Red Light, Green Light
Researchers at Philips and the University of Amsterdam in the Netherlands have created the first material for light-emitting diodes (LEDs) and flat-panel displays that can glow two different colors. Other electroluminescent materials, like the familiar LED indicators on VCRs, emit light of one fixed hue when electricity flows through them. As a result, multicolor devices, such as flat-screen televisions and computer monitors, have required three different materials-one each for red, green, and blue.The new material is a mixture of a semiconducting polymer and a compound containing the metal ruthenium. Applying a voltage in one direction excites the metal, causing it to emit red light; an opposite voltage excites the polymer, which glows green. The dual-color material will allow designers to create full-color displays using two, rather than three, materials. This advance will simplify manufacture, and it will yield brighter displays because a larger portion of the screen surface will emit light at any given time. Philips expects the first small full-color displays that use the materials to be ready for market within three to five years.