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Toward solving the world energy crisis
Northwestern University, Evanston, Ill., scientists discovered that a surprising mate-
rial, selenide, is the best at converting waste heat to useful electricity. This outstanding
property could potentially provide enormous energy savings. Researchers found that the
crystal form of the chemical compound tin selenide conducts heat so poorly through its lat-
tice structure that it is the most efficient thermoelectric material known. Unlike most ther-
moelectric materials, tin selenide has a simple structure, which provides the key to its
exceptional properties. The efficiency of waste heat conversion in thermoelectrics is re-
flected by its figure of merit, ZT. Tin selenide exhibits a ZT of 2.6, the highest reported to
date at around 650°C. The material’s extremely low thermal conductivity boosts the ZT to
this high level, while retaining electrical conductivity. .
Impurity size could help or hinder superconductor performance
North Carolina State University, Raleigh, re-
searchers found that impurities can either hurt per-
formance—or possibly provide benefits—in a key
superconductive material expected to find use in a host
of applications, including future particle colliders. Im-
purity size determines whether it helps or hinders the
material’s performance. “Bismuth strontium calcium
copper oxide (Bi2212) is the only high-temperature su-
perconductor that can be made as a round wire, and is
expected to have applications in magnets for a wide
range of uses,” says Ph.D. student Golsa Naderi.
To use Bi2212 for potential applications, it needs
to be formed into a multifilamentary wire, which con-
tains 500-1000 Bi2212 filaments embedded in silver,
and then heat-treated to nearly 900°C. However, this processing results in impurities in
the material. These impurities largely consist of porosity and bismuth strontium copper
oxide (Bi2201). Researchers found that nanoscale impurities, from 1.2 to 2.5 nm wide, ap-
pear to improve Bi2212’s performance as a superconductor. .
Thin-film solar cell mystery solved
Treating cadmium-telluride (CdTe) solar cell materials with cadmium-chloride improves
their efficiency, but researchers have not fully understood why until now. A research team
fromOak Ridge National Laboratory, Tenn., the University of Toledo, Ohio, and the National
Renewable Energy Laboratory, Golden, Colo., used electron microscopy and computational
simulations to explore the physical origins of the unexplained treatment process.
Using state-of-the-art electron microscopy techniques to study the thin films’ structure and
chemical composition after treatment, researchers found that
chlorine atoms replaced tellurium atoms within the grain bound-
aries. This atomic substitution creates local electric fields at the
grain boundaries that boost the material’s photovoltaic perform-
ance instead of damaging it. ,
Cross-sectional electron
beam-induced current maps
show the difference in cadmium
telluride solar cells before
(pictured above) and after
(below) cadmium chloride
treatment. The increased
brightness after treatment
indicates higher current
collection at grain boundaries.
Courtesy of ORNL.
ADVANCED MATERIALS & PROCESSES • JULY 2014 12
ENERGY TRENDS
briefs
The U.S. Department of Energy
will support the application of
advanced materials and
manufacturing techniques to
develop next-generation
hydropower technologies with a
$4.4 million grant. As part of the
Clean Energy Manufacturing
Initiative, the funding will help
researchers develop low cost,
integrated hydropower turbine-
generator sets that can produce
cost-competitive electricity at low-
head sites. The funding will also
help pioneer new designs that
apply advanced materials and
innovative manufacturing
techniques to next-generation,
low-head hydropower systems.
Jyllian Kemsley, senior editor at
Chemical & Engineering News, by
the American Chemical Society,
Washington, points out in a recent
article that radiation can cause a
range of problems from
temperature misreadings in
electronic devices to nuclear
power plant explosions. These
problems could be solved by
finding the right materials to deal
with high-radiation environments.
In the case of nuclear power
plants, steel might be better than
zirconium for housing fuel pellets.
For other applications, however,
scientists found that although
radiation punches holes in carbon
nanotubes, when bundled together,
radiation can make them 100
times more rigid. .
Impurity size can either hurt
performance—or possibly provide
benefits—in the superconductive
material Bi2212. Courtesy of Golsa
Naderi.
MatHero, a new project coordinated by
Karlsruhe Institute of Technology
(KIT), Germany, aims to make organic
photovoltaics competitive with their in-
organic counterparts by enhancing effi-
ciency, reducing production costs, and
increasing their lifetime. MatHero—new
materials for highly efficient and reliable
organic solar cells—covers the com-
plete value chain of organic solar cell
fabrication, from polymer design and
synthesis to module fabrication and
characterization to stability assessment. The project goal is an environ-
mentally compatible printed organic solar module initially for use in
off-grid applications. .
Plastic solar cells are
lightweight, mechanically
flexible, and offer many
advantages over
inorganic solar cells.