As efficiency records collapse and devices become more stable, the race to commercialize high-efficiency perovskite-silicon tandem solar energy products begins in Europe. Valerie Thompson.
The move by an EU-backed consortium of European technical institutes, universities and public bodies involved in perovskite development was the latest sign of solar researchers and industry working together to take perovskite-silicon tandem solar to the next level.
In 2022, Qcells, Enel Green Power, Meyer Burger, and Voltec Solar announced perovskite-silicon tandem initiatives that bring deep process knowledge to the table, including vacuum deposition, interface design, and encapsulation methods.
pv magazine has signed up with all of them, as well as members of the research community and device supply chain, as well as perovskite-silicon tandem pioneer Oxford PV, to ask about perovskite stability progress.
Researchers bring tandem cell assemblies to over 30 percent conversion efficiency in the laboratory, so R&D collaboration with industry is the way forward. There have also been promising stability announcements and breakthroughs in larger devices.
“Industrial interest has increased since the new record achieved by perovskite tandem cells,” says Steve Albrecht, head of the perovskite tandem solar cell department at Germany’s Helmholtz-Zentrum Berlin (HZB). “It’s a global interest. The efficiency is visible, now stability and scalability require more research and development.”
Albrecht points to the perovskite and silicon tandem record of 32.5% efficiency set by HZB in December 2022. In January, the institute announced an additive with promising stability capabilities. “There are more researchers dealing with stability,” he says. “The instability factors are also better understood. More and more information is available. I expect it to continue along these lines.”
Switzerland-based Center Suisse d’Electronique et de Microtechnique (CSEM) and École Polytechnique Fédérale de Lausanne reported a 31.25% efficient perovskite-silicon tandem device in July 2022, highlighting the need to expand the cell and achieve stable lifetime. .
“The challenge is to bring the functional stability of perovskite solar cells closer to the standards achieved by silicon technologies,” says Quentin Jeangros, head of the CSEM group for perovskite materials and devices. “This is key to making perovskite PV competitive in mainstream applications.”
Gianluca Coletti agrees. He is the program manager for PV tandem technology at the Dutch research institute Nederlandse Organisatie voor Toegepast Natuurwetenschapel Onderzoek (TNO) and coordinates the organization’s contribution to the Solliance thin-film solar research consortium. Solliance recently achieved 30.1% efficiency with a four-terminal perovskite-silicon tandem cell.
“New stability results are constantly being reported,” says Coletti. “Reported shelf life was initially shorter than a few minutes. Today, many last 3,000 hours and last outdoors for more than two years. A lot has been learned. Equally important are the breakthroughs made with larger area devices in recent months. More than 26% efficiency in larger devices – for example more than 20 cm2 – reached at least four teams.
“However, as a research community, we are at the point where we need to change gears and focus on technology in order to scale and increase technology readiness. Therefore, long-term stability is one of the most important points. Now that the 30% barrier has been broken, it is time to focus R&D investments on highly reliable devices, and this is better achieved by forming partnerships between industry, research institutes and academia.
The pioneer is Oxford PV. With a new CEO, the Oxford University spinout is ramping up its production line of two-terminal (2T) monolithic perovskite-silicon tandem cells. Its German plant’s progress has been hampered by delays in equipment deliveries, but it is producing M6 disc-shaped tandem solar cells at a stable 27 percent efficiency — rising to 30 percent, according to chief technology officer Chris Case.
“Customers and partners are assembling full-size, 60-cell modules based on cells from our pilot line,” says Case. pv magazine. “A trained and well-known certification agency helps with the certification of a full-size module.”
In Italy, the Green Power renewables department of the energy company Enel is working on 2T perovskite-silicon tandem technology with the French Institut National de l’Énergie Solaire. Production is planned for 2025. In 2022, the partners announced a 24.9% efficient, 9 cm2 devices and in December they reached 25.8%.
“Today, tandem-perovskite-silicon-heterojunction (HJT) solar cells have demonstrated efficiencies of over 30% in small areas,” says Eliano Russo, director of Enel’s 3Sun solar plant in Sicily. “Using an HJT as a base cell has proven to be a very suitable approach to obtain a highly efficient monolithic perovskite-silicon tandem solar cell.”
As for the development of larger, more stable and more reliable devices, Russo adds: “We are working extensively on these aspects so that within a few years we can produce an industrial product with higher performance and reliability.”
Qcells has announced a European perovskite-silicon tandem initiative as part of the recently launched “Pepperoni” project consortium supported by the EU and Swiss governments. Fabian Fertig, Qcells’ global director of research and development for wafers and cells, says the pilot line at the company’s Thalheim plant in Germany is identifying and addressing barriers to entry for tandem solar cells.
“Reliability remains a key challenge for the commercialization of perovskite-silicon tandem solar cells and modules,” says Fertig. “Although significant progress has been made in improving stability and durability, further work is needed to reach a level sufficient to be competitive with existing silicon-based products. 17 European partners are involved in the multi-year Pepperoni project… The benefits of this project will hopefully be felt by the entire European solar industry.”
In France, module manufacturer Voltec Solar is working on perovskite-silicon tandem research together with the Institut Photovoltaïque d’Ile-de-France (IPVF). Their France PV Industrie joint venture is working on four-terminal technology.
“The goal of our project is to achieve at least a 15 percent reduction in levelized cost of energy (LCOE) with this type of tandem panel compared to current silicon panels,” says IPVF CEO Roch Drozdowski-Strehl.
Swiss heterojunction solar manufacturer Meyer Burger recently announced that it is working with local and German research groups to integrate perovskite-tandem technology into its production.
Supply chain development
Swedish equipment and technology business Evolar AB reported last year stability progress with 100 cm2 devices manufactured using its evaporative deposition process.
CEO and co-founder Mats Ljunggren confirms commercial interest in Evolar’s turnkey perovskite cell production line, which is combined with established silicon lines. “Inquiries come from all over the world,” he says. “Our sales team is currently preparing offers for pilot lines, where we will deliver both equipment and services that will help our customers get up.”
Founded in 2019, Evolar markets integrated cell and panel manufacturers and employs approximately 40 people, most of whom are process developers and equipment engineers.
Fluxim, a Swiss developer of characterization and modeling tools for emerging photovoltaics, also has a view on perovskite development. “On the research and development level of both academia and industry, I think Europe has an advantage with many strong research groups and institutions,” says Daniele Braga, the company’s sales manager.
“The next step is to focus on setting up production lines to maintain the current pole position,” says Frank A. Nüesch, Director of Functional Polymers at the Swiss Federal Laboratories for Materials Science and Technology. “Such a move would send signals to the extended value chain, including the chemical industry, to encourage it to work on the synthesis of the high-quality chemicals needed for the perovskite junction.”