Effect of Phosphorescent Sensitizer on White Organic Light-Emitting Devices

We have fabricated high-efficiency white organic light-emitting devices by using the phosphorescent material fac tris (2-phenylpyridine) iridium Ir(ppy₃) as a sensitizer. Ir(ppy)₃ and the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9 enyl) (DCJTB) are co-doped into 4,4'-N,N'-dicarbazole-biphenyl (CBP) host. N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) acts as a blue light-emitting as well as hole-transporting layer. The chromaticity of white emission can be tuned by adjusting the concentration of Ir(ppy)₃ and DCJTB. The maximum efficiency and luminance of the device with 3-wt.% Ir(ppy)₃ and 2-wt.% DCJTB are 7.5 cd A^-1 and 12020 cd m^-2, respectively, which produces fairly pure white emission with the commission international De L'Eclairage coordinates of (0.33, 0.32) at 10 V.