Organic light emitting diode, display substrate and display device

Abstract

An organic light emitting diode is provided, the organic light emitting diode including: an anode; a first light emitting unit on the anode; the charge generation unit is located on the side, away from the anode, of the first light emitting unit, and the charge generation unit contains a metal elementary substance doping agent; the second light-emitting unit is positioned on one side, far away from the anode, of the charge generation unit; the cathode is positioned on one side, far away from the anode, of the second light-emitting unit; wherein an interface function layer is further arranged between the charge generation unit and the first light-emitting unit, the material of the interface function layer comprises an auxiliary electron transport material, and the auxiliary electron transport material has the capability of forming coordinate bonds with metal ions from the metal elementary substance dopant.

Description

Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to an organic light emitting diode, a display substrate and a display device. Background Art

[0002] Organic Light-Emitting Diode (OLED) has been widely used in mobile terminals such as mobile phones and watches in recent years due to its advantages of high contrast, self-luminescence, lightness, and foldability. At the same time, the short life of OLED limits its popularity in medium and large-sized, in-vehicle displays and other fields. Stacked OLED devices double the current efficiency by connecting two or more OLEDs in series through a charge generation unit, which can meet the needs of medium and large-sized OLED displays for high brightness and long life devices. Stacked OLED devices contain multiple independent light-emitting units, and adjacent light-emitting units are connected in series through a charge generation unit. In stacked OLED devices, how to set up the structure to improve the performance of stacked OLED devices is one of the topics that display product researchers and developers are concerned about.

[0003] The above information disclosed in this section is only for understanding the background of the inventive concept of the present disclosure and therefore the above information may contain information that does not constitute the prior art. Summary of the invention

[0004] In one aspect, an organic light emitting diode is provided, comprising:

[0005] anode;

[0006] A first light emitting unit, located on the anode;

[0007] A charge generation unit, located at a side of the first light-emitting unit away from the anode, wherein the charge generation unit contains a metal element dopant;

[0008] A second light emitting unit is located on a side of the charge generating unit away from the anode; and

[0009] a cathode, located at a side of the second light emitting unit away from the anode;

[0010] Among them, an interface functional layer is also arranged between the charge generating unit and the first light-emitting unit, and the material of the interface functional layer includes an auxiliary electron transport material, and the auxiliary electron transport material has the ability to form coordination bonds with metal ions from the metal element dopant.

[0011] According to some exemplary embodiments, the auxiliary electron transport material includes a coordination functional group, and the coordination functional group includes at least one of a six-membered nitrogen-containing heterocycle, a five-membered nitrogen-containing heterocycle, and a carboxylic anhydride group.

[0012] According to some exemplary embodiments, the coordination functional group includes at least one of the following structures:

[0013]

[0014] According to some exemplary embodiments, the auxiliary electron transport material includes at least two coordination functional groups.

[0015] According to some exemplary embodiments, the auxiliary electron transport material includes at least one of 4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, 1,4,5,8-naphthalenetetracarboxylic anhydride and perylenetetracarboxylic dianhydride.

[0016] According to some exemplary embodiments, the material of the interface functional layer further includes alkali metal halide.

[0017] According to some exemplary embodiments, in the interface functional layer, the mass percentage of the alkali metal halide is 10 wt %-50 wt %.

[0018] According to some exemplary embodiments, the alkali metal halide includes at least one of lithium fluoride, lithium chloride, lithium bromide, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, and potassium iodide.

[0019] According to some exemplary embodiments, the charge generation unit includes an N-type charge generation layer located on a side of the interface functional layer away from the anode and a side of the N-type charge generation layer away from the anode, and the thickness of the interface functional layer is less than the thickness of the N-type charge generation layer.

[0020] According to some exemplary embodiments, the thickness of the interface functional layer is 2nm-5nm.

[0021] According to some exemplary embodiments, the N-type charge generation layer includes a host electron transport material and the metal element dopant, and the host electron transport material and the auxiliary electron transport material include the same material.

[0022] According to some exemplary embodiments, the material of the interface functional layer does not include a metal element.

[0023] According to some exemplary embodiments, the first light-emitting unit includes a first hole transport layer located on the anode, a first light-emitting layer located on a side of the first hole transport layer away from the anode, and a first electron transport layer located between the first light-emitting layer and the interface functional layer; and

[0024] The first electron transport layer includes a first electron transport material, and an absolute value of a lowest unoccupied molecular orbital energy level of the first electron transport material is greater than or equal to an absolute value of a lowest unoccupied molecular orbital energy level of the auxiliary electron transport material.

[0025] According to some exemplary embodiments, a difference between a lowest unoccupied molecular orbital energy level of the first electron transport material and a lowest unoccupied molecular orbital energy level of the auxiliary electron transport material is less than or equal to 0.2 eV.

[0026] In another aspect, a display substrate is provided, comprising the organic light emitting diode as described in any one of the above items.

[0027] In yet another aspect, a display device is provided, comprising the display substrate as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other objects and advantages of the present disclosure will be apparent from the following description of the present disclosure with reference to the accompanying drawings, and will help to have a comprehensive understanding of the present disclosure.

[0029] Figure 1 The cross-sectional view of a stacked organic light emitting diode in the related art is schematically shown.

[0030] Figure 2 Schematically shows Figure 1 Schematic diagram of the working principle of the charge generation unit in .

