A hydrophobic fluorinated polymer material, polyvinylidenefluoride (PVDF), was used as an interlayer between the poly-3,4-ethylenedioxythiophene:polystyrenesulfonate and poly(3-hexylthiophene)(P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) active layers in organic solar cells (OSCs). The PVDF interlayer increased the short circuit current and improved the power conversion efficiency of the OSCs. The PVDF interlayer induced extensive crystallization of the P3HT:PCBM active layer during thermal treatment, which was responsible for the high short circuit current and power conversion efficiency.