Helmholtz Center achieves 21.6% for perovskite CIGS tandem solar cell

From pv magazine Germany.

Scientists at the Helmholtz Center Berlin (HZB) claim to have produced a thin-film solar cell made of perovskite and copper-indium-gallium-selenide (CIGS) with an efficiency of 21.6%.

The achievement is not a record, as the Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) and Belgium’s Nanoelectronics Research Center (Imec) reported a 24.6% efficiency in November.

The HZB researchers said they used a simple, robust production process suitable for scaling up. Rutger Schlatmann, director of the HZB’s Institute PVcomB, spoke of an “enormous step in the direction of commercial production”. The HZB team’s tandem cell could theoretically reach an efficiency of more than 30%, claim the researchers.

The Helmholtz group applied an ultra-thin, conformal intermediate layer to the CIGSe layer, then spun-coated the perovskite layer onto it at the HZB’s HySPRINT lab. In cooperation with the Eindhoven University of Technology, the HZB researchers realized their tandem cell on an area of ​​0.8 cm².

Certification aim

“Record values are only recognized for areas of 1 cm² or more, yet our cell area is just slightly below this threshold,” said Steve Albrecht, co-author of a paper about the research. “Therefore, we now focus [on certifying] this tandem solar cell efficiency and its enormous performance, [through] an independent institution.”

Tandem solar cells consist of two semiconductors with different band gaps. As a result, they can use a larger share of the solar spectrum for power generation. Perovskites convert blue, high-energy components of light, while CIGS or silicon do the same with red and near-infrared parts of the spectrum.

Last week, European solar research organization Solliance announced it had achieved 21.5% efficiency for a flexible CIGS tandem solar cell based on perovskite.