WO2023056829A1

WO2023056829A1 - Quantum dot light-emitting layer, preparation method for quantum dot light-emitting layer, and quantum dot light-emitting diode device

Info

Publication number: WO2023056829A1
Application number: PCT/CN2022/118788
Authority: WO
Inventors: 周礼宽; 杨一行
Original assignee: Tcl科技集团股份有限公司
Priority date: 2021-10-08
Filing date: 2022-09-14
Publication date: 2023-04-13
Also published as: CN115960601A

Abstract

Disclosed in the present application are a quantum dot light-emitting layer, a preparation method for a quantum dot light-emitting layer, and a quantum dot light-emitting diode (QLED) device. The quantum dot light-emitting layer comprises a quantum dot material and a main body material, wherein the quantum dot material comprises first quantum dots, and the main body material fills gaps between the first quantum dots; and the first quantum dots are nuclear-shell quantum dots, and the band gap width of the main body material is not less than the band gap width of the outermost shell material of the first quantum dots. Therefore, the current efficiency and stability of a QLED are improved.

Description

Quantum dot light-emitting layer, preparation method of quantum dot light-emitting layer, and quantum dot light-emitting diode device

This application claims the priority of the Chinese patent application with the application number 202111172956.6 and the application title "A Quantum Dot Light-Emitting Layer and Its Preparation Method and Quantum Dot Light-Emitting Diode Device" filed at the China Patent Office on October 08, 2021 , the entire contents of which are incorporated in this application by reference.

technical field

The present application relates to the field of display technology, in particular to a quantum dot light emitting layer, a preparation method of the quantum dot light emitting layer and a quantum dot light emitting diode device.

Background technique

Quantum dot light-emitting diode (QLED) is an ideal solution for next-generation display technology, because quantum dots have nearly 100% luminous efficiency, high color purity (luminous peak width less than 25nm) and adjustable wavelength (from ultraviolet to infrared), etc. Excellent luminescence characteristics and chemical/photochemical stability of inorganic crystals can also use large-area, high-yield solution processing methods to achieve flexible displays with high color gamut, high contrast, fast response, high cost performance, and low energy consumption. It has been studied and paid attention to by many scientific researchers at home and abroad.

In recent years, with the in-depth research on the performance of QLED devices, great progress has been made in current efficiency (CE) and lifetime (T95@1000nit). The external quantum efficiency (EQE) of QLED devices based on cadmium-containing systems is as high as 20.5%, The working life is as long as 30,000 hours, which is already comparable to the performance of organic light-emitting diodes (OLEDs) in commercial applications.

In a QLED device, the device consists of an anode (Anode), a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL) and a cathode (Cathode). The emission layer is It is prepared by the solution method of quantum dot nanoparticles, and the quantum dot nanoparticles are arranged in a layer-by-layer stacking manner; when the device is working normally, electrons and holes are injected into the quantum dot light-emitting layer through the anode and cathode through the transport layer for further processing. Composite glow. Common quantum dot nanoparticles are generally in a regular spherical or cubic structure. During the process of stacking the light-emitting layer by the solution method, a gap will be formed between the quantum dots, resulting in the inability of electrons and holes to be effectively transmitted due to the discontinuity of the transport medium, resulting in Charge builds up, increasing the internal resistance of the device. For example, the red, green, and blue primary color quantum dots obtained by the existing process have a particle size distribution between 6-15nm, and the quantum dot film is obtained through the solution process, including spin coating, spray coating, transfer printing and other printing processes, quantum dots and quantum dots There is a noticeable gap between them, see Figure 1. At the same time, the existence of gaps inside the light-emitting layer leads to more defect states at the interface, which easily captures carriers and produces non-radiative recombination, resulting in poor optoelectronic performance of the device.

technical problem

It can be seen that how to solve the problem of carrier transport difficulties caused by quantum dot gaps in the light-emitting layer of QLED devices and the problem of trapping carriers by defects at the interface, in order to meet the needs of commercial applications for high efficiency and reliability of QLED devices, is currently a problem that needs to be overcome. one of the main problems.

Therefore, it is urgent to provide a quantum dot light-emitting layer and a quantum dot light-emitting diode device that can solve the quantum dot gap in the light-emitting layer of the QLED device, so as to avoid the problems of difficult carrier transport and carrier capture by defects at the interface.

technical solution

In view of this, the present application provides a quantum dot light-emitting layer, a preparation method of the quantum dot light-emitting layer and a quantum dot light-emitting diode device, which can solve the problem of carrier transport difficulties caused by quantum dot gaps in the light-emitting layer of QLED devices and defect capture at the interface The problem of carriers can solve the resulting problems of low current efficiency and poor stability of QLED devices, so as to meet the needs of commercial applications for high efficiency and reliability of QLED devices.

In a first aspect, the present application provides a quantum dot light-emitting layer, the quantum dot light-emitting layer includes a quantum dot material and a host material, the quantum dot material includes a first quantum dot, and the host material is filled in the first in the gaps between the quantum dots;

Wherein, the first quantum dot is a core-shell quantum dot, including a core layer and a shell layer; the bandgap width of the host material is greater than or equal to the bandgap width of the shell material of the first quantum dot.

Optionally, the difference between the bandgap width of the host material and the bandgap width of the outermost shell layer material of the first quantum dot is less than or equal to 0.8eV.

Optionally, the mass ratio of the first quantum dots to the host material is 100:5-20.

Optionally, the quantum dot material further includes second quantum dots, and the bandgap width of the second quantum dots is greater than or equal to the bandgap width of the outermost shell layer material of the first quantum dots.

Optionally, the lattice mismatch between the host material and the shell material of the first quantum dot is less than or equal to 5%;

The lattice mismatch between the host material and the second quantum dots is less than or equal to 5%.

Optionally, the mass ratio of the first quantum dots to the second quantum dots is 100:1-15; and, the total mass of the second quantum dots and the host material is equal to that of the first quantum dots The mass ratio is 5% to 20%.

