NOVELTY - Substituted carboxylic acid dye compounds (I) comprising a chromophore to which an acyloin group is attached are new.    USE - (I) are useful: in an electronic device (which is a solar cell, preferably a dye-sensitized solar cell); as sensitizer in a dye-sensitized solar cell; and as a photosensitizer in a photocatalytic process (photocatalyzed hydrogen production and photocatalytic degradation of organic pollutants). (I) are useful in solar cell panels for or incorporated in mobile phones, notebooks, laptops, portable audio-tape players, MPEG-1 audio layer 3 (MP3)-players, remote controls, e-cards, e-books, e-readers, portable compact disc-players, portable DVD-players, cameras, digicams, global position system devices, portable sensors, displays integrated in electronic devices, portable solar chargers for batteries of the above devices, smart windows and on-roof applications (preferably in areas where a grid connection is not possible, e.g. camping cars and boats).    ADVANTAGE - (I): are improved ones with intense absorption in the visible and long wavelength region of the solar spectrum; can be easily covalently attached to nanocrystalline wide band gap semiconductors (TiO2 and SnO2); allows an efficient charge transfer from the dye to the semiconductor; and are easily accessible due simple methods of preparation. (I) exhibits high quantum efficiency.    DETAILED DESCRIPTION - Substituted carboxylic acid dye compounds (I) of formula (II) or (III) comprising a chromophore to which an acyloin group is attached are new, where the chromophore is an organic or metal-organic compound absorbing electromagnetic radiation of 300-1200 nm, or a subrange of it, preferably 350-500 nm, 500-750 nm or 350-700 nm.    A = phenyl, biphenyl or heteroaryl (all optionally substituted), H, cyclic or acyclic alkyl, -(CH2)n1-R, -((CR=CR)n1-(CH2)n2)p-R, -((CC)n1-(CH2)n2)p-R, -((CH2)n1-(X)n2)p-R, halo (F, Cl, Br or I), moieties containing heteroatoms (NO2, CN, NR2 or -OH) or moieties forming a ring structure with the acyloin group;    n1, n2 = 0-12, preferably 0-4;    p = 0-6, preferably 0-2;    X = -CR2, O, S, NR or -CR;    R = H, alkyl chain of formula (-C nH2n+1, -COOR1, -OR1, -SR1, -N(R1)2, F, Cl, Br, I, O, N , NO2, CN or CF3;    R1 = phenyl, biphenyl or heteroaryl (all optionally substituted), H or alkyl chain of formula (-CnH2n+1); and    n = 0-12, preferably 0-6.    An INDEPENDENT CLAIM is also included for an electronic device comprising (I).