Researchers gain essential knowledge about the increasing efficiency of solar material

The rows of blue solar panels that punctuate landscapes and roofs are usually made from crystalline silicon, the proven semiconductor of almost any electronic device.

Over the past decade, researchers at Colorado State University have led pioneering studies to improve the performance and cost of solar energy by manufacturing and testing new materials that go beyond silicon capabilities. They focused on a promising material to replace silicon, called cadmium telluride.

In collaboration with partners from the University of Loughborough in the UK, researchers at the CSU's Next Generation Photovoltaics Center, supported by the National Science Foundation, have announced a breakthrough in improving cell performance thin-film solar cadmium telluride through the addition of another material, selenium. Their results were published in the journal Nature Energy earlier this month and is the subject of an article titled "News and Views".

"Our article directly addresses the fundamental understanding of what happens when we go from selenium to cadmium telluride," said Kurt Barth, director of the Next Generation Photovoltaics Center and associate professor of research at the department of mechanical engineering.

Until now, it was not clear why the addition of selenium had a record performance of cadmium telluride solar cells – the ratio of energy production to light input – being only 22 percent. %. In collaboration with CSU, W.S. Sampath and Amit Munshi, Barth and an international team solved this mystery. Their experiments revealed that selenium overcame the effects of atomic scale defects in cadmium telluride crystals, paving the way for more widespread and cheaper solar generated electricity.

The thin films of cadmium telluride that the CSU team uses in the laboratory use 100 times less materials than conventional silicon solar panels. They are therefore easier to manufacture and absorb sunlight at an almost ideal wavelength. The electricity produced by photovoltaic cells made from cadmium telluride represents the lowest cost available in the solar industry because it under-exploits fossil fuel sources in many parts of the world .

According to the document, the electrons generated when sunlight hits the selenium-treated solar panel are less likely to be trapped and lost at the level of defects in the material, located at the boundaries between the crystal grains during their growth. This increases the amount of energy extracted from each solar cell. By working with materials made by CSU via advanced deposition methods, the team discovered this unexpected behavior by measuring the amount of light emitted by panels containing selenium.

Since selenium is not uniformly distributed on the panels, they compared the luminescence emitted by areas where selenium was relatively absent or absent and areas where selenium was highly concentrated.

"A good flawless solar cell material is very effective at emitting light, and therefore highly luminescent," said Tom Fiducia, lead author of the journal and PhD student. student at Loughborough University, working with Professor Michael Walls. "It is striking that data indicating that selenium-rich regions are luminescent are much brighter than pure cadmium telluride and that the effect is remarkably potent."