U.S. patent application number 16/203666 was filed with the patent office on 2020-01-30 for quantum dot device and display device.
The applicant listed for this patent is SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Eun Joo JANG, Chan Su KIM, Sung Woo KIM, Tae Ho KIM, Kun Su PARK.
Application Number | 20200035935 16/203666 |
Document ID | / |
Family ID | 69141284 |
Filed Date | 2020-01-30 |
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United States Patent
Application |
20200035935 |
Kind Code |
A1 |
KIM; Chan Su ; et
al. |
January 30, 2020 |
QUANTUM DOT DEVICE AND DISPLAY DEVICE
Abstract
A quantum dot device including an anode and a cathode facing
each other, a quantum dot layer between the anode and the cathode
and electron auxiliary layer between the quantum dot layer and the
cathode, wherein the electron auxiliary layer includes at least one
nanoparticle represented by Chemical Formula 1 and at least one
metal halide represented by Chemical Formula 2, and a display
device. Zn.sub.1-xM.sub.xO Chemical Formula 1 Q.sup.+X.sup.-
Chemical Formula 2
Inventors: |
KIM; Chan Su; (Seoul,
KR) ; KIM; Tae Ho; (Suwon-si, KR) ; PARK; Kun
Su; (Seongnam-si, KR) ; KIM; Sung Woo;
(Hwaseong-si, KR) ; JANG; Eun Joo; (Suwon-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRONICS CO., LTD. |
Suwon-si |
|
KR |
|
|
Family ID: |
69141284 |
Appl. No.: |
16/203666 |
Filed: |
November 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/0037 20130101;
H01L 2251/552 20130101; H01L 2251/5369 20130101; H01L 51/0039
20130101; B82Y 40/00 20130101; H01L 51/5072 20130101; H01L 2251/305
20130101; B82Y 20/00 20130101; H01L 51/502 20130101; C09K 11/883
20130101 |
International
Class: |
H01L 51/50 20060101
H01L051/50; C09K 11/88 20060101 C09K011/88; H01L 51/00 20060101
H01L051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2018 |
KR |
10-2018-0085986 |
Claims
1. A quantum dot device, comprising an anode and a cathode facing
each other, a quantum dot layer between the anode and the cathode,
and an electron auxiliary layer between the quantum dot layer and
the cathode, wherein the electron auxiliary layer comprises at
least one nanoparticle represented by Chemical Formula 1 and at
least one metal halide represented by Chemical Formula 2:
Zn.sub.1-xM.sub.xO Chemical Formula 1 wherein, in Chemical Formula
1, M is Mg, Co, Ni, Zr, Mn, Sn, Y, Al, or a combination thereof,
and 0.ltoreq.x<0.5, Q.sup.+X.sup.- Chemical Formula 2 wherein,
in Chemical Formula 2, Q is Zn, Na, K, Li, or a combination
thereof, and X is a halogen.
2. The quantum dot device of claim 1, wherein the metal halide is
present between the nanoparticles.
3. The quantum dot device of claim 1, wherein the nanoparticle is
passivated by the metal halide.
4. The quantum dot device of claim 1, wherein the metal halide is
bound to a surface of the nanoparticle.
5. The quantum dot device of claim 1, wherein the nanoparticle has
an average particle diameter of less than or equal to about 10
nanometers.
6. The quantum dot device of claim 1, wherein the metal halide is
present in an amount of about 3 to about 20 parts by weight
relative to 100 parts by weight of the nanoparticle.
7. The quantum dot device of claim 1, wherein the nanoparticle
comprises a ligand bound to a surface of the nanoparticle.
8. The quantum dot device of claim 7, wherein the ligand comprises
an acetate, a carboxylate, a cyano group, an amine, an amide, a
nitride, a nitrate, a sulfonyl, or a combination thereof.
9. The quantum dot device of claim 7, wherein the metal halide is
bound to the ligand.
10. The quantum dot device of claim 1, wherein a difference between
lowest unoccupied molecular orbital energy levels of the quantum
dot layer and the electron auxiliary layer is greater than a
difference between lowest unoccupied molecular orbital energy
levels of the quantum dot layer and a layer comprising the
nanoparticle.
11. The quantum dot device of claim 10, wherein a lowest unoccupied
molecular orbital energy level of the quantum dot layer ranges from
about 2.5 electron volts to about 3.6 electron volts and a lowest
unoccupied molecular orbital energy level of the electron auxiliary
layer ranges from about 3.7 electron volts to about 5.3 electron
volts.
12. The quantum dot device of claim 1, wherein the nanoparticle and
the metal halide are present as a mixture.
13. The quantum dot device of claim 1, wherein the quantum dot
layer comprises a non-cadmium quantum dot.
14. The quantum dot device of claim 13, wherein the quantum dot
comprises zinc and tellurium, selenium, or a combination thereof,
or indium (In) and zinc, phosphorus, or a combination thereof.
15. The quantum dot device of claim 14, wherein the quantum dot
comprises a core comprising zinc and tellurium, selenium, or a
combination thereof or indium and zinc, phosphorus, or a
combination thereof and a shell on at least a part of the core, the
shell having a different composition from the core.
16. The quantum dot device of claim 15, wherein the shell comprises
ZnSeS, ZnS, or a combination thereof.
17. A method of manufacturing a quantum dot device, comprising
forming an anode, forming a quantum dot layer on the anode, forming
an electron auxiliary layer on the quantum dot layer, and forming a
cathode on the electron auxiliary layer, wherein the forming of the
electron auxiliary layer comprises mixing a Zn precursor and
optionally a precursor comprising M, wherein M is Mg, Co, Ni, Zr,
Mn, Sn, Y, Al, or a combination thereof, in a first solvent to
prepare a first solution, preparing a second solution comprising a
nanoparticle represented by Zn.sub.1-xM.sub.xO, wherein
0.ltoreq.x<0.5, through a sol-gel reaction of the first
solution, dissolving a metal halide represented by Q.sup.+X.sup.-,
wherein Q is Zn, Na, K, Li, or a combination thereof and X is a
halogen, in a second solvent to prepare a third solution, preparing
a mixed solution of the second solution and the third solution, and
coating the mixed solution on the quantum dot layer to manufacture
the quantum dot device.
18. The method of claim 17, wherein the first solvent and the
second solvent comprise the same or different alcohols.
19. The method of claim 17, wherein the metal halide in the mixed
solution is present in an amount of about 3 to about 20 parts by
weight relative to 100 parts by weight of the nanoparticle.
20. A display device comprising the quantum dot device of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2018-0085986 filed in the Korean
Intellectual Property Office on Jul. 24, 2018, and all the benefits
accruing therefrom under 35 U.S.C. .sctn. 119, the entire contents
of which are incorporated herein by reference.
BACKGROUND
1. Field
[0002] A quantum dot device and a display device are disclosed.
2. Description of the Related Art
[0003] Physical characteristics (e.g., energy bandgaps, melting
points, etc.) of nanoparticles that are intrinsic characteristics
may be controlled by changing the particle sizes of the
nanoparticles, unlike bulk materials. For example, semiconductor
nanocrystal particles, also known as quantum dots, are supplied
with photoenergy or electrical energy and may emit light in a
wavelength corresponding to sizes of the quantum dots. Accordingly,
the quantum dots may be used as a light emitting element emitting
light of a particular wavelength.
SUMMARY
[0004] A quantum dot device may use quantum dots as a light
emitting element. However, the quantum dots are different from a
conventional light emitting element, and a method of improving
performance of the quantum dot device is desired.
[0005] An embodiment is to provide a quantum dot device capable of
realizing improved performance.
[0006] An embodiment provides an electronic device including the
quantum dot device.
[0007] According to an embodiment, a quantum dot device includes an
anode and a cathode facing each other, a quantum dot layer between
the anode and the cathode, and an electron auxiliary layer between
the quantum dot layer and the cathode, wherein the electron
auxiliary layer includes at least one nanoparticle represented by
Chemical Formula 1 and at least one metal halide represented by
Chemical Formula 2.
