Electrochemical attenuated total reflectance spectroscopy in far- and deep-ultraviolet regions

Recently, we developed a novel attenuated total reflectance (ATR) spectroscopic system in far- and deep-ultraviolet (FUV and DUV) regions that operates under electrochemical conditions in order to investigate the electronic states of materials near the electrode surface. We succeeded to record the FUV-DUV spectra of various ionic liquids systematically using the ATR-FUV-DUV spectroscopy and theoretically assign the obtained spectra based on quantum chemical calculations. Subsequently, upon application of voltage to an ionic liquid consisting of imidazolium cations and iodide anions, electronic transition spectra in the 150−450 nm range varied. In particular, absorbance due to charge transfer from the anion to the cation drastically increased at positive potentials. According to the molecular dynamics simulations, the density of iodide anion near the electrode surface drastically changed depending on the electrode potential, which contributed to the spectral changes. Now, this technique is applied for organic semiconductor materials.