Quantum dots, production methods thereof, and light emitting device including the same

1. A quantum dot, comprising

a semiconductor nanocrystal, and

an organic ligand bound to a surface of the semiconductor nanocrystal,

wherein the organic ligand comprises

a first ligand derived from a first thiol compound comprising a C12 or more aliphatic hydrocarbon group, and

a second ligand derived from a second thiol compound comprising a C8 or less aliphatic hydrocarbon group.

2. The quantum dot of claim 1 , wherein the quantum dot comprises

a core comprising a first semiconductor nanocrystal, and

a shell disposed on the core, the shell comprising a second semiconductor nanocrystal comprising a different composition from a composition of the first semiconductor nanocrystal.

3. The quantum dot of claim 2 , wherein the first semiconductor nanocrystal and the second semiconductor nanocrystal are independently a Group II-VI compound, 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, or a combination thereof.

4. The quantum dot of claim 1 , wherein the first thiol compound comprises a compound represented by Chemical Formula 1:

wherein, R 1 is hydrogen; a substituted or unsubstituted C1 to C30 linear or branched alkyl group; a substituted or unsubstituted C2 to C30 linear or branched alkenyl group; a substituted or unsubstituted C2 to C30 linear or branched alkynyl group; a substituted or unsubstituted C6 to C30 aryl group; a substituted or unsubstituted C7 to C30 arylalkyl group; a substituted or unsubstituted C3 to C30 cycloalkyl group; a C1 to C30 alkoxy group; a hydroxy group; —NH 2 ; a substituted or unsubstituted C1 to C30 amine group (—NRR′, wherein R and R′ are independently hydrogen or a C1 to C30 linear or branched alkyl group, provided that R and R′ are not simultaneously hydrogen); an isocyanate group; a halogen; —ROR′, wherein R is a substituted or unsubstituted C1 to C20 alkylene group, and R′ is hydrogen or a C1 to C20 linear or branched alkyl group; an acyl halide (—RC(═O)X, wherein R is a substituted or unsubstituted C1 to C30 alkylene group and X is a halogen); —C(═O)OR′, wherein R′ is hydrogen or a C1 to C30 linear or branched alkyl group; —CN; —C(═O)ONRR′, wherein R and R′ are independently hydrogen or a C1 to C20 linear or branched alkyl group; or a combination thereof,

L 1 is a carbon atom, a nitrogen atom, a substituted or unsubstituted C1 to C30 alkylene group, a substituted or unsubstituted C2 to C30 alkenylene group, a substituted or unsubstituted C3 to C30 cycloalkylene group, a substituted or unsubstituted C6 to C30 arylene group, or a substituted or unsubstituted C1 to C30 alkylene group or a substituted or unsubstituted C2 to C30 alkenylene group wherein a methylene moiety is replaced by a sulfonyl moiety, a carbonyl moiety, an ether moiety, a sulfide moiety, a sulfoxide moiety, an ester moiety, an amide moiety comprising hydrogen or a C1 to C10 alkyl group, or a combination thereof,

Y 1 is a single bond; —C(═S)—; a substituted or unsubstituted C1 to C30 alkylene group; a substituted or unsubstituted C2 to C30 alkenylene group; or a C1 to C30 alkylene group or a C2 to C30 alkenylene group wherein a methylene moiety is replaced by a sulfonyl moiety, a carbonyl moiety, an ether moiety, a sulfide moiety, a sulfoxide moiety, an ester moiety, an amide moiety comprising hydrogen or a C1 to C10 linear or branched alkyl group, an imine moiety comprising hydrogen or a C1 to C10 linear or branched alkyl group, or a combination thereof;

M is hydrogen or a monovalent metal,

k1 is 0 or an integer of 1 or greater,

k2 is 1 or 2, provided that when k2 is 2, Y 1 is a single bond, and each SM moiety is bonded to an adjacent carbon atom in the L 1 moiety,

a sum of k1 and k2 does not exceed the valence of L 1 , and

R 1 , L 1 , and Y 1 are selected such that the first thiol compound comprises a C12 or more aliphatic hydrocarbon group.

5. The quantum dot of claim 1 , wherein the first thiol compound comprises a C12 to C40 substituted or unsubstituted alkyl group, a C12 to C40 substituted or unsubstituted alkenyl group, a poly(ethyleneglycol)alkylether thiol, or a combination thereof.

6. The quantum dot of claim 1 , wherein the first thiol compound comprises dodecane thiol, tetradecane thiol, hexadecane thiol, octadecane thiol, oleyl mercaptan, or a combination thereof.

7. The quantum dot of claim 1 , wherein the second thiol compound comprises a compound represented by Chemical Formula 2:

wherein, R 2 is hydrogen; a substituted or unsubstituted C1 to C8 linear or branched alkyl group; a substituted or unsubstituted C2 to C8 linear or branched alkenyl group; a substituted or unsubstituted C6 aryl group; a substituted or unsubstituted C3 to C8 cycloalkyl group; a C1 to C8 alkoxy group; a hydroxy group; —NH 2 ; a substituted or unsubstituted C1 to C8 amine group (—NRR′, wherein R and R′ are independently hydrogen or a C1 to C4 linear or branched alkyl group provided that R and R′ are not simultaneously hydrogen); an isocyanate group; a halogen; —ROR′, wherein R is a substituted or unsubstituted C1 to C7 alkylene group, and R′ is hydrogen or a C1 to C7 linear or branched alkyl group; an acyl halide (—RC(═O)X, wherein R is a substituted or unsubstituted C1 to C7 alkylene group and X is a halogen); —C(═O)OR′, wherein R′ is hydrogen or a C1 to C7 linear or branched alkyl group; —CN; —C(═O)ONRR′, wherein R and R′ are independently hydrogen or a C1 to C7 linear or branched alkyl group; or a combination thereof,

