Ag₂Se quantum dots (QDs) was synthesized by co-deposition method which was further applied as co-sensitizer in solid-state dye-sensitized solar cells (DSSCs). The effects of different sensitization methods of Ag₂Se QDs (TiO₂/N719/QDs, TiO₂/QDs/N719) and sensitization time (0-5 h) on the performance of QDs/dye co-sensitized solar cells were studied. Structure and optical properties of Ag₂Se QDs were characterized by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy (UV-Vis). Furthermore, the transmission of charge carriers of solar cell devices was characterized by photo-modulated photocurrent/voltage spectrum (IMPS/VS) and electrochemical impedance spectra (EIS). It was found that the device with TiO₂/QDs/N719 showed higher incident photon-to-current efficiency (IPCE) and photoelectric efficiency than those of TiO₂/N719/QDs, which was due to the fact that TiO₂/QDs/N719 photoanode adsorbed more QDs and dyes. With the extension of Ag₂Se QDs sensitization time, the photovoltaic properties of DSSCs firstly ascended and then descended, achieving the highest photoelectric conversion efficiency 3.97%. The incorporation of Ag₂Se QDs could effectively promote the electron transport and inhibit the electron-hole recombination, which benefited from a blocking layer that QDs served in device. As sensitization time prolonged over 2 h, the photovoltaic performances of device deteriorated, which was attributed to the augmented trap sites in Ag₂Se QDs layer.