Zn.sub.1-xM.sub.xO Chemical Formula 1
[0008] In Chemical Formula 1,
[0009] M is Mg, Co, Ni, Zr, Mn, Sn, Y, Al, or a combination
thereof, and
[0010] 0.ltoreq.x<0.5,
Q.sup.+X.sup.- Chemical Formula 2
[0011] wherein, in Chemical Formula 2,
[0012] Q is Zn, Na, K, Li, or a combination thereof, and
[0013] X is a halogen.
[0014] The metal halide may be present between the
nanoparticles.
[0015] The nanoparticle may be passivated by the metal halide.
[0016] The metal halide may be bound to the surface of the
nanoparticle.
[0017] The nanoparticle may have an average particle diameter of
less than or equal to about 10 nanometers (nm).
[0018] The metal halide may be present in an amount of about 3 to
about 20 parts by weight relative to 100 parts by weight of the
nanoparticle.
[0019] The nanoparticle may include a ligand bound to a surface of
the nanoparticle.
[0020] The ligand may include an acetate, a carboxylate, a cyano
group, an amine, an amide, a nitride, a nitrate, a sulfonyl, or a
combination thereof.
[0021] The metal halide may be bound to the ligand.
[0022] A difference between lowest unoccupied molecular orbital
(LUMO) energy levels of the quantum dot layer and the electron
auxiliary layer may be greater than a difference between LUMO
energy levels of the quantum dot layer and a layer including the
nanoparticle.
[0023] A LUMO energy level of the quantum dot layer may range from
about 2.5 electron volts (eV) to about 3.6 eV and a LUMO energy
level of the electron auxiliary layer may range from about 3.7 eV
to about 5.3 eV.
[0024] The nanoparticle and the metal halide may be present as a
mixture.
[0025] The quantum dot layer may include a non-cadmium quantum
dot.
[0026] The quantum dot may include zinc (Zn) and tellurium (Te)
selenium (Se), or a combination thereof, or indium (In) and zinc
(Zn), phosphorus (P), or a combination thereof.
[0027] The quantum dot may include a core including zinc (Zn) and
tellurium (Te), selenium (Se), or a combination thereof or indium
(In) and zinc (Zn), phosphorus (P), or a combination thereof and a
shell disposed on at least a part of the core, the shell having a
different composition from the core.
[0028] The shell may include ZnSeS, ZnS, or a combination
thereof.
[0029] According to an embodiment, a method of manufacturing a
quantum dot device includes forming an anode, forming a quantum dot
layer on the anode, forming an electron auxiliary layer on the
quantum dot layer, and forming a cathode on the electron auxiliary
layer, wherein the forming of the electron auxiliary layer includes
mixing a Zn precursor and optionally a precursor comprising M
(wherein M is Mg, Co, Ni, Zr, Mn, Sn, Y, Al, or a combination
thereof) in a first solvent to prepare a first solution, preparing
a second solution including a nanoparticle represented by
Zn.sub.1-xM.sub.xO (wherein 0.ltoreq.x<0.5) through a sol-gel
reaction of the first solution, dissolving a metal halide
represented by Q.sup.+X.sup.- (wherein Q is Zn, Na, K, Li, or a
combination thereof and X is a halogen) in a second solvent to
prepare a third solution, preparing a mixed solution of the second
solution and the third solution, and coating the mixed solution on
the quantum dot layer.
[0030] The first solvent and the second solvent may include the
same or different alcohols.
[0031] The metal halide in the mixed solution may be present in an
amount of about 3 to about 20 parts by weight relative to 100 parts
by weight of the nanoparticle.
[0032] According to an embodiment, a display device includes the
quantum dot device.
[0033] Performance of the quantum dot device may be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The above and other advantages and features of this
disclosure will become more apparent by describing in further
detail exemplary embodiments thereof with reference to the
accompanying drawings, in which:
[0035] FIG. 1 is a schematic cross-sectional view of a quantum dot
device according to an embodiment,
[0036] FIG. 2 is a photograph showing changes of the solutions of
Preparation Examples 1 and 2 and Comparative Preparation Example 1
after being allowed to stand at a high temperature,
[0037] FIG. 3 is a scanning electron microscopy (SEM) photograph of
a thin film formed of the solution of Preparation Example 2,
and
[0038] FIG. 4 is a SEM photograph of a thin film formed of the
solution of Comparative Preparation Example 1.
DETAILED DESCRIPTION
[0039] Hereinafter, example embodiments of the present disclosure
will be described in detail so that a person skilled in the art
would understand the same. This disclosure may, however, be
embodied in many different forms and is not construed as limited to
the example embodiments set forth herein.
[0040] In the drawings, the thickness of layers, films, panels,
regions, etc., are exaggerated for clarity. Like reference numerals
designate like elements throughout the specification. It will be
understood that when an element such as a layer, film, region, or
substrate is referred to as being "on" another element, it can be
directly on the other element or intervening elements may also be
present. In contrast, when an element is referred to as being
"directly on" another element, there are no intervening elements
present.
[0041] It will be understood that, although the terms "first,"
"second," "third" etc. may be used herein to describe various
elements, components, regions, layers and/or sections, these
elements, components, regions, layers and/or sections should not be
limited by these terms. These terms are only used to distinguish
one element, component, region, layer or section from another
element, component, region, layer or section. Thus, "a first
element," "component," "region," "layer" or "section" discussed
below could be termed a second element, component, region, layer or
section without departing from the teachings herein.
[0042] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting. As
used herein, the singular forms "a," "an," and "the" are intended
to include the plural forms, including "at least one," unless the
content clearly indicates otherwise. "At least one" is not to be
construed as limiting "a" or "an." "Or" means "and/or." As used
herein, the term "and/or" includes any and all combinations of one
or more of the associated listed items. It will be further
understood that the terms "comprises" and/or "comprising," or
"includes" and/or "including" when used in this specification,
specify the presence of stated features, regions, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, regions,
integers, steps, operations, elements, components, and/or groups
thereof.
[0043] "About" as used herein is inclusive of the stated value and
means within an acceptable range of deviation for the particular
value as determined by one of ordinary skill in the art,
considering the measurement in question and the error associated
with measurement of the particular quantity (i.e., the limitations
of the measurement system). For example, "about" can mean within
one or more standard deviations, or within .+-.30%, 20%, 10% or 5%
of the stated value.
[0044] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
disclosure belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0045] Exemplary embodiments are described herein with reference to
cross section illustrations that are schematic illustrations of
idealized embodiments. As such, variations from the shapes of the
illustrations as a result, for example, of manufacturing techniques
and/or tolerances, are to be expected. Thus, embodiments described
herein should not be construed as limited to the particular shapes
of regions as illustrated herein but are to include deviations in
shapes that result, for example, from manufacturing. For example, a
region illustrated or described as flat may, typically, have rough
and/or nonlinear features. Moreover, sharp angles that are
illustrated may be rounded. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the precise shape of a region and are not intended to
limit the scope of the present claims.
[0046] Hereinafter, a work function or a highest occupied molecular
orbital (HOMO) energy level is expressed as an absolute value from
a vacuum level. In addition, when the work function or the HOMO
energy level is referred to be "deep," "high" or "large," the work
function or the HOMO energy level has a large absolute value based
on "0 eV" of the vacuum level, while when the work function or the
HOMO energy level is referred to be "shallow," "low," or "small,"
the work function or HOMO energy level has a small absolute value
based on "0 eV" of the vacuum level.
[0047] Hereinafter, a quantum dot device according to an embodiment
is described with reference to drawings.
[0048] FIG. 1 is a schematic cross-sectional view of a quantum dot
device according to an embodiment.
