A microwave hydrothermal synthesis of size-tunable SnO 2 nanocrystals is achieved by employing a SnCl 4 solution in a mixed ethanol-water solvent. A large increase in ethanol content to over 90%, as well as an increase in SnCl 4 concentration, is the key to successfully obtain highly crystallized and well dispersed SnO 2 particles as large as 26 nm, which can be determined by XRD and HR-TEM observations. Such well ripened SnO 2 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 SnO 2 crystals, owing to their low electron trap density and shallow distribution.

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