Near-infrared (NIR) organic light-emitting diodes (OLEDs) generally suffer from low external quantum efficiencies (EQEs). Conventional NIR thermally activated delayed fluorescence (TADF) emitters predominantly rely on triphenylamine (TPA)-based donors, restricting further molecular design. Herein, we develop four new NIR-TADF emitters incorporating a rigid and strongly electron-donating donor unit, in which the charge-transfer characteristics are finely tuned by regulating the connection positions of cyano groups on the acceptor framework. Solution-processed neat-film OLEDs exhibit electroluminescence from 867 to 922 nm. Notably, the device based on tBPz-CN36 achieves an EQE of 0.01% at 922 nm, representing one of the highest values reported for neat-film NIR TADF OLEDs in this spectral region. This work demonstrates that the introduction of a rigid donor that is independent of the TPA system, together with acceptor-site engineering through regulation of cyano connection positions, provides an effective molecular strategy for achieving long-wavelength NIR TADF emission beyond conventional TPA architectures.
Li et al. (Mon,) studied this question.