Modified 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran-containing red fluorescent emitters for efficient organic light-emitting diodes

Efficient red fluorescent compounds Red 1 and Red 2 based on bulky bicyclo[2,2,2]octane groups in the pyran moiety and tert-butyl or isopropyl group in the julolidine moiety of the 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran (DCJTB) skeleton were synthesized and characterized. As red-emitting dopants in an Alq3 single-host emitting system, Red 1 and Red 2 exhibited improved color purity and enhanced luminous efficiency compared to DCJTB. Moreover, a device using Red 1 as a dopant in a rubrene–Alq3 co-host emitting system exhibited improved electroluminescence performance with a luminous efficiency and power efficiency of 6.89 cd/A and 3.09 lm/W at 20 mA/cm2, respectively, and CIE x,y coordinates of (x = 0.64,y = 0.36) at 7.0 V, approaching saturated red emission.