NOVELTY - A dye-sensitized solar cells, comprises a metal complex (c1) comprising at least one substituted monopyridine ligand or polypyridine ligand, as a sensitizing-dye, and a cobalt complex, as a redox mediator, where the substituted monopyridine ligand and/or polypyridine ligand comprises at least one substituted aryl group.    USE - As dye-sensitized solar cells (claimed).    ADVANTAGE - The metal complex dye shows superior compatibility with the cobalt complex based redox mediator; and allows the use of cobalt complex as redox mediator in dye-sensitized solar cell (DSSC) system in which metal complex dye molecule is adopted as a sensitizing-dye, without causing a significant decrease in the performance of the system.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) new metal complex of formula ML'1L'2X1X2 (I);    (2) a method of manufacturing the metal complex (I) involving: reacting substituted aryl halide (preferably alkoxy- or thioalkyl-substituted phenyl bromide), with heterocycle-boronic acid (preferably thienyl boronic acid); and    (3) new substituted bipyridine ligand of formula (II1).    M=metal belonging to Group 6, 8, 9, 10 or 11 of the long-format Periodic Table, preferably ruthenium;    X1 and X2=halo, -OH, -CN, -SCN, -NCS, and -NCO;    L'1 and L'2=bipyridine ligand of formula (II);    Het=bridge selected from aromatic amine groups, heteroatoms, alkenyl groups, aryl groups, or heterocycles, preferably thiophene, oligothiophenes, ethylenedioxythiophenes (EDOT), oligo-EDOTs, cyclopentanedithiophenes (CPDT), especially sulfur and thiophene;    Ar1=substituted aryl, preferably alkoxy phenyl or thioalkyl phenyl;    m=0-4;    n=1-4;    R12-R21=H, halo, cyano, alkyl, halogenated alkyl, alkoxy, halogenated alkoxy, aryl, halogenated aryl, aryloxy, halogenated aryloxy, heterocycles, halogenated heterocycles, heterocyclic alkyl, halogenated heterocyclic alkyl, heterocyclic alkoxy, halogenated heterocyclic alkoxy, heterocyclic aryl, halogenated heterocyclic aryl, heterocyclic aryloxy, halogenated heterocyclic aryloxy, amino, halogenated amino, or NO2, preferably alkoxy or thioalkyl.