TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Components: The semiconductor is titanium oxide. The semiconductor layer is a semiconductor particle layer subjected to calcination process, and the sensitizing dye is dye particles supported by semiconductor particles. The semiconductor particle layer has a porosity of 10 vol.% or less. Preferred Definitions:    R3 = H; and    X = carboxyl or sulfo (both preferred), sulfino, sulfinyl, phosphoryl, phosphinyl, phosphono, phosphonyl, or sulfonyl or its salt.    WIDER DISCLOSURE - The 3,5-dihydro-imidazol-4-one compound (I) is also disclosed as new.    SPECIFIC COMPOUNDS - The use of 285 compounds (I) is disclosed e.g. (4-(1-(4-((4-(2-carboxymethylsulfanyl-5-oxo-1,5-dihydro-imidazol-(4Z)-ylidenemethyl)-phenyl)-(4-(2,2-diphenyl-vinyl)-phenyl)-amino)-phenyl)-meth-(Z)-ylidene)-5-oxo-4,5-dihydro-1H-imidazol-2-ylsulfanyl)-acetic acid, (4-(1-(4-((4-(2-carboxymethylsulfanyl-5-oxo-1,5-dihydro-imidazol-(4Z)-ylidenemethyl)-phenyl)-(4-((E)-2-phenyl-2-p-tolyl-vinyl)-phenyl)-amino)-phenyl)-meth-(Z)-ylidene)-5-oxo-4,5-dihydro-1H-imidazol-2-ylsulfanyl)-acetic acid, (4-(1-(4-((4-(2-carboxymethylsulfanyl-5-oxo-1,5-dihydro-imidazol-(4Z)-ylidenemethyl)-phenyl)-(4-(2,2-di-p-tolyl-vinyl)-phenyl)-amino)-phenyl)-meth-(Z)-ylidene)-5-oxo-4,5-dihydro-1H-imidazol-2-ylsulfanyl)-acetic acid, (4-(1-(4-((4-(2-carboxymethylsulfanyl-5-oxo-1,5-dihydro-imidazol-(4Z)-ylidenemethyl)-phenyl)-(4-((E)-2-(2,4-dimethyl-phenyl)-2-phenyl-vinyl)-phenyl)-amino)-phenyl)-meth-(Z)-ylidene)-5-oxo-4,5-dihydro-1H-imidazol-2-ylsulfanyl)-acetic acid and (4-(1-(4-((4-(2-carboxymethylsulfanyl-5-oxo-1,5-dihydro-imidazol-(4Z)-ylidenemethyl)-phenyl)-(4-((E)-2-(3,4-dimethyl-phenyl)-2-phenyl-vinyl)-phenyl)-amino)-phenyl)-meth-(Z)-ylidene)-5-oxo-4,5-dihydro-1H-imidazol-2-ylsulfanyl)-acetic acid of formula (Ia).    EXAMPLE - An acetic acid solution containing 4-((4-((E)-2-(3,4-dimethylphenyl)-2-phenyl-vinyl)phenyl)-(4-formylphenyl)amino)benzaldehyde, thiohydantoin (3 equivalents) and ammonium acetate (10 equivalents) was stirred at 120 degrees C for 2 hours. The resultant reaction solution was added with water, then subjected to extraction with ethyl acetate. The extracted material was washed with water, dried with magnesium sulfate, concentrated and dried in a rotary evaporator, and further processed with a silica column, to give (5E)-5-((4-((4-((E)-2-(3,4-dimethylphenyl)-2-phenyl-vinyl)phenyl)-(4-((Z)-(5-oxo-2-thioxo-imidazolidin-4-ylidene)methyl)phenyl)amino)phenyl)methylene)-2-thioxo-imidazolidin-4-one. Bromoacetic acid (3 equivalent) and potassium hydroxide (9 equivalent) were added to an ethanol solution of (5E)-5-((4-((4-((E)-2-(3,4-dimethylphenyl)-2-phenyl-vinyl)phenyl)-(4-((Z)-(5-oxo-2-thioxo-imidazolidin-4-ylidene)methyl)phenyl)amino)phenyl)methylene)-2-thioxo-imidazolidin-4-one and stirred at 70 degrees C for 1 hour. The resultant solution was concentrated and dried in a rotary evaporator, then added with water and ethyl acetate, and then an organic layer was removed with a separating funnel and worked up to give (4-(1-(4-((4-(2-carboxymethylsulfanyl-5-oxo-1,5-dihydro-imidazol-(4Z)-ylidenemethyl)-phenyl)-(4-((E)-2-(3,4-dimethyl-phenyl)-2-phenyl-vinyl)-phenyl)-amino)-phenyl)-meth-(Z)-ylidene)-5-oxo-4,5-dihydro-1H-imidazol-2-ylsulfanyl)-acetic acid.