CN113224244B - Light-emitting device, preparation method thereof and display device - Google Patents

Light-emitting device, preparation method thereof and display device Download PDF

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CN113224244B
CN113224244B CN202010277150.2A CN202010277150A CN113224244B CN 113224244 B CN113224244 B CN 113224244B CN 202010277150 A CN202010277150 A CN 202010277150A CN 113224244 B CN113224244 B CN 113224244B
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light
emitting
sublayer
layer
emitting device
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CN113224244A (en
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苏亮
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Guangdong Juhua Printing Display Technology Co Ltd
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Guangdong Juhua Printing Display Technology Co Ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/10—Deposition of organic active material
    • H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating

Abstract

The invention discloses a light-emitting device, a preparation method thereof and a display device. The light emitting device includes: an anode and a cathode arranged oppositely; a quantum dot light emitting layer disposed between the anode and the cathode, the quantum dot light emitting layer comprising: a first luminescent sublayer disposed toward the anode, the first luminescent sublayer formed by mixing a TADF material and quantum dots; a second light-emitting sublayer disposed toward the cathode, the second light-emitting sublayer formed from a mixture of an electron acceptor material and a TADF material. The quantum dot light-emitting device can effectively improve the light-emitting efficiency and stability of the light-emitting device based on energy transfer.

Description

Light-emitting device, preparation method thereof and display device
Technical Field
The invention relates to the field of display, in particular to a light-emitting device, a preparation method thereof and a display device.
Background
Due to the unique optical properties of quantum dots, such as continuously adjustable light-emitting wavelength along with size and components, narrow light-emitting spectrum, high fluorescence efficiency, good stability and the like, quantum dot electroluminescent diodes (QLEDs) are widely concerned and researched in the display field. Meanwhile, the QLED display has many advantages that the LCD cannot achieve, such as large viewing angle, high contrast, fast response speed, and flexibility, and is thus expected to become a next generation display technology.
Through decades of development, the QLED structurally forms a classical configuration of organic hole transport layer/quantum dot light emitting layer/inorganic electron transport layer. Under the structure, the efficiency of the QLED is directly related to an organic electroluminescent diode (OLED), and the QLED shows a great prospect. However, challenges also follow. On one hand, a relatively obvious hole barrier exists between the organic hole transport layer and the quantum dot light-emitting layer, and an electron barrier between the inorganic electron transport layer and the quantum dot light-emitting layer is much smaller; on the other hand, the hole mobility of organic hole transport materials is much smaller than the electron mobility of inorganic electron transport materials; under the combined action of the two, the QLED has the serious problem of excessive electrons, and the fluorescence quenching of the quantum dot light emitting layer, the increase of Auger recombination probability, the failure of the organic hole transport layer and the like are caused. In the face of the problem, the quantum dot light emission obtained by using the energy transfer technology is probably an effective method, and the problem of quantum dot electron excess can be avoided.
The rapid development of monomolecular thermally activated delayed fluorescence materials (TADF) which can rapidly convert triplet excitons into singlet excitons may be a very suitable quantum dot host material. However, the conventional technology of combining the TADF material with the quantum dot to obtain the quantum dot luminescence generally has the problems that the efficiency and the stability are still to be improved.
Disclosure of Invention
Accordingly, there is a need for a light emitting device, a method of manufacturing the same, and a display device, which can effectively improve the light emitting efficiency and stability of the light emitting device.
A light emitting device comprising:
an anode and a cathode arranged oppositely;
a quantum dot light emitting layer disposed between the anode and the cathode, the quantum dot light emitting layer comprising:
a first luminescent sublayer disposed toward the anode, the first luminescent sublayer formed by mixing a TADF material and quantum dots;
a second light-emitting sublayer disposed toward the cathode, the second light-emitting sublayer formed from a mixture of an electron acceptor material and a TADF material.
In one embodiment, the HOMO level of the electron acceptor material in the second light emitting sublayer is greater than the HOMO level of the TADF material in the first light emitting sublayer;
the LUMO level of the electron acceptor material in the second light-emitting sublayer is greater than the LUMO level of the TADF material in the first light-emitting sublayer.
In one embodiment, the HOMO level of the electron acceptor material in the second emissive sub-layer is at least 0.4eV greater than the HOMO level of the TADF material in the first emissive sub-layer;
the LUMO level of the electron acceptor material in the second light-emitting sublayer is at least 0.4eV greater than the LUMO level of the TADF material in the first light-emitting sublayer.
