Abstract The device performance of the dye-sensitized solar cells (DSSCs) mainly depends on the sensitizers. Ruthenium sensitizers have played a vital role in the DSSCs to improve power conversion efficiency. However, the absorbance spectra of most Ru-sensitizers limited up to 600 nm, which maybe prohibiting further improvement of short-circuit current density (Jsc). To address this problem, TER-HDT was designed and synthesized by incorporating hexyl dithiafulvalene (HDT)-substituted bipyridine as an ancillary ligand and [2,2′:6′,2′'-terpyridine]-4,4′,4′'-tricarboxylic acid as anchoring ligand together. The synthesized TER-HDT was systematically studied and characterized by spectroscopic (proton NMR, Mass analysis), optical (UV-absorbance and photoluminescence), electrochemical and theoretical techniques. The novel sensitizer TER-HDT absorption tailed up to 900 nm, which originated from the enhanced intermolecular charge transfer in conjunction with efficient intra and intermolecular interactions. The HOMO and LUMO energy levels TER-HDT are suitable for electron injection and regeneration which may help to achieve high efficiency.