NOVELTY - A photosensitizing transition metal complex is new.    USE - For photovoltaic cell, e.g. solar cell.    ADVANTAGE - The inventive metal complex improves the efficiency, durability and stability of dye sensitized nanocrystalline solar cell.    DETAILED DESCRIPTION - A photosensitizing transition metal complex of formula MLY1 is new.    M = Ru(II), Os(II), Fe(II), Re(I), or Te(I);    L = polypyridine ligand (II);    A1-A3 = -COOH, -COO N(C4H9)4, -PO(OH)2, -PO(OR1)2, -CO(NHOH), H, 1-50C alkyl, 2-50C alkylamide, or 7-50C aralkyl;    R1 = 1-30C alkyl;    Y1 = group (IIIa)-(IIId);    R3 = 1-50C alkyl, 2-30C alkoxyalkyl, 1-30C aminoalkyl, 2-20C alkoxycarbonyl, 2-30C alkylamide, cyano, or H.    INDEPENDENT CLAIMS are also included for:    (1) a photovoltaic cell comprising a support (8), a conductive layer formed on the support, and a porous semiconductor layer (3) formed on the conductive layer, a counter electrode (6), and an electrolyte deposited where the porous semiconductor layer carries a photosensitizing transition metal complex;    (2) a photosensitive transition metal complex of formula MLX3;    (3) a photosensitive transition metal complex of formula MLY2X;    (4) a photosensitive transition metal complex of formula MLY3X; and    (5) a photosensitive transition metal complex of formula MLY4X.    M, L = as previously defined;    X = ligand selected from NCS-, CL-, Br-, I-, CN-, NCO-, H2O, pyridine which may be substituted by vinyl, primary, secondary or tertiary amino, alkylthio, arylthio, hydroxyl, or 1-30C alkyl; and    Y2 = group of formula (IVa-1);    Y3 = group of formula (IVa-2);    Y4 = group selected from formulae (IVb-1 to 3), (IVc-1 to 4), (IVd-1 to 8), and (IVe-1 to 2);    R4, R5, R6 = 1-20C alkyl, 2-12C alkoxyalkyl, 1-12C aminoalkyl, 2-6C alkoxycarbonyl, 2-30C alkylamide, 1-12C perfluoroalkyl group, 1-6C alkoxy group, aryl, cyano, hydroxy, nitro, amino, trifluoromethane, halogen, or hydrogen;    R7 = 1-12C trifluoro or perfluoroalkyl group;    R8 and R9 = same as defined for R5 and R6; and    R10 to R17 = 1-20C alkyl, 1-12C alkoxyalkyl, 2-12C perfluoroalkyl, 2-12C alkylamide, 1-12C aminoalkyl, 2-6C alkoxycarbonyl, 1-6C alkoxy, 6-12C aryl, cyano, hydroxy, nitro, amino, trifluoro, halogen or hydrogen.    DESCRIPTION OF DRAWING(S) - The figure is a diagrammatic sectional view showing the structure of a solar cell.    Porous semiconductor layer (3)    Hole transporting layer (4)    Counter electrode (6)    Support (8)    Counter electrode side (9)