In one embodiment, the TADF material is selected from: one or more of t4CzIPN, 4CzFCN, 3ACR-TRZ, 4CzCNPy, TBP-DMAc, tri-PXZ-TRZ, tmCzTrz, DMAC-DPS, CNICCz, CNICtCz, 5CzCN, TP-C-TPB and PXZ-DPS.
In one embodiment, the electron acceptor material is selected from: one or more of DPEPO, TPBi, tmPyPb, BCP, bphen, tmPyTz, B3PYMPM, 3TPYMB and PO-T2T.
In one embodiment, the molar ratio of the quantum dots to the TADF material in the first luminescent sublayer is 1: (1.5 to 99); and/or
The molar ratio of the TADF material to the electron acceptor material in the second light-emitting sublayer is 1: (0.4-99).
In one embodiment, the thickness of the first luminescent sublayer is 10-30 nm; and/or
The thickness of the second light-emitting sublayer is 3-15 nm.
In one embodiment, the light emitting device further comprises:
a hole functional layer disposed between the anode and the quantum dot light emitting layer; and/or the presence of a gas in the gas,
and the electronic functional layer is arranged between the cathode and the quantum dot light-emitting layer.
In one embodiment, the hole function layer includes:
a hole injection layer disposed toward the anode, the hole injection layer being of a material selected from the group consisting of: PEDOT is one or more of PSS, WO3, moO3, V2O5, F4-TCNQ and HATCN; and/or
A hole transport layer disposed toward the first emissive sub-layer, the hole transport layer being of a material selected from: one or more of Poly-TPD, TFB, PVK, NPB, TAPC, TCTA, mCP, CBP, mCBP, CDBP, niO, cu2O and CuSCN.
In one embodiment, the electronically functional layer comprises:
an electron injection layer disposed toward the cathode, the electron injection layer being of a material selected from the group consisting of: one or more of LiF, csF, liq, cs2CO3, li2CO3, ba and Yb; and/or
An electron transport layer disposed toward the second emissive sublayer, the electron transport layer being of a material selected from: one or more of ZnO, znAlO, znMgO, znGaO, tiO2, snO2, TPBi, tmPyPb, BCP, bphen, tmPyTz, B3PYMPM, 3TPYMB and PO-T2T.
A method for manufacturing a light emitting device includes the steps of:
sequentially laminating an anode, a first light-emitting sublayer, a second light-emitting sublayer and a cathode on a substrate; or
Sequentially laminating a cathode, a second light-emitting sublayer, a first light-emitting sublayer and an anode on a substrate;
wherein the first luminescent sublayer is formed by mixing TADF materials and quantum dots;
the second light-emitting sublayer is formed by mixing an electron acceptor material and a TADF material.
A display device, comprising:
the light emitting device described above; or
The light-emitting device obtained by the preparation method is provided.
The luminescent device can effectively solve the problems that the luminescent efficiency of the luminescent device is not high enough and the efficiency roll-off is serious because quantum dots are directly doped in an electron donor material or an electron acceptor material in the prior art. In the quantum dot light-emitting device, the electron acceptor material in the second luminescent sublayer and the TADF material in the first luminescent sublayer can form an interface type exciplex, so that excitons can be transferred to quantum dots, and the luminous efficiency of the light-emitting device can be improved; the TADF material in the second light-emitting sublayer can receive a part of the holes moving from the anode direction, and form excitons with the electrons, which helps to enlarge the exciton distribution area and thus reduce the efficiency roll-off, and meanwhile, the excitons in the TADF can transfer energy to the quantum dots, which helps to further improve the efficiency of the quantum dot light-emitting device.
Drawings
Fig. 1 is a schematic cross-sectional view of a light emitting device according to an embodiment of the invention.
