12 Sep 17:06
by Zhi‐Ping Yan,
Li Yuan,
Yuan Zhang,
Meng‐Xi Mao,
Xiang‐Ji Liao,
Hua‐Xiu Ni,
Zhi‐Heng Wang,
Zhongfu An,
You‐Xuan Zheng,
Jing‐Lin Zuo
Through a steric-hindrance-assisted dual-core strategy, chiral organoboron structures are prepared by direct bonding of two multiple-resonance thermally activated delayed fluorescence (MR-TADF) monocores, realizing superior chiroptical property and dual-channel enhanced ultrapure blue emission. Furthermore, highly efficient circularly polarized organic light-emitting diodes (CP-OLEDs) with maximum external quantum efficiencies of 23.9% and 25.6% are achieved.
Abstract
The realization of luminescent materials with narrowband and circularly polarized luminescence (CPL) is of great significance for the development of future optical and photonic devices. Herein, through a steric-hindrance-assisted dual-core strategy, two pairs of chiral dual-core multiple resonance thermally activated delayed fluorescence (MR-TADF) materials (R/S-DOBN and R/S-DOBNT) are directly constructed by the bonding of two organoboron MR-TADF monocores (SOBN and SOBNT) with carbazole/3,6-di-tert-butyl-9H-carbazole and phenol derivative as donors, realizing obvious CPL and narrowband emissions. Furthermore, the dual-core effect in the prepared R/S-DOBN and R/S-DOBNT increases the transition oscillator strength two times more than that of a monocore structure, while maintaining the ultrapure blue emissions peaking at 453 and 459 nm with a narrower full-width at half-maximum of 21 nm through reorganization energy reduction. The circularly polarized organic light-emitting diodes based on the enantiomers exhibit ultrapure blue emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.14, 0.10) and (0.13, 0.12), high maximum external quantum efficiencies of 23.9% and 25.6%, and obvious circularly polarized electroluminescence with dissymmetry factors (|g
EL|) ≈ 10−3.
21 Jul 03:41
by Yanyan Liu, Jiaji Yang, Zhu Mao, Xiaojie Chen, Zhan Yang, Xiangyu Ge, Xiaomei Peng, Juan Zhao, Shi-Jian Su, and Zhenguo Chi
ACS Applied Materials & Interfaces
DOI: 10.1021/acsami.2c07617
08 Jul 18:40
by Huitian Du, Qian Zhou, Yuan Yu, Chenghao Liu, Jing Li, Chuang Zhang, Ziwu Ji, and Zhiyong Pang
The Journal of Physical Chemistry C
DOI: 10.1021/acs.jpcc.2c02993
08 Jul 18:16
by Dengliang Zhang,
Lingfeng Chao,
Guangrong Jin,
Zhaohui Xing,
Wei Hong,
Yonghua Chen,
Lei Wang,
Jiangshan Chen,
Dongge Ma
Efficient red perovskite light-emitting diodes (PeLEDs) with high luminance and low efficiency roll-off are fabricated by manipulating the crystallization kinetics of PEABr-CsPbI3. The nonradiative losses are greatly reduced in the passivation-free perovskite films with excess PbI2 and anti-solvent treatment. The optimized PeLEDs achieve a peak external quantum efficiency of 19.6%, which keeping at 17.2% under the luminance of 1000 cd m–2.
Abstract
CsPbI3 is attractive for efficient and cost-effective red perovskite light-emitting diodes (PeLEDs), but its black phases still suffer from the metastable structure. The incorporation of large-size organic cations has been widely used to construct quasi-2D perovskites to stabilize the black phases. However, the multiple-phase quasi-2D perovskites usually show abundant interface defects and enhanced Auger recombination, leading to the low luminance and serious efficiency roll-off in PeLEDs. Herein, highly efficient red PeLEDs are demonstrated with high luminance and low efficiency roll-off realized by manipulating the crystallization kinetics of phenethylamine bromide (PEABr) incorporated CsPbI3. PEABr-CsPbI3 nanocrystal films with much larger and more oriented β-CsPbIxBr3-x grains are successfully obtained through appropriately increasing PbI2 content and coordinating with anti-solvent treatment. The carrier recombination dynamics investigations reveal that the trap-assisted recombination and Auger recombination are greatly reduced in the passivation-free PEABr-CsPbI3 films by rational crystallization regulation. A peak external quantum efficiency (EQE) up to 19.6% is achieved in the red PeLEDs with a stable emission peak at 672 nm, which is maintained as high as 17.2% at a high luminance of over 1000 cd m−2. This study could shed light on modulating the crystallization kinetics of pervoskites to optimize carrier recombination dynamics toward high performance PeLEDs.
