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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 | S E P T E M B E R 2 0 1 5
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PEROVSKITE SOLAR CELLS
HOLD PROMISE
The ad hoc team on Perovskite
PV Cells at the Global Research Center
for Environment and Energy based on
Nanomaterials Science (GREEN), NIMS,
Japan, has successfully developed per-
ovskite solar cells with good reproduc-
ibility and stability with excellent semi-
conducting properties. Perovskite solar
cells are promising low-cost and high-
ly-efficient next-generation solar cells
because they can be produced through
low-temperature processes such as spin
coating and generate a large amount of
electricity due to their high optical ab-
sorption together with high open-circuit
voltage. In order to identify the semicon-
ducting properties of perovskites and
formulate guidelines for the develop-
ment of highly efficient solar cell materi-
als, NIMS launched the ad hoc team.
The team created perovskite solar
cells with a simplified structure while
strictly eliminating moisture and oxy-
gen by employing a fabrication tech-
nique developed for the organic solar
cells in the past. These new cells are
stable and have no hysteresis in the
current-voltage curve. Further, the so-
lar cell material serves as an excellent
semiconductor with ideal diode proper-
ties, say researchers.
NANO -ACCORDIONS HELP
CREATE TRANSPARENT
CONDUCTORS
Researchers from North Caroli-
na State University, Raleigh, created
stretchable, transparent conductors
that work due to the structures’ nano-
accordion design. “There are no conduc-
tive, transparent, and stretchable mate-
rials in nature, so we had to create one,”
says Abhijeet Bagal, a Ph.D. student in
mechanical and aerospace engineering.
“Our technique uses geometry to stretch
brittle materials, which is inspired by
springs that we see in everyday life,” Ba-
gal explains. “The only thing different is
that we made it much smaller.”
Researchers created a 3D poly-
mer template on a silicon substrate.
The template is shaped like a series of
identical, evenly spaced rectangles.
In addition, it is coated with a layer of
aluminum-doped zinc oxide, which is
the conducting material, and an elastic
polymer is applied to the zinc oxide. Re-
searchers then flip the whole thing over
and remove the silicon and template.
What’s left behind is a series of sym-
metrical, zinc oxide ridges on an elastic
substrate. Because both zinc oxide and
the polymer are clear, the structure is
transparent. And it is stretchable be-
cause the ridges of zinc oxide allow the
structure to expand and contract, like
the bellows of an accordion. The struc-
ture can be stretched repeatedly with-
out breaking. And while there is some
loss of conductivity the first time the
nano-accordion is stretched, additional
stretching does not affect conductivity.
.
Schematic illustration of electrically biased suspended graphene and light emis-
sion from the center of the suspended graphene. Courtesy of Young Duck Kim/
Columbia Engineering.
BRIEF
Swiss PV start-up Flisom, which began in 2005 on the campus of the Swiss Federal Laboratories for Materials Sci-
ence and Technology (EMPA), is developing roll-to-roll production technologies for low-cost, high-performance CIGS
thin film solar cells on flexible plastic foil. The 4500 m2 pilot plant has a production capacity of 15 MW installed solar
energy. The company’s founder and chairman believes these cells have great potential for providing highly efficient
solar modules and solar systems with low installation costs. , .
ENERGY TRENDS
A new stretchable, transparent conduc-
tor could be used in flexible electronics,
stretchable displays, or wearable sensors.
Courtesy of Abhijeet Bagal.