Description of the reference numerals
101. A substrate; 102. an anode; 103. a hole injection layer; 104. a hole transport layer; 105. a quantum dot light emitting layer; 1051. a first luminescent sublayer; 1052. a second light-emitting sublayer; 106. an electron transport layer; 107. an electron injection layer; 108. and a cathode.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It should be understood that the terms "first", "second", etc. are used herein to describe various information, but the information should not be limited to these terms, which are used only to distinguish one type of information from another. For example, "first" information may also be referred to as "second" information, and similarly, "second" information may also be referred to as "first" information, without departing from the scope of the present invention.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, e.g., as being fixed or detachable or integrally connected; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening elements, or they may be in communication within two elements, i.e., when an element is referred to as being "disposed" on another element, it may be directly on the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
An embodiment of the present invention provides a light emitting device. The light emitting device includes:
an anode and a cathode arranged oppositely;
and the quantum dot light-emitting layer is arranged between the anode and the cathode. The quantum dot light emitting layer includes: a first light emitting sublayer and a second light emitting sublayer. The first luminescent sublayer is arranged towards the anode and is formed by mixing TADF materials and quantum dots; the second light emitting sublayer is disposed toward the cathode, and is formed by mixing an electron acceptor material and a TADF material.
The luminescent device can effectively solve the problems that the luminescent efficiency of the luminescent device is not high enough and the efficiency roll-off is serious because quantum dots are directly doped in an electron donor material or an electron acceptor material in the prior art. In the quantum dot light-emitting device, the electron acceptor material in the second luminescent sublayer and the TADF material in the first luminescent sublayer can form an interface type exciplex, so that excitons can be transferred to quantum dots, and the luminous efficiency of the light-emitting device can be improved; the TADF material in the second light-emitting sublayer can receive a part of the holes moving from the anode direction to form excitons with the electrons, which helps to enlarge an exciton distribution area and further reduce efficiency roll-off, and meanwhile, the excitons in the TADF can transfer energy to the quantum dots, which helps to further improve the efficiency of the quantum dot light-emitting device.
The HOMO level of the electron acceptor material in the second light-emitting sublayer is greater than the HOMO level of the TADF material in the first light-emitting sublayer. The LUMO energy level of the electron acceptor material in the second emissive sub-layer is greater than the LUMO energy level of the TADF material in the first emissive sub-layer.
The HOMO level of the electron acceptor material in the second light-emitting sublayer is at least 0.4eV greater than the HOMO level of the TADF material in the first light-emitting sublayer. The LUMO level of the electron acceptor material in the second emissive sublayer is at least 0.4eV greater than the LUMO level of the TADF material in the first emissive sublayer.
The TADF material is selected from: t4CzIPN (2,4,5,6-tetra (3,6-di-tert-butyrlcarbazol-9-yl) -1,3-dicyclonobene), 4CzFCN (2,3,4,6-tetra (9 Hcarbazol-9-yl) -5-fluorobenozonitril), 3ACR-TRZ (2,4,6-tris (4- (9,9-dimethylacidan-10-yl) phenyl) -1,3,5-triazine) 4CzCNPy (2,3,5,6-tetracarbazole-4-cyanoo-pyridine), TBP-DMAc (benzene-1,3,5-tris ((4- (9,9-dimethylacridin-10 (9H) -yl) phenyl) methanone), tri-PXZ-TRZ (2,4,6-Tri (4- (10H-phenoxazin-10H-yl) phenyl) -1,3,5-triazine), tmCzTrz (9,9 ', 9' - (5- (9,9-diphenyl-9,9-triazin-2-yl) bezene-9,9-triyl) tris (9,9-dimethyl-9H-carbozole)), DMAC-DPS (Bis [4- (9,9-dimethyl-9,9-dihydroacridine) phenyl ] sulfone) ' CNICCz (6258 zft 6258-di (9H-carbozol-9-yl) indolo [ 6258 zft 6258-jk ] carbozole-2-carbonitrile), CNICtCz (6258 zft 6258-Bis (6258 zft 6258-di-tert-butyl-9H-carbozol-9-yl) indoo [ 6258 zft 6258-jk ] carbozole-2-carbonitrile), 5CzCN (6258 zft 6258-penta (9H-carbozol-9-yl) carbonitrile), TP-C-TPB (6- (3 ',5' -diphenylenyl) -12- (3 \ 5\ diphenylylphenyl-4 "-yl) chrysene), PXZ-DPS (10,10 ' - (sulforylbis (4,1-phenylene)) bis (10H-phenoxyazine)).
The electron acceptor material is selected from: one or more of DPEPO, TPBi, tmPyPb, BCP, bphen, tmPyTz, B3PYMPM, 3TPYMB and PO-T2T.
The molar ratio of the quantum dots in the first luminescent sublayer to the TADF material is 1: (1.5-99), and in another embodiment, the molar ratio of quantum dots to TADF material in the first luminescent sublayer is 1: (3-60), in another embodiment, the molar ratio of quantum dots to TADF material in the first luminescent sublayer is 1: (5-30). Preferably, the molar ratio of quantum dots to TADF material in the first luminescent sublayer is 1: (5 to 19).
