The photovoltaic performance of molybdenum cluster-sensitized solar cells has been explored with the challenge of enhancing their efficiency due to the low charge transfer efficiency. Aromatic sulfonate ligands (NS = naphthalene 2,6-disulfonate = –OSO2–C10H6–SO3–) were now used for the functionalization of the {Mo6Ii8} cluster cores. The new functional [Mo6I8iI3a(H2O)2a(NS)a] cluster unit exhibits enhanced photophysical and photoelectrochemical properties compared to other homologues based on the {Mo6I8i} cluster cores. In greater detail, the role of the NS functional groups was beneficially emphasized for the improved oxidation stability of the cluster in a redox mediator, adjusting the emission lifetime to a suitable range for fast electron injection, and accelerating the charge transport process. The best as-synthesized Mo6 cluster-based solar cell resulted in a stable photocurrent of 2.38 mA cm–2 with a fill factor of 0.63 and the power conversion efficiency of 0.97% under an AM 1.5 illumination, a two times’ enhancement in comparison to the reference iodide Mo6 cluster-based cell (0.52%). Specific attention focused on the increase of the power conversion efficiency up to 1.18% after 330 s and then reached the saturation trend. The enhanced charge transfer of the metal cluster complex was obtained from facile modifications of the functional apical ligands that result in advantageous photophysical and electrochemical characteristics, specializing in optoelectronic devices. This study provides the general methodology and knowledge for the next improvement of the photovoltaic efficiency of the Mo6 cluster-based sensitized solar cells.