NOVELTY - Photosensitizing transition metal complexes (A) are new.    USE - (A) are useful in photovoltaic cell (claimed) such as solar cell.    ADVANTAGE - (A) are photochemically stable, and improve the efficiency, durability and stability of dye sensitized nanocrystalline solar cell.    DETAILED DESCRIPTION - Photosensitizing transition metal complexes (A) of formula (MLY2X) (I) and (MLY3X) (II) are new.    M = transition metal comprising Ru(II), Os(II), Fe(II), Re(I) or Tc(I);    L = polypyridine ligand of formula (a);    A1-A3 = anchoring group comprising -COOH, -COON(C4H9)4, -PO(OH)2, -PO(OR1)2, -CO(NHOH), 1-50C alkyl, 2-50C alkylamide or 7-50C aralkyl;    R1 = 1-30C alkyl;    X = ligand comprising NCS-, Cl-, Br-, I-, CN-, NCO-, H2O or pyridine (optionally substituted by vinyl, primary, secondary or tertiary amino, alkylthio, arylthio, OH or 1-30C alkyl);    Y2 = R4-C(=O)-CH(R5)-C(=O)-R6; and    R4-R6 = 1-20C alkyl, 2-12C alkoxyalkyl, 1-12C aminoalkyl, 2-6C alkoxycarbonyl, 2-30C alkylamide, 1-12C perfluoroalkyl, 1-6C alkoxy, aryl, CN, OH, nitro, amino, trifluoro group, halo or H.    In formula (II),    At least one of A1-A3 = anchoring group comprising -COOH, -COON(C4H9)4, -PO(OH)2, -PO(OR1)2, -CO(NHOH), and when there is the remaining A1-A3 being not the anchoring group, it may be H, 1-50C alkyl, 2-50C alkylamide or 7-50C aralkyl;    Y3 = phenyl group of formula (b);    R7 = 4 trifluoro or perfluoro1-12C alkyl; and    R8, R9 = 1-20C alkyl, 2-12C alkoxyalkyl, 1-12C aminoalkyl, 2-6C alkoxycarbonyl, 2-30C alkylamide, 1-12C perfluoroalkyl, 1-6C alkoxy, aryl, CN, OH, nitro, amino, trifluoro group, halo or H.    An INDEPENDENT CLAIM is included for a photovoltaic cell comprising a support (8), a conductive layer formed on the support, and a porous semiconductor layer formed on the conductive layer, a counter electrode, and an electrolyte deposited between them, where the porous semiconductor layer carries (A).    DESCRIPTION OF DRAWING(S) - The figure shows a diagrammatic sectional view showing the structure of solar cell.    Substrate (1)    Electroconductive film (3) Porous photovoltaic layer (2)    Hole transporting layer (4)    Support. (8)