Light Absorption Coefficients of Ionic Liquids under Electric Field

Ionic liquids have attracted a lot of research attention for their applications in novel optoelectronic structures and devices as an optical means of regulating electricity. Although the electro-optic effect of ionic liquids is mentioned in some literature, a quantitative testing and analysis are hardly found in light absorption coefficients of ionic liquids under an electric field. In the present study, an experimental apparatus was designed to measure the absorption coefficients of ionic liquids under different electric fields. Five groups of imidazole ionic liquids were experimentally investigated and an inversion was performed to determine the spectral absorption coefficients of the imidazole ionic liquids under electric fields. Different intensities with multiple interface refractions and reflections were also considered, and the various measurement errors were analyzed through uncertainties propagation analysis. Spectral absorption of ionic liquids from 300 nm to 2500 nm was obtained and the absorption coefficients were retrieved. It was found that the absorption behavior of ionic liquids changed in some frequency bands under an applied electric field. The experimental results showed that the absorption coefficient of the ionic liquid increases with the voltage at 1520nm and 1920nm. The change rate was affected by the types of anions and cations in the ionic liquid and the diffusion rate of the ions therein. This study provides illustrations for the ionic liquid-based electro-optical regulation in terms of physical property parameters and the testing technique.