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Twist Angle and Rotation Freedom Effects on Luminescent Donor–Acceptor Materials: Crystal Structures, Photophysical Properties, and OLED Application
Author(s) -
Jiang Jianxia,
Hu Dehua,
Hanif Muddasir,
Li Xianglong,
Su Shijian,
Xie Zengqi,
Liu Linlin,
Zhang Shitong,
Yang Bing,
Ma Yuguang
Publication year - 2016
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201600608
Subject(s) - oled , materials science , triphenylamine , twist , acceptor , photoluminescence , luminescence , molecular geometry , crystallography , photochemistry , molecule , chemistry , optoelectronics , nanotechnology , physics , geometry , condensed matter physics , mathematics , organic chemistry , layer (electronics)
The twist angle and rotation freedom between the donor (D) and acceptor (A) in D–A materials plays an important role in their photophysical properties. Here, the authors select the asymmetric acceptor pyridal[2,1,3]thiadiazole (PT) to construct two D–A isomers ( p‐ TPA‐PT and d‐ TPA‐PT) with different twist angle and rotation freedom due to the donor triphenylamine (TPA) proximal or distal to N‐atom (pyridyl), as well as a symmetric bis‐triphenylamine‐substituted compound DTPA‐PT for their investigation. On the basis of experimental and theoretical analysis, the authors have explained how the difference in twist‐angle and freedom of rotation affects the photophysical properties of these materials. The p‐ TPA‐PT has small twist angles with a relative large k r , however, the more freedom of rotation of the D–A bond causes larger k nr , which is comparable to the k r , and thus a lower photoluminescence (PL) efficiency is obtained in the doped film. Although the d‐ TPA‐PT has relative large twist angles with low k r , the suppressed rotation of the DA bond significantly reduces k nr , resulting in more competitive k r when compared with the p‐ TPA‐PT, consequently relatively higher PL efficiency is observed. The DTPA‐PT, combination of p‐ TPA‐PT and d‐ TPA‐PT, shows highest k r , much larger than its k nr , therefore shows highest PL efficiency. As a result, the DTPA‐PT based organic light emitting diode (OLED) shows beautiful deep‐red emission, maximum external quantum efficiency of 3.87%, L max = 12 000 cd m −2 , which is among the best deep‐red OLED devices.