Electrophoretic deposition of ZnO film and its compression for a plastic based flexible dye-sensitized solar cell

A room temperature fabrication method is developed for the preparation of a ZnO porous film on a plastic substrate, involving an electrophoresis deposition (EPD) process, followed by the compression of the film as the post-treatment. The thus prepared ZnO film is used for the photoanode of a dye-sensitized solar cell (DSSC). Besides, an indoline dye is employed as the sensitizer (referred to as D149) for the ZnO semiconductor. Performances of such DSSCs are studied at various compression pressures used for their ZnO films. Electrochemical impedance spectroscopy (EIS) is employed to quantify the charge transport resistance at the ZnO/dye/electrolyte interface (R_ct2) and the electron lifetime (τ_e) in the ZnO film. As for the thickness effect, ZnO film with a thickness of about 22 μm renders the best efficiency for the ZnO based DSSC. In addition, UV-O₃ is applied in two ways; in one way only the compressed ZnO film is treated in one step, and in the second way both the substrate and the compressed ZnO film are treated separately in two steps. The adherence of the ZnO film is shown by a photograph. Scanning electron microscopy is used to characterize the morphologies of the ZnO films.