[0031] Figure 3 A cross-sectional schematic diagram of an organic light emitting diode according to some embodiments of the present disclosure is schematically shown.

[0032] Figure 4 A cross-sectional view of a display substrate according to some embodiments of the present disclosure is schematically shown.

[0033] It should be noted that, for the sake of clarity, in the drawings used to describe the embodiments of the present disclosure, the sizes of layers, structures or regions may be enlarged or reduced, that is, these drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0034] In the following description, for the purpose of explanation, many specific details are set forth to provide a comprehensive understanding of various exemplary embodiments. However, it is apparent that various exemplary embodiments may be implemented without these specific details or with one or more equivalent arrangements. In other cases, well-known structures and devices are shown in block diagram form to avoid making various exemplary embodiments unnecessarily obscure. In addition, various exemplary embodiments may be different, but not necessarily exclusive. For example, the specific shape, configuration, and characteristics of an exemplary embodiment may be used or implemented in another exemplary embodiment without departing from the inventive concept.

[0035] In the accompanying drawings, the size and relative size of the elements may be exaggerated for the purpose of clarity and / or description. Thus, the size and relative size of the individual elements are not necessarily limited to the size and relative size shown in the drawings. When the exemplary embodiments may be implemented differently, the specific process sequence may be performed differently from the described sequence. For example, two processes described in succession may be performed substantially simultaneously or in an order opposite to the described sequence. In addition, the same reference numerals represent the same elements.

[0036] When an element is described as "on" another element, "connected to" another element or "coupled to" another element, the element may be directly on another element, directly connected to another element or directly coupled to another element, or there may be an intermediate element. However, when an element is described as "directly on" another element, "directly connected to" another element or "directly coupled to" another element, there is no intermediate element. Other terms and / or expressions used to describe the relationship between elements should be interpreted in a similar manner, for example, "between..." versus "directly between...", "adjacent" versus "directly adjacent" or "on..." versus "directly on...", etc. In addition, the term "connection" may refer to physical connection, electrical connection, communication connection and / or fluid connection. In addition, the X-axis, Y-axis and Z-axis are not limited to the three axes of the rectangular coordinate system, and can be interpreted in a broader sense. For example, the X-axis, Y-axis and Z-axis may be perpendicular to each other, or may represent different directions that are not perpendicular to each other. For the purpose of this disclosure, "at least one of X, Y, and Z" and "at least one selected from the group consisting of X, Y, and Z" may be interpreted as only X, only Y, only Z, or any combination of two or more of X, Y, and Z such as XYZ, XY, YZ, and XZ. As used herein, the term "and / or" includes any and all combinations of one or more of the listed associated items.

[0037] It should be understood that, although the terms first, second, etc. may be used herein to describe different elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiment, a first element may be named a second element, and similarly, a second element may be named a first element.

[0038] Figure 1 The cross-sectional view of a stacked organic light emitting diode in the related art is schematically shown.

[0039] Reference Figure 1 The organic light emitting diode includes an anode 10, a first light emitting unit 30 located on the anode 10, a charge generating unit 50 located on a side of the first light emitting unit 30 away from the anode 10, a second light emitting unit 40 located on a side of the first light emitting unit 30 away from the anode 10, and a cathode 20 located on a side of the second light emitting unit 40 away from the anode 10. The first light emitting unit 30 includes a first hole transport layer 31 located on the anode 10, a first light emitting layer 32 located on a side of the first hole transport layer 31 away from the anode 10, and a first electron transport layer 33 located on a side of the first light emitting layer 32 away from the anode 10. The second light emitting unit 40 includes a second hole transport layer 41 located on a side of the charge generating unit 50 away from the anode 10, a second light emitting layer 42 located on a side of the second hole transport layer 41 away from the anode 10, and a second electron transport layer 43 located on a side of the second light emitting layer 42 away from the anode 10.

[0040] The charge generating unit 50 includes an N-type charge generating layer 51 on the side close to the first light-emitting unit 30 and a P-type charge generating layer 52 on the side close to the second light-emitting unit 40. The N-type charge generating layer 51 and the P-type charge generating layer 52 are in contact with each other to form a charge generating unit 50 having charge separation and transmission functions.

[0041] The organic light emitting diode is a stacked device including two light emitting units, and the charge generating unit 50 connects the adjacent light emitting units in series to achieve separation of electrons and holes. In order to improve the charge generation and transmission capabilities of the charge generating unit 50, the material of the N-type charge generating layer 51 includes an electron transmission material doped with a metal element with higher conductivity, and the material of the P-type charge generating layer 52 includes a hole transmission material doped with a metal oxide. Since the N-type charge generating layer 51 is doped with metal elements, these metal elements have the problem of easy diffusion and difficulty in binding due to their small volume, which will lead to a reduction in the life of the organic light emitting diode, and the display device composed of the organic light emitting diode will also have the problem of lateral crosstalk.

[0042] Figure 2 Schematically shows Figure 1 Schematic diagram of the working principle of the charge generation unit in .

