A cadmium-free small-area CIGS solar cell created by the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) and its partner, Manz, possesses a conversion efficiency of 21%, as verified by Fraunhofer ISE, according to a recent press release.
The 21% conversion efficiency marks a new record for cadmium-free solar cells in this surface area category — but not for CIGS solar cells overall, where ZSW holds the current record (21.7%), and Solexel holds the current record for concentrator CIGS solar cells (23.3%).
The new record-breaking CIGS cells make use of an architecture incorporating intermediate films (buffer layer) of zinc oxysulfide (front contact) and zinc magnesium oxide — which are deposited, rather than cadmium sulfide and zinc oxide buffer layers, via a chemical bath.
“First and foremost, the buffer layer transmits more light without the cadmium sulphide,” stated Professor Michael Powalla, a ZSW board member and the head of the center’s solar photovoltaics division. “In theory, we could use it to achieve even higher efficiency than with previous CIGS cells. The alternative buffer layer and the cadmium sulfide buffer are both deposited in a chemical bath, so a transition to manufacturing is possible without requiring additional processes.”
The achievement of the new record means that ZSW once again holds the top spot for the category, taking it back from the Japanese.
As mentioned above, ZSW also currently holds the record for highest conversion efficiency in a (non concentrator) CIGS solar cell. That record of 21.7% conversion efficiency was actually only achieved pretty recently, just last fall — beating out the earlier record held by the Fraunhofer Institute for Solar Energy Systems by 0.7%.
For more on solar cell efficiency records, check out: Which Solar Panels Are Most Efficient?
Image Credit: ZSW