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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 1 6
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SIMPLE METHOD TRANSFORMS
PEROVSKITES
An international team of research-
ers discovered a way to flip a chemical
switch that converts one type of per-
ovskite into another—one with better
thermal stability and that is a better
light absorber. Most perovskite solar
cells produced today are made with a
type of perovskite called methylam-
monium lead triiodide. The problem is
that MAPbI
3
tends to degrade at moder-
ate temperatures. As a result, there is a
growing interest in solar cells that use
a type of perovskite called formamidin-
ium lead triiodide instead.
The team, led by Nitin Padture, a
professor at Brown University, Prov-
idence, R.I., first made high-quality
MAPbI
3
thin films and then exposed
them to formamidine gas at 150°C.
The material instantly converted from
MAPbI
3
to FAPbI
3
while preserving
the microstructure and morphology
of the original thin film. “It’s like flip-
ping a switch,” says Padture. “The gas
pulls out the methylammonium from
the crystal structure and stuffs in the
formamidinium, and does so without
changing the morphology. We’re tak-
ing advantage of a lot of experience in
making excellent quality MAPbI
3
thin
films and simply converting them to
FAPbI
3
thin films while maintaining the
same quality.”
For more information:
Nitin Padture,
nitin_padture@brown. edu,
www.brown.edu.
BOOSTING LI-ION BATTERY
PERFORMANCE
Researchers at Missouri Univer-
sity of Science and Technology, Rolla,
are working to improve the short-life of
lithium-ion batteries by using atomic
layer deposition (ALD). Xinhua Liang,
assistant professor of chemical and
biochemical engineering, is leading
a study that dopes and coats lithium
magnesium nickel oxygen (LMNO)
with iron oxide—at the same time—
through ALD.
“Unlike current research that
either covers the particles’ surface
with insulating film or dopes the parti-
cles to improve battery performance,”
explains Liang, “this ALD process com-
bines the coating and doping processes
An international team of research-
ers developed a method that flips a
chemical switch to convert one type
of perovskite into another. Courtesy
of Padture Lab/Brown University.
BRIEF
Researchers at
Stanford University,
Palo Alto, Calif., developed and tested a new material that can cool a solar cell
by up to 13°C under the California winter sun. Because heat makes solar cells less efficient, the team predicts their
cooling layer could help solar cells turn approximately 1%more sunlight into electricity, a big boost from a simple
add-on. Cooler temperatures also mean the solar cells will likely last longer due to greatly reduced efficiency deg-
radation rates. Researchers achieved the combination of cooling plus maintaining sunlight absorption with a wafer
made of silica.
stanford.edu.
ENERGY TRENDS
Button battery testing in Xinhua Liang’s
lab.
into one, and applying this technique
makes rechargeable lithium-ion batter-
ies last longer.” The new process makes
lithium-ion batteries that have 93%
capacity retention after 1000 cycles of
charge and discharge at room tempera-
ture and 91% at elevated temperatures.
This is equivalent to roughly three years
of battery life with nearly the same per-
formance as a new battery, he adds.
For more information: Xinhua Liang,
573.341.7632,
liangxin@mst.edu, www.
mst.edu.