Summary: The hot exciton mechanism based on high-lying reverse intersystem crossing process is advantageous in achieving high-performance deep-blue OLEDs. To further improve device performance, a deep-blue emitter based on exciton recovery strategy, named CAT, is successfully designed. Through various measurements, the multi-channeled pathways of exciton utilization and the proportion of singlet excitons are comprehensively demonstrated. By achieving high exciton utilization efficiency, CAT-based non-doped OLEDs exhibit excellent external quantum efficiency and sensitized blue fluorescent OLEDs also achieve remarkable performance. The operational lifetime of the multi-channel sensitized device is evaluated for the first time, highlighting the significance of the exciton recovery strategy.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Zhiqiang Guan, Yang Li, Zhaohua Zhu, Zixin Zeng, Ziming Chen, Zhiwei Ren, Gang Li, Sai-Wing Tsang, Hin-Lap Yip, Yuan Xiong, Chun-Sing Lee
Summary: In this study, the PLQY and EQE of blue perovskite LEDs were improved by introducing CsAc and applying solvent annealing. Through these methods, non-radiative losses caused by trap-induced recombination and exciton-exciton annihilation were effectively suppressed.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Applied
Jihoon Kang, Ha Lim Lee, Junseop Lim, Jun Yeob Lee
Summary: In organic light-emitting diodes (OLEDs), host engineering is crucial for improving device performance. However, achieving high efficiency in blue phosphorescent OLEDs remains challenging due to the high triplet energy of blue phosphors. In this study, a thermally activated delayed fluorescence-type host with a sterically modulated carbazole-triazine backbone structure is developed. By incorporating a spatially twisted pi-spacer, the host exhibits a short delayed decay time and high triplet energy with a small singlet-triplet energy splitting. This photophysical modulation enables efficient utilization of triplet excitons, leading to significantly improved device performance with a maximum external quantum efficiency of 23.6%.
Article
Engineering, Environmental
Shunta Kakumachi, Thanh Ba Nguyen, Hajime Nakanotani, Chihaya Adachi
Summary: The quenching of electrically generated excitons in OLEDs limits the overall EL efficiency. A sudden exciton quenching was observed at the turn-on voltage region in a blue TTU-based OLED, which depends on the hole-transporting materials (HTMs). The voltage dependence of exciton quenching yield and EL spectra suggests a shift in the emission zone from the interface to the bulk of the EML with increasing voltage.
CHEMICAL ENGINEERING JOURNAL
(2023)
Review
Chemistry, Multidisciplinary
Yaxiong Wang, Ju Hui Yun, Lei Wang, Jun Yeob Lee
Summary: Improving the performance of blue OLEDs is a challenge in both scientific and industrial communities, with optimizing the fabrication process of devices, developing stable and efficient luminescence and transporting materials, and developing host materials with high triplet energy being key approaches. The bottleneck lies in improving operational lifetimes, decreasing efficiency roll-off, and maintaining high quantum efficiency, and more innovation is needed in this field.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Jiajun Luo, Longbo Yang, Zhifang Tan, Weiwei Xie, Qi Sun, Jinghui Li, Peipei Du, Qi Xiao, Liang Wang, Xue Zhao, Guangda Niu, Liang Gao, Shengye Jin, Jiang Tang
Summary: This study introduces a lead-free perovskite, CsEuBr3, which displays bright blue exciton emission at 448 nm with color coordinates of (0.15, 0.04) originating from specific transitions. It demonstrates high performance characteristics including short excited-state lifetime, excellent exciton diffusion diffusivity, and high quantum yield. This material is used to construct deep-blue PeLEDs with high efficiency and longevity, aiming to inspire further research in lanthanide-based perovskites for next-generation LED applications.
ADVANCED MATERIALS
(2021)
Article
Optics
Qi Zhu, Liang Zhou, Weiqiang Liu, Yingjie Cui, Ruixia Wu, Jiahai Wang, Qingduo Duanmu
Summary: An efficient blue organic electroluminescent device was achieved by optimizing the double light-emitting layers structure, selecting appropriate host materials, and adjusting the doping concentration. The device exhibited good thermal stability and high current efficiency, making it a promising candidate for practical applications in the field of optoelectronics.
OPTICS AND LASER TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
Yong-Chun Ye, Yang Shen, Wei Zhou, Shi-Chi Feng, Jiang-Ying Wang, Yan-Qing Li, Jian-Xin Tang
Summary: Perovskite light-emitting diodes (PeLEDs) show promise for next-generation high-definition displays due to their excellent color purity and low power consumption. A novel strategy of interfacial molecule control is demonstrated using a bifunctional material to enhance interaction and exciton management between the perovskite and electron-transport layers. This modification layer not only passivates surface defects but also blocks interfacial exciton transfer, resulting in improved external quantum efficiencies for green, blue, and red emissions.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Jae-Min Kim, Kyung Hyung Lee, Jun Yeob Lee
Summary: This study comprehensively investigates the exciton dynamics of electroplex hosts in blue PhOLEDs and correlates the steady-state triplet excitons in the host with device lifetime. A degradation modeling considering the impact of host triplet excitons and dopants on material degradation was developed, leading to enhanced operational stability. The characterization method and numerical modeling can help predict the device lifetime of PhOLEDs for specific host materials.
ADVANCED OPTICAL MATERIALS
(2022)
Article
Chemistry, Applied
Ruicheng Wang, Dehua Hu, Longjiang Xing, Ziquan Lu, Yihong Zhu, Zhichao Mao, Wen-cheng Chen, Yanping Huo, Shaomin Ji
Summary: Two new anthracene-based emitters, pipdAnCz and pipdAnTPA, are designed and synthesized to improve the efficiency of organic light-emitting diodes (OLEDs) by converting triplet excitons to singlet excitons. Both emitters possess characteristics of hot exciton and triplet-triplet annihilation (TTA), enabling the conversion of triplet excitons to singlet excitons from different energy levels.
Article
Chemistry, Multidisciplinary
Junseop Lim, Si Hyun Han, Jun Yeob Lee
Summary: The authors report on organic light-emitting diodes (OLEDs) emitting light through charge-transfer (CT) complex formation in the light-emitting layer. Two phosphorescent materials with energy level offset are chosen for efficient CT complex generation. The resulting CT complex emits a yellow light under an electric field and can be used to create white OLEDs with blue and yellow emissions at a quantum efficiency of 13.7%. Further material development is expected to enhance the quantum efficiency of CT complex OLEDs.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Yu Xia, Yon-Hui Lou, Yu-Hang Zhou, Yi-Ran Shi, Kai-Li Wang, Lei Cai, Chun-Hao Chen, Fan Hu, Zhao-Kui Wang, Liang-Sheng Liao
Summary: A novel defect-passivation strategy using isocyanate molecules is proposed to fabricate efficient sky-blue PeLEDs. The strategy reduces nonradiative recombination loss and improves carrier injection and transport capacities by reducing the confinement effect. The prepared sky-blue PeLEDs show significantly improved external quantum efficiency, and the isocyanate-based passivators are shown to be universal for improving PeLEDs performance.
ADVANCED FUNCTIONAL MATERIALS
(2022)
