Fraunhofer ISE hits 22.3% efficiency for III-V/Si tandem cell

© Fraunhofer ISE/ A. Wekkeli

January 8 (Renewables Now) - The Fraunhofer Institute for Solar Energy Systems ISE (Fraunhofer ISE) on Monday announced an efficiency record of 22.3% for a multi-junction solar cell, in which III-V semiconductors were directly grown on the silicon.

The result has been achieved as part of the MehrSi project, in which scientists at Fraunhofer ISE partner with the Technische Universität Ilmenau (TU Ilmenau), the Philipps University of Marburg and technology company AIXTRON SE.

According to researchers in the solar field, combining different semiconductor materials is one way to surpass the theoretical solar efficiency limit of 29.4% for single-junction silicon photovoltaic (PV) cells. Over more than a decade, scientists have been trying to grow III-V layers directly on the silicon solar cell, thus reducing the costs associated with the use of expensive III-V substrates.

Fraunhofer ISE announced that the team has succeeded in that task, greatly reducing the defect density in the III-V semiconductor layers on the silicon, and has thus produced a III-V/Si tandem solar cell with 22.3% efficiency.

Andreas Bett, institute director of Fraunhofer ISE, noted that a new research centre for high efficiency PV cells is being built in Freiburg and that work on tandem cells will continue there upon its completion in 2020. “With the improved technical infrastructure, we expect the developments in multi-junction solar cells based on silicon to accelerate rapidly,” Bett said.

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