The rows of blue solar modules that dot landscapes and roofs are typically made of crystalline silicon, the workhorse in virtually every electronic device.
In solar technology, cadmium telluride could replace the silicon.
Over the past decade, Colorado State University (CSU) researchers have pioneered studies to improve the performance and cost of solar energy by producing and testing new materials that go beyond the capabilities of silicon. They have focused on a material that is promising to replace silicon: cadmium telluride.
In collaboration with colleagues from Loughborough University in Great Britain, researchers from the CSU's Next Generation Photovoltaics Center have achieved a decisive breakthrough on how the performance of cadmium telluride thin-film solar cells can be further improved by adding selenium.
The research results were published in the journal "Nature Energy".
"Our report goes as far as a fundamental understanding of what happens when we alloy selenium to form cadmium telluride," said Kurt Barth, director of the Next Generation Photovoltaics Center and associate professor in the Department of Mechanical Engineering.
So far, it has not been clear why the addition of selenium has achieved a record-breaking cadmium telluride solar cell efficiency of well over 22 percent.
Together with CSU employees WS Sampath and Amit Munshi, Barth and an international team have solved this mystery. Their experiments showed that selenium overcomes the effects of atomic defects in cadmium telluride crystals, opening a new path for widespread, cheaper solar power.
The cadmium telluride thin films produced by the CSU team in the lab use 100 less material than conventional silicon solar cells.
They are therefore easier to manufacture and absorb sunlight at almost ideal wavelength. The electricity generated by cadmium telluride photovoltaic cells is the most cost-effective in the solar industry and undercuts fossil fuels in many parts of the world.
According to the report, it is less likely for electrons that are generated when sunlight strikes the bleached solar panel to be trapped and lost in the material's defects.
These defects arise during growth at the boundaries between the crystal grains. This increases the amount of energy gained from each solar cell.
Working with the materials produced at the CSU using advanced deposition methods, the team discovered this unexpected behavior when it registered how much light is emitted from selenium-containing solar modules.
Because selenium is not evenly distributed throughout the modules, they compared the luminescence from areas that had little or no selenium to areas where the selenium was very concentrated.
"Good and faultless solar cell material is very efficient in terms of light emission and therefore luminescence," said Tom Fiducia, lead author of the research report and PhD student at the University of Loughborough - in collaboration with Professor Michael Walls.
“It is strikingly clear when you see from the data that regions rich in selenium shine much brighter than pure cadmium telluride. The effect is remarkably strong. "
Since 2009 the National Science Foundation has supported the work of the “Next Generation Photovoltaics Center”.
Source: Electronics Information
