Electroluminescent device, and display device comprising the same
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 including at least two 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 the inorganic layer on a side opposite the emission layer, wherein a work function of the organic layer is greater than a work function of the inorganic layer.
1. 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 the organic layer has an average thickness of about 2 nanometers to about 20 nanometers.
2. The electroluminescent device of claim 1 , wherein the organic layer completely covers the upper surface of the inorganic layer between the inorganic layer and the second electrode.
3. The electroluminescent device of claim 1 , wherein the organic layer has a lowest unoccupied molecular orbital (LUMO) energy level of about −1.8 electron Volts to about −2.8 electron Volts.
4. The electroluminescent device of claim 1 , wherein the organic layer has an electron mobility of about 10 −3 square centimeters per Volt-second to about 10 −1 square centimeters per Volt-second.
5. The electroluminescent device of claim 1 , 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.
6. The electroluminescent device of claim 1 , wherein an average particle diameter of the plurality of inorganic nanoparticles is less than or equal to about 150 nanometers.
7. The electroluminescent device of claim 1 , wherein the inorganic layer is disposed on the emission layer as a cluster layer comprising the plurality of inorganic nanoparticles.
8. The electroluminescent device of claim 7 , wherein the cluster layer is disposed directly on the emission layer.
9. The electroluminescent device of claim 7 , wherein
an upper surface of the cluster layer comprises a surface region having two or more grains each comprising the inorganic nanoparticles, wherein a grain boundary is formed between adjacent grains, and
the organic layer fills at least a portion of the grain boundary.
10. The electroluminescent device of claim 7 , wherein an average thickness of the cluster layer is less than or equal to about 100 nanometers.
11. The electroluminescent device of claim 1 , 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.
12. The electroluminescent device of claim 11 , wherein the organic layer comprises at least two different organic semiconductor compounds.
13. The electroluminescent device of claim 12 , wherein
the organic layer comprises a first organic semiconductor compound and a second organic semiconductor compound that are different from each other, and
a weight ratio of the first organic semiconductor compound and the second organic semiconductor compound in the organic layer is about 3:7 to about 7:3.
14. The electroluminescent device of claim 1 , wherein the electron transport layer further comprises at least one additional unit comprising an inorganic layer and an organic layer, wherein the inorganic layers and the organic layers in the electron transport layer are alternately stacked.
15. The electroluminescent device of claim 1 , wherein the plurality of light emitting particles comprises quantum dots.
16. The electroluminescent device of claim 15 , wherein the quantum dots are a Group II-VI compound that does not comprise Cd, a Group III-V compound, a Group IV-VI compound, a Group IV element or compound, a Group I-III-VI compound, a Group I-II-IV-VI compound that does not comprise Cd, or a combination thereof.
17. The electroluminescent device of claim 15 , wherein the quantum dots have a core-shell structure.
18. The electroluminescent device of claim 1 , wherein the electron transport layer does not have electroluminescence.
19. The electroluminescent device of claim 1 , which further comprises an electron injection layer between the second electrode and the electron transport layer, and optionally a carrier blocking layer between the second electrode and the electron injection layer or between the electron injection layer and the electron transport layer.
20. A display device comprising the electroluminescent device of claim 1 .