Highly efficient red thermally activated delayed fluorescence emitters by manipulating the molecular horizontal orientation

作者：Zhou, Changjiang; Cao, Chen; Yang, Dezhi; Cao, Xiaosong^*; Liu, He; Ma, Dongge; Lee, Chun-Sing^*; Yang, Chuluo^*

来源：Materials Chemistry Frontiers, 2021, 5(7): 3209-3215.

DOI：10.1039/d1qm00155h

• LIGHT-EMITTING-DIODES
• EXTERNAL QUANTUM EFFICIENCY
• EMISSION
• ACCEPTOR
• DESIGN

Developing highly efficient red thermally activated delayed fluorescence (TADF) emitters remains a formidable challenge due to strict molecular design principles. In this contribution, two red emitters PXZ-AQPy and PXZ-AQPhPy with high structural rigidity and linear configurations are designed and synthesized based on phenoxazine (PXZ) as a donor and acenaphtho[1,2-b]quinoxaline (AQ) as an acceptor. Both molecules with horizontal orientation are endowed with TADF and aggregation-induced emission (AIE) properties. By elongating the acceptor segment via phenyl decoration, PXZ-AQPhPy exhibits higher horizontal ratios of the emitting dipole orientation (Theta|| = 85%), while the emission characteristics are almost unaltered. Consequently, the PXZ-AQPhPy based device achieves a high external quantum efficiency of 19.6% with an emission peak at 610 nm. This work provides a simple and effective design strategy to selectively promote the horizontal orientation of red TADF emitters.