Long-lifetime, high-efficiency white organic light-emitting diodes with mixed host composing double emission layers

Abstract

A long-lifetime, high-efficiency white organic light-emitting diode was fabricated with a mixed host in one of double emission layers. The first layer comprised yellow rubrene doped in a mixed host consisting of 50% N, N′ diphenyl- N, N′ -bis-(1-naphthyl)- 1, 1′ -biphenyl- 4- 4′ -diamine (NPB) and 50% 2- (t -butyl)-9,10-bis (2′ -naphthyl)anthracene (TBADN). The second layer comprised blue 4, 4′ -bis[2-{4- (N,N -diphenylamino)phenyl}vinyl] biphenyl doped in TBADN. This device exhibited the longest lifetime, five times that of its pure NPB counterpart. The resulting efficiency was 6.0 lmW (10.9 cdA) at 10 mA cm2, 33% better than that of the NPB counterpart. These improvements were attributable to the mixed-host structure, which effectively dispersed carriers and gave a good charge balance. © 2006 American Institute of Physics.