A whispering gallery is a specially-designed round room that allows a whisper from a person on one end to be carried around and heard clearly by a person on the other end. Researchers at Stanford University have used that premise to create photovoltaic nanoshell structures that cause light to resonate much like sound in a whispering gallery, and let solar cells absorb more light.
The researchers made these nanoshells from tiny balls of silica coated with a layer of silicon. They hollowed out the center with acid, creating an optical shell design that is not only great at letting light in, but holding it there. Associate professor of material sciences at Stanford, Yi Cui said, "The light gets trapped inside the nanoshells. It circulates round and round rather than passing through and this is very desirable for solar applications."
As the light circulates in the shell, it is gradually absorbed by the photovoltaic material -- the longer it circulates the better. When measuring light absorption with their solar material compared to a flat layer of silicon film, there was a much broader absorption of light and when they applied three layers of the nanoshell structures, they were able to boost light absorption to 75 percent in certain parts of the spectrum.
Beyond just trapping more light, these nanocrystalline-silicon shells can be made quickly and more cheaply than flat nanocrystalline-silicon film. Traditional silicon film has to be layered over hours and it costs and weighs 20 times more than the nanoshells because it uses so much more material. When you're using the expensive or scarce materials that are often used in solar applications, like tellurium and indium, that adds up.
The nanoshells also allow many different angles of light to be absorbed and can be bent and twisted in a variety of ways, opening up a broad array of applications for this new solar material, especially where the angle of light may not be optimal for a flat solar panel, like solar clothing or solar sails on ships.
The researchers have published their findings in the journal Nature Communications.