PT  - JOURNAL ARTICLE
AU  - Xiang, Yepeng
AU  - Li, Pan
AU  - Gong, Shaolong
AU  - Huang, Yu-Hsin
AU  - Wang, Chun-Yu
AU  - Zhong, Cheng
AU  - Zeng, Weixuan
AU  - Chen, Zhanxiang
AU  - Lee, Wei-Kai
AU  - Yin, Xiaojun
AU  - Wu, Chung-Chih
AU  - Yang, Chuluo
TI  - Acceptor plane expansion enhances horizontal orientation of thermally activated delayed fluorescence emitters
AID  - 10.1126/sciadv.aba7855
DP  - 2020 Oct 01
TA  - Science Advances
PG  - eaba7855
VI  - 6
IP  - 41
4099  - http://advances.sciencemag.org/content/6/41/eaba7855.short
4100  - http://advances.sciencemag.org/content/6/41/eaba7855.full
SO  - Sci Adv2020 Oct 01; 6
AB  - Manipulating orientation of organic emitters remains a formidable challenge in organic light-emitting diodes (OLEDs). Here, expansion of the acceptor plane of thermally activated delayed fluorescence (TADF) emitters was demonstrated to selectively modulate emitting dipole orientation. Two proof-of-the-concept molecules, PXZPyPM and PXZTAZPM, were prepared by introducing a planar 2-phenylpyridine or 2,4,6-triphenyl-1,3,5-triazine substituent into a prototypical molecule (PXZPM) bearing a pyrimidine core and two phenoxazine donors. This design approach suppressed the influence of substituents on electronic structures and associated optoelectronic properties. Accordingly, PXZPyPM and PXZTAZPM preserved almost the same excited states and similar emission characteristics as PXZPM. The expanded acceptor plane of PXZPyPM and PXZTAZPM resulted in a 15 to 18% increase in horizontal ratios of emitting dipole orientation. PXZPyPM supported its green device exhibiting an external quantum efficiency of 33.9% and a power efficiency of 118.9 lumen per watt, competitive with the most efficient green TADF OLEDs reported so far.