Engineering a Practical Full-Spectrum Solar Cell
Researchers led by the Materials Science Division's Wladek Walukiewicz have designed a multiband solar cell in which two distinct materials are alloyed together using a common semiconductor fabrication technique. By engineering an alloy with multiple band gaps—the energies of light that can be absorbed by a material—costly fabrication steps can be avoided. In addition, such a design also improves the power conversion efficiency of solar cells, as a larger portion of the sun's energy can be translated into electrical current.
The team created a test cell by alloying gallium arsenide, a semiconductor employed in solar cells, with gallium nitride, a wide bandgap semiconductor used in light-emitting diodes. Narrow intermediate bands generated within the wide bandgap semiconductor serve as a ladder to promote electrons without conducting charge and thereby shorting out the solar cell.
These findings reveal light from the near-infrared well into the ultraviolet region of the solar spectrum could be absorbed by the multiband junction and converted into current. These results are the first to show a transition between intermediate and conduction energy bands in these materials, unveiling a missing link in the quest for a fully operational multiband solar cell device.