Optionally, the particle size of the second quantum dots is 2-5 nm;

The material of the second quantum dot is selected from one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP.

Optionally, the first quantum dot is a Type I core-shell quantum dot;

The core layer material of the first quantum dot is selected from CdSe, CdS, CdTe, CdSeTe, CdZnS, PbSe, ZnTe, CdSeS, PbS, PbTe, HgS, HgSe, HgTe, GaP, GaAs, InP, InAs, InZnP and InGaP a kind of

The shell material of the first quantum dot is selected from one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP.

Optionally, the host material is a chalcogenide material; the host material is selected from one of cadmium sulfide, zinc sulfide, indium sulfide, lead sulfide and gallium sulfide.

In a second aspect, the present application provides a method for preparing a quantum dot luminescent layer, comprising the following steps:

Step 1, using quantum dot materials to prepare a quantum dot light-emitting layer film;

Step 2: Filling the host material into the gaps between the quantum dots in the quantum dot light-emitting layer film by using a continuous ion layer adsorption reaction method to obtain the quantum dot light-emitting layer.

Optionally, the quantum dot material includes at least one of first quantum dots or second quantum dots; for the quantum dot material including the first quantum dots and the second quantum dots, the first quantum dots The bandgap width of the second quantum dot is greater than or equal to the bandgap width of the outermost shell material of the first quantum dot;

The first quantum dot is a Type I core-shell quantum dot; the core layer material of the first quantum dot is selected from CdSe, CdS, CdTe, CdSeTe, CdZnS, PbSe, ZnTe, CdSeS, PbS, PbTe, HgS, HgSe , HgTe, GaP, GaAs, InP, InAs, InZnP and InGaP; the shell material of the first quantum dot is selected from CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS , one of PbSeS, InZnP and InGaP;

The particle diameter of the second quantum dot is 2-5nm; the material of the second quantum dot is selected from CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP kind of.

Optionally, the host material is a chalcogenide material, and the bandgap width of the host material is greater than or equal to the bandgap width of the shell material of the first quantum dot;

The difference between the bandgap width of the host material and the bandgap width of the outermost shell material of the first quantum dot is less than or equal to 0.8eV;

The lattice mismatch between the host material and the shell material of the first quantum dot is less than or equal to 5%.

Optionally, the step of preparing the quantum dot light-emitting layer by the continuous ion layer adsorption reaction method includes: continuously soaking the quantum dot light-emitting layer film after annealing in the alcohol phase solution of the metal cation precursor and the alcohol of the sulfur precursor phase solution; cycle through the above steps of soaking.

Optionally, the step of preparing the quantum dot light-emitting layer by the continuous ion layer adsorption reaction method comprises:

Soak the quantum dot light-emitting layer film in the alcohol phase solution of the metal cation precursor for 30s to 1min, rinse with an alcohol reagent; then soak in the alcohol phase solution of the sulfur precursor for 30s to 1min, and wash with an alcohol reagent;

The above steps are repeated 2 to 10 times to fill the gaps of the quantum dot light-emitting layer with the host material, and then anneal at 100 to 150° C. for 1 to 15 minutes to remove residual alcohol solvent.

Optionally, the metal cation precursors include metal cations of at least one of Cd, Zn, In, Pb and Ga.

In a third aspect, the present application provides a quantum dot light-emitting diode device, including an anode, a cathode, and a quantum dot light-emitting layer disposed between the anode and the cathode, wherein the quantum dot light-emitting layer includes a quantum dot material and a host material, the quantum dot material includes a first quantum dot, and the host material is filled in the gap between the first quantum dots; the first quantum dot is a core-shell quantum dot, including a core layer and a shell layer; the bandgap width of the host material is greater than or equal to the bandgap width of the shell material of the first quantum dot;

Alternatively, the quantum dot luminescent layer is prepared by the following preparation method:

The particle diameter of the second quantum dot is 2-5nm; the material of the second quantum dot is selected from CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP a kind of

Optionally, the core layer material of the first quantum dot is selected from CdSe, the shell material of the first quantum dot is selected from CdS, the first quantum dot is a red quantum dot, and the first quantum dot The particle size is 14nm, and the host material is CdS.

Optionally, the quantum dot light emitting diode device further includes a hole injection layer, a hole transport layer and an electron transport layer, the hole transport layer is arranged between the anode and the quantum dot light emitting layer, the The hole injection layer is arranged between the anode and the hole transport layer, and the electron transport layer is arranged between the cathode and the quantum dot light emitting layer.

Optionally, the material of the hole injection layer is selected from one or more of PEDOT:PSS, nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide or copper oxide;

The material of the hole transport layer is selected from one or more of PVK, Poly-TPD, CBP, TCTA or TFB;

The material of the electron transport layer is selected from one or more of n-type ZnO, TiO ₂ , SnO, Ta ₂ O ₃ , AlZnO, ZnSnO, InSnO, Alq ₃ , Ca, Ba, CsF, LiF or CsCO ₃ ;

The material of the anode is selected from one or more of indium tin oxide, fluorine-doped tin oxide, indium zinc oxide, graphene or carbon nanotubes;

The material of the cathode is selected from one or more of Al, Ca, Ba or Ag.

Beneficial effect

The quantum dot light-emitting layer of the present application fills the gap of the quantum dot light-emitting layer through the host material, so as to obtain the continuity of the carrier transport process in the device and passivate the quantum dot surface defects to reduce the probability of carrier capture, thereby improving the device optoelectronic performance and stability.

