Efficient single-layer yellow-light emitting diodes with ladder-type poly(p-phenylene)/poly(decyl-thiophene) blends

We present the realisation of efficient polymer light emitting diodes (PLEDs) with yellow emission in a single-layer configuration. We found that the external electroluminescence-quantum efficiencies 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) (PDT) are significantly improved to 4.2% compared with PLEDs fabricated of pure m-LPPP (2%). In this paper, electroluminescence and photoluminescence properties of different PLEDs consisting of m-LPPP and different amounts of PDT are compared. The results are discussed in terms of excitation energy transfer of Forster type and charge transfer. (C) 1999 Elsevier Science Ltd. All rights reserved.