ZSW sets 21.7% thin film efficiency record

The world record for thin film solar performance is back in the hands of researchers at Stuttgart’s Centre for Solar Energy and Hydrogen Research (ZSW) after scientists achieved a 21.7% efficiency with a new CIGS solar cell.

The record improves by 0.7% the previous best set by Swedish researchers Midsummer earlier this year, and returns the accolade to ZSW’s researchers, who have broken previous efficiency ceilings in the past.

According to Michael Powalla, ZSW’s head of the photovoltaics division, the 21.7% performance extends CIGS cell’s lead over typical multicrystalline solar cell efficiencies in laboratory conditions by 1.3%.

"Our advances once again confirm the tremendous technological potential of CIGS thin film PV," said Powalla. "The lab data shows that further efficiency improvements will be possible in the years ahead. This could drive down the cost of CIGS technology even more sharply."

As is standard for efficiency testing, the record-setting cell from ZSW had an area of 0.5 cm² and was manufactured via a co-evaporation process that has proven highly reproducible in laboratory conditions. More than 40 cells were produced that topped the 21% mark – an indication that the method is ready to be scaled up to mass production volumes. The results were confirmed by the Fraunhofer Institute for Solar Energy Systems ISE.

"We are accustomed to the solar industry in Baden-Württemberg [Stuttgart’s federal state] setting records, but this world record is something special," said Baden-Württemberg’s minister of finance and economics, Nils Schmid. "The excellent research being done at ZSW is a key prerequisite for innovations like this. The roughly €4 million in basic funding flowing to the ZSW every year from the state is money well spent."

Powalla confirmed that it is likely to be a couple of years yet until this type of cell creation process is co-opted at manufacturing scale. The scientist believes that "17% to 19% is very much possible in the next few years". Currently CIGS cells on the market usually reach no more than 15% efficiency, but costs are coming down rapidly, increasing the likelihood of mass-market higher efficiencies.

ZSW has agreed a joint partnership with Germany’s Manz AG for this new CIGS thin film technology, with the turnkey specialists eager to move the methods out of the laboratory and into the factory. Manz has recently refined its CIGS fab as the company looks to lower CIGS manufacturing costs by as much as 10%.