[0049] Referring to FIG. 1, a quantum dot device 10 according to an
embodiment includes a first electrode 11 and a second electrode 15
facing each other, a quantum dot layer 13 disposed between the
first electrode 11 and the second electrode 15, a hole auxiliary
layer 12 disposed between the first electrode 11 and the quantum
dot layer 13, and an electron auxiliary layer 14 disposed between
the quantum dot layer 13 and the second electrode 15.
[0050] A substrate may be disposed at the side of the first
electrode 11 or the second electrode 15. The substrate may be for
example made of an inorganic material such as glass; an organic
material such as polycarbonate, polymethylmethacrylate,
polyethyleneterephthalate, polyethylenenaphthalate, polyamide,
polyethersulfone, or a combination thereof; or a silicon wafer. The
substrate may be omitted.
[0051] One of the first electrode 11 and the second electrode 15 is
an anode and the other is a cathode. For example, the first
electrode 11 may be an anode and the second electrode 15 may be a
cathode.
[0052] The first electrode 11 may be made of a conductor having
high work function, and may be for example made of a metal, a
conductive metal oxide, or a combination thereof. The first
electrode 11 may be for example made of a metal or an alloy thereof
such as nickel, platinum, vanadium, chromium, copper, zinc, and
gold; a conductive metal oxide such as zinc oxide, indium oxide,
tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or
fluorine doped tin oxide; or a combination of metal and oxide such
as ZnO and Al or SnO.sub.2 and Sb, but is not limited thereto.
[0053] The second electrode 15 may be for example made of a
conductor having a lower work function than the first electrode 11,
and may be for example made of a metal, a conductive metal oxide, a
conductive polymer, or a combination thereof. The second electrode
15 may be for example a metal or an alloy thereof such as aluminum,
magnesium, calcium, sodium, potassium, titanium, indium, yttrium,
lithium, gadolinium silver, tin, lead, cesium, barium, and the
like; a multi-layer structure material such as LiF/Al,
LiO.sub.2/Al, Liq/Al, LiF/Ca, and BaF.sub.2/Ca, but is not limited
thereto.
[0054] A work function of the first electrode 11 may be higher than
that of the second electrode 15. For example, the work function of
the first electrode 11 may be for example about 4.5 eV to about 5.0
eV and the work function of the second electrode 15 may be for
example greater than or equal to about 4.0 eV and less than about
4.5 eV. Within the ranges, the work function of the first electrode
11 may be for example about 4.6 eV to about 4.9 eV and the work
function of the second electrode 15 may be for example about 4.0 eV
to about 4.3 eV.
[0055] The first electrode 11, the second electrode 15, or a
combination thereof may be a light-transmitting electrode and the
light-transmitting electrode may be for example made of a
conductive oxide such as zinc oxide, indium oxide, tin oxide,
indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine doped
tin oxide, or a metal thin layer of a single layer or a multilayer.
When one of the first electrode 11 and the second electrode 15 is a
non-light-transmitting electrode, it may be made of for example an
opaque conductor such as aluminum (Al), silver (Ag), or gold
(Au).
[0056] The quantum dot layer 13 includes a quantum dot. The quantum
dot may be a semiconductor nanocrystal, and may have various
shapes, for example an isotropic semiconductor nanocrystal, a
quantum rod, and a quantum plate. Herein, the quantum rod may
indicate a quantum dot having an aspect ratio of greater than about
1:1, for example an aspect ratio of greater than or equal to about
2:1, greater than or equal to about 3:1, or greater than or equal
to about 5:1. For example, the quantum rod may have an aspect ratio
of less than or equal to about 50:1, of less than or equal to about
30:1, or of less than or equal to about 20:1.
[0057] The quantum dot may have for example a particle diameter (an
average largest particle diameter for a non-spherical shape) of for
example about 1 nm to about 100 nm, about 1 nm to about 80 nm,
about 1 nm to about 50 nm, or about 1 nm to about 20 nm.
[0058] Energy bandgaps of quantum dots may be controlled according
to sizes and compositions of the quantum dots, and thus
photoluminescence wavelength may be controlled. For example, as the
sizes of quantum dots increase, the quantum dots may have narrow
energy bandgaps and thus emit light in a relatively long wavelength
region while as the sizes of the quantum dots decrease, the quantum
dots may have wide energy bandgap and thus emit light in a
relatively short wavelength region.
[0059] For example, the quantum dot may emit for example light in a
predetermined wavelength region of a visible ray region according
to its size composition, or a combination thereof. For example, the
quantum dot may emit blue light, red light, or green light, and the
blue light may have for example a peak emission wavelength in about
430 nm to about 470 nm, the red light may have for example a peak
emission wavelength in about 600 nm to about 650 nm, and the green
light may have for example a peak emission wavelength in about 520
nm to about 550 nm. For example, the quantum dot may emit blue
light having a peak emission wavelength in a wavelength of about
430 nm to about 470 nm.
[0060] For example, an average size of the blue light emitting
quantum dot may be for example less than or equal to about 4.5 nm,
less than or equal to about 4.3 nm, less than or equal to about 4.2
nm, less than or equal to about 4.1 nm, or less than or equal to
4.0 nm. Within the ranges, it may be for example about 2.0 nm to
about 4.5 nm, about 2.0 nm to about 4.3 nm, about 2.0 nm to about
4.2 nm, about 2.0 about nm to about 4.1 nm, or about 2.0 nm to
about 4.0 nm.
[0061] The quantum dot may have for example a quantum yield of
greater than or equal to about 10%, greater than or equal to about
30%, greater than or equal to about 50%, greater than or equal to
about 60%, greater than or equal to about 70%, or greater than or
equal to about 90%.
[0062] The quantum dot may have a relatively narrow full width at
half maximum (FWHM). Herein, the FWHM a width of a wavelength
corresponding to a half of a peak absorption point and as the FWHM
is narrower, light in a narrower wavelength region may be emitted
and high color purity may be obtained. The quantum dot may have for
example a FWHM of less than or equal to about 50 nm, less than or
equal to about 49 nm, less than or equal to about 48 nm, less than
or equal to about 47 nm, less than or equal to about 46 nm, less
than or equal to about 45 nm, less than or equal to about 44 nm,
less than or equal to about 43 nm, less than or equal to about 42
nm, less than or equal to about 41 nm, less than or equal to about
40 nm, less than or equal to about 39 nm, less than or equal to
about 38 nm, less than or equal to about 37 nm, less than or equal
to about 36 nm, less than or equal to about 35 nm, less than or
equal to about 34 nm, less than or equal to about 33 nm, less than
or equal to about 32 nm, less than or equal to about 31 nm, less
than or equal to about 30 nm, less than or equal to about 29 nm, or
less than or equal to about 28 nm.
[0063] For example, the quantum dot may be for example a Group
II-VI semiconductor compound, a Group III-V semiconductor compound,
a Group IV-VI semiconductor compound, a Group IV semiconductor
compound, a Group I-III-VI semiconductor compound, a Group
I--II-IV-VI semiconductor compound, a Group II-III-V semiconductor
compound, or a combination thereof. The Group II-VI semiconductor
compound may be for example a binary element compound of CdSe,
CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or a
combination thereof; a ternary element compound of CdSeS, CdSeTe,
CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe,
CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe,
MgZnS, or a combination thereof; or a quaternary element compound
of ZnSeSTe, HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe,
CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or a combination thereof, but
is not limited thereto. The Group III-V semiconductor compound may
be for example a binary element compound of GaN, GaP, GaAs, GaSb,
AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or a combination
thereof; a ternary element compound of GaNP, GaNAs, GaNSb, GaPAs,
GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs,
InPSb, GaAlNP, or a combination thereof; or a quaternary element
compound of GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GalnNP, GalnNAs,
GalnNSb, GalnPAs, GalnPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs,
InAlPSb, or a combination thereof, but is not limited thereto. The
Group IV-VI semiconductor compound may be for example a binary
element compound of SnS, SnSe, SnTe, PbS, PbSe, PbTe, or a
combination thereof; a ternary element compound of SnSeS, SnSeTe,
SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or a
combination thereof; or a quaternary element compound of SnPbSSe,
SnPbSeTe, SnPbSTe, or a combination thereof, but is not limited
thereto. The Group IV semiconductor compound may be for example a
singular element semiconductor compound of Si, Ge, or a combination
thereof; and a binary element semiconductor compound of SiC, SiGe,
or a combination thereof, but is not limited thereto. The Group
I-III-VI semiconductor compound may be for example of CuInSe.sub.2,
CuInS.sub.2, CuInGaSe, CuInGaS, or a combination thereof, but is
not limited thereto. The Group I-II-IV-VI semiconductor compound
may be for example of CuZnSnSe and CuZnSnS, but is not limited
thereto. The Group II-III-V semiconductor compound may include for
example InZnP, but is not limited thereto.
