The University of New South Wales and its partners undertook a project to develop a cost-effective and high performance GaAsP/SiGe tandem solar cell on Si substrate with an efficiency over 33%.
This project is a partnership among UNSW Australia, AmberWave Inc., Veeco, Inc., Yale University, the University of Delaware and Arizona State University. The goal of this project is to develop a cost-effective and high performance GaAsP/SiGe tandem solar cell on Si substrate with an efficiency over 33%.
Silicon solar cells dominate the Photovoltaic (PV) market due to their performance, reliability and relatively low cost. However, the efficiency of the best silicon solar cells has stayed at around 25% for the last 17 years. Solar cells made of materials in the 3rd and 5th column of the periodic table (III/V materials) are known to yield the highest efficiencies, but the high cost of lattice-matched substrates and metal organic chemical vapor deposition (MOCVD) of the active device layers makes them prohibitively expensive for large scale terrestrial applications.
This programme combines the affordability of silicon substrates with limited III-V material thickness to increase the overall efficiency at an affordable cost. The greatest challenge is lattice-mismatch when developing III-V on Si tandem devices. Lattice match is required to achieve high efficiency. This has been addressed by a metamorphic silicon:germanium (SiGe) buffer grown between the silicon substrate and the gallium-arsenide phosphide (GaAsP) active device layers.