A small PETE device made with cesium-coated gallium nitride glows while being tested inside an ultra-high vacuum chamber.
Stanford engineers have discovered a process called photon enhanced thermionic emission (PETE) that simultaneously combines the light and heat of solar radiation to generate electricity, and could offer over double the efficiency of existing solar cell technology. The process could reduce the costs of solar energy production enough for it to compete with oil.

"This is really a conceptual breakthrough, a new energy conversion process, not just a new material or a slightly different tweak," said Nick Melosh, an assistant professor of materials science and engineering, who led the research group. "It is actually something fundamentally different about how you can harvest energy."

Melosh's group figured out that by coating a piece of semiconducting material with a thin layer of the metal cesium, it made the material able to use both light and heat to generate electricity. While most silicon solar cells have been rendered inert by the time the temperature reaches 100 °C, the PETE device doesn't hit peak efficiency until it is well over 200 °C. The team would like to design the devices so they could be easily bolted on to existing systems, thereby making conversion relatively inexpensive.

In the video below, Melosh describes how the system works from his Stanford lab.