Double-twist pyridine-carbonitrile derivatives yielding excellent thermally activated delayed fluorescence emitters for high-performance OLEDs

Possessing high photoluminescence quantum yield (PLQY) and fast reverse intersystem crossing (RISC) process are critical for obtaining efficient thermally activated delayed fluorescence (TADF) emitters. Herein, two donor-spacer-acceptor molecules, namely, 4-(4-(9,9-dimethylacridin-10(9 H )-yl)phenyl)-2,6-dimethylpyridine-3,5-dicarbonitrile (Me-DMAC) and 4-(4-(10 H -phenoxazin-10-yl)phenyl)-2,6-dimethylpyridine-3,5-dicarbonitrile (Me-PXZ), were developed via a double-twist design strategy. The large hindrance induces a twisted geometry, leading to small Δ E ST values and fast RISC processes. The time-resolved photophysical measurements revealed the TADF emissions of these pyridine-3,5-dicarbonitrile-based molecules in doped thin films. High external quantum efficiency (EQE) values of 25.8% and 21.1% were achieved in organic light-emitting diodes (OLEDs) using green Me-DMAC and yellow Me-PXZ dyes, respectively, as emitters. Two dicyanopyridine-containing TADF emitters were developed via the double-twist design strategy, yielding EQE max values of 25.8% and 21.1%.