Light-emitting element comprising quantum dots, display device including the same, and manufacturing method of the light-emitting element
A method of manufacturing a light-emitting element includes forming a first electrode, forming a hole transport region by providing a hole transport material on the first electrode, forming a light-emitting layer on the hole transport region, forming an electron transport region on the light-emitting layer, and forming a second electrode on the electron transport region, wherein the forming of the light-emitting layer includes providing, on the hole transport region, a quantum dot composition including an organic solvent and a plurality of quantum dots, heat-treating the quantum dot composition, and vacuum-drying the heat-treated quantum dot composition, so that a light-emitting element in which quantum dots have infiltrated into the hole transport region may be manufactured.
1 . A light-emitting element comprising:
a first electrode;
a light-emitting layer on the first electrode and comprising quantum dots;
a hole transport region between the first electrode and the light-emitting layer and comprising a first portion adjacent to the light-emitting layer, the first portion consisting of a hole transport material and quantum dots the same as those comprised in the light-emitting layer, and the first portion having a concentration gradient which is a distribution density of the quantum dots decreasing from a portion of the first portion adjacent to the light-emitting layer to a portion of the first portion further away from the light-emitting layer;
an electron transport region on the light-emitting layer; and
a second electrode on the electron transport region,
wherein an interface is defined between the light-emitting layer and the hole transport region, and
the hole transport material is selected from the group consisting of a compound represented by Formula H-1, a phthalocyanine compound, N,N′-diphenyl-N, N′-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4′-diamine (DNTPD), 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (TDATA), 4,4′,4″-tris {N-(2-naphthyl)-N-phenylamino}-triphenylamine (2-TNATA), polyaniline/dodecylbenzenesulfonic acid (PANI/DBSA), polyaniline/camphor sulfonic acid (PANI/CSA), (polyaniline)/poly(4-styrenesulfonate) (PANI/PSS), N,N′-di(naphthalene-1-yl)-N, N′-diphenyl-benzidine (NPB), 4-isopropyl-4′-methyldiphenyliodonium tetrakis(pentafluorophenyl) borate, a fluorine-based derivative, 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), 4,4′-bis[N,N′-(3-tolyl)amino]-3,3′-dimethylbiphenyl (HMTPD), 1,3-Bis(N-carbazolyl)benzene (mCP), 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi), 9-phenyl-9H-3,9′-bicarbazole (CCP), and 1,3-bis(1,8-dimethyl-9H-carbazol-9-yl)benzene (mDCP),
wherein in Formula H-1,
L 1 and L 2 are each independently a substituted or unsubstituted arylene group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 30 ring-forming carbon atoms,
a and b are each independently an integer of 0 to 10,
Ar 1 and Ar 2 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 30 ring-forming carbon atoms, and
Ar 3 is a substituted or unsubstituted aryl group having 6 to 30 ring-forming carbon atoms,
wherein a substituent of the substituted arylene group, the substituted heteroarylene group, the substituted aryl group, and the substituted heteroaryl group is selected from the group consisting of a deuterium atom, a halogen atom, a cyano group, a nitro group, an amino group, a silyl group, an oxy group, a sulfinyl group, a sulfonyl group, a carbonyl group, a boron group, a phosphine oxide group, a phosphine sulfide group, an alkyl group, an alkoxy group, a hydrocarbon ring group, an aryl group, and a heterocyclic group.
2 . The light-emitting element of claim 1 , wherein the hole transport region comprises the first portion and a second portion not comprising the quantum dots.
3 . The light-emitting element of claim 1 , wherein
the hole transport region comprises a plurality of organic layers, and
an organic layer most adjacent to the light-emitting layer from among the plurality of organic layers comprises the quantum dots.
4 . The light-emitting element of claim 1 , wherein
the hole transport region comprises a hole injection layer and a hole transport layer on the hole injection layer, and
the hole transport layer comprises the quantum dots, and the hole injection layer does not comprise the quantum dots.
5 . The light-emitting element of claim 4 , wherein
the hole transport layer comprises the first portion and a fourth portion not comprising the quantum dots.
6 . The light-emitting element of claim 5 , wherein a thickness of the first portion is smaller than a thickness of the fourth portion.
7 . The light-emitting element of claim 5 , wherein,
in the first portion, the distribution density of the quantum dots in the portion adjacent to the light-emitting layer is greater than a distribution density of the quantum dots in a portion adjacent to the fourth portion.
8 . The light-emitting element of claim 5 , wherein a distribution density of the quantum dots decreases from the first portion to the fourth portion.
9 . A display device comprising first to third light-emitting elements configured to emit light having different wavelengths,
wherein each of the first to third light-emitting elements comprises:
a first electrode;
a light-emitting layer on the first electrode and comprising quantum dots;
a hole transport region between the first electrode and the light-emitting layer and consisting of:
a hole transport material, and
quantum dots the same as those comprised in the light-emitting layer;
an electron transport region on the light-emitting layer; and
a second electrode on the electron transport region,
wherein an interface is defined between the light-emitting layer and the hole transport region, and
wherein the hole transport region comprises:
a hole injection layer, and
a hole transport layer on the hole injection layer, the hole transport layer comprising a first portion consisting of the hole transport material and the quantum dots and a fourth portion not comprising the quantum dots, and
wherein, in the first portion, a distribution density of the quantum dots in a portion adjacent to the light-emitting layer is greater than a distribution density of the quantum dots in a portion adjacent to the fourth portion.
10 . The display device of claim 9 , wherein
the first light-emitting element comprises a first light-emitting layer comprising first quantum dots configured to emit blue light,
the second light-emitting element comprises a second light-emitting layer comprising second quantum dots configured to emit green light, and
the third light-emitting element comprises a third light-emitting layer comprising third quantum dots configured to emit red light.
11 . The display device of claim 10 , wherein
the first light-emitting element comprises a first hole transport region comprising the first quantum dots under the first light-emitting layer,
the second light-emitting element comprises a second hole transport region comprising the second quantum dots under the second light-emitting layer, and
the third light-emitting element comprises a third hole transport region comprising the third quantum dots under the third light-emitting layer.
12 . An electronic device comprising a display device,
the display device comprising first to third light-emitting elements configured to emit light having different wavelengths,
wherein each of the first to third light-emitting elements comprises:
a first electrode;
a light-emitting layer on the first electrode and comprising quantum dots;
a hole transport region between the first electrode and the light-emitting layer and consisting of:
a hole transport material, and
quantum dots the same as those comprised in the light-emitting layer;
an electron transport region on the light-emitting layer; and
a second electrode on the electron transport region,
wherein an interface is defined between the light-emitting layer and the hole transport region, and
wherein the hole transport region comprises:
a hole injection layer, and
a hole transport layer on the hole injection layer, the hole transport layer comprising a first portion consisting of the hole transport material and the quantum dots and a fourth portion not comprising the quantum dots, and
wherein, in the first portion, a distribution density of the quantum dots in a portion adjacent to the light-emitting layer is greater than a distribution density of the quantum dots in a portion adjacent to the fourth portion.