Mo2C microspheres and nanorods as counter electrode catalysts for iodide-free redox couples in dye-sensitized solar cells

Abstract

In this work, molybdenum carbide microspheres (Mo₂C-Ms) and nanorods (Mo₂C-Nr) are synthesized for use as counter electrode (CE) catalysts in dye-sensitized solar cells (DSSCs), specifically towards the regeneration of iodide-free redox couples of T₂/T⁻ and Co^3+/2+. In the T₂/T⁻ based DSSCs, the prepared Mo₂C-Ms and Mo₂C-Nr both show high catalytic behavior, and the devices generate power conversion efficiency (PCE) values of 5.50% (Mo₂C-Ms) and 4.86% (Mo₂C-Nr), respectively, much higher than the Pt CE based counterpart (3.73%). Electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel polarization curve measurements reveal that Mo₂C-Ms also show higher catalytic activity for the Co^3+/2+ redox couple that is competitive with the traditional Pt CE. The device using a Mo₂C-Ms CE achieves a high PCE of 8.70%, indicating great potential to replace the expensive Pt CE.