Abstract Three new metal-free dyes with a 5, 6-bis (octyloxy) benzo [c][1, 2, 5] thiadiazole core (DOBT-I–III) have been designed and synthesized for use as DSSCs. Their absorption properties and electrochemical and photovoltaic performances have been investigated systematically. The DSSCs based on DOBT-I–III show high open-circuit voltages (V oc) of 829, 818, and 784 mV, respectively. Of the three dyes, DOBT-III, which contains a ...