Researchers at the Swiss Federal Laboratories for Materials Science and Technology (Empa) report that they have created an 11.5% efficient flexible cadmium telluride (CdTe) thin film solar photovoltaic (PV) cell using copper doping.
Previously achieved flexible CdTe efficiencies were below 8%. The new record was achieved using high-vacuum copper evaporation onto the CdTe layer followed by a heat treatment to allow the copper atoms to penetrate the CdTe layer.
“People have tried to dope CdTe cells in substrate configuration before but failed time and again”, noted Ayodhya Nath Tiwari, head of Empa’s laboratory for Thin Films and Photovoltaics.
Empa says that the process was improved by fine-tuning the amount of evaporation to allow a monolithic copper layer to be deposited on the CdTe. Through this method the team achieved a 13.6% efficiency for CdTe on glass, well below current records, but an 11.5% efficiency on metal foil.
Flexible thin-film CdTe offers multiple cost advantages
Empa notes that flexible thin film PV requires a minimum amount of materials and can be manufactured in large quantities by roll-to-roll processing, and also that CdTe is a low-cost PV technology.
The team believes that there is an opportunity to improve efficiencies further in the future, and has set a short-term goal to reach 15% efficiency. Researchers have stated that they believe that the material has the potential for efficiencies above 20%, which is around the current world record for both dominant thin-film PV technologies, CdTe and copper indium gallium diselenide (CIGS).