TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No preparation method is given. Preferred Compound: The ruthenium complex photosensitizer dye of (1) is one or more of 16 compounds, e.g. group of formulae (68)-(70). SPECIFIC COMPOUNDS - Ruthenium complex photosensitizer dyes of (1) are disclosed as groups of formulae (Ia)-(Ic).    EXAMPLE - (Ruthenium chloride (RuCl2)(p-cymene))2 (0.4323 g) and 4,4'-bis(5-octyl-2,2'-bithiophen-5-yl)-2,2'-bipyridine (1.0 g) were dissolved in anhydrous dimethyl formamide (DMF) (30 ml). The solution was then heated to 80 degrees C for 4 hours. After this, 4,4'-bis(E-carboxyvinyl)-2,2'-bipyridine (0.4183 g) was added to the solution, followed by heating the solution to 160 degrees C for 4 hours, where reaction was conducted in the dark to prevent the generation of isomers. Excessive amount of ammonium thiocyanate (NH4NCS) was added to the solution, and the reaction was allowed to continue for 5 hours at 130 degrees C. After the reaction completed, the temperature of the solution was returned to room temperature. The solution was concentrated by removing the solvent DMF using a vacuum system, followed by a washing process using respectively deionized water, sodium hydroxide solution at pH 12, and ethyl ether to obtain a solid substance. A crude product was ultimately obtained after vacuum filtration. After dissolving the crude product in methanol and passing the solution through a column (using methanol as eluent), a dark color portion was collected and methanol was removed by rotary evaporation. The resulting black solid substance was purified using ethyl acetate to remove the soluble impurities. Then, acetone was used as solvent to remove the impurities that were dissolvable in acetone. The black solid substance, after being sequentially washed with ethyl acetate and acetone, was dissolved in a mixture solution of methanol and tetra-butyl ammonium hydroxide aqueous solution. The resulting solution then was passed through a column (using Sephadex LH-20(RTM: dextran gel) as packing material), and a darker color portion of the solution was collected. Few drops of 0.01 M nitric acid aqueous solution were added to the solution for adjusting the pH to 3, and a precipitation (formula (Ia)) of 0.69 g was obtained (yield: 40.0%). Result: ruthenium complex photosensitizer dye (position of the longest wavelength absorption peak=562 nm; absorption coefficient of the longest wavelength absorption peak=25100/Mcm); N3 (conventional photosensitizer dye disclosed by M. Gratzel (J. Photochem. A, 2004, 164, 3) and M. K. Nazeeruddin et al. (J. Am. Chem. Soc. 1993, 115, 6382)) (position of the longest wavelength absorption peak=530 nm; absorption coefficient of the longest wavelength absorption peak=14500/Mcm).