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Perovskites (from 20)
to separate into a 2D layered structure, or
lose ordered structure entirely,” says Tonio
Buonassisi, professor of mechanical engi-
neering at MIT and director of the Photo-
voltaics Research Laboratory.
Highly tunable
“Perovskites are highly tunable, like a
build-your-own-adventure type of crystal
structure,” he says.
Prof. Buonassisi aims to make Perovskites competitive with sili-
That structure of interlaced lattices con- con for solar cells. (MIT)
sists of ions or charged molecules, two of From a research perspective, Buonassisi
them (A and B) positively charged and the says, one advantage of perovskites is that
other one (X) negatively charged. The A they are relatively easy to make in the lab —
and B ions are typically of quite different the chemical constituents assemble readily.
sizes, with the A being larger.
“Easy come, easy go!”
Within the overall category of perovskites, But that’s also their downside: “The mate-
there are a number of types, including rial goes together very easily at room tem-
metal oxide perovskites, which have found perature,” he says, “but it also comes apart
applications in catalysis and in energy very easily at room temperature. Easy
storage and conversion, such as in fuel come, easy go!”
cells and metal-air batteries.
To deal with that issue, most research-
But a main focus of research activity for ers are focused on using various kinds of
more than a decade has been on lead ha- protective materials to encapsulate the
lide perovskites, according to Buonassisi. perovskite, protecting it from exposure to
air and moisture.
The biggest obstacle: durability
While perovskites continue to show great But others are studying the exact mecha-
promise, and several companies are al- nisms that lead to that degradation, in
ready gearing up to begin some com- hopes of finding formulations or treatments
mercial production, durability remains the that are more inherently robust. A key find-
biggest obstacle they face. ing is that a process called autocatalysis is
largely to blame for the breakdown.
While silicon solar panels retain up to 90
percent of their power output after 25 Buonassisi and his co-researchers recent-
years, perovskites degrade much faster. ly completed a study showing that once
perovskites reach a usable lifetime of at
Great progress has been made — initial least a decade, thanks to their much lower
samples lasted only a few hours, then initial cost, that would be sufficient to make
weeks or months, but newer formulations them economically viable as a substitute
have usable lifetimes of up to a few years, for silicon in large, utility-scale solar farms.
suitable for some applications where lon- —David L. Chandler, mit.edu
gevity is not essential.
