Inorganic iodide ligands in ex situ PbS quantum dot sensitized solar cells with I−/I3− electrolytes

In this paper, inorganic iodide ligands were used in PbS quantum dot sensitized solar cells (QDSCs) with iodide/triiodide electrolytes. Inorganic ligands are employed to replace organic ligands in QDSCs for the first time. They combined effects of passivating surface states and decreasing the interface resistance between QDs and sensitized TiO2, QDs and electrolyte. Then the corrosion of PbS QDs by triiodide in iodide/triiodide electrolytes was suppressed and electron injection and hole transfer was much easier. Stability test verified iodide ligands could prevent PbS from corrosion of iodide/triiodide electrolytes. Electrochemical impedance spectroscopy (EIS) showed that iodide ligands effectively decreased the interface resistance and improved the electron transfer. Finally, the performance with iodide ligands was significantly improved and achieved 3.7 times that of the untreated cells in efficiency.