1. Molecular design of thermally activated delayed fluorescent emitters for narrowband orange–red OLEDs boosted by a cyano-functionalization strategy
- Author
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Xin Xiao, Zhengyang Bin, Yang Liu, Jingsong You, and You Ran
- Subjects
Materials science ,business.industry ,Exciton ,Relaxation (NMR) ,General Chemistry ,Fluorescence ,Chemistry ,OLED ,Optoelectronics ,Surface modification ,Quantum efficiency ,CN-group ,business ,HOMO/LUMO - Abstract
The establishment of a simple molecular design strategy to realize red-shifted emission while maintaining good color purity for multi-resonance induced thermally activated delayed fluorescent (MR-TADF) materials remains an appealing yet challenging task. Herein, we demonstrate that the attachment of a cyano (CN) functionality at the lowest unoccupied molecular orbital location of the MR-TADF skeleton can promote attractive red-shifted emission due to the exceptional electron-withdrawing capacity of the CN group, which represents the first example of orange–red MR-TADF emitters. Meanwhile, the linear CN group adopts a coplanar conformation with the MR-framework to restrict structure relaxation associated with rotation, which is beneficial to maintain a small full-width at half-maximum and thus a good color purity. The CNCz-BNCz-based OLED device, which utilizes a TADF sensitized mechanism to accelerate the up-conversion process of triplet excitons in the emitting layer, exhibits an outstanding external quantum efficiency (EQE) as high as 33.7%, representing the state-of-the-art performance for orange–red TADF-OLEDs., The first example of narrowband orange–red MR-TADF emitters has been developed, which realizes a record-high EQE of 33.7% in OLEDs.
- Published
- 2021
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