A new ionic liquid (IL) 5-mercapto-1-methyltetrazole 1-methyl-3-propylimidazolium salt PMIT with di-5-(1-methyltetrazole) disulfide （T2） as the organic redox couple is adopted for application in IL dye-sensitized solar cells (DSSCs). Adopting ultralow-cost and superior catalytic ink carbon as the counter electrode (CE), the N719- and D102-sensitized devices show high efficiencies of 4.30% and 3.83% under 100 mWcm-2 light illumination, respectively. Electrochemical studies provide insights on the mass-transfer and recombination kinetics of the electrolyte and electrochemical catalysis of the CE. The ink carbon CE exhibits more excellent catalytic activity than the Pt CE for the redox couple. These show an attractive prospect of carbon materials for application in DSSCs based on new iodine-free ionic liquid organic electrolyte.