CN116456741A

CN116456741A - Light-emitting device, manufacturing method thereof and display device

Info

Publication number: CN116456741A
Application number: CN202310318673.0A
Authority: CN
Inventors: 王卫杰
Original assignee: BOE Technology Group Co Ltd
Current assignee: BOE Technology Group Co Ltd
Priority date: 2023-03-28
Filing date: 2023-03-28
Publication date: 2023-07-18

Abstract

The disclosure provides a light emitting device, a manufacturing method thereof and a display device, and belongs to the technical field of display. The light-emitting device comprises a first electrode, a light-emitting functional layer and a second electrode which are arranged in a stacked manner, wherein the light-emitting functional layer comprises a hole transport layer and a quantum dot light-emitting layer, the hole transport layer is positioned between the first electrode and the quantum dot light-emitting layer, and the material of the hole transport layer comprises a first hole transport material and a second hole transport material; wherein the first hole transport material and the second hole transport material are different; the first hole transport material is a P-type covalent organic framework material. The present disclosure can improve charge transfer balance, enhancing device performance.

Description

Light-emitting device, manufacturing method thereof and display device

Technical Field

The disclosure relates to the technical field of display, in particular to a light emitting device, a manufacturing method thereof and a display device.

Background

The quantum dot light emitting diode (Quantum Dot Light Emitting Diodes, QLED) has advantages such as high emission color purity, adjustable emission wavelength, and solution processing characteristics, and has received great attention in recent years from the scientific research and industry. Currently, a QLED device generally adopts an organic hole transport layer and a crosslinkable small molecule hole transport material, and is matched with an inorganic electron transport layer zinc oxide (ZnO). However, the hole mobility of organic hole transport materials is generally lower than the electron mobility of ZnO, together with the lower valence band of the Quantum Dots (QDs) themselves, such that the hole injection barrier is significantly larger than the electron injection barrier, ultimately resulting in a QLED carrier injection imbalance.

The above information disclosed in the background section is only for enhancement of understanding of the background of the disclosure and therefore it may include information that does not form the prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

The disclosure provides a light emitting device, a manufacturing method thereof and a display device, so as to improve charge transmission balance and improve device performance.

In order to achieve the above purpose, the present disclosure adopts the following technical scheme:

according to a first aspect of the present disclosure, there is provided a light emitting device including a first electrode, a light emitting functional layer, and a second electrode, which are stacked, the light emitting functional layer including a hole transporting layer and a quantum dot light emitting layer, the hole transporting layer being located between the first electrode and the quantum dot light emitting layer, a material of the hole transporting layer including a first hole transporting material and a second hole transporting material;

wherein the first hole transport material and the second hole transport material are different;

the first hole transport material is a P-type covalent organic framework material.

In one exemplary embodiment of the present disclosure, the first hole transport material and the second hole transport material satisfy the following relationship:

-6.5eV≤HOMO _HTL1 ≤-5.0eV；

HOMO _HTL2 ≤-5.7eV；

Wherein HOMO is a kind of _HTL1 Represents the highest occupied molecular orbital level, HOMO, of the first hole transporting material _HTL2 Representing the highest occupied molecular orbital energy level of the second hole transport material.

In one exemplary embodiment of the present disclosure, the first hole transport material has a hole mobility of not less than 3cm ² V ^-1 s ^-1 。

In one exemplary embodiment of the present disclosure, the mass ratio of the first hole transport material and the second hole transport material is (0.1 to 10): 100.

in one exemplary embodiment of the present disclosure, the first hole transport material is composed of organic framework units including one or more of triphenylamine, triphenylene, triphenylbenzene, pyrene, porphyrin, phthalocyanine, tetrathiafulvalene, tetraphenylmethane, naphthalene, anthracene, benzothiophene, benzodithiophene.

In one exemplary embodiment of the present disclosure, the light emitting functional layer further includes a hole injection layer between the first electrode and the hole transport layer;

wherein the material of the hole injection layer, the first hole transport material, and the second hole transport material satisfy the following relationship:

HOMO _HTL2 ≤HOMO _HTL1 ≤HOMO _HIL ；

wherein HOMO is a kind of _HTL1 Representing the highest occupied molecular orbital energy level of the first hole transport material; HOMO (high-order optical disk) _HTL2 Representing the highest occupied molecular orbital energy level of the second hole transport material; HOMO (high-order optical disk) _HIL Representing the highest occupied molecular orbital energy level of the material of the hole injection layer.

In one exemplary embodiment of the present disclosure, the hole transport layer has a thickness of 20nm to 50nm.

In one exemplary embodiment of the present disclosure, the hole transport layer is formed of a mixed liquid including the first hole transport material and the second hole transport material.

In one exemplary embodiment of the present disclosure, the light emitting functional layer further includes an electron transport layer between the second electrode and the quantum dot light emitting layer;

the material of the electron transport layer includes an inorganic material.

In one exemplary embodiment of the present disclosure, the material of the electron transport layer includes zinc oxide.

According to a second aspect of the present disclosure, there is provided a method of manufacturing a light emitting device, comprising:

providing a base, wherein the base comprises a substrate base plate and a first electrode arranged on one side of the substrate base plate;

forming a light-emitting functional layer on one side of the first electrode far away from the substrate base plate, wherein the light-emitting functional layer comprises a hole transport layer and a quantum dot light-emitting layer, and the hole transport layer is positioned between the first electrode and the quantum dot light-emitting layer;

Wherein the method for forming the hole transport layer comprises the following steps:

mixing a first hole transport material and a second hole transport material to obtain a mixed solution, wherein the first hole transport material and the second hole transport material are different, and the first hole transport material is a P-type covalent organic framework material;

and coating the mixed solution to form the hole transport layer.

