European researchers achieve 17.8 percent perovskite/CIGS mini module

A collaborative research team from the Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (Centre for Solar Energy and Hydrogen Research, ZSW), Karlsruhe Institute of Technology (KIT) and Belgium’s imec has successfully produced a 3.76cm2 PV module; that deploys semi-transparent perovskite layer on top of a copper indium gallium selenide (CIGS) cell. The project’s findings and resulting efficiency record of 17.8% were presented today at the PSCO-2016 conference in Genoa, Italy, today.

The perovskite/CIGS photovoltaic stack produced by the researchers harvests the higher energy light spectrum with the semi-transparent perovskite top layer, while the CIGS bottom layer harvests the light with lower energy.

The resulting PV stack’s efficiency of 17.8% surpasses efficiency records for "upscaled" research modules deploying both perovskites, with 15.5% achieved by imec, and CIGS, with the 15.7% record held by ZSW.

The research consortium couples the KIT’s Helmholtz Young Investigator group’s work on perovskite multi-junction cells, along with the ZSW’s expertise in CIGS, and imec’s perovskite know-how.

Ulrich Paetzold, head of the research group at KIT, said that the efficiency result "is just a starting point," and that perovskite/CIGS stack module efficiencies could exceed 25% "in the next years." Paetzold’s group is focusing on the optics of perovskite multi-junction solar modules.

A researcher team from Switzerland and Germany have previously achieved an 18% perovskite/heterojunction PV cell.

While the record-setting module is far from being at commercial scale, the researchers report that it is a "fully scalable device concept," for both the perovskite and CIGS layer. The module is produced using a "monolithic interconnection scheme," indicating that it is suitable for contemporary mass production techniques, with a resulting area loss of less than 7% for both technologies.

“This success is an elegant way of combining the advantages of two highly advanced thin-film technologies," said ZSW’s Michael Powalla. "It will contribute greatly to ever more cost-efficient solar power for the customer.”

While the 17.8% efficiency achievement on a reasonably-sized research module is, without a doubt, a positive development, the research teams have not addressed the perovskite stability in their media release announcing the result. While perovskites have shown stunning increases in conversion efficiencies in recent years, the stability of the semiconductor material is thought to be a major hurdle yet to have been overcome: Stable perovskites tend to exhibit low conversion efficiency, and high-efficiency perovskites are frequently unstable.