We report that microwave (MW) treatment of binder-free TiO2 paste coating is a facile method that can replace energy- and time-consuming high-temperature sintering processes in the production of mesoporous electrodes in dye-sensitized solar cells. For example, 5 min of MW treatment at 110 W is sufficient to produce a device with ∼4% efficiency. Conventional sintering at 375 or 450 °C for ∼2 h is required to make devices with a comparable efficiency. Compatibility with common plastic substrates is another advantage of MW-treatment process. Substrate temperature remained below 205 °C after 5 min of MW treatment. Analysis of impedance spectra using equivalent circuit model showed a correlation between device performance and resistances. Specifically, the sum of charge-transfer resistances at TiO2-TiO2 and Pt-electrolyte junctions, the Warburg component, and contact and FTO sheet resistances was in good agreement with the series resistance deduced from the fitting of measured J-V curves to an imperfect diode with parasitic resistances. Moreover, the discrepancy in variations of short-circuit current and charge-transfer resistance in TiO2 electrodes indicated that MW sintering can be effective in reducing charge-transfer resistance without sacrificing dye adsorption.
This work was partly supported by \u2018Human Resources Program in Energy Technology\u2019 of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry and Energy, Republic of Korea (No. 20164030201380), and partly by the GRRC program of Gyeonggi province (GRRC-AJOU2016B03, Photonics-Medical Convergence Technology Research Center).
