||Well-defined poly(acrylonitrile-co-dimethyl acrylamide)-block-polyethylene oxide-block-poly(acrylonitrile-co-dimethyl acrylamide) with various molecular weights and acrylonitrile/dimethyl acrylamide ratios were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. Solubility and gel formation in liquid electrolytes greatly depend on dimethyl acrylamide content and molecular weight of triblock copolymers. As molecular weight of polymers with lower dimethyl acrylamide content increases, ionic conductivity and diffusion coefficient of polymer gel electrolytes increase. By utilizing ruthenium-based N719 dye, gel-state DSSCs with an efficiency of above 10%, which are comparable to liquid-type DSSC, was achieved. Moreover, the gel-state DSSCs exhibit long-term stability by 1000-hour testing under 1-sun illumination at 50°C. The present polymer gel electrolytes can be considered as alternative of liquid electrolyte used in DSSCs.