Photosensitive perovskites change shape when exposed to light

August 28, 2017, King Abdullah University of Science and Technology
The perovskite material changes size when exposed to light. Credit: WILE, VCH Verlag GmbH & Co.

A crystalline material that changes shape in response to light could form the heart of novel light-activated devices. Perovskite crystals have received a lot of attention for their efficiency at converting sunlight into electricity, but new work by scientists at KAUST shows their potential uses extend far beyond the light-harvesting layer of solar panels.

Photostriction is the property of certain materials to undergo a change in internal strain, and therefore shape, with exposure to light. Organic photostrictive materials offer the greatest shape change so far reported in response to light—a parameter known as their photostrictive coefficient—but their response is slow and unstable under ambient conditions.

KAUST electrical engineer Jr-Hau He and his colleagues have looked for photostriction in a new family of materials, the perovskites. "Perovskites are one of the hottest optical materials," says He. His work now shows there's more to their interesting optical properties than . The researchers tested a called MAPbBr3 and revealed it had strong and robust photostriction behavior.

To extensively test the material's photostriction capabilities, the team developed a new method. They used Raman spectroscopy, which probes the molecular vibrations within the structure. When bathed in light, photostriction alters the internal strain in the material, which then shifts the internal pattern of vibrations. By measuring the shift in the Raman signal when the material was placed under mechanical pressure, the team could calibrate the technique and so use it to quantify the effect of photostriction.

"We demonstrated that in situ Raman spectroscopy with confocal microscopy is a powerful characterization tool for conveniently measuring intrinsic photoinduced lattice deformation," says Tzu-Chiao Wei, a member of the team. "The same approach could be applied to measure photostriction in other materials," he adds.

The perovskite material proved to have a significant photostriction coefficient of 1.25%. The researchers also showed that the perovskite's photostriction was partly due to the photovoltaic effect—the phenomenon at the heart of most solar cell operation. The spontaneous generation of positive and negative charges when the perovskite is bathed in light polarizes the material, which induces a movement in the ions the material is made from.

The robust and stable photostriction of perovskite makes it useful for a range of possible devices, says Wei. "We will use this material to fabricate next-generation optoelectronic devices, including wireless remote switchable devices and other -controlled applications," he says.

Explore further: Flatter materials have fewer imperfections, which makes for better solar cells and light sensors

More information: Tzu-Chiao Wei et al, Photostriction of CH3 NH3 PbBr3 Perovskite Crystals, Advanced Materials (2017). DOI: 10.1002/adma.201701789

Related Stories

Revealing the microscopic mechanisms in perovskite solar cells

March 21, 2017

A material with the perovskite crystal structure has become very popular for solar cells. While most perovskites are inorganic compounds, this new material is a hybrid of relatively inexpensive organic and inorganic materials. ...

Semi-transparent perovskite solar cells for solar windows

May 22, 2017

Scientists are exploring ways to develop transparent or semi-transparent solar cells as a substitute for glass walls in modern buildings with the aim of harnessing solar energy. But this has proven challenging, because transparency ...

Solar cells with nanostripes

May 2, 2017

Solar cells based on perovskites reach high efficiencies: They convert more than 20 percent of the incident light directly into usable power. On their search for underlying physical mechanisms, researchers of the Karlsruhe ...

Recommended for you

New study explores cell mechanics at work

June 19, 2018

It's a remarkable choreography. In each of our bodies, more than 37 trillion cells tightly coordinate with other cells to organize into the numerous tissues and organs that make us tick.

The secret to measuring the energy of an antineutrino

June 18, 2018

Scientists study tiny particles called neutrinos to learn about how our universe evolved. These particles, well-known for being tough to detect, could tell the story of how matter won out over antimatter a fraction of a second ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.