Silver Nanoparticles Boost Thin-Film Efficiency

In 2008, thin-film solar became the latest candidate on the short list for the holy grail of renewables, achieving record efficiency ratings in the laboratory that caught the attention of both the energy industry and the mainstream press. While not quite as effective as traditional silicon-based photovoltaics, which regularly achieve conversion efficiencies of over 20%, the newer thin-film panels offer an obvious advantage in that they use less material and are therefore cheaper to produce. Now new developments promise to increase thin-film’s efficiency enough to lower the costs of generating energy near the range of cheaper-but-oh-so-dirty fossil fuels.

Researchers at the Australian National University and the Center of Nanophotonics at the Institute for Atomic and Molecular Physics in Amsterdam have discovered that “sprinkling” the surface of thin-film panels with nanoparticles of silver (Ag) can significantly increase the amount of light the panels can absorb. Previous thin-film applications proved less effective at handling wavelengths of light from both the longer (redder) and shorter (bluer) ends of the electromagnetic spectrum, limiting their efficiency in experiments. Incorporating minute silver flecks, however, has the effect of “thickening” the cells horizontally, allowing for the conversion of these more elusive wavelengths. The electrons in silver are highly sensitive to visible light and react by emitting their own photons in the form of “surface plasmons”, electromagnetic waves that propagate across the surface of the panel rather than through it. By traveling in this manner, the plasmons come into contact with more of the cell’s silicon, increasing its ability to convert light into electricity.

According to the researchers’ findings recently published in Optics Express (see abstract), this breakthrough could improve the conversion rates of these wavelengths nearly tenfold. And though silver is expensive, the overall cost of thin-film technology should hardly be affected. The metal is used in such small quantities that analysts predict a price increase of no more than a few cents per panel.

Sources: “19.9%: New Thin Film Solar Efficiency Record”, TreeHugger; “Seeing Red”, The Economist; Catchpole, K.R. and A. Polman, “Plasmonic Solar Cells”, Optics Extress (Vol 16, Issue 26); “Enhancing solar cells with nanoparticles”, www.nanitenews.com; Paddon, Paul and Bernhard Michel,“Enabling Solar Cells: Virtual Prototyping of Nanostructures”, www.simuloptics.com; “Surface plasmon resonance”, Wikipedia;  www.erbium.nl (Photonic Materials Group website).


Posted on Friday, January 9th, 2009 at 4:27 pm | Tagged in Energy, Energy Efficiency, Photovoltaics, Renewables, Technology | posted by Jamie

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