The thickness of the first luminescent sublayer is 10-30 nm. For example, the thickness of the first luminescent sublayer is 10nm, 11nm, 12nm.. 29nm, 30nm, or other non-integer value.
The molar ratio of the TADF material to the electron acceptor material in the second light-emitting sublayer is 1: (0.4-99). In another embodiment, the molar ratio of TADF material to electron acceptor material in the second emissive sub-layer is 1: (1-80). In another embodiment, the molar ratio of TADF material to electron acceptor material in the second emissive sub-layer is 1: (5 to 50). In another embodiment, the molar ratio of TADF material to electron acceptor material in the second emissive sub-layer is 1: (10 to 30).
The thickness of the second light-emitting sublayer is 3-15 nm. For example, the thickness of the second luminescent sublayer is 3nm, 4nm, 5nm, 6nm.. 14nm, 15nm, or other non-integer value.
The light emitting device further includes: and the hole functional layer is arranged between the anode and the quantum dot light-emitting layer. Further, the first luminescent sublayer is disposed toward the hole function layer.
The hole function layer includes: a hole injection layer and/or a hole transport layer. A hole injection layer is disposed toward the anode, the hole injection layer being of PEDOT: PSS (poly (3,4-ethylenedioxythiophene): poly (styrenesulfonic acid)), WO 3 、MoO 3 、V 2 O 5 、F 4 TCNQ and HATCN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene), cuPc, woO x 、MoO x (e.g., X = 3), crO x 、NiO、CuO、VO x 、CuS、MoS 2 、MoSe 2 、WS 2 、WSe 2 One or more of them.
A hole transport layer is disposed toward the first emissive sub-layer, the hole transport layer being of a material selected from: poly-TPD (N, N ' -bis (3-methylphenyl) -N, N ' -diphenyl-1,1 ' -biphenyl-4,4 ' -diamine), TFB (Poly [ (9,9-di-N-octylfluorenyl-2,7-diyl) -alt- (4,4 ' - (N- (4-N-butyl) phenyl) -diphenylamine)]) PVK (polyvinylcarbazole), NPB (N, N ' -diphenyl-N, N ' - (1-naphthyl) -1,1' -biphenyl-4,4 ' -diamine), TAPC (4,4 ' -cyclohexylbis [ N, N-di (4-methylphenyl) aniline)]) TCTA (4,4 ', 4' -tris (carbazol-9-yl) triphenylamine), mCP, CBP (4,4 ' -bis (9-carbazol) biphenyl), PFB [ N, N ' - (4-N-butylphenyl) -N, N ' -diphenyl-p-phenylenediamine]- [9,9-di-n-octylfluorenyl-2,7-diyl]Copolymer, TPD (N, N '-bis (3-methylphenyl) -N, N' -diphenyl-1,1 '-biphenyl-4,4' -diamine), poly-TBP, mCBP, CDBP, niO, cu 2 O、CuSCN、MoO 3 、WoO 3 、NiO、CuO、V 2 O 5 And one or more of CuS.
The light emitting device further includes: and the electronic functional layer is arranged between the cathode and the quantum dot light-emitting layer. Further, the second light-emitting sublayer is disposed toward the electron-functional layer.
The electron function layer comprises an electron transmission layer arranged between the cathode and the quantum dot light-emitting layer, and an electron injection layer arranged between the cathode and the electron transmission layer, and the second light-emitting sublayer is arranged close to the electron transmission layer.
The material of the electron transport layer is selected from: znO, znAlO, znMgO, znGaO, tiO 2 、SnO 2 TPBi, tmPyPb, BCP, bphen, tmPyTz, B3PYMPM, 3TPYMB and PO-T2T.
The material of the electron injection layer is selected from: liF, csF, liq, cs 2 CO 3 、Li 2 CO 3 One or more of Ba and Yb.
In another aspect of the present invention, the present embodiment provides a method of manufacturing a light emitting device. The method comprises the following steps:
sequentially forming an anode, a first luminescent sublayer, a second luminescent sublayer and a cathode on a substrate; or
Sequentially forming a cathode, a second light-emitting sublayer, a first light-emitting sublayer and an anode on a substrate;
wherein the first luminescent sublayer is formed by mixing TADF materials and quantum dots;
the second light-emitting sublayer is formed by mixing an electron acceptor material and a TADF material.
