Fabrication of White Organic Light-Emitting Diodes Using Two Complementary Color Methods

White organic light-emitting diodes (WOLEDs) were fabricated using two complementary color methods with two emissive layer structure such as NPB (500 Å)/DPVBi (65 Å)/MADN:DCM2-0.5% (170 Å)/Bphen (300 Å)/Liq (20 Å)/Al (1000 Å). A deep blue and orange emissions were obtained from DPVBi layer and MADN host doped with a red fluorescent DCM2 dopant each. White emission was achieved through controlling hole-electron recombination by optimization of emissive layers thicknesses and DCM2 concentrations. Optimized WOLED device shows emission efficiency of 5.04 cd/A, current density of 2.64 mA/cm2 and luminance of 938 cd/m2 at 6 V with CIEx,y color coordinate of (0.338, 0.330). These results indicate that DPVBi layer effects on hole blocking and the exciton generation due to difference of energy level in highest occupied molecular orbital. The CIEx,y coordinates of device was slightly changed change from (0.338, 0.330) at 6 V to (0.341, 0.333) at 12 V, which is almost independent on driving voltages.