While generally more costly to manufacture than silicon, compound semiconductors (usually composed of elements from columns three and five of the periodic table) offer superior performance when fabricated into solar cells. One of the methods of reducing the cost of these more expensive materials is to deposit them in very thin layers on foreign substrates that are larger and cheaper than their native substrate. Researchers from Yale University’s School of Engineering and Applied Sciences have produced high performance cells composed of Gallium, Arsenic, and Phosphorus (GaAsP) on a substrate of Gallium-Phosphide (GaP) through a process called heteroepitaxy. This result is a major step towards producing high performance cells on the much less expensive silicon substrate as GaP is known to be compatible with silicon. The high voltage of the cells grown indicates that the Yale group’s process was able to suppress the formation of performance-degrading defects in the critical layers of the solar cell device. Cells of this kind, when optimized and integrated onto a silicon platform will offer far superior performance to a silicon cell alone at a hopefully small premium in price.
Tomasulo, K. Nay Yaung, J. Simon, and M. L. Lee (2012) GaAsP solar cells on GaP substrates by molecular beam epitaxy, APPLIED PHYSICS LETTERS 101, 033911, DOI: 10.1063/1.4738373