Dye-sensitized Solar Cell (DSC) is a new generation solar cell with promising for low cost clear renewable energy. Ruthenium complexes were the best sensitizers amongst all types of molecules used for DSC. Molecular design of ruthenium complex for high efficiency DSC is an active research area. A heteroleptic ruthenium complex, coded CYC-B6S, which incorporating an antenna carbazole moiety in the ancillary ligand was used as a typical example to demonstrate the strategy of molecular design. CYC-B6S exhibits the lower energy MLCT band centered at 548 nm with a molar absorption coefficient of 1.61 × 104 M-1 cm-1. Solution state cell based on CYC-B6S show a conversion efficiency of 9.72%. 3.5% was achieved with all-solid state device based on CYC-B6S. Flexible DSCs sensitized with CYC-B6S has an efficiency of 3.8% at TiO2 thickness as small as 6.0 μm.