According to a third aspect of the present disclosure, there is provided a display apparatus comprising a light emitting device as described in the first aspect.

The light emitting device provided by the present disclosure, the hole transport layer comprises a first hole transport material and a second hole transport material, the first hole transport material is a P-type covalent organic framework material. The P-type covalent organic framework material can construct an effective hole transport channel and high hole mobility, so that the hole transport capacity of the device can be improved, the charge transport balance is improved, and the performance of the device is improved.

Drawings

The above and other features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

Fig. 1 is a schematic view of a light emitting device structure in an exemplary embodiment of the present disclosure.

The main element reference numerals in the drawings are explained as follows:

100-a first electrode; 310-a hole injection layer; 320-a hole transport layer; 330-a quantum dot light emitting layer; 340-an electron transport layer; 350-an electron blocking layer; 200-a second electrode; 300-light emitting functional layer.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments may be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure.

In the drawings, the thickness of regions and layers may be exaggerated for clarity. The same reference numerals in the drawings denote the same or similar structures, and thus detailed descriptions thereof will be omitted.

The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the disclosed aspects may be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the main technical ideas of the present disclosure.

When a structure is "on" another structure, it may mean that the structure is integrally formed with the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure through another structure.

The terms "a," "an," "the" are used to indicate the presence of one or more elements/components/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. in addition to the listed elements/components/etc. The terms "first" and "second" and the like are used merely as labels, and are not intended to limit the number of their objects.

QLED devices typically employ an organic hole transporting layer and a crosslinkable small molecule hole transporting material, in combination with an inorganic electron transporting layer zinc oxide (ZnO). However, the hole mobility of the organic hole transport material is generally lower than the electron mobility of ZnO, and the lower valence band of the Quantum Dot (QD) itself makes the hole injection barrier significantly larger than the electron injection barrier, which ultimately results in a QLED device with unbalanced carrier injection, which is particularly serious in blue-light QLED devices.

In the related art, carrier balance is promoted by sacrificing electron injection, such as doping ZnO or inserting an electron blocking layer, but this method is disadvantageous for improvement of device performance.

The present disclosure provides a light emitting device, including a first electrode 100, a light emitting functional layer 300, and a second electrode 200 that are stacked, where the light emitting functional layer includes a hole transporting layer 320 and a quantum dot light emitting layer 330, the hole transporting layer 320 is located between the first electrode 100 and the quantum dot light emitting layer 330, and a material of the hole transporting layer 320 includes a first hole transporting material and a second hole transporting material; wherein the first hole transport material and the second hole transport material are different; the first hole transport material is a P-type covalent organic framework material.

The light emitting device provided by the present disclosure, the hole transport layer 320 includes a first hole transport material and a second hole transport material, the first hole transport material being a P-type covalent organic framework material. The P-type covalent organic framework material can construct an effective hole transport channel and high hole mobility, so that the hole transport capacity of the device can be improved, the charge transport balance is improved, and the performance of the device is improved.

The components of the light emitting device of the present disclosure will be described in detail below with reference to the attached drawings and specific examples:

the light emitting device provided by the present disclosure includes a first electrode 100, a light emitting functional layer 300, and a second electrode 200 that are stacked.

The first electrode 100 may be an anode, which may include a conductor such as a metal, a conductive metal oxide, or a combination thereof having a high work function. The anode may comprise, for example, a metal that may be nickel, platinum, vanadium, chromium, copper, zinc, or gold, or alloys thereof; the conductive metal oxide can be zinc oxide, indium oxide, tin oxide, indium Tin Oxide (ITO), indium zinc oxide (IZ)O), or fluorine doped tin oxide; alternatively, the combination of metal and conductive metal oxide may be ZnO and Al, or SnO ₂ And Sb, but is not limited thereto.

The second electrode 200 may be a cathode, which may include a conductor such as a metal, a conductive metal oxide, and/or a conductive polymer having a lower work function than the anode. The cathode may include, for example, a metal that may be aluminum, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, silver, tin, lead, cesium, barium, or the like, or alloys thereof; multilayer structures such as LiF/Al, li ₂ O/Al, liq/Al, liF/Ca, and BaF ₂ /Ca, but is not limited thereto.

The light emitting functional layer 300 includes a hole transporting layer 320, a quantum dot light emitting layer 330, and an electron transporting layer 340, the hole transporting layer 320 being positioned between the first electrode 100 and the quantum dot light emitting layer 330, and the electron transporting layer 340 being positioned between the quantum dot light emitting layer 330 and the second electrode 200.

In some embodiments of the present disclosure, the material of the hole transport layer 320 includes a first hole transport material and a second hole transport material; wherein the first hole transport material and the second hole transport material are different; the first hole transport material is a P-type covalent organic framework material.

Covalent Organic Framework (COF) materials are porous crystalline materials formed by covalent bonding of organic framework units. For example, in a two-dimensional (2D) COF material, organic framework units can be orderly stacked to form a 2D sheet through pi-pi interaction among molecules, so that the charge transport performance in the direction is remarkably improved. An extended pi conjugated system can be formed by utilizing conjugated organic framework units with electron donating properties, the P-type properties of the COF material are endowed, and high hole mobility is realized.

The hole transport layer 320 is formed by doping the P-type covalent organic framework material into other hole transport materials, and the hole transport capacity of the light emitting device can be promoted by means of a hole transport channel constructed by the P-type covalent organic framework material and high hole mobility, so that charge transport balance is improved.

Further, the light emitting functional layer 300 may further include a hole injection layer 310 and an electron injection layer 350, the hole injection layer 310 being positioned between the first electrode 100 and the hole transport layer 320 to enhance the ability to inject holes into the hole transport layer 320. An electron injection layer 350 is positioned between the electron transport layer 340 and the second electrode 200 to enhance the ability to inject electrons into the electron transport layer 340.