The quantum dot luminescent layer of the present application uses the host material to fill the gap between the quantum dots and the quantum dots through the continuous ion layer adsorption reaction method (SILAR), effectively eliminating the gaps between the quantum dots, so that the obtained quantum dot luminescent layer can Guarantee the uninterrupted transport of carriers in the continuous phase. At the same time, the filled host material passivates the surface of quantum dots, reduces the possibility of interface defects trapping carriers, and reduces non-radiative recombination, thereby improving the carrier transport process in the device and reducing internal defects in the light-emitting layer, further improving the optoelectronics of the device. performance and stability.

The QLED device obtained in the present application has excellent current efficiency and stability, and meets the requirements of commercial applications for high efficiency and reliability of the QLED device.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is a schematic diagram of quantum dot stacking in the light-emitting layer of a comparative device provided by the present application;

Fig. 2 is a schematic diagram 1 of quantum dot stacking in the quantum dot light-emitting layer of the device provided by the embodiment of the present application;

Fig. 3 is a second schematic diagram of quantum dot stacking in the quantum dot light-emitting layer of the device provided by the embodiment of the present application;

Fig. 4 is a schematic structural diagram of a quantum dot light-emitting diode device provided in an embodiment of the present application;

5 is an electroluminescence spectrum diagram of the quantum dot light-emitting diode device provided in Example 3 of the present application;

Fig. 6 is the electroluminescent spectrogram of the quantum dot light-emitting diode device provided in Example 4 of the present application;

7 is a schematic flow diagram of a method for preparing a quantum dot light-emitting layer provided in an embodiment of the present application;

Fig. 8 is a schematic flow chart of preparing a quantum dot light-emitting layer by using the continuous ion layer adsorption reaction method (SILAR) provided by the embodiment of the present application.

Embodiment of this application

The following will clearly and completely describe the technical solutions in the embodiments of the application with reference to the drawings in the embodiments of the application. Apparently, the described embodiments are only some of the embodiments of the application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of protection of this application.

Embodiments of the present application provide a quantum dot light-emitting layer, a preparation method thereof, and a quantum dot light-emitting diode device. Each will be described in detail below. It should be noted that the description sequence of the following embodiments is not intended to limit the preferred sequence of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used for designation only and do not impose numerical requirements or establish an order. Various embodiments of the present invention may exist in a range format; it should be understood that the description in a range format is merely for convenience and brevity, and should not be construed as an inflexible limitation on the scope of the invention; therefore, the stated ranges should be considered The description has specifically disclosed all possible subranges as well as individual values within that range. For example, a description of a range from 1 to 6 should be considered to have specifically disclosed subranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and A single number within a range, such as 1, 2, 3, 4, 5 and 6, applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range.

In this application, the term "and/or" is used to describe the relationship between associated objects, indicating that there may be three relationships, for example, "A and/or B" may indicate three situations: the first situation is that A exists alone ; The second case is the presence of A and B at the same time; the third case is the case of B alone, wherein A and B can be singular or plural respectively.

In this application, the term "at least one" means one or more, and "multiple" means two or more. The terms "at least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one (one) of a, b, or c" or "at least one (one) of a, b, and c" can be expressed as: a, b, c, a-b (that is, a and b ), a-c, b-c or a-b-c, wherein, a, b and c can be single or multiple respectively.

The inventor found in the work of studying quantum dot materials and quantum dot light-emitting diode devices that the quantum dot materials used in the light-emitting layer in the QLED device structure are generally composed of a core-shell structure with a particle size of 8-15nm. There are obvious gaps between quantum dots and quantum dots in the film. When the QLED device is working, electrons and holes are injected into the wide bandgap shell layer in the quantum dot light-emitting layer structure through the cathode and anode via the transport layer, and then injected into the quantum dot core by energy transfer for radiative composite light emission; among them, The gap between the quantum dots creates a discontinuous carrier transport channel, which increases the charge injection barrier. At the same time, the existence of the gap exposes the surface of the quantum dots, which is easy to generate defects to capture carriers and reduce the photoelectric conversion efficiency. In the previous research work, there was a method of filling the quantum dot gap by doping organic polymer materials in the light-emitting layer to enhance the carrier transport performance, but the quantum dots of inorganic nanomaterials and organic polymers belong to different phases. The surface in contact is easy to generate more defect states; at the same time, a Type I heterojunction needs to be formed between the organic polymer material and the quantum dot light-emitting layer, so that electrons and holes can be effectively injected into the quantum dot, and the optional There are fewer types of organic polymers. In addition, by orderly arranging quantum dots with uniform size to reduce the excessive gap caused by uneven size, at the same time, using effective methods, such as thick shells, short-chain ligands, etc., to passivate the surface defects of quantum dots to reduce the impact of defect states on photoelectric performance. Impact. However, it still cannot effectively eliminate the adverse effects of the quantum dot light-emitting layer due to the existence of gaps.

The embodiment of the present application provides a quantum dot light-emitting layer, as shown in FIG. 2 and FIG. 3 . The quantum dot light-emitting layer includes a quantum dot material and a host material, wherein the quantum dot material includes first quantum dots, and the host material fills gaps between the first quantum dots. In addition, the first quantum dots are core-shell quantum dots, and the bandgap width of the host material is greater than or equal to the bandgap width of the shell layer material of the first quantum dots. Specifically, the host material is used to fill the gaps between the quantum dot materials. After the gaps in the quantum dot luminescent layer are filled with the host material, the gaps between the quantum dots are reduced, and the elimination of the gaps can ensure the uninterrupted transmission of carriers in the continuous phase; at the same time, the filled host material can passivate the quantum dots. The point surface reduces the possibility of interface defects trapping carriers and reduces non-radiative recombination, which in turn can improve the carrier transport process in the device and reduce internal defects in the light-emitting layer, providing a basis for improving the optoelectronic performance and stability of the device.

The particle size distribution of the red, green and blue primary color quantum dots obtained by the existing technology is between 6-15nm, and the quantum dot film is obtained through the solution process, including spin coating, spray coating, transfer printing and other printing processes, and the gap between quantum dots and quantum dots There is a clear gap, as shown in Figure 1. After filling with the host material, the gap of the quantum dot light-emitting layer is reduced, as shown in Figure 2.

