Efficiency enhancement mechanism in yellow organic light-emitting devices with multiple heterostructures acting as an emitting layer

Abstract

The electrical properties of organic light-emitting devices (OLEDs) with multiple heterostructures consisting of N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4.4'-diamine (NPB)/5,6,11,12-tetraphenylnaphthacene (rubrene) emitting layers were investigated. The efficiencies of the OLEDs were significantly affected by the number of heterostructures. Although the turn-on voltage of the OLEDs increases with increasing number of NPB/rubrene heterostructures owing to an increase in the number of trapped holes, the efficiency of the OLEDs increases with increasing driving voltage and increasing number of heterostructures. The efficiency enhancement mechanism in the OLEDs with multiple heterostructures is described on the basis of the electrical results.