A dye sensitized solar cell, comprising a-heteroleptic polypyridil complex of Ru, Os or Fe. The donating ligand has an extended conjugated n-system increasing the light absorbance and keeing the LUMO energy level higher than that of the anchoring ligand. A compacting compound whose molecular structure comprises a terminal group, a hydrophobic part and an anchoring′ group may be co-adsorbed together with the dye on the semi-conductive metal oxide layer of the photoanode, forming a dense mixed self-assembled monolayer.