Organic light-emitting diode, display substrate, and display device

Abstract

Provided is an organic light-emitting diode. The organic light-emitting diode comprises: an anode; a first light-emitting unit, located on the anode; a charge generation unit, located on the side of the first light-emitting unit distant from the anode, the charge generation unit containing a metal simple substance dopant; a second light-emitting unit, located on the side of the charge generation unit distant from the anode; and a cathode, located on the side of the second light-emitting unit distant from the anode. An interfacial functional layer is further provided between the charge generation unit and the first light-emitting unit, the material of the interfacial functional layer comprises an auxiliary electron transport material, and the auxiliary electron transport material has a capability of forming a coordination bond with a metal ion from the metal simple substance dopant.

Description

Organic light-emitting diodes, display substrates and display devices Technical Field

[0001] This disclosure relates to the field of display technology, and more particularly to an organic light-emitting diode, a display substrate, and a display device. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have been widely used in mobile devices such as smartphones and watches in recent years due to their advantages of high contrast, self-illumination, thinness, and foldability. However, the relatively short lifespan of OLEDs limits their widespread adoption in medium-to-large-size displays and automotive displays. Stacked OLED devices, by connecting two or more OLEDs in series through charge generation units, achieve a significant increase in current efficiency, meeting the requirements of medium-to-large-size OLED displays for high brightness and long lifespan. Stacked OLED devices contain multiple independent light-emitting units, with adjacent units connected in series through charge generation units. In stacked OLED devices, how to design the structure to improve performance is one of the key areas of focus for display product developers.

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

[0004] In one aspect, an organic light-emitting diode includes:

[0005] anode;

[0006] The first light-emitting unit is located on the anode;

[0007] A charge generating unit is located on the side of the first light-emitting unit away from the anode, and the charge generating unit contains a metallic elemental dopant;

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

[0009] The cathode is located on the side of the second light-emitting unit away from the anode;

[0010] An interface functional layer is further provided between the charge generating unit and the first light-emitting unit. The material of the interface functional layer includes an auxiliary electron transport material, which has the ability to form coordination bonds with metal ions from the metal elemental dopant.

[0011] According to some exemplary embodiments, the auxiliary electron transport material includes a coordination functional group, which 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] According to some exemplary embodiments, the auxiliary electron transport material includes at least two of the aforementioned coordination functional groups.

[0014] According to some exemplary embodiments, the auxiliary electron transport material includes at least one selected from 4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 1,4,5,8-naphthalenetetracarboxylic anhydride, and perylenetetracarboxylic dianhydride.

[0015] According to some exemplary embodiments, the material of the interface functional layer also includes alkali metal halides.

[0016] According to some exemplary embodiments, in the interface functional layer, the mass percentage of the alkali metal halide is 10wt%-50wt%.

[0017] 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.

[0018] According to some exemplary embodiments, the charge generation unit includes an N-type charge generation layer located on the side of the interface functional layer away from the anode and a side of the N-type charge generation layer away from the anode, wherein the thickness of the interface functional layer is less than the thickness of the N-type charge generation layer.

[0019] According to some exemplary embodiments, the thickness of the interface functional layer is 2nm-5nm.

[0020] According to some exemplary embodiments, the N-type charge generation layer includes a host electron transport material and the metal elemental dopant, wherein the host electron transport material and the auxiliary electron transport material comprise the same material.

[0021] According to some exemplary embodiments, the material of the interface functional layer does not include elemental metals.

[0022] 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 the 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

[0023] The first electron transport layer includes a first electron transport material, wherein 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.

[0024] 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.

[0025] In another aspect, a display substrate is provided, including an organic light-emitting diode as described in any of the preceding claims.

[0026] In another aspect, a display device is provided, comprising a display substrate as described above. Attached Figure Description

[0027] Other objects and advantages of this disclosure will become apparent from the following description of the disclosure with reference to the accompanying drawings, and will help to provide a comprehensive understanding of the disclosure.

