The performance of organic photovoltaic devices was enhanced by insertion of the photo-crosslinkable buffer layer. This buffer layer was formed by a photo curable precursor with bithiophene and pentadienyl moieties. The fill factor of the device with this buffer layer exceeded 0.7 in the organic photovoltaic cell. The characteristic of the photo-crosslinkable property enabled this buffer layer to be inserted between the hole extraction layer and the active layer, which formed an ohmic contact with both layers. The insertion of the buffer layer induced a 20% enhancement in conversion efficiency by small increases in the short-circuit current and the open-circuit voltage, and a huge increase in the fill factor. This photo-crosslinkable buffer layer acted as a leakage current reducing layer as measured by the reduced dark current. The high crystallinity and smooth surface of this buffer layer resulted in improved surface morphology and internal packing, thus enhanced the fill factor.