Further, the host material includes a chalcogen compound material. For example, the host material may be cadmium sulfide, zinc sulfide, indium sulfide, lead sulfide, or gallium sulfide. The preparation of the host material can be obtained by a continuous ion layer adsorption reaction method.

In the present invention, the quantum dot material includes first quantum dots and/or second quantum dots.

In an embodiment, the quantum dot material is composed of first quantum dots, as shown in FIG. 2 . At this time, the mass ratio of the first quantum dots to the host material is related to the interstitial volume generated by different particle sizes of the quantum dots. For example, the mass ratio of the first quantum dots to the host material may be 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100 :13, 100:14, 100:15, 100:16, 100:17, 100:18, 100:19 or 100:20. Further, the first quantum dot is a Type I core-shell quantum dot, including a core layer and a shell layer. Further, the core layer material of the first quantum dots includes: binary, multi-element, multi-element graded alloys composed of II-VI, III-V, and IV-VI elements, and quantum dots of core-shell components. Correspondingly, the shell material of the first quantum dot is selected to form a Type I core-shell structure material with the core.

Further, the core layer material of the first quantum dot is selected from but not limited to CdSe, CdS, CdTe, CdSeTe, CdZnS, PbSe, ZnTe, CdSeS, PbS, PbTe, HgS, HgSe, HgTe, GaP, GaAs, InP, One of InAs, InZnP and InGaP. The shell layer material of the first quantum dot is selected from but not limited to one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP. It can be seen that the first quantum dot is a single-component core-shell quantum dot, that is, the core layer and the shell layer are respectively composed of a single-component quantum dot material.

Further, the bandgap width (Eg) of the host material is greater than or equal to the bandgap width (Eg) of the outermost shell material of the first quantum dot, that is, Eg(host material)-Eg(first quantum dot point-shell) ≥ 0. At this time, the first quantum dot in the light-emitting layer acts as the nucleus and the host material to form a Type I heterogeneous energy level structure, which helps the carriers to be effectively confined inside the quantum dot; at the same time, the existence of no gap ensures The continuity of the carrier transport channel. In addition, E _g (host material)-E _g (first quantum dot-shell layer)≤0.8eV can avoid the difficulty of carrier injection due to the excessive bandgap width of the host material, which will lead to an increase in the internal impedance of the device. Factors that are not conducive to the stability of the device, such as large, increased operating voltage, and Joule heat generation.

In some embodiments, the lattice mismatch between the host material and the shell material of the first quantum dot is less than or equal to 5%. If the lattice mismatch is greater than 5%, crystal defects will be generated near the growth interface due to lattice stress, which will lead to the quenching of carriers in the non-radiative recombination center and reduce the radiative recombination efficiency.

In another embodiment, the quantum dot material is composed of the first quantum dot and the second quantum dot, as shown in FIG. 3 . Further, the mass percentage of the second quantum dots in the quantum dot material is less than or equal to 20%. The mass ratio of the first quantum dots, the second quantum dots to the host material is related to the interstitial volume produced by the different particle sizes of the quantum dots. For example, the mass ratio of the first quantum dots to the second quantum dots can be 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8 , 100:9, 100:10, 100:11, 100:12, 100:13, 100:14 or 100:15; further, the total mass of the second quantum dot and the host material is the same as the first The mass ratio of a quantum dot is 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, 11:100, 12:100, 13:100, 14:100, 15:100 , 16:100, 17:100, 18:100, 19:100 or 20:100.

Further, the second quantum dot is selected from but not limited to one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP. Further, the second quantum dots are nanoparticles with a particle diameter of 2-5 nm. It can be seen that the second quantum dot is a single-component quantum dot, that is, it is composed of a single-component quantum dot material.

Further, the bandgap width (Eg) of the second quantum dot is greater than or equal to the bandgap width (Eg) of the outermost shell material of the first quantum dot, that is, Eg(second quantum dot)-Eg (first quantum dot - shell) > 0.

Further, the lattice mismatch between the host material and the second quantum dots is less than or equal to 5%.

Further, the energy level of the second quantum dot is consistent with that of the host material. Further, the lattice parameter and bandgap width of the second quantum dot material are consistent with those of the host material. For example, the selection of the second quantum dot material may be consistent with the composition of the host material. At this time, the host material may be understood as an additional shell structure of quantum dots.

In the quantum dot light-emitting layer, the quantum dots are generally stacked in a tightly connected arrangement, as shown in Figure 1; at this time, the quantum dot light-emitting layer includes the following two possible situations: ① When the distance between the centers of the quantum dot cores is > 10nm; ②When the distance between the centers of quantum dot cores is s≤10nm.

For example, when the spacing s between the centers of the luminescent nuclei of adjacent first quantum dots is less than or equal to 10 nm, there will be a relatively obvious energy resonance transfer effect (FRET), resulting in energy loss. At this time, in order to reduce the energy resonance transfer loss between quantum dots, when the quantum dot core center distance s≤10nm, increase the first quantum dot core center distance by doping the second quantum dot, as shown in Figure 3; the principle is: first The second quantum dot material serves as the added spacer particles of the first quantum dots, the S between the first quantum dots is increased to the extent that the energy resonance transfer loss is reduced, and then the gap is filled with the host material to obtain the effect of the present invention. Further, the doping control mass percentage of the second quantum dots is in the range of less than or equal to 20%, avoiding the introduction of too many second quantum dot components with a wide bandgap, which will lead to an increase in the operating voltage of the device, resulting in device function at high current density Layer material aging problem. It can be seen that the function of the second quantum dot is to increase the distance between the first quantum dot luminescent nuclei and reduce the effect of energy resonance transfer (FRET). Uniformly distributed energy level barriers, the second quantum dot selects a material with uniformly distributed components and the same energy level as the filling host.

