Mass transport effect on the photovoltaic performance of ruthenium-based quasi-solid dye sensitized solar cells using cobalt based redox couples

• The effect of different quasi-solid cobalt electrolytes in Ru-based DSSCs was studied.
• Significant efficiency improvement is observed under low light condition.
• The established dye Z907 reached an efficiency of 5.2% for [Co(dtb)3]3+/2+ electrolyte under 0.29 sun.
• Negligible mass transport limitation observed for [Co(bpy)3]3+/2+ electrolyte.
• Gel electrolytes sustained 100% photocurrent of the liquid electrolyte under low light.

Dye-sensitized solar cell (DSSC) technology is a promising solution to global energy and environmental problems. However, device stability and long-term durability are still significant issues in the commercial application of DSSC. Quasi-solid-state polymer electrolytes can be used in DSSCs in order to overcome various problems associated with liquid electrolytes. In this work we have studied the effect of mass transport on the photovoltaic performance of established ruthenium sensitizers (N719 and Z907) in DSSCs using the series of cobalt (II/III) quasi-solid electrolytes based on the poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) polymer. The [Co(bpy)3]3+/2+ electrolyte showed better mass transport among all electrolyte systems examined. The DSSCs employing Z907 sensitizer exhibit significantly enhanced photovoltaic performances, in which a better power conversion efficiency of 4.34% was obtained from [Co(bpy)3]3+/2+ redox mediator under 1 sun condition. The Z907 device efficiency significantly increased to 5.2% (2.66% under 1 sun) and sustained 100% photocurrent of the liquid electrolyte for [Co(dtb)3]3+/2+ redox couple under 0.29 sun condition.