A research team at the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (Helmholtz Center for Materials and Energy, HZB) has developed a »simple, robust fabrication process« for tandem solar cells based on perovskites and CIGS (copper indium gallium selenide), »that is also suitable for scaling up to large surface areas«. The efficiency achieved here is relatively low at 21.6 percent. Comparable concepts from other institutes achieve well over 24 percent, but currently only on areas up to 0.5 square centimeters that are irrelevant for mass production.
However, even the HZB process is only 0.8 square centimetres in size for the time being. According to Rutger Schlatmann, Director of the HZB Institute PvcomB, an important characteristic is that »this tandem cell was fabricated on a rough, untreated CIGS bottom cell, which simplifies manufacture and represents an enormous advantage in terms of mass production«. Moreover, possible efficiencies would reach 30 percent and higher.
The next step will now be the certification of the efficiency by an independent institution. For recognition as a record, however, the value would have to be achieved on an area of at least one square centimetre.