Dr. Nadia El-Masry, professor of materials science and engineering, and Dr. Salah M. Bedair, professor of electrical and computer engineering, have won a $1.4 million grant to conduct research aimed at boosting the energy yield of multijunction solar cells made of gallium arsenide.
The North Carolina State University professors will collaborate on the research with Spectrolab, a subsidiary of Boeing that manufactures high-efficiency solar cells for the space program. Spectrolab scientists have developed a multijunction solar cell with an efficiency rating of 40.7 percent, according to company officials. The NC State research team aims to boost the efficiency rating of the Spectrolab cells to 45 percent.
Multijunction gallium arsenide solar cells are far more efficient than silicon cells, which have yet to reach 20 percent efficiency. Silicon cells, however, are much cheaper to produce, and this cost differential is the main reason multijunction gallium arsenide cells are used mostly in space. El-Masry said the efficiency gains achieved through this research project are expected to lower the energy costs sufficiently to make the gallium arsenide cells more competitive for earthbound applications.
To increase the efficiency of the cells, El-Masry said, the research team will seek to develop a fourth layer for three-layer Spectrolab cells. Each layer of a multijunction cell is tuned to convert specific wavelengths of the solar spectrum into electricity. The extra layer to be developed by the team would receive the now unused 1.0-to-1.4-electrovolt portion of the spectrum.
Most of the money for the research grant is from the U.S. Department of Energy's Solar America Initiative to improve solar cell technology. The department is funding 11 solar cell projects around the country totaling $13.7 million.