A series of new organic dyes, 2-(2,6-bis((E)-2-(5 '-hexyl-2,2 '-bithiophen-5-yl)vinyl)-pyran-4-ylidene)-2-cyanoacetic acid (OD-1) and 2,2 '-(2-((E)-2-(5 '-hexyl-2,2 '-bithiophen-5-yl)vinyl)-1H-indene-1,3(2H)-diylidene)bis(2-cyanoacetic acid) (OD-2), were synthesized as a sensitizers for the application of dye-sensitized solar cells (DSSCs). The introduction of the 5 '-hexyl-2,2 '-bithiophene units as an electron donor group and 2,6-dimethyl-pyran-4-one or 1,3-indandione as a pi-spacers units increased the conjugation length of the sensitizers and thus improved their molar absorption coefficient and light harvesting efficiency.