European researchers have produced a tandem photovoltaic module from perovskite and copper indium gallium selenide (CIGS) with an efficiency that they say exceeds that of the best devices made from the individual materials.

A conversion efficiency of 17.8% was documented for the small-area stack, measuring 3.76 cm² in area, developed by imec (Belgium), Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (Germany), and Karlsruhe Institute of Technology, (Germany).

Perovskite solar module sits atop the CIGS module.The current record for perovskite modules on this scale is at 15.3%, and the reference CIGS solar module has an efficiency of 15.7%.

Use of two different thin-film materials enables more of the solar spectrum to be harvested, the researchers say. The semitransparent upper perovskite solar module efficiently absorbs the high-energy portion of the solar spectrum, while the lower CIGS layer converts the infrared parts.

In the device concept, both the perovskite top module and the CIGS bottom module feature a monolithic interconnection scheme, using seven and four module cell stripes respectively. The area losses are less than 8% for both technologies and the interconnection can be laser-processed. This should allow industrial scaling to stacked modules of several square meters.