title: A bipolar transporter as an efficient green fluorescent emitter and host for red phosphors in multi- and single-layer organic light-emitting diodes.
abstract: Multifunctional donor-acceptor compound 4,4'-bis(dibenzothiophene-S,S-dioxide-2-yl)triphenylamine (DSTPA) was obtained by linking a strongly electron-withdrawing core and a strongly electron-donating core with a biphenyl bridge in linear spatial alignment. DSTPA not only has suitable HOMO and LUMO levels for easily accepting both holes and electrons, it was also demonstrated to have a high fluorescence quantum yield of 0.98 and a high triplet energy level of 2.39 eV. Versatile applications of DSTPA for bipolar transport, green fluorescent emission, and sensitizing a red phosphor were systematically investigated in a series of multi- and single-layer organic light-emitting devices. In traditional multilayer devices, it shows excellent performance both in an undoped fluorescent device (used as a green emitter and achieving maximum current and power efficiencies (CE and PE) of 12.6 cd A(-1) and 9.4 Lm W(-1) , respectively) and in a red phosphorescent device (used as a host and achieving maximum CE and PE of 26.4 cd A(-1) and 26.3 Lm W(-1) , respectively). Furthermore, DSTPA was also simultaneously used as an emitter, a hole transporter, and an electron transporter in a single-layer device showing CE and PE of 5.1 cd A(-1) and 4.7 Lm W(-1) , respectively. A single-layer red phosphorescent device with efficiencies of 11.7 cd A(-1) and 12.6 Lm W(-1) was obtained by doping DSTPA with a red phosphor. The performances of all of the devices in this work are comparable to the best of their corresponding classes in the literature.
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Sciences, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR (P. R. China).
authors.forename: Jun
authors.initials: J
authors.lastname: Ye
authors.forename: Zhan
authors.initials: Z
authors.lastname: Chen
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.forename: Feifei
authors.initials: F
authors.lastname: An
authors.forename: Yi
authors.initials: Y
authors.lastname: Yuan
authors.forename: Wencheng
authors.initials: W
authors.lastname: Chen
authors.forename: Qingdan
authors.initials: Q
authors.lastname: Yang
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhang
authors.forename: Chun-Sing
authors.initials: CS
authors.lastname: Lee
keywords: bipolar charge transport; charge carrier injection; donor-acceptor systems; fluorescence; semiconductors