25.5% Efficiency For Perovskite-Si Tandem PV Cells

• A research team at Germany's HZB research center has achieved 25.5% power conversion efficiency for perovskite silicon tandem solar cells
• They were able to achieve this conversion ratio by applying a polymer light management foil to the front side of an efficient perovskite silicon tandem solar cell with a silicon layer etched on the back-side
• Using LM foil on the front-side of the cell can be immensely useful in building integrated PV that can be utilized for new areas of energy generation from large sky scraper facades, HZB said

A team of researchers at the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) research centre in Germany, say they have achieved 25.5% efficiency for perovskite-silicon tandem solar cells, which they claim is the highest published value till date. The study has been published in the journal, Energy and Environmental Science.

To reduce the reflection and allow the solar cell to capture more light, the HZB physicist Steve Albrecht led team fabricated an efficient perovskite/silicon tandem device with a silicon layer etched on the back-side. They then applied a polymer light management (LM) foil to the front side of the device, thus enabling processing of a high-quality perovskite film on a flat surface, while benefiting from the front-side texture.

"In this way, we succeeded in considerably improving the efficiency of a monolithic perovskite-silicon heterojunction tandem cell from 23.4 % to 25.5 %," said Marko Jošt, first author of the study and postdoctoral fellow in Albrecht's team.

Team leader Steve Albrecht believes the LM foil on the front-side of the solar cell device is particularly advantageous under diffuse light irradiation, and not only under perpendicularly incident light. Tandem solar cells with the new LM foil could be useful in building-integrated PV (BIPV), that throws open possibilities for huge new areas of energy generation from large sky scraper facades.

A sophisticated numerical model for complex 3D features and their interaction with light prepared by the team indicates that an efficiency of 32.5% can be achieved realistically "if we succeed to incorporate high quality perovskites with a band gap of 1.66 eV," added Jošt.

In July 2018, Belgian research institute Imec achieved 27.1% power conversion efficiency for a 4-terminal perovskite/silicon tandem PV cell (see 27.1% Perovskite/Si Tandem Cell From IMEC). In the same month, EPFL and CSEM scientists achieved a 25.2% record efficiency for a tandem solar cell based on silicon and perovskite (see 25.5% Record For Si-Perovskite Cell).