An electroluminescent device , comprising: a first electrode and a second electrode facing each other; an emission layer disposed between the first electrode and the second electrode and comprising a plurality of light emitting particles ; a hole transport layer disposed between the first electrode and the emission layer; and an electron transport layer disposed between the emission layer and the second electrode; wherein the electron transport layer comprises: an inorganic layer disposed on the emission layer, the inorganic layer comprising a plurality of inorganic nanoparticles ; and an organic layer directly disposed on at least a portion of an upper surface of the inorganic layer on a side opposite the emission layer, wherein an inorganic nanoparticle of the plurality of inorganic nanoparticles is ZnO, TiO 2 , ZrO 2 , SnO 2 , WO 3 , Ta 2 O 3 , or a combination thereof, wherein the organic layer comprises an organic semiconductor compound that is a quinolone-based compound, a triazine-based compound, a quinoline-based compound, a triazole-based compound, a naphthalene-based compound, or a combination thereof, or a phosphine oxide based compound, a phosphonyl phenol based compound, or a combination thereof, wherein the organic layer is an energy barrier against electrons moving from the second electrode to the inorganic layer, and wherein an average thickness of the organic layer is 2 nanometers to 20 nanometers. a first electrode and a second electrode facing each other; an emission layer disposed between the first electrode and the second electrode and comprising a plurality of light emitting particles ; a hole transport layer disposed between the first electrode and the emission layer; and an electron transport layer disposed between the emission layer and the second electrode; wherein the electron transport layer comprises: an inorganic layer disposed on the emission layer, the inorganic layer comprising a plurality of inorganic nanoparticles ; and an organic layer directly disposed on at least a portion of an upper surface of the inorganic layer on a side opposite the emission layer, wherein an inorganic nanoparticle of the plurality of inorganic nanoparticles is ZnO, TiO 2 , ZrO 2 , SnO 2 , WO 3 , Ta 2 O 3 , or a combination thereof, wherein the organic layer comprises an organic semiconductor compound that is a quinolone-based compound, a triazine-based compound, a quinoline-based compound, a triazole-based compound, a naphthalene-based compound, or a combination thereof, or a phosphine oxide based compound, a phosphonyl phenol based compound, or a combination thereof, wherein the organic layer is an energy barrier against electrons moving from the second electrode to the inorganic layer, and wherein an average thickness of the organic layer is 2 nanometers to 20 nanometers. an inorganic layer disposed on the emission layer, the inorganic layer comprising a plurality of inorganic nanoparticles ; and an organic layer directly disposed on at least a portion of an upper surface of the inorganic layer on a side opposite the emission layer, wherein an inorganic nanoparticle of the plurality of inorganic nanoparticles is ZnO, TiO 2 , ZrO 2 , SnO 2 , WO 3 , Ta 2 O 3 , or a combination thereof, wherein the organic layer comprises an organic semiconductor compound that is a quinolone-based compound, a triazine-based compound, a quinoline-based compound, a triazole-based compound, a naphthalene-based compound, or a combination thereof, or a phosphine oxide based compound, a phosphonyl phenol based compound, or a combination thereof, wherein the organic layer is an energy barrier against electrons moving from the second electrode to the inorganic layer, and wherein an average thickness of the organic layer is 2 nanometers to 20 nanometers. <EOS>