Balance between the charge transfer resistance and diffusion impedance in a CNT/Pt counter electrode for highly efficient liquid-junction photovoltaic devices

Abstract

Abstract This study investigates changes in the charge transfer resistance (Rct) and diffusion impedance (Zw) according to the thickness of a CNT/Pt layer coated onto an FTO glass counter electrode (CE) to improve the photovoltaic performance of dye-sensitized solar cells (DSCs). For this purpose, we carefully controlled the thickness of the CE by using different amounts of CNT/Pt in the paste. Note that both Rct and Zw decrease with an increase in the thickness of the CEs. Power conversion efficiencies of 7.77, 8.21, 7.58 and 7.36% are determined for DSCs with thicknesses of the CNT/Pt layer of 1, 3.2, 10 and 18 μm, respectively. The obtained results are in good agreement with the changes in the ratio of Rct/Zw. When the ratio of Rct/Zw becomes one and the Rct value is less than 1 Ωcm2, the device shows the best performance. Because this strategy is simple and effective, it can be useful for developing cost-effective CE materials for DSCs.