Clean Power plasmonic effect AMOLF CalTech

Published on November 2nd, 2014 | by Tina Casey


Brace Yourself, Here Comes The Plasmonic Solar Cell Of The Future

November 2nd, 2014 by  

We’ve been keeping tabs on the plasmonics scene for a while and we just got wind of an interesting new development from the Netherlands in partnership with Caltech. If the Netherlands connection doesn’t exactly ring your bells, recall that Caltech is the institutional home of NASA’s Jet Propulsion Laboratory, which is heavily invested in the related field of photonics.

As for the Netherlands angle, that would be FOM Institute AMOLF, which belongs to the Netherlands Organisation for Scientific Research. AMOLF  has been partnering with Caltech on plasmonics for a number of years now, so let’s see what they’re up to in terms of influencing the next wave of low cost, high efficiency solar cells.

plasmonic effect AMOLF CalTech

Artist impression of the plasmo-electric effect (image rotated), © AMOLF/Tremani via AMOLF.

The Plasmonic Effect

For those of you new to the topic, plasmonics (aka the plasmo-electric effect) refers to the ability of certain metals to capture light and convert it to an electrical charge.

For more details you can check out an article on plasmonics at our sister site PlanetSave, but for now let’s just say that plasmonics refers to electrons that are in an excited state when exposed to light.

Today’s solar cell technology is based on silicon and other semiconductors, so introducing another class of materials into the mix could bust the solar field wide open in terms of cost, efficiency, and application.

Think of the new opportunities afforded by the emerging generation of flexible, lightweight thin film solar cells compared to conventional silicon solar cells and you can see what the future could bring.

The plasmonic effect has actually been around the block before, give or take a few centuries. As described in the AMOLF press materials, stained glass masters of early church architecture created vivid colors by embedding tiny particles of metal in the glass, to enhance light absorption and diffusion.


Some of the recent developments in the plasmonic field include a “black metal” solar cell from Lawrence Livermore National Laboratory, consisting of a surface etched with nanoscale pillars. A similar approach, described as a “forest of gold nanorods,” is under way at the University of California-Davis.

And yes, there is a plasmonic graphene angle but we’ll save that for another time.

The AMOLF-Caltech Plasmonic Collaboration

AMOLF and Caltech had previously examined the plasmonic effect in gold nanospheres exposed to a laser. That study found that the nanospheres exhibited the potential for a negative charge when exposed to blue light, and a positive potential under red light.

For the next step, which formed the basis of the new plasmonics study (just published in the journal Science, if you want to check it out), the team took a somewhat different path than that of Lawrence Livermore or UC-Davis.

Instead of creating rods or pillars, they engineered tiny circuits consisting of a film of gold only 20 nanometers thick, into which they “drilled” holes measuring only 100 nanometers in diameter (a nanometer is a billionth of a meter, for those of you keeping score at home).

2 plasmonic effect AMOLF CalTech

Measuring the plasmonic effect (courtesy of AMOLF).

The figure above, provided by AMOLF,  shows (a) a rendering of a metal nanoparticle exposed to light, (b) an electron microscopy image of the nanoscale holes in gold film, (c) a chart of the measurements taken for different spacings between the holes, and (d) the same measurements interpreted for their electrical potential.

Here’s the happy recap of the study from AMOLF:

…these metal hole arrays possess bright plasmon resonances, of which the wavelength can be controlled by the spacing between the holes. When irradiating these circuits with a laser, and gradually tuning the color of the light from blue to red, a negative potential (-100 mV) was found for blue light and a positive potential (+100 mV) for red light.

Since When Is Gold Cheaper Than Coal?

When you see gold in connection with energy technology, you’ve got to be thinking that the cost factor is prohibitive. There’s certainly something to say for that line of thinking if you look at fuel cell technology, which has been bumping up against a price wall partly due to the use of expensive platinum catalysts.

So, don’t hold your breath for that shiny new golden solar cell to roll around.

On the other hand, foundational research at Caltech could lead to the discovery of other solar-friendly metals that could beat gold on cost-effectiveness, if not efficiency.

That brings us to the other angle to consider, which is cradle-to-cradle cost. Punching holes into a thin film, even at the nanoscale level, lends itself to the emerging crop of low cost, high throughput manufacturing technologies that are pushing the clean energy envelope. The use of metals that lend themselves to efficient, low-carbon recovery and recycling processes would round out the circle.

