Self-Healing Nanomaterials

Self-Healing Nanomaterials for Use in Solar Panels and Other Electronic Devices

Self-repairing robots and devices are commonplace in science fiction films. In reality, wear and degradation reduce the efficiency of electronic devices until they need to be replaced. A cracked smartphone screen that heals overnight or solar panels powering satellites that continuously repair damage from micro-meteorites? The field of self-healing materials is expanding rapidly, and what once seemed like science fiction could soon become reality thanks to researchers at Technion - Israel Institute of Technology, who are developing environmentally friendly nanocrystal semiconductors capable of self-healing. Findings recently published in Advanced Functional Materials describe the process by which a group of materials called double perovskites demonstrate self-healing properties after suffering damage from electron beam radiation. Perovskites, first discovered in 1839, have attracted the attention of researchers due to their unique electro-optical properties that make them highly efficient in energy conversion despite their low production cost. Special efforts have been made to use lead-based perovskites in high-efficiency solar cells. Professor Yehonadav Bekenstein from the Faculty of Materials Science and Engineering and the research group at the Solid State Institute at Technion are seeking green alternatives to toxic lead and engineered lead-free perovskites. The team specializes in the synthesis of nano-scale crystals of new materials. By controlling the composition, shape and size of the crystals, they alter the physical properties of the materials. Nanocrystals are the smallest material particles that remain naturally stable. Their size makes certain properties more pronounced and enables research approaches such as imaging using electron microscopes to observe how atoms move in materials—approaches impossible with larger crystals. This was actually the methodology that led to the discovery of self-healing in lead-free perovskites. Perovskite nanoparticles were produced in Prof. Bekenstein's laboratory using a short and simple process involving heating the material to 100°C for several minutes. Doctoral students Sasha Khalfin and Noam Veber examined the particles using a transmission electron microscope and discovered the exciting phenomenon. The high-voltage electron beam used by this type of microscope caused defects and holes in the nanocrystals. The researchers were then able to discover how these holes interacted with the surrounding material and how they moved and transformed within it. They observed that the holes moved freely within the nanocrystal but avoided the edges. The researchers developed code that analyzed dozens of videos obtained using electron microscopy to understand the movement dynamics within the crystal. They found that holes formed on the surface of the nanoparticles and were subsequently transported to energetically stable regions inside. It was hypothesized that the reason for the inward movement of holes was organic molecules coating the surface of the nanocrystals. After removing these organic molecules, the group discovered that the crystal spontaneously expelled the holes to the surface and returned to its original undamaged structure—in other words, the shell healed itself. This discovery is an important step in understanding the processes that enable perovskite nanoparticles to heal themselves and paves the way for their incorporation into solar panels and other electronic devices. Prof. Yehonadav Bekenstein completed his education in Physics and Chemistry at the Hebrew University of Jerusalem. Following a postdoctoral fellowship at the University of California, Berkeley, he joined the Technion faculty in 2018. He has received numerous awards including the Käte and Franz Wiener Prize (Outstanding Doctoral Thesis Award), the Rothschild Fellowship for postdoctoral researchers, and the Alon Outstanding Faculty Integration Fellowship. In 2020, he was awarded an ERC Starting Grant for early-career scientists.

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Materials provided by Technion - Israel Institute of Technology. Journal Source: Sasha Khalfin, Noam Veber, Shaked Dror, Reut Shechter, Saar Shaek, Shai Levy, Yaron Kauffmann, Leonid Klinger, Eugen Rabkin, Yehonadav Bekenstein. Self‐Healing of Crystal Voids in Double Perovskite Nanocrystals Is Related to Surface Passivation. Advanced Functional Materials, 2021; 2110421 DOI: 10.1002/adfm.202110421 Technion - Israel Institute of Technology. "Self-healing nanomaterials usable in solar panels and other electronic devices." ScienceDaily. www.sciencedaily.com/releases/2022/01/220103104609.htm (accessed 4 January 2022).