title: Enhanced electroluminescence based on thermally activated delayed fluorescence from a carbazole-triazine derivative.
abstract: Thermally activated delayed fluorescence (TADF) properties of a dicarbazole-triazine compound, 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-3,3'-bicarbazole (CzT), and its OLED characteristics were investigated. An estimated small energy gap of about 90 meV between the singlet and triplet energy states of CzT made the up-conversion of triplet excitons back to a singlet state possible. The origin of the observed delayed fluorescence has been shown to be thermally activated delayed fluorescence. An organic light emitting diode (OLED) with CzT as an emitter showed the maximum external quantum efficiency (EQE) of 6%. For comparison, another carbazole-triazine derivative of 3-(2'-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1'-biphenyl]-2-yl)-9-phenyl-9H-carbazole (PhCzTAZ) with a similar structure was also studied. PhCzTAZ showed a low fluorescence quantum yield with no TADF.
authors.affiliation: Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan. adachi@cstf.kyushu-u.ac.jp.
authors.forename: Tomas
authors.initials: T
authors.lastname: Serevičius
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Ming-Cheng
authors.initials: MC
authors.lastname: Kuo
authors.forename: Shuo-Hsien
authors.initials: SH
authors.lastname: Cheng
authors.forename: Ken-Tsung
authors.initials: KT
authors.lastname: Wong
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Chang
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Kwong
authors.forename: Sean
authors.initials: S
authors.lastname: Xia
authors.forename: Chihaya
authors.initials: C
authors.lastname: Adachi