08 Jul 18:10
by Akash Thamarappalli,
Chandana Sampath Kumara Ranasinghe,
Junhyuk Jang,
Mile Gao,
Paul L. Burn,
Emma V. Puttock,
Paul E. Shaw
Dual emission light-emitting dendrimers composed of phosphorescent fac-tris[2-phenylpyridine]iridium(III) cores and thermally activated delayed fluorescence-based (TADF-based) dendrons show solvatochromism, with the emission switching between phosphorescence and TADF depending on the medium in which the measurement is undertaken. Solution processed organic light-emitting diodes with the dendrimers blended in a host result in green emission with an external quantum efficiency of up to 15.1%.
Abstract
Dual emission light-emitting dendrimers composed of phosphorescent fac-tris[2-phenylpyridyl]iridium(III) [Ir(ppy)3] cores and thermally activated delayed fluorescence-based (TADF-based) dendrons have been prepared. The TADF-based dendrons are designed to have green or blue emission. The dendrimers show solvatochromism, with the emission switching between phosphorescence and TADF depending on the medium in which the measurement is undertaken. Time-dependent photoluminescence (PL) spectra measurements show that the TADF dendrons can act as an energy pool for emission from the phosphorescent core. The PL quantum yields (PLQYs) are found to be strongly dependent on the dielectric constant of the solvent, ranging from as high as 76% to as low as 0.3%. Neat films of the dendrimers are found to have relatively balanced hole and electron mobilities of order 10–6 cm2 V–1 s–1, with bilayer organic light-emitting diodes (OLEDs) containing neat emissive layers having a maximum external quantum efficiency (EQE) of 4.7% for a film having a PLQY of 12%. Finally, the solution processed OLEDs fabricated using 0.4 mol% of the dendrimers blended with 9-[3-(9H-carbazol-9-yl)phenyl]-9H-carbazole-3-carbonitrile result in green emission with maximum EQEs of 9.8% and 15.1% for the dendrimers with green and blue emissive TADF dendrons, respectively.
08 Jul 17:31
by Hongjing Han,
Sujuan Hu,
Shilong Zhang,
Xiaojun Li,
Hailing Sun,
Jiawen Chen,
Baiquan Liu,
Chuan Liu,
Wangqiao Chen,
Qichun Zhang
Two new pyrene-based polyaromatic hydrocarbons (PAHs) molecules-PyS and PyD were synthesized. Due to the more twisted and extended backbone, the bis-fused molecule PyD packed in neat Cmca space group in single-crystal system compared with P21/n for PyS, which may be favorable to form excimers in the solid state and showed solution-processed non-doped single-white-emitting-molecule SEL-WOLED with high performance.
Abstract
Single-emitting-layer white organic light-emitting diodes (SEL-WOLEDs) have developed rapidly in recent years due to the outstanding advantages of high efficiency, simple device structure, low cost, less phase separation, and stable emission color. Nevertheless, the relatively complicated host-dopant system is usually essential for most previous SEL-WOLEDs and the development of simple non-doped SEL-WOLEDs lags behind. Hence the straightforward synthesis of single-white-emitting molecules for non-doped SEL-WOLEDs still remains a great challengeable task. In this article, we designed and synthesized two new pyrene-based polyaromatic hydrocarbons (PAHs) and used them as emitting layer materials in the OLED devices. When the molecules change from the mono-fused one to bis-fused one, the emitting light changes from greenish to white color. Further study indicated that the bis-fused molecule PyD with more twisted and extended backbone packed in neat Cmca space group in single-crystal system compared with P21/n for PyS, which may be favorable to form excimers in the solid state and broaden the emission spectrum in the OLEDs. As a result, a solution-processed non-doped single-white-emitting-molecule SEL-WOLED with high performance (e. g., a high color rendering index of 66) is reported. The findings will be beneficial not only to further development of simple WOLEDs, but also to other related organic optoelectronic technology.
Open Access
