Researchers at the University of California, Davis have identified surprising properties in a type of material known as perovskite that could pave the way for a new generation of optically controlled semiconductor devices. Their findings were published on March 3. advanced materialsshow that halide perovskite crystals can change shape when exposed to light and then return to their original shape.
Perovskites are a type of semiconductor, but they behave very differently from traditional materials such as silicon and gallium arsenide. These can be made from a mixture of organic and inorganic ingredients and are often cheaper to produce. These differences make them particularly attractive for next-generation technologies.
“These are ‘smart materials’ that can be tuned to respond to stimuli in ways that we can control,” said Marina Leite, professor of materials science and engineering at the University of California, Davis, and senior author of the paper. “Their chemistry is very different in ways that could be beneficial for creating devices that we couldn’t build before.”
All perovskites share a common structure known as ABX3. At the atomic level, this can be visualized as a central atom surrounded by an octahedron (two pyramids attached to the base) formed by six atoms. All of these atoms are enclosed within a cube with an atom in each corner. Because of this structure, perovskites are already widely explored for use in optoelectronics and cutting-edge solar cells.
Light causes rapid and reversible crystal changes
To investigate how these materials react to light, graduate student Mansha Dubey illuminated perovskite crystals with laser light and used X-ray measurements to observe how their atomic structure changed. The crystals themselves were created by collaborators Bekir Tuledi, Andriy Kanak, and Professor Maksim Kovalenko from Switzerland’s ETH Zurich.
Experiments revealed that when a crystal is exposed to light, its internal lattice changes rapidly. When the light is removed, the structure returns to its original configuration. This cycle can be repeated many times.
“When you shine light on it, you see a dramatic change in the lattice, which is a unique phenomenon not seen in silicon or gallium arsenide,” Leite said. This photostrictive effect is reversible and can be repeated over and over again, she said.
Adjustable response depending on light and configuration
One of the most promising aspects of perovskites is their flexibility. By adjusting the chemical composition, scientists can control the wavelengths of light that a crystal absorbs and emits, a property known as its bandgap. Different compositions respond differently to light, especially at frequencies above the bandgap.
The researchers also discovered that they could tune the strength of the shape change. Both the color and intensity of the light affect how strongly the material reacts.
“This is not a binary on/off effect; it can be a scaled response, like a dimmer, depending on the light shining on it,” she said.
To devices and new technologies that control light
This ability to use light to precisely control how a material changes shape could lead to new types of devices. Leite suggests that perovskites could be used in sensors and actuators that are activated or regulated by light instead of electricity.
This research was supported by the Defense Advanced Research Projects Agency program focused on developing materials for switchable photonic devices and the National Science Foundation. The team also utilized the Advanced Materials Characterization and Testing (AMCaT) Laboratory at the University of California, Davis, which was established with support from NSF.
