WO2020134161A1

WO2020134161A1 - Quantum dot light emitting diode and preparation method thereof

Info

Publication number: WO2020134161A1
Application number: PCT/CN2019/104010
Authority: WO
Inventors: 聂志文; 杨一行
Original assignee: Tcl科技集团股份有限公司
Priority date: 2018-12-29
Filing date: 2019-09-02
Publication date: 2020-07-02
Also published as: CN111384280A; CN111384280B

Abstract

Disclosed are a quantum dot light-emitting diode and a preparation method thereof, wherein the quantum dot light-emitting diode comprises a functional layer arranged between an anode and a quantum dot light-emitting layer, the functional layer comprises an N-layer stacked functional structural unit, the functional structural unit is composed of a hole transport layer and an electron blocking material layer, which are stacked, the hole transport layer in the functional structural unit is arranged close to the anode, and the electron blocking material layer in the functional structural unit is arranged close to the quantum dot light-emitting layer, the n is an integer greater than or equal to 2, and in adjacent two-layer functional structural units in the N-layer stacked functional structural unit, the HOMO energy level of the material of the electron blocking material layer close to the quantum dot light-emitting layer is greater than that of the material of the the electron blocking material layer close to the anode. The present disclosure can improve the transmission rate of hole transport to the quantum dot light-emitting layer through the arrangement of the function layer, so as to balance the injection rate of electrons and holes, improve the recombination efficiency of carriers in the quantum dot layer, and further improve the light-emitting efficiency, stability and service life of the quantum dot light-emitting diode.

Description

Quantum dot light-emitting diode and preparation method thereof

Technical field

The present disclosure relates to the field of quantum dots, in particular to a quantum dot light-emitting diode and a preparation method thereof.

Background technique

The quantum dot light-emitting diode (QLED) is a typical sandwich structure, which is composed of electrodes, functional layers, and light-emitting layers. Under the excitation of the applied voltage, the carriers enter the quantum dots from the functional layers through the electrodes at both ends to recombine to form excitons. The recombined excitons release photons in the form of radiation transitions, thereby emitting light. Because colloidal quantum dots have the characteristics of high luminous efficiency, high color purity, wide color gamut, and good stability, QLED not only inherits these excellent properties of quantum dots, but also has self-luminous, wide viewing angle, flexible, etc. Features, showing great commercial application prospects, have become an important research direction in the field of new generation of new and lighting display. At the same time, since the quantum dot itself is processed and prepared by the solution method, it is very suitable for configuration as an ink, and then printing, inkjet and other methods are used to achieve large-scale and large-area preparation. At present, after more than 20 years of research and development, QLED devices have developed rapidly and achieved remarkable results. Especially in recent years, from the control of the functional layer to the control of the quantum dot itself, the alloying of the quantum dot and the growth of the thick shell layer have greatly promoted the performance of QLED devices.

At this stage, for QLED devices, how to simultaneously improve device efficiency, life and stability is still a very challenging problem. Generally, semiconductor quantum dots generally have a deep HOMO energy level, and there is a large potential barrier for charge transport in each functional layer, resulting in an imbalance between electron and hole injection during device operation. On the one hand, a high carrier injection barrier will increase the operating voltage of the device; on the other hand, unbalanced charge injection will greatly reduce the recombination probability of carriers in the light-emitting layer, and easily lead to non-radiative transitions of excitons , Thereby affecting the luminous efficiency and life of the device.

Therefore, the existing technology needs to be improved and developed.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, the purpose of the present disclosure is to provide a quantum dot light emitting diode and a preparation method thereof, aiming to solve the recombination probability of carriers in the light emitting layer caused by the imbalance of carrier injection in the existing QLED device The problem of reducing the luminous efficiency and life of the device is reduced.

The technical solutions of the present disclosure are as follows:

A quantum dot light-emitting diode includes a cathode, an anode, and a quantum dot light-emitting layer disposed between the cathode and the anode, wherein a functional layer is provided between the anode and the quantum dot light-emitting layer, and the functional layer includes n layer stacks A functional structural unit is provided, the functional structural unit is composed of a hole transport layer and an electron blocking material layer that are stacked, the hole transport layer in the functional structural unit is disposed near the anode, and the electron blocking in the functional structural unit The material layer is disposed near the quantum dot light-emitting layer, n is an integer greater than or equal to 2, and in the two adjacent functional functional units of the n-layer functional structural unit, the electron blocking material layer material near the quantum dot light-emitting layer The HOMO energy level is greater than that of the electron blocking material layer material near the anode.

