Tech Briefs Magazine - February 2022 - 21

and bottom of the chip as well as when
they run into one another. By meticulously
planning the design of the transducers
and controlling the frequency
and strength of the vibrations causing
the waves, the researchers are able to
create vortices that, when combined,
form tunnels that can push and pull
droplets in any direction along the surface
of the device.
The new system uses dual-mode transducers
that can transport droplets along
an x or y axis, based on two different
streaming patterns. By using dual-mode
transducers, the researchers were able to
move droplets along two axes while si -
multaneously reducing the complexity of
the electronics four-fold. They were also
able to reduce the operating voltage of
the transducers three to seven times
lower
than a previous
system, which
allowed it to simultaneously control eight
droplets. And by introducing a microcontroller
to the setup, the researchers
were able to program and automate
much of the droplet movement.
The ability to control droplets in a
manner similar to the logic systems
found on a computer chip is essential to
a wide variety of clinical and research
procedures. The next step is to combine
the miniaturized radio-frequency power
supply and control board for large-scale
integration and dynamic planning.
For more information, contact Erin Kramer
at erin.kramer@duke.edu; 919-660-4257.
Fabrication Method for Large-Scale Production of
Perovskite Solar Cells
The sulfolane-additive process yields easy fabrication, low cost, and long operating life.
Los Alamos National Laboratory, Los Alamos, NM
A
simpler solution for fabricating stable
perovskite solar cells overcomes
the key bottleneck to large-scale production
and commercialization of this
renewable-energy technology, which
has remained out of reach for more
than a decade.
Researchers demonstrated the new
ap proach through two mini modules
that reached high levels of converting
sunlight to power with greatly extended
operational lifetimes. Since the process
is facile and low cost, it could be easily
adapted to scalable fabrication in
industrial settings.
A perovskite is any material with a particular
crystal structure similar to the
mineral perovskite. Perovskites can be
engineered and fabricated in extremely
thin films, which makes them useful for
solar photovoltaic cells. Perovskite photovoltaics,
seen as a viable competitor to
the familiar silicon-based photovoltaics
on the market for decades, have been a
highly anticipated emerging technology
over the last decade. Commercialization
has been slowed by the lack of a solution
to scaling up production of high-efficiency
perovskite solar cell modules
from the benchtop to the factory floor.
The team invented a one-step spin
coating method by introducing sulfolane
as an additive in the perovskite precursor,
or the liquid material that creates the perovskite
crystal through a chemical reaction.
As in other fabrication methods,
that crystal is then de posited on a substrate.
The new process allowed the team
to produce high-yield, large-area photovoltaic
devices that are highly efficient in
Tech Briefs, February 2022
Cov
A new dipping process using a sulfolane additive creates high-performing perovskite solar cells.
The method is inexpensive and well-suited for scaling up to commercial production. (Photo: Los
Alamos National Laboratory)
creating power from sunlight. These
perovskite solar cells also have a long
operational lifetime.
Through a simple dipping method,
the team was able to deposit a uniform,
high-quality perovskite crystalline thin
film covering a large active area in two
mini modules, one of about 16 square
centimeters and the other nearly 37
square centimeters. Fabricating uniform
thin film across the entire photovoltaic
module's area is essential to
device performance. The mini modules
achieved a power conversion efficiency of
17.58 percent and 16.06 percent, respectively.
The power conversion efficiency is a
measure of how effectively sunlight is converted
into electricity.
For other perovskite fabrication methods,
one of the major roadblocks to
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industrial-scale fabrication is their narrow
processing window - the time during
which the film can be laid down on
the substrate. To get a uniform crystalline
film that's well bonded to the
layer below it, the deposition process has
to be strictly controlled within a matter
of seconds.
Using sulfolane in the perovskite precursor
extends the processing window
from 9 seconds to 90 seconds, forming
highly crystalline, compact layers over a
large area while being less dependent
on the processing conditions. The sulfolane
method can be easily adapted to
existing industrial fabrication techniques,
which helps to pave the path
toward commercialization.
For more information, contact Charles
Poling at cpoling@lanl.gov; 505-257-8006.
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Tech Briefs Magazine - February 2022

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