NOVELTY - The method comprises forming recesses with an electromagnetic radiation emitted by a laser light source at a surface of a substrate (1) from a polymeric material, and coating the recesses from a polymeric material formed on the surface of the substrate and/or a layer from an electrical conductive material. The recesses form a regular array of structural elements at the respective surface of the substrate, before further layers are formed for forming organic light emitting diodes or organic photovoltaic elements on the surface of the substrate.    USE - The method is useful for preparing LEDs such as organic LEDs or photovoltaic elements such as organic solar cells.    ADVANTAGE - The method is capable of effectively and economically preparing the LEDs or photovoltaic elements with high quality and less effort.    DETAILED DESCRIPTION - The method comprises forming recesses with an electromagnetic radiation emitted by a laser light source at a surface of a substrate (1) from a polymeric material, and coating the recesses from a polymeric material formed on the surface of the substrate and/or a layer from an electrical conductive material. The recesses form a regular array of structural elements at the respective surface of the substrate, before further layers are formed for forming organic light emitting diodes or organic photovoltaic elements on the surface of the substrate or a multilayer structure is connected for the organic light emitting diodes or organic photovoltaic elements with the substrate. The radiation emitted by the laser light source: is directed with local varying intensity, focus, power, polarization, pulse rate/pulse length and/or with different wavelengths on the surface of the substrate so that a local varying material removal and/or recast takes place for forming the recesses; is radiated by a microlens array; and is divided into partial laser beams, where the emitted radiation is focused on a plane that coincides with the plane of the surface of the substrate and is arranged in radiation direction before or after the plane of the surface of the substrate. An irradiation of the emitted radiation takes place from the laser light source in such a way that the laser partial beams in an overlay area are brought under predefined/angle to interference. The substrate is positioned with the respective surface at a predefined position in the overlay area. The laser partial beams are generated by a beam splitter from an individual laser beam emitted from the laser light source, and are guided using a beam deflector into the overlay area. The recesses are periodically formed in the form of a recess structure: in the surface of the substrate; in the plane of the surface of the substrate viewed in direction; and/or in two directions standing to each other under an angle of 60 degrees . The recesses are formed so that a distance between neighboring recesses and/or a periodicity of the recess structure in the plane of the surface of the substrate is 100 nm and 300 mu m. A depth expansion of the recesses to the plane is 10 nm and 50 mu m. A lateral expansion of the recesses in the plane of the substrate is 25 nm and 250 mu m. An aspect ratio of the depth expansion and the lateral expansion is 0.3-3. The recesses are formed so that the periodical recess structure comprises: linear-shaped trench structures comprising trenches running from each other with constant trench spacing or crossing trench structures with same or different trench spacings comprising the structure at an angle of 60 degrees ; and blind holes comprising periodical hole structure. The blind holes of the hole structure are formed in two directions standing to each other under the angle of 45-90 degrees including borders of 45-90 degrees respectively in periodical spacings. A surface structure formed on the surface of the substrate is transferred with the formed recesses into a reflective layer formed on the surface of the substrate. The layer is formed from an electrical conductive polymer, an electrical conductive oxide or a metal. The irradiation is pulsed or continuous and is performed with the electromagnetic radiation of the wavelength in an infrared region and/or in an ultraviolet region having the radiation of neodymium-doped yttrium aluminum garnet (Nd:YAG) pulsed laser light source of the wavelength of 266-355 nm. The recesses are formed on the surface of the substrate in such a way that the depth expansion and/or the lateral expansion of the recesses is of different sizes. The surface between the recesses in an edge region of the recesses has a radius of 10 nm.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of organic LEDs or organic photovoltaic elements.    Substrate (1)    Radiation reflecting layer (1.2)    Electrode forming layers (1.3, 1.5)    Active organic layer (1.4)    Outer layer. (1.6)