An organic light emitting device comprising: a substrate; a first electrode; an organic light emitting layer disposed on the first electrode having a curvy shape including a plurality of convex regions and a plurality of concave regions, wherein the organic light emitting layer in at least one of the convex regions or at least one of the concave regions is thinner at a point between and away from a bottom and a top of said one of the convex regions or concave regions than at the bottom or the top of said one of the convex regions or concave regions; a second electrode disposed on the organic light emitting layer; and an overcoat layer disposed on the substrate and under the first electrode, and including a plurality of convex parts and a plurality of concave parts corresponding to the convex regions and the concave regions, respectively, of the organic light emitting layer, wherein the convex parts of the overcoat layer have a Full Width at Half Maximum, FWHM, smaller than a radius (D/2) thereof wherein the FWHM is defined as a length between both sides of the convex portion at a position of a half-height; and the radius is defined as half the diameter, said diameter being defined as a length between centres of two first connection portions, in which a connection portion is defined as a portion positioned between adjacent convex parts; characterised in that characterised in that an FWHM aspect ratio of the convex parts of the overcoat layer, defined by the height of the convex portion divided by the Full Width at Half Maximum of the convex portion, is larger than an aspect ratio of the convex parts of the overcoat layer, defined by the height of the convex portion divided by the radius (D/2) of the convex portion, and in that the aspect ratio of the convex parts is in the range of 0.4 to 0.7. a substrate; a first electrode; an organic light emitting layer disposed on the first electrode having a curvy shape including a plurality of convex regions and a plurality of concave regions, wherein the organic light emitting layer in at least one of the convex regions or at least one of the concave regions is thinner at a point between and away from a bottom and a top of said one of the convex regions or concave regions than at the bottom or the top of said one of the convex regions or concave regions; a second electrode disposed on the organic light emitting layer; and an overcoat layer disposed on the substrate and under the first electrode, and including a plurality of convex parts and a plurality of concave parts corresponding to the convex regions and the concave regions, respectively, of the organic light emitting layer, wherein the convex parts of the overcoat layer have a Full Width at Half Maximum, FWHM, smaller than a radius (D/2) thereof wherein the FWHM is defined as a length between both sides of the convex portion at a position of a half-height; and the radius is defined as half the diameter, said diameter being defined as a length between centres of two first connection portions, in which a connection portion is defined as a portion positioned between adjacent convex parts; characterised in that characterised in that an FWHM aspect ratio of the convex parts of the overcoat layer, defined by the height of the convex portion divided by the Full Width at Half Maximum of the convex portion, is larger than an aspect ratio of the convex parts of the overcoat layer, defined by the height of the convex portion divided by the radius (D/2) of the convex portion, and in that the aspect ratio of the convex parts is in the range of 0.4 to 0.7.