While the sunlight-to-electricity conversion efficiency of most solar power arrays used for residential construction hovers in the 20% range, researchers over the past four years have found ways to boost that number in the lab, although the technology hasn’t quite found its way into large-scale production.
In December 2006, for example, Boeing Company subsidiary Spectrolab announced that it had produced a “multijunction” solar cell – constructed of multiple thin films, each designed to capture a certain section of the solar spectrum – that is able to convert 40.7% of the sun’s energy into electricity. Seven months later, a consortium led by researchers at the University of Delaware created a silicon solar cell platform that achieved 42.8% efficiency, and in October last year, Sharp Corporation announced it had achieved 35.8% conversion efficiency with a triple-junction solar cell whose construction features three photo-absorption layers consisting of elements other than silicon.
The latest development in this power quest is a solar cell proposed by researchers at Stanford University that would use materials other than silicon to not only convert photons to electricity but also enhance the cell’s power production by harnessing the thermal energy of sunlight. The concept, called Photon Enhanced Thermionic Emission, basically turns waste heat – one of the things that, as it increases above room temperature, reduces the performance of silicon solar arrays – into a force for greater conversion efficiency. Reporting on their work in the August 1 edition of Nature Materials, the researchers say the solar devices they plan to develop using this technology are expected push conversion efficiencies above 50%.
In a brief about the research paper, website DailyTech noted that the solar cell is expected to consist of gallium-based photovoltaic surfaces, with a thin coating of cesium to enable the device to harvest electricity from what would otherwise be waste heat. Peak efficiency for the device, in fact, would be above 200 degrees Celsius, well in excess of the 100 degrees Celsius that renders silicon solar cells inert, DailyTech notes.
If the device does indeed move from theory to reality, and then can be manufactured cost-effectively, it could be a major game changer.
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