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.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.

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