William Yuan, a seventh-grader from Portland, OR, developed a three-dimensional solar cell that absorbs UV as well as visible light. The combination of the two might greatly improve cell efficiency. William's project earned him a $25,000 scholarship and a trip to the Library of Congress to accept the award, which is usually given out for research at the graduate level.

"Current solar cells are flat and can only absorb visible light," he said. "I came up with an innovative solar cell that absorbs both visible and UV light. My project focused on finding the optimum solar cell to further increase the light absorption and efficiency and design a nanotube for light-electricity conversion efficiency."