A preparation method of quantum dot light-emitting diode, which includes the following steps:

Provide substrate;

A functional layer is prepared on the substrate. The functional layer includes n layers of stacked functional structural units. The functional structural unit is composed of a stacked hole transport layer and an electron blocking material layer. The hole transport layer is disposed near the anode, the electron blocking material layer in the functional structural unit is disposed near the quantum dot light emitting layer, the n is an integer greater than or equal to 2, and two adjacent layers in the n-layer functional structural unit In the functional structural unit, the HOMO energy level of the electron blocking material layer material near the quantum dot light emitting layer is greater than the HOMO energy level of the electron blocking material layer material near the anode.

Beneficial effect: The quantum dot light-emitting diode provided by the present disclosure can improve the transmission rate of holes from the quantum dot light-emitting layer through the arrangement of the functional layer, thereby balancing the injection rate of electrons and holes, so as to improve the carrier in the quantum dot Recombination efficiency in the layer, thereby improving the luminous efficiency, stability and service life of quantum dot light-emitting diodes.

BRIEF DESCRIPTION

FIG. 1 is a schematic structural diagram of a preferred embodiment of a quantum dot light emitting diode of the present disclosure.

2 is a schematic diagram of the energy band structure of the quantum dot light emitting diode of the present disclosure.

FIG. 3 is a flowchart of a preferred embodiment of a method for manufacturing a quantum dot light emitting diode of the present disclosure.

detailed description

The present disclosure provides a quantum dot light emitting diode and a preparation method thereof. In order to make the purpose, technical solution and effects of the present disclosure clearer and more specific, the present disclosure will be described in further detail below. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not intended to limit the present disclosure.

There are many forms of quantum dot light emitting diodes, and the quantum dot light emitting diodes are divided into a positive structure and an inverse structure. In some embodiments, the positive structure quantum dot light emitting diodes include a substrate stacked from bottom to top , Anode, quantum dot light-emitting layer, electron transport layer and cathode. In yet another embodiment of the present disclosure, the substrate may include a substrate, an anode stacked on the surface of the substrate, and a hole injection layer stacked on the anode; in yet another embodiment of the present disclosure, the The substrate may include a substrate, an anode stacked on the surface of the substrate, a hole injection layer stacked on the surface of the anode, and a hole transport layer stacked on the surface of the hole injection layer.

In some embodiments, the inverted-type quantum dot light-emitting diode may include a substrate, a cathode, a quantum dot light-emitting layer, and an anode layered from bottom to top. In one embodiment of the present disclosure, the substrate may include a substrate, a cathode stacked on the surface of the substrate, and an electron injection layer stacked on the surface of the cathode; in yet another embodiment of the present disclosure, the The substrate may include a substrate, a cathode stacked on the surface of the substrate, an electron injection layer stacked on the surface of the cathode, and an electron transport layer stacked on the surface of the electron injection layer; in still another embodiment of the present disclosure, the The substrate may include a substrate, a cathode stacked on the surface of the substrate, an electron injection layer stacked on the surface of the cathode, an electron transport layer stacked on the surface of the electron injection layer, and a hole blocking layer stacked on the surface of the electron transport layer.

In the specific embodiments of the present disclosure, the positive-type quantum dot light-emitting diode shown in FIG. 1 will be mainly used as an example for introduction. Specifically, as shown in FIG. 1, the positive-type quantum dot light-emitting diode includes a substrate 10, an anode 20, a functional layer, a quantum dot light-emitting layer 40, an electron transport layer 50, and a cathode 60 stacked from bottom to top. The functional layer includes n layers of stacked functional structural units. The functional structural unit is composed of a stacked hole transport layer 31 and an electron blocking material layer 32. The hole transport layer 31 in the functional structural unit is close to the anode 20 Setting, the electron blocking material layer 32 in the functional structural unit is disposed close to the quantum dot light emitting layer 40, the n is an integer greater than or equal to 2, and two adjacent functional structural units in the n-layer functional structural unit The HOMO energy level of the material of the electron blocking material layer 32 near the quantum dot light emitting layer 40 is greater than the HOMO energy level of the material of the electron blocking material layer 32 near the anode 20.

