"Future" multi-junction groups grab US funds
25 universities and companies are set to share a $21.7 million government kitty to put the US at the forefront of emerging solar-power technology.
The money comes as part of the US Department of Energy's Solar America Initiative, which announced the new "Future Generation" project on November 8. The individual projects will run over three years, between 2008 and 2010.
One of the major stated themes of the program is to fund efforts to bring down the cost of multi-junction photovoltaic cells, which can currently reach 40.7 percent solar conversion efficiency under concentration.
Capitalizing on this is the Fairport, New York, company Wakonda, which is looking to grow GaAs cells similar to existing devices on inexpensive germanium foil, rather than single-crystal substrates.
At $2.1 million this is the largest of the Future Generation projects, although the company has itself contributed $1.2 million.
Sacrificing the usual germanium substrate is more economical, but it also makes for appreciably less efficient devices, with Wakonda targeting 15 percent efficiency by 2010.
This is the same target that has been set by a Massachusetts Institute of Technology (MIT) team in another effort closely related to existing multi-junction designs. Led by Vladimir Bukovic, this project involves using a cadmium or lead quantum dot layer that allows bandgap tuning.
By contrast, the Rochester Institute of Technology's InAs quantum dot layer project is targeting 40 percent efficiency in conjunction with existing GaAs PV technology.
Researchers from the University of Illinois are looking at innovating the optical element of PV designs, with micro-optic concentrators operating in conjunction with large numbers of GaAs micro-cells.
Some much more exotic approaches to multi-junction cells will also be undertaken by some of the other Future Generation researchers, exemplified by Arizona State's II-IV-V compound materials. Using ZnSnP2 and ZnGeAs2, the Arizona team's conversion target is 20 percent by 2010.
Veering sharply away from the multi-junction approach, but still using GaAs in interesting cylindrical configurations, is a University of California, San Diego, plasmonics research effort. A number of other plasmonics efforts, which rely on metals to transmit light otherwise not otherwise absorbed into the PV cell, also feature in the new Future Generation program.