For example, when the distance between the core centers of adjacent first quantum dots is greater than 10nm, the problem of energy resonance transfer is relatively small, and only the first quantum dots can be used as the quantum dot material, and the second quantum dots are not needed to increase the first quantum dot. Quantum dot spacing. At this time, the quantum dot light-emitting layer is prepared from the first quantum dots and the host material, as shown in FIG. 2 . At this time, the quantum dots in the light-emitting layer serve as the nucleus and the host material to form a Type I heterogeneous energy level structure, which helps the carriers to be effectively confined inside the quantum dots.

The embodiment of the present application also provides a method for preparing a quantum dot light-emitting layer, as shown in Figure 7, including the following steps:

Step 2: Fill the host material into the gap between the quantum dots in the quantum dot light-emitting layer film by using the continuous ion layer adsorption reaction method (SILAR) to obtain the quantum dot light-emitting layer.

Further, the quantum dot material includes first quantum dots and/or second quantum dots. In detail, the bandgap width of the second quantum dot is greater than or equal to the bandgap width of the outermost shell material of the first quantum dot. The first quantum dot is a Type I core-shell quantum dot. The core layer material of the first quantum dot is selected from but not limited to CdSe, CdS, CdTe, CdSeTe, CdZnS, PbSe, ZnTe, CdSeS, PbS, PbTe, HgS, HgSe, HgTe, GaP, GaAs, InP, InAs, InZnP and InGaP; the shell material of the first quantum dot is selected from but not limited to CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP any kind. The particle diameter of the second quantum dot is 2-5 nm. The material of the second quantum dot is selected from but not limited to any one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP.

Further, the host material is a chalcogen compound material, and the bandgap width of the host material is greater than or equal to the bandgap width of the shell material of the first quantum dot. The difference between the bandgap width of the host material and the bandgap width of the outermost shell material of the first quantum dot is less than or equal to 0.8eV. The lattice mismatch between the host material and the shell material of the first quantum dot is less than or equal to 5%.

Further, as shown in Figure 8, the step of preparing quantum dot luminescent layer by described adopting continuous ion layer adsorption reaction method (SILAR) comprises:

S1. Soak the annealed quantum dot light-emitting layer film in the alcohol phase solution of the metal cation precursor for 30s-1min, and then rinse the film with alcohol reagent for 30s-1min;

S2. Place the quantum dot light-emitting layer film obtained in step S1 in the alcohol phase solution of the sulfur precursor, soak for 30s-1min, and wash continuously in the alcohol reagent;

S3. Repeat steps S1 and S2 above for 2 to 10 times to ensure that the gaps in the quantum dot light-emitting layer are filled with the host material, and then anneal at 100-150° C. for 1-15 minutes to remove residual alcohol solvent.

Specifically, the metal cation precursor includes metal cations of at least one of cadmium (Cd), zinc (Zn), indium (In), lead (Pb) and gallium (Ga). The sulfur precursors are sulfur-containing salts containing metal sulfides and/or organic sulfides. For example, sodium sulfide, potassium sulfide, ammonium sulfide. After continuous immersion in the alcohol phase solution of the metal cation precursor and the alcohol phase solution of the sulfur precursor, the metal cation precursor and the sulfur precursor can react to form metal sulfides, such as cadmium sulfide, zinc sulfide, indium sulfide , lead sulfide or gallium sulfide, that is, the host material in the quantum dot light-emitting layer.

And, in the preparation method of described quantum dot light-emitting layer, adopt continuous ion layer adsorption reaction method (SILAR) circulation (repeated " soaking in the alcohol phase solution of metal cation precursor and the alcohol phase solution of sulfur precursor continuously " Step) preparing the quantum dot luminescent layer, which can realize the filling of the host material in a manner similar to the growth of the quantum dot shell layer.

When the distance between the centers of adjacent quantum dot luminescent cores is s≤10nm, at this time, when preparing the quantum dot luminescent layer, the second quantum dots are mixed with the first quantum dots in a certain proportion, and the second quantum dots are distributed in an approximately regular manner. The distance between the first quantum dots is increased to reduce energy loss caused by resonance transfer. When the distance between centers of quantum dot cores is greater than 10 nm, only the first quantum dot can be used as the quantum dot material to prepare the quantum dot light-emitting layer.

The embodiment of the present application also provides a quantum dot light-emitting diode device (QLED device), including an anode, a cathode, and a quantum dot light-emitting layer arranged between the anode and the cathode, and the quantum dot light-emitting layer is the aforementioned quantum dot light-emitting layer. Point glow layer.

The embodiment of the present application also provides a printed quantum dot display, including the above-mentioned quantum dot light-emitting diode.

Further, the quantum dot light emitting diode comprises an anode 1, a hole injection layer 2, a hole transport layer 3, a light emitting layer 4, an electron transport layer 5 and a cathode 6, as shown in FIG. 4 .

Further, the anode is selected from one or more of indium tin oxide, fluorine-doped tin oxide, indium zinc oxide, graphene, and carbon nanotubes; the material of the hole injection layer is PEDOT:PSS, nickel oxide, oxide One or more of molybdenum, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide, copper oxide; hole transport layer material is one or more of PVK, Poly-TPD, CBP, TCTA and TFB; quantum The dot light-emitting layer includes red, green and blue multi-component mixed quantum dot light-emitting layer; the material of the electron transport layer is n-type ZnO, TiO ₂ , SnO, Ta ₂ O ₃ , AlZnO, ZnSnO, InSnO, Alq ₃ , Ca, Ba One or more of , CsF, LiF, CsCO ₃ ; the cathode is selected from one or more of Al, Ca, Ba, Ag.

In this application, the life test of the device adopts the 128-channel life test system customized by Guangzhou New Vision Company. The system architecture is driven by a constant voltage and constant current source to test the change of voltage or current; the photodiode detector and test system are used to test the change of the brightness (photocurrent) of the QLED; the luminance meter is used to test and calibrate the brightness (photocurrent) of the QLED.