In this embodiment, the quantum dot light emitting diode can effectively balance the injection rate of electrons and holes through the arrangement of the functional layer, thereby improving the recombination efficiency of carriers in the quantum dot light emitting layer, and thereby improving the luminous efficiency of the quantum dot light emitting diode. Stability and service life. The mechanism for achieving the above effect is as follows:

For quantum dot light-emitting diodes, during the transport of holes from the anode to the quantum dot light-emitting layer, the deeper the HOMO energy level of the holes in each transport layer, the greater the barrier during hole transport and the tunneling of holes The higher the energy required for the transport layer, the slower the hole transport rate; the functional layer in the quantum dot light-emitting diode described in this embodiment includes n layers of stacked functional structural units, and the functional structural units are stacked Composed of a hole transport layer and an electron blocking material layer, the hole transport layer in the functional structural unit is disposed near the anode, the electron blocking material layer in the functional structural unit is disposed near the quantum dot light emitting layer, and n is greater than Equal to an integer, and in the adjacent two functional structural units of the n-layer functional structural unit, the HOMO energy level of the electron blocking material layer material near the quantum dot light emitting layer is greater than the HOMO energy of the electron blocking material layer material near the anode level. As shown in FIG. 2, during the hole transport from the anode to the quantum dot light emitting layer, the HOMO energy level of the electron blocking material layer gradually increases, and the maximum HOMO energy level of the electron blocking material layer is less than the quantum dot light emission Layer HOMO energy level, this HOMO energy level increases in a stepped electron blocking material layer is very helpful to accelerate the hole transport performance, thereby balancing the injection rate of electrons and holes, in order to improve the carrier in the quantum dot layer The composite efficiency of the LED can further improve the luminous efficiency, stability and service life of the quantum dot light-emitting diode.

In some embodiments, the number of layers of the electron blocking material layer and the hole transport layer is the same, and the number of layers of the electron blocking material layer and the hole transport layer is 2-10 layers. Preferably, the number of layers of the electron blocking material layer and the hole transport layer are 2-5 layers.

In some embodiments, the thickness of each electron blocking material layer is 2-5 nm.

In some embodiments, the electron blocking material layer has a HOMO energy level of -5.0 to -8.0 eV. In some specific embodiments, in the two adjacent functional structural units of the n-layer functional structural unit, the electron blocking material layer material near the quantum dot light emitting layer has a HOMO energy level greater than that of the electron blocking material layer material near the anode HOMO energy level, the HOMO energy level difference between adjacent electron blocking material layers is -0.1 ~ -0.5eV. In this embodiment, the electron blocking material layer whose HOMO energy level is increased stepwise can effectively accelerate the hole transport rate, so that the hole enters the quantum dot light-emitting layer and the electron enters the quantum dot light-emitting layer to achieve a balance State, increasing the recombination probability of electrons and holes.

In some embodiments, the electron blocking material layer material is selected from one or more of PVK, Poly-TPD, NPB, TCTA, TAPC, CBP, TFB, and DNA, but is not limited thereto.

