Facile synthesis of Ag2Se quantum dots and their application in Dye/Ag2Se co-sensitized solar cells

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 μm) 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.