[0064] The quantum dot may include the binary semiconductor
compound, the ternary semiconductor compound, or the quaternary
semiconductor compound in a substantially uniform concentration or
partially different concentration distributions.
[0065] For example, the quantum dot may include a non-cadmium-based
quantum dot. Cadmium (Cd) may cause severe environment/health
problems and a restricted element by Restriction of Hazardous
Substances Directive (RoHS) in a plurality of countries, and thus
the non-cadmium-based quantum dot may be effectively used.
[0066] For example, the quantum dot may be a semiconductor compound
including zinc (Zn) and tellurium (Te), selenium (Se), or a
combination thereof. For example, the quantum dot may be a Zn--Te
semiconductor compound, a Zn--Se semiconductor compound, a
Zn--Te--Se semiconductor compound, or a combination thereof. For
example, in the Zn--Te--Se semiconductor compound, an amount of
tellurium (Te) may be less than that of selenium (Se). The
semiconductor compound may emit blue light having a peak emission
wavelength in a wavelength region of less than or equal to about
470 nm, for example in a wavelength region of about 430 nm to about
470 nm.
[0067] For example, the quantum dot may be for example a
semiconductor compound including indium (In) and zinc (Zn),
phosphorus (P), or a combination thereof. For example, the quantum
dot may be an In--Zn semiconductor compound, an In--P semiconductor
compound, an In--Zn--P semiconductor compound, or a combination
thereof. For example, in the In--Zn semiconductor compound or the
In--Zn--P semiconductor compound, a mole ratio of zinc (Zn)
relative to indium (In) may be greater than or equal to about 25:1.
The semiconductor compound may emit blue light having a peak
emission wavelength in a wavelength region of less than or equal to
about 470 nm, for example in a wavelength region of about 430 nm to
about 470 nm.
[0068] The quantum dot may have a core-shell structure wherein a
shell surrounds a core. For example, the core and the shell of the
quantum dot may have an interface, and an element of at least one
of the core or the shell in the interface may have a concentration
gradient wherein the concentration of the element(s) of the shell
decreases toward the core. For example, a material composition of
the shell of the quantum dot has a higher energy bandgap than a
material composition of the core of the quantum dot, and thereby
the quantum dot may exhibit a quantum confinement effect.
[0069] The quantum dot may have one quantum dot core and a
multi-layered quantum dot shell surrounding the core. Herein, the
multi-layered shell has at least two shells wherein each shell
independently may be a single composition, an alloy, or have a
concentration gradient.
[0070] For example, a shell of a multi-layered shell that is
farther from the core may have a higher energy bandgap than a shell
that is closer to the core, and thereby the quantum dot may exhibit
a quantum confinement effect.
[0071] For example, the quantum dot having a core-shell structure
may for example include a core including a first semiconductor
compound including zinc (Zn) and tellurium (Te), selenium (Se), or
a combination thereof and a shell disposed on at least a part of
the core and including a second semiconductor compound having a
different composition from that of the core.
[0072] A Zn--Te--Se-based first semiconductor compound may be for
example a Zn--Se-based semiconductor compound including a
relatively small amount of tellurium (Te) and, for example, a
semiconductor compound represented by ZnTe.sub.xSe.sub.1-x
(wherein, x is greater than about 0 and less than or equal to about
0.05).
[0073] For example, in the Zn--Te--Se-based first semiconductor
compound, the mole amount of zinc (Zn) may be greater than that of
selenium (Se), and the mole amount of selenium (Se) may be greater
than that of tellurium (Te). For example, in the first
semiconductor compound, a mole ratio of tellurium (Te) relative to
selenium (Se) may be less than or equal to about 0.05:1, less than
or equal to about 0.049:1, less than or equal to about 0.048:1,
less than or equal to about 0.047:1, less than or equal to about
0.045:1, less than or equal to about 0.044:1, less than or equal to
about 0.043:1, less than or equal to about 0.042:1, less than or
equal to about 0.041:1, less than or equal to about 0.04:1, less
than or equal to about 0.039:1, less than or equal to about
0.035:1, less than or equal to about 0.03:1, less than or equal to
about 0.02:19, less than or equal to about 0.025:1, less than or
equal to about 0.024:1, less than or equal to about 0.023:1, less
than or equal to about 0.022:1, less than or equal to about
0.021:1, less than or equal to about 0.02:1, less than or equal to
about 0.019:1, less than or equal to about 0.018:1, less than or
equal to about 0.017:1, less than or equal to about 0.016:1, less
than or equal to about 0.015:1, less than or equal to about
0.014:1, less than or equal to about 0.013:1, less than or equal to
about 0.012:1, less than or equal to about 0.011:1, or less than or
equal to about 0.01:1. For example, in the first semiconductor
compound, a mole ratio of tellurium (Te) relative to zinc (Zn) may
be less than or equal to about 0.02:1, less than or equal to about
0.019:1, less than or equal to about 0.018:1, less than or equal to
about 0.017:1, less than or equal to about 0.016:1, less than or
equal to about 0.015:1, less than or equal to about 0.014:1, less
than or equal to about 0.013:1, less than or equal to about
0.012:1, less than or equal to about 0.011:1, or less than or equal
to about 0.010:1.
[0074] The second semiconductor compound may include for example a
Group II-VI semiconductor compound, a Group III-V semiconductor
compound, a Group IV-VI semiconductor compound, a Group IV
semiconductor compound, a Group I-III-VI semiconductor compound, a
Group I-II-IV-VI semiconductor compound, a Group II-III-V
semiconductor compound, or a combination thereof. Examples of the
Group II-VI semiconductor compound, the Group III-V semiconductor
compound, the Group IV-VI semiconductor compound, the Group IV
semiconductor compound, the Group I-III-VI semiconductor compound,
the Group I--II-IV-VI semiconductor compound, and the Group
II-III-V semiconductor compound are the same as described
above.
[0075] For example, the second semiconductor compound may include
zinc (Zn), selenium (Se), sulfur (S), or a combination thereof. For
example, the shell may include at least one internal shell disposed
close to the core and an outermost shell disposed as the outermost
shell of the quantum dot and the internal shell may include ZnSeS
and the outermost shell may include SnS. For example, the shell may
have a concentration gradient of one component and for example an
amount of sulfur (S) may increase in a direction away from the
core.
[0076] For example, the quantum dot having a core-shell structure
may include for example a core including a third semiconductor
compound including indium (In) and zinc (Zn), phosphorus (P), or a
combination thereof and a shell disposed on at least a part of the
core and including a fourth semiconductor compound having a
different composition from the core.
[0077] In the In--Zn--P-based third semiconductor compound, a mole
ratio of zinc (Zn) relative to indium (In) may be greater than or
equal to about 25:1. For example, in the In--Zn--P-based first
semiconductor compound, the mole ratio of zinc (Zn) relative to
indium (In) may be greater than or equal to about 28:1, greater
than or equal to about 29:1, or greater than or equal to about
30:1. For example, in the In--Zn--P-based first semiconductor
compound, the mole ratio of zinc (Zn) relative to indium (In) may
be less than or equal to about 55:1, for example less than or equal
to about 50:1, less than or equal to about 45:1, less than or equal
to about 40:1, less than or equal to about 35:1, less than or equal
to about 34:1, less than or equal to about 33:1, or less than or
equal to about 32:1.