In some embodiments, the material of the electron blocking material layer is selected from one or more of compound doped PVK, Poly-TPD, NPB, TCTA, TAPC, CBP, TFB, and DNA, and the compound is selected from One of Li-TFSI, NiO, CuSCN, MoO ₃ , CuO, V ₂ O ₅ or CuS, but is not limited thereto. In some embodiments, the electron blocking layer material is selected from one of PVK, Poly-TPD, NPB, TCTA, TAPC, CBP, TFB, and DNA and Li-TFSI, NiO, CuSCN, MoO ₃ , CuO, V A mixed material composed of ₂ O ₅ and CuS. The purpose of selecting a mixed material compound doped electron blocking material is mainly to adjust the LUMO energy level of the electron blocking material layer material, to achieve a stepped barrier between level energy levels, and thereby to adjust the electron and hole transport rate, Improve the recombination efficiency of excitons. As an example, the material of the electron blocking material layer is selected from PVK:Li-TFSI, PVK:NiO, PVK:CuSCN, PVK:MoO ₃ , PVK:CuO, PVK:V ₂ O ₅ , PVK:CuS, Poly-TPD, Poly-TPD: Li-TFSI, Poly-TPD: -NiO, Poly-TPD: CuSCN, Poly-TPD: MoO ₃ , Poly-TPD: CuO, Poly-TPD: V ₂ O ₅ , Poly-TPD: CuS, NPB , NPB: Li-TFSI, NPB-TPD: -NiO, NPB-TPD: CuSCN, NPB: MoO ₃ , NPB: CuO, NPB: V ₂ O ₅ , NPB: CuS, TCTA, TCTA: Li-TFSI, TCTA- TPD:-NiO, TCTA-TPD:CuSCN, TCTA:MoO ₃ , TCTA:CuO, TCTA:V ₂ O ₅ , TCTA:CuS, TAPC, TAPC:Li-TFSI, TAPC-TPD:-NiO, TAPC-TPD: CuSCN, TAPC: MoO ₃ , TAPC: CuO, TAPC: V ₂ O ₅ , TAPC: CuS, CBP, CBP: Li-TFSI, CBP-TPD: -NiO, CBP-TPD: CuSCN, CBP: MoO ₃ , CBP: CuO, CBP: V ₂ O ₅ , CBP: CuS, TFB, TFB: Li-TFSI, TFB-TPD: -NiO, TFB-TPD: CuSCN, TFB: MoO ₃ , TFB: CuO, TFB: V ₂ O ₅ and TFB: One or more of CuS, but not limited to this.

In some embodiments, the functional layer includes at least one functional structural unit, wherein the LUMO energy level in the electron blocking material layer in the functional structural unit is greater than the LUMO energy level of the hole transport layer. In this embodiment, when the LUMO level of the electron blocking material layer is higher than the LUMO level of the hole transport layer, electrons can be better bound to the quantum dot light-emitting layer, thereby increasing the recombination probability of electrons and holes , Greatly improve the luminous efficiency of quantum dots. In a specific embodiment, the LUMO energy level of the hole transport layer is -2.0 to -3.0 eV.

In some embodiments, the hole transport layer material is selected from TFB, PVK, Poly-TBP, Poly-TPD, NPB, TCTA, TAPC, CBP, PEODT: PSS, MoO ₃ , WoO ₃ , NiO, CuO, V One or more of ₂ O ₅ and CuS, but not limited to this. In some embodiments, the thickness of each hole transport layer is 10-40 nm.

In some embodiments, the quantum dot light-emitting layer material is selected from one or more of group II-VI compounds, group III-V compounds, and group I-III-VI compounds, but is not limited thereto. As an example, the group II-VI compound is selected from CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS; CdZnSeS, CdZnSeTe and CdZnSTe One or more; the group III-V compound is selected from one or more of InP, InAs, GaP, GaAs, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP, and InAlNP; the I -Group III-VI compounds are selected from one or more of CuInS ₂ , CuInSe ₂ and AgInS ₂ .

In some embodiments, the thickness of the quantum dot light emitting layer is 30-120 nm.

In some embodiments, the anode material is selected from one or more of Li, Ca, Ba, LiF, CsN ₃ , Cs ₂ CO ₃ , CsF, Ag, Mo, Al, Cu, and Au, but is not limited to this. In some embodiments, the thickness of the anode is 20-150 nm.

In some embodiments, the electron transport layer material is selected from one or more of ZnO, TiO _2, Alq ₃ , SnO, ZrO, AlZnO, ZnSnO, BCP, TAZ, PBD, TPBI, Bphen, and CsCO ₃ , But it is not limited to this. In some embodiments, the thickness of the electron transport layer is 10-120 nm. In some embodiments, the thickness of the electron transport layer is 30-120 nm.

In some embodiments, the cathode material is selected from one of ITO, FTO, or ZTO. In some embodiments, the thickness of the cathode is 60-130 nm.

It should be noted that the quantum dot light emitting diode of the present disclosure may further include one or more of the following functional layers: a hole injection layer provided between the anode and the hole transport layer, and a hole injection layer provided between the cathode and the functional layer Electron injection layer.