In some embodiments of the present disclosure, the material of the hole injection layer 310, the first hole transport material, and the second hole transport material satisfy the following relationship:

HOMO _HTL2 ≤HOMO _HTL1 ≤HOMO _HIL ；

wherein HOMO is a kind of _HTL1 Representing the highest occupied molecular orbital energy level of the first hole transport material; HOMO (high-order optical disk) _HTL2 Representing the highest occupied molecular orbital energy level of the second hole transport material; HOMO (high-order optical disk) _HIL Representing the highest occupied molecular orbital energy level of the material of the hole injection layer 310.

In some embodiments of the present disclosure, the first hole transport material has a hole mobility of not less than 3cm ² V ^-1 s ^-1 . For example, the first hole transport material may have a hole mobility of not less than 3cm ² V ^-1 s ^-1 Or not less than 4cm ² V ^-1 s ^-1 Or not less than 4.5cm ² V ^-1 s ^-1 Or not less than 5cm ² V ^-1 s ^-1 Or not less than 5.5cm ² V ^-1 s ^-1 Or not less than 6cm ² V ^-1 s ^-1 Or not less than 6.5cm ² V ^-1 s ^-1 Or not less than 7cm ² V ^-1 s ^-1 Or not less than 7.5cm ² V ^-1 s ^-1 Or not less than 8cm ² V ^-1 s ^-1 Or not less than 8.5cm ² V ^-1 s ^-1 。

The first hole transport material may have a relatively deep HOMO level to match the HOMO level of the quantum dot light emitting layer 330. Accordingly, mobility of holes transferred from the hole transport layer 320 to the quantum dot light emitting layer 330 may be improved.

The HOMO level of the first hole transport material may be equal to the HOMO level of the quantum dot light emitting layer 330 or a range of about 1.0eV or less from the HOMO level of the quantum dot light emitting layer 330. For example, the difference between the HOMO levels of the first hole transport material and the quantum dot light emitting layer 330 may be about 0eV to about 1.0eV.

In some embodiments of the present disclosure, the first hole transport material and the second hole transport material satisfy the following relationship:

-6.5eV≤HOMO _HTL1 ≤-5.0eV；

HOMO _HTL2 ≤-5.7eV。

wherein the HOMO level of the first hole transporting material may be approximately-6.4 eV to-5.1 eV, or-6.3 eV to-5.2 eV, or-6.2 eV to-5.3 eV, or-6.1 eV to-5.4 eV, or-6.0 eV to-5.5 eV, or-5.9 eV to-5.6 eV, or-5.8 eV to-5.7 eV, and specifically may be-6.5 eV, -6.4eV, -6.3eV, -6.2eV, -6.1eV, -6.0eV, -5.9eV, -5.8, -5.7eV, -5.6eV, -5.5eV, -5.4eV, -5.3eV, -5.2eV, -5.1eV, -5.0eV, but is not limited thereto.

The HOMO level of the second hole-transporting material may be, but is not limited to, -6.4eV, -6.3eV, -6.2eV, -6.1eV, -6.0eV, -5.9eV, -5.8eV, -5.7eV, etc.

In some embodiments of the present disclosure, the first hole transport material is comprised of an organic framework unit comprising triphenylamineTriphenylene->Triphenylbenzene->Pyrene->Porphyrin->Phthalocyanine->TetrathiafulvaleneTetraphenyl methane->Naphthalene->Anthracene->Benzothiophene->Benzodithiophene->One or more of the following.

For example, the organic framework unit may include triphenylamine and naphthalene, or triphenylamine and anthracene, or triphenylamine and naphthalene, or pyrene and benzothiophene, or porphyrin and anthracene, or phthalocyanine and benzothiophene, or tetrathiafulvalene and naphthalene, or tetraphenyl methane and anthracene, but is not limited thereto.

For example, the organic frame unit comprises tetra-amino phenyl porphyrin and terephthalaldehyde, the first transport material is 2D covalent organic frame material COF-366 with crystalline structure constructed by condensation reaction of tetra-amino phenyl porphyrin and terephthalaldehyde, and the hole mobility of the organic frame material can reach 8.1cm ² V ^-1 s ^-1 For another example, the organic framework unit comprises phenyl porphyrin tetraborate and tetrahydroxyanthracene, the first transmission material is a 2D covalent organic framework material COF-66 synthesized by phenyl porphyrin tetraborate and tetrahydroxyanthracene, and the hole mobility of the organic framework material can reach 3cm ² V ^-1 s ^-1 As another example, the organic framework units include hexahydroxytriphenylene and hexaaminotrimethylene, and the first transport material is formed from hexahydroxytriphenylene and2D covalent organic framework material C2P-5 synthesized by hexaamino triphenylene and having hole mobility of 4cm ² V ^-1 s ^-1 。

The second hole transporting material may be selected from organic hole transporting materials or inorganic hole transporting materials, including but not limited to small molecule hole transporting materials and polymeric hole transporting materials, such as small molecule hole transporting materials, e.g., 4 '-bis (9-carbazole) biphenyl (CBP, HOMO: -6.0 eV), N-dicarbazolyl-3, 5-benzene (mCP, HOMO: -6.1 eV), polymeric hole transporting materials poly (9-vinylcarbazole) (PVK, HOMO: -5.8 eV), crosslinked hole transporting materials 4,4' -bis (3-vinyl-9-carbazole) biphenyl (CBP-V, HOMO: -6.2 eV), and the like. Inorganic hole transport materials include, but are not limited to, cuSCN, niO _x Etc.

