TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: In the step (a), the calcining is carried out at 200-600 degrees C for less than 200 minutes. In the step (b), the impregnation process is carried out at 20-28 degrees C for less than 60 minutes. In the step (c), the impregnation process is carried out at 30-50 degrees c for 1-180 minutes. Preferred Components: The metal oxide nanoparticle includes tin oxide, antimony-, niobium- or fluorine-doped tin oxide, indium oxide, tin-doped indium oxide, zinc oxide, aluminum-, boron-, gallium-, hydrogen-, indium-, yttrium-, titanium-, silicon- or tin-doped zinc oxide, magnesium oxide, cadmium oxide, magnesium-zinc oxide of formula (MgZnO), indium-zinc oxide of formula (InZnO), the copper-aluminum oxide, silver oxide, gallium oxide, zinc tin oxide of formula (ZnSnO), titanium dioxide and zinc indium-tin oxide (ZnInSnO), nickel oxide, rhodium oxide, ruthenium oxide, iridium oxide, copper oxide, cobalt oxide, tungsten oxide, titanium oxide, zirconium oxide, strontium oxide, lanthanum oxide, vanadium oxide, molybdenum oxide, niobium oxide, aluminum oxide, yttrium oxide, scandium oxide, samarium oxide and/or strontium-titanium oxide of formula (SrTiO).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The average particle diameter of the metal oxide nanoparticle is 10-100 nm. The pH value of the acidic aqueous solution is 1-5. The acidic aqueous solution includes hydrochloric acid, sulfuric acid, phosphonic acid, acetic acid and/or nitric acid. The solvent in the acidic aqueous solution includes distilled water or ethanol. The acidic aqueous solution is sodium nitrate aqueous solution. The band gap of the photosensitive dye solution is 1.55-3.1 eV. The photosensitive dye solution comprises metal or metal complex including organic-inorganic complex dyes (ruthenium-, osmium-, platinum-, copper-, porphyrin- and phthalocyanine-based dye), organic dyes (coumarin-, indoline-, carbazole-, triarylamine-, parylene-, hemocyanin-based and squalene-based dye) or their mixtures. The solvent in the photosensitive dye solution comprises ethanol, acetonitrile, tetrahydrofuran and/or dimethyl chloride. EXAMPLE - Metal oxide nanoparticle paste (7.3 wt.% titanium oxide nanoparticles, 0.05 wt.% ethyl cellulose and remaining amount of terpineol) was coated on 100 nm titanium oxide thin film (obtained by spin coating 0.15 M titanium diisopropoxide bis(acetylacetonate) on a conductive glass substrate and heat treating at 450 degrees C) and calcined at 500 degrees C for 30 minutes to obtain porous film. The obtained porous film was impregnated with nitric acid aqueous solution (prepared by diluting 0.1 M nitric acid with distilled water and stirring for 30 minutes until the pH value reaches 1) for 20 minutes, filled with nitrogen gas and dried at 40 degrees C. The resulting substrate was impregnated with the photosensitive dye solution (prepared by dissolving ruthenium complex dye of formula (NaRu(4-carboxylic acid-4'-caboxylate) (4,4'-dinonyl-2,2'-bipyridine) (NCS)2) with ethanol to a concentration of 2 mM) for 20 minutes to obtain the photo-electrode.