Embodiments of the present disclosure also provide a method for manufacturing a quantum dot light emitting diode, as shown in FIG. 3, including the steps of:

S10, provide substrate;

S20. Prepare a functional layer on the substrate. The functional layer includes n layers of stacked functional structural units. The functional structural unit is composed of a stacked hole transport layer and an electron blocking material layer. The functional structural unit The hole transport layer in is arranged near the anode, the electron blocking material layer in the functional structural unit is arranged near the quantum dot light emitting layer, the n is an integer greater than or equal to 2, and the adjacent in the n-layer functional structural unit In the two-layer functional structural unit, the HOMO energy level of the electron blocking material layer material near the quantum dot light emitting layer is greater than the HOMO energy level of the electron blocking material layer material near the anode.

Specifically, the quantum dot light emitting diode is divided into an upright structure and an inverted structure. The upright structure includes an anode, a cathode, and a quantum dot light-emitting layer disposed between the anode and the cathode. The anode of the upright structure is disposed on the substrate, and hole transport can also be provided between the anode and the quantum dot light-emitting layer. The hole functional layer such as a layer, a hole injection layer, and an electron blocking layer may be provided with an electron functional layer such as an electron transport layer, an electron injection layer, and a hole blocking layer between the cathode and the quantum dot light emitting layer. The inverted structure includes an anode, a cathode, and a quantum dot light-emitting layer disposed between the anode and the cathode. The cathode of the inverted structure is disposed on the substrate. A hole transport layer can also be provided between the anode and the quantum dot light-emitting layer. A hole functional layer such as a hole injection layer and an electron blocking layer may be provided with an electron functional layer such as an electron transport layer, an electron injection layer and a hole blocking layer between the cathode and the quantum dot light emitting layer.

For the upright structure, the bottom electrode provided on the substrate is an anode. In some embodiments of the present disclosure, the substrate may include a substrate and a bottom electrode stacked on the surface of the substrate; In some embodiments, the substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, and a hole injection layer stacked on the surface of the bottom electrode.

For the inverted structure, the bottom electrode provided on the substrate is the cathode. In some embodiments of the present disclosure, the substrate may be the bottom electrode provided on the substrate; in still other embodiments of the present disclosure, the The substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, an electron injection layer stacked on the surface of the bottom electrode, and a quantum dot light emitting layer stacked on the surface of the electron injection layer. In still other embodiments of the present disclosure, the substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, an electron transport layer stacked on the surface of the electron injection layer, and quantum dots stacked on the surface of the electron transport layer Light emitting layer; in still other embodiments of the present disclosure, the substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, an electron injection layer stacked on the surface of the bottom electrode, and a layer stacked on the surface of the electron injection layer An electron transport layer and a quantum dot light emitting layer stacked on the surface of the electron transport layer; in still other embodiments of the present disclosure, the substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, and a bottom electrode stacked on the surface An electron injection layer on the surface, an electron transport layer stacked on the surface of the electron injection layer, a hole blocking layer stacked on the surface of the electron transport layer, and a quantum dot light emitting layer stacked on the surface of the electron blocking layer; In an embodiment, the substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, an electron injection layer stacked on the surface of the bottom electrode, an electron transport layer stacked on the surface of the electron injection layer, and a layer stacked on the electron transport The hole blocking layer on the surface of the layer, the quantum dot light emitting layer stacked on the surface of the hole blocking layer, and the electron blocking layer stacked on the surface of the quantum dot light emitting layer.

In some embodiments, the substrate is a substrate. In some embodiments of the present disclosure, the substrate may include a base and an anode stacked on the surface of the base; in still other embodiments of the present disclosure, the substrate may It includes a substrate, an anode stacked on the surface of the substrate, and a hole injection layer stacked on the surface of the anode.

In the present disclosure, each layer preparation method may be a chemical method or a physical method, wherein the chemical method includes but is not limited to one of chemical vapor deposition method, continuous ion layer adsorption and reaction method, anodizing method, electrolytic deposition method, and co-precipitation method One or more; physical methods include but are not limited to solution methods (such as spin coating method, printing method, blade coating method, dipping and pulling method, dipping method, spraying method, roll coating method, casting method, slit coating method) Or strip coating method, etc.), evaporation method (such as thermal evaporation method, electron beam evaporation method, magnetron sputtering method or multi-arc ion coating method, etc.), deposition method (such as physical vapor deposition method, atomic layer One or more of deposition method, pulsed laser deposition method, etc.).

