Tech Briefs Magazine - March 2022 - 45

New Technology Can Lead to Highly Foldable Solar Cells
Carbon nanotubes (CNT)
* embedded in polymide substrate (PI)
* p-doping with molybdenum oxide
(MoOx) via thermal annealing
Foldable devices are
next-generation electronics...
CNT
...that can be applied to solar cells,
to integrate them into everyday items
However, foldability depends
on harsher deformations...
...which are not possible with
conventional substrate materials
(MoOx)
(p-doping)
Thickness
= 7 µm
PI
Folding test revealed the
following properties:
High power conversion
efficiency
Strong substrate adherence
High conductivity
Resilient to over 10,000
folding cycles
Glass film
Indium tin
oxide film
The prototype transparent conductor can pave the way for efficient and stable foldable devices
The prototype transparent conductor can pave the way for efficient and stable foldable devices. (Photo: Pusan National University)
Foldable Perovskite Solar Cells Using Carbon Nanotube-Embedded Ultathin Polyimide Conductor
Yoon et al. (2021)
Advanced Science
DOI: 10.1002/advs.202004092
ing. To address this problem, the team
embedded the conducting layer into a
polyimide (PI) substrate, filling the void
spaces in the nanotubes.
To ensure maximum performance,
they also doped the resulting material to
increase its conductivity. By introducing
small impurities (in this case, withdrawn
electrons to molybdenum oxide) into
the SWNT-PI nanocomposite layer, the
energy needed for electrons to move
across the structure is much smaller, and
hence, more charge can be generated
for a given amount of current.
The resulting prototype far exceeded
the team's expectations. Only 7 micrometers
thick, the composite film exhibited
exceptional resistance to bending,
al most 80 percent transparency, and
a power conversion efficiency of 15.2
percent, the most ever achieved in solar
cells using carbon nanotube conductors.
For more information, contact Professor Il
Jeon at il.jeon@spc.oxon.org.
Recycled Cotton Becomes New Fabric
A method converts cotton into sugar, which can be turned into spandex, nylon, or ethanol.
Lund University, Lund, Sweden
R
esearchers have developed a method
that converts cotton into sugar that
in turn can be turned into spandex, nylon,
or ethanol.
Most discarded materials go straight
into an incinerator or end up in landfills.
Fabrics with strong fibers can be reused.
However, much of the fabric that
is discarded has fibers that are too short
for re-use and sooner or later, all cotton
fibers become too short for the process
known as fiber regeneration.
The team's method breaks down the
plant fiber in cotton - the cellulose --
into smaller components. Rather than
using micro-organisms or enzymes, the
process involves soaking the fabrics in sulphuric
acid. The result is a clear, dark, amber-colored
sugar solution.
Tech Briefs, March 2022
Glucose is a very flexible molecule and
has many potential uses. The new method
would produce chemicals that in turn
could become various types of textiles including
spandex and nylon. An alternative
use could be to produce ethanol.
From a normal sheet, the method extracts
five liters of sugar solution, with
each liter containing the equivalent of
33 sugar cubes. That liquid, however,
could not be turned into a soft drink,
as it also contains corrosive sulphuric
acid. One of the challenges is to overcome
the complex structure of cotton
cellulose.
What makes cotton unique is that its
cellulose has a high crystallinity, making
it difficult to break down the chemicals
and reuse the components. In addition,
www.techbriefs.com
there are a lot of surface treatment substances,
dyes, and other pollutants that
must be removed.
The concept of hydrolizing pure cotton
is nothing new; it was discovered
in the 1800s. The difficulty has been to
make the process effective, economically
viable, and attractive.
Once the recipe formulation is complete,
it will be both relatively simple
and cheap to use. For the process to become
a reality, the logistics must work.
There is currently no established way of
managing and sorting various textiles
that are not sent to ordinary clothing
donation points.
For more information, contact Edvin
Ruuth, Department of Chemical Engineering,
at edvin.ruuth@chemeng.lth.se.
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Tech Briefs Magazine - March 2022

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