NOVELTY - Phenothiazine dye compounds (I) are new.    USE - (I) are useful for preparing dye sensitized solar cells (claimed).    ADVANTAGE - (I) have strong ability to capture light in visible light region, and improve photoelectric conversion efficiency of dye-sensitized solar cells.    DETAILED DESCRIPTION - Phenothiazine dye compounds of formula (I) are new.    R1, R2 = H, 1-20C straight or branched alkyl, 1-20C amide, 1-20C alkoxy or halo;    m = 1-6;    Ar1 = aryl, substituted 1,4-phenylene moiety of formula (II), 9H-fluorene-2,7-diyl moiety of formula (III), benzo(c)(1,2,5)thiadiazol-4,7-diyl moiety of formula (IV), thiophen-2,5-diyl moiety of formula (V), furan-2,5-diyl moiety of formula (VI) or pyrrrol-2,5-diyl moiety of formula (VII);    X1-X4 = H, 1-20C straight or branched alkyl, 1-20C amido group, 1-20C alkoxy or halo;    X5, X6 = H, 1-20C straight or branched alkyl, or 1-20C alkoxy; and    X7, X8 = H, 1-20C straight or branched alkyl or halo.    INDEPENDENT CLAIMS are also included for:    (1) use of (I) in a dye-sensitized solar cells comprising light anode, photocathode and light anode substrate, the photocathode substrate and electrolyte composition, employing the light anode substrate and the photocathode substrate as conductive glass, the light anode substrate is provided with nanoporous titania film in one side of the conductive glass and soaking in phenothiazine dye (I), the photocathode substrate is provided with catalyst platinum layer in one side of the conductive glass, setting space between the light anode and photocathode relatively, and sealing the surrounding of intermediate nanoporous titania film with a sealing material to form closed cavity, where the cavity is filled with electrolyte; and    (2) preparing the dye-sensitized solar cells comprising taking conductive glass, absolute ethanol and de-ionized water in degreasers, cleaning by using ultrasonic wave and then drying for further use, (ii) stirring 10ml titanium tetrabutoxide and 20ml ethanol mixed solution at room temperature, adding 18 ml acetic acid and 50 ml de-ionized water in the obtained solution and stirring for 1 hour, and then transferring the mixed solution into an autoclave and processing for 12 hours at 230 degrees C, cooling to room temperature, filtering the suspension, then washing with de-ionized water and ethanol sequentially for many times, baking in an oven at 50 degrees C for 6 hours until to dry to obtain titania nanocrystalline particles having size of 20 nm, (iii) taking 1 g titania nanocrystalline particles, 8 ml ethanol, 0.2 ml acetic acid, 3 g terpineol and 0.5 g ethyl cellulose and grinding the mixture thoroughly for 40 minutes, and then subjecting slurry to ultrasonication for 15 minutes to obtain white viscous titania nanocrystalline slurry, (iv) placing screen plate on top of the conductive glass maintaining 1cm distance, printing titania nanocrystalline slurry on the screen plate, baking the each printed titania films at 125 degrees C for 5 minutes in oven and volatilizing organic solvents, where the thickness of single printed titania films is 4 mu , and repeating many times until to get titania films having thickness of 16 mu m, placing the titania films in a muffle furnace and processing at 325 degrees C and baking for 5 minutes, 375 degrees C for 5 minutes, 450 degrees C for 15 minutes, 500 degrees C for 15 minutes sequentially at different temperatures, immersing the baked titania film in 0.04 M aqueous titanium tetrachloride solution at 70 degrees C for 30 minutes, washing the titania film with deionized water repeatedly, then again placing in muffle furnace, heating to 520 degrees C and baking for 30 minutes, then cooling to room temperature, placing in a sealed bag and storing desiccator and further use, (v) dissolving (I) in tetrahydrofuran and dichloromethane to obtain dye solution having concentration of 5x 10-4 mol/litre, (vi) mixing 0.6 M 1-methyl-3-propyl imidazolium iodide prepared from acetonitrile, valeronitrile, 0.1 M guanidine thiocyanate and 0.03M iodine and 0.5 M tert-butyl pyridine solution to obtain electrolyte solution, (vii) dipping the photoanode nanoporous titania thin film layer obtained in the step (iv) in dye solution obtained in the step (v) to obtain light-sensitized anode, (viii) dissolving chloroplatinic acid hexahydrate in isopropanol solution to obtain formulation having concentration of 5x 10-3 M, dropping on clean conductive glass surface, scrolling the solution with glass rod to get uniform coated surface, drying naturally, and placing in a muffle furnace and sintering for 15 minutes under 400 degrees C, where platinum is deposited on the conductive glass surface due to thermal decomposition, cooling, removing, cutting into set up size and soaking in absolute ethanol, and further use, and (ix) covering titania electrode with platinum electrode and fixing the both sides with clamps, and testing openness sensitized dye solar cell, then injecting electrolytic solution obtained in the step (iv) where the no air bubbles are present between the electrodes and sealing to obtain dye-sensitized solar cell.