[0078] The fourth semiconductor compound may include for example a
Group II-VI semiconductor compound, a Group III-V semiconductor
compound, a Group IV-VI semiconductor compound, a Group IV
semiconductor compound, a Group I-III-VI semiconductor compound, a
Group I-II-IV-VI semiconductor compound, a Group II-III-V
semiconductor compound, or a combination thereof. Examples of the
Group II-VI semiconductor compound, the Group III-V semiconductor
compound, the Group IV-VI semiconductor compound, the Group IV
semiconductor compound, the Group I-III-VI semiconductor compound,
the Group I--II-IV-VI semiconductor compound, and the Group
II-III-V semiconductor compound are the same as described
above.
[0079] For example, the fourth semiconductor compound may include
zinc (Zn) and sulfur (S), and optionally selenium (Se). For
example, the shell may include at least one internal shell disposed
close to the core and an outermost shell disposed as the outermost
shell of the quantum dot and the internal shell, the outermost
shell, or a combination thereof may include the fourth
semiconductor compound of ZnS or ZnSeS.
[0080] The quantum dot layer 13 may have for example a thickness of
about 5 nm to about 200 nm, for example about 10 nm to about 150
nm, about 10 nm to about 100 nm, or about 10 nm to about 50 nm.
[0081] The quantum dot layer 13 may have a relatively high HOMO
energy level and may be for example a HOMO energy level of greater
than or equal to about 5.4 eV, greater than or equal to about 5.6
eV, greater than or equal to about 5.7 eV, greater than or equal to
about 5.8 eV, greater than or equal to about 5.9 eV or greater than
or equal to about 6.0 eV. The HOMO energy level of the quantum dot
layer 13 may be for example about 5.4 eV to about 7.0 eV, about 5.4
eV to about 6.8 eV, about 5.4 eV to about 6.7 eV, about 5.4 eV to
about 6.5 eV, about 5.4 eV to about 6.3 eV, about 5.4 eV to about
6.2 eV, or about 5.4 eV to about 6.1 eV, within the ranges, for
example about 5.6 eV to about 7.0 eV, about 5.6 eV to about 6.8 eV,
about 5.6 eV to about 6.7 eV, about 5.6 eV to about 6.5 eV, about
5.6 eV to about 6.3 eV, about 5.6 eV to about 6.2 eV, or about 5.6
eV to about 6.1 eV, for example about 5.7 eV to about 7.0 eV, about
5.7 eV to about 6.8 eV, about 5.7 eV to about 6.7 eV, about 5.7 eV
to about 6.5 eV, about 5.7 eV to about 6.3 eV, about 5.7 eV to
about 6.2 eV, or about 5.7 eV to about 6.1 eV, for example about
5.8 eV to about 7.0 eV, about 5.8 eV to about 6.8 eV, about 5.8 eV
to about 6.7 eV, about 5.8 eV to about 6.5 eV, about 5.8 eV to
about 6.3 eV, about 5.8 eV to about 6.2 eV, about 5.8 eV to about
6.1 eV, for example about 6.0 eV to about 7.0 eV, about 6.0 eV to
about 6.8 eV, about 6.0 eV to about 6.7 eV, about 6.0 eV to about
6.5 eV, about 6.0 eV to about 6.3 eV, or about 6.0 eV to about 6.2
eV.
[0082] The quantum dot layer 13 may have a relatively low LUMO
energy level, and may have for example an LUMO energy level of less
than or equal to about 3.6 eV, for example less than or equal to
about 3.5 eV, less than or equal to about 3.4 eV, less than or
equal to about 3.3 eV, less than or equal to about 3.2 eV, or less
than or equal to about 3.0 eV. The LUMO energy level of the quantum
dot layer 13 may be for example about 2.5 eV to about 3.6 eV, about
2.5 eV to about 3.5 eV, about 2.5 eV to about 3.4 eV, about 2.5 eV
to about 3.3 eV, about 2.5 eV to about 3.2 eV, about 2.5 eV to
about 3.1 eV, or about 2.5 eV to about 3.0 eV.
[0083] The quantum dot layer 13 may have an energy bandgap of about
2.4 eV to about 2.9 eV. Within the ranges, it may have for example
an energy bandgap of about 2.4 eV to about 2.8 eV, for example
about 2.4 eV to about 2.78 eV.
[0084] The hole auxiliary layer 12 is disposed between the first
electrode 11 and the quantum dot layer 13. The hole auxiliary layer
12 may have one layer or two or more layers, may for example help
ease injection and/or transport of charges such as holes from the
first electrode 11 into the quantum dot layer 13, and may include
for example a hole injection layer, a hole transport layer, an
electron blocking layer, or a combination thereof.
[0085] The hole auxiliary layer 12 may have a relatively high HOMO
energy level so that it may match a HOMO energy level of the
quantum dot layer 13. Accordingly, mobility of holes from the hole
auxiliary layer 12 into the quantum dot layer 13 may be
increased.
[0086] The hole auxiliary layer 12 may have the same HOMO energy
level as the quantum dot layer 13 or a lower HOMO energy level than
the quantum dot layer 13 within a difference of about 1.0 eV or
less. For example, a difference between HOMO energy levels of the
hole auxiliary layer 12 and the quantum dot layer 13 may be about 0
eV to about 1.0 eV, for example about 0.01 eV to about 0.8 eV,
about 0.01 eV to about 0.7 eV, about 0.01 eV to about 0.5 eV, about
0.01 eV to about 0.4 eV, about 0.01 eV to about 0.3 eV, about 0.01
eV to about 0.2 eV, or about 0.01 eV to about 0.1 eV.
[0087] The hole auxiliary layer 12 may have a HOMO energy level of
for example greater than or equal to about 5.0 eV, greater than or
equal to about 5.2 eV, greater than or equal to about 5.4 eV,
greater than or equal to about 5.6 eV, or greater than or equal to
about 5.8 eV.
[0088] For example, the hole auxiliary layer 12 may have a HOMO
energy level of about 5.0 eV to about 7.0 eV, for example about 5.2
eV to about 6.8 eV, about 5.4 eV to about 6.8 eV, about 5.4 eV to
about 6.7 eV, about 5.4 eV to about 6.5 eV, about 5.4 eV to about
6.3 eV, about 5.4 eV to about 6.2 eV, about 5.4 eV to about 6.1 eV,
about 5.6 eV to about 7.0 eV, about 5.6 eV to about 6.8 eV, about
5.6 eV to about 6.7 eV, about 5.6 eV to about 6.5 eV, about 5.6 eV
to about 6.3 eV, about 5.6 eV to about 6.2 eV, about 5.6 eV to
about 6.1 eV, about 5.8 eV to about 7.0 eV, about 5.8 eV to about
6.8 eV, about 5.8 eV to about 6.7 eV, about 5.8 eV to about 6.5 eV,
about 5.8 eV to about 6.3 eV, about 5.8 eV to about 6.2 eV, or
about 5.8 eV to about 6.1 eV.
[0089] For example, the hole auxiliary layer 12 may include a hole
injection layer close to the first electrode 11 and a hole
transport layer close to the quantum dot layer 13. Herein, the hole
injection layer may have a HOMO energy level of about 5.0 eV to
about 6.0 eV, about 5.0 eV to about 5.5 eV, or about 5.0 eV to
about 5.4 eV, and the hole transport layer may have a HOMO energy
level of about 5.2 eV to about 7.0 eV, for example about 5.4 eV to
about 6.8 eV, about 5.4 eV to about 6.7 eV, about 5.4 eV to about
6.5 eV, about 5.4 eV to about 6.3 eV, about 5.4 eV to about 6.2 eV,
or about 5.4 eV to about 6.1 eV.
