Hydrothermal synthesis of TiO2 colloids is based on hydrolysis and pressure treatment of titanium isopropoxide precursor in acidic solutions. The influence of the use of nitric and acetic acids during the synthesis was studied, showing a significant effect on the colloid crystal structure. Both dark-field TEM and phase transformation temperature measurements indicate that the colloids prepared in acetic acid contain more of the {101} face compared with the colloids prepared in nitric acid. The surface structure difference affects the performance of dye-sensitized solar cells that consist of electrodes made from these colloids. Better performance is achieved using the colloids prepared in nitric acid, indicating the importance of controlled colloid fabrication for higher conversion efficiencies.