Color variable bipolar/ac light-emitting devices based on conjugated polymers

There is increased interest in developing color variable light emitting devices. We report here the fabrication of color variable bipolar/ac light-emitting devices based on conjugated polymers. The devices consist of blends of pyridine-phenylene and thiophene-phenylene based copolymers sandwiched between the emeraldine base form and the sulfonated form of polyaniline. ITO and Al are used as electrodes. The devices operate under either polarity of driving voltage with different colors of light being emitted, red under forward bias, and green under reverse bias. The relative fast time response allows the rapid switching of colors and ac operation. (C) 1997 American Institute of Physics.