High efficiency and long lifetime OLED based on a metal-doped electron transport layer

The OLED performance of cesium (Cs) doped 4,4'-bis(5-phenyl-[1,3,4]oxadiazol-2-yl)-2,2'-dinaphthylbiphenyl (bis-OXD), a metal-doped electron transport layer, is reported. Device lifetime increases because: (1) Cs is heavy and difficult to diffuse in an organic matrix, and (2) The host material, bis-OXD, exhibits a high glass-transition temperature (T.) of 147 degrees C. The average roughness of the thin film is small hence the leakage current of the corresponding OLED devices is low. By using a silver cathode, an OLED with a 2.59 V reduction in driving voltage, a 47.3% increase in current efficiency, and a 3.14 times enhancement in operation lifetime was demonstrated. (c) 2005 Elsevier B.V. All rights reserved.