The present application has carried out several tests successively, and a part of the test results are given as a reference to further describe the invention in detail, and will be described in detail below in conjunction with specific examples.

Example 1

This embodiment provides a quantum dot light-emitting layer, which includes a quantum dot material and a host material, and the host material fills the gap between quantum dots in the quantum dot material.

The quantum dot material in the quantum dot light-emitting layer of this embodiment is red quantum dot CdSe/CdS, with a particle size of about 14nm. After spin-coating to form a film, it is continuously soaked in cadmium acetate ethanol solution and sodium sulfide ethanol solution through SILAR, and cleaned with ethanol The reaction by-products were removed, and the cycle was carried out 3 times, and finally annealed on a hot plate at 120°C for 10 minutes to remove the residual ethanol solvent, and a red quantum dot light-emitting layer film in which the quantum dot gap was filled to form cadmium sulfide was obtained. The main material of cadmium sulfide is consistent with the CdS composition of the quantum dot shell layer, and there will be no interface defects due to the problem of interface lattice matching. The reduction of the effect is also an important factor for the high performance of the device.

Example 2

The quantum dot material in the quantum dot light-emitting layer of this embodiment is blue quantum dot ZnCdSe/ZnS, with a particle size of about 8 nm. If only the blue quantum dot ZnCdSe/ZnS is used as the quantum dot material, the distance between the quantum dot central cores after stacking is less than 10nm, which will produce a significant FERT effect. In addition, when the particle size of the quantum dots is small, the specific surface area produced The larger the value, the higher the possibility of the existence of defect states. Therefore, in this embodiment, 10% by mass of zinc sulfide nanoparticles is added to the ZnCdSe/ZnS quantum dot solution, and the particle size of the zinc sulfide nanoparticles is about 4 nm.

After the quantum dot solution containing 18mg of ZnCdSe/ZnS and 2mg of ZnS per milliliter is spin-coated to form a film, the SILAR is continuously soaked in zinc acetate methanol solution and sodium sulfide methanol solution, and the reaction by-products are removed by washing with methanol. The cycle was performed 5 times, and finally annealed on a hot plate at 100°C for 15 minutes to remove the residual methanol solvent to obtain a blue quantum dot light-emitting layer film in which the quantum dot gap was filled to form zinc sulfide.

Example 3

This implementation provides a quantum dot light-emitting diode device (QLED device), and its preparation method includes the following steps:

The hole injection layer PEDOT spin-coated on the anode ITO: PSS material, annealed at 100°C for 15 minutes; then formed on the hole injection layer TFB, annealed at 100°C for 15 minutes; on the hole transport layer as the carrier Form the luminescent layer of CdSe/CdS red quantum dots (please refer to the quantum dot luminescent layer in embodiment 1), 80 ℃ of annealing 10min remove the residual solvent of luminescent layer film; The quantum dot luminescent layer film after the annealing is soaked in cadmium acetate ethanol Solution for 45s, then use ethanol to rinse the film for 1min, then soak in sodium sulfide ethanol solution for 45s, and then use ethanol to rinse the film for 1min to remove excess ions that adhere to the surface of the film and do not participate in the reaction. Cycle 3 times to obtain the main body filled with zinc sulfide The material is a red light-emitting layer thin film; on the light-emitting layer, an ethanol solution containing ZnO is spin-coated to obtain an electron transport layer; finally, an electroluminescent device is formed by evaporating an Ag cathode.

The electroluminescence spectrum analysis is performed on the quantum dot light-emitting diode device of this embodiment, as shown in FIG. 5 .

Example 4

The hole injection layer PEDOT spin-coated on the anode ITO: PSS material, annealed at 100°C for 15 minutes; then formed on the hole injection layer PVK hole transport layer, annealed at 100°C for 15 minutes; on the hole transport layer as the carrier Form the luminescent layer of the ZnCdSe/ZnS blue quantum dot containing 10% mass percentage ZnS (please refer to the quantum dot luminescent layer in embodiment 2), 80 ℃ of annealing 10min remove the solvent that luminescent layer thin film remains; The quantum dot after annealing The luminescent layer film was soaked in zinc acetate methanol solution for 30s, then rinsed with methanol for 1min, then soaked in sodium sulfide methanol solution for 30s, and rinsed with methanol for 1min to remove excess ions that did not participate in the reaction adhering to the surface of the film, and cycled 5 times to obtain a blue light-emitting layer film filled with zinc sulfide host material; spin-coat an ethanol solution containing ZnMgO on the light-emitting layer to obtain an electron transport layer; finally, evaporate an Al cathode to package and form an electroluminescent device.

The electroluminescence spectrum analysis is performed on the quantum dot light-emitting diode device of this embodiment, as shown in FIG. 6 .

Comparative example 1

The quantum dot light-emitting diode device of Comparative Example 1 is substantially the same as that of Example 1, except that the light-emitting layer is CdSe/CdS quantum dots. The structure of the quantum dot light emitting layer in the quantum dot light emitting diode device can be referred to as shown in FIG. 1 .

Comparative example 2

The quantum dot light-emitting diode device of Comparative Example 2 is substantially the same as that of Example 2, except that the light-emitting layer is ZnCdSe/ZnS quantum dots. The structure of the quantum dot light emitting layer in the quantum dot light emitting diode device can be referred to as shown in FIG. 1 .

Test example 1

The photoelectric properties and lifetimes of the quantum dot light-emitting diode devices obtained in Example 3, Example 4, Comparative Example 1, and Comparative Example 2 were tested. The test results are shown in Table 1, and the device is recorded.

