Flexible solar cells: Efficiency improved again
Empa reports a new record for the efficiency of flexible solar cells: Once again, a value of 22.2% was achieved for flexible CIGS solar cells on plastic films. Such flexible solar cells are particularly suitable for applications on buildings, vehicles, satellites, airships and mobile devices.
Empa researchers have again improved the efficiency of flexible CIGS solar cells. Already last year a record could be reported. Independently certified measurements now showed a value of 22.2% in the conversion of light into electricity, which is an improvement on the previous record value of 21.4%. By comparison, the maximum efficiency of a rigid crystalline silicon solar cell is 26.7%. The team led by Romain Carron, group leader in Empa's Thin Films and Photovoltaics Laboratory under Ayodhya N. Tiwari, presented their latest results at the "8th World Conference on Photovoltaic Energy Conversion" (WCPEC-8) in Milan on September 26, 2022.
Thin semiconductor layer optimized again
The flexible solar cells are processed on a polymer film with a light-absorbing semiconductor layer consisting of a copper-indium-gadolinium-selenium compound. This mineral layer is deposited by a low-temperature co-evaporation process. Empa scientist Shiro Nishiwaki changed the composition of the layer to improve the performance and output voltage of the cells. "Two different approaches to alloying the crystal led to similar improvements in device performance," says Romain Carron. Therefore, the results can be transferred to an industrial scale in different ways, but with equivalent results. The solar cell's efficiency of 22.2% was independently confirmed at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany.
Flexible solar cells: An area of research since 1999
Ayodhya Tiwari and his team have been researching flexible thin-film solar cells for more than 23 years. They have set several efficiency records over the years. Their "record streak" started in 1999 with an efficiency of 12.8%, then went on to 14.1% (2005), 17.6% (2010), 18.7% (2011) and 20.4 %(2013), and finally reached 20.8% in 2019 and 21.4% in 2021. However, given the already very high efficiencies, any increase, no matter how small, will require careful study of the factors limiting energy conversion and innovative approaches to address them, according to the statement. The current increase in efficiency is due to the alloying of the light-absorbing semiconductor layer, whose electronic properties have been improved.
Wide range of applications
Flexible and lightweight solar modules with this technology are particularly suitable for applications on roofs and facades of buildings, on greenhouses, vehicles and airships, and for portable electronics. Empa is working with the Swiss company Flisom on roll-to-roll production of lightweight, flexible solar modules for such applications. The research was supported by the Swiss Federal Office of Energy (SFOE).
Source: Empa
