Spring 2014 IAB & Research Review
March 5 - 6

Prof. Eli Yablonovitch

The Opto-Electronic Physics Which Just Broke the Efficiency Record in Solar Cells

Solar cell science and technology is changing. New efficiency records have been set. Alta Devices has reached 28.8% efficiency in a thin film single-junction cell at 1-sun, and 30.8% efficiency in a thin-film dual junction cell at 1-sun.
Counter-intuitively, efficient external fluorescence is a necessity for approaching the ultimate limits. A great Solar Cell also needs to be a great Light Emitting Diode. Why would a solar cell, intended to absorb light, benefit from emitting light? Although it is tempting to equate light emission with loss, paradoxically, light emission actually improves the open-circuit voltage and the efficiency.
The single-crystal thin film technology that achieved these high efficiencies is created by epitaxial liftoff and can be produced at a cost well below the other less efficient thin film solar technologies. The path is now open to a 30% efficient photovoltaic technology that can be produced at low cost.