The light-emitting diode device test data that the embodiment of table 1 and comparative example prepare

According to the data in Table 1, it can be concluded that:

The electroluminescence peak position of the quantum dot light-emitting diode device prepared in Example 3 is 625nm, the half-peak width is 25nm, the external quantum efficiency (EQE) is 19.5%, and the lifetime (T ₉₅ @1000nit) is 2300h. At the same time, the turn-on voltage (V _T ) of the device was lowered by 0.2V compared with the device of Comparative Example 1.

The electroluminescence peak position of the quantum dot light-emitting diode device prepared in Example 4 is 472nm, the half-peak width is 22nm, the external quantum efficiency (EQE) is 17%, and the lifetime (T95@1000nit) is 150h. Because the blue quantum dots have a larger band gap, the turn-on voltage of the blue quantum dot light-emitting diode device is higher. After the light-emitting layer is processed by the scheme of the present invention, the turn-on voltage (VT) is reduced by 0.4 compared with the comparative example. V, that is, the quantum dot light-emitting diode device has lower resistance and better conductivity.

In the quantum dot light-emitting diode device in the comparative example, the external quantum efficiency (EQE) and lifetime (T95@1000nit) of the obtained quantum dot light-emitting diode device are lower than those of the luminescent The layer fills the device properties of the host material. It can be seen that the quantum dot light-emitting diode device of the comparative example has more unpassivated defects on the surface of the quantum dots in the light-emitting layer and the unfilled gap between the quantum dots and the quantum dots, resulting in a relatively low charge transmission ability between the quantum dots. At the same time, the FRET generated between adjacent quantum dots leads to the loss of part of the energy, resulting in poor photoelectric performance of the comparative devices.

In summary, the quantum dot light-emitting layer of the present application eliminates the gap between quantum dots, thereby ensuring the uninterrupted transport of carriers in the continuous phase, and solves the problem of carrier transport difficulties and problems caused by the gap between quantum dots in the light-emitting layer of QLED devices. The problem of trapping carriers by defects at the interface; in turn, the current efficiency and stability of QLED devices can be improved to meet the needs of commercial applications for high efficiency and reliability of QLED devices.

This application uses the SILAR method (continuous ionic layer adsorption reaction method) to fill the gap of the quantum dot light-emitting layer with a wide-bandgap inorganic semiconductor as the main material to ensure the uninterrupted and continuous transmission of carriers inside the quantum dot light-emitting layer. At the same time, the lattice mismatch between the selected host material and the quantum dot shell is less than or equal to 5%, and the defect state density at the interface is effectively passivated after filling, reducing the possibility of interface defects trapping carriers and reducing non- Radiative recombination, in order to improve the carrier transport process in the device and reduce the internal defects of the light-emitting layer, improve the photoelectric performance and stability of the device.

The light-emitting layer in the QLED device is made of the first quantum dots with a Type I core-shell structure. The role of the shell layer is to passivate the surface defect states of the quantum dot core and improve the fluorescence yield of the quantum dots. On the other hand, it will Electron and hole wavefunctions are bound within the core, avoiding quenching of nonradiative recombination centers where exciton delocalization to shell surface states is avoided.

A quantum dot light-emitting layer, a preparation method of a quantum dot light-emitting layer and a quantum dot light-emitting diode device provided in the embodiments of the present application have been introduced in detail above, and specific examples are used in this paper to illustrate the principles and implementation methods of the present application , the description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation and application scope, In summary, the contents of this specification should not be construed as limiting the application.

Claims

A quantum dot light-emitting layer, wherein the quantum dot light-emitting layer includes a quantum dot material and a host material, the quantum dot material includes first quantum dots, and the host material fills the gaps between the first quantum dots middle;

Wherein, the first quantum dot is a core-shell quantum dot, including a core layer and a shell layer; the bandgap width of the host material is greater than or equal to the bandgap width of the shell material of the first quantum dot.
The quantum dot light-emitting layer according to claim 1, wherein the difference between the bandgap width of the host material and the bandgap width of the outermost shell layer material of the first quantum dot is less than or equal to 0.8eV.
The quantum dot light-emitting layer according to claim 1 or 2, wherein the mass ratio of the first quantum dots to the host material is 100:5-20.
The quantum dot light-emitting layer according to any one of claims 1 to 3, wherein the quantum dot material further comprises second quantum dots, and the bandgap width of the second quantum dots is greater than or equal to that of the first quantum dots. Point the bandgap width of the outermost shell material.
The quantum dot light-emitting layer according to claim 4, wherein the lattice mismatch between the host material and the shell material of the first quantum dot is less than or equal to 5%;

The lattice mismatch between the host material and the second quantum dots is less than or equal to 5%.
The quantum dot light-emitting layer according to claim 4 or 5, wherein the mass ratio of the first quantum dots to the second quantum dots is 100:1-15; and, the second quantum dots and the host The ratio of the total mass of the material to the mass of the first quantum dot is 5%-20%.
The quantum dot light-emitting layer according to any one of claims 4 to 6, wherein the particle diameter of the second quantum dot is 2-5 nm;

The material of the second quantum dot is selected from one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP.
The quantum dot light-emitting layer according to any one of claims 1 to 7, wherein the first quantum dot is a Type I core-shell quantum dot;

The core layer material of the first quantum dot is selected from CdSe, CdS, CdTe, CdSeTe, CdZnS, PbSe, ZnTe, CdSeS, PbS, PbTe, HgS, HgSe, HgTe, GaP, GaAs, InP, InAs, InZnP and InGaP a kind of

The shell material of the first quantum dot is selected from one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP.
The quantum dot luminescent layer according to any one of claims 1 to 8, wherein the host material is a chalcogen compound material; the host material is selected from the group consisting of cadmium sulfide, zinc sulfide, indium sulfide, lead sulfide and gallium sulfide One of.
A method for preparing a quantum dot luminescent layer, comprising the steps of:

Step 1, using quantum dot materials to prepare quantum dot luminescent layer thin films;

