Helmholtz Center achieves 29.80% efficiency for perovskite/silicon tandem solar cell

Scientists at the Helmholtz Center Berlin (HZB) claim to have produced a perovskite/silicon tandem solar cell with a world record efficiency of 29.80%.

The result, which has been certified by Germany’s Fraunhofer Institute for Solar Energy Systems’ (ISE) CalLab, was also included in the charts of the U.S. Department of Energy’s National Renewable Energy Laboratory. It improves upon the previous world record achieved by perovskite developer Oxford PV in December 2020, when the U.K.-based company announced a power conversion efficiency of 29.52% for its perovskite/silicon tandem device.

The solar cell has an area of 1cm² and is based on a nanotextured front side and a back side with a dielectric reflector, which is used to reflect infrared light back into the silicon absorber.

The nanotexturing on one side, according to the researchers, is not only responsible for improving light absorption and photocurrent, compared to a reference solar cell without the nanotextures, but it also, surprisingly, improved, slightly, the electronic quality of the tandem device and enabled better film formation of the perovskite layers.

“By using a dielectric reflector, we were able to use this part of the sunlight more efficiently, resulting in a higher photocurrent,” said HZB researcher Alexandros Cruz Bournazou, noting that the efficiency of the solar cell may soon exceed the 30% threshold, through nanostructuring the absorber layers on both sides.

All the technical details on the solar cell can be found in the paper Monolithic perovskite/silicon tandem solar cell with >29% efficiency by enhanced hole extraction, which was published in Energy in December 2020, when the same research team achieved an efficiency of 29.15%.