From NIST: “Unexpected Property May Raise Material’s Prospects as Solar Cell”

NIST

May 22, 2017

Ben Stein
benjamin.stein@nist.gov
(301) 975-2763

NIST, collaborators find first compelling evidence of new property known as “ferroelasticity” in perovskites.

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Schematic shows a perovskite sample (black) examined by the photothermal induced resonance technique. When the sample absorbs pulses of light (depicted as disks in purple cones), the sample expands rapidly, causing the cantilever of an atomic force microscope (AFM) to vibrate like a struck tuning fork. The cantilever’s motion, which is detected by reflecting the AFM laser light (red) off the AFM detector, provides a sensitive measure of the amount of light absorbed. Credit: NIST

Crystalline materials known as perovskites could become the next superstars of solar cells. Over the past few years, researchers have demonstrated that a special class of perovskites—those consisting of a hybrid of organic and inorganic components—convert sunlight into electricity with an efficiency above 20 percent and are easier to fabricate and more impervious to defects than the standard solar cell made of crystalline silicon. As fabricated today, however, these organic/inorganic perovskites (OIPs) deteriorate well before the typical 30-year lifetime for silicon cells, which prevents their widespread use in harnessing solar power.

Now a team led by Andrea Centrone at the National Institute of Standards and Technology (NIST) and Jinsong Huang and Alexei Gruverman of the University of Nebraska has found the first solid evidence for a property of OIPs that may provide a new way to improve their long-term stability as solar cells.

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Image recorded by an atomic force microscope reveals the topography of a polycrystalline sample of the perovskite, including the boundaries between crystals. Credit: NIST

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Image taken with the photothermal induced resonance technique shows the newly discovered ferroelastic domains (striations) within most crystals. Scale shows the PTIR signal intensity, a measure of the infrared light absorbed by the sample. Credit: NIST

The unexpected feature that the team found is known as ferroelasticity—a spontaneous rearrangement of the internal structure of OIPs in which each crystal subdivides into a series of tiny regions, or domains, that have the same atomic arrangement but which are oriented in different directions. This rearrangement creates a spontaneous strain in each domain that exists even in the absence of any external stress (force).

The researchers recently described their work in Science Advances.

See the full article here.

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