Design Strategy of Blue and Yellow Thermally Activated Delayed Fluorescence Emitters and Their All‐Fluorescence White OLEDs with External Quantum Efficiency beyond 20%

• DOI: 10.1002/adfm.201602507
• Publication Date: 2016-08-16T13:56:38Z
• Authors: Yunchuan Li; Xiang‐Long Li; Dongjun Chen; Xinyi Cai; Gaozhan Xie; Zuozheng He; Yuan‐Chun Wu; Alan Lien; Yong Cao; Shi‐Jian Su
• Keywords: Quantum Efficiency

Two thioxanthone‐derived isomeric series of thermally activated delayed fluorescence (TADF) emitters 1,6‐2TPA‐TX/3,6‐2TPA‐TX and 1,6‐2TPA‐TXO/3,6‐2TPA‐TXO are developed for organic light‐emitting diodes (OLEDs). Blue emission devices based on symmetrical 3,6‐2TPA‐TX with common vertical transition route realize an extremely high external quantum efficiency (EQE) 23.7%, ever highest EQE 24.3% is achieved yellow 3,6‐2TPA‐TXO by solely changing the sulfur atom valence state thioxanthone core. In contrast, their corresponding asymmetric isomers affected intramolecular energy transfer more severely a nonradiative deactivation pathway, to give much low values (<5%). By utilizing as blue emitter emitter, 20.4% all‐fluorescence white OLEDs.