[0028] Figure 1 schematically shows a cross-sectional view of a stacked organic light-emitting diode in the related art.

[0029] Figure 2 schematically illustrates the working principle of the charge generation unit in Figure 1.

[0030] Figure 3 schematically shows a cross-sectional view of an organic light-emitting diode according to some embodiments of the present disclosure.

[0031] Figure 4 schematically shows a cross-sectional view of a display substrate according to some embodiments of the present disclosure.

[0032] It should be noted that, for clarity, the dimensions of layers, structures, or regions in the accompanying drawings used to describe embodiments of this disclosure may be enlarged or reduced; that is, these drawings are not drawn to actual scale. Detailed Implementation

[0033] In the following description, numerous specific details are set forth for illustrative purposes to provide a comprehensive understanding of various exemplary embodiments. However, it will be apparent that various exemplary embodiments may be implemented without these specific details or with one or more equivalent arrangements. In other instances, well-known structures and apparatuses are shown in block diagram form to avoid unnecessarily obscuring the various exemplary embodiments. Furthermore, the various exemplary embodiments may be different, but not necessarily exclusive. For example, specific shapes, configurations, and characteristics of exemplary embodiments may be used or implemented in another exemplary embodiment without departing from the inventive concept.

[0034] In the accompanying drawings, the dimensions and relative dimensions of the elements may be enlarged for clarity and / or descriptive purposes. Thus, the dimensions and relative dimensions of the individual elements are not necessarily limited to those shown in the drawings. When exemplary embodiments can be implemented differently, the specific process sequence may be performed differently than the order described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of description. Furthermore, the same reference numerals denote the same elements.

[0035] When an element is described as being "on" another element, "connected to" another element, or "attached to" another element, the element may be directly on, directly connected to, or directly attached to the other element, or there may be intermediate elements present. However, when an element is described as being "directly on" another element, "directly connected to" another element, or "directly attached to" another element, there are no intermediate elements. Other terms and / or expressions used to describe relationships between elements should be interpreted in a similar manner, such as "between" versus "directly between," "adjacent" versus "directly adjacent," or "on" versus "directly on," etc. Furthermore, the term "connection" can refer to a physical connection, an electrical connection, a communication connection, and / or a fluid connection. Additionally, the X-axis, Y-axis, and Z-axis are not limited to the three axes of a Cartesian 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 purposes 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” can 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 related items.

[0036] 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 merely used to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, a first element may be named a second element, and similarly, a second element may be named a first element.

[0037] Figure 1 schematically shows a cross-sectional view of a stacked organic light-emitting diode in the related art.

[0038] Referring to FIG1, 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 the side of the first light-emitting unit 30 away from the anode 10, a second light-emitting unit 40 located on the side of the first light-emitting unit 30 away from the anode 10, and a cathode 20 located on the 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 the side of the first hole transport layer 31 away from the anode 10, and a first electron transport layer 33 located on the 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 the side of the charge-generating unit 50 away from the anode 10, a second light-emitting layer 42 located on the side of the second hole transport layer 41 away from the anode 10, and a second electron transport layer 43 located on the side of the second light-emitting layer 42 away from the anode 10.

[0039] The charge generation unit 50 includes an N-type charge generation layer 51 near the first light-emitting unit 30 and a P-type charge generation layer 52 near the second light-emitting unit 40. The N-type charge generation layer 51 and the P-type charge generation layer 52 are in contact with each other to form a charge generation unit 50 with charge separation and transmission functions.

[0040] This organic light-emitting diode (OLED) is a stacked device comprising two light-emitting units. The charge generation unit 50 connects adjacent light-emitting units in series, achieving electron and hole separation. To improve the charge generation and transport capabilities of the charge generation unit 50, the N-type charge generation layer 51 is made of an electron transport material doped with a metallic element with high conductivity, and the P-type charge generation layer 52 is made of a hole transport material doped with a metal oxide. Because the N-type charge generation layer 51 is doped with a metallic element, these elements, due to their small size, are prone to diffusion and difficult to bind, leading to a reduced lifespan for the OLED. Furthermore, display devices constructed using this OLED may experience lateral crosstalk.

