Compiled by the editorial desk with reference to the study published in Applied Physics Letters and statements from researchers at AMOLF.

Dutch researchers have developed a way to give solar panels a green tint without the steep efficiency penalties of current colored panels, a step that could make the technology more palatable for architects and homeowners who find traditional black or blue modules unattractive.

The method, described this week in the journal Applied Physics Letters, imprints silicon nanocylinders onto a panel's surface that scatter green light back to the viewer. The result is a panel that appears green from most angles while retaining about 90 percent of its power output—a far smaller loss than the dyes or reflective coatings used in commercial colored panels today.

“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, a research institute in Amsterdam, 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.”

Most solar research has centered on boosting efficiency and cutting costs. Standard panels available to consumers convert up to 22 percent of sunlight into electricity. Colored panels already exist, but the dyes and coatings that create their hues can cut efficiency dramatically, making them less practical for many installations.

The AMOLF team used a technique called soft-imprint lithography, which works like an optical rubber stamp. A stamp the size of a solar panel imprints a dense array of silicon nanocylinders onto the surface. Each cylinder is about 100 nanometers wide and resonates electromagnetically, scattering a specific wavelength of light. By adjusting the cylinder's geometry, researchers can fine-tune the color. In this case, the imprint reduced the panel's efficiency by only about 2 percent.

Why the Color Matters

The appeal goes beyond aesthetics. If solar panels can blend into rooftops, facades, or landscapes, they may be more readily accepted by city planners and homeowners who resist the stark look of conventional modules. Green panels could disappear into grassy surroundings, red ones match tile roofs, and white ones mimic walls—expanding where solar can be installed.

Unlike existing colored panels, the nanopatterns provide a consistent hue from different viewing 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 technology may also benefit tandem solar cells, which stack multiple layers to capture different parts of the spectrum and can achieve efficiencies above 30 percent.

Next, the researchers are designing imprints for red and blue cells. Once they master the three primary colors of light, they could combine them to produce 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,” said Albert Polman, a scientific group leader at AMOLF and senior author of the paper. “Going to white is a really big step.”

The technique is still in the lab, but Polman noted it is scalable. “In principle, this technique is easily scalable for fabrication technology,” he said. “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.”