CityU researchers show off a photodetector constructed with the morphed perovskites. Photo: City University of Hong Kong.
CityU researchers show off a photodetector constructed with the morphed perovskites. Photo: City University of Hong Kong.

A research team co-led by scholars from City University of Hong Kong (CityU) has shown that all-inorganic perovskites can be deformed and morphed at room temperature without compromising their functional properties. Their findings, reported in a paper in Nature Materials, demonstrate the potential of this class of semiconductors for manufacturing next-generation deformable electronics and energy systems in the future.

All-inorganic lead halide perovskites are becoming increasingly important semiconducting materials in energy conversion and optoelectronics because of their outstanding performance and enhanced environmental stability.

“However, unlike metal materials or polymers, inorganic semiconductors are often brittle and hard to process,” said Chen Fu-Rong, associate vice-president (mainland collaboration) and professor of materials science at CityU, who co-led the study. “This strongly restricts their applications as optoelectronic products that must withstand mechanical stress and strain without losing their functionality.”

To overcome this limitation, Chen and his research team explored the deformability of an all-inorganic perovskite (CsPbX3, where X can be chlorine, bromine or iodine ions). They found that perovskites can be substantially morphed into distinct geometries at room temperature while preserving their functional properties, an achievement unprecedented in conventional inorganic semiconductors.

In their experiments, the team using the vapour-liquid-solid method to synthesize single-crystal micropillars of CsPbX3 with diameters and widths ranging from 0.4μm to 2μm and lengths ranging from 3μm to 10μm. They then conducted in situ compression experiments with a scanning electron microscope.

These revealed that, under compression, there were continuous slips of partial dislocations on multiple slip systems in the CsPbX3 crystal lattice. This ‘domino-like’ multi-slipping deformation mechanism allowed the micropillars to deform into various distinct shapes without fracturing, including an upside-down L shape, a Z shape and a wine-glass shape.

With the aid of an atomic-resolution transmission electron microscope (TEM), the team discovered that the atoms in the deformation zone were well connected, leading to undamaged functional properties. “We also observed that the optoelectronic performance of the micropillars remained unaffected by the deformation,” said Johnny Ho Chung-yin, associate head and professor in the Department of Materials Science and Engineering (MNE) at CityU. “This demonstrates the potential of these materials for use in deformable optoelectronics.”

The research team performed further electronic and structural analyses to uncover the physical origin of this unusual behaviour. “The secret of the morphing ability is the low-slip energy barrier, which ensures facile slips, and the strong Pb–X bonds, which maintain the crystal’s structural integrity and prevent cracking or cleaving,” said Zhao Shijun, who specializes in the properties of computational materials at MNE. And the bandgap – an energy index influencing the total electrical properties of intrinsic semiconductors – of the CsPbX3 crystal lattice remained unchanged after deformation, indicating that the electronic structure of the material was unaffected.

“Our results demonstrated that all-inorganic CsPbX3 single crystals can be substantially deformed and facilely morphed into various shapes through multi-slipping under ambient conditions, without changing their crystalline integrity, lattice structure or optoelectronic properties,” said Chen.

“This achievement represents a significant step towards designing and manufacturing innovative energy devices and deformable electronics. The underlying mechanism, uncovered by a TEM at the atomic level provides important implications for seeking other intrinsic ductile semiconductors.”

This story is adapted from material from City University of Hong Kong, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.