title: Polarity-Tunable Host Materials and Their Applications in Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes.
abstract: A series of polarity-tunable host materials were developed based on oligocarbazoles and diphenylphosphine oxide, and their polarities can be tuned through increasing distance of acceptor and donor units. Density functional theory calculations were employed, and photoluminescence spectra in different polar solvents were measured to illustrate different polarities of these host materials. As CZPO has relatively stronger polarity, electroluminescence (EL) spectrum of solution-processed device based on 6 wt % PXZDSO2:CZPO is 7 nm red-shifted relative to that of other host materials based devices. Besides, a comparable impressive external quantum efficiency (EQE) value of 18.7% is achieved for an evaporation-processed yellow device consisting of FCZBn, which is superior to that of the device based on CBP (4,4'-dicarbazolyl-1,1'-biphenyl) (17.0%), and its efficiency roll-off is also obviously reduced, giving an EQE value as high as 16.3% at the luminance of 1000 cd/m2. In addition, from CZPO to FCZBn as the polarities of host materials decrease, EL spectra of solution-processed devices based on DMAC-DPS emitter blue-shift constantly from 496 to 470 nm. The current work gives a constructive approach to control EL spectra of organic light-emitting diodes with a fixed thermally activated delayed fluorescence emitter by tuning the polarities of host materials.
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: Dongjun
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: Xianglong
authors.initials: X
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: 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: 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: Kunkun
authors.initials: K
authors.lastname: Liu
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: Qian
authors.initials: Q
authors.lastname: Zhang
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: oligocarbazoles; organic light-emitting diodes; polarity-tunable host materials; spectra shift; thermally activated delayed fluorescence