For the first time, Co-doped CuCrO2+δ non-stoichiometric nanocrystals with δ≈0.1 aresynthesized bylow-temperature hydrothermal method. The synthesis mechanism proposed and the structural characterizations have confirmed that the excess oxygen from delafossite structure is given by the specific hydrothermal conditions (temperature, pressure and molarity of basic solution). The decreasing of the observed electrical resistivity in the non-stoichiometric nanocrystals is enhanced by Co-subtitution. Thus, hydrothermal synthesis has allowed to obtain doped delafossite nanocrystalline compound with excess oxygen and mixed valancies of both sites (A and B sites) and could open the study of its cumulative effect on physical properties. The performance of p-type DSSCs based on Co-doped CuCrO2+δnanocrystals photocathodeswas made using two type of dye: Coumarin C343 and Ruthenium N719. The short-circuit density (Jsc) is notably increased by approximately 60% when N719 is used as dye.