A new type of device that uses both heat and light from the sun should be more efficient than conventional solar cells, which convert only the light into electricity.

The device relies on a physical principle discovered and demonstrated by researchers at Stanford University. In their prototype, the energy in sunlight excites electrons in an electrode, and heat from the sun coaxes the excited electrons to jump across a vacuum into another electrode, generating an electrical current. The device could be designed to send waste heat to a steam engine and convert 50 percent of the energy in sunlight into electricity--a huge improvement over conventional solar cells.

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