Enhancement in the photovoltaic performance of a dye-sensitized solar cell by an optimized ZnO barrier layer

A dye-sensitized solar cell (DSC) has been considered as a strong alternative to conventional photovoltaic devices based on semiconductors such as silicon or compound semiconductors. The barrier layer functioned by the use of an electrode consisting of two different conduction band potentials is very effective in increasing the photovoltaic performance of a DSC. Especially, zinc oxide (ZnO) is very effective as a barrier layer because it has a higher energy level of the conduction band than TiO₂and good contact with TiO ₂ and dye molecules. We tried to fabricate the ZnO barrier layer using zinc acetate aqueous solution by the dip-coating method, although ZnO film is usually fabricated by chemical vapor deposition or sputter deposition. The experimental parameters were optimized to achieve an effective ZnO barrier layer. The electrochemical impedance spectroscopy and x-ray diffraction pattern were measured to analyze the ZnO layer. The photovoltaic performance of a completed DSC with an optimized ZnO barrier layer was measured and compared with that of a conventional DSC. Consequently, a DSC with a ZnO barrier layer had an increased V_OC up to 0.85 V and an enhanced efficiency of 4.05%.