High Power Efficiency Blue-to-Green Organic Light-Emitting Diodes Using Isonicotinonitrile-Based Fluorescent Emitters.

Herein, 9,10-dihydro-9,9-dimethylacridine (Ac) or phenoxazine (PXZ)-substituted isonicotinonitrile (INN) derivatives, denoted as 2AcINN, 26AcINN, and 26PXZINN, were developed as a series of thermally activated delayed fluorescence (TADF) emitters. These emitters showed reasonably high photoluminescence quantum yields of 71-79 % in the host films and high power efficiency organic light-emitting diodes (OLEDs). Sky-blue emitter 26AcINN exhibited a low turn-on voltage of 2.9 V, a high external quantum efficiency (ηext ) of 22 %, and a high power efficiency (ηp ) of 66 lm W-1 with Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.22, 0.45), whereas green emitter 26PXZINN exhibited a low turn-on voltage of 2.2 V, a high ηext of 22 %, and a high ηp of 99 lm W-1 with CIE chromaticity coordinates of (0.37, 0.58). These performances are among the best for TADF OLEDs to date.