Abstract
Conjugated polymers now provide a class of processible, film-forming semiconductors and metals. We have worked on the development of the semiconductor physics of these materials by using them as the active components in a range of semiconductor devices. In particular, we showed that these polymers could be used as the emissive layers in thin-film light-emitting diodes (LEDs),1 with improvement in device performance through control of chemical structure2 and by use of heterostructure device architectures.3 The physics of polymer semiconductor devices is reviewed in Greenham and Friend.4 Electroluminescent (EL) diodes can be made with semiconducting polymers using very simple structures, with polymer layers formed by solution processing sandwiched between charge injection electrodes, one of which is semitransparent. The prototypical polymer for this work is poly(p-phenylenevi-nylene), PPV. Cambridge Display Technology (CDT) has developed devices similar to this, using a conducting polymer layer between the PPV and indium-tin oxide (anode) and an alloy of aluminium with a low work-function metal, deposited by sputtering, as cathode. These now provide luminous efficiencies of 2 lumen/W and several thousand hours of operation.
© 1998 Optical Society of America
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