Conducting Under UV-Irradiation

Photo­conduction, where an insulating material exhibits a semi­conducting property under photo­irradiation, was found in 1873, and is now applied in various devices including optical sensors, CCD cameras, remote controllers and solar cells. This long-known important pheno­menon has a weak point; it cannot produce high con­duction metallic substances.

A shot of UV light has produced a considerable flow of electric current like spring water in an insulating molecular crystal, which phenomenon originates from the unique original physical properties of this material, realized by the interplay between the two kinds of molecules shown in the image. (Source: T. Naito et al. / RSC)

Metallic conduction is more suitable or advan­tageous for appli­cation in electronic devices, because it consumes less energy than semi­conductors. Now, researchers from the Ehime Uni­versity in Japan have found metal-like conduction behavior in a molecular crystal under UV-irra­diation. This material itself is unique in that, without irradiation, its behavior falls between metals and insulators. However, it turned out to be impossible to make it behave metal­lically in any method other than UV-irra­diation.

Such a material is often metallized by applying high pressure or high tempera­ture, but this was not the case for this parti­cular material. In addition to the newly found metallic photo­conduction, the new finding is important because it indicates that there are other photo­excited states of matter possessing unique properties. In other words, the researchers like to explore the photo­excited states of various materials to find novel properties and functions just as chemists have done for hundreds of years by syn­thesizing new materials. (Source: Ehime U.)

Reference: T. Naito et al.: A possibly highly conducting state in an optically excited molecular crystal, J. Mater. Chem. C 7, 9175 (2019); DOI: 10.1039/C9TC00491B

Link: Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan

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