[0043] Reference Figure 2 After the P-type charge generation layer 52 and the N-type charge generation layer 51 are combined, since the free electrons in the N region (the region where the N-type charge generation layer 51 is located) are majority carriers, and the holes in the P region (the region where the P-type charge generation layer 52 is located) are majority carriers, a concentration difference between electrons and holes appears at their junction. Due to the concentration difference between free electrons and holes, some electrons will diffuse from the N region to the P region, and some holes will diffuse from the P region to the N region. As a result of the diffusion, the side of the P region close to the N region loses holes, leaving negatively charged impurity ions, and the side of the N region close to the P region loses electrons, leaving positively charged impurity ions, thereby forming a space charge region at the junction of the P region and the N region to block the diffusion movement. When an external bias is applied, the dipole separation is caused at the interface between the P region and the N region, and the electrons on the highest occupied molecular orbital (HOMO) of the P-type semiconductor material in the P-type charge generation layer 52 are injected into the lowest unoccupied molecular orbital (LUMO) of the N-type semiconductor material in the N-type charge generation layer 51 through the tunneling effect of the PN junction depletion layer, thereby generating a charge generation effect.

[0044] Without relying on any theory, the inventor unexpectedly found that in the charge generation unit structure of the above structure, if the N-type charge generation layer 51 contains a metal element as a dopant, based on the N-type doping mechanism of metal coordination activation, the doped metal element in the N-type charge generation layer 51 will coordinate with the electron transport material as the main material, forming a metal complex during the coordination process, and may release free electrons and part of the metal ions to form free metal ions. These free metal ions will move to adjacent film layers (such as including) under the drive of an external electric field. Figure 1 The first electron transport layer 33 shown in the figure diffuses, causing the molecular structure of the adjacent film layer material to be destroyed, making the adjacent film layer ineffective, which in turn leads to a decrease in the luminous efficiency and life of the organic light-emitting diode. At the same time, in the display device composed of the organic light-emitting diode, the presence of these free metal ions increases the conductivity of the common film layer of multiple organic light-emitting diodes, reduces the lateral resistance, and exacerbates the lateral crosstalk problem between adjacent organic light-emitting diodes.

[0045] The metal element dopant suitable for implementing the embodiments of the present disclosure is any metal element suitable for the N-type doping mechanism based on metal coordination activation. Preferred examples thereof include, but are not limited to, active metals with relatively high electrical conductivity, such as lithium, magnesium, ytterbium, and silver.

[0046] Figure 3 A cross-sectional schematic diagram of an organic light emitting diode according to some embodiments of the present disclosure is schematically shown.

[0047] Reference Figure 3 The organic light emitting diode includes an anode 10, a first light emitting unit 30 located on the anode 10, a charge generating unit 50 located on a side of the first light emitting unit 30 away from the anode 10, a second light emitting unit 40 located on a side of the first light emitting unit 30 away from the anode 10, and a cathode 20 located on a side of the second light emitting unit 40 away from the anode 10. The first light emitting unit 30 includes a first hole transport layer 31 located on the anode 10, a first light emitting layer 32 located on a side of the first hole transport layer 31 away from the anode 10, and a first electron transport layer 33 located on a side of the first light emitting layer 32 away from the anode 10. The second light emitting unit 40 includes a second hole transport layer 41 located on a side of the charge generating unit 50 away from the anode 10, a second light emitting layer 42 located on a side of the second hole transport layer 41 away from the anode 10, and a second electron transport layer 43 located on a side of the second light emitting layer 42 away from the anode 10.

[0048] The charge generation unit 50 includes an N-type charge generation layer 51 on the side close to the first light-emitting unit 30 and a P-type charge generation layer 52 on the side close to the second light-emitting unit 40, and the N-type charge generation layer 51 has a metal element dopant. In addition, an interface functional layer 60 is further provided between the charge generation unit 50 and the first light-emitting unit 30, and the material of the interface functional layer 60 includes an auxiliary electron transport material, and the auxiliary electron transport material has the ability to form a coordination bond with a metal ion from the metal element dopant.

[0049] In the organic light-emitting diode, an interface functional layer 60 is added between the charge generating unit 50 and the first light-emitting unit 30, and the interface functional layer 60 includes an auxiliary electron transport material, that is, the interface functional layer 60 can perform electron transport. On the other hand, the auxiliary electron transport material can also form a coordination bond with the metal ions from the metal element dopant, that is, when the metal ions generated in the N-type charge generating layer 51 diffuse into the interface functional layer 60, the auxiliary electron transport material in the interface functional layer 60 can form a coordination bond with the metal ions to capture and bind the metal ions, thereby preventing the free metal ions from further diffusing to the first electron transport layer 33, which is beneficial to improving the life of the organic light-emitting diode. In addition, since the diffusion movement of the free metal ions is weakened, the square resistance of the organic light-emitting diode is increased, and the lateral crosstalk problem of the display device composed of the organic light-emitting diode can also be effectively improved.

[0050] According to some exemplary embodiments, the material of the anode 10 may include a conductive metal oxide, for example, may include at least one of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO) or aluminum zinc oxide (AZO).

[0051] According to some exemplary embodiments, the material of cathode 20 may include a conductive material having a low work function, for example, may include at least one of silver (Ag), Mg, Al, platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), Li, and calcium (Ca).

[0052] According to some exemplary embodiments, the materials of the first electron transport layer 33 and the second electron transport layer 43 may include a material having good electron transport properties, and the material of the first electron transport layer 33 and the material of the second electron transport layer 43 may be the same or different.

[0053] According to some exemplary embodiments, the materials of the first hole transport layer 31 and the second hole transport layer 41 may include materials having good hole transport properties, and the materials of the first hole transport layer 31 and the second hole transport layer 41 may be the same or different.

