Pulse-Reversal Deposition of Cobalt Sulfide Thin Film as a Counter Electrode for Dye-Sensitized Solar Cells

In this study, cobalt sulfide (CoS) thin film was electrochemically deposited on a transparent conducting glass substrate in a neutral aqueous by means of a simple pulse-reversal (PR) deposition technique, and employed as a counter electrode (CE) for dye-sensitized solar cells (DSCs) for the first time. Initially, extensive electrochemical measurements were conducted to investigate the deposition mechanism for the proposed PR deposition mode and determine the suitable pulse potentials. When compared to the conventional potentiostatic (PS) deposition mode, the proposed PR deposition mode can facilitate the formation of single-component CoS with granular morphology. Moreover, the effects of the parameters in the PR mode, including duty cycle and pulse frequency, on the electrocatalytic activity for I 3 − reduction were investigated. After the optimization, the CoS PR CE at duty cycle of 0.1 and pulse frequency of 1/30 Hz showed the most excellent electrocatalytic activity for I 3 − reduction among all electrodeposited-CoS CEs. The DSC with the CoS PR CE exhibits an impressive cell efficiency of 5.48%, which is much better than that of the DSC with CoS PS CE (2.13%) and comparable to that of the DSC using Pt CE (5.50%).