Researchers at AMOLF have developed green solar panels that reduce power output by about 10 percent by imprinting silicon nanopatterns onto existing cells, according to a study published this week in Applied Physics Letters. The panels appear green from most angles and could make solar technology more acceptable for buildings and landscapes.
Most solar research focuses on increasing efficiency and lowering cost. Consumer panels can ideally convert up to 22 percent of sunlight into usable energy. Colored panels already on the market use dyes and reflective coatings that greatly reduce efficiency. The new method uses soft-imprint lithography, which works like an optical rubber stamp to press a dense array of silicon nanocylinders onto the cell surface. Each nanocylinder is about 100 nanometers wide and scatters a specific wavelength of light. The geometry determines the scattered wavelength, allowing color to be fine-tuned. The imprint reduces efficiency by about 2 percent, though the overall power reduction from lost green light is about 10 percent.
“Some people say ‘why would you make solar cells less efficient?’ But we can make solar cells beautiful without losing too much efficiency,” said Verena Neder, a researcher at AMOLF and lead author of the paper. “The new method to change the color 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.”
“In principle, this technique is easily scalable for fabrication technology,” said Albert Polman, a scientific group leader at AMOLF and senior author on the paper. “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.”
Unlike existing colored 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 could also be useful in tandem solar cells, which stack layers to absorb different parts of the spectrum and achieve efficiencies greater than 30 percent. Next, the researchers are designing imprints for red and blue solar cells. Once they master these three 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,” Polman said. “Going to white is a really big step.”
This article was provided by American Institute of Physics. Materials may have been edited for clarity and brevity.
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