The characterization of nanocrystalline dye-sensitized solar cells with flexible metal substrates by electrochemical impedance spectroscopy

Metal substrates are excellent alternatives to conducting plastic substrates in flexible solar cells because of the possible sintering process at high temperature. However, the investigation of cells with flexible metal substrates has only recently started with titanium, tungsten, and stainless steel. It was found that they formed semiconductor oxides after the sintering process. In this paper, we probed the properties of dye sensitized solar cells with the metal substrates prepared in three different ways-a bare metal sheet, indium tin oxide (ITO) sputter coating on a bare metal sheet, and ITO sputter coating after the addition of a SiOx layer on the metal sheet. The best cell efficiency was obtained from the cell with bare Ti because it formed a TiO2 layer which was identical to the main working electrode. When an ITO layer was added, fill factors (FFs) increased for W and SUS 304 and FF decreased for Ti; the addition of a SiOx layer led to a short circuit current increase and FF decrease. Electrochemical impedance spectroscopy was taken and analyzed to characterize the resistance element in each circuit, and the corresponding effects were discussed. A new impedance element resulting from the SiOx insulating layer was classified from electrochemical impedance spectroscopic data.