Scientists from Boeing's subsidiary, Spectrolab, recently announced that they have made solar cells with more than 40% power generation efficiency – a milestone that is the highest efficiency of any current optoelectronic device. The findings were published in the latest issue of Applied Physics Letters.
Conventional solar cells that are currently used, such as those used in homes or buildings, use only the natural light intensity of the sun, and are therefore relatively narrow in terms of optimal wavelengths for light energy utilization. The Spectrolab team used a multi-node aggregator battery, which can use a light source equivalent to 100 suns through a lens or the like. Moreover, multi-junction cells can utilize a wider range of wavelengths in sunlight and are therefore more efficient than single junction cells.
In the specific design, the scientists used three band gap substructures to decompose the broad spectrum of sunlight into three parts. Each of the substructures can capture different wavelengths of sunlight, which ensures that each substructure can effectively convert light into electrical energy. As a result, the conversion efficiency measured by the team was 40.7%, which exceeded the theoretical conversion efficiency limit of 40% for single-junction cells, the main reason being their multi-node structure.
Spectrolab's main mission is to apply PV cells and panels to the aerospace industry (most of the solar cells they manufacture today are used on satellites), but the company believes this breakthrough is also expected to be used in commercial solar cells.
The study was supported by the US Department of Energy's Renewable Energy Laboratory and will play an important role in the government's next steps. The United States plans to achieve solar energy in 2015 that can be compared to conventional generators. Scientists predict that batteries with more than three knots can theoretically be as efficient as 58%.
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