Analysis of AC Impedance in Localized Region Using Magnetic Field Distribution Measured by HTS-SQUID

Estimation of ac impedance in a localized region was investigated by measuring the magnetic field from an electrical current induced by applying an ac voltage to a sample. For this measurement, a high-temperature-superconductor superconducting quantum interference device (HTS-SQUID) was used to detect a small magnetic field from a sample. To clarify the detection of ac impedance in a localized region, a dye-sensitized solar cell (DSSC) with a positive electrode consisting of two catalysis materials was prepared. Although the I-V characteristic and electrochemical impedance spectroscopy (EIS) of the solar cell with two catalysis materials were different from those of the solar cell with a one catalysis material, it was difficult to evaluate the ac impedance of the localized region. The magnetic field from the solar cell with two catalysis materials depended on the measurement position at which the catalysis material located under HTS-SQUID was different. This difference was correlated to the ac impedance change predicted by the measured EIS. Moreover, the mapping obtained by magnetic field distribution near the interface of two catalysis materials showed a different magnetic field intensity, which was correlated to the position of each catalysis material. These results indicate that the analysis of the localized ac impedance is possible using the magnetic field distribution generated from a sample.