In Situ versus ex Situ Assembly of Aqueous-Based Thioacid Capped CdSe Nanocrystals within Mesoporous TiO2 Films for Quantum Dot Sensitized Solar Cells

We report a straightforward in situ deposition method to directly assemble aqueous thioglycolic acid capped CdSe colloidal quantum dots within mesoporous TiO2 thin films by a low-temperature hydrothermal route. This approach integrates linker assisted adsorption and colloidal quantum dot synthesis in a single step due to the use of thioglycolic acid as the capping agent for the quantum dots and tethering agent for the TiO2. It permits high loading and uniform distribution of colloidal quantum dots within mesoporous TiO2 electrodes with a greatly improved photovoltaic performance as quantum dot sensitized solar cells, reaching efficiencies as high as 2.2% under one sun illumination conditions after ZnS treatment, compared to the ex situ assembly technique of adsorption of presynthesized semiconductor nanocrystals.