Solar panels provide access to virtually unlimited clean energy, yet this renewable resource is not utilized anywhere close to its potential. There are many reasons for this, including the expense and limited selection of solar panels. Experts are working to replace the traditional black and blue panels with green, red, and white colors that may be more enticing to home and building owners.
Researchers have developed a technique to imprint solar panels with silicon nanopatterns which cast out green light. The loss of absorbed green light only reduces the effectiveness of the panels by approximately 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 lead author Verena Neder. “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.”
Previous research on solar cells has been mainly focused on increasing the efficiency of panels and reducing the cost. The solar panels currently available on the market can convert up to 22 percent of sunlight into usable energy. The colored solar panels that are available are not nearly as effective due to the dyes and reflective coatings that give them their color.
For the current study, researchers used soft-print lithography to create green solar panels that maintain most of their efficiency. This process stamps a heavy concentration of silicon nanocylinders onto the cell surfaces. At about 100 nanometers wide, each nanocylinder has an electromagnetic vibrancy that scatters a particular wavelength of light. The nanocylinders can be adjusted to alter the color of the solar cell.
“In principle, this technique is easily scalable for fabrication technology,” said senior author Albert Polman. “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.”
The solar panels enhanced with nanopatterns appeared green from almost any angle, which is a huge improvement on colored panels that are currently on the market. The nanopatterns may also make it possible to stack several layers of cells which are developed to absorb different parts of the spectrum. This design could improve the efficiency of solar panels to more than 30 percent.
The study, which is published this week Applied Physics Letters, will continue with the development of imprints for red and blue solar cells. The creation of green, red, and blue solar cells may ultimately enable the researchers to develop white solar panels.
“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 Polman. “Going to white is a really big step.”