Carbon Nanotube/Manganese Oxide Thin Film Composites-Based Counter Electrode for Dye-Sensitized Solar Cell

Abstract

Manganese oxide thin film sandwiched between carbon nanotubes thin films-coated on fluorine-doped tin oxide (FTO/CNT/MnOx/CNT) was used as a counter electrode of dye-sensitized solar cell (DSSC) for performance improvement. The multi-layer electrodes were fabricated by sequential process comprising doctor-blade coating of CNT layer and the following electroplating coating of MnOx layer and subsequent doctor-blade coating of CNT layer once again. The multi-layered counter electrode of CNT/MnOx/CNT exhibited the improved conversion efficiency and a fill factor of 2.01±0.01% and a fill factor of 0.55±0.01, respectively, due to an increase in capacitance of the electrode. Electrochemical impedance spectra (EIS) show that the capacitance of multi-layered CNT/MnOx/CNT electrode increased from 22±3 mF to 41±2 mF comparing to that of a monolayer of CNT. Furthermore, EIS of FTO/CNT/MnOx/CNT-based DSSC shows the smallest radius of the semicircle with a charge transfer resistance of 42 Ω, implying a quick redox reaction between counter electrode and electrolyte. The improved fill factor is likely due to the role of MnOx that increases the capacitance of electrode and reduces electron transfer rate from counter electron to electrolyte.