Non-reflective black cathode in organic light-emitting diode

A black conductive electrode with a resistivity of 6.75 x 10(-4) Ohm cm was fabricated by doping silicon monoxide into aluminum by simple thermal evaporation. The relative optical reflectance of such electrode layers within the visible spectral range was between 0.12 and 0.05. The black electrode was incorporated in an organic light-emitting diode (OLED) by sequential deposition of alpha-napthylphenylbiphenyl diamine, tris-(8-hydroxyquinoline) aluminum and the black layer on indium-tin-oxide-coated glass substrates. The black layer reduced the reflection of ambient light entering the device and resulted in a significant increase of the OLED display contrast ratio. The electroluminescence properties of the device incorporating the black layer were investigated. (C) 2003 Elsevier B.V. All rights reserved.