In this paper, we report a new molecular architecture for increasing the emission efficiency of nicotinonitrile-derivatives-based donor-acceptor-donor combined thermally activated delayed fluorescence (TADF) emitters with asymmetric molecular architecture. The proposed molecular design facilitates highly effective TADF emission through a relatively small singlet (S1) and triplet (T1) energy gap (ΔEST ≈ 0.1 eV) and provides an increased reverse intersystem crossing efficiency (ΦRISC) of up to 86% from T1 to S1 states. Organic light-emitting diodes (OLEDs) employing the proposed asymmetric nicotinonitrile derivatives as emitters exhibit external quantum efficiencies (ηext) of up to 18.5% in greenish-blue and green emissions.
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