[0041] Figure 2 schematically illustrates the working principle of the charge generation unit in Figure 1.

[0042] Referring to Figure 2, after the P-type charge generation layer 52 and the N-type charge generation layer 51 combine, a concentration difference between electrons and holes arises at their boundary because free electrons are the majority carriers in the N-region (the region where the N-type charge generation layer 51 is located) and holes are the majority carriers in the P-region (the region where the P-type charge generation layer 52 is located). Due to this concentration difference, some electrons diffuse from the N-region to the P-region, and some holes diffuse from the P-region to the N-region. This diffusion results in the P-region losing holes near the N-region, leaving behind negatively charged impurity ions, and the N-region losing electrons near the P-region, leaving behind positively charged impurity ions. This creates a space charge region at the boundary between the P-region and the N-region to block the diffusion process. When an external bias voltage is applied, dipole separation occurs at the interface between the P-region and the N-region. Electrons in 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.

[0043] Without relying on any theory, the inventors unexpectedly discovered that in the charge generation unit structure described above, if the N-type charge generation layer 51 contains a metallic element as a dopant, based on the N-type doping mechanism of metal coordination activation, the doped metallic element in the N-type charge generation layer 51 will coordinate with the electron transport material, which is the host material. During the coordination process, a metal complex is formed, and free electrons and some metal ions may be released, forming ionized metal ions. These ionized metal ions will diffuse into adjacent film layers (such as the first electron transport layer 33 shown in Figure 1) under the drive of an external electric field, causing the molecular structure of the adjacent film layer material to be destroyed, resulting in the failure of the adjacent film layer, which in turn leads to a decrease in the luminous efficiency and lifetime of the organic light-emitting diode. At the same time, in the display device composed of this organic light-emitting diode, the presence of these ionized 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.

[0044] Suitable elemental metal dopants for implementing embodiments of this disclosure are any elemental metals suitable for N-type doping mechanisms based on metal coordination activation. Preferred examples include, but are not limited to, active metals with high electrical conductivity, such as lithium, magnesium, ytterbium, and silver.

[0045] Figure 3 schematically shows a cross-sectional view of an organic light-emitting diode according to some embodiments of the present disclosure.

[0046] Referring to FIG3, 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 the side of the first light-emitting unit 30 away from the anode 10, a second light-emitting unit 40 located on the side of the first light-emitting unit 30 away from the anode 10, and a cathode 20 located on the 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 the side of the first hole transport layer 31 away from the anode 10, and a first electron transport layer 33 located on the 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 the side of the charge-generating unit 50 away from the anode 10, a second light-emitting layer 42 located on the side of the second hole transport layer 41 away from the anode 10, and a second electron transport layer 43 located on the side of the second light-emitting layer 42 away from the anode 10.

[0047] The charge generation unit 50 includes an N-type charge generation layer 51 near the first light-emitting unit 30 and a P-type charge generation layer 52 near the second light-emitting unit 40. The N-type charge generation layer 51 has a metal elemental dopant. Furthermore, an interface functional layer 60 is disposed between the charge generation unit 50 and the first light-emitting unit 30. The material of the interface functional layer 60 includes an auxiliary electron transport material, which has the ability to form coordination bonds with metal ions from the metal elemental dopant.

[0048] In this organic light-emitting diode (OLED), an interface functional layer 60 is added between the charge generation unit 50 and the first light-emitting unit 30. This interface functional layer 60 includes an auxiliary electron transport material, enabling electron transport. Furthermore, the auxiliary electron transport material can form coordination bonds with metal ions from the elemental metal dopant. When metal ions generated in the N-type charge generation layer 51 diffuse into the interface functional layer 60, the auxiliary electron transport material in the interface functional layer 60 can form coordination bonds with these metal ions, thereby capturing and binding them. This prevents the free metal ions from further diffusing into the first electron transport layer 33, which helps to improve the lifespan of the OLED. In addition, because the diffusion of free metal ions is weakened, the sheet resistance of the OLED increases, and the lateral crosstalk problem in the display device composed of this OLED can also be effectively improved.