In some embodiments of the present disclosure, the ratio of the mass of the first hole transport material to the mass of the second hole transport material is (0.1 to 10): 100. specifically, the mass ratio of the first hole transport material and the second hole transport material may be (0.1 to 9): 100, or (0.1 to 8): 100, or (0.1 to 7): 100, or (0.1 to 6): 100, or (0.1 to 5): 100, or (0.1 to 4): 100, or (0.1 to 3): 100, or (0.1 to 2): 100, or (0.1 to 1): 100.

The material of the hole injection layer 310 may also be selected with reference to the specific selection of the second hole transport material described above, if the requirement of the HOMO level is met, and may of course be selected from other hole injection materials commonly used in the art. Specifically, the material of hole injection layer 310 may be selected from poly (3, 4-ethylenedioxythiophene)/poly (4-styrenesulfonate) (PEDOT/PSS) with HOMO of-5.0 eV, niO _x The valence band of (2) is typically between-5.1 and-5.4 eV.

The hole transport layer 320 may have a thickness of 20nm to 50nm, specifically greater than about 20nm and less than or equal to about 50nm, greater than about 25nm and less than or equal to about 45nm, greater than about 30nm and less than or equal to about 40nm, greater than about 35nm and less than or equal to about 38nm.

Quantum Dots (QDs) are inorganic semiconductor nanoparticles synthesized by solution processes and having a size between 1 and 10nm that approximates or is smaller than the exciton bohr radius of the particle. The migration of carriers (electrons and holes) in the quantum dots is confined to the interior of the quantum dots, which gives the quantum dots unique optical and electrical properties.

The quantum dots may have, for example, a particle diameter (average maximum particle length for non-spherical shapes) of about 1nm to about 100nm, about 1nm to about 80nm, about 1nm to about 50nm, or about 1nm to 20 nm.

The energy band gap of the quantum dots can be controlled according to the size and composition of the quantum dots, and thus the emission wavelength can be controlled. For example, when the size of the quantum dot increases, the quantum dot may have a narrow energy bandgap and thus be formulated to emit light in a relatively long wavelength region, while when the size of the quantum dot decreases, the quantum dot may have a wide energy bandgap and thus be formulated to emit light in a relatively short wavelength region. For example, quantum dots may be formulated to emit light in a predetermined wavelength region of the visible light region according to their size and/or composition. For example, the quantum dots may be formulated to emit a second color light, a third color light, or a first color light, the second color light (blue light) may have a peak emission wavelength (λmax) in, for example, about 430nm to about 480nm, the third color light (red light) may have a peak emission wavelength (λmax) in, for example, about 600nm to about 650nm, and the first color light (green light) may have a peak emission wavelength (λmax) in, for example, about 520nm to about 560nm, but are not limited thereto.

The quantum dots can have, for example, a quantum yield of greater than or equal to about 10%, greater than or equal to about 20%, 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%.

Quantum dots may have a relatively narrow half width (FWHM). Here, the FWHM is a width corresponding to a half wavelength of the peak absorption point, and when the FWHM is narrow, light emitted in a narrow wavelength region can be formulated, and a high color purity can be obtained. The quantum dots can have a FWHM of, for example, less than or equal to about 50nm, less than or equal to about 49nm, less than or equal to about 48nm, less than or equal to about 47nm, less than or equal to about 46nm, less than or equal to about 45nm, less than or equal to about 44nm, less than or equal to about 43nm, less than or equal to about 42nm, less than or equal to about 41nm, less than or equal to about 40nm, less than or equal to about 39nm, less than or equal to about 38nm, less than or equal to about 37nm, less than or equal to about 36nm, less than or equal to about 35nm, less than or equal to about 34nm, less than or equal to about 33nm, less than or equal to about 32nm, less than or equal to about 31nm, less than or equal to about 30nm, less than or equal to about 29nm, or less than or equal to about 28 nm. Within the range, it may have a FWHM of, for example, about 2nm to about 49nm, about 2nm to about 48nm, about 2nm to about 47nm, about 2nm to about 46nm, about 2nm to about 45nm, about 2nm to about 44nm, about 2nm to about 43nm, about 2nm to about 42nm, about 2nm to about 41nm, about 2nm to about 40nm, about 2nm to about 39nm, about 2nm to about 38nm, about 2nm to about 37nm, about 2nm to about 36nm, about 2nm to about 35nm, about 2nm to about 34nm, about 2nm to about 33nm, about 2nm to about 32nm, about 2nm to about 31nm, about 2nm to about 30nm, about 2nm to about 29nm, or about 2nm to about 28 nm.

