Method for fabricating a substrate comprising a nanostructured surface for an organic light emitting diode OLED, in which the following successive steps are carried out: a) a layer of an organic resin or of a low melting point mineral material is deposited on a planar surface of a substrate; b) the organic resin is heated to a temperature equal to or higher than its glass transition temperature Tg or its melting point, or the mineral material is heated to a temperature equal to or higher than its melting point, and the layer of liquid organic resin or mineral material is printed with a mould having a nanostructuration, whereby the layer of organic resin or mineral material is provided with a first nanostructuration matching the nanostructuration of the mould; c) the temperature of the organic resin or of the mineral material is lowered to a temperature at which it is solid; d) the mould is separated from the layer of organic resin or of mineral material joined to the substrate; characterized in that the method further comprises, at the end of step d) the following successive steps: e) the organic resin is heated to a temperature equal to or higher than its glass transition temperature Tg or its melting point, or the mineral material is heated to a temperature equal to or higher than its melting point, and the organic resin or the mineral material is maintained at this temperature for a time t R called annealing time, whereby the organic resin or the mineral material flows and the first nanostructuration of the layer of organic resin or of mineral material is modified to produce a second nanostructuration (410, 411); f) the organic resin or the mineral material is cooled below its glass transition temperature or its melting point to solidify it; g) optionally, the solid organic resin or the solid mineral material is annealed. a) a layer of an organic resin or of a low melting point mineral material is deposited on a planar surface of a substrate; b) the organic resin is heated to a temperature equal to or higher than its glass transition temperature Tg or its melting point, or the mineral material is heated to a temperature equal to or higher than its melting point, and the layer of liquid organic resin or mineral material is printed with a mould having a nanostructuration, whereby the layer of organic resin or mineral material is provided with a first nanostructuration matching the nanostructuration of the mould; c) the temperature of the organic resin or of the mineral material is lowered to a temperature at which it is solid; d) the mould is separated from the layer of organic resin or of mineral material joined to the substrate; e) the organic resin is heated to a temperature equal to or higher than its glass transition temperature Tg or its melting point, or the mineral material is heated to a temperature equal to or higher than its melting point, and the organic resin or the mineral material is maintained at this temperature for a time t R called annealing time, whereby the organic resin or the mineral material flows and the first nanostructuration of the layer of organic resin or of mineral material is modified to produce a second nanostructuration (410, 411); f) the organic resin or the mineral material is cooled below its glass transition temperature or its melting point to solidify it; g) optionally, the solid organic resin or the solid mineral material is annealed.