NOVELTY - Sodium carbonate and sodium bicarbonate are mixed to prepare sodium carbonate-sodium bicarbonate buffer solution. Nano titanium dioxide and the buffer solution are mixed, ground to obtain titanium dioxide suspension. Polyelectrolyte is mixed with the buffer solution to obtain polyelectrolyte solution. A conductive glass substrate is soaked in the suspension, removed, cleaned, dried, soaked in the polyelectrolyte and finished a layer of static self-assembly. The titanium dioxide and polyelectrolyte are assembled and roasted to obtain titanium dioxide film.    USE - Preparation of titanium dioxide film used for solar cell electrode.    ADVANTAGE - The method provides titanium dioxide film having uniform and flat surface, large porosity and specific surface and precise thickness with improved cell stability, pigment adsorption amount and light absorption efficiency, without cracking and peeling of film.    DETAILED DESCRIPTION - Sodium carbonate (0.1 mol/L) and sodium bicarbonate (0.1 mol/L) are uniformly mixed in the volume ratio of 1:10-10:1 to prepare sodium carbonate-sodium bicarbonate buffer solution (0.1 mol/L). The pH of the obtained solution is adjusted to 8-12. Nano titanium dioxide and sodium carbonate-sodium bicarbonate buffer solution are uniformly mixed in the weight ratio of 1:50-1:100, ground for 20 minutes completely, ultrasonic dispersion is carried out for 30 minutes and pH is regulated to 8-12 under stirring to obtain titanium dioxide suspension. Polyelectrolyte is mixed with the buffer solution in the weight ratio of 12:1-16:1, and pH is regulated to 4-6 to obtain polyelectrolyte solution. A clean conductive glass substrate is soaked in the titanium dioxide suspension for 1-10 minutes, removed, cleaned for 3 times through deionized water, blown and dried, soaked in the polyelectrolyte for 5 minutes, removed, cleaned for 3 times through deionized water, blown and dried, and finished a layer of static self-assembly. The soaking, cleaning and drying process are repeated. The titanium dioxide and polyelectrolyte are alternately assembled to the conductive glass substrate through static adsorption force till obtaining a thick titanium dioxide film. The obtained film is roasted at 300-800 degrees C for 20-120 minutes to obtain titanium dioxide film.