A unique ferroelectric and lead-free material may change solar cell manufacturing
Solar cell manufacturing just became easier, more efficient, and less costly.
A team of researchers at DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab), in collaboration with UC Berkeley, has discovered a unique material that can be used as a simpler approach to solar cell manufacturing, the team reported.
This material is a crystalline solar material with a built-in electric field — also known as "ferroelectricity" — that was reported earlier this year in the journal Science Advances.
Thanks to this discovery, making solar cell devices can be less expensive, include an easier process, and can be more efficient.
How it works
Solar panels require solar cells to convert energy from the sun into electricity. These solar cells require an electric field to separate positive charges from negative ones.
To create this field, manufacturers typically spend a fair amount of money to dope each layer of the solar cell with chemicals that separate the positive and the negative charges. This means electrons flow from the negative side of the device to the positive side — a factor that provides stability and performance.
Grown in the lab from cesium germanium tribromide (CsGeBr3 or CGB), the new ferroelectric material offers an easier and less costly way to make solar cell devices. CGB materials are polarized, meaning one side of the crystal naturally builds up positive charges while the other side builds up negative ones. So no material doping is necessary.
Not only is the material ferroelectric, it's also a lead-free "halide perovskite," which is an emerging class of affordable and easy to make solar materials. Typically, the best-performing halide perovskites contain lead. This lead is known for contaminating our environment and creating public health concerns. The added bonus of the new material the researchers discovered is that it is lead-free and doesn't eschew performance.
“If you can imagine a lead-free solar material that not only harvests energy from the sun but also has the added bonus of having a naturally, spontaneously formed electric field – the possibilities across the solar energy and electronics industries are pretty exciting,” said co-senior author Peidong Yang, senior faculty scientist in Berkeley Lab’s Materials Sciences Division and a professor of chemistry and materials science and engineering at UC Berkeley.
What CGB can be used for
Not only can CGB bring down the cost of manufacturing solar cells, it could also be used to advance a new generation of switching devices, sensors, and super-stable memory devices that respond to light, explained co-senior author Ramamoorthy Ramesh, who was senior faculty scientist in Berkeley Lab’s Materials Sciences Division and professor of materials science and engineering at UC Berkeley at the time of the study.
On top of that, the researchers found that CGB’s light absorption is tunable — spanning the spectrum of visible to ultraviolet light (1.6 to 3 electron volts), an ideal range for coaxing high energy conversion efficiencies in a solar cell, Yang said. Such tunability is rarely found in traditional ferroelectrics, he noted.
What the future holds
The team spent years fine-tuning its research and there's still more to be done. As first author of the paper, Ye Zhang, who was a UC Berkeley graduate student researcher in Yang’s lab at the time, says, there is still more work to be done before the CGB material can make its debut in a commercial solar device, but he’s excited by their results so far.
“This ferroelectric perovskite material, which is essentially a salt, is surprisingly versatile,” he said. “We look forward to testing its true potential in a real photovoltaic device.”
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