Disclosed is an organic light-emitting diodes including a ZnO nanoparticle and an ionic group. The organic light-emitting diodes according to the present invention includes: a substrate formed of glass or a flexible plastic material; an anode formed on the substrate; a hole transport layer formed on the anode; an emissive layer formed on the hole transport layer; an electron transport layer being formed on the emissive layer and including a ZnO nanoparticle; an electron injection layer being formed on the electron transport layer and including an ionic group; and a cathode formed on the electron injection layer.