Efficient single layer yellow light emitting diodes made of a bleed of a ladder-type poly(p-phenylene) and polyalkylthiophene

We present the realisation of efficient yellow polymer light emitting diodes (PLEDs), in a single layer configuration, which is of considerable interest because of the ease of production of the PLEDs. We found that the electroluminescence-quantum-efficiency of PLEDs made of a blend of a blue emitting laddertype poly(p-phenylene) (m-LPPP) and small amounts of an orange emitting poly(decyl-thiophene) (PA10T) is significantly improved to 4.2% compared with PLEDs fabricated of pure m-LPPP (2%). In this paper we compare electroluminescence efficiencies of PLEDs made of different concentrations of PA10T in the polymer blend and discuss the observed aggregation effect, which alters the photophysical properties. (C) 1999 Elsevier Science B.V. All rights reserved.