A new solar cell designed to be more like an LED, able to emit
light as well as absorb it, could achieve efficiencies close to
30 percent. Typical solar cells theoretically can harvest about
33.5 percent of energy from sunlight, but scientists have yet to
reach this efficiency. Since 1961, scientists have known that,
under ideal conditions, solar cells at most will absorb and
convert 33.5 percent of electrical energy from incoming
sunlight. Yet for five decades, researchers have been
unsuccessful in achieving this efficiency: As of 2010, the
highest anyone had reached was just more than 26 percent.
Professor Eli Yablonovitch and colleagues at the University of
California, Berkeley, conducted research to understand why such
a significant gap remains between the theoretical limit and the
lesser limit that researchers have achieved. What they
discovered was a relatively simple, if perhaps counterintuitive,
answer based on a mathematical connection between absorption and
emission of light. A high-efficiency solar