Quantum dot light-emitting diode and quantum dot light-emitting device having the same

1. A quantum dot comprising:

a semiconductor nanocrystal or metal oxide core;

a shell substantially or fully covering the core, wherein the shell has an outer surface;

an X-type ligand comprising a functional group selected from the group consisting of a carboxylate group, a phosphate group, and a thiolate group bound to a first region of the outer surface; and

an L-type ligand comprising a functional group selected from the group consisting of an amino group, a thiol group, a phosphine group, and a phosphine oxide group bound to a second region of the outer surface.

2. The quantum dot of claim 1 , wherein the X-type ligand further comprises a C 5 -C 30 saturated or unsaturated hydrocarbon chain.

3. The quantum dot of claim 1 , wherein the X-type ligand has one of the following structures:

wherein:

n is an integer ranging from 6 to 16;

m is an integer ranging from 4 to 9;

p is an integer ranging from 4 to 9; and

X is a carboxylate group, a phosphate group, or a thiolate group.

4. The quantum dot of claim 3 , wherein the X-type ligand is selected from the group consisting of octanoic acid, decanoic acid, dodecanoic acid, myristic acid, palmitic acid, hexadecanoic acid, stearic acid, oleic acid, and combinations thereof.

5. The quantum dot of claim 1 , wherein the L-type ligand is selected from the group consisting of C 1 to C 10 linear or branched alkyl amines, C 4 to C 8 alicyclic amines, C 5 to C 20 aromatic amines, C 1 to C 10 linear or branched alkyl phosphines, C 1 to C 10 linear or branched alkyl phosphine oxides and a combination thereof.

6. The quantum dot of claim 1 , wherein the L-type ligand is tris(2-aminoethyl)amine, tris(2-aminomethyl)amine, N-butyl-N-ethylethane-1,2-diamine, ethylene diamine, pentaethylenehexamine, cyclohexane-1,2-diamine, cyclohexene-1,2-diamine, or 2,3-diaminopyridine.

7. The quantum dot of claim 1 , wherein the X-type ligand is bound to the first region of the outer surface through a negatively charged functional group.

8. The quantum dot of claim 1 , wherein the L-type ligand is bound to the second region of the outer surface through an unshared electron pair.

9. The quantum dot of claim 1 , wherein the outer surface is substantially spherical and the first region is a first hemisphere and the second region is a second hemisphere.

10. A light emitting diode comprising a plurality of quantum dots according to claim 1 .

11. The light emitting diode of claim 10 comprising:

a first electrode and a second electrode;

an emitting material layer;

an electron transfer layer; and

a hole transfer layer

wherein

the emitting material layer is interposed between the electron transfer layer and the hole transfer layer and the emitting material layer comprises the quantum dots.

12. The light emitting diode of claim 11 , wherein a plurality of the first regions of the outer surfaces of the quantum dots are substantially proximal to the hole transfer layer and substantially distal to the electron transfer layer.

13. The light emitting diode of claim 11 , wherein a plurality of the second regions of the outer surfaces of the quantum dots are substantially proximal to the electron transfer layer and distal to the hole transfer layer.

14. A light emitting device comprising a quantum dot of claim 1 .

15. The light emitting device of claim 14 comprising:

a substrate;

a light emitting diode comprising the quantum dot of claim 1 on the substrate; and

a driving element disposed between the substrate and the light emitting diode and connected to the light emitting diode.

16. A light emitting device comprising a light-emitting diode of claim 10 .

17. The light emitting device of claim 16 comprising:

a substrate;

a light emitting diode comprising the quantum dot of claim 1 on the substrate; and

a driving element disposed between the substrate and the light emitting diode and connected to the light emitting diode.