Highly effective nicotinonitrile-derivatives-based thermally activated delayed fluorescence emitter with asymmetric molecular architecture for high-performance organic light-emitting diodes

Abstract

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 (S-1) and triplet (T-1) energy gap (Delta E-ST approximate to 0.1 eV) and provides an increased reverse intersystem crossing efficiency (Phi(RISC)) of up to 86% from T-1 to S-1 states. Organic light-emitting diodes (OLEDs) employing the proposed asymmetric nicotinonitrile derivatives as emitters exhibit external quantum efficiencies (eta(ext)) of up to 18.5% in greenish-blue and green emissions.