Fabrication of White Organic Light-emitting Devices with Multi-emissive-layer Structure

White organic light emitting devices were fabricated using phosphorescent materials. The device structure was ITO/ NPB (20 nm/ DPVBi(x nm)/CDBP:5% Ir(btp)2acac(35 nm)/Alq3(y nm)/BCP(5 nm)/CsF(1 nm)/Al (150 nm), where NPB is a N,N'-bis-(1naphthyl)-N,N'–biphenyl-1,1'-biphenyl-4,4'-diamine as a hole transporting layer, DPVBi is 4,4 '-bis(2,2 -diphenylvinyl)-1,1 '-biphenyl as blue fluorescent dye, CDBP is 4,4’-bis(9carbazolyl)-2,2’-dimethylbiphenyl, Ir(btp)2acac is a bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2_]iridium (acetylacetonate) [(t-bt)2Ir(acac)], BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline as electron-transporting and hole-blocking layer, Alq3 is tris(8-hydroxyquinoline) aluminum as an green emitting layer. CsF layer inserted is used as a buffer layer to increase the electron injection efficiency. The thickness of DPVBi and Alq3 were 20nm and 25 nm and maximum luminance about 2453 cd/m 2 .