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 6.0lm∕W (10.9cd∕A) at 10mA∕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.