NOVELTY - The organic solar cell (10) comprises a cathode (3), an anode (5) disposed opposite to the cathode, a photoactive layer (0.1-50%) disposed between the cathode and the anode, and an electron blocking layer positioned between the anode and the photoactive layer. The photoactive layer comprises: an electron donor (7); an electron acceptor (9); and a hydrophilic nanostructure, which comprises an electron conductive material consisting of a semiconductor element, a semiconductor compound, a semiconductor carbon material and/or a metallic carbon material.    USE - Used as an organic solar cell.    ADVANTAGE - The organic solar cell has an increased amount of photocurrent and improved photoelectric conversion efficiency by improving a moving path of electrons in a photoactive layer, and can be economically and simply manufactured.    DETAILED DESCRIPTION - The organic solar cell (10) comprises a cathode (3), an anode (5) disposed opposite to the cathode, a photoactive layer (0.1-50%) disposed between the cathode and the anode, and an electron blocking layer positioned between the anode and the photoactive layer. The photoactive layer comprises: an electron donor (7); an electron acceptor (9); and a hydrophilic nanostructure, which comprises an electron conductive material consisting of a semiconductor element, a semiconductor compound, a semiconductor carbon material, a metallic carbon material that is surface-treated with a hole blocking material and/or a metal that is surface-treated with a hole blocking material. The nanostructure is physically and electrically connected to the cathode, has an one-dimensional linear structure, a two-dimensional flat structure or a three-dimensional cubic structure and surface roughness, and consists of nanotubes, nanorods, nanowire, nanotrees, nanotetrapods, nanodisks, nanoplates, nanoribbons, and/or a self-assembled monolayer of the hole blocking material on its surface. The semiconductor element, the semiconductor compound, the semiconductor carbon material and the hole blocking material satisfy the equations given in the specification. The semiconductor element, the semiconductor compound and the semiconductor carbon material are surface-treated with the hole-blocking material. The semiconductor compound consists of a group II-VI compound, a group III-V compound, a group IV-VI compound, a group IV compound and/or a semiconductor metal oxide. The semiconductor carbon material and the metallic carbon material that is surface-treated with the hole blocking material consist of carbon nanotubes and/or graphene. The hole blocking material consists of a semiconductor element and/or a semiconductor compound. An INDEPENDENT CLAIM is included for a method of fabricating the organic solar cell.    DESCRIPTION OF DRAWING(S) - The diagram shows a cross-sectional view of an organic solar cell.    Substrate (1)    Cathode (3)    Anode (5)    Electron donor (7)    Electron acceptor (9)    Organic solar cell. (10)