Y the octahedra. The octahedra can easily
rotate while maintaining contact at
their corners, giving perovskites unusu-
al properties that have long been ex-
ploited in specialized applications.
Lithium niobate, for example, acts both
as a piezoelectric transducer between
electrical and mechanical signals and
in high-speed optical modulators for
telecommunications. In the new mate-
rials, the arrangement follows these
rules, but the ingredients are different.
OVER THE PAST five years, rap- id progress in photovoltaic technology has been fur- ther accelerated by materi- als called perovskites. They
require only common ingredients and
relatively easy manufacturing meth-
ods, holding out the possibility of
cheap thin-film cells on a variety of sur-
faces or combined with silicon in large
panels. In the laboratory, small-area
cells made with these materials already
feature solar-conversion efficiencies as
high as 22%, rivaling those of tradition-
al silicon solar cells.
“I’ve been in the business since the
late 70s,” said David Cahen, a chemist
and materials scientist at the Weiz-
mann Institute in Rehovot, Israel. “This
is a time of developments in solar cells
and photovoltaics that is unprecedent-
ed,” including new materials, efficiency
improvements, and cost reductions.
But “there has not been anything like
this one,” he said. “The perovskites
have put all of those into shadow.”
A practical technology will require
further engineering for large-scale
manufacture and long-term stability,
and there are still open scientific ques-
tions. Moreover, although researchers
think they can avoid environmental
toxicity from lead in the materials, they
may not be able to avoid a public per-
ception of danger.
But perovskites’ potential is clearly
shaking up the field.
A New Twist
Perovskites are a well-known family of
materials whose crystals consist of a lattice of octahedra, each comprising six
negative ions around a positive ion, with
a second positive ion in the gap between
New materials could allow cheaper, more efficient
solar cells for both traditional and novel applications.
Science | DOI: 10.1145/3148690 Don Monroe
Material structure sketching the stacking of nanometer-thick layers of two-dimensional
perovskite and organic spacing layers.