The effect of solvents on the morphology of a 1:1 (w/w) poly(3-hexylthiophenes) (P3HT) : [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blended with and without aryl halide as an additive. The P3HT:PCBM active layer in the polymer solar cell structure was prepared by spin-coating using a solvent from a selection of chlorobenzene, 1,2-dichlorobenzene and chloroform. For all samples, the P3HT:PCMB molar ratio was 1:1 and 10 mg of the additives in 1 ml of solvent, while the films with the 1,3,5-trichlorobenzene (TCB) additive were prepared at the concentration of 12 mg of P3HT:PCBM in 1 ml of TCB. Optical absorption spectroscopy measurements of the films indicated shifts in absorption peaks in the range from 500-600 nm which are attributed to P3HT. The shifts were observed only for the chloroform solvent, which has the lowest boiling point out of the three. By contrast, chlorobenzene and 1,2-dichlorobenzene provided merely a gradual increase of the peak intensities. Topographic images obtained by the Atomic Force Microscope (AFM) of the P3HT:PCBM layers with and without aryl halide as the additive were founded to have the highest surface roughness with the usage of chloroform solvent in both cases. This roughness was mentioned as the self-organization signature of the P3HT materials [1]. In addition, the effect of co-solvents on the distribution of P3HT and PCBM in the films was also investigated by two methods: (1) by dissolving out the PCBM and (2) by using the AFM phase imaging mode. The latter was found to be more informative, yielding both the crystallinity and the P3HT:PCBM distribution of the films. The results show that the chloroform solvent does not only produce more ordering in the P3HT but also provide a more uniform phase-separated distribution of P3HT:PCBM. This type of structure is expected to be favorable for applications in high performance polymer solar cells.