Corrugations boost perovskite performance
HZB teams publish details of record-breaking perovskite tandem solar cells with periodic nanotextures
In November 2021, three research teams from Helmholtz-Zentrum Berlin (HZB) achieved a record-breaking certified efficiency of 29.8 percent with a tandem cell made of perovskite and silicon. The record stood unbeaten for eight months, until this summer a Swiss team at EPFL surpassed the value.
The HZB researchers have now presented the details of the technology in Nature Nanotechnology, describing how using corrugations or 'periodic nanotextures' provided performance advantages without compromising the material quality of the solution-processed perovskite layers.
"Our competences complement each other very well," says Christiane Becker, who developed the world record cell with the team led by Bernd Stannowski (silicon bottom cell) and Steve Albrecht (perovskite top cell). Becker's team introduced the nanooptical structure into the tandem cell: a gently corrugated nanotexture on the silicon surface. "Most surprising, this texture brings several advantages at once: it reduces reflection losses and ensures a more regular perovskite film formation," says Becker. In addition, a dielectric buffer layer on the back of the silicon reduces parasitic absorption at near-infrared wavelengths.
The researchers believe that customised nanotextures can help to improve perovskite semiconductor materials on diverse levels not only for tandem solar cells made of perovskite and silicon, but also for perovskite-based LEDs.
Pictured above: Scanning electron microscopy of perovskite silicon tandem cells in cross-section: a) planar, b) with corrugated nanotexture, c) with nanotexture and back-reflector layer (golden).
'Nano-optical designs for high-efficiency monolithic perovskite–silicon tandem solar cells' by Philipp Tockhorn et al; Nature Nanotechnology (2022)