A comparative study of carbazole-based thermally activated delayed fluorescence emitters with different steric hindrance. Issue 19 (5th May 2017)

• Record Type: Journal Article
• Authors: Wang, Kai; Liu, Wei; Zheng, Cai-Jun; Shi, Yi-Zhong; Liang, Ke; Zhang, Ming; Ou, Xue-Mei; Zhang, Xiao-Hong
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 19(2017)
• Page Start: 4797
• Page End: 4803
• Publication Date: 2017-05-05
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7tc00681k
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Two carbazole-based thermally activated delayed fluorescence D–A structure emitters with different steric hindrance were designed and compared. Abstract : Thermally activated delayed fluorescence (TADF) emitters based on carbazole groups have been reported to realize different efficiencies in devices. Herein, we report two carbazole-based TADF emitters, namely 2-(9 H -carbazol-9-yl)thianthrene 5, 5, 10, 10-tetraoxide (CZ-TTR ), which has one free-rotation carbazole, and 2, 3-di(9 H -carbazol-9-yl)thianthrene 5, 5, 10, 10-tetraoxide (DCZ-TTR ), which has two mutually restricted carbazole groups, and investigated the influence of steric hindrance on their properties. Both compounds employed the same donor and acceptor segments and connecting mode. However, due to steric hindrance between the two carbazole segments, DCZ-TTR exhibited a smaller singlet–triplet splitting of 0.03 eV compared with that ofCZ-TTR (0.10 eV). The device containingDCZ-TTR showed significantly higher efficiencies (20.1% for external quantum efficiency (EQE), 58.5 lm W −1 for power efficiency (PE), and 59.6 cd A −1 for current efficiency (CE)) than those of theCZ-TTR -based device (EQE = 14.4%; PE = 32.9 lm W −1 ; CE = 32.5 cd A −1 ). These results clearly proved the necessity of introducing suitable steric hindrance when designing highly efficient TADF emitters based on carbazole groups.