Solar cells: New efficiency record for thin-film photovoltaics

Researchers at Empa (Swiss Federal Laboratories for Materials Testing and Research) have achieved a new record of 21.4% in the efficiency of thin-film photovoltaics.

Picture: Empa

Solar power can play an important role in the energy transition. In addition to the storage problem, a second challenge is the statics. Many buildings are not designed for area-wide solar cells.

Flexible solar cells, also called thin-film photovoltaics, could be used as thin foils almost everywhere and thus solve the weight problem. However, the efficiency must be high enough to make their use worthwhile.

That’s why the Swiss Federal Laboratories for Materials Testing and Research have been researching for years to optimize efficiency and thus make flexible solar cells competitive. Their new efficiency record is 21.4%. An independent research team from the Frauenhofer Institute for Solar Energy Systems ISE have almost confirmed this value in a practical test with 21.38%. It was also tested that the efficiency was stable after several months.

Of course, the flexible solar modules are nowhere near conventional silicon solar cells, which cannot be bent. According to Empa, their maximum value is currently 26.7%. That doesn’t sound like a particularly large gap. However, these values are worlds apart for research.
The scientists have achieved the current 21.4% with flexible solar cells based on copper indium gallium diselenide (CIGS). They are manufactured using a low-temperature evaporation method on a polymer film. The light-absorbing semiconductor material Cu(In,Ga)Se2 is deposited as an extremely thin film on the foil. This is not new. However, the researchers have succeeded in improving the exact composition of the film as well as the alkali dopants, thus increasing the efficiency.

Empa is working with the Swiss company Flisom to bring the product to market. The company is a spin-off of Empa and ETH Zurich. Together, they want to develop a process for roll-to-roll production of lightweight, flexible solar modules that would be straightforward to use in numerous applications.

Source: Nicole Lücke,, 13.09.2021, 10:20am -> Link

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