A high light-harvesting ability heteroleptic ruthenium complex dye, SJW-E1, was examined as a sensitizer for the plastic dye-sensitized solar cells (DSSCs) constructed by a low-temperature electrode preparation method using binder-free TiO2 paste and an ITO-PEN substrate. The effects of a TiO x buffer layer, electrolyte composition and co-adsorbents on the cell performance as well as the cell long-term stability were investigated. The TiOx buffer layer has not only enhanced the adhesion between TiO 2 thin film and the ITO/PEN substrate but also reduced the electron recombination, resulting in the improvement of the fill factor (FF) and therefore the photovoltaic performance of the solar cells. The optimized solar cell based on SJW-E1 dye showed an efficiency of 6.31%. Furthermore, the plastic DSSCs based on the SJW-E1 dye shows a better cell stability compared to that based on N719 dye after a full sunlight soaking (at ca. 50 °C) for 500 h. These results demonstrated that the flexible DSSCs based on the high light-harvesting, well-functionalized heteroleptic ruthenium dye could achieve both high performance and good stability.