Effect of hole-blocking layer doped with electron-transport molecules on the performance of blue organic light-emitting device

A hole-blocking layer, bathocuproine (BCP), doped with an electron-transport material, tris(8-hydroxyquinolinato)aluminum (Alq3), was applied to blue organic light-emitting devices (OLEDs) in order to investigate its effect on the color purity and device stability. The color coordinate of a blue OLED with the BCP layer doped with 10% Alq3 molecules was not much degraded as x = 0.157 and y = 0.127, while the maximum efficiency and luminance reached ∼1.7 cd/A and ∼10 000 cd/m2, respectively. In particular, an approximately 18-fold-higher device lifetime has been achieved with the present Alq3-doped BCP layer compared to the undoped BCP layer. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)