[0049] According to some exemplary embodiments, the material of the anode 10 may include a conductive metal oxide, such as 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).

[0050] According to some exemplary embodiments, the material of the cathode 20 may include a conductive material with a low work function, such as 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).

[0051] According to some exemplary embodiments, the materials of the first electron transport layer 33 and the second electron transport layer 43 may include materials with good electron transport properties, and the materials of the first electron transport layer 33 and the second electron transport layer 43 may be the same or different.

[0052] According to some exemplary embodiments, the materials of the first hole transport layer 31 and the second hole transport layer 41 may include materials with good hole transport characteristics, and the materials of the first hole transport layer 31 and the second hole transport layer 41 may be the same or different.

[0053] According to some exemplary embodiments, the material of the N-type charge generation layer 51 includes a host electron transport material as the host material and a metal element dopant as the host material. The host electron transport material is an organic material with electron transport properties and charge generation capability, and the metal element dopant is an active metal with high electrical conductivity, such as lithium, magnesium, ytterbium, and silver.

[0054] According to some exemplary embodiments, the thickness of the N-type charge generation layer 51 ranges from 10 nm to 20 nm.

[0055] According to some exemplary embodiments, the doping ratio of the doped material in the N-type charge generation layer 51 is 1wt%-5wt%.

[0056] According to some exemplary embodiments, the material of the P-type charge generation layer 52 includes an organic material with hole transport characteristics as the host material and a metal oxide or organic material as a dopant material. The dopant material can 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).

[0057] According to some exemplary embodiments, the thickness of the P-type charge generation layer 52 ranges from 5 nm to 10 nm.

[0058] According to some exemplary embodiments, the doping ratio of the doped material in the P-type charge generation layer 52 is 3wt%-10wt%.

[0059] According to some exemplary embodiments, the auxiliary electron transport material includes a coordination functional group, which is a functional group capable of forming coordination bonds with metal ions from a metal element dopant. This coordination functional group includes at least one of a six-membered nitrogen-containing heterocycle, a five-membered nitrogen-containing heterocycle, or 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 correspondingly include lithium ions, magnesium ions, ytterbium ions, and silver ions. The inventors have discovered that the coordination functional group having the aforementioned structure can form particularly good coordination binding effects with these metal ions (e.g., including lithium ions, magnesium ions, ytterbium ions, and silver ions) generated in the N-type charge generation layer 51 without affecting electron transport performance. In other words, while ensuring electron transport capability, the interface functional layer 60 can also bind free metal ions by forming coordination bonds with metal ions from a metal element dopant, thereby effectively slowing down the diffusion of free metal ions.

[0060] It should be noted that a six-membered nitrogen-containing heterocycle should be understood as a cyclic group with 6 ring atoms, where at least one ring atom is a nitrogen atom, and the other ring atoms may include carbon atoms. A five-membered nitrogen-containing heterocycle should be understood as a cyclic group with 5 ring atoms, where at least one ring atom is a nitrogen atom, and the other ring atoms may include carbon atoms.

[0061] According to some exemplary embodiments, the coordination functional group includes at least one of the following structures:

[0062] It should be noted that, N in N and The oxygen atoms on the carbonyl groups have empty orbitals, which can form strong coordination bonds with the lone pairs of electrons in metal ions (such as lithium ions, magnesium ions, ytterbium ions, and silver ions) from metal element dopants, thereby binding the metal ions and slowing down the diffusion of free metal ions.