[0054] According to some exemplary embodiments, the material of the N-type charge generation layer 51 includes a main electron transport material as a main material and a metal element dopant as a single element dopant, wherein the main electron transport material is an organic material having electron transport properties and charge generation capabilities, and the metal element dopant is an active metal with relatively high electrical conductivity, such as lithium, magnesium, ytterbium, and silver.

[0055] According to some exemplary embodiments, the thickness of the N-type charge generation layer 51 ranges from 10 nm to 20 nm.

[0056] According to some exemplary embodiments, the doping ratio of the doping material in the N-type charge generation layer 51 is 1 wt %-5 wt %.

[0057] According to some exemplary embodiments, the material of the P-type charge generation layer 52 includes an organic material with hole transport properties as a main material and a metal oxide or an organic material as a doping material, and the doping material may be molybdenum trioxide, tungsten trioxide, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanodimethyl-p-benzoquinone (F4-TCNQ) or 1,4,5,8,9,11-hexaazatriphenylhexanitrile (HAT-CN).

[0058] According to some exemplary embodiments, the thickness of the P-type charge generation layer 52 ranges from 5 nm to 10 nm.

[0059] According to some exemplary embodiments, the doping ratio of the doping material in the P-type charge generation layer 52 is 3 wt %-10 wt %.

[0060] According to some exemplary embodiments, the auxiliary electron transport material includes a coordination functional group, which is a functional group that can form a coordination bond with a metal ion from a metal element dopant, and the coordination functional group includes at least one of a six-membered nitrogen-containing heterocycle, a five-membered nitrogen-containing heterocycle, and a carboxylic anhydride group. Typically, the metal element in the N-type charge generation layer 51 may include lithium, magnesium, ytterbium, and silver, and the metal ions generated in the N-type charge generation layer 51 may include lithium ions, magnesium ions, ytterbium ions, and silver ions, etc. The inventors have found through research that the coordination functional group having the aforementioned structure can form a particularly good coordination binding effect with these metal ions (for example, including lithium ions, magnesium ions, ytterbium ions, and silver ions, etc.) generated in the N-type charge generation layer 51, while not affecting the electron transport performance. That is to say, while ensuring the electron transport capability, the interface functional layer 60 can also form a coordination bond with the metal ions from the metal element dopant to bind the free metal ions, thereby effectively slowing down the diffusion movement of the free metal ions.

[0061] It should be noted that the six-membered nitrogen-containing heterocycle should be understood as a cyclic group with 6 ring atoms, at least one ring atom in the cyclic group is a nitrogen atom, and the other ring atoms may include carbon atoms. The five-membered nitrogen-containing heterocycle should be understood as a cyclic group with 5 ring atoms, at least one ring atom in the cyclic group is a nitrogen atom, and the other ring atoms may include carbon atoms.

[0062] According to some exemplary embodiments, the coordination functional group includes at least one of the following structures:

[0063]

[0064] It should be noted that N in N and The O on the carbonyl group in the ion has an empty orbital, which can form a strong coordination bond with the lone pair of electrons in the metal ions (such as lithium ions, magnesium ions, ytterbium ions and silver ions) from the metal element dopant, thereby binding the metal ions and slowing down the diffusion movement of the free metal ions.

[0065] According to some exemplary embodiments, the auxiliary electron transport material includes at least two coordination functional groups, that is, the auxiliary electron transport material has two or more coordination functional groups in its molecular structure, which is beneficial to further enhance the ability of the auxiliary electron transport material to bind metal ions through coordination.

[0066] According to some exemplary embodiments, the auxiliary electron transport material includes at least one of 4,7-diphenyl-1,10-phenanthroline (Bphen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin), 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBI), 1,4,5,8-naphthalenetetracarboxylic anhydride (NTCDA) and perylenetetracarboxylic dianhydride (PTCDAD), and the structural formulas of the foregoing materials are shown below.

[0067]

[0068] In the auxiliary electron transport materials shown in the above structural formula, Bphen and BCP each include two TPBI includes 3 NTCDA and PTCDAD each include 2 The materials illustrated above have a specific chemical structure, which can provide a coordination space at the coordination functional group that matches the ionic radius of metal ions (such as lithium ions, magnesium ions, ytterbium ions and silver ions) from metal element dopants, so that they can form particularly stable coordination bonds with these specific metal ions to achieve a stronger coordination binding effect on free metal ions, thereby effectively weakening the diffusion movement of free metal ions. In addition, these materials have good electron transmission capabilities and will not affect the electron transmission rate.

[0069] According to some exemplary embodiments, referring to Figure 3 The material of the interface functional layer 60 also includes alkali metal halides. By doping a certain amount of alkali metal halides in the auxiliary electron transport material, the conductivity of the interface functional layer 60 can be improved, thereby improving the electron transport capacity of the interface functional layer 60. Moreover, on the basis that the interface functional layer 60 has a higher electron transport capacity, the interface functional layer 60 can be set to be slightly thicker, which is conducive to further improving the ability to bind metal ions through coordination.

[0070] According to some exemplary embodiments, the mass percentage of the alkali metal halide in the interface functional layer 60 is 10wt%-50wt%. For example, the mass percentage of the alkali metal halide can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt% or 50wt%, etc.

[0071] According to some exemplary embodiments, the alkali metal halide includes at least one of lithium fluoride, lithium chloride, lithium bromide, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, and potassium iodide.

