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TAP TIMES -26- OCTOBER 2022
Lead-free solar material
offers simpler manufacturing
BERKELEY, Calif. — Solar panels, also
known as photovoltaics, rely on semi-
conductor devices or solar cells to
convert energy from the sun into elec-
tricity.
To generate electricity, solar cells need an
electric field to separate positive charges
from negative charges. To get this field,
manufacturers typically dope the solar cell Light microscopy image of nanowires, 100 to 1,000 nanometers
in diameter, grown from cesium germanium tribromide (CGB) on
with chemicals so that one layer of the a mica substrate. The CGB nanowires are samples of a new lead-
device bears a positive charge and another free halide perovskite solar material that is also ferroelectric.
(Peidong Yang and Ye Zhang/Berkeley Lab)
layer a negative charge.
Unlike conventional solar materials, CGB
Extra costly steps crystals are inherently polarized, where
This multilayered design ensures that one side of the crystal builds up positive
electrons flow from the negative side of a charges and the other side builds up nega-
device to the positive side – a key factor tive charges, no doping required.
in device stability and performance. But
chemical doping and layered synthesis also Halide perovskite
add extra costly steps in solar cell manu- In addition to being ferroelectric, CGB is
facturing. also a lead-free “halide perovskite,” an
emerging class of solar materials that have
Now, a research team led by scientists at intrigued researchers for their affordability
DOE’s Lawrence Berkeley National Labora- and ease of synthesis compared to silicon.
tory (Berkeley Lab), in collaboration with But many of the best-performing halide
UC Berkeley, has demonstrated a unique perovskites naturally contain the element
workaround that offers a simpler ap- lead.
proach to solar cell manufacturing: A crys-
talline solar material with a built-in electric According to other researchers, lead rem-
field. nants from perovskite solar material pro-
duction and disposal could contaminate the
Enabled by “ferroelectricity” environment and present public health con-
This property is enabled by what scientists cerns.
call “ferroelectricity.” The material was
reported earlier this year in Science Ad- No lead, no performance compromise
vances. For these reasons, researchers have sought
new halide perovskite formulations that es-
The new ferroelectric material — which is chew lead without compromising perfor-
grown in the lab from cesium germanium mance.
tribromide (CsGeBr or CGB) — opens the
3
door to an easier approach to making solar “If you can imagine a lead-free solar mat-
cell devices. next page
