Perovskite Photovoltaics Scaling Gap Closed and Efficiency Exceeds 24 Percent

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Perovskite solar cells achieve excellent efficiencies in the laboratory, but industrial production has struggled with scalability. Researchers at KIT now present a vacuum process that increases efficiencies: 24.4 percent for single cells and 23.5 percent for tandem modules.

The efficiency of perovskite solar cells is already excellent in the laboratory, but industrial production has so far lacked scalability. KIT researchers are now presenting a vacuum process that paves the way for the highly efficient mass production of tandem solar cells. This could also revolutionize energy harvesting for IoT applications.

Photovoltaics will play a central role in the power supply of the future. While silicon-based PV technology is slowly reaching its physical limits, perovskite solar cells promise efficiencies of well over 30 percent - provided they are used as tandem cells (perovskite combined with silicon or as pure perovskite tandems).

The problem so far: most record efficiencies have been achieved on fingernail-sized samples in the laboratory, mostly using wet chemical processes (spin coating), which are hardly suitable for precise mass production on large surfaces.

Co-Evaporation in a Vacuum

A team led by Dr. Tobias Abzieher and Professor Ulrich W. Paetzold from the Karlsruhe Institute of Technology (KIT) has now made decisive progress. They are relying on co-evaporation (co-evaporation) in a high vacuum.

"The vacuum process has decisive advantages over wet chemical processing for industrial production," explains Tobias Abzieher. "Layer deposition can be controlled much more precisely, dries faster and can be seamlessly integrated into existing semiconductor and OLED production processes."

The Values in Detail

The results obtained at KIT show that the industrial vacuum process hardly requires any compromises in terms of efficiency compared to the laboratory standard:

• Single solar cells: An efficiency of 24.4 percent was achieved here. This is a peak value for perovskite cells, which were produced purely by physical vapor deposition.
• Perovskite-perovskite tandem modules: On an aperture area of approx. 12.25 cm², the researchers achieved an efficiency of 23.5 percent
• Scalability: Maintaining quality at module level is particularly important. Laser interconnection of the cells to form modules means that losses can be kept to a minimum.

Relevance for the Power Supply

For developers of power supply solutions, the industrial maturity of perovskites means two things in particular: falling costs per watt peak and new design freedom. As perovskite layers are extremely thin and potentially flexible, they open up applications beyond classic rigid glass modules.

KIT is already working with industrial partners to transfer the process to square meter-sized modules. "Our goal is to bring highly efficient tandem photovoltaics out of the laboratory and into real-life applications - using processes that are economically competitive," says Ulrich W. Paetzold.

The results underline the fact that perovskite technology has finally left its academic status and is maturing into a serious pillar of industrial energy supply. (heh)