High-efficiency organic electroluminescent materials based on the D–A–D type with sterically hindered methyl groups. Issue 20 (23rd April 2020)

• Record Type: Journal Article
• Authors: Zhang, Youming; Zhou, Xuan; Zhou, Changjiang; Su, Qiang; Chen, Shuming; Song, Jun; Wong, Wai-Yeung
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 20(2020)
• Page Start: 6851
• Page End: 6860
• Publication Date: 2020-04-23
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0tc00596g
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Emitters with the hybridized local and charge-transfer (HLCT) feature of 2TPA-BT, 2MeTPA-BT and 2DMeTPA-BT were designed and synthesized. The crystal structures show that the methyl groups have great influence on their spatial configuration. Abstract : Three donor–acceptor–donor type emitters of 2TPA-BT, 2MeTPA-BT and 2DMeTPA-BT were synthesized. Crystal structures for all compounds were determined by single-crystal X-ray diffraction analysis, showing that by introducing one or two methyl groups between the donors and acceptor, the spatial configuration changes greatly for 2MeTPA-BT and 2DMeTPA-BT compared to their parent compound 2TPA-BT . Density functional theory analysis reveals that the emission of 2MeTPA-BT has a more obvious hybridized local and charge-transfer (HLCT) feature based on the influence of steric hindrance of methyl substituents. Attributed to their different spatial configurations and luminescence mechanisms, different emission wavelengths with high photoluminescence quantum yields ( Φ PL s) of 75.43%, 93.43% and 89.63% in toluene solvent, as well as 44.76%, 52.19 and 33.87% in neat film, were observed for 2TPA-BT, 2MeTPA-BT and 2DMeTPA-BT, respectively. Furthermore, strong electroluminescence was observed with the emission peaks at 602, 560 and 544 nm, maximum current efficiencies of 11.05 cd A −1, 30.40 cd A −1 and 25.02 cd A −1, maximum power efficiencies of 6.01 lm W −1, 23.67 lm W −1 and 20.37 lm W −1, and maximum external quantum efficiencies of 4.43%, 8.47% and 7.29% for 2TPA-BT, 2MeTPA-BT and 2DMeTPA-BT doped organic light-emitting devices (OLEDs), respectively. This work clearly illustrates the effect of spatial configuration changes on the luminescence properties of organic emitters.