NOVELTY - The method involves mixing and setting an electron donor material and an electron acceptor material on a transparent conductive substrate for forming an active layer (S1). Solvent is heated (S2) into a hot solvent vapor, which allows the active layer to be annealed in the vapor, where the vapor moistens and modifies a surface morphology of the active layer. The active layer is thermal-annealed. The active layer is moved out (S3) of an environment, where the vapor is settled and embellished active layer is desiccated. An electrode layer is set (S4) on the active layer.    USE - Method for manufacturing large-area organic solar cells for industrial application.    ADVANTAGE - The method enables manufacturing large-area organic solar cells, which obtain a better power conversion efficiency of the solar cells in short time, thus reducing manufacturing time and saving manufacturing cost to complete the process in minutes without consuming the processing time of the solvent vapor annealing and attain better power conversion efficiency. The method enables manufacturing the active layer with a large area and without being restricted by the area of the element. The method enables adopting hot solvent vapor annealing process to modify a morphology and a nanostructure of a layer including coarser surfaces and thicker thickness for enhancing flatness and uniformity and increasing quality of the nanostructure, crystallinity and a contact surface of a cathode metal layer.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow diagram illustrating a method for manufacturing large-area organic solar cells.    Step for mixing and setting electron donor material and electron acceptor material on transparent conductive substrate for forming active layer (S1)    Step for heating solvent into hot solvent vapor, which allows active layer to be annealed in hot solvent vapor (S2)    Step for moving active layer out of environment (S3)    Step for setting electrode layer on active layer (S4)