According to an embodiment of the present invention, the first luminescent sublayer is formed by deposition using a solution method.
According to the embodiment of the invention, the light-emitting second light-emitting sub-layer is formed by co-evaporation deposition through an evaporation method.
The method for manufacturing the light emitting device in this embodiment prepares the first light emitting sub-layer formed by mixing the TADF material and the quantum dot on the hole function layer, and prepares the second light emitting sub-layer formed by mixing the electron acceptor material and the TADF material on the first light emitting sub-layer, where the electron acceptor material in the second light emitting sub-layer and the TADF material in the first light emitting sub-layer can form an interface type exciplex, and can transfer excitons to the quantum dot, which is helpful for improving the efficiency of the light emitting device; the TADF material in the second light-emitting sublayer can receive a part of the holes moving from the anode direction to form excitons with the electrons, which helps to enlarge an exciton distribution area and further reduce efficiency roll-off, and meanwhile, the excitons in the TADF material can transfer energy to the quantum dots, which helps to further improve the efficiency of the quantum dot light-emitting device.
According to an embodiment of the present invention, the method for manufacturing a light emitting device further includes a step of forming a hole function layer after forming the anode and before forming the first light emitting sub-layer, or forming a hole function layer after forming the first light emitting layer and before forming the anode, and the manufactured light emitting device sequentially includes the anode, the hole function layer, the first light emitting sub-layer, the second light emitting sub-layer, and the cathode stacked on the substrate;
the method for manufacturing the light emitting device may further include the step of forming an electronic function layer after the second light emitting sub-layer is formed and before the cathode is formed, or forming an electronic function layer after the cathode is formed and before the second light emitting sub-layer is formed, and the manufactured light emitting device sequentially includes an anode, a hole function layer, a first light emitting sub-layer, a second light emitting sub-layer, an electronic function layer, and a cathode which are stacked on a substrate.
In still another aspect of the present invention, the present invention provides a display device including: the light emitting device described above; alternatively, a light-emitting device obtained by the aforementioned production method. Thus, the display device may have all the features and advantages of the light emitting device or the manufacturing method described above, and thus, the description thereof is omitted.
Example 1
The embodiment provides a method for manufacturing a light emitting device.
Referring to fig. 1, a method for manufacturing a light emitting device includes the steps of:
(1) An anode 102 is made of a transparent conductive thin film ITO on a substrate 101, and the thickness of the anode 102 is 50nm.
(2) PSS as a hole injection layer 103, the thickness of the hole injection layer 103 being 30nm.
(3) TFB was deposited as a hole transport layer 104 on the hole injection layer 103 using a solution method, and the thickness of the hole transport layer 104 was 30nm.
(4) A solution method is used to deposit, as the first light-emitting sublayer 1051, TBP-DMAc, cdSe/CdSeS/CdS (molar ratio 9:1), wherein the thickness of the first light-emitting sublayer 1051 is 20nm, on the hole transport layer 104.
(5) TBP-DMAc: TPBi (molar ratio of 10: 90) was co-vapor deposited on the first light-emitting sublayer 1051 as the second light-emitting sublayer 1052 by an evaporation method, and the thickness of the second light-emitting sublayer 1052 was 5nm. First light emitting sublayer 1051 and second light emitting sublayer 1052 form quantum dot light emitting layer 105.
(6) TPBi is deposited as the electron transport layer 106 on the second light emitting sublayer 1052 by an evaporation method, and the thickness of the electron transport layer 106 is 45nm.
(7) Deposition of Cs on the Electron transport layer 106 by vapor deposition 2 CO 3 As the electron injection layer 107, the thickness of the electron injection layer 107 was 2nm.
(8) Al is deposited as a cathode 108 on the electron injection layer 107 by an evaporation method, and the thickness of the cathode 108 is 120nm.
In this embodiment, the second light-emitting sublayer 1052 is disposed between the first light-emitting sublayer 1051 and the electron transport layer 106, so that on one hand, the exciton distribution area is enlarged, and the problem of roll-off in efficiency is alleviated; on the other hand, the TADF material of the second light-emitting sublayer 1052 can also transfer the exciton energy to the quantum dot, so that the energy transmission channel is increased, and the light-emitting efficiency of the quantum dot light-emitting device is improved.
Example 2
The embodiment provides a method for manufacturing a light emitting device.
