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Solar panels are attractive in terms of offering an alternative to the air-polluting fossil fuels which satisfy nearly 80% of the world’s energy demands, but they are not very attractive to look at.
However, the shiny blue and black panels littered across the landscape could become less of an eyesore, and blend in more with their surroundings thanks to new research from AMOLF - a research laboratory of the Netherlands Organisation for Scientific Research.
Scientists at the Amsterdam-based institute have developed a method for imprinting existing solar panels with silicon nanoparticles that scatter green light back to an observer. The panels have a green appearance from most angles, and show only a 10% power reduction due to the loss of absorbed green light.
It is hoped this step will make solar panels a more attractive technology to Architects, homeowners and to City Planners, as such installations could melt into the landscape, as could red panels on roofs, and white ones disguised as walls.
Some people say ‘why would you make solar cells less efficient?’ But we can make solar cells beautiful without losing too much efficiency. The new method to change the colour of the panels is not only easy to apply but also attractive as an architectural design element and has the potential to widen their use.
Verena Neder, a Researcher in Photonic Materials at AMOLF and Lead Author of the Paper Published in Applied Physical Letters
Most research on solar cells focusses on increasing their efficiency and reducing costs; those currently sold to consumers ideally convert up to 22% of the sun’s light into usable energy. And while colored solar panels are on the market, the dyes and reflective coatings used to give them their color massively reduce their efficiency.
Neder and her colleagues were able to create their efficient green solar panels through soft-imprint lithography which works a bit like an optical rubber stamp to print a dense array of silicon nanocylinders onto the surface of the cell. Each nanocylinder is approximately 100 nanometers wide – slightly smaller than the diameter of the HIV virus – and exhibits an electromagnetic resonance that scatters a particular wavelength of light.
The geometry of the nanocylinder determines which wavelength it scatters and can easily be fine-tuned to change the color of the solar cells. The imprint reduces the solar panels efficiency by about 2%.
In principle, this technique is easily scalable for fabrication technology. You can use a rubber stamp the size of a solar panel that in one step can print the whole panel full of these little, exactly defined nanoparticles.
Professor Albert Polman, a Scientific Group Leader in Photonic Materials at AMOLF and Senior Author on the Paper
Unlike existing colored solar panels, the nanopatterns give a consistent appearance from different angles, “The structure we made is not very sensitive to the angle of observation, so even if you look at it from a wide angle, it still appears green,” Neder said.
The nanopatterns also could be useful in constructing tandem solar cells, which stack several layers, each designed to absorb certain parts of the spectrum, to achieve efficiencies of greater than 30%.
Next, the Researchers aim to design imprints to create red and blue solar cells. Once they master these three colors - the primary colors of light - they can create any color, potentially even white.
You have to combine different nanoparticles, and if they get very close to each other they can interact and that will affect the color. Going to white is a really big step.
Professor Albert Polman, a Scientific Group Leader in Photonic Materials at AMOLF and Senior Author on the Paper
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