[0090] The hole auxiliary layer 12 may include a suitable material
satisfying the energy level without any particular limit and may be
for example
poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine (TFB),
polyarylamine, poly(N-vinylcarbazole,
poly(3,4-ethylenedioxythiophene) (PEDOT),
poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS),
polyaniline, polypyrrole, N, N,
N',N'-tetrakis(4-methoxyphenyl)-benzidine (TPD),
(4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (.alpha.-NPD),
m-MTDATA (4,4',4''-tris[phenyl(m-tolyl)amino]triphenylamine),
4,4',4''-tris(N-carbazolyl)-triphenylamine (TCTA),
,1-bis[(di-4-tolylamino)phenylcyclohexane (TAPC), a p-type metal
oxide (e.g., NiO, WO.sub.3, MoO.sub.3, etc.), a carbon-based
material such as graphene oxide, or a combination thereof, but is
not limited thereto.
[0091] The electron auxiliary layer 14 is disposed between the
quantum dot layer 13 and the second electrode 15. The electron
auxiliary layer 14 may have one layer or two or more layers, and
may for example help ease injection and/or transport of charges
such as electrons from the second electrode 15 into the quantum dot
layer 13, or may control mobility rates of charges such as
electrons. The electron auxiliary layer 14 may include for example
an electron injection layer, an electron transport layer, an
electron controlling layer, a hole blocking layer, or a combination
thereof, but is not limited thereto.
[0092] The electron auxiliary layer 14 includes at least one
nanoparticle represented by Chemical Formula 1 and at least one
metal halide represented by Chemical Formula 2.
Zn.sub.1-xM.sub.xO Chemical Formula 1
[0093] In Chemical Formula 1,
[0094] M is Mg, Co, Ni, Zr, Mn, Sn, Y, Al, or a combination
thereof, and
[0095] 0.ltoreq.x<0.5,
Q.sup.+X.sup.- Chemical Formula 2
[0096] wherein, in Chemical Formula 2,
[0097] Q is Zn, Na, K, Li, or a combination thereof, and
[0098] X is a halogen.
[0099] The nanoparticle represented by Chemical Formula 1 may be
zinc oxide (ZnO) or zinc oxide on which a metal except, e.g., other
than, zinc is doped.
[0100] For example, M of Chemical Formula 1 may be for example Mg,
Co, Ni, or a combination thereof, but is not limited thereto.
[0101] For example, x of Chemical Formula 1 may satisfy for example
0.01.ltoreq.x.ltoreq.0.4, 0.02.ltoreq.x.ltoreq.0.4,
0.03.ltoreq.x.ltoreq.0.3, or 0.05.ltoreq.x.ltoreq.0.3, but is not
limited thereto.
[0102] An average particle size of the nanoparticle may be for
example less than or equal to about 10 nm.
[0103] For example, an average particle size of the zinc oxide may
be for example about 3.0 nm to about 10.0 nm, for example about 3.5
nm to about 8.0 nm, about 3.5 nm to about 7.0 nm, about 3.5 nm to
about 6.0 nm, about 3.5 nm to about 5.5 nm, about 3.5 nm to about
5.0 nm, about 4.0 nm to about 5.0 nm, or about 4.5 nm to about 5.0
nm.
[0104] For example, an average particle size of the metal-doped
zinc oxide may be less than about 3.5 nm, for example less than or
equal to about 3.4 nm, less than or equal to about 3.3 nm, less
than or equal to about 3.2 nm, less than or equal to about 3.1 nm,
or less than or equal to about 3.0 nm. An average particle size of
a first nanoparticle may be for example greater than or equal to
about 1.2 nm and less than about 3.5 nm, greater than or equal to
about 1.3 nm and less than about 3.4 nm, about 1.5 nm to about 3.3
nm, about 1.8 nm to about 3.3 nm, or about 2.0 nm to about 3.3
nm.
[0105] For example, the electron auxiliary layer 14 may include
zinc oxide.
[0106] For example, the electron auxiliary layer 14 may include
metal (M)-doped zinc oxide.
[0107] For example, the electron auxiliary layer 14 may include a
mixture of zinc oxide and metal (M)-doped zinc oxide.
[0108] The metal halide is an ionic compound including a cation of
Na, K, Li, or a combination thereof and a halogen anion, i.e., a
halide. The cation and anion of the metal halide may be separated
or may be present together in the electron auxiliary layer 14. In
the present specification, the metal halide may refer to a cation
or an anion that are separated from each other as well as a cation
and an anion that are present together.
[0109] The metal halide may be present between the nanoparticles
and for example the metal halide may fill gaps between the
nanoparticles.
[0110] For example, the nanoparticle may be surrounded by the metal
halide and thus passivated.
[0111] For example, the metal halide may be bound to the surface of
the nanoparticle.
[0112] For example, the nanoparticle may include a ligand bound to
the surface, and the metal halide may be bound to the ligand. The
ligand may include an acetate, a carboxylate, a cyano group, an
amine, an amide, a nitride, a nitrate, a sulfonyl, or a combination
thereof, but is not limited thereto.
[0113] The nanoparticle and metal halide have sufficient
miscibility in a solvent, and as aforementioned, the metal halide
surrounds and passivates the surface of the nanoparticle and thus
may increase solution stability and dispersibility. Accordingly,
even when the nanoparticle passivated with the metal halide is
allowed to stand at room temperature or a high temperature for a
long time, neither a precipitate nor agglomerate is not easily
formed, and thus storage stability may be increased.
[0114] In addition, the metal halide fills gaps among the
nanoparticles and thus may form the electron auxiliary layer 14
having a dense structure and accordingly, decrease leakage current
and simultaneously, block holes from passing the quantum dot layer
13 and thus improve efficiency and life-span of a quantum dot
device.
[0115] An amount of the metal halide may be controlled according to
characteristics desired for the electron auxiliary layer 14, and
may be for example about 3 to about 20 parts by weight, based on
100 parts by weight of the nanoparticle. Within the range, solution
stability and dispersibility, and electrical characteristics may be
simultaneously improved. Within the ranges, it may be included in
an amount of about 3 to about 15 parts by weight, about 3 to about
10 parts by weight, about 5 to about 10 parts by weight, or about 5
to about 8 parts by weight.
[0116] The electron auxiliary layer 14 may have a different energy
level from a layer including, e.g., consisting of, zinc oxide and
not including a metal halide (hereinafter, referred to as `a zinc
oxide layer`) and/or a layer including, e.g., consisting of, metal
(M)-doped zinc oxide and not including a metal halide (hereinafter,
referred to as `a metal-doped zinc oxide layer`). For example, a
LUMO energy level of the electron auxiliary layer 14 may be
different from a LUMO energy level of the zinc oxide layer or the
metal-doped zinc oxide layer and for example the LUMO energy level
of the electron auxiliary layer 14 may be deeper than the LUMO
energy level of the zinc oxide layer or the metal-doped zinc oxide
layer. For example, a HOMO energy level of the electron auxiliary
layer 14 may be different from a HOMO energy level of the zinc
oxide layer or the metal-doped zinc oxide layer, and for example
the HOMO energy level of the electron auxiliary layer 14 may be
deeper than the HOMO energy level of the zinc oxide layer or the
metal-doped zinc oxide layer.
[0117] An energy level difference between the quantum dot layer 13
and the electron auxiliary layer 14 may change depending on an
energy level change of the electron auxiliary layer 14. For
example, a difference between LUMO energy levels of the quantum dot
layer 13 and the electron auxiliary layer 14 may be greater than a
difference between LUMO energy levels of the quantum dot layer 13
and the zinc oxide layer or the metal-doped zinc oxide layer.
[0118] For example, a difference between LUMO energy levels of the
quantum dot layer 13 and the electron auxiliary layer 14 may be
greater than a difference between LUMO energy levels of the quantum
dot layer 13 and the zinc oxide layer or the metal-doped zinc oxide
layer by for example about 0.1 eV to about 1.2 eV, about 0.2 eV to
about 1.1 eV, or about 0.3 eV to about 1.1 eV.
