The properties of heterojunction interfaces based on P3HT/PCBM are determined by the substrate work funcition and the charge transfer states according to the integer charge transfer(ICT) model.We fabricate the heterojunction organic photovoltaic devices with P3HT or/and PCBM buffer layer,different from bulk heterojunction devices,and investigate the influence of the added buffer layers on open-circuit voltage and short-circuit current.The results suggest that the buffer layers can significantly enhance the short-circuit current density which increases from 3.96 mA/cm2 to 4.51 mA/cm2 and 4.70 mA/cm2,but have little effect on open-circuit voltage.