Solid-state photoswitching molecules: structural design for isomerization in condensed phase

Abstract

Photoswitching dynamics of common organic photoisomers in solid state are often reduced compared to the solution state due to the close packing of molecules that limits structural changes. The facile solid-state switching of photoisomers has implications in developing novel light-controlled devices such as actuator, field-effect transistor, and photodetector, as well as photon energy storage materials that can be charged by light and release thermal energy upon triggering. Thus, the solid-state photoswitching of organic molecules has been studied in relation to the structural characteristics, and various effective methods to enhance the switching in condensed phases have been developed. This review highlights isomerization dynamics of common photoswitches in solid and then introduces important strategies for facilitating the switching dynamics, including the covalent functionalization methods for small-molecule photoswitches as well as the incorporation of various templates such as porous medium, nanoparticle, and host-guest structure. Furthermore, the solid-state switching of molecules at the interface with inorganic substrates including 2D materials and the microscopy techniques for the characterization will be further described. (C) 2020 The Author(s). Published by Elsevier Ltd.