High contrast organic light-emitting devices with improved electrical characteristics

High contrast organic light-emitting devices with low-reflection cathodes are fabricated. The cathode consists of a semitransparent metal layer, a phase-changing (PC) layer, and a reflective metal layer. With Al doped tris(8-hydroxyquinoline) aluminum as PC layer, devices exhibit the average reflectivity of the ambient light as low as about 13%. And its electrical characteristics are almost identical to that of a conventional device, although the thickness is increased by 70%. The improvement in conductivity could be attributed to the conductive Al cluster distributed in the organic matrix.