Researchers at the Heimholtz Zentrum Berlin (HZB) have developed a tandem solar cell that converts 32.5% of the sun’s radiation into electricity, a new world record for this type of technology, according to certifying institute European Solar Test Installation (ESTI) in Italy.

The system consists of a silicon bottom cell and a perovskite top cell. Tandem devices outstrip other technologies in efficiency by stacking cell layers with different materials on top of each other to harvest a larger part of the light spectrum.

HZB with the new cell exceeds its previous record of a 29.8% efficiency with a tandem cell from last year, and that of a Switzerland’s Ecole Polytechnique Fédérale de Lausanne (EPFL), which had reached an efficiency of 31.3% earlier this year with a similar technology.

"This is a really big leap forward that we didn't foresee a few months ago,” said Steve Albrecht, a leading researcher on tandem cells at HZB.

While the nearly one third efficiency was reached under laboratory circumstances, the break-through is particularly relevant as HZB is one of several research institutions collaborating with Swiss manufacturer Meyer Burger, which aims to produce 30%-plus efficiency solar cells on an industrial scale.

By pushing efficiencies higher with the latest technologies, Meyer Burger wants to beat much larger Chinese competitors, whose products are usually quite cheap, but are based on cell technologies, for example PERC, that reach efficiencies of around 23% in commercial use or around 25-26% in a laboratory environment, such as TOPCon or heterojunction – a technology also being advanced by Meyer Burger.

Harvesting a larger share of the sun’s radiation could give European solar cell and panel makers a competitive edge over producers from Asia, which can count on a domestic mass market, cheap state finance and low labour costs.

Meyer Burger is one of several companies attempting a solar manufacturing revival in Europe after cheap Chinese competition a decade ago had nearly killed the once-mighty sector – with the EU-backed European Solar Initiative aiming to see at least 20GW of PV manufacturing back in the EU by 2025.

There is definitely rising demand for solar cells and panels in Europe, with solar power capacity additions in the EU having jumped by nearly half this year to a staggering 41.1GW.

“We are very excited about the new value as it shows that the perovskite/silicon tandem technology is highly promising for contributing to a sustainable energy supply," Albrecht said.

HZB's scientific director Bernd Rech added: "At 32.5%, the solar cell efficiency of the HZB tandems is now in ranges previously only achieved by expensive III/V semiconductors [built with stacked sub-cells and based on costly materials such as gallium-indium-phosphide].”

To achieve the new record, researchers used an advanced perovskite composition with what HZB calls a very smart interface modification.

The lead authors in Albrecht’s team – Silvia Mariotti and Eike Köhnen – developed an interface modification to reduce charge carrier recombination losses and applied detailed analysis to understand the specific properties of the interface modification.

These developments were then successfully implemented in tandem solar cells, combined with further optical improvements, the research institute said.