We investigated the formation of bilayer inverse opal TiO2 (io-TiO2) structures via post-treatment with a TiO2 precursor solution and characterized the photovoltaic performances of the resulting electrodes for use in dye-sensitized solar cells. The post-treatment of TiO2 inverse opals in a precursor solution grew rutile TiO2 nanoparticles on anatase crystalline phase io-TiO2 surfaces, resulting in anatase/rutile bilayer structures. We achieved a maximum photovoltaic conversion efficiency of 4.6% using a 25 mu m thick electrode formed with the post-treated io-TiO2 under simulated AM 1.5 light. This efficiency represents a 183% improvement over the non-post-treated io-TiO2 electrodes. The shell thickness was controlled by the post-treatment time. The effects of shell thickness on photovoltaic performance were investigated by measuring the morphologies and electrochemical impedance of the post-treated io-TiO2. We found that post-treatment up to a certain period of time increased the surface area and electron lifetime, but further treatment resulted in decreased area and saturated lifetimes. The optimal post-treatment time was identified, and the optimal io-TiO2 electrodes were characterized.