[0063] According to some exemplary embodiments, the auxiliary electron transport material includes at least two coordination functional groups, that is, the molecular structure of the auxiliary electron transport material has two or more coordination functional groups, which is beneficial to further enhance the ability of the auxiliary electron transport material to bind metal ions through coordination.

[0064] According to some exemplary embodiments, the auxiliary electron transport material includes at least one selected from 4,7-diphenyl-1,10-phenanthroline (Bphen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, copper bath), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBI), 1,4,5,8-naphthalenetetracarboxylic anhydride (NTCDA), and perylenetetracarboxylic dianhydride (PTCDAD), the structural formula of which is shown below.

[0065] In the auxiliary electron transport materials illustrated 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 specific chemical structures that provide coordination spaces at their coordination functional groups that match the ionic radii of metal ions (such as lithium, magnesium, ytterbium, and silver ions) from elemental metal dopants. This allows them to form particularly stable coordination bonds with these specific metal ions, thereby achieving a strong coordination binding effect on free metal ions. This effectively reduces the diffusion of free metal ions, and these materials all have good electron transport capabilities without affecting the electron transport rate.

[0066] According to some exemplary embodiments, referring to FIG3, the material of the interface functional layer 60 further includes alkali metal halides. By doping a certain amount of alkali metal halides into the auxiliary electron transport material, the conductivity of the interface functional layer 60 can be improved, thereby enhancing the electron transport capability of the interface functional layer 60. Furthermore, based on the higher electron transport capability of the interface functional layer 60, the interface functional layer 60 can be made slightly thicker, which is beneficial to further enhance the ability to bind metal ions through coordination.

[0067] According to some exemplary embodiments, in the interface functional layer 60, the mass percentage content of alkali metal halides is 10wt%-50wt%. For example, the mass percentage content of alkali metal halides can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%, etc.

[0068] 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.

[0069] According to some exemplary embodiments, referring to FIG3, the thickness of the interface functional layer 60 is less than the thickness of the N-type charge generation layer 51. The thickness of the interface functional layer 60 can be set to be slightly thinner. While ensuring that the interface functional layer 60 can bind free metal ions through coordination, it avoids affecting the rate of electron migration from the N-type charge generation layer 51 to the first electron transport layer 33 due to the interface functional layer 60 being too thick.

[0070] According to some exemplary embodiments, referring to FIG3, the thickness of the interface functional layer 60 is 2nm-5nm. For example, the thickness of the interface functional layer 60 can be 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, or 5nm, etc.

[0071] According to some exemplary embodiments, referring to FIG3, the material of the interface functional layer 60 does not contain elemental metals, so the interface functional layer 60 itself will not release free metal ions.

[0072] According to some exemplary embodiments, referring to FIG3, 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, thereby making the LUMO energy level of the N-type charge generation layer 51 closer to the LUMO energy level of the interface functional layer 60, which is beneficial for electrons to migrate from the N-type charge generation layer 51 to the interface functional layer 60.

[0073] According to some exemplary embodiments, referring to FIG3, the first electron transport layer 33 includes a first electron transport material. The first electron transport material and the auxiliary electron transport material may be 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 electrons in the interface functional layer 60 can migrate to the first transport layer.

[0074] 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 increasing the rate at which electrons migrate from the interface functional layer 60 to the first electron transport layer 33, and is beneficial to further improving the luminous efficiency of the organic light-emitting diode.

[0075] The following description, in conjunction with specific embodiments (embodiments of this disclosure) and comparative examples, provides further illustrative details.

[0076] Example 1

[0077] Organic light-emitting diode ① was prepared according to the following steps. The structure of organic light-emitting diode ① can be seen in Figure 3.

[0078] The glass substrate with an indium tin oxide layer (i.e., anode 10) is ultrasonically treated in a cleaning agent, rinsed in deionized water, and dried to remove residual moisture.

[0079] A first hole transport layer 31 is formed on the side of the anode 10 away from the glass substrate by a vapor deposition 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).

