Described herein are D-π-A type sensitizers of the formula (I) or (II) having a novel central π-conjugated unit di-thiazolyl-benzodiazole and dye-sensitized electrodes including a substrate having an electrically conductive surface, an oxide semiconductor film formed on the conductive surface, and the above sensitizer of formula (I) or (II), as specified above, supported on the film. A solar cell includes the above electrode, a counter electrode, and an electrolyte deposited there between. The sensitizers of formula (I) and (II) efficiently sensitize the semiconductor materials and show a high solar to electricity conversion efficiency.