title: Structure-Performance Investigation of Thioxanthone Derivatives for Developing Color Tunable Highly Efficient Thermally Activated Delayed Fluorescence Emitters.
abstract: Thioxanthone derivatives consisting of undecorated carbazole as an electron donor and thioxanthone (TXO) or 9H-thioxanthen-9-one-S,S-dioxide (SOXO) as an electron acceptor in a donor-acceptor (D-A) or donor-acceptor-donor (D-A-D) structure were developed as thermally activated delayed fluorescence emitters to fabricate highly efficient fluorescent organic light emitting diodes. Their emission color was successfully tuned from blue to yellow by changing the sulfur atom valence state of the thioxanthone unit to tune intramolecular charge transfer effect. Their thermal, electrochemical, photophysical, and electroluminescent properties, and theoretical calculations were systematically investigated to illustrate the molecular structure and property relationships. Maximum external quantum efficiency (EQE) of 13.6% with Commission Internationale de L'Eclairage coordinates of (0.37, 0.57) was achieved for green light emission CzSOXO consisting of SOXO and carbazole in a D-A structure. Blue light emission CzTXO and DCzTXO consisting of TXO and carbazole in a D-A and D-A-D structure could also give EQE values exceeding 11%. Their efficiency roll-off with increasing current density was simulated by adopting triplet-triplet annihilation model, indicating that the TXO derivatives suffer more severe efficiency roll-off because of their relatively long delayed fluorescence lifetime (τ(D)).
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Zhiheng
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Yunchuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Xinyi
authors.initials: X
authors.lastname: Cai
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Dongcheng
authors.initials: D
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Gaozhan
authors.initials: G
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: KunKun
authors.initials: K
authors.lastname: Liu
authors.affiliation: Shenzhen China Star Optoelectronics Technology Company, Ltd. , Shenzhen 518132, China.
authors.forename: Yuan-Chun
authors.initials: YC
authors.lastname: Wu
authors.affiliation: Shenzhen China Star Optoelectronics Technology Company, Ltd. , Shenzhen 518132, China.
authors.forename: Chang-Cheng
authors.initials: CC
authors.lastname: Lo
authors.affiliation: Shenzhen China Star Optoelectronics Technology Company, Ltd. , Shenzhen 518132, China.
authors.forename: A
authors.initials: A
authors.lastname: Lien
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Shi-Jian
authors.initials: SJ
authors.lastname: Su
keywords: color tunable; intramolecular charge transfer; organic light emitting diodes; thermally activated delayed fluorescence; thioxanthone derivatives