[0080] A first light-emitting layer 32 is formed on the side of the first hole transport layer 31 away from the anode 10 by a vapor deposition 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)(pyridinecarboxylate)iridium(III) (FIrpic).

[0081] A first electron transport layer 33 is formed on the side of the first light-emitting layer 32 away from the anode 10 by a vapor deposition process. The thickness of the first electron transport layer 33 is 15 nm, and the material of the first electron transport layer 33 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0082] An interface functional layer 60 is formed on the side of the first electron transport layer 33 away from the anode 10 by a vapor deposition 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).

[0083] An N-type charge generation layer 51 is formed on the side of the interface functional layer 60 away from the anode 10 by a vapor deposition 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% 4,7-diphenyl-1,10-phenanthroline (Bphen) and 1 wt% ytterbium.

[0084] 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 a vapor deposition 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% N,N′-diphenyl-N,N'-di(1-naphthyl)-1,1′-biphenyl-4,4'-diamine (NPB) and 5 wt% 1,4,5,8,9,11-hexaazatriphenylhexanitrile (HAT-CN).

[0085] 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 a vapor deposition 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).

[0086] A second light-emitting layer 42 is formed on the side of the second hole transport layer 41 away from the anode 10 by a vapor deposition 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)(pyridinecarboxylate)iridium(III) (FIrpic).

[0087] A second electron transport layer 43 is formed on the side of the second light-emitting layer 42 away from the anode 10 by a vapor deposition process. The thickness of the second electron transport layer 43 is 35 nm. The second electron transport layer 43 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0088] A cathode 20 is formed on the side of the second electron transport layer 43 away from the anode 10 by a vapor deposition process. The cathode 20 has a thickness of 13 nm and is made of a magnesium-silver alloy with a magnesium to silver mass ratio of 1:9.

[0089] Example 2

[0090] Organic light-emitting diode ② was prepared according to the following steps. The structure of organic light-emitting diode ② can be seen in Figure 3.

[0091] The glass substrate with an indium tin oxide layer (i.e., anode 10) is ultrasonically treated in a cleaning agent, rinsed in deionized water, and dried to remove residual moisture.

[0092] A first hole transport layer 31 is formed on the side of the anode 10 away from the glass substrate by a vapor deposition 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).

[0093] A first light-emitting layer 32 is formed on the side of the first hole transport layer 31 away from the anode 10 by a vapor deposition 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)(pyridinecarboxylate)iridium(III) (FIrpic).

[0094] A first electron transport layer 33 is formed on the side of the first light-emitting layer 32 away from the anode 10 by a vapor deposition process. The thickness of the first electron transport layer 33 is 15 nm, and the material of the first electron transport layer 33 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0095] An interface functional layer 60 is formed on the side of the first electron transport layer 33 away from the anode 10 by a vapor deposition process. The thickness of the interface functional layer 60 is 5 nm, and the material of the interface functional layer 60 is 50 wt% 4,7-diphenyl-1,10-phenanthroline (Bphen) and 50 wt% lithium fluoride.

[0096] An N-type charge generation layer 51 is formed on the side of the interface functional layer 60 away from the anode 10 by a vapor deposition 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% 4,7-diphenyl-1,10-phenanthroline (Bphen) and 1 wt% ytterbium.

[0097] 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 a vapor deposition 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% N,N'-diphenyl-N,N'-di(1-naphthyl)-1,1′-biphenyl-4,4'-diamine (NPB) and 5 wt% 1,4,5,8,9,11-hexaazatriphenylhexanitrile (HAT-CN).

[0098] 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 a vapor deposition 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).

[0099] A second light-emitting layer 42 is formed on the side of the second hole transport layer 41 away from the anode 10 by a vapor deposition 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)(pyridinecarboxylate)iridium(III) (FIrpic).

