Exploring the use of impedance spectroscopy in relaxation and electrochemical studies

Impedance spectroscopy involves the application of a small amplitude AC voltage to electrode, and probing in/out of current phase as a function of frequency. It is a powerful tool to characterize the physical properties on the dynamics of immobile and mobile charge carriers, including molecular/collective dipolar fluctuations, charge transport and polarization effects at the boundary, in molecular systems. This review first discusses the development of impedance spectroscopy technique to cover the broad frequency range from mHz to GHz. Subsequently, we devoted to introduce the recent advances in impedance spectroscopy with an emphasis on its novel applications to relaxation characterization in glass-forming system, electronic/ionic charge transfer characterization in dye-sensitized solar cells and impedance biosensors.