The present invention provides a process for preparing a photoanode of a dye-sensitized solar cell (DSSC) by pressure swing impregnation, which includes impregnating a metal oxide layer on a conductive substrate in a photosensitizing dye solution in a vessel; introducing a pressurized inert gas into the vessel to maintain a first pressure therein for a period of time, wherein the first pressure can be lower or higher than the critical pressure of the inert gas and the solution is expanded by the inert gas; further pressurizing the vessel with the inert gas and maintaining at a second pressure higher than the first pressure for a period of time, wherein the inert gas becomes sub-critical or supercritical fluid and dissolves more in the solution, creating an anti-solvent effect, so that the photosensitizing dye further deposits onto the metal oxide layer due to the anti-solvent effect. |