Sharp sets highest solar cell efficiency
By Paul Ridden
October 27, 2009
The Sharp Corporation has developed a compound solar cell that has achieved a conversion efficiency of 35.8 percent. Developing a new base layer for its triple-junction compound solar cell has improved on Sharp's previous conversion efficiency by almost four percent.
Compound solar cells are made up of layers of two or more elements which absorb light energy. They are used mainly on space satellites and although Sharp has had its cells on satellites for over 30 years, the company began researching triple-junction technology started in 2000 to improve conversion efficiency. In labs, conversion efficiency of greater than 40.0% has been achieved with these types of solar cells.
In order to improve the photo-sensitive nature of the stacked compound layers, Sharp replaced the germanium base layer in the triple-junction cell with indium gallium arsenide. Germanium generates a lot of current but much of this is wasted, the new compound is more efficient at utilizing the current generated.
Before creating the new structure, Sharp managed an impressive 31.5 percent conversion efficiency. Using the new compound has increased this to 35.8 percent, confirmed by Japan's National Institute of Advanced Industrial Science and Technology in September.
Sharp points out that these results have been achieved at the research level using a 1cm cell which means that the technology has not yet been incorporated into satellites. Encouraged by the results however, the company's researchers will push towards achieving even greater conversion efficiency.