Researchers Solve Scientific Puzzle That Could Improve Solar Panel Efficiency

New solar panels created from a semiconducting material called cadmium telluride (CdTe) 'have been found to produce electricity at lower costs than silicon panels and there has been a dramatic gain in efficiency brought about by adding an element called selenium to the cadmium telluride,' reports Phys.Org. 'Until now, it was not well understood why selenium increases efficiency but thanks to Tom Fiducia, a Ph.D. Research Student in the Center for Renewable Energy Systems Technology (CREST), and an international team of researchers, the puzzle has been solved.' From the report: Their paper, titled 'Understanding the role of selenium in defect passivation for highly efficient selenium-alloyed cadmium telluride solar cells,' has revealed that selenium works by overcoming the effect of harmful, atomic-scale defects in CdTe panels. This explains the increase of efficiency as electrons (subatomic particles that carry electricity), which are generated when sunlight hits the solar panel, are less likely to be trapped and lost at the defects. This increases the amount of power extracted.

Tom, who is the lead author of the paper, says the team discovered this 'unexpected' behavior by measuring how much light is emitted from selenium-containing panels. As selenium is not evenly distributed across the panels, they compared the 'luminescence' emitted from areas where there was little-to-no selenium present and areas where the selenium was very concentrated. Tom explained: 'While it seems counter intuitive, good solar cell material that is defect-free is very efficient at emitting light, and so luminesces strongly. We mapped the luminescence emitted from a selenium-containing solar cell at a resolution of around 1/10,000th of a millimeter and compared it to a similarly high-resolution map of the selenium concentration taken on the exact same area of the cell. It is strikingly obvious when you see the data that selenium-rich regions luminesce much more brightly than the pure cadmium telluride, and the effect is remarkably strong.' The new-found knowledge could be used to increase the efficiency of cadmium telluride solar panels even further, says Tom. 'For instance, this could be by simply increasing the amount of selenium in the devices or altering its distributions within the cell.'

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