NOVELTY - The organic heterojunction solar cell comprises a first electrode (2) and a second electrode (5), an electrically active layer (4) disposed between the first and second electrodes and comprising an organic p-type semiconductor material and a n-type carbon semiconductor material, and an additional layer (7) disposed between the first electrode and the electrically active layer in direct contact with the active layer. The additional layer comprises a compound forming non-covalent interactions with the n-type carbon semiconductor material.    USE - Used as an organic heterojunction solar cell.    ADVANTAGE - The organic heterojunction solar cell exhibits improved photocurrent density, good conversion efficiency and high performance and stability.    DETAILED DESCRIPTION - The organic heterojunction solar cell comprises a first electrode (2) and a second electrode (5), an electrically active layer (4) disposed between the first and second electrodes and comprising an organic p-type semiconductor material and a n-type carbon semiconductor material, and an additional layer (7) disposed between the first electrode and the electrically active layer in direct contact with the active layer. The additional layer comprises a compound forming non-covalent interactions with the n-type carbon semiconductor material. The concentration of n-type carbon semiconductor material decreases in the electrically active layer from a first surface of the electrically active layer in contact with the additional layer to a second surface of the electrically active layer opposite to the first surface. The concentration of p-type organic semiconductor material increases in the electrically active layer from a first surface of the electrically active layer in contact with the additional layer to a second surface of the electrically active layer. The compound forming non-covalent interactions with the n-type carbon semiconductor material comprises fluorinated polymers, and polymers with side chains containing nitrogenous aromatic group. A thin intermediate layer (6) of a n-type semiconductor material is disposed between the first electrode and the additional layer.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a heterojunction organic solar cell.    First electrode (2)    Injection layer (3)    Electrically active layer (4)    Second electrode (5)    Thin intermediate layer (6)    Additional layer. (7)