Researchers from Helmholtz-Zentrum Berlin (HZB) have claimed to have set a new conversion efficiency record of 29.80% in a tandem solar cell made of perovskite and silicon. The result was certified by Fraunhofer ISE CalLab.

The researchers improved upon their earlier conversion efficiency record of 29.15%. They claim the results suggest that the conversion efficiency of perovskite silicon tandem solar cells could be increased to over 30% by nanostructuring the absorber layers on both sides.

“An efficiency of 30% is like a psychological limit for this fascinating new technology. That could revolutionize the photovoltaic industry soon, ”said Steve Albrecht, who examines the perovskite thin films in the HySPRINT innovation lab at HZB.

The researchers examined how nanostructures at different interfaces affect the performance of a tandem solar cell made of a perovskite solar cell on a silicon solar cell. The team used a computer simulation to calculate the photocurrent density in the perovskite and silicon sub-cells for various geometries, with and without nanotextures.

The team then fabricated perovskite-silicon tandem solar cells with various structures. According to the researchers, even one-sided nanotexturing improves light absorption. This configuration enables a higher short-circuit current compared to a flat reference.

The researchers claim it is remarkable that nanotextures also lead to a slight improvement in the electronic quality of the tandem solar cell and a better film formation of the perovskite layers.

They also improved the backside of the cell by using a dielectric reflector which absorbs sunlight more efficiently, leading to a higher photocurrent. The backside of a cell is supposed to reflect the infrared light into the silicon absorber.

In August 2020, researchers at Fraunhofer Institute for Solar Energy Systems ISE had announced a new record efficiency of 25.9% for the III-V/Si tandem solar cell grown directly on silicon.

Mercom had earlier reported that scientists at Helmholtz Zentrum Berlin developed tandem cells that combine two different semiconductors and convert different light spectrum parts into electrical energy. That perovskite CIGS tandem cell had achieved a record efficiency of 24.16%.