Now compare the cost of sunlight as an energy source  to coal, or for that matter natural gas and oil. After a solar array is completed, the energy source comes beaming down from the heavens, free of charge. With fossil fuels, not so much. Aside from climate change issues, after you construct your fossil power plant you still have to account for a steady stream of expense to keep it running, including the local public health, economic and environmental risk factors related to fuel extraction, preparation, and transportation.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • June Birch

    Could someone please tell me what would happen in the case of a nuclear power accident and much higher levels of radiation. Would it have any effect on these types of solar cells? I’m guessing that it wouldn’t, but I don’t know enough and I’m quite interested. (I really like solar.).

    • jaffons

      hmmm.. Are you planning to explode nuclear plant so it would increase solar power efficiency and degrade nuclear power? 😛

  • GCO

    Brace yourself, here comes the cell of the future

    boasts Tina in her headline… then utterly fails to articulate anything tangible re efficiency, stability/durability, cost, manufacturability, and, more importantly, future availability.
    We learn nothing of substance, except that there might be “potential”. Even the author seems unconvinced actually:

    So, don’t hold your breath for that shiny new golden solar cell to roll around.

    and concludes with some platitudes about renewables vs fossil fuels.

    Thanks for wasting my time.

    • Hans

      “then utterly fails to articulate anything tangible re efficiency,
      stability/durability, cost, manufacturability, and, more importantly,
      future availability.”

      In such an early stage of the development such concrete questions can of course not be answered.

      Tina seems to have a nose for picking out interesting developments, and write attention grabbing headlines. But indeed the content of the articles often doesn’t match with those headlines. Tina’s writing style is also not my cup of tea (reminds me of a teacher who tries to be popular with the students by using street lingo of five years ago). But I find her articles useful for keeping an eye on new development and then ixquicking for articles with more information.

  • It’s so heartening to see the world digging in to implement sustainability. After a 200 year run, it’s time to retire fossil fuel of every ilk to the footnotes of world history.

  • Ronald Brakels

    Twenty nanometers is about 150 gold atoms thick. So to make a square meter of these gold plasmonic solar cells would require one billionth of 386 tonnes of gold or 0.386 grams which at the moment comes to about $15. If it was only as efficient as a good silicon panel and had 200 watts per square meter that would come to about 7.5 cents a watt. Actually, it should be less than that since the gold has holes in it.

    • Doug Cutler

      That’s not much. I wonder what the life span would be for a panel made up primarily of incorruptible gold. There must be some other supportive materials involved. But what about a panel primarily gold and glass? Is it possible we finally have something useful for gold to do besides sitting around and looking shinny?

      • Philip W

        We already have some useful applications for gold e.g. in high frequency technology.

        • Doug Cutler

          Perhaps you may kindly grant the commenter some hyperbolic leeway. Even so, I still see the a lot of gold sitting around doing not much.

          To the main point: I’d still be interested to see some durability specs on plasmonic gold if available.

          • Philip W

            I didn´t mean to offend you.
            It´s just that a lot of people may not know that and before they think that gold right now is useless besides being shiny and expensive, I wanted to add this.
            Forgive me if it seemed otherwise.

          • Doug Cutler

            Relocated comment.

          • TinaCasey

            Yes no apologies needed here, and anyways at the rate things are going a synthetic gold substitute is within the realm of possibility.

      • Ronald Brakels

        Well, I would expect the gold grid and attached carbon molecules to degrade over time. Atoms migrate very slowly through materials, with the exact speed depending on temperature. For silicon PV this isn’t such a huge deal as for each atom of doping material there might be say a milliion silicon atoms and their precise location doesn’t matter, but for these organic/gold cells, or rather potential cells in the future, position is very important and I’d expect them to degrade much more rapidly, perhaps similar to organic dye solar cells. That it, much faster than silicon PV. However, if the cost can be brought down low enough, then economically that would make up for the faster degradation.

        • Doug Cutler

          Alas, another likely also-ran. But a fascinating line of inquiry all the same. Thanks.

          • Globe99

            Actually, there are methods in the literature to coat these materials with a thin layer of transparent oxide that would make them impervious to environmental damage. All that matters is that light can reach them.

        • Joseph Dubeau

          One way to make PV cheaper is to replace the silver with copper.

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