Tandem solar cells made of perovskite and silicon enable significantly higher efficiencies than silicon solar cells alone.

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.

Nanotextured PSTSC design a–c, SEM cross-section micrographs of the front and rear side of planar (a), nanotextured (b) and nanotextured + RDBL (c) PSTSCs. c-Si, crystalline silicon. Image Credit: © P. Tockhorn, Helmholtz-Zentrum Berlin für Materialien und Energiehad. More images at both the press release and study paper links.

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 not until 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, in which they 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.


In the Nature Nanotechnology paper the team is saying they’ve clear 31% efficiency. For those watching clearing the 30% mark is a milestone. Congratulations are in order! The light management the team has accomplished will have an impact on consumer products over time. The prime question being, “What the cost will be at industrial scale to build panels?” with the exactness the team is showing in the lab studies.

This is good work, as every photon has to pay for solar to stay in the energy business, and even then the competition is going to be fierce.

There are hard questions to come. They’ll be about production costs, environmental concern about building and recycling, lifespan and all the others, too.

But over 30% is a high efficiency and that gives enthusiasts cause for confidence.


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