New world record efficiency for thin film silicon solar cells

February 12, 2013, Ecole Polytechnique Federale de Lausanne

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).

"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 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.

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.

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 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% 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).

Explore further: Sharp Develops Mass-Production Technology for Triple-Junction Thin-Film Solar Cells

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1.8 / 5 (4) Feb 12, 2013
The primary problem with thin-film cells is you end up with a much larger system and much higher installation costs.
4.2 / 5 (5) Feb 12, 2013
Roof tile prices?!? You're not worried about a larger system here. your just using solar cell in place of roof tiles.

From a builders perspective, same cost but comes with some free power.

It might not get you off the grid, but it will help lower utility costs and environmental impact.
1 / 5 (1) Feb 12, 2013
4 / 5 (3) Feb 12, 2013
Then just cover these with a thin sheet of Gorilla glass and you get durable roof tiles with electricity.
4.3 / 5 (3) Feb 12, 2013
Roof tile prices?!? You're not worried about a larger system here. your just using solar cell in place of roof tiles.

You can't actually use them -as- roof tiles.

There's a lot more involved than just stacking them up like ordinary roof tiles and putting a nail through to keep them in place. You need to provide wiring access, free ventilation under the panels to keep them cool, weatherproofing and service access.

Although it would be neat if someone made a roof tile that had a solar panel built into it.
1 / 5 (1) Apr 01, 2013
Cool the PV with copper tubing to pre-heat home hot water.

Dual-purpose solar helps shorten the investment payback - that number has been a problem since the 70's!
not rated yet Apr 04, 2013
Already ahead of you Eikka

Those are shingles, not tiles. A shingle roof doesn't last as long as a tile roof, and you can't use them as actual roof shingles - rather you install them on top of a mat you lay on a shingled roof.

And again, it's not very optimal because the roof surface gets really hot in the sun.

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