Silver selenide (Ag2Se) quantum dots (QDs) with uniform size have been synthesized via a facile and low-cost method. The Ag2Se QDs are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-Vis-NIR spectrophotometer. Uniform Ag2Se QDs with average particle size of 4.8-5.8 nm and good dispersity can be prepared in the pH (value) of 10.5 and reaction time of 10-90 min. The Ag2Se QDs with average particle size of 4.8 nm have a direct band gap of 1.5 eV and can enhance the light absorption property of Dye/TiO2 photoanode. The fabricated Dye/Ag2Se co-sensitized solar cell exhibits a photocurrent density of 8.25 mA cm(-2) and a power conversion efficiency of 3.23%, which is higher than that of dye-sensitized solar cell (3.51 mA cm(-2) and 1.32%). The intensity-modulated photocurrent/photovoltage spectroscopy shows that the charge diffusion length is improved (31 mu m) for the Dye/Ag2Se co-sensitized solar cells. This improvement may be due to the enhanced electron transport and reduced electron recombination processes in the dye-sensitized solar cells after decorating with Ag2Se QDs.