Theoretical Study on the Effects of External Electric Field on Nonlinear Optical Properties of Azobenzene

ABSTRACT With the development of nonlinear optical switch, the potential of photochromic molecules and their modification gained concerns, especially electric field is believed as effective stimuli for modulating molecular electronic structures and properties. In this work, the electric field was applied to explore its effect on azobenzene, and the results revealed pronounced direction‐ and conformation‐dependent responses of azobenzene to the applied fields. In the aspect of effect of field direction, the properties of N═N bond, the isomerization process, the polarized charge distribution, as well as nonlinear optical properties would be influenced more by x ‐ or y ‐axis fields. In comparison, the effect of the field along the z ‐axis was little despite nonplanarity in the trans conformation was observed. On the other hand, the cis and trans isomers exhibited distinctions in various aspects. For the cis conformation, the molecular structure, UV–vis absorption spectra, and the first‐order hyperpolarizability were mainly influenced by the field along the x ‐axis. For the trans conformation, these properties were greatly influenced by the field along the y ‐axis. Especially, the field parallel to the y ‐axis markedly enhanced the switch efficiency. This work demonstrated the role of the electric field as a tool for modulating the optoelectronic responses of azobenzene and provided a strategy for tuning molecular optical properties.