[0119] For example, a difference between LUMO energy levels of the
quantum dot layer 13 and the electron auxiliary layer 14 may be
about 1.0 eV to about 2.0 eV, for example about 1.1 eV to about 1.8
eV, or about 1.1 eV to about 1.7 eV.
[0120] For example, the LUMO energy level of the quantum dot layer
13 may be about 2.5 eV to about 3.6 eV and the LUMO energy level of
the electron auxiliary layer 14 may be about 3.7 eV to about 5.3
eV.
[0121] The quantum dot device 10 may further include additional
layers between each layer.
[0122] The hole auxiliary layer 12, the quantum dot layer 13, and
the electron auxiliary layer 14 may be for example formed with a
solution process, for example a spin coating, a slit coating,
inkjet printing, a nozzle printing, spraying a doctor blade
coating, or a combination thereof, but is not limited thereto.
[0123] For example, the electron auxiliary layer 14 may be
manufactured by mixing a Zn salt and optionally an M salt (wherein
M is the same as described above) in a first solvent to prepare a
first solution, preparing a second solution including a
nanoparticle represented by Zn.sub.1-xM.sub.xO (0.ltoreq.x<0.5)
through a sol-gel reaction of the first solution, dissolving a
metal halide represented by Q.sup.+X.sup.- (Q and X are the same as
described above) in a second solvent to prepare a third solution,
preparing a mixed solution of the second solution and the third
solution, and coating the mixed solution on the quantum dot layer
13. A doping amount of the metal-doped nanoparticle may be adjusted
by controlling a supply ratio of the Zn salt and the M salt. Herein
the metal halide may be supplied so that it may be included in an
amount of about 3 to about 20 parts by weight, based on 100 parts
by weight of the nanoparticle. Herein, the first solvent and the
second solvent may be the same or different and may be for example
an alcohol, for example methanol, ethanol, isopropanol, butanol, or
a mixed solvent thereof.
[0124] The quantum dot device may be for example applied to various
electronic devices such as display devices or lighting devices, and
the like.
[0125] Hereinafter, the embodiments are illustrated in more detail
with reference to examples. However, these examples are exemplary,
and the present disclosure is not limited thereto.
Synthesis Example: Synthesis of Quantum Dot
1. Synthesis of ZnTeSe Core
[0126] Selenium (Se) and tellurium (Te) are dispersed in
trioctylphosphine (TOP) to obtain a 2 molar (M) Se/TOP stock
solution and a 0.1 M Te/TOP stock solution. 0.125 millimoles (mmol)
of zinc acetate, 0.25 mmol of oleic acid, and 0.25 mmol of
hexadecylamine are put along with 10 milliliters (mL) of
trioctylamine in a reactor and then, heated at 120.degree. C. under
vacuum. After 1 hour, an atmosphere in the reactor is converted
into nitrogen.
[0127] After heating the reactor at 300.degree. C., the Se/TOP
stock solution and the Te/TOP stock solution are rapidly added
thereto in a Te/Se ratio of 1/25. After 10 minutes, 30 minutes, or
60 minutes, the reaction solution is rapidly cooled down to room
temperature, acetone is added thereto, and a precipitate obtained
by centrifuging the mixture is dispersed in toluene to obtain a
ZnTeSe quantum dot.
2. Synthesis of ZnTeSe Core/ZnSeS Shell Quantum Dot
[0128] 1.8 mmol (0.336 grams (g)) of zinc acetate, 3.6 mmol (1.134
g) of oleic acid, and 10 mL of trioctylamine are put into a flask
and vacuumed at 120.degree. C. for 10 minutes. The inside of flask
is substituted with nitrogen (N.sub.2) and heated at 180.degree. C.
The ZnTeSe core obtained in Synthesis Example 1 is put therein
within 10 seconds, subsequently, 0.04 mmol of Se/TOP is slowly
injected and then heated at 280.degree. C. Then, 0.01 mmol of S/TOP
is put thereto and heated at 320.degree. C. and reacted for 10
minutes. Continuously, a mixed solution of 0.02 mmol of Se/TOP and
0.04 mmol of S/TOP is slowly injected and reacted again for 20
minutes. Then, the step of injecting Se and S by changing the
mixing ratio thereof and reacting the same for 20 minutes is
repeated. The mixed solution of Se and S uses a mixed solution of
0.01 mmol Se/TOP+0.05 mmol S/TOP, a mixed solution (B) of 0.005
mmol Se/TOP+0.1 mmol S/TOP, and a solution of 0.5 mmol S/TOP,
sequentially.
[0129] After completing all the reaction, the reactor is cooled,
the prepared nanocrystal is precipitated with ethanol, and the
obtained nanocrystal is centrifuged with ethanol and dispersed in
toluene to obtain a ZnTeSe/ZnSeS core/shell quantum dot.
Preparation Example: Preparation of Solution for Hole Auxiliary
Layer
Preparation Example 1
[0130] 9.00 mmol of zinc acetate dihydrate and 90 mL of dimethyl
sulfoxide are put into a reactor and heated under air at 60.degree.
C. Subsequently, 15 mmol of tetramethylammonium hydroxide
pentahydrate is dissolved in 30 mL of ethanol and the solution is
put into the reactor at 3 mL per one minute in a dropwise fashion.
After stirring the mixture for 1 hour, the prepared ZnO
nanoparticle and ethyl acetate are centrifuged in a volume ratio of
1:9 and dispersed in ethanol to obtain a solution in which the ZnO
nanoparticle is dispersed.
[0131] Subsequently, a solution prepared by dissolving NaCl (a
concentration: 5 to 20 milligrams per milliliter (mg/mL)) in
methanol is mixed with the solution in which the ZnO nanoparticle
is dispersed (a concentration: 30 to 100 mg/mL) to prepare a
solution for a hole auxiliary layer. Herein, NaCl is supplied in an
amount of 5 parts by weight, based on 100 parts by weight of the
ZnO nanoparticle.
Preparation Example 2
[0132] A solution for a hole auxiliary layer is prepared according
to the same method as Preparation Example 1 except for supplying
NaCl in an amount of 10 parts by weight, based on 100 parts by
weight of the ZnO nanoparticle.
Comparative Preparation Example 1
[0133] A solution for a hole auxiliary layer is prepared according
to the same method as Preparation Example 1 except for not
supplying NaCl.
Preparation Example 3
[0134] 8.07 mmol of zinc acetate dihydrate, 0.93 mmol of magnesium
acetate tetrahydrate, and 90 mL of dimethylsulfoxide are put into a
reactor and heated under air at 60.degree. C. Subsequently, 15 mmol
of tetramethylammonium hydroxide pentahydrate is dissolved in 30 mL
of ethanol and the solution is put into the reactor at 3 mL per one
minute in a dropwise fashion. After stirring the mixture for 1
hour, the prepared Zn.sub.0.85Mg.sub.0.15O nanoparticle and ethyl
acetate are centrifuged in a volume ratio of 1:9 and dispersed in
ethanol to obtain a solution in which the Zn.sub.0.85Mg.sub.0.15O
nanoparticle is dispersed.
[0135] Subsequently, a solution prepared by dissolving NaCl (a
concentration: 5 to 20 mg/mL) in methanol is mixed with the
solution in which the Zn.sub.0.85Mg.sub.0.15O nanoparticle (a
concentration: 30 to 100 mg/mL) is dispersed to prepare a solution
for a hole auxiliary layer. Herein, NaCl is supplied in an amount
of 5 parts by weight, based on 100 parts by weight of the
Zn.sub.0.85Mg.sub.0.15O nanoparticle.
