Fabrication of a ZnO film with a mosaic structure for a high efficient dye-sensitized solar cell

A flexible photoanode with zinc oxide film on titanium foil was prepared and its application in a dye-sensitized solar cell (DSSC) was investigated. The ZnO film with a mosaic structure, composed of densely packed ZnO nanosheets (ZnONS), was obtained by calcining a film of layered hydroxide zinc carbonate (LHZC), which was previously grown directly on a Ti foil via chemical bath deposition (CBD). The highly porous ZnONS film with a film thickness of about 25 mu m could be facilely prepared within 4 h under CBD conditions. Owing to the intrinsic properties of the ZnONS film, i.e., high porosity, high surface area, and effective electron transport, a solar-to-electricity conversion efficiency (eta) of 5.41% was achieved for the pertinent back-illuminated DSSC, which is the highest ever reported value for a back-illuminated DSSC based on a ZnO photoanode. The effect of the sputtering time of platinum (Pt) and iodine concentration on the photovoltaic performance of the DSSC were also investigated. Films on the substrates were characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Transmission spectra were obtained to characterize Pt films. Electrochemical impedance spectra (EIS) were obtained to analyze the charge transfer resistance and Warburg diffusion process in the DSSCs. Incident photon-to-current conversion efficiency (IPCE) curves were used to support the behavior of short-circuit photocurrent (J(SC)) of DSSCs and also to calculate its values. Electron lifetimes in photoanodes were determined using Bode-phase plots.