An inherent inefficiency in any solar power setup that sees only around 80 percent of the electricity generated reaching a battery for storage and later use has been overcome in a new "breathing" solar cell, U.S. researchers say.
In a normal solar power setup where photovoltaic panels convert sunlight into electricity, any excess electricity not immediately used to power electronics is sent to a battery to be held in reserve -- but only about 80 percent of the energy safely makes it there, the researchers say.
Now, scientists at Ohio State University say they've combined the generating and storage functions of solar power in a single device, a solar cell that can store its own power; in effect, a solar battery.
"The state of the art is to use a solar panel to capture the light, and then use a cheap battery to store the energy," lead inventor Yiying Wu, a professor of biochemistry and chemistry, says. "We've integrated both functions into one device. Any time you can do that, you reduce cost."
In the OSU device a special mesh solar panel allows the battery to "breathe," vital to how it creates and stores energy, the researchers explain.
The mesh in the OSU battery belongs to a class of devices known as dye-sensitized solar cells, where colored dyes are used to tune the wavelength of light a cell captures.
Light hits the mesh solar panel and creates electrons that, inside the device, are involved in chemical decomposition of lithium peroxide into oxygen and lithium ions. The oxygen is released while the lithium ions are stored within the battery.
When the battery is discharging, it consumes oxygen from the air to re-form the lithium peroxide.
"Basically, it's a breathing battery," Wu says. "It breathes in air when it discharges, and breathes out when it charges."
Since light is converted to electrons inside the battery, rather than electrons having to travel between a solar cell and an external battery, the new device approaches 100 percent efficiency rather than the 80 percent storage efficiency of a normal solar cell-battery setup, the researchers report in the journal Nature Communications.
They've repeatedly charged and discharge the battery while analyzing how well the devices electrode materials survived, to get an indication of battery life, they said.
Their solar battery's lifetime should be comparable to rechargeable batteries already in the marketplace, they said.
