NOVELTY - Producing an organic photovoltaic element with an organic photo-active layer (3) comprising a conjugated block copolymer having a polymer A block containing a thiophene group and a polymer B block containing a thiophene group, or a polymer composition containing conjugated polymer A and polymer B, and a fullerene derivative, involves exposing an organic photo-active layer to a vapor of solvent having a surface tension between a surface tension of the conjugated polymer A or polymer B containing a thiophene group and a surface tension of the fullerene derivative.    USE - For producing an organic photovoltaic element (claimed) which is used in an inorganic matter such as monocrystal silicon, polycrystal silicon, amorphous silicon, and compound semiconductor; and also used in solar cell, photovoltaic cell, an electron device e.g. an optical sensor, an optical switch, and phototransistor, and an optical memory.    ADVANTAGE - The method provides organic photovoltaic element having high power conversion efficiency through an economically advantageous and short production process.    DETAILED DESCRIPTION - Producing an organic photovoltaic element with an organic photo-active layer (3) comprising a conjugated block copolymer having a polymer A block containing a thiophene group and a polymer B block containing a thiophene group, or a polymer composition containing a conjugated polymer A having a thiophene group and a conjugated polymer B having a thiophene group, where the difference between the melting points of the polymers is greater than or equal to 10 degrees C, and a fullerene derivative, involves exposing an organic photo-active layer to a vapor of solvent having a surface tension between a surface tension of the conjugated polymer A or polymer B containing a thiophene group and a surface tension of the fullerene derivative.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an organic photovoltaic element.    Substrate (1)    Anode (2)    organic photo-active layer (3)    Cathode (4)