LEDs produce light when incoming negatively charged electrons and positively charged "holes" attract each other and combine. The electrons and holes have a physical property called "spin" that rotates like the Earth rotating on its axis, but unlike the Earth they can spin in different directions. Physicists once believed that only 25% of the energy flowing into an LED could be emitted as light. Valy Vardeny, the physics chairman at the University of Utah, developed a test that indicates that 41 to 63% of the energy flowing into an LED can be converted to light using plastic LEDs made from organic materials called electrically conducting polymers and oligomers. Vardeny bombarded ten different plastics with microwaves, and found that materials that emit red and blue violet light emitted more light when placed in a magnetic field at cold temperatures. "The findings mean it should be possible to make more efficient light emitters for lasers, displays, and computer and television screens," says Vardeny. For more information, contact the University of Utah, Salt Lake City, UT 84112-9017; FAX: (801) 585-3350.
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