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 diode s (PLEDs), in a single layer configuration, which is of considerable intere st because of the ease of production of the PLEDs. We found that the electr oluminescence-quantum-efficiency of PLEDs made of a blend of a blue emittin g laddertype poly(p-phenylene) (m-LPPP) and small amounts of an orange emit ting poly(decyl-thiophene) (PA10T) is significantly improved to 4.2% compar ed with PLEDs fabricated of pure m-LPPP (2%). In this paper we compare elec troluminescence efficiencies of PLEDs made of different concentrations of P A10T in the polymer blend and discuss the observed aggregation effect, whic h alters the photophysical properties. (C) 1999 Elsevier Science B.V. All r ights reserved.