2-(Thiophen-2-yl)thiazole was introduced as a π-bridge into diethylamino coumarin and novel coumarin sensitizers were synthesized with cyanoacrylic acid or rhodanine acetic acid as electron acceptor. Their light-harvesting capabilities and photovoltaic performance were investigated and compared with those of a similar sensitizer bearing a phenylthiophene bridge. Replacement of benzene in the π-bridge with a thiazole ring contributes to the improvement of the light-harvesting capability and hence superior J_SC. 7-Diethylamino coumarin dye with a 2-(thiophen-2-yl)thiazole bridge and cyanoacrylic acid acceptor shows the most efficient photoelectricity conversion efficiency which has the maximum value of 4.78% (V_OC = 690 mV, J_SC = 9.79 mA cm⁻², and ff = 0.71) under simulated AM 1.5 G irradiation (100 mW cm⁻²).