ANU researcher achieves world's highest solar cell efficiency for low-grade silicon

Fiacre Rougieux
Thursday 17 December 2015

The price of Photovoltaics modules has drastically decreased during the last decade, however further cost reductions are now increasingly hard.

The key problem with such modules is that it is based on hyper-pure silicon called “electronic-grade silicon”. This material is not only very pure but also very expensive to fabricate.

Now researchers at the ANU have determined a new way to make solar cells cheaper, by using cheaper silicon called “Upgraded Metallurgical-Grade silicon”.

“The challenge with Upgraded Metallurgical-Grade silicon, is that it is less pure which usually leads to solar cells with very low efficiencies” said Dr. Rougieux from ANU College of Engineering and Computer Science.

The researchers were able to use 100% Upgraded Metallurgical-Grade silicon to produce an independently certified solar cell efficiency of 19.8%, the highest for this material and comparable to current industrial cells. This was done in collaboration with Apollon Solar, which provided the wafers and the feedstock produced by FerroPerm in the framework of the PHOTOSIL project.

“What this means is that the process of vapor phase purification (that the solar industry inherited from the microelectronics industry) is not necessary for the solar industry. We believe that it is an overkill to produce 20% silicon solar cells using ultra pure (vapor phase purified) silicon. Upgraded-Metallurgical Grade silicon (liquid state purified) provides a clear and cheaper alternative for high efficiency solar cells.”

The researchers also note that one other added benefit of Upgraded Metallurgical-Grade silicon is that it leads to a significantly lower carbon footprint for the modules. “Going from solid to liquid back to solid requires only a fraction of the energy and cost, compared to solid, vapor, solid” said Dr. Rougieux.

Dr Fiacre Rougieux recently won a 2016 Discovery Early Career Researcher Award (DECRA) through the Australian Research Council and will  aim to produce technologies to maximise the electronic quality of silicon and mitigate the negative impacts of defects on high-efficiency solar cells. The intended outcomes are the development of novel solar cell processes to produce defect-free silicon and new characterisation techniques to image defects in silicon wafers. This would allow high efficiency solar cells to overcome their current limits and unlock the potential of current processes to produce solar cells with efficiency above 26 per cent, providing more efficient and affordable solar electricity.

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