Tech Briefs Magazine - August 2022 - 28

Materials & Coatings
Enhanced Material Stable Enough for Solar Cells
A simple change to the surface of perovskite removes a barrier to its functionality.
Purdue University, West Lafayette, IN
S
oft and flexible materials called ha lide
perovskites could make solar cells
more efficient at significantly less cost but
they're too unstable to use. A research
team has found a way to make halide perovskites
stable enough by inhibiting the
ion movement that makes them rapidly
degrade, unlocking their use for solar
panels as well as electronic devices. The
discovery also means that halide perovskites
can stack together to form heterostructures
that would allow a device to
perform more functions.
Solar cells made out of perovskites in the
lab perform just as well as the solar cells on
the market made of silicon. Perovskites
have the potential to be even more efficient
than silicon because less energy is
wasted when converting solar energy to
electricity. And because perovskites can be
processed from a solution into a thin film,
like ink printed on paper, they could be
more cheaply produced in higher quantities
compared to silicon.
A perovskite is made up of components
that an engineer can individually replace
at the nanometer scale to tune the material's
properties. Including multiple perovskites
in a solar cell or integrated circuit
would allow the device to perform different
functions, but perovskites are too unstable
to stack together.
Simply by adding a rigid, bulky molecule
called bithiophenylethylammonium
to the surface of a perovskite stabilizes the
movement of ions, preventing chemical
bonds from breaking easily. The researchJust
adding a bulky molecule to the surface of a perovskite could make the material stable enough
for incorporating into solar panels. (Image: Purdue University illustration/Enzheng Shi)
ers also demonstrated that adding this
molecule makes a perovskite stable
enough to form clean atomic junctions
with other perovskites, allowing them to
stack and integrate.
The bulky molecule allows a perovskite
to stay stable even when heated to 100 °C.
Solar cells and electronic devices require
elevated temperatures of 50-80 °C to operPlant-Based
Thermotherapy Patch
Additional applications include defogging/defrosting, wearable devices, industrial heat
systems, sensors, thermochromic displays, and microfluidic chips.
Tampere University, Tampere, Finland
A
28
team of researchers has developed a
biodegradable, transparent, flexible,
and fast-acting thermotherapy patch
from plant leaves that is compatible with
flexible electronic applications. Plant material
was used to reduce the amount of
electronic waste.
The researchers used leaves from a
Bodhi tree (Ficus religiosa). The veins of the
leaves have a fractal pattern that makes the
surface highly flexible and shearable. Silver
nanowires were attached to the leaf
skeleton and the surface was encapsulated
in a biodegradable, transparent tape. The
fractal-based design can also be used in
flexible electronic applications, as it overcomes
the limitations of conventional planar
designs by maximizing the surface
area at the microscale, or more specifically,
maximizing the surface area-to-volume rawww.techbriefs.com
tio
via simple scaling. The large surface
area enables effective heat transfer, allowing
a rapid response time and preventing
overheating. Due to the flexibile structure
and uniform heating of the patch, it can
also be attached to moving joints.
In orthopedics, medical thermotherapy
pads are commonly used to reduce pain,
improve blood circulation, and de crease
inflammation. They are also used in the
Tech Briefs, August 2022
ate. It could also be possible to incorporate
perovskites into computer chips. Tiny
switches in computer chips, called transistors,
rely on tiny junctions to control electrical
current. A pattern of perovskites
might allow the chip to perform more
functions than with just one material.
For more information, contact Letian
Dou at dou10@purdue.edu.

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Tech Briefs Magazine - August 2022

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