Referring to fig. 1, a method for manufacturing a light emitting device includes the steps of:
(1) An anode 102 is made of a transparent conductive thin film ITO on a substrate 101, and the thickness of the anode 102 is 50nm.
(2) PSS as a hole injection layer 103, the hole injection layer 103 having a thickness of 30nm was deposited on the anode 102 using a solution method.
(3) TFB was deposited as a hole transport layer 104 on the hole injection layer 103 using a solution method, and the thickness of the hole transport layer 104 was 30nm.
(4) A solution method is used for depositing TBP-DMAc, namely CdSe/CdSeS/CdS (the molar ratio is 9:1) as a first light-emitting sublayer 1051 on the hole transport layer 104, and the thickness of the first light-emitting sublayer 1051 is 20nm.
(5) TBP-DMAc: TPBi (molar ratio of 10: 90) is co-vapor deposited on the first light-emitting sublayer 1051 as the second light-emitting sublayer 1052 by an evaporation method, and the thickness of the second light-emitting sublayer 1052 is 10nm. First light-emitting sublayer 1051 and second light-emitting sublayer 1052 form quantum dot light-emitting layer 105.
(6) TPBi is deposited as the electron transport layer 106 on the second light-emitting sublayer 1052 by evaporation, and the thickness of the electron transport layer 106 is 40nm.
(7) Deposition of Cs on the electron transport layer 106 by evaporation 2 CO 3 As the electron injection layer 107, the thickness of the electron injection layer 107 was 2nm.
(8) Al is deposited as a cathode 108 on the electron injection layer 107 by an evaporation method, and the thickness of the cathode 108 is 120nm.
Example 3
The embodiment provides a method for manufacturing a light emitting device.
Referring to fig. 1, a method for manufacturing a light emitting device includes the steps of:
(1) A transparent conductive film ITO is used as an anode 102, and the thickness of the anode 102 is 50nm.
(2) PSS as a hole injection layer 103, the hole injection layer 103 having a thickness of 30nm was deposited on the anode 102 using a solution method.
(3) TFB was deposited as a hole transport layer 104 on the hole injection layer 103 using a solution method, and the thickness of the hole transport layer 104 was 30nm.
(4) A solution method is used to deposit, as the first light-emitting sublayer 1051, TBP-DMAc, cdSe/CdSeS/CdS (molar ratio 9:1), wherein the thickness of the first light-emitting sublayer 1051 is 20nm, on the hole transport layer 104.
(5) TBP-DMAc: TPBi (molar ratio of 10: 90) was co-vapor deposited on the first light-emitting sublayer 1051 as the second light-emitting sublayer 1052 by an evaporation method, and the thickness of the second light-emitting sublayer 1052 was 15nm. First light emitting sublayer 1051 and second light emitting sublayer 1052 form quantum dot light emitting layer 105.
(6) TPBi is deposited as the electron transport layer 106 on the second light emitting sublayer 1052 by an evaporation method, and the thickness of the electron transport layer 106 is 35nm.
(7) Deposition of Cs on the electron transport layer 106 by evaporation 2 CO 3 As the electron injection layer 107, the thickness of the electron injection layer 107 was 2nm.
(8) Al is deposited as a cathode 108 on the electron injection layer 107 by an evaporation method, and the thickness of the cathode 108 is 120nm.
Example 4
The embodiment provides a method for manufacturing a light emitting device.
Referring to fig. 1, a method for manufacturing a light emitting device includes the steps of:
(1) A transparent conductive film ITO is used as an anode 102, and the thickness of the anode 102 is 50nm.
(2) PSS as a hole injection layer 103, the hole injection layer 103 having a thickness of 30nm was deposited on the anode 102 using a solution method.
(3) TFB was deposited as a hole transport layer 104 on the hole injection layer 103 using a solution method, and the thickness of the hole transport layer 104 was 30nm.
(4) PXZ-DPS, cdSe/CdSeS/CdS (molar ratio 9:1) was deposited as a first light-emitting sublayer 1051 on the hole transport layer 104 using a solution method, the first light-emitting sublayer 1051 having a thickness of 20nm.
(5) A layer of PXZ-DPS: tmPyPb (molar ratio 10. First light-emitting sublayer 1051 and second light-emitting sublayer 1052 form quantum dot light-emitting layer 105.
(6) TmPyPb was deposited as the electron transport layer 106 on the second light emitting sublayer 1052 by evaporation, and the thickness of the electron transport layer 106 was 45nm.