L 2 is a carbon atom, a nitrogen atom, a substituted or unsubstituted C1 to C8 alkylene group, a substituted or unsubstituted C3 to C8 cycloalkylene group, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted C1 to C8 alkylene group wherein a methylene moiety is replaced by a sulfonyl moiety, a carbonyl moiety, an ether moiety, a sulfide moiety, a sulfoxide moiety, an ester moiety, an amide moiety comprising hydrogen or a C1 to C10 alkyl group,

Y 2 is a single bond; —C(═S)—; a substituted or unsubstituted C1 to C7 alkylene group; a substituted or unsubstituted C2 to C7 alkenylene group; or a C1 to C7 alkylene group or a C2 to C7 alkenylene group wherein a methylene moiety is replaced by a sulfonyl moiety, a carbonyl moiety, an ether moiety, a sulfide moiety, a sulfoxide moiety, an ester moiety, an amide moiety comprising hydrogen or a C1 to C7 linear or branched alkyl group, an imine moiety comprising hydrogen or a C1 to C7 linear or branched alkyl group, or a combination thereof;

M is hydrogen or a monovalent metal,

k3 is 0 or an integer of 1 or greater,

k4 is 1 or 2, provided that when k4 is 2, Y 2 is a single bond and each SM moiety is bonded to an adjacent carbon atom in the L 1 moiety,

a sum of k3 and k4 does not exceed the valence of L 2 , and

R 2 , L 2 , and Y 2 are independently selected such that the second thiol compound comprises a C8 or less aliphatic hydrocarbon group.

8. The quantum dot of claim 1 , wherein the second thiol compound comprises a C3 to C8 substituted or unsubstituted alkyl group, a C3 to C8 substituted or unsubstituted alkenyl group, or a combination thereof.

9. The quantum dot of claim 1 , wherein the second thiol compound comprises a butane thiol, a pentane thiol, a hexane thiol, a heptane thiol, an octane thiol, 2-(2-methoxyethoxy)ethane thiol, 3-methoxybutyl 3-mercaptopropinonate, 3-methoxybutylmercaptoacetate, thioglycolic acid, 3-mercaptopropionic acid, thiopronine, 2-mercaptopropionic acid, 2-mercaptopropinonate, 2-mercaptoethanol, 1-thioglycerol, mercaptosuccinic acid, L-cysteine, 2-(dimethylamino)ethanethiol, 5-mercaptomethyltetrazole, 2,3-dimercapto-1-propanol, glutathione, diethyldithiocarbamate, or a combination thereof.

10. The quantum dot of claim 1 , wherein the first thiol compound does not comprise a carboxylic acid moiety and the second thiol compound does not comprise a carboxylic acid moiety.

11. The quantum dot of claim 1 , wherein

the quantum dot further comprises a third ligand derived from RC(═O)OH, RC(═O)OM′, RNH 2 , R 2 NH, R 3 N, R 3 PO, R 3 P, ROH, RP(═O)(OH) 2 , R 2 P(═O)OH, wherein, each R is independently a substituted or unsubstituted C5 to C24 alkyl group, a substituted or unsubstituted C5 to C24 alkenyl group, or a substituted or unsubstituted C5 to C20 aryl group, and M′ is a monovalent metal, or a combination thereof, and

the third ligand is present in an amount of less than about 5 weight percent, based on a total weight of the quantum dot.

12. The quantum dot of claim 11 , wherein in the quantum dot, the amount of the third ligand is less than or equal to about 1 weight percent, based on a total weight of the quantum dot.

13. The quantum dot of claim 1 , wherein a total amount of an organic substance present in the quantum dot is less than about 15 weight percent, as measured by a thermogravimetric analysis.

14. The quantum dot of claim 1 , wherein the quantum dot further comprises a polyvalent metal compound or a moiety derived therefrom on a surface of the quantum dot.

15. The quantum dot of claim 14 , wherein the polyvalent metal compound comprises zinc, indium, or a combination thereof.

16. The quantum dot of claim 14 , wherein the polyvalent metal compound comprises a (meth)acrylate moiety, RCOO—, wherein R is a C10 or less aliphatic hydrocarbon group, a halide, or a combination thereof.

17. The quantum dot of claim 14 , wherein the polyvalent metal compound comprises zinc chloride, zinc bromide, zinc iodide, indium chloride, zinc(meth)acrylate, zinc propinonate, or a combination thereof.

18. A light emitting device comprising

a first electrode and a second electrode facing each other; and

an emission layer disposed between the first electrode and the second electrode, the emission layer comprising the quantum dot according to claim 1 .

19. The light emitting device of claim 18 , wherein the light emitting device further comprises a hole injecting layer, a hole transport layer, an electron blocking layer, or a combination thereof between the first electrode and the emission layer.

20. The light emitting device of claim 18 , wherein the light emitting device further comprises an electron injecting layer, an electron transport layer, a hole blocking layer, or a combination thereof between the second electrode and the emission layer.

21. A display device comprising the light emitting device of claim 18 .