We report two novel D-pi-A type organic dyes with a coplanar dithieno[2,3-d; 2',3'-d']benzo[1,2 b;4,5-b']dithiophene (DTBDT) as pi-spacer for dye-sensitized solar cells. A best device performance with a power conversion efficiency of 6.32% is achieved, making DTBDT unit a promising building block for design of organic sensitizers.