Efficient white-light-emitting organic electroluminescent devices

We report very efficient white OLEDs consisting of a blue-emitting 4,4'bis[N-(1-napthyl)-N-pbenyl-amino]-biphenyl (a-NPD), a hole-blocking layer of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) doped with red fluorescent 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-8-yl) vinyl]-4H-pyran) (DCM2), and green-emitting tris(8-hydroxyquinoline) aluminum (Alq 3 ). The device with the structure of ITO/a-NPD (50 nm)/BCP:DCM2 (0.8 %, 4 nm)/ Alq 3 (50 nm)/LiF (0.5 nm)/Al shows a white-light emission with the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.329, 0.333). The luminous efficiency is 2.6 lm/W and an external quantum efficiency is 2.1 % at a luminance of 100 cd/m 2 . The maximum luminance of 20,800 cd/m 2 is obtained at 15.4 V.