A pyridine based meta-linking deep-blue emitter with high conjugation extent and electroluminescence efficiencies

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 4; no. 26; pp. 6249 - 6255
• Main Authors: Zhu, Ze-Lin, Chen, Wen-Cheng, Zhang, Liang-Dong, Liu, Xiao-Le, Tong, Qing-Xiao, Wong, Fu-Lung, Lu, Feng, Lee, Chun-Sing
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Charge transfer; Colors (materials); Devices; Electric potential; Emission; Emitters; Molecular structure; Pyridines
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C6TC01689H

We designed and synthesized a bipolar deep-blue emitter 2,6-bis(4-(1-(4-( tert -butyl)phenyl)-1 H -phenanthro[9,10- d ]imidazol-2-yl)phenyl)pyridine ( 26BTPIPy ) based on a meta -linking D–π–A–π–D structure. Compared to its para -linking analogue ( 25BTPIPy ), the meta -linking in 26BTPIPy effectively shortens molecular conjugated length and restricts intramolecular charge transfer. Interestingly, unlike most other meta -linking emitters, a high fluorescence yield can be maintained in 26BTPIPy . This may be attributed to a relatively planar structure at the benzene–pyridine–benzene joint in 26BTPIPy leading to considerable overlapping of its frontier molecular orbitals. These suitable combinations of properties endow 26BTPIPy with efficient deep-blue emission and good bipolar carrier transporting characteristics. An organic light-emitting device using 26BTPIPy as an emitter shows a low turn-on voltage (2.8 V), deep-blue emission with a color index of (0.15, 0.09) and high current and external quantum efficiencies (4.16 cd A −1 and 5.15%). Besides, a bilayer device using 26BTPIPy as both an emitting and electron-transporting material also gives high performance with a current efficiency of 4.22 cd A −1 and a color purity of (0.15, 0.11).