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A New benchmark for efficiency of flexible thin-film solar cells

Never before has such an efficient flexible CIGS solar cell been built. Empa researchers achieve an efficiency of 21.4% – breaking their own record. So far, the best efficiency of a non-flexible solar cell made of crystalline silicon is reported at 26.7 percent.

Empa a Switzerland based Laboratory for Thin Films and Photovoltaics is an apex research facility for the development of high-performance thin film solar cells, batteries and opto-electronic devices and applications for affordable energy-sustainable future





The Empa Laboratory for Thin Films and Photovoltaics, headed by Ayodhya N. Tiwari, has broken its own record. The researchers improved the efficiency of energy conversion in CIGS solar cells on flexible polymer substrate to 21.4%. This is 2.88% higher than the previous mark (20.8%) - which is held by the same group. The technology of choice is copper indium gallium diselenide (Cu(In,Ga)Se2) or CIGS, which enables the manufacture of flexible, lightweight solar cells on polymer films. The details of the research achievement were presented at the 38th European Photovoltaic Solar Energy and Conference and Exhibition (EU PVSEC) on 7 September 2021 by Romain Carron, group leader in the Laboratory for Thin Films and Photovoltaics headed by Ayodhya N. Tiwari. The solar cell efficiency of 21.38 percent was independently measured at Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany.

Secret behind the CIGS Solar Cell feat..

The achievement of this new benchmark for efficiency of flexible thin-film solar cells is the result of three major combined improvements, explains Romain Carron, head of CIGS research at Empa's laboratory. "First, we have carefully adjusted the chemical composition of the absorber layer to improve its electronic and optical properties. Then we developed new methods for alkali metal doping. And finally, we have adapted the properties of the absorber-buffer interface to improve cell performance." In particular, Shiro Nishiwaki's meticulous work was essential to improve the performance of the cells, says Carron.



Flexible CIGS solar modules are already commercially available, in particular from the Empa spin-off Flisom, which was co-founded by Tiwari. "Such high efficiency as we have now achieved in our laboratory demonstrates the potential of the technology. Future developments will be aimed in particular at transferring our new process from laboratory to industrial scale in order to increase the power generation and profitability of photovoltaic systems," says Tiwari.



22 years of Research & Setting new benchmarks consistently..

Empa has been engaged in doing pioneering research on flexible solar cell for more than 22 years. With all the know how of the technology and rudimentary processes, it has set and breached its own benchmarks for efficiency of flexible thin-film solar cells many times . First It achieved 12.8 percent benchmark in 1999, which was pushed to 14.1 percent in 2005, 17.6 percent in 2010, 18.7 percent in 2011, 20.4 percent in 2013 and 20.8 percent in 2019.


Flexible thin film solar modules can be used on existing roofs and facades of buildings, farms, industrial structure, surface transport to water transport to air transport and consumer electronics. They are less invasive and bit eco friendly for installation.


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