ZnO QDs were successfully synthesized by using a simple synthetic route. The synthesized ZnO QDs have different shapes with highly crystalline nature and their size was found to be ca. 3–5 nm. At the same time, a series of modified N719 dyes were obtained via ion-exchange reactions and characterized by FTIR and HRMS measurements. When the modified N719 dyes were used as a sensitizer for ZnO QDs-based flexible solar cells, the photovoltaic properties were enhanced significantly. A highest efficiency of 2.94% was achieved; this might be attributed to the fact that the aggregate of Zn2+/dye on the surface of ZnO QDs can be suppressed efficiently owing to a less carboxylated (COOH) bipyridyl ligand in the modified N719 dye, inhibiting the formation of chelation between ZnO QDs and dye.
