Preparation of highly stable TiO2 sols and nanocrystalline TiO2 films via a low temperature sol–gel route

Highly stable TiO2 sols were prepared by adjusting the water-to-titanium molar ratio to ~4 in the process of hydrolysis and condensation of titanium isopropoxide in ethanol with HNO3. Particularly, long-term stable TiO2 sols were prepared without adding any chemical additives. Anatase TiO2 nanocrystallites with sizes of 3–5 nm in diameter were uniformly dispersed in the stable sol. Crystallized TiO2 films were successfully deposited on Si (100) using the stable sol via a dip-coating process with low temperature curing at as low as 100 °C. The synthesized TiO2 sols and films are promising for use in flexible or dye-sensitized solar cells.