Top-emitting organic light-emitting diodes using Cs/Al/Ag cathodes

A semi-transparent cathode composed of Cs (0.5 nm)/Al (2.0 nm)/Ag (20 nm) at the wavelength of 515 nm exhibited the transmittance of 52% and the reflectance of 46%, respectively. The top-emitting device with the glass/Ag (100 nm)/tin-doped indium oxide (ITO, 125nm)/4,4',4"-tris[2-naphthylphenyl-l-phenylaminoltriphenylamine (2-TNATA, 30nm)/4,4'-bis[N-(lnapthyl)-N-phenyl-aminol-biphenyl (NPB, 15 nm)/tris(8-quinolinolato) aluminum(111) (Alq(3), 55 nm)/Cs (0.5 nm)/Al (2 nm)/ Ag (20 nm)/Aiq(3) (52 nm) structure showed the maximum luminance of 77,200 cd/m(2). Also, the external quantum efficiency and the power efficiency at about 1,000 cd/m(2) were 1.9% and 2.5 lm/W, respectively. It shows about 2 times higher luminous efficiency, compared to the same device structure having lithium fluoride instead of cesium.