The disclosure will be described in detail below through examples.

Example 1

A quantum dot light-emitting diode includes a substrate, an anode, a hole injection layer, a functional layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode, which are arranged in layers from bottom to top. The functional layer includes 5 layers arranged alternately A hole transport layer and a 5-layer electron transport layer. The bottom layer of the functional layer is a hole transport layer and is located near the anode. The top layer of the functional layer is an electron blocking material layer and is located near the quantum dot light-emitting layer. In the direction of the cathode, the materials of the electron blocking material layer are PVK, PVK doped with 1.5wt.% Li-TFSI, PVK doped with 3wt.% Li-TFSI, and 4.5wt.% Li-TFSI PVK and 6wt.% Li-TFSI PVK; the anode is ITO with a thickness of 100nm; the hole injection layer material is PEDOT:PSS with a thickness of 40nm; the hole transport layer material is TFB with each layer empty The thickness of the hole transport layer is 10 nm; the material of the quantum dot light emitting layer is InP/ZnS with a thickness of 100 nm; the thickness of each electron blocking material layer is 4 nm; the material of the electron transport layer is ZnO with a thickness of 100nm; the cathode is Al and the thickness is 50nm.

Example 2

A quantum dot light-emitting diode includes a substrate, an anode, a hole injection layer, a functional layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode, which are arranged in layers from bottom to top. The functional layer includes 5 layers arranged alternately A hole transport layer and a 5-layer electron transport layer. The bottom layer of the functional layer is a hole transport layer and is located near the anode. The top layer of the functional layer is an electron blocking material layer and is located near the quantum dot light-emitting layer. In the direction of the cathode, the material of the electron blocking material layer is TFB, TFB doped with 1.5 wt.% Li-TFSI, TFB doped with 3 wt.% Li-TFSI, and 4.5 wt.% Li-TFSI. TFB and 6wt.% Li-TFSI TFB; the anode is ITO with a thickness of 100nm; the hole injection layer material is PEDOT:PSS with a thickness of 40nm; the hole transport layer material is PVK, each layer is empty The thickness of the hole transport layer is 15 nm; the material of the quantum dot light emitting layer is InP/ZnS with a thickness of 40 nm; the thickness of each electron blocking material layer is 4 nm; the material of the electron transport layer is SnO with a thickness of 100 nm; The cathode is Al and the thickness is 50 nm.

Example 3

A quantum dot light-emitting diode includes a substrate, an anode, a hole injection layer, a functional layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode, which are arranged in layers from bottom to top. The functional layer includes 5 layers arranged alternately A hole transport layer and a 5-layer electron transport layer. The bottom layer of the functional layer is a hole transport layer and is located near the anode. The top layer of the functional layer is an electron blocking material layer and is located near the quantum dot light-emitting layer. In the direction of the cathode, the materials of the electron blocking material layer are TCTA, TCTA doped with 1.5wt.% MoO ₃ , TCTA doped with 3wt.% MoO ₃ , TCTA with 4.5wt.% MoO ₃ , and 6wt .TCA of %MoO ₃ ; the anode is ITO with a thickness of 100 nm; the hole injection layer material is PEDOT:PSS with a thickness of 40 nm; the hole transport layer material is Poly-TBP with hole transport per layer The thickness of the layer is 8 nm; the material of the quantum dot light-emitting layer is InP/ZnS with a thickness of 80 nm; the thickness of each electron blocking material layer is 4 nm; the material of the electron transport layer is TiO with a thickness of 100 nm; The cathode is Al and the thickness is 50 nm.

