5,6-Dicyano[2,1,3]benzothiadiazole-based deep red/near infrared thermally activated delayed fluorescence emitter for efficient electroluminescent devices

Deep red to near-infrared organic light-emitting diodes (DR/NIR-OLEDs) have remarkably attracted much interest due to their potential applications in many areas.Herein, we present a simple structured near-infrared thermally activated delayed fluorescence (TADF) molecule (DMACCNBz) comprising a strong electron-accepting core (A) of 5,6-dicyano[2,1,3]benzothiadiazole (CNBz) end-capped with highest-energy molecular orbital (HOMO), rigid structure, and two strong electron donors (D) of 9,9-dimethyl-9,10-dihydroacridine (DMAC), thereby formulating a D-A-D type chromophore.The experimental and theoretical studies confirm that DMACCNBz is a TADF fluorophore with NIR emission ( PL = 738 nm) and a small singlet-triplet splitting energy (E ST ) of 0.07 eV.DMACCNBz is successfully applied as an emissive material in DR/NIR-OLEDs.The device using DMACCNBz 10 wt% doped emissive layer demonstrates a record-setting external quantum efficiency (EQE) of 7.19% with an emission peak at 696 nm, while the device using 30 wt% doping of DMACCNBz exhibits NIR emission with a peak at 722 nm, an EQE of 4.93%, and a maximum radiance of 4720 mW sr -1 m -2 .