NOVELTY - Ruthenium complex photosensitizer dye is new.    USE - Ruthenium complex photosensitizer dye of (1) useful for dye-sensitized solar cell (claimed).    ADVANTAGE - The ruthenium complex photosensitizer dye of (1) has absorption spectrum, which is close to the solar light spectrum; and very high absorption coefficient, providing dye-sensitized solar cell, which can effectively absorb solar light and convert it into an output current. The energy level of highest occupied molecular orbital and lowest unoccupied molecular orbital of the photosensitizer dye is compatible well with the oxidation potential of the electrolyte and conduction band of anode in dye-sensitized solar cell. Thus, the dye-sensitized solar cell has higher photoelectric conversion efficiency than the conventional dye-sensitized solar cell.    DETAILED DESCRIPTION - Ruthenium complex photosensitizer dye of formula (1) is new.    X1=one of 18 groups, e.g. formulae (2)-(4);    X2=H;or    X1, X2=both represent one of 18 groups, e.g. formulae (2)-(4);    R1-R7, R20, R22=H, CtH2t+1, OCvH2v+1, SCwH2w+1, -O-CH2-(CH2-O-CH2)r-CH2-O-R59 (36), or -CH2-O-CH2-(CH2-O-CH2)r-CH2-O-R60 (37);    a, b, d, i, j, k, t, v, w, x, y=1-15;    n=0-2;    m=1-4;    Y1=S, CH2, N-R, or Se;    R=H or CxH2x+1;    Y2=one of 18 groups, e.g. -H, -CiH2i+1, -O-CjH2j+1, -S-CkH2k+1, formula (36), or formula (37);    R59, R60=H or CjH2j+1;    r=0-6;    Z1=one of 7 groups, e.g. -COOA1, -PO3HA1, or -CH=CH-COOA1;    Z2=H or one of 7 groups, e.g. -COOA1, -PO3HA1, or -CH=CH-COOA1;    A1=H, Li, Na, K, tetra-alkyl ammonium groups of formula R66-(R63)N(+)(R65)-R64 (45), or any species or groups with positive charge;    R63-R66=H or CyH2y+1;    R48-R51=H, CaH2a+1, OCbH2b+1, SCdH2d+1, formula (36), or formula (37);and    q=1-3.    When Z1 and Z2 both represent -COOA1, X1 represents formula (2) or (3), n in formula (2) or (3) represents 0, Y1 in formula (2) or (3) represents S, and X2 represents H or the same group as X1; then Y2 does not represent one of -H, -CiH2i+1, or -O-CjH2j+1 or group of formula (31), but merely represents one of 8 groups, e.g. -S-CkH2k+1 or one of 6 groups, e.g. group of formula (32). When Z1 and Z2 both represent -COOA1, X1 represents formula (4), n in formula (4) represents 0, Y1 in formula (4) represents S, R3 in formula (4) represents H, and X2 represents H or the same group as X1; then Y2 does not represent one of -H, -CiH2i+1, or -O-CjH2j+1, but merely represents one of 15 groups, e.g. -S-CkH2k+1. When Z1 and Z2 both represent -COOA1, X1 represents formula (5), n in formula (5) represents 0, Y1 in formula (5) represents S, R4-R7 in formula (5) represents H, and X2 represents H or the same group as X1; then Y2 does not represent one of -H, -CiH2i+1, or -O-CjH2j+1, but merely represents one of 15 groups, e.g. -S-CkH2k+1. When Z1 and Z2 both represent -COOA1 in which A1 represents H, X1 and X2 both represent formula (10) or (12), n is 0, and Y1 represents S; then Y2 in formula (10) or (12) does not represent one of -H, -CiH2i+1, -O-CjH2j+1, -S-CkH2k+1, but merely represents one of 14 groups, e.g. group of formula (24).