Ag2Se quantum dots for photovoltaic applications and ligand effects on device performance

Highlights: • Ag₂Se quantum dots were considered as a promising blocking layer material in DSSCs. • Bifunctional ligands played a determined role in well loading of Ag₂Se QDs. • Electron transport and recombination in device were improved by ligands. • Photovoltaic performance of solid-state DSSCs was improved by incorporating ligands. In this paper, solid state dye-sensitized solar cells (DSSCs) with Ag₂Se quantum dots (QDs) blocking layer are reported, three different bifunctional linker molecules such as mercaptopropionic acid (MPA), thioglycolic acid (TGA) and cysteine have been used to cap on TiO₂ to link Ag₂Se quantum dots. The linker molecule play a determinant role in well coverage loading of Ag₂Se QDs and improve electron transport and recombination in device. The Ag₂Se QDs can serve both as light absorber and charge blocking layer in device. The power conversion efficiency can be effectively enhanced and the highest one (4.38%) is achieved based on TiO₂/cysteine/Ag₂Se photoanode, showing 45% enhancement compared to that of the controlled one (3.03%).