Isophorone derivative as red dopant for organic electroluminescent devices

The donor–acceptor functionalized molecule, bis(4-(2-(3,3-dicyanomethylene-5,5-dimethyl-1-cyclohexylidene)vinyl)phenyl)(1-naphthyl)amine (DPN-4CN), with symmetrical structure, was investigated for its application in optoelectronic devices. Red organic light-emitting diodes (OLEDs) were fabricated by doping DPN-4CN in tris(8-hydroxyquinolino) aluminum (Alq3) as red emitters, with a structure of ITO/NPB/Alq3:DPN-4CN/BCP/Alq3/LiF/Al. The device with a doping concentration of 2.5 wt% showed pure red emission with λmax at 654 nm and CIE coordinates of (0.62, 0.36), a high brightness of 5080 cd m−2 at a driving voltage of 12 V, a current efficiency of 2.14 cd A−1 and an external quantum efficiency of 1.07% at a current density of 20 mA cm−2. The current efficiencies and CIE coordinates of the device were almost constant over a current density from 1 to 200 mA cm−2.