(7) Deposition of Cs on the electron transport layer 106 by evaporation 2 CO 3 As the electron injection layer 107, the thickness of the electron injection layer 107 was 2nm.
(8) Al was deposited on the electron injection layer 107 by an evaporation method as a cathode 108, and the thickness of the cathode 108 was 120nm.
Example 5
The embodiment provides a method for manufacturing a light emitting device.
Referring to fig. 1, a method for manufacturing a light emitting device includes the steps of:
(1) A transparent conductive film ITO is used as an anode 102, and the thickness of the anode 102 is 50nm.
(2) PSS as a hole injection layer 103, the hole injection layer 103 having a thickness of 30nm was deposited on the anode 102 using a solution method.
(3) TFB was deposited as a hole transport layer 104 on the hole injection layer 103 using a solution method, and the thickness of the hole transport layer 104 was 30nm.
(4) CdSe/CdSeS/CdS (molar ratio 9:1) was deposited as the first light-emitting sublayer 1051 on the hole transport layer 104 by a solution method, and the thickness of the first light-emitting sublayer 1051 was 20nm.
(5) A layer of CNICCz: B3PYMPM (molar ratio 10. First light emitting sublayer 1051 and second light emitting sublayer 1052 form quantum dot light emitting layer 105.
(6) B3PYMPM is deposited as the electron transport layer 106 on the second light emitting sublayer 1052 by an evaporation method, and the thickness of the electron transport layer 106 is 45nm.
(7) Deposition of Cs on the electron transport layer 106 by evaporation 2 CO 3 As the electron injection layer 107, the thickness of the electron injection layer 107 was 2nm.
(8) Al is deposited as a cathode 108 on the electron injection layer 107 by an evaporation method, and the thickness of the cathode 108 is 120nm.
Comparative example 1
The embodiment provides a preparation method of a quantum dot light-emitting device.
A preparation method of a quantum dot light-emitting device comprises the following steps:
(1) The transparent conductive film ITO is used as an anode, and the thickness of the anode is 50nm.
(2) PSS is used as a hole injection layer, and the thickness of the hole injection layer is 40nm.
(3) TFB was deposited as a hole transport layer on the hole injection layer using a solution method, the hole transport layer having a thickness of 30nm.
(4) Depositing the TBP-DMAc CdSe/CdSeS/CdS (the molar ratio is 9:1) on the hole transport layer by a solution method to form a first luminescent sublayer, wherein the thickness of the first luminescent sublayer is 20nm.
(5) TPBi is deposited on the first luminescent sublayer by an evaporation method to serve as an electron transport layer, and the thickness of the electron transport layer is 50nm.
(6) Deposition of Cs on the electron transport layer by evaporation 2 CO 3 As the electron injection layer, the thickness of the electron injection layer was 2nm.
Al is deposited on the electron injection layer by an evaporation method to be used as a cathode, and the thickness of the cathode is 120nm.
eEQE and T of comparative examples 4-8 and comparative examples were examined 50 @1000cd/m 2 As shown in table 1, EQE: the external quantum efficiency, numerically equal to the ratio between the number of photons emitted outside the surface of the device and the number of electrons injected from the electrodes, is expressed in% and characterizes the electro-optical conversion efficiency of the device.
T 50 @1000cd/m 2 : indicating QLED at 1000cd/m 2 The time elapsed until the initial brightness thereof decayed to 50% of the initial brightness.
TABLE 1
Figure BDA0002445198520000131
As can be seen from the data in table 1, the continuous lighting time of the quantum dot light-emitting devices prepared in examples 1 to 5 is significantly better than that of the quantum dot light-emitting device prepared in comparative example 1. The EQE of the light emitting device prepared in comparative example 1 sharply decreased with increasing luminance; after the structure of the device is optimized, the roll-off speed of the EQE of the light-emitting device prepared in the embodiments 1 to 5 is obviously improved; meanwhile, the EQE of the light emitting devices prepared in examples 1 to 5 is also significantly improved compared to comparative example 1.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (12)

1. A light emitting device, comprising:
an anode and a cathode arranged oppositely;
a quantum dot light emitting layer disposed between the anode and the cathode, the quantum dot light emitting layer comprising:
a first luminescent sublayer disposed toward the anode, the first luminescent sublayer formed by mixing a TADF material and quantum dots;
a second light-emitting sublayer disposed toward the cathode, the second light-emitting sublayer formed of a mixture of an electron acceptor material and a TADF material; the electron acceptor material in the second light-emitting sublayer can form an interface type exciplex with the TADF material in the first light-emitting sublayer, and the TADF material in the second light-emitting sublayer can receive a part of holes moving from the anode direction and form excitons with electrons.
