A p-type NiO conducting film for an organic solar cell, a preparation method thereof, and an organic solar cell using the same and having enhanced power conversion efficiency, are provided, wherein the NiO conducting film is fabricated by vacuum sputtering in which nickel or nickel oxide is used as a target material, and argon, oxygen or the mixed gas of the argon and the oxygen is supplied. The p-type NiO conducting film may be easily prepared by vacuum sputtering, and since a n-type conducting film is prepared by simply coating sol-phase precursor solution, the NiO conducting film and the organic solar cells having the NiO conducting film in the order of the NiO conducting film, a photoactive layer, and a n-type conducting film, have enhanced electric energy conversion. As a result, the provided disclosure is useful particularly when applied in organic solar cells and organic light emitting devices.