Preparation Example 4
[0136] A solution for a hole auxiliary layer is prepared according
to the same method as Preparation Example 1 except for supplying
NaCl in an amount of 10 parts by weight, based on 100 parts by
weight of the Zn.sub.0.85Mg.sub.0.15O nanoparticle.
Comparative Preparation Example 2
[0137] A solution for a hole auxiliary layer is prepared according
to the same method as Preparation Example 3 except for not
supplying NaCl.
Evaluation I
[0138] High temperature stability of the solutions of Preparation
Examples 1 to 4 and Comparative Preparation Examples 1 and 2 is
evaluated.
[0139] The high temperature stability is confirmed by formation of
agglomerations after placing the solutions of Preparation Examples
1 to 4 and Comparative Preparation Examples 1 and 2 on a 60.degree.
C. hot plate for 2 hours.
[0140] The results are shown in FIG. 2 and Table 1.
[0141] FIG. 2 is a photograph showing changes of the solutions of
Preparation Examples 1 and 2 and Comparative Preparation Example 1
after being allowed to stand at a high temperature.
[0142] In FIG. 2, (a) is the solution according to Comparative
Preparation Example 1, (b) is the solution of Preparation Example
1, and (c) is the solution of Preparation Example 2.
TABLE-US-00001 TABLE 1 Preparation Example 1 Transparent
(agglomerate is not formed) Preparation Example 2 Transparent
(agglomerate is not formed) Comparative Cloudy (agglomerate is
formed) Preparation Example 1 Preparation Example 3 Transparent
(agglomerate is not formed) Preparation Example 4 Transparent
(agglomerate is not formed) Comparative Cloudy (agglomerate is
formed) Preparation Example 2
[0143] Referring to Table 1, agglomerates in the solutions of
Preparation Examples 1 to 4 are not formed even after the solutions
are allowed to stand at a high temperature, but agglomerates in the
solutions according to Comparative Preparation Examples 1 and 2 are
formed after the solutions are allowed to stand at a high
temperature. Accordingly, the solutions of Preparation Examples 1
to 4 show high temperature stability.
Evaluation II
[0144] The solutions of Preparation Example 2 and Comparative
Preparation Example 1 are respectively spin-coated to be 40 nm
thick on a glass plate and heat-treated at 80.degree. C. for 30
minutes.
[0145] A surface morphology of the formed thin film is
confirmed.
[0146] FIG. 3 is a SEM photograph of a thin film formed of the
solution of Preparation Example 2 and FIG. 4 is a SEM photograph of
a thin film formed of the solution according to Comparative
Preparation Example 1.
[0147] Referring to FIGS. 3 and 4, the thin film formed of the
solution of Preparation Example 2 is denser than the solution
according to Comparative Preparation Example 1 and thus shows
improved surface morphology.
Manufacture of Quantum Dot Device
Example 1
[0148] A glass substrate deposited with ITO (work function (WF):
4.8 electron volts (eV)) is surface-treated with an UV-ozone for 15
minutes, spin-coated with a PEDOT:PSS solution (H.C. Starks Co.,
Ltd.), and heat-treated under the air atmosphere at 150.degree. C.
for 10 minutes and then, under an N.sub.2 atmosphere at 150.degree.
C. for 10 minutes to form a 25 nm-thick hole injection layer (HOMO:
5.3 eV and LUMO: 2.7 eV). Subsequently, on the hole injection
layer, a 25 nm-thick hole transport layer (HOMO: 5.6 eV and LUMO:
2.69 eV) is formed by spin-coating
poly[(9,9-dioctylfluorenyl-2,7-diyl-co(4,4'-(N-4-butylphenyl)diphenylamin-
e] solution (TFB) (Sumitomo) and heat-treating the same at
150.degree. C. for 30 minutes. On the hole transport layer, a 25
nm-thick quantum dot layer (HOMO: 5.7 eV and LUMO: 2.97 eV) by
spin-coating the ZnTeSe/ZnSeS core-shell quantum dot obtained in
Synthesis Example and heat-treating the same at 80.degree. C. for
30 minutes. On the quantum dot layer, a nm-thick electron auxiliary
layer (HOMO: 7.82 eV and LUMO: 4.30 eV) by spin-coating the
solution obtained in Preparation Example 1 and heat-treating the
same at 80.degree. C. for 30 minutes. On the electron auxiliary
layer, a second electrode (cathode) is formed by vacuum-depositing
aluminum (Al) to be 90 nm to manufacture a quantum dot device.
Example 2
[0149] A quantum dot device is manufactured according to the same
method as Example 1 except for forming an electron auxiliary layer
(HOMO: 7.82 eV, LUMO: 4.30 eV) by using the solution of Preparation
Example 2 instead of the solution of Preparation Example 1.
Example 3
[0150] A quantum dot device is manufactured according to the same
method as Example 1 except for forming an electron auxiliary layer
(HOMO: 8.81 eV, LUMO: 5.13 eV) by using the solution of Preparation
Example 3 instead of the solution of Preparation Example 1.
Example 4
[0151] A quantum dot device is manufactured according to the same
method as Example 1 except for forming an electron auxiliary layer
(HOMO: 8.81 eV, LUMO: 5.13 eV) by using the solution of Preparation
Example 4 instead of the solution of Preparation Example 1.
Comparative Example 1
[0152] A quantum dot device is manufactured according to the same
method as Example 1 except for forming an electron auxiliary layer
(HOMO: 7.54 eV, LUMO: 4.18 eV) by using the solution according to
Comparative Preparation Example 1 instead of the solution of
Preparation Example 1.
Comparative Example 2
[0153] A quantum dot device is manufactured according to the same
method as Example 1 except for forming an electron auxiliary layer
(HOMO: 8.42 eV, LUMO: 4.74 eV) by using the solution of Comparative
Preparation Example 1 instead of the solution of Preparation
Example 2.
Evaluation III
[0154] Current-voltage-luminescence characteristics of the quantum
dot devices of Examples 1 to 4 and Comparative Examples 1 and 2 are
evaluated.
[0155] The current-voltage-luminescence characteristics are
evaluated by using a Keithley 220 current source and a Minolta
CS200 spectroradiometer.
[0156] The results are shown in Tables 2 and 3.
TABLE-US-00002 TABLE 2 Comparative Example 1 Example 2 Example 1
EQE.sub.max 7.4 5.8 5.8 EQE @500 nit 3.7 4.9 3.2 V @ 5 mA 2.8 2.8
2.9 V @ 100 nit 3.0 3.0 3.2 Lum.sub.max 10300 9220 6450 T50 @500
218 292 100 nit (%) (ref.) .lamda.max 632 634 636
TABLE-US-00003 TABLE 3 Comparative Example 3 Example 4 Example 2
EQE.sub.max 9.6 12.3 6.6 EQE @500 nit 7.5 8.7 6.6 V @ 5 mA 3.0 3.0
2.9 V @ 100 nit 3.0 3.0 3.2 Lum.sub.max 21500 26020 16390 T50 @500
239 354 100 nit (%) (ref.) .lamda.max 632 632 633
[0157] EQE.sub.max: maximum external quantum efficiency [0158]
EQE@500 nit: external quantum efficiency at 500 nit (candela per
square meter (cd/m.sup.2)) [0159] V @ 5 mA: voltage at 5
milliamperes (mA) [0160] V @ 100 nit: voltage at 100 nit [0161]
Lum.sub.max: maximum luminance [0162] T50 @500 nit: time taken for
luminance at a constant current of an initial 500 nit reference to
decrease down to 50% (a relative value to 100% (ref) of Comparative
Examples 1 and 2)
[0163] Referring to Table 2, the quantum dot devices of Examples 1
and 2 show improved efficiency and life-span compared with the
quantum dot device according to Comparative Example 1.
[0164] Likewise, referring to Table 3, the quantum dot devices of
Examples 3 and 4 show improved efficiency and life-span compared
with the quantum dot device according to Comparative Example 2.
[0165] While this disclosure has been described in connection with
what is presently considered to be practical example embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
* * * * *