Improvement of viewing angle and pixel contrast ratio in green top-emitting organic light-emitting devices

Green top-emitting organic light-emitting devices based on tris-(8-hydroxyl-quinoline) aluminum are fabricated with a low reflective Sm/Ag cathode and a comparative Al/Ag cathode. An additional 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP) layer, used as a light outcoupling layer, is deposited onto the SmAg cathode to improve device performances. The influence of different cathodes and the BCP layer on electrical and optical characteristics are investigated and discussed. It is worth mentioning that the introduction of the BCP layer not only enhances the brightness and the luminous efficiency but also improves the viewing angle and the pixel contrast ratio.