2. A light-emitting device according to claim 1, wherein the HOMO level of the electron acceptor material in the second light-emitting sub-layer is greater than the HOMO level of the TADF material in the first light-emitting sub-layer;
the LUMO level of the electron acceptor material in the second light-emitting sublayer is greater than the LUMO level of the TADF material in the first light-emitting sublayer.
3. The light-emitting device according to claim 2, wherein the HOMO level of the electron acceptor material in the second light-emitting sublayer is at least 0.4eV greater than the HOMO level of the TADF material in the first light-emitting sublayer;
the LUMO level of the electron acceptor material in the second light-emitting sublayer is at least 0.4eV greater than the LUMO level of the TADF material in the first light-emitting sublayer.
4. The light emitting device of claim 1~3, wherein the TADF material is selected from the group consisting of: one or more of t4CzIPN, 4CzFCN, 3ACR-TRZ, 4CzCNPy, TBP-DMAc, tri-PXZ-TRZ, tmCzTrz, DMAC-DPS, CNICCz, CNICtCz, 5CzCN, TP-C-TPB and PXZ-DPS.
5. The light emitting device of any one of claims 1~3 wherein the electron acceptor material is selected from the group consisting of: one or more of DPEPO, TPBi, tmPyPb, BCP, bphen, tmPyTz, B3PYMPM, 3TPYMB and PO-T2T.
6. The light-emitting device of claim 1~3 wherein the molar ratio of the quantum dots in the first luminescent sublayer to the TADF material is 1: (1.5 to 99); and/or
The molar ratio of the TADF material to the electron acceptor material in the second light-emitting sublayer is 1: (0.4 to 99).
7. The light-emitting device according to any one of claims 1~3, wherein the thickness of the first luminescent sublayer is 10-30nm; and/or
The thickness of the second light-emitting sublayer is 3-15nm.
8. The light emitting device of any one of claims 1~3 further comprising:
a hole functional layer disposed between the anode and the quantum dot light emitting layer; and/or the presence of a gas in the gas,
an electronically functional layer disposed between the cathode and the quantum dot light emitting layer.
9. The light-emitting device according to claim 8, wherein the hole function layer comprises:
a hole injection layer disposed toward the anode, the hole injection layer being of a material selected from the group consisting of: PSS, WO PEDOT 3 、MoO 3 、V 2 O 5 、F 4 -one or more of TCNQ and HATCN; and/or
A hole transport layer disposed toward the first emissive sub-layer, the hole transport layer being of a material selected from: poly-TPD, TFB, PVK, NPB, TAPC, TCTA, mCP, CBP, mCBP, CDBP, niO, cu 2 O and CuSCN.
10. The light-emitting device according to claim 8, wherein the electronic function layer comprises:
an electron injection layer disposed toward the cathode, the electron injection layer being of a material selected from the group consisting of: liF, csF, liq, cs 2 CO 3 、Li 2 CO 3 One or more of Ba and Yb; and/or
An electron transport layer disposed toward the second emissive sublayer, the electron transport layer being of a material selected from: znO, znAlO, znMgO, znGaO, tiO 2 、SnO 2 、TPBi、TmPyPb、BCP、Bphen、TmPyTz、B3PYMPOne or more of M, 3TPYMB and PO-T2T.
11. A method for manufacturing a light emitting device is characterized by comprising the following steps:
sequentially laminating an anode, a first light-emitting sublayer, a second light-emitting sublayer and a cathode on a substrate; or alternatively
Sequentially laminating a cathode, a second light-emitting sublayer, a first light-emitting sublayer and an anode on a substrate;
wherein the first luminescent sublayer is formed by mixing TADF materials and quantum dots;
the second light-emitting sublayer is formed by mixing an electron acceptor material and a TADF material; the electron acceptor material in the second light-emitting sub-layer may form an interface type exciplex with the TADF material in the first light-emitting sub-layer, and the TADF material in the second light-emitting sub-layer may receive a portion of holes moving from the anode direction to form excitons with electrons.
12. A display device, comprising:
a light-emitting device according to any one of claims 1 to 10; or alternatively
A light-emitting device obtained by the production method according to claim 11.
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