[0072] According to some exemplary embodiments, referring to Figure 3 The thickness of the interface functional layer 60 is less than that of the N-type charge generation layer 51. The thickness of the interface functional layer 60 can be set to be slightly thinner. On the basis of ensuring that the interface functional layer 60 can bind the free metal ions through coordination, the interface functional layer 60 is not too thick to affect the migration rate of electrons from the N-type charge generation layer 51 to the first electron transport layer 33.

[0073] According to some exemplary embodiments, referring to Figure 3 The thickness of the interface functional layer 60 is 2 nm to 5 nm. For example, the thickness of the interface functional layer 60 can be 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm or 5 nm.

[0074] According to some exemplary embodiments, referring to Figure 3 The material of the interface functional layer 60 does not include a metal element, so the interface functional layer 60 itself basically does not release free metal ions.

[0075] According to some exemplary embodiments, referring to Figure 3 The main electron transport material in the N-type charge generation layer 51 and the auxiliary electron transport material in the interface functional layer 60 include the same material, so that the LUMO energy level of the N-type charge generation layer 51 is closer to the LUMO energy level of the interface functional layer 60, which is conducive to the migration of electrons from the N-type charge generation layer 51 to the interface functional layer 60.

[0076] According to some exemplary embodiments, referring to Figure 3 The first electron transport layer 33 includes a first electron transport material. The first electron transport material and the auxiliary electron transport material are the same or different. The absolute value of the lowest unoccupied molecular orbital energy level of the first electron transport material is greater than or equal to the absolute value of the lowest unoccupied molecular orbital energy level of the auxiliary electron transport material, so that the LUMO energy level of the first electron transport layer 33 is deeper than the LUMO energy level of the interface functional layer 60, so that the electrons in the interface functional layer 60 can migrate to the first transport layer.

[0077] According to some exemplary embodiments, the difference between the lowest unoccupied molecular orbital energy level of the first electron transport material and the lowest unoccupied molecular orbital energy level of the auxiliary electron transport material is less than or equal to 0.2 eV. This setting is beneficial to improving the rate at which electrons migrate from the interface functional layer 60 to the first electron transport layer 33, which is beneficial to further improving the luminous efficiency of the organic light emitting diode.

[0078] The following is further described with reference to some specific embodiments (embodiments of the present disclosure) and comparative examples.

[0079] Embodiment 1

[0080] The organic light emitting diode ① is prepared according to the following steps. The structure of the organic light emitting diode ① can be referred to Figure 3 .

[0081] The glass substrate with the indium tin oxide layer (ie, the anode 10) is ultrasonically treated in a cleaning agent, rinsed in deionized water, and dried to remove residual moisture.

[0082] A first hole transport layer 31 is formed on the side of the anode 10 away from the glass substrate by an evaporation process. The thickness of the first hole transport layer 31 is 20 nm. The material of the first hole transport layer 31 is N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB).

[0083] A first light-emitting layer 32 is formed on a side of the first hole transport layer 31 away from the anode 10 by an evaporation process. The thickness of the first light-emitting layer 32 is 20 nm. The material of the first light-emitting layer 32 includes 99 wt % of 4,4′-bis(N-carbazole)-1,1′-biphenyl (CBP) and 1 wt % of bis(4,6-difluorophenylpyridine-C2,N)(picolinate)iridium(III) (FIrpic).

[0084] A first electron transport layer 33 is formed on a side of the first light emitting layer 32 away from the anode 10 by an evaporation process. The thickness of the first electron transport layer 33 is 15 nm. The material of the first electron transport layer 33 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0085] An interface functional layer 60 is formed on a side of the first electron transport layer 33 away from the anode 10 by an evaporation process. The thickness of the interface functional layer 60 is 3 nm, and the material of the interface functional layer 60 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0086] An N-type charge generation layer 51 is formed on the side of the interface functional layer 60 away from the anode 10 by an evaporation process. The thickness of the N-type charge generation layer 51 is 18 nm. The material of the N-type charge generation layer 51 is 99 wt % of 4,7-diphenyl-1,10-phenanthroline (Bphen) and 1 wt % of ytterbium.

[0087] A P-type charge generation layer 52 is formed on the side of the N-type charge generation layer 51 away from the anode 10 by an evaporation process. The thickness of the P-type charge generation layer 52 is 9 nm. The material of the P-type charge generation layer 52 is 95 wt % of N, N′-diphenyl-N, N′-di(1-naphthyl)-1, 1′-biphenyl-4,4′-diamine (NPB) and 5 wt % of 1, 4, 5, 8, 9, 11-hexaazatriphenylhexanitrile (HAT-CN).

[0088] A second hole transport layer 41 is formed on the side of the P-type charge generation layer 52 away from the anode 10 by an evaporation process. The thickness of the second hole transport layer 41 is 30 nm. The material of the second hole transport layer 41 is N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB).

[0089] A second light-emitting layer 42 is formed on a side of the second hole transport layer 41 away from the anode 10 by an evaporation process. The thickness of the second light-emitting layer 42 is 20 nm. The material of the second light-emitting layer 42 includes 99 wt % of 4,4′-bis(N-carbazole)-1,1′-biphenyl (CBP) and 1 wt % of bis(4,6-difluorophenylpyridine-C2,N)(picolinate)iridium(III) (FIrpic).

