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 lm ∕ W ( 10.9 cd ∕ A ) at 10 mA ∕ cm 2 , 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.