Efficient white organic electroluminescent devices consisting of blue- and red-emitting layers

We report the fabrication and the characterization of white-organic-light-emitting devices consisting of a blue-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi) and a red-emitting layer of 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-8-yl)vinyl]-4H-pyran (DCM2) doped into either 4,4′bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (α-NPD) or tris(8-hydroxyquinoline) aluminum (Alq3). The spectral emission depends on both the doping location of DCM2 and its doping concentration. The electroluminescence (EL) spectra consist of two broad bands around 460 nm (DPVBi) and 560 nm (α-NPD:DCM2) or 590 nm (Alq3:DCM2). We obtained an efficient white-light emission from the devices with the 0.2% DCM2 doping in α-NPD layer. The device shows the CIE coordinates of (0.33, 0.36), an external quantum efficiency (QE) of about 3.1%, and a luminous efficiency of 3.75 lm/W at luminance 100 cd/m2. The maximum luminance of about 41,000 cd/m2 was obtained.