Flexible light-emitting diodes made from soluble conducting polymers

The fabrication is reported of a fully flexible LED using poly(ethylene terephthalate) as the substrate, soluble polyaniline as the hole-injecting electrode, a substituted poly(1,4-phenylene-vinylene) as the electroluminescent layer, and calcium as the electron-injecting top contact. The structure is mechanically robust and may be sharply bent without failure. The LED is easily visible under room lighting and has an external quantum efficiency of about 1 percent. With a turn-on voltage for light emission of 2-3 V, the 'plastic' LED demonstrates that this unique combination of optical, electrical, and mechanical properties can be used to make novel structures that are compatible with conventional devices.