Solar panels, though capable of producing clean renewable energy from just the rays of the sun, aren't necessarily aesthetically pleasing. They don't come in a wide range of colors and you can't see through them, which may keep them from being installed in places or for applications where they could be of use, such as on windows or as a decorative element.
But a new kind of photovoltaic cell could change all of that, as they can be produced in an ultrathin sheet and in various colors, and in turn might open up a lot of possibilities for wider adoption of solar energy.
Researchers at the University of Michigan have invented what they believe to be the "first semi-transparent, colored photovoltaics," which could eventually be used to cover the sides of buildings, as window shades, or even energy-harvesting billboards.
"I think this offers a very different way of utilizing solar technology rather than concentrating it in a small area. Today, solar panels are black and the only place you can put them on a building is the rooftop. And the rooftop of a typical high-rise is so tiny.
We think we can make solar panels more beautiful—any color a designer wants. And we can vastly deploy these panels, even indoors." - Jay Guo, UM professor of engineering
These prototype solar cells aren't nearly as efficient as those found in conventional dark-colored solar panels, because the colored areas in them reflect certain light wavelengths back to our eyes, instead of converting them to electricity, as current solar cells do. However, by being semi-transparent, and capable of taking on different colors, the new cells could be one of the missing links in wider adoption of solar energy, because they could be integrated into the design features of a structure.
To make the cells, an ultrathin sheet of amorphous silicon is sandwiched between two semi-transparent electrodes, which allow the light to hit the semiconductor, as well as carrying the electrical current generated by the cell.
"This hybrid structure, a combination of both organic and inorganic components, lets the researchers make cells that are 10 times thinner than traditional amorphous silicon solar cells. The organic layer replaces a thick 'doped' region that would typically controls the flow of electricity." - UM
Instead of being dyed to produce a color, the new solar cells are mechanically structured to transmit specific wavelengths of light by varying the thickness of the amorphous silicon layer in them. For example, on the prototype that emulates the US flag, the red regions are 31 nanometers thick, and the blue regions are just 6 nanometers thick, which transmit or reflect those colors to the human eye.
The team's work is published at Scientific Reports: Decorative power generating panels creating angle insensitive transmissive colors
[Source: University of Michigan]