Australian uni reaches 34.5% efficiency with 4-junction mini-module

Researchers at the University of New South Wales (UNSW) have hit 34.5% efficiency with a 28-sq-cm four-junction mini-module and said yesterday that scaling it up to a 800-sq-cm device “is well within reach”.

The team at the Australian Centre for Advanced Photovoltaics (ACAP) combined a silicon cell on one face of a glass prism, with a triple-junction solar cell on the other. The triple-junction cell has an indium-gallium-phosphide layer, an indium-gallium-arsenide (InGaAs) layer and a germanium layer. The incoming rays are split into four bands so that energy is extracted by each junction at its most efficient wavelength.

The 34.5% result, using normal sunlight with no concentrators, has been confirmed by the US National Renewable Energy Laboratory. The previous record was made by US company Alta Devices, which reached 24% efficiency for a 800-sq-cm module.

The ACAP team is preparing to build a module as big as Alta’s. “There’ll be some marginal loss from interconnection in the scale-up, but we are so far ahead that it’s entirely feasible,” Dr Mark Keevers said.

The cost of multi-junction solar cells is high, but the Australian researchers are working on new techniques to reduce the manufacturing complexity and create cheaper multi-junction cells. For now, they say the spectrum-splitting approach is perfect for solar towers. UNSW is already working with Victoria-based RayGen Resources Pty Ltd to explore how to use the advanced receiver at concentrated solar photovoltaic (CSPV) projects.

Both, the ACAP research and RayGen have received funding from the Australian Renewable Energy Agency (ARENA) to help develop their technologies.

China’s Trina Solar Ltd (NYSE:TSL) is also a research partner of UNSW.

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