[0090] A second electron transport layer 43 is formed on a side of the second light emitting layer 42 away from the anode 10 by an evaporation process. The thickness of the second electron transport layer 43 is 35 nm. The second electron transport layer 43 comprises 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0091] The cathode 20 is formed on the side of the second electron transport layer 43 away from the anode 10 by an evaporation process. The thickness of the cathode 20 is 13 nm. The material of the cathode 20 is a magnesium-silver alloy, and the mass ratio of magnesium to silver is 1:9.

[0092] Embodiment 2

[0093] The organic light emitting diode ② is prepared according to the following steps. The structure of the organic light emitting diode ② can be referred to Figure 3 .

[0094] The glass substrate with the indium tin oxide layer (ie, the anode 10) is ultrasonically treated in a cleaning agent, rinsed in deionized water, and dried to remove residual moisture.

[0095] A first hole transport layer 31 is formed on the side of the anode 10 away from the glass substrate by an evaporation process. The thickness of the first hole transport layer 31 is 20 nm. The material of the first hole transport layer 31 is N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB).

[0096] A first light-emitting layer 32 is formed on a side of the first hole transport layer 31 away from the anode 10 by an evaporation process. The thickness of the first light-emitting layer 32 is 20 nm. The material of the first light-emitting layer 32 includes 99 wt % of 4,4′-bis(N-carbazole)-1,1′-biphenyl (CBP) and 1 wt % of bis(4,6-difluorophenylpyridine-C2,N)(picolinate)iridium(III) (FIrpic).

[0097] A first electron transport layer 33 is formed on a side of the first light emitting layer 32 away from the anode 10 by an evaporation process. The thickness of the first electron transport layer 33 is 15 nm. The material of the first electron transport layer 33 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0098] An interface functional layer 60 is formed on the side of the first electron transport layer 33 away from the anode 10 by evaporation process. The thickness of the interface functional layer 60 is 5 nm. The material of the interface functional layer 60 is 50 wt % of 4,7-diphenyl-1,10-phenanthroline (Bphen) and 50 wt % of lithium fluoride.

[0099] An N-type charge generation layer 51 is formed on the side of the interface functional layer 60 away from the anode 10 by an evaporation process. The thickness of the N-type charge generation layer 51 is 16 nm. The material of the N-type charge generation layer 51 is 99 wt % of 4,7-diphenyl-1,10-phenanthroline (Bphen) and 1 wt % of ytterbium.

[0100] A P-type charge generation layer 52 is formed on the side of the N-type charge generation layer 51 away from the anode 10 by an evaporation process. The thickness of the P-type charge generation layer 52 is 9 nm. The material of the P-type charge generation layer 52 is 95 wt % of N, N′-diphenyl-N, N′-di(1-naphthyl)-1, 1′-biphenyl-4,4′-diamine (NPB) and 5 wt % of 1, 4, 5, 8, 9, 11-hexaazatriphenylhexanitrile (HAT-CN).

[0101] A second hole transport layer 41 is formed on the side of the P-type charge generation layer 52 away from the anode 10 by an evaporation process. The thickness of the second hole transport layer 41 is 30 nm. The material of the second hole transport layer 41 is N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB).

[0102] A second light-emitting layer 42 is formed on the side of the second hole transport layer 41 away from the anode 10 by an evaporation process. The thickness of the second light-emitting layer 42 is 20 nm. The material of the second light-emitting layer 42 includes 99 wt % of 4,4′-bis(N-carbazole)-1,1′-biphenyl (CBP) and 1 wt % of bis(4,6-difluorophenylpyridine-C2,N)(picolinate)iridium(III) (FIrpic).

[0103] A second electron transport layer 43 is formed on a side of the second light emitting layer 42 away from the anode 10 by an evaporation process. The thickness of the second electron transport layer 43 is 35 nm. The second electron transport layer 43 comprises 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0104] The cathode 20 is formed on the side of the second electron transport layer 43 away from the anode 10 by an evaporation process. The thickness of the cathode 20 is 13 nm. The material of the cathode 20 is a magnesium-silver alloy, and the mass ratio of magnesium to silver is 1:9.

[0105] Comparative Example 1

[0106] The organic light emitting diode ③ is prepared according to the following steps. The structure of the organic light emitting diode ③ can be referred to Figure 1 .

[0107] The glass substrate with the indium tin oxide layer (ie, the anode 10) is ultrasonically treated in a cleaning agent, rinsed in deionized water, and dried to remove residual moisture.

[0108] A first hole transport layer 31 is formed on the side of the anode 10 away from the glass substrate by an evaporation process. The thickness of the first hole transport layer 31 is 20 nm. The material of the first hole transport layer 31 is N, N′-diphenyl-N, N′-di(1-naphthyl)-1, 1′-biphenyl-4, 4′-diamine (NPB).

[0109] A first light-emitting layer 32 is formed on a side of the first hole transport layer 31 away from the anode 10 by an evaporation process. The thickness of the first light-emitting layer 32 is 20 nm. The material of the first light-emitting layer 32 includes 99 wt % of 4,4′-bis(N-carbazole)-1,1′-biphenyl (CBP) and 1 wt % of bis(4,6-difluorophenylpyridine-C2,N)(picolinate)iridium(III) (FIrpic).

