Direct aqueous synthesis of quantum dots for high-performance AgInSe 2 quantum-dot-sensitized solar cell

Abstract

Abstract Compared to the use of an organic system, a synthetic method based on aqueous solutions offers the potential for simple, environmentally friendly, low-cost fabrication with high synthetic reproducibility and easy upscaling. Here, AgInSe 2 quantum dots (QDs) capped with different types of thiol molecules [thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), or glutathione (GSH)] are prepared within 15 min in aqueous media under microwave irradiation. The GSH-stabilized AgInSe 2 QDs are demonstrated to be effective light harvesters in a QD-sensitized solar cell (QDSSC), showing ∼23% better efficiency than cells using TGA- and MPA-stabilized AgInSe 2 QDs. The performance enhancement is attributed to the multidentate chelating effect of the GSH stabilizer, which provides efficient charge injection from QDs into the conduction band of TiO 2 in the photoanode. Electrochemical impedance spectroscopy and intensity-modulated photocurrent spectroscopy/intensity-modulated photovoltage spectroscopy measurements are adopted for more detailed study of the interfacial properties and electron transport characteristics of these AgInSe 2 QDSSCs. More importantly, the GSH-stabilized AgInSe 2 QDSSC with TiCl 4 treatment exhibits an excellent power conversion efficiency of 5.69% with an average value of 5.48 ± 0.19% under 100 mW cm −2 illumination, which is one of the highest values observed for a QDSSC sensitized with a Ag-based metal chalcogenide.