The University of Arkansas has announced that researchers there and at Arkansas State University are getting over $1 million in new funding to further their work on creating better solar cells for spacecraft. NASA is providing the bulk of that — $735,000 — but matching funds also come from the two universities — $237,000 from the University of Arkansas and $86,000 from Arkansas State.
The theoretical maximum efficiency of silicon solar cells is around 29%. To get around this limit, cells are made with different materials and designed to capture energy not only from visible light but from the infrared and ultraviolet spectrum as well: triple junction cells. The highest quality cells are costly and reserved for use in space and concentrating solar collectors, where fewer of them need to be used. NASA has been using solar cells with an efficiency of around 23% while the industry maximum in the lab is around 44% using triple junction cells.
This new research is using alternative materials to silicone and is trying to get the conversion efficiency in space to over 40%. Here’s more from the University of Arkansas:
The funding will allow researchers in Manasreh’s Optoelectronics Research Lab to continue growing and functionalizing semiconductor and metallic nanoparticles to be used in solar cells. He said this work could eventually lead to the start of a private company based in Arkansas. In 2010, Manasreh received a five-year $1.13 million grant from the U.S. Air Force Office of Scientific Research, which included cost sharing from the University of Arkansas, to pursue similar and complementary work….
Manasreh employs two approaches to fabricate solar cells. Instead of silicon, the first approach involves a combination of copper, indium, gallium and selenium (CuInSe2and CuInGaSe2) as the semiconductor material to grow nanocrystals. The researchers make the nanocrystals functional by generating volatile ligands, which are molecules that bind to a central atom. The nanocrystals are then either converted into thin films or combined with titanium dioxide or zinc oxide nanotubes to create the desired solar cells. After fabrication of the cells, the researchers will test and evaluate their performance.
The second approach uses molecular beam epitaxy, a method of depositing nanocrystals, to create quantum dots made of indium arsenide (InAs). Quantum dots are nanosized particles of semiconductor material.
To enhance the performance of the solar cells, the researchers will use short ligands to couple metallic nanoparticles to the nanocrystals and quantum dots. They will then investigate the plasmonic effect of trapping sun light, which in turn increases the energy conversion efficiency. Just as a photon is the quantum of the electromagnetic waves, a plasmon is the quantum of charge waves generated by light.
Photo Credit: Bernt Rostad
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