For example, the quantum dots may include group II-VI semiconductor compounds, group III-V semiconductor compounds, group IV-VI semiconductor compounds, group IV semiconductors, group I-III-VI semiconductor compounds, group I-II-IV-VI semiconductor compounds, group II-III-V semiconductor compounds, or combinations thereof. The group II-VI semiconductor compound may be selected, for example, from: binary compounds such as CdSe, cdTe, znS, znSe, znTe, znO, hgS, hgSe, hgTe, mgSe, mgS, or mixtures thereof; ternary compounds such as CdSeS, cdSeTe, cdSTe, znSeS, znSeTe, znSTe, hgSeS, hgSeTe, hgSTe, cdZnS, cdZnSe, cdZnTe, cdHgS, cdHgSe, cdHgTe, hgZnS, hgZnSe, hgZnTe, mgZnSe, mgZnS, or mixtures thereof; and quaternary compounds such as HgZnTeS, cdZnSeS, cdZnSeTe, cdZnSTe, cdHgSeS, cdHgSeTe, cdHgSTe, hgZnSeS, hgZnSeTe, hgZnSTe, or mixtures thereof, but are not limited thereto. The III-V semiconductor compound may be selected, for example, from: binary compounds such as GaN, gaP, gaAs, gaSb, alN, alP, alAs, alSb, inN, inP, inAs, inSb, or mixtures thereof; ternary compounds such as GaNP, gaNAs, gaNSb, gaPAs, gaPSb, alNP, alNAs, alNSb, alPAs, alPSb, inNP, inNAs, inNSb, inPAs, inPSb, or mixtures thereof; and quaternary compounds such as GaAlNP, gaAlNAs, gaAlNSb, gaAlPAs, gaAlPSb, gaInNP, gaInNAs, gaInNSb, gaInPAs, gaInPSb, inAlNP, inAlNAs, inAlNSb, inAlPAs, inAlPSb, or mixtures thereof, but are not limited thereto. The group IV-VI semiconductor compound may be selected, for example, from: binary compounds such as SnS, snSe, snTe, pbS, pbSe, pbTe, or mixtures thereof; ternary compounds such as SnSeS, snSeTe, snSTe, pbSeS, pbSeTe, pbSTe, snPbS, snPbSe, snPbTe, or mixtures thereof; and quaternary compounds such as SnPbSSe, snPbSeTe, snPbSTe, or mixtures thereof, but are not limited thereto. The group IV semiconductor may be selected, for example, from: elemental (unitary) semiconductors such as Si, ge, or mixtures thereof; and binary semiconductor compounds such as SiC, siGe, and mixtures thereof, but are not limited thereto. The group I-III-VI semiconductor compound may be, for example, cuInSe2, cuInS2, cuInGaSe, cuInGaS, or mixtures thereof, but is not limited thereto. The group I-II-IV-VI semiconductor compound may be, for example, cuZnSnSe, cuZnSnS, or a mixture thereof, but is not limited thereto. The group II-III-V semiconductor compound may include, for example, inZnP, but is not limited thereto.

The quantum dots may be of substantially uniform concentration or of locally different concentration profiles including elemental, binary, ternary, or quaternary semiconductor compounds.

For example, the quantum dots may include cadmium-free (Cd) quantum dots. Cadmium-free quantum dots are quantum dots that do not include cadmium (Cd). Cadmium (Cd) can cause serious environmental/health problems and is a limited element in accordance with the hazardous substances limitation directive (RoHS) in various countries, and thus non-cadmium-based quantum dots can be effectively used.

Quantum dots may have a core-shell structure in which one quantum dot surrounds another quantum dot. For example, the core and shell of the quantum dot may have an interface, and the element of at least one of the core or shell in the interface may have a concentration gradient, wherein the concentration of the element of the shell decreases toward the core. For example, the material composition of the shell of the quantum dot has a higher energy bandgap than the material composition of the core of the quantum dot, and thus the quantum dot may exhibit a quantum confinement effect.

The quantum dot may have a quantum dot core and a multi-layer quantum dot shell surrounding the core. Here, the multi-layer shell has at least two shells, wherein each shell may be of a single composition, an alloy, and/or have a concentration gradient.

For example, the shell of the multi-layer shell that is farther from the core may have a higher energy bandgap than the shell that is closer to the core, and thus the quantum dot may exhibit a quantum confinement effect.

For example, quantum dots having a core-shell structure may include, for example: a core comprising a first semiconductor compound comprising zinc (Zn), and at least one of tellurium (Te) and selenium (Se); and a shell comprising a second semiconductor compound disposed on at least a portion of the core and having a composition different from the composition of the core.

For example, the first semiconductor compound may be a Zn-Te-Se based semiconductor compound including zinc (Zn), tellurium (Te), and selenium (Se), e.g., a Zn-Se based semiconductor compound including a small amount of tellurium (Te), e.g., a semiconductor compound represented by ZnTexSe1-x, where x is greater than about 0 and less than or equal to 0.05.

For example, in the first semiconductor compound based on Zn-Te-Se, the molar amount of zinc (Zn) may be higher than that of selenium (Se), and the molar amount of selenium (Se) may be higher than that of tellurium (Te). For example, in the first semiconductor compound, the molar ratio of tellurium (Te) to selenium (Se) may be less than or equal to about 0.05, less than or equal to about 0.049, less than or equal to about 0.048, less than or equal to about 0.047, less than or equal to about 0.045, less than or equal to about 0.044, less than or equal to about 0.043, less than or equal to about 0.042, less than or equal to about 0.041, less than or equal to about 0.04, less than or equal to about 0.039, less than or equal to about 0.035, less than or equal to about 0.03, less than or equal to about 0.029, less than or equal to about 0.025, less than or equal to about 0.024, less than or equal to about 0.023, less than or equal to about 0.022, less than or equal to about 0.021, less than or equal to about 0.02, less than or equal to about 0.019, less than or equal to about 0.018, less than or equal to about 0.012, less than or equal to about 0.01. For example, in the first semiconductor compound, the molar ratio of tellurium (Te) to zinc (Zn) may be less than or equal to about 0.02, less than or equal to about 0.019, less than or equal to about 0.018, less than or equal to about 0.017, less than or equal to about 0.016, less than or equal to about 0.015, less than or equal to about 0.014, less than or equal to about 0.013, less than or equal to about 0.012, less than or equal to about 0.011, or less than or equal to about 0.010.

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, 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, 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 those described above.

For example, the second semiconductor compound may include zinc (Zn), selenium (Se), and/or sulfur (S). For example, the shell may include ZnSeS, znSe, znS, or a combination thereof. For example, the shell may include at least one inner shell disposed proximate to the core and an outermost shell disposed at an outermost side of the quantum dot. The inner shell may comprise ZnSeS, znSe, or a combination thereof, and the outermost shell may comprise ZnS. For example, the shell may have a concentration gradient of one component, and for example, the amount of sulfur (S) may increase as it leaves the core.

