title: Adjusting Nitrogen Atom Orientations of Pyridine Ring in Tetraphenylsilane-Based Hosts for Highly Efficient Blue Phosphorescent Organic Light-Emitting Devices.
abstract: Four wide bandgap host materials, namely, 9-(4-diphenyl(4-(pyridin-3-yl)phenyl)silyl-phenyl)-9H-carbazole (CSmP), 9-(4-diphenyl(4-(pyridin-2-yl)phenyl)silylphenyl)-9H-carbazole (CSoP), 9-(4-diphenyl(4-(pyridin-3-yl)phenyl)silylphenyl)-9H-3,9'-bicarbazole (DCSmP), and 9-(4-(diphenyl(4-(pyridin-2-yl)phenyl)silyl)phenyl)-9H-3,9'-bicarbazole (DCSoP), have developed by incorporation of pyridine with varied N atom orientation and carbazole/dimer carbazole units into the tetraphenylsilane skeleton for blue phosphorescent light-emitting diodes. These host materials all possess wide bandgap (3.54-3.64 eV) and high triplet energies (2.77-2.95 eV). As revealed by the absorption and emission spectra, theoretical calculations, and CV measurements, the N atom orientation exerts a strong influence on the LUMO energy level and electron-transportation behaviors without deterioring the photophysical properties. Among them, DCSmP with 3-pyridyl substituent manifests the best electron-transporting capability. The FIrpic-doped blue phosphorescent device using DCSmP as host material exhibits excellent electroluminescence performance with a maximum current efficiency of 40.1 cd A(-1) and a maximum external quantum efficiency of 20.0%. The current efficiency and external quantum efficiency are improved 3-fold, higher than those fabricated from DCSpP with 4-pyridyl as substituent, demonstrating an effective strategy for large improvement in device performance by a subtle change in molecular structure.
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Qing
authors: Q
authors: Bai
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: He
authors: H
authors: Liu
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Liang
authors: L
authors: Yao
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Tong
authors: T
authors: Shan
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Jinyu
authors: J
authors: Li
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Yu
authors: Y
authors: Gao
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Zhe
authors: Z
authors: Zhang
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Yulong
authors: Y
authors: Liu
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Ping
authors: P
authors: Lu
authors: State Key Laboratory of Supramolecular Structure and Materials, Jilin University , No. 2699, Qianjin Street, Changchun, Jilin 130012, P. R. China.
authors: Bing
authors: B
authors: Yang
authors: Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology , Guangzhou, Guangdong 510640, China.
authors: Yuguang
authors: Y
authors: Ma
keywords: blue PhOLED; carbazole; pyridine; tetraarylsilane; wide bandgap