Example 4

A quantum dot light-emitting diode includes a substrate, an anode, a hole injection layer, a functional layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode, which are arranged in layers from bottom to top. The functional layer includes 5 layers arranged alternately A hole transport layer and a 5-layer electron transport layer. The bottom layer of the functional layer is a hole transport layer and is located near the anode. The top layer of the functional layer is an electron blocking material layer and is located near the quantum dot light-emitting layer. In the direction of the cathode, the materials of the electron blocking material layer are PVK, PVK doped with 1.5wt.% Li-TFSI, PVK doped with 3wt.% Li-TFSI, and 4.5wt.% Li-TFSI PVK and PVK of 6wt.% Li-TFSI; the anode is ITO with a thickness of 100nm; the hole injection layer material is PEDOT:PSS with a thickness of 40nm; the hole transport layer material is Poly-TPD, each The thickness of the hole transport layer is 10 nm; the material of the quantum dot light-emitting layer is CdZnS/CdZnSe/ZnS with a thickness of 120 nm; the thickness of each electron blocking material layer is 4 nm; the material of the electron transport layer is AlZnO , The thickness is 100nm; the cathode is Al, the thickness is 50nm.

Example 5

A quantum dot light-emitting diode includes a substrate, an anode, a hole injection layer, a functional layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode, which are arranged in layers from bottom to top. The functional layer includes 5 layers arranged alternately A hole transport layer and a 5-layer electron transport layer. The bottom layer of the functional layer is a hole transport layer and is located near the anode. The top layer of the functional layer is an electron blocking material layer and is located near the quantum dot light-emitting layer. In the direction of the cathode, the material of the electron blocking material layer is TFB, TFB doped with 1.5 wt.% Li-TFSI, TFB doped with 3 wt.% Li-TFSI, and 4.5 wt.% Li-TFSI. TFB and 6wt.% Li-TFSI TFB; the anode is ITO with a thickness of 100nm; the hole injection layer material is PEDOT:PSS with a thickness of 40nm; the hole transport layer material is TCTA, each layer is empty The thickness of the hole transport layer is 20 nm; the material of the quantum dot light-emitting layer is CdZnS/CdZnSe/ZnS with a thickness of 30 nm; the thickness of each electron blocking material layer is 4 nm; the material of the electron transport layer is TPBI with a thickness Is 100 nm; the cathode is Al and the thickness is 50 nm.

Example 6

A quantum dot light-emitting diode includes a substrate, an anode, a hole injection layer, a functional layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode, which are arranged in layers from bottom to top. The functional layer includes 5 layers arranged alternately A hole transport layer and a 5-layer electron transport layer. The bottom layer of the functional layer is a hole transport layer and is located near the anode. The top layer of the functional layer is an electron blocking material layer and is located near the quantum dot light-emitting layer. In the direction of the cathode, the materials of the electron blocking material layer are TCTA, TCTA doped with 1.5wt.% MoO ₃ , TCTA doped with 3wt.% MoO ₃ , TCTA with 4.5wt.% MoO ₃ , and 6wt .TCA of %MoO ₃ ; the anode is ITO with a thickness of 100 nm; the hole injection layer material is PEDOT:PSS with a thickness of 40 nm; the hole transport layer material is TFB, each hole transport layer has a The thickness is 10 nm; the material of the quantum dot light emitting layer is CdZnS/CdZnSe/ZnS, and the thickness is 110 nm; the thickness of each electron blocking material layer is 4 nm; the material of the electron transport layer is ZnO, and the thickness is 100 nm ; The cathode is Al with a thickness of 50 nm.

In summary, the quantum dot light emitting diode provided by the present disclosure includes a cathode, an anode, and a quantum dot light emitting layer disposed between the cathode and the anode. A functional layer is provided between the anode and the quantum dot light emitting layer. It includes n layers of stacked functional structural units, which are composed of a hole transport layer and an electron blocking material layer that are stacked, the hole transport layer in the functional structural unit is arranged near the anode, and the functional structural unit The electron blocking material layer in is arranged close to the quantum dot light emitting layer, n is an integer greater than or equal to 2, and in the adjacent two functional structural units of the n layer functional structural unit, the electron blocking near the quantum dot light emitting layer The HOMO energy level of the material layer material is greater than the HOMO energy level of the electron blocking material layer material near the anode. The quantum dot light-emitting diode of the present disclosure can increase the transmission rate of holes from the quantum dot light-emitting layer through the arrangement of the functional layer, thereby balancing the injection rate of electrons and holes to improve the recombination efficiency of carriers in the quantum dot layer , Thereby improving the luminous efficiency, stability and service life of quantum dot light-emitting diodes.

