01/02/2024
Source: Energy & Management Powernews
Oxford PV and Fraunhofer ISE announce the development of a full-format tandem PV module with a "record efficiency" of 25 percent based on perovskite silicon tandem solar cells.
The Fraunhofer Institute for Solar Energy Systems (ISE) has announced the world's most efficient silicon perovskite tandem solar module in industrial format. A research team used perovskite silicon tandem solar cells from Oxford PV to produce a photovoltaic module with an efficiency of 25 percent and an output of 421 watts on an area of 1.68 square meters. Tandem technology has the potential to achieve significantly higher efficiencies than previous silicon PV modules. This is possible because two PV layers are arranged on top of each other, with the upper one allowing some of the light to pass through.
The scientists used equipment at the Fraunhofer ISE's Module Technology Evaluation Center (Module-TEC), which is already used in mass production, and optimized the processes. The glass-glass PV module from the Oxford PV solar cells could thus also be manufactured in the PV industry. "It is more efficient than any industrial-sized silicon PV module ever built," said Stefan Glunz, Head of Photovoltaics at Fraunhofer ISE.
The perovskite silicon solar cells in M6 format with an efficiency of 26.8 percent were manufactured in small series by Oxford PV, a spin-off from the University of Oxford, at its factory in Brandenburg. Commercial production of the tandem solar cells will begin this year. David Ward, Chief Executive Officer of Oxford PV, said that perovskite silicon tandem cells have a theoretical efficiency potential of over 43 percent compared to less than 30 percent for silicon solar cells.
Low temperature processes developed
As the perovskite layer of the tandem cells is temperature sensitive, the research team developed low temperature processes for the interconnection and encapsulation of the solar cells, which are also particularly gentle on the cells mechanically. "These are suitable for industrial mass production and can be implemented on commercial systems, and current PV module production lines can be easily adapted," explained Achim Kraft, Group Leader for Interconnection Technology at Fraunhofer ISE.
The solar cells were interconnected using conductive bonding. "In the future, we will also test the alternative of soldering the solar cells at low temperatures," Kraft announced. For the measurement, the Fraunhofer ISE calibration laboratory used a new multispectral solar simulator, which can be used to determine the efficiency of tandem PV modules.
Both cell layers must be irradiated by different LED light sources under the exact conditions under which they would also produce electricity in natural sunlight in order to be able to determine the performance of the solar module precisely and reproducibly. As the currently standardized measurement methods are not fully transferable to this new technology, the method used was additionally validated with field measurements.
The project teams from Fraunhofer ISE and Oxford PV are now aiming to obtain certification for the PV module. To this end, intensive tests on long-term stability are already underway in the climate chambers of the PV module test laboratory at Fraunhofer ISE.
Author: Susanne Harmsen
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