| Feb 12, 2013 |
New world record efficiency for thin film silicon solar cells
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(Nanowerk News) The Photovoltaics-Laboratory (PV-Lab) of EPFL's Insitute of Microengineering (IMT), founded in 1984 by Prof. Arvind Shah and now headed by Prof. Christophe Ballif, is well known as a pioneer in the development of thin-film silicon solar cells, and as a precursor in the use of microcrystalline silicon as a photoactive material in thin-film silicon photovoltaic (TF-Si PV) devices. A remarkable step was achieved by the team led by Dr. Fanny Meillaud and Dr. Matthieu Despeisse with a new world record efficiency of 10.7% for a single-junction microcrystalline silicon solar cell, independently confirmed at Fraunhofer Institute for Solar Energy Systems (ISE CalLab PV Cells) in Freiburg (Germany).
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"Deep understanding has been gained these last years in material quality, efficient light-trapping and cell design, which in combination with careful process optimization led to this remarkable world-record efficiency" says Simon Hänni, PhD student at IMT Neuchâtel. Importantly, the employed processes can be up-scaled to the module level. While standard wafer-based crystalline silicon PV technology implements absorber layers with a thickness of about 180 micrometers for module conversion efficiency of 15 to 20%, 10.7% efficiency was reached here with only 1.8 micrometers of silicon material, i.e. 100 times less material than for conventional technologies, and with cell fabrication temperature never exceeding 200°C.
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Thin-film silicon technology indeed offers the advantages of saving up on raw material and offering low energy payback time, thus allowing module production prices as low as 35 €/m2, reaching the price level of standard roof tiles.
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The reported progress is of paramount importance for increasing further TF-Si PV devices efficiency and potential, as at least one microcrystalline silicon junction is systematically used in combination with an amorphous silicon junction to form multiple junction devices for a broader use of the solar spectrum. The reported record efficiency clearly indicates that the potential of TF-Si multi-junction devices can be extended to > 13.5% conversion efficiency with a minimum usage of abundant and non-toxic raw material at low costs (TF-Si PV modules implementing in their simplest form two glasses and few microns of zinc and of silicon for an easy recycling).
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