It should be understood that the application of the present disclosure is not limited to the above examples, and those of ordinary skill in the art may make improvements or changes based on the above description, and all such improvements and changes shall fall within the protection scope of the claims appended to the present disclosure.

Claims

A quantum dot light emitting diode, including a cathode, an anode, and a quantum dot light emitting layer disposed between the cathode and the anode, characterized in that a functional layer is provided between the anode and the quantum dot light emitting layer, and the functional layer includes n A functional structural unit arranged in layers, the functional structural unit consisting of a hole transport layer and an electron blocking material layer stacked, the hole transport layer in the functional structural unit is arranged close to the anode, and the The electron blocking material layer is disposed close to the quantum dot light-emitting layer, n is an integer greater than or equal to 2, and the electron blocking material layer near the quantum dot light-emitting layer in the two adjacent functional functional units of the n-layer functional structural unit The HOMO energy level of the material is greater than the HOMO energy level of the electron blocking material layer material near the anode.
The quantum dot light-emitting diode according to claim 1, wherein the material of the electron blocking material layer is selected from one or more of PVK, Poly-TPD, NPB, TCTA, TAPC, CBP, TFB and DNA .
The quantum dot light emitting diode according to claim 1, wherein the material of the electron blocking material layer is selected from one of compound doped PVK, Poly-TPD, NPB, TCTA, TAPC, CBP, TFB and DNA One or more, the compound is selected from one of Li-TFSI, NiO, CuSCN, MoO 3 , CuO, V 2 O 5 or CuS.
The quantum dot light emitting diode according to claim 1, wherein the hole transport layer material is selected from TFB, PVK, Poly-TBP, Poly-TPD, NPB, TCTA, TAPC, CBP, PEODT: PSS, MoO 3. One or more of WoO 3 , NiO, CuO, V 2 O 5 and CuS.
The quantum dot light-emitting diode according to claim 1, wherein the electron blocking material layer has a HOMO energy level of -5.0 to -8.0 eV.
The quantum dot light-emitting diode according to claim 1, wherein 2≤n≤10.
The quantum dot light emitting diode according to claim 1, wherein 2≤n≤5.
The quantum dot light-emitting diode according to claim 1, wherein the HOMO energy level difference between adjacent electron blocking material layers is -0.1 to -0.5 eV.
The quantum dot light-emitting diode according to claim 1, wherein the functional layer includes at least one functional structural unit, wherein the LUMO energy level in the electron blocking material layer in the functional structural unit is greater than the The LUMO level of the hole transport layer.
The quantum dot light-emitting diode according to claim 9, wherein the LUMO energy level of the hole transport layer is -2.0 to -3.0 eV.
The quantum dot light emitting diode according to claim 1, wherein the thickness of each electron blocking material layer is 2-5 nm.
The quantum dot light-emitting diode according to claim 1, wherein the thickness of each hole transport layer is 10-100 nm.
The quantum dot light-emitting diode according to claim 1, wherein the material of the quantum dot light-emitting layer is selected from one or more of group II-VI compounds, group III-V compounds and group I-III-VI compounds Species.
The quantum dot light emitting diode according to claim 1, wherein an electron transport layer is further provided between the cathode and the quantum dot light emitting layer, and the electron transport layer material is selected from ZnO, TiO 2 , Alq 3 , SnO , ZrO, AlZnO, ZnSnO, BCP, TAZ, PBD, TPBI, Bphen and CsCO 3 one or more.
A preparation method of quantum dot light-emitting diode, which is characterized by comprising the following steps:

Provide substrate;

A functional layer is prepared on the substrate. The functional layer includes n layers of stacked functional structural units. The functional structural unit is composed of a stacked hole transport layer and an electron blocking material layer. The hole transport layer is disposed near the anode, the electron blocking material layer in the functional structural unit is disposed near the quantum dot light emitting layer, the n is an integer greater than or equal to 2, and two adjacent layers in the n-layer functional structural unit In the functional structural unit, the HOMO energy level of the electron blocking material layer material near the quantum dot light emitting layer is greater than the HOMO energy level of the electron blocking material layer material near the anode.