Microwave synthesis of size-controllable SnO2 nanocrystals for dye-sensitized solar cells

A microwave hydrothermal synthesis of size-tunable SnO2 nanocrystals is achieved by employing a SnCl4 solution in a mixed ethanol-water solvent. A large increase in ethanol content to over 90%, as well as an increase in SnCl4 concentration, is the key to successfully obtain highly crystallized and well dispersed SnO2 particles as large as 26 nm, which can be determined by XRD and HR-TEM observations. Such well ripened SnO2 crystals exhibit a good performance as photoelectrodes in dye-sensitized solar cells, resulting in an IPCE of around 70% when N719 dye is employed. The size dependent differences in photoelectrochemical properties are studied by SLIM-PCV measurements. The results indicate that fast electron transport occurs with the large SnO2 crystals, owing to their low electron trap density and shallow distribution.