Xie Gaozhan, Chen Dongjun, Li Xianglong, Cai Xinyi, Li Yunchuan, Chen Dongcheng, Liu Kunkun, Zhang Qian, Cao Yong, Su Shi-Jian
State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
ACS Appl Mater Interfaces. 2016 Oct 19;8(41):27920-27930. doi: 10.1021/acsami.6b08738. Epub 2016 Oct 4.
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/m. 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.
基于低聚咔唑和二苯基氧化膦开发了一系列极性可调的主体材料，其极性可通过增加受体和供体单元之间的距离来调节。采用密度泛函理论计算，并测量了不同极性溶剂中的光致发光光谱，以说明这些主体材料的不同极性。由于CZPO具有相对较强的极性，基于6 wt% PXZDSO2:CZPO的溶液处理器件的电致发光（EL）光谱相对于其他基于主体材料的器件红移了7 nm。此外，由FCZBn组成的蒸发处理黄色器件实现了18.7%的可比令人印象深刻的外量子效率（EQE）值，优于基于CBP（4,4'-二咔唑基-1,1'-联苯）的器件（17.0%），并且其效率滚降也明显降低，在1000 cd/m的亮度下EQE值高达16.3%。此外，随着主体材料极性从CZPO到FCZBn降低，基于DMAC-DPS发射体的溶液处理器件的EL光谱从496 nm持续蓝移到470 nm。当前工作提供了一种建设性方法，通过调节主体材料的极性来控制具有固定热激活延迟荧光发射体的有机发光二极管的EL光谱。
