Electroluminescent device, and display device comprising the same

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 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 and comprising at least two different organic semiconductor compounds,

wherein a first root-mean surface roughness of a surface of the electron transport layer is in a range from about 0.5 nanometers to about 3 nanometers, and

the at least two different organic semiconductor compounds comprise a conductive monomolecular organic nanocompound having a conjugated structure, a conductive low molecular organic nanocompound having a conjugated structure, or a combination thereof.

2. The electroluminescent device of claim 1 , wherein a charge mobility of the electron transport layer is in a range from about 10 −2 centimeters per volt-second to about 10 −7 centimeters per volt-second.

3. The electroluminescent device of claim 1 , wherein a lowest unoccupied molecular orbital energy level of the electron transport layer is in a range from about −2.5 electronvolts to about −3.5 electronvolts.

4. The electroluminescent device of claim 1 , wherein the first root-mean surface roughness of the surface of the electron transport layer is in a range from about 0.8 nanometers to about 2 nanometers.

5. The electroluminescent device of claim 1 , wherein the at least two different organic semiconductor compounds comprise a quinolone compound, a triazine compound, a quinoline compound, a triazole compound, a naphthalene compound, or a combination thereof.

6. The electroluminescent device of claim 1 , wherein the electron transport layer has an average thickness in a range of about 20 nanometers to about 50 nanometers.

7. The electroluminescent device of claim 1 , wherein the electron transport layer is directly on the emission layer to cover the surface of the emission layer.

8. The electroluminescent device of claim 1 , wherein the light emitting particle emits light in a blue wavelength region.

9. A display device comprising the electroluminescent device of claim 1 .

10. The electroluminescent device of claim 1 , wherein a second root-mean surface roughness of the surface of the electron transport layer measured by an atomic-force microscopy is in a range from about 0.5 nanometers to about 10 nanometers.

11. The electroluminescent device of claim 10 , wherein the second root-mean surface roughness is in a range from about 0.5 nanometers to about 5 nanometers.

12. The electroluminescent device of claim 1 , wherein

the at least two different organic semiconductor compounds comprise a first organic semiconductor compound and a second organic semiconductor compound,

wherein first organic semiconductor compound comprises a compound represented by Chemical Formula 1, Chemical Formula 2, or a triaryl triazine compound, and

wherein the second organic semiconductor compound comprises a compound represented by Chemical Formula 3, a pyrazole compound, or a phosphonyl phenol compound:

13. The electroluminescent device of claim 12 , wherein a weight ratio of the first organic semiconductor compound to the second organic semiconductor in the electron transport layer is in a range of about 8:2 to about 2:8.

14. The electroluminescent device of claim 12 , wherein a weight ratio of the first organic semiconductor compound to the second organic semiconductor compound in the electron transport layer is in a range of about 8:2 to about 5:5.

15. The electroluminescent device of claim 1 , wherein the light emitting particle comprises a quantum dot.

16. The electroluminescent device of claim 15 , wherein the quantum dot comprises 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 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 dot has a core-shell structure.