Co-solvent effects on the morphology of P3HT:PCBM thin films

► We investigate P3HT:PCBM films using co-solvents of chlorobenzene and toluene. ► The choice of solvents is based on their close boiling points and on different polarities. ► The result points out the key role of the PCBM solubility on the film organization. ► P3HT regioregularity has no influence on morphology with dominant chlorobenzene solvents.