For example, a quantum dot having a core-shell structure may include: a core comprising a third semiconductor compound comprising indium (In) and at least one of zinc (Zn) and phosphorus (P); and a shell disposed on at least a portion of the core and comprising a fourth semiconductor compound having a different composition than the core.

In the third semiconductor compound based on In-Zn-P, the molar ratio of zinc (Zn) to indium (In) may be greater than or equal to about 25. For example, in the In-Zn-P based third semiconductor compound, the molar ratio of zinc (Zn) to indium (In) may be greater than or equal to about 28, greater than or equal to about 29, or greater than or equal to about 30. For example, in the In-Zn-P based third semiconductor compound, the molar ratio of zinc (Zn) to indium (In) may be less than or equal to about 55, such as less than or equal to about 50, less than or equal to about 45, less than or equal to about 40, less than or equal to about 35, less than or equal to about 34, less than or equal to about 33, or less than or equal to about 32.

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, 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, 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 those described above.

For example, the fourth semiconductor compound may include zinc (Zn) and sulfur (S) and optionally selenium (Se). For example, the shell may include ZnSeS, znSe, znS, or a combination thereof. For example, the shell may include at least one inner shell disposed proximate to the core and an outermost shell disposed at an outermost side of the quantum dot. At least one of the inner shell and the outermost shell may include a fourth semiconductor compound ZnS, znSe, or ZnSeS.

Preferably, the quantum dot light emitting layer 330 of the present disclosure may correspondingly emit blue light.

The average particle size of the quantum dots formulated to emit the second color light (blue light) may be, for example, less than or equal to about 4.5nm, and, for example, less than or equal to about 4.3nm, less than or equal to about 4.2nm, less than or equal to about 4.1nm, or less than or equal to about 4.0nm. Within the range, for example, the average particle size of the quantum dots may be from about 2.0nm to about 4.5nm, such as from about 2.0nm to about 4.3nm, from about 2.0nm to about 4.2nm, from about 2.0nm to about 4.1nm, or from about 2.0nm to about 4.0nm.

As an example, the blue light quantum dot may be a cadmium-based quantum dot, such as CdSe, cdS, cdZnSe, cdZnS, etc.; or cadmium-free quantum dots, such as InP, znSe, zeSeTe; or quantum dots with core-shell structures, such as CdSe/CdS, inP/ZnS, znSe/ZnS, znSeTe/ZnS, and the like. In the present disclosure, quantum dots with core-shell structures are preferred, and for quantum dots with core-shell structures, the size of the core, which affects the luminescence color, may be 1.5nm to 2.0nm when the core is CdSe, and blue light may be emitted in this range; when the core is InP, its size may be 1.5nm to 2.0nm, in which range blue light can be emitted.

The LUMO energy levels of the second electrode 200, the electron injection layer 350, the electron transport layer 340, and the quantum dot light emitting layer 330 may become gradually shallower. For example, the LUMO level of the electron injection layer 350 may be shallower than the work function of the second electrode 200, and the LUMO level of the electron transport layer 340 may be shallower than the LUMO level of the electron injection layer 350, and the LUMO level of the quantum dot light emitting layer 330 may be shallower than the LUMO level of the electron transport layer 340. That is, the work function of the second electrode 200, the LUMO level of the electron injection layer 350, the LUMO level of the electron transport layer 340, and the LUMO level of the quantum dot light emitting layer 330 may have stepped (cascade) levels gradually decreasing in one direction.

The electron transport layer 340 may include an inorganic material, such as first inorganic nanoparticles. The first inorganic nanoparticles may be, for example, oxide nanoparticles, and may be, for example, metal oxide nanoparticles.

The first inorganic nanoparticle may be a two-dimensional or three-dimensional nanoparticle having an average particle diameter as follows: less than or equal to about 10nm, in a range of less than or equal to about 8nm, less than or equal to about 7nm, less than or equal to about 5nm, less than or equal to about 4nm, or less than or equal to about 3.5nm, or in a range of about 1nm to about 10nm, about 1nm to about 9nm, about 1nm to about 8nm, about 1nm to about 7nm, about 1nm to about 5nm, about 1nm to about 4nm, or about 1nm to about 3.5nm.

For example, the first inorganic nanoparticle may be a metal oxide nanoparticle including at least one of: zinc (Zn), magnesium (Mg), cobalt (Co), nickel (Ni), gallium (Ga), aluminum (Al), calcium (Ca), zirconium (Zr), tungsten (W), lithium (Li), titanium (Ti), tantalum (Ta), tin (Sn), hafnium (Hf), and barium (Ba).

As an example, the first inorganic nanoparticle may include a metal oxide nanoparticle including zinc (Zn), and may include a metal oxide nanoparticle including zinc (Zn) and a metal oxide nanoparticle including zinc (Zn) _1-x Q _x O(0≤x<0.5 Metal oxide nanoparticles represented. Where Q is at least one metal other than Zn, such as magnesium (Mg), cobalt (Co), nickel (Ni), gallium (Ga), aluminum (Al), calcium (Ca), zirconium (Zr), tungsten (W), lithium (Li), titanium (Ti), tantalum (Ta), tin (Sn), hafnium (Hf), silicon (Si), barium (Ba), aluminum (Al), titanium (Ti), tantalum (Ta), tin (Sn), hafnium (Hf), silicon (Si), barium (Ba), titanium (Ca), titanium (Zn), titanium (Li), titanium (Ti), titanium (Ca), and the like,Or a combination thereof.

For example, Q may include magnesium (Mg).

For example, x may be 0.01.ltoreq.x.ltoreq.0.3 within the range, e.g., 0.01.ltoreq.x.ltoreq.0.2.

