Preparation of Cauliflower-like ZnO Films by Chemical Bath Deposition: Photovoltaic Performance and Equivalent Circuit of Dye-sensitized Solar Cells

The uniform cauliflower-like ZnO films were deposited on the conducting substrate by a chemical bath deposition in urea/water solution. The film structure and morphology were characterized by X-ray diffraction, thermo-gravimetric differential thermal analysis, energy dispersive spectroscopy, selected area electron diffraction, field emission scanning electron microscopy and high resolution transmission electron microscopy. The average diameter of ZnO nanoparticles and the petal thickness were 25 nm and 8 μm, respectively. Dye-sensitized solar cells based on the cauliflower-like ZnO film electrode showed the short-circuit current density of 6.08 mA/cm2, the open-circuit photovoltage of 0.66 V, the fill factor of 0.55 and the overall conversion efficiency of 2.18%. The equivalent circuit of cells based on the ZnO film electrodes was measured by the electrochemical impedance spectroscopy. Furthermore, the analysis of equivalent circuit provided the relationship between the cell performance and the interfacial resistance, such as the shunt resistance and the series resistance.