EU PVSEC: More stable perovskites remain a candidate for silicon tandem cells

Share on facebook
Facebook
Share on twitter
Twitter
Share on linkedin
LinkedIn
Share on reddit
Reddit
Share on email
Email
Within just a few years, the efficiency of Perovskite solar cells has skyrocketed.

Research on perovskite solar cells has made progress, but there is still a long way to go for a highly efficient tandem with a conventional crystalline silicon cell.

At the European Photovoltaic Solar Energy Conference (EU PVSEC) in Munich last week, the PV-Lab at the Institute of Microengineering (IMT) in Neuchâtel, Switzerland presented a 1.4 cm² small, monolithically stacked silicon-perovskite tandem cell with an efficiency of 20.5%, a significant increase over the 16% value for a monolithic tandem that IMT showed at the previous EU PVSEC in Hamburg last September.

Within just a few years, the efficiency of Perovskite solar cells has skyrocketed; the record for a lab cell is currently held by a group at the Korean Research Institute of Chemical Technology with 22.1%.

Perovskite is an organic-inorganic compound; usually, methylammonium lead iodide is used for solar cells. Its bandgap of 1.56 eV is close to the ideal value of 1.7 eV for the top cell in a tandem with a wafer-based silicon cell in order to capture that part of the light spectrum that the silicon cell cannot absorb.

If the top and bottom cells are not monolithically stacked, but only optically coupled and efficiency is measured by four terminals, the potential of such a tandem becomes clear: Christophe Ballif, director of the PV-Lab at IMT and Vice President Photovoltaics at the Centre Suisse d'Electronique et de Microtechnique (CSEM), presented a tandem efficiency of 25.2% for a 0.25 cm² small perovskite cell on top of a silicon heterojunction cell. With further improvements, Ballif believes that 27 to 28% can be achieved.

The challenge, however, lies in upscaling perovskite cells to larger areas. A mini-module with an aperture area of 168 cm², produced by the Dutch-Belgian-German thin-film PV research consortium Solliance, has reached an efficiency of 10.0% – still far away from the record efficiencies of lab cells.

Another issue remains the long-term stability of perovskites. A Swiss research group at the École Polytechnique Fédérale de Lausanne (EPFL) has achieved some improvement here, as Anders Hagfeldt, head of the EPFL Laboratory of Photomolecular Science, reported at the EU PVSEC. By adding small amounts of inorganic cesium, the researchers could stabilize the efficiency of a perovskite cell for 250 hours at room temperature. 

At 75°C, however, gold from the contact diffused into the cell and the efficiency degraded. Although an additional interface layer of chromium was able to prevent this effect, Hagfeldt admitted: “The stability of silicon is a challenge for perovskites.”

Read Next

PV Tech Premium
April 12, 2021
Mark Osborne details how Solar Module Super League (SMSL) major JinkoSolar is transforming its manufacturing base, moving from an asset-lite model to one more vertically integrated.
March 12, 2021
LONGi Solar is planning to build a new 5GW high-efficiency monocrystalline solar cell plant in Yinchuan, China.
March 3, 2021
Major polysilicon and solar cell producer Tongwei Group has begun ramping the final cell lines at its 15GW Meishen production hub in Sichuan Province, with the facility now the largest single site for solar production in the world.
February 2, 2021
Large-wafer size producer Tianjin Zhonghuan Semiconductor (TZS) is to build a new 50GW 210mm (G12) mono-wafer manufacturing hub in Ningxia Hui Autonomous Region at a cost of around RMB12 Billion (US$1.86 billion).
February 2, 2021
The solar industry's two largest enterprises, GCL and LONGi have signed a major polysilicon supply deal, the first time the rivals have entered into a major business deal together.
February 1, 2021
Panasonic has announced plans to withdraw from manufacturing heterojunction (HJT) cells and modules with the closure of its manufacturing plants in Malaysia and Shimane Prefecture, Japan.

Subscribe to Newsletter

Upcoming Events

Solar Media Events
April 20, 2021
Upcoming Webinars
April 28, 2021
4:00 - 4:30 PM CET
Solar Media Events
May 11, 2021