By the end of 2021, teams at HZB (Helmholtz-Zentrum Berlin für Materialien und Energiehad) presented perovskite silicon tandem solar cells with an efficiency close to 30 percent. This value was a world record for eight months, a long time for this hotly contested field of research.
In the journal Nature Nanotechnology, the scientists described how they achieved the new record value over 31% with nanooptical structuring and reflective coatings.
Tandem cells from HZB have already achieved several world records. Recently, in November 2021, HZB research teams achieved a certified efficiency of 29.8 % with a tandem cell made of perovskite and silicon. This was an absolute world record that stood unbeaten at the top for eight months. It was in the summer of 2022 that a Swiss team at EPFL succeeded in surpassing this value.
The HZB teams had worked closely together for the record-breaking tandem cell. After they presented the details in Nature Nanotechnology, the journal also invited them to write a research briefing to summarize their work and give an outlook on future developments.
Prof. Dr. Christiane Becker, who developed the world record cell with the team led by Dr. Bernd Stannowski (silicon bottom cell) and Prof. Dr. Steve Albrecht (perovskite top cell) said, “Our competences complement each other very well.”
Becker’s team introduced a 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,” explained Becker.
In addition, a dielectric buffer layer on the back of the silicon reduces parasitic absorption at near-infrared wavelengths.
At the new record milestone, the researchers assert that customized nanotextures can help to improve perovskite semiconductor materials on diverse levels. These results are not only valuable for tandem solar cells made of perovskite and silicon, but also for perovskite-based light-emitting diodes.
