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