High-Luminance Top-Emitting Organic Light-Emitting Diodes Using Cs∕Al∕Au as the Semitransparent Multimetal Cathode

Top-emitting organic light-emitting diodes (TEOLEDs) using an ultrathin cesium (Cs) layer capped with a semitransparent layer as an effective, electron-injecting cathode were fabricated by vacuum evaporation. The optical properties of at a wavelength of exhibited a transmittance of and a reflectance of . The cathode showed lower power consumption and higher luminance at the same forward bias voltage than the cathode. Using a tris(8-quinolinolato)aluminum(III) layer as the emissive material, a TEOLED based on the cathode showed a maximum luminance of at . An external quantum efficiency and the power efficiency of and , respectively, at a luminance of (corresponding to a bias voltage of ) was obtained. The good driving performance of this TEOLED was attributed to the excellent optical properties such as high transmittance and efficient-electron injection from the to the adjoining organic layer.