Light-emitting polymers - The shape of things to come?

Ten years ago, nobody imagined that polymers would be used as the light-emitting layer in light-emitting diodes (LEDs). In fact only a small number of research groups were aware that polymers could have semiconducting electronic properties. Now they form the basis of a new display technology that may develop to rival liquid crystals. The story starts in 1990 with the report by the Cambridge group of light emission when a voltage was applied to a thin film of the polymer poly(1,4- phenylenevinylene) (PPV) [ 1 ]. These early polymer LEDs were green-yellow, could only be seen in a dark room, had efficiencies of order 0.005% a, and lasted only a few minutes. Today, polymer LEDs can have efficiencies of a few per cent and lifetimes exceeding ten thousand hours have been demonstrated.