The LUMO level of electron transport layer 340 may be a value between the LUMO level of quantum dot light emitting layer 330 and the LUMO level of electron injection layer 350, and may be from about 3.2eV to about 4.8eV, from about 3.2eV to about 4.6eV, from about 3.2eV to about 4.5eV, from about 3.2eV to about 4.3eV, from about 3.2eV to about 4.1eV, from about 3.4eV to 4.1eV, from about 3.5eV to about 4.6eV, from about 3.6eV to about 4.3eV, from about 3.6eV to about 4.1eV, from about 3.6eV to about 3.9eV, from about 3.7eV to about 4.6eV, from about 3.7eV to about 4.3eV, from about 3.7eV to about 4.1eV, or from about 3.7eV to about 3.9eV. The LUMO level of the electron injection layer 350 may be between the work function of the second electrode 200 and the LUMO level of the electron transport layer 340.

The electron transport layer 340 can have a thickness of greater than about 10nm and less than or equal to about 80nm, and within a range of greater than about 10nm and less than or equal to about 70nm, greater than about 10nm and less than or equal to about 60nm, greater than about 10nm and less than or equal to about 50nm, greater than about 10nm and less than or equal to about 40nm, or greater than about 10nm and less than or equal to about 30nm.

The electron injection layer 350 may be thinner than the electron transport layer 340. For example, the thickness of the electron injection layer 350 may be about 0.01 to about 0.8 times, about 0.01 to about 0.7 times, about 0.01 to about 0.5 times, about 0.1 to about 0.8 times, about 0.1 to about 0.7 times, or about 0.1 to about 0.5 times the thickness of the electron transport layer 340. The thickness of the electron injection layer 350 may be, for example, less than or equal to about 10nm, less than or equal to about 7nm, or less than or equal to about 5nm. Within the range, the thickness of the electron injection layer 350 may be about 1nm to about 10nm, about 1nm to about 8nm, about 1nm to about 7nm, or about 1nm to about 5nm.

The present disclosure also provides a method for manufacturing a light emitting device, including:

step S100, providing a base, wherein the base comprises a substrate base plate and a first electrode 100 arranged on one side of the substrate base plate;

step S200, forming a light emitting functional layer 300 on a side of the first electrode 100 away from the substrate, wherein the light emitting functional layer 300 includes a hole transporting layer 320 and a quantum dot light emitting layer 330, and the hole transporting layer 320 is located between the first electrode 100 and the quantum dot light emitting layer 330;

Wherein, the method for forming the hole transport layer 320 includes:

step S210, mixing a first hole transport material and a second hole transport material to obtain a mixed solution, wherein the first hole transport material and the second hole transport material are different, and the first hole transport material is a P-type covalent organic framework material;

step S220, coating the mixed solution to form the hole transport layer 320.

Wherein the mixing concentration ratio of the first hole transport material to the second hole transport material is (0.1-10): 100.

the thin film formed solely due to the P-type covalent organic framework material has light absorption in the visible region. Therefore, in the present disclosure, the hole transport layer 320 is prepared by a blending method, the P-type covalent organic framework material is uniformly dispersed in the second hole transport material solution, and then the uniformly mixed solution is spin-coated to prepare a film, and then dried to prepare the hole transport layer 320, the rotation speed is 1000-3000 rpm, and the annealing temperature is 80-120 ℃.

The first hole transport material has a hole mobility of not less than 3cm ² V ^-1 s ^-1 . For example, the first hole transport material may have a hole mobility of not less than 3cm ² V ^-1 s ^-1 Or not less than 4cm ² V ^-1 s ^-1 Or not less than 4.5cm ² V ^-1 s ^-1 Or not less than 5cm ² V ^-1 s ^-1 Or not less than 5.5cm ² V ^-1 s ^-1 Or not less than 6cm ² V ^-1 s ^-1 Or not less than 6.5cm ² V ^-1 s ^-1 Or not less than 7cm ² V ^-1 s ^-1 Or not less than 7.5cm ² V ^-1 s ^-1 Or not less than 8cm ² V ^-1 s ^-1 Or not less than 8.5cm ² V ^-1 s ^-1 。

For example, the organic frame unit comprises tetra-amino phenyl porphyrin and terephthalaldehyde, the first transport material is 2D covalent organic frame material COF-366 with crystalline structure constructed by condensation reaction of tetra-amino phenyl porphyrin and terephthalaldehyde, and the hole mobility of the organic frame material can reach 8.1cm ² V ^-1 s ^-1 For another example, the organic framework unit comprises phenyl porphyrin tetraborate and tetrahydroxyanthracene, the first transmission material is a 2D covalent organic framework material COF-66 synthesized by phenyl porphyrin tetraborate and tetrahydroxyanthracene, and the hole mobility of the organic framework material can reach 3cm ² V ^-1 s ^-1 As another example, the organic framework units include hexahydroxytriphenylene and hexaaminotrimethylene, and the first transport material is a 2D covalent organic framework material C2P-5 synthesized from hexahydroxytriphenylene and hexaaminotrimethylene, having a hole mobility of 4cm ² V ^-1 s ^-1 。

The second hole transporting material may be selected from organic hole transporting materials including, but not limited to, small molecule hole transporting materials such as 4,4' -bis (9-carbazole) biphenyl (CBP, HOMO: -6.0 eV), N-dicarbazolyl-3, 5-benzene (mCP, HOMO: -6.1 eV), and polymeric hole transporting materials poly (9-vinylcarbazole) (PVK, HOMO: -5.8 eV), Crosslinked hole transport materials 4,4' -bis (3-vinyl-9-carbazole) biphenyl (CBP-V, HOMO: -6.2 eV), and the like. Inorganic hole transport materials include, but are not limited to, cuSCN, niO _x Etc.

