Polythiophene polymers in light emitting diodes: making multicolour devices

Summary form only given. Polythiophenes with alkyl and alkylphenyl substituents, with bandgaps from 1.8 to 3 eV, have been synthesised and used in polymer light emitting diodes. The bandgap is systematically tuned by the pattern and character of substituents on the polythiophene main chain. Steric repulsion between substituents and the main chain forces the polymer out of planarity, increasing the bandgap. By using these soluble polymers in light emitting diodes we have obtained the colours blue, green, red and infrared, with quantum efficiencies reaching the 0. I- I % range. Using multilayers we have obtained multicolour emission in these diodes. Special geometries allows the use of these polymer LEDs as /spl les/100 nm diameter light sources.