Step 2: Filling the host material into the gaps between the quantum dots in the quantum dot light-emitting layer film by using a continuous ion layer adsorption reaction method to obtain the quantum dot light-emitting layer.
The preparation method according to claim 10, wherein the quantum dot material comprises at least one of the first quantum dot or the second quantum dot; for all the quantum dots comprising the first quantum dot and the second quantum dot The quantum dot material, the bandgap width of the second quantum dot is greater than or equal to the bandgap width of the outermost shell material of the first quantum dot;

The first quantum dot is a Type I core-shell quantum dot; the core layer material of the first quantum dot is selected from CdSe, CdS, CdTe, CdSeTe, CdZnS, PbSe, ZnTe, CdSeS, PbS, PbTe, HgS, HgSe , HgTe, GaP, GaAs, InP, InAs, InZnP and InGaP; the shell material of the first quantum dot is selected from CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS , one of PbSeS, InZnP and InGaP;

The particle diameter of the second quantum dot is 2-5nm; the material of the second quantum dot is selected from CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP kind of.
The preparation method according to claim 10 or 11, wherein the host material is a chalcogen compound material, and the bandgap width of the host material is greater than or equal to the bandgap width of the shell material of the first quantum dot;

The difference between the bandgap width of the host material and the bandgap width of the outermost shell material of the first quantum dot is less than or equal to 0.8eV;

The lattice mismatch between the host material and the shell material of the first quantum dot is less than or equal to 5%.
According to the preparation method described in any one of claims 10 to 12, wherein, the step of preparing the quantum dot light-emitting layer by the continuous ion layer adsorption reaction method comprises: continuously soaking the quantum dot light-emitting layer film after annealing in In the alcohol phase solution of the metal cation precursor and the alcohol phase solution of the sulfur precursor; cyclically carry out the above steps of soaking.
The preparation method according to claim 13, wherein, the step of preparing the quantum dot light-emitting layer by the continuous ion layer adsorption reaction method comprises:

Soak the quantum dot light-emitting layer film in the alcohol phase solution of the metal cation precursor for 30s to 1min, rinse with an alcohol reagent; then soak in the alcohol phase solution of the sulfur precursor for 30s to 1min, and wash with an alcohol reagent;

The above steps are repeated 2 to 10 times to fill the gaps of the quantum dot light-emitting layer with the host material, and then anneal at 100 to 150° C. for 1 to 15 minutes to remove residual alcohol solvent.
The preparation method according to claim 13 or 14, wherein the metal cation precursor comprises a metal cation of at least one of Cd, Zn, In, Pb and Ga.
A quantum dot light-emitting diode device, comprising an anode, a cathode, and a quantum dot light-emitting layer arranged between the anode and the cathode, wherein the quantum dot light-emitting layer includes a quantum dot material and a host material, and the quantum dot The material includes a first quantum dot, the host material is filled in the gap between the first quantum dots; the first quantum dot is a core-shell quantum dot, including a core layer and a shell layer; the band of the host material The gap width is greater than or equal to the band gap width of the shell material of the first quantum dot;

Alternatively, the quantum dot luminescent layer is prepared by the following preparation method:

Step 1, using quantum dot materials to prepare a quantum dot light-emitting layer film;

Step 2: Filling the host material into the gaps between the quantum dots in the quantum dot light-emitting layer film by using a continuous ion layer adsorption reaction method to obtain the quantum dot light-emitting layer.
The quantum dot light-emitting diode device according to claim 16, wherein the quantum dot material comprises at least one of a first quantum dot or a second quantum dot; The quantum dot material of dots, the bandgap width of the second quantum dot is greater than or equal to the bandgap width of the outermost shell material of the first quantum dot;

The first quantum dot is a Type I core-shell quantum dot; the core layer material of the first quantum dot is selected from CdSe, CdS, CdTe, CdSeTe, CdZnS, PbSe, ZnTe, CdSeS, PbS, PbTe, HgS, HgSe , HgTe, GaP, GaAs, InP, InAs, InZnP and InGaP; the shell material of the first quantum dot is selected from CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS , one of PbSeS, InZnP and InGaP;

The particle diameter of the second quantum dot is 2-5nm; the material of the second quantum dot is selected from CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS, ZnS, PbS, PbSeS, InZnP and InGaP a kind of

The difference between the bandgap width of the host material and the bandgap width of the outermost shell material of the first quantum dot is less than or equal to 0.8eV;

The lattice mismatch between the host material and the shell material of the first quantum dot is less than or equal to 5%.
The quantum dot light-emitting diode device according to claim 16 or 17, wherein the core material of the first quantum dot is selected from CdSe, the shell material of the first quantum dot is selected from CdS, and the first quantum dot is selected from CdS. The dots are red quantum dots, the particle size of the first quantum dots is 14nm, and the host material is CdS.
The quantum dot light emitting diode device according to any one of claims 16 to 18, wherein the quantum dot light emitting diode device further comprises a hole injection layer, a hole transport layer and an electron transport layer, and the hole transport layer It is arranged between the anode and the quantum dot light-emitting layer, the hole injection layer is arranged between the anode and the hole transport layer, and the electron transport layer is arranged between the cathode and the quantum dot Dot between glowing layers.
The quantum dot light-emitting diode device according to claim 19, wherein the material of the hole injection layer is selected from PEDOT:PSS, nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide or copper oxide one or more of

The material of the hole transport layer is selected from one or more of PVK, Poly-TPD, CBP, TCTA or TFB;

The material of the electron transport layer is selected from one or more of n-type ZnO, TiO 2 , SnO, Ta 2 O 3 , AlZnO, ZnSnO, InSnO, Alq 3 , Ca, Ba, CsF, LiF or CsCO 3 ;

The material of the anode is selected from one or more of indium tin oxide, fluorine-doped tin oxide, indium zinc oxide, graphene or carbon nanotubes;

The material of the cathode is selected from one or more of Al, Ca, Ba or Ag.