[0110] A first electron transport layer 33 is formed on a side of the first light emitting layer 32 away from the anode 10 by an evaporation process. The thickness of the first electron transport layer 33 is 15 nm. The material of the first electron transport layer 33 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0111] An N-type charge generation layer 51 is formed on the side of the first electron transport layer 33 away from the anode 10 by an evaporation process. The thickness of the N-type charge generation layer 51 is 21 nm. The material of the N-type charge generation layer 51 is 99 wt % of 4,7-diphenyl-1,10-phenanthroline (Bphen) and 1 wt % of ytterbium.

[0112] A P-type charge generation layer 52 is formed on the side of the N-type charge generation layer 51 away from the anode 10 by an evaporation process. The thickness of the P-type charge generation layer 52 is 9 nm. The material of the P-type charge generation layer 52 is 95 wt % of N, N′-diphenyl-N, N′-di(1-naphthyl)-1, 1′-biphenyl-4,4′-diamine (NPB) and 5 wt % of 1, 4, 5, 8, 9, 11-hexaazatriphenylhexanitrile (HAT-CN).

[0113] A second hole transport layer 41 is formed on the side of the P-type charge generation layer 52 away from the anode 10 by an evaporation process. The thickness of the second hole transport layer 41 is 30 nm. The material of the second hole transport layer 41 is N,N′-diphenyl-N,N′-di(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB).

[0114] A second light-emitting layer 42 is formed on the side of the second hole transport layer 41 away from the anode 10 by an evaporation process. The thickness of the second light-emitting layer 42 is 20 nm. The material of the second light-emitting layer 42 includes 99 wt % of 4,4′-bis(N-carbazole)-1,1′-biphenyl (CBP) and 1 wt % of bis(4,6-difluorophenylpyridine-C2,N)(picolinate)iridium(III) (FIrpic).

[0115] A second electron transport layer 43 is formed on a side of the second light emitting layer 42 away from the anode 10 by an evaporation process. The thickness of the second electron transport layer 43 is 35 nm. The second electron transport layer 43 comprises 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0116] The cathode 20 is formed on the side of the second electron transport layer 43 away from the anode 10 by an evaporation process. The thickness of the cathode 20 is 13 nm. The material of the cathode 20 is a magnesium-silver alloy, and the mass ratio of magnesium to silver is 1:9.

[0117] Device performance tests were performed on the organic light emitting diode ① prepared in Example 1, the organic light emitting diode ② prepared in Example 2, and the organic light emitting diode ③ prepared in Comparative Example 1 to obtain test data of turn-on voltage, current efficiency, device life, and device square resistance. The relevant test data are summarized in Table 1, wherein the test data of the organic light emitting diode ③ was taken as the reference value 100%, and the test data of the organic light emitting diode ① and the organic light emitting diode ② were obtained respectively.

[0118] Table 1

[0119] Turn on voltage Current efficiency Device life Device square resistance Organic Light Emitting Diode① 105％ 99％ 118％ 121％ Organic Light Emitting Diode② 98％ 103％ 115％ 117％ Organic light emitting diodes③ 100％ 100％ 100％ 100％

[0120] From the data in Table 1, we can see that compared with OLED ③, the turn-on voltage of OLED ① increases by 5%, the current efficiency decreases by 1%, the device life increases by 18%, and the device resistance increases by 21%. OLED ① adds an interface functional layer between the N-type charge generation layer and the first electron transport layer. The interface functional layer can form coordination bonds with free metal ions to effectively weaken the diffusion movement of metal ions, which increases the device life of OLED ① and the device square resistance.

[0121] Compared with organic light-emitting diode ③, the turn-on voltage of organic light-emitting diode ② is reduced by 2%, the current efficiency is increased by 3%, the device life is increased by 15%, and the device resistance is increased by 17%. Organic light-emitting diode ② adds an interface functional layer between the N-type charge generation layer and the first electron transport layer. The interface functional layer can form a coordination bond with the free metal ions to effectively weaken the diffusion movement of the metal ions, which increases the device life of organic light-emitting diode ② and the device square resistance.

[0122] In addition, comparing the test data of OLED ① and OLED ②, since the interface functional layer in OLED ② is doped with lithium fluoride, the electron injection ability and electron transmission ability of the interface functional layer in OLED ② are stronger, thereby making the turn-on voltage of OLED ② lower and the current efficiency higher. Accordingly, the device life and device square resistance of OLED ② are slightly lower than those of OLED ①.

[0123] Figure 4 A cross-sectional view of a display substrate according to some embodiments of the present disclosure is schematically shown.

[0124] At least some embodiments of the present disclosure further provide a display substrate, referring to Figure 4 The display substrate includes a base substrate 1, a driving circuit layer 2 located on the base substrate 1, a plurality of organic light emitting diodes 3 located on the side of the driving circuit layer 2 away from the base substrate 1, and an encapsulation layer 4 located on the side of the plurality of organic light emitting diodes 3 away from the base substrate 1. In order to simplify the preparation process and other factors, a part of the film layer in the organic light emitting diode 3 will be formed as a common film layer, and the common film layer is a continuous film layer covering the entire surface of the display area of ​​the display substrate. Adjacent organic light emitting diodes 3 will be connected through the common film layer, so there is a risk of causing lateral crosstalk problems.

[0125] Combined with reference Figure 3 and Figure 4 , illustratively, at least one of the first hole transport layer 31 , the first electron transport layer 33 , the second hole transport layer 41 , the second electron transport layer 43 , the charge generating unit 50 and the interface functional layer 60 in the organic light emitting diode 3 is a common film layer.

