High‐Performance Platinum‐Free Dye‐Sensitized Solar Cells with Molybdenum Disulfide Films as Counter Electrodes

By using a radio‐frequency sputtering method, we synthesized large‐area, uniform, and transparent molybdenum disulfide film electrodes (1, 3, 5, and 7 min) on transparent and conducting fluorine‐doped tin oxide (FTO), as ecofriendly, cost‐effective counter electrodes (CE) for dye‐sensitized solar cells (DSSCs). These CEs were used in place of the routinely used expensive platinum CEs for the catalytic reduction of a triiodide electrolyte. The structure and morphology of the MoS₂ was analyzed by using Raman spectroscopy, X‐ray diffraction, and X‐ray photoemission spectroscopy measurements and the DSSC characteristics were investigated. An unbroken film of MoS₂ was identified on the FTO crystallites from field‐emission scanning electron microscopy. Cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel curve measurements reveal the promise of MoS₂ as a CE with a low charge‐transfer resistance, high electrocatalytic activity, and fast reaction kinetics for the reduction of triiodide to iodide. Finally, an optimized transparent MoS₂ CE, obtained after 5 min synthesis time, showed a high power‐conversion efficiency of 6.0 %, which comparable to the performance obtained with a Pt CE (6.6 %) when used in TiO₂‐based DSCCs, thus signifying the importance of sputtering time on DSSC performance.