Overpotential modification at the MoS₂ counter electrode/electrolyte interfaces by thermal annealing resulting improvement in photovoltaic performance of dye-sensitized solar cells

The application of molybdenum sulfide (MoS₂) to dye-sensitized solar cells (DSSCs) as a counter electrode (CE) has been reported. However, CE possessing both high electrical conductivity and excellent electrocatalytic activity is indispensable for DSSCs and it is still unclear how much of power conversion efficiency increase in the present case is due to each of these two components. The effect of thermal annealing on the MoS₂ counter electrode in DSSCs is investigated. The experimental results revealed that the MoS₂ crystallinity influences on the power conversion efficiency by controlling the overpotential for an electron transferring from the MoS₂ CE to the electrolyte that serves to change the short circuit current. This understanding can provide guidance for the development of highly efficient DSSCs with platinum-free CEs.