[0126] The organic light emitting diode 3 in the display substrate adopts the organic light emitting diode described above. Since an interface functional layer located between the charge generating unit and the first light emitting unit is added to the organic light emitting diode, the display panel has a longer service life and can effectively avoid poor display caused by lateral crosstalk problems.

[0127] At least some embodiments of the present disclosure also provide a display device, which includes a display substrate as described above. The display device may include any device or product having a display function. For example, the display device may be a smart phone, a mobile phone, an e-book reader, a desktop computer (PC), a laptop PC, a netbook PC, a personal digital assistant (PDA), a portable multimedia player (PMP), a digital audio player, a mobile medical device, a camera, a wearable device (such as a head-mounted device, an electronic clothing, an electronic bracelet, an electronic necklace, an electronic accessory, an electronic tattoo, or a smart watch), a television, etc.

[0128] It should be understood that the display device according to some exemplary embodiments of the present disclosure has all the features and advantages of the above-mentioned display substrate, and these features and advantages can be referred to the above description of the display substrate, which will not be repeated here.

[0129] As used herein, the terms "substantially," "approximately," "approximately," and other similar terms are used as terms of approximation rather than as terms of degree, and they are intended to account for the inherent deviations in measured or calculated values ​​that would be recognized by one of ordinary skill in the art. Taking into account factors such as process fluctuations, measurement problems, and errors associated with the measurement of a particular quantity (i.e., limitations of the measurement system), "approximately" or "approximately" as used herein include the stated value and mean that the particular value is within an acceptable range of deviation as determined by one of ordinary skill in the art. For example, "approximately" can mean within one or more standard deviations, or within ±10% or ±5% of the stated value.

[0130] Although some embodiments according to the general inventive concept of the present disclosure have been illustrated and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the general inventive concept of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. An organic light emitting diode, wherein: The organic light emitting diode comprises: anode; A first light emitting unit, located on the anode; A charge generation unit, located at a side of the first light-emitting unit away from the anode, wherein the charge generation unit contains a metal element dopant; A second light emitting unit is located on a side of the charge generating unit away from the anode; and a cathode, located at a side of the second light emitting unit away from the anode; Among them, an interface functional layer is also arranged between the charge generating unit and the first light-emitting unit, and the material of the interface functional layer includes an auxiliary electron transport material, and the auxiliary electron transport material has the ability to form coordination bonds with metal ions from the metal element dopant.

2. The organic light emitting diode according to claim 1, wherein: The auxiliary electron transport material includes a coordination functional group, and the coordination functional group includes at least one of a six-membered nitrogen-containing heterocycle, a five-membered nitrogen-containing heterocycle, and a carboxylic anhydride group.

3. The organic light emitting diode according to claim 2, wherein: The coordination functional group includes at least one of the following structures:

4. The organic light emitting diode according to claim 2 or 3, wherein: The auxiliary electron transport material includes at least two coordination functional groups.

5. The organic light emitting diode according to any one of claims 2 to 4, wherein: The auxiliary electron transport material includes at least one of 4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, 1,4,5,8-naphthalenetetracarboxylic anhydride and perylenetetracarboxylic dianhydride.

6. The organic light emitting diode according to any one of claims 1 to 5, wherein: The material of the interface functional layer also includes alkali metal halides.

7. The organic light emitting diode according to claim 6, wherein: In the interface functional layer, the mass percentage of the alkali metal halide is 10wt%-50wt%.

8. The organic light emitting diode according to claim 6, wherein: The alkali metal halide includes at least one of lithium fluoride, lithium chloride, lithium bromide, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide and potassium iodide.

9. The organic light emitting diode according to any one of claims 1 to 8, wherein: The charge generation unit includes an N-type charge generation layer located on a side of the interface functional layer away from the anode and a side of the N-type charge generation layer away from the anode, and the thickness of the interface functional layer is smaller than that of the N-type charge generation layer.

10. The organic light emitting diode according to claim 9, wherein: The thickness of the interface functional layer is 2nm-5nm.

11. The organic light emitting diode according to claim 9, wherein: The N-type charge generation layer includes a main electron transport material and the metal single substance dopant, and the main electron transport material and the auxiliary electron transport material include the same material.

12. The organic light emitting diode according to claim 11, wherein: The material of the interface functional layer does not include metal elements.

13. The organic light emitting diode according to any one of claims 1 to 12, wherein: The first light-emitting unit includes a first hole transport layer located on the anode, a first light-emitting layer located on a side of the first hole transport layer away from the anode, and a first electron transport layer located between the first light-emitting layer and the interface functional layer; as well as The first electron transport layer includes a first electron transport material, and an absolute value of a lowest unoccupied molecular orbital energy level of the first electron transport material is greater than or equal to an absolute value of a lowest unoccupied molecular orbital energy level of the auxiliary electron transport material.

14. The organic light emitting diode according to claim 13, wherein: The difference between the lowest unoccupied molecular orbital energy level of the first electron transport material and the lowest unoccupied molecular orbital energy level of the auxiliary electron transport material is less than or equal to 0.2 eV.

15. A display substrate, wherein: The display substrate comprises the organic light emitting diode according to any one of claims 1 to 14.

16. A display device, wherein: The display device comprises the display substrate according to claim 15 .

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