Toward ultimate light efficiency on the cheap

Researchers at the University of Michigan have taken a major stride toward perfectly efficient lighting that is also relatively inexpensive and simple to make. The same material can also reveal the presence of water by changing color.

Incandescent bulbs turn only 5 percent of the electricity they use into light, while fluorescent LEDs can produce light from up to 25 percent of the electrons that pass through them. Phosphorescent LEDs offer the potential to turn every electron into a ray of light, but it is very difficult to achieve with inexpensive materials.

LEDs are semiconductors that produce light when an electric current runs through them. Carbon-based, or organic, semiconductors are much cheaper than inorganic semiconductors, but today's organic technologies rely on metals in the semiconductor to enable phosphorescence. This raises the price and sometimes makes the material toxic. Now, the team of Jinsang Kim, a professor of materials science and engineering and chemical engineering, developed bright, metal-free, organic, phosphorescent light emitters.