The present disclosure also provides a display apparatus including the light emitting device in any of the above embodiments. The display device can be electronic equipment such as a computer, a mobile phone, a tablet and the like.

Examples

As shown in fig. 1, a light emitting device is fabricated and formed, and the light emitting device includes an ITO glass substrate (anode), a hole injection layer 310, a hole transport layer 320, a quantum dot light emitting layer 330, an electron transport layer 340, and a cathode in this order from bottom to top. In an embodiment, the hole transport layer 320 is prepared from a hole transport material doped with a P-type covalent organic framework material. The preparation steps of the device are as follows:

ultrasonically cleaning an ITO glass substrate by deionized water, acetone and isopropanol for 15 minutes, and then baking at 130 ℃ for 10 minutes;

2. placing the dried ITO glass substrate in an ultraviolet ozone cleaning machine for irradiation for 20 minutes;

3. hole injection layer 310 was prepared: spin-coating PEDOT on the ITO substrate, wherein the spin-coating rotation speed is 4000rpm, the time is 40s, and the substrate is baked for 30 minutes at 130 ℃ in air;

4. hole transport layer 320 was prepared: firstly, adding a P-type covalent organic framework material COF-366 into a chlorobenzene solution (12 mg/mL) of TFB according to the mass fraction of 0.5%, and fully stirring to uniformly disperse the P-type covalent organic framework material in the TFB solution; then spin-coating TFB solution added with the P-type covalent organic framework material in nitrogen atmosphere, spin-coating at 3000rpm for 40s, and baking at 150 ℃ for 30 minutes in nitrogen atmosphere;

5. Preparing a quantum dot light emitting layer 330: spin-coating CdSe/ZnS quantum dot octane solution in nitrogen atmosphere, wherein the spin-coating rotating speed is 3000rpm, the time is 40s, and baking is carried out for 10 minutes at 100 ℃ in nitrogen atmosphere;

6. electron transport layer 340 was prepared: spin-coating ZnO nanoparticle solution in nitrogen atmosphere, wherein the spin-coating rotating speed is 3000rpm, the time is 40s, and the ZnO nanoparticle solution is baked for 10 minutes at 80 ℃ in nitrogen atmosphere;

7. preparing a metal cathode: spin coating of the solutionThen transferring the sample into a vacuum evaporation cabin until the vacuum degree is reduced to 2X 10 ^-4 Pa, starting to vapor deposit Al electrode, vapor deposition rate isThe thickness is 100nm, and the device preparation is completed.

The structure of each material used in the examples is as follows:

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COF-366 (CAS number 1381930-10-4)

Comparative example

The materials and preparation conditions for each layer were the same as in the examples except that hole transport layer 320 was spin coated with a solution of pure TFB in chlorobenzene (12 mg/mL).

The results show that the devices produced in the examples perform better than the comparative examples.

It should be noted that although the steps of the methods of the present disclosure are illustrated in the accompanying drawings in a particular order, this does not require or imply that the steps must be performed in that particular order or that all of the illustrated steps be performed in order to achieve desirable results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step to perform, and/or one step decomposed into multiple steps to perform, etc., all are considered part of the present disclosure.

It is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the disclosure. The disclosure is capable of other embodiments and of being practiced and carried out in various ways. The foregoing variations and modifications are within the scope of the present disclosure. It should be understood that the present disclosure disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present disclosure. Embodiments of the present disclosure describe the best mode known for carrying out the disclosure and will enable one skilled in the art to utilize the disclosure.

Claims

1. A light emitting device, comprising a first electrode, a light emitting functional layer and a second electrode which are stacked, wherein the light emitting functional layer comprises a hole transport layer and a quantum dot light emitting layer, the hole transport layer is positioned between the first electrode and the quantum dot light emitting layer, and the material of the hole transport layer comprises a first hole transport material and a second hole transport material;

2. The light-emitting device according to claim 1, wherein the first hole-transporting material and the second hole-transporting material satisfy the following relationship:

-6.5eV≤HOMO _HTL1 ≤-5.0eV；

HOMO _HTL2 ≤-5.7eV；

3. The light-emitting device according to claim 1, wherein the first hole transport material has a hole mobility of not less than 3cm ² V ^-1 s ^-1 。

4. The light-emitting device according to claim 1, wherein a mass ratio of the first hole transport material and the second hole transport material is (0.1 to 10): 100.

5. the light-emitting device according to claim 1, wherein the first hole-transporting material is composed of an organic framework unit including one or more of triphenylamine, triphenylene, triphenylbenzene, pyrene, porphyrin, phthalocyanine, tetrathiafulvalene, tetraphenylmethane, naphthalene, anthracene, benzothiophene, and benzodithiophene.

6. The light-emitting device according to claim 1, wherein the light-emitting functional layer further comprises a hole injection layer, the hole injection layer being located between the first electrode and the hole transport layer;

HOMO _HTL2 ≤HOMO _HTL1 ≤HOMO _HIL ；

7. The light-emitting device according to claim 1, wherein the thickness of the hole transport layer is 20nm to 50nm.

8. The light-emitting device according to claim 1, wherein the hole-transporting layer is formed from a mixed liquid including the first hole-transporting material and the second hole-transporting material.

9. The light-emitting device according to claim 8, wherein the light-emitting functional layer further comprises an electron transport layer between the second electrode and the quantum dot light-emitting layer;

the material of the electron transport layer includes an inorganic material.

10. The light-emitting device according to claim 9, wherein the material of the electron transport layer comprises zinc oxide.

11. A method of fabricating a light emitting device, comprising:

and coating the mixed solution to form the hole transport layer.

12. A display device comprising a light emitting device according to any one of claims 1 to 10.