Molecular engineering of donor moiety of donor–acceptor structure for management of photophysical properties and device performances

• Acridine derived strong donor moiety for thermally activated delayed fluorescent emitters.
• Combination of acridine derived donor with diphenyltriazine acceptor.
• Efficient delayed fluorescence in the acridine donor based delayed fluorescent emitters.

Acridine and carbazole derived electron donors, 8,8-dimethyl-5-phenyl-8,13-dihydro-5H-indolo[2,3-c]acridine (4IA) and 13,13-dimethyl-11-phenyl-11,13-dihydro-5H-indole[2,3-b]acridine(3IA), were synthesized as strong donor moieties of thermally activated delayed fluorescent (TADF) emitters. The new donor moiety was included in the molecular structure of diphenyltriazine based TADF emitter to study the effect of geometrical structure of the donor on the photophysical and device characteristics of TADF emitters. The 4IA donor was better than the 3IA donor for small singlet-triplet energy splitting and TADF emission. TADF behavior was observed only in the 4IA based TADF emitter due to geometrical structure. A TADF emitter having the 4IA based donor moiety exhibited a blue color coordinate of (0.21, 0.31) and a quantum efficiency of 13.7%.

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