We used solvent-vapor treatment method to tailor the nanoscale phase-seperation and thus tailor the charge mobility of the poly(3-hexylthiophene)/fullerene (P3HT/C₆₀) blend films. The nanowires obtained by chloroform vapor treatment are rich in C₆₀, whereas the nanowires obtained by DCB vapor treatment are rich in P3HT. The treated blends offers far superior hole transport than the untreated blends, which is attributed to the nanoscale phase-segregation and a 3-D network contained either C₆₀ or P3HT nanowires. Meanwhile, the electrically bicontinous nanoscale morphology realized by controlling the crystallinity of P3HT and C₆₀ using different solvents vapor results in enhanced absorption in visible light without further heat-treatment or preparation in both cases. Solar cells fabricating from the films after treatment show several-fold improvements in power conversion efficiency compared to devices having films without treatment.