[0100] A second electron transport layer 43 is formed on the side of the second light-emitting layer 42 away from the anode 10 by a vapor deposition process. The thickness of the second electron transport layer 43 is 35 nm. The second electron transport layer 43 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0101] A cathode 20 is formed on the side of the second electron transport layer 43 away from the anode 10 by a vapor deposition process. The cathode 20 has a thickness of 13 nm and is made of a magnesium-silver alloy with a magnesium to silver mass ratio of 1:9.

[0102] Comparative Example 1

[0103] Organic light-emitting diode ③ was prepared according to the following steps. The structure of organic light-emitting diode ③ can be seen in Figure 1.

[0104] The glass substrate with an indium tin oxide layer (i.e., anode 10) is ultrasonically treated in a cleaning agent, rinsed in deionized water, and dried to remove residual moisture.

[0105] A first hole transport layer 31 is formed on the side of the anode 10 away from the glass substrate by a vapor deposition 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).

[0106] A first light-emitting layer 32 is formed on the side of the first hole transport layer 31 away from the anode 10 by a vapor deposition 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)(pyridinecarboxylate)iridium(III) (FIrpic).

[0107] A first electron transport layer 33 is formed on the side of the first light-emitting layer 32 away from the anode 10 by a vapor deposition process. The thickness of the first electron transport layer 33 is 15 nm, and the material of the first electron transport layer 33 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0108] 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 a vapor deposition 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% 4,7-diphenyl-1,10-phenanthroline (Bphen) and 1 wt% ytterbium.

[0109] 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 a vapor deposition 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% N,N′-diphenyl-N,N'-di(1-naphthyl)-1,1f-biphenyl-4,4′-diamine (NPB) and 5 wt% 1,4,5,8,9,11-hexaazatriphenylhexanitrile (HAT-CN).

[0110] 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 a vapor deposition 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).

[0111] A second light-emitting layer 42 is formed on the side of the second hole transport layer 41 away from the anode 10 by a vapor deposition 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)(pyridinecarboxylate)iridium(III) (FIrpic).

[0112] A second electron transport layer 43 is formed on the side of the second light-emitting layer 42 away from the anode 10 by a vapor deposition process. The thickness of the second electron transport layer 43 is 35 nm. The second electron transport layer 43 is 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0113] A cathode 20 is formed on the side of the second electron transport layer 43 away from the anode 10 by a vapor deposition process. The cathode 20 has a thickness of 13 nm and is made of a magnesium-silver alloy with a magnesium to silver mass ratio of 1:9.

[0114] 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 ⑧ prepared in Comparative Example 1 were subjected to device performance tests. Test data on turn-on voltage, current efficiency, device lifetime, and device sheet resistance were obtained. The relevant test data are summarized in Table 1. Among them, the test data of organic light-emitting diode ③ were used as the baseline value of 100%, and the test data of organic light-emitting diode ① and organic light-emitting diode ② were obtained respectively.

[0115] Table 1

[0116] As can be seen from the data in Table 1, compared with OLED ⑧, OLED ① has a 5% higher start-up voltage, a 1% lower current efficiency, an 18% higher device lifetime, and a 21% higher device resistance. OLED ① increases its device lifetime and sheet resistance by adding an interface functional layer between the N-type charge generation layer and the first electron transport layer. This interface functional layer can form coordination bonds with free metal ions, thereby effectively weakening the diffusion of metal ions.

[0117] Compared to organic light-emitting diode (OLED) ③, organic light-emitting diode (OLED) ② has a 2% lower turn-on voltage, a 3% higher current efficiency, a 15% higher device lifetime, and a 17% higher device resistance. OLED ② increases its device lifetime and sheet resistance by adding an interface functional layer between the N-type charge generation layer and the first electron transport layer. This interface functional layer can form coordination bonds with free metal ions, effectively weakening the diffusion of metal ions.

[0118] Furthermore, comparing the test data of organic light-emitting diode ① and organic light-emitting diode ②, since the interface functional layer of organic light-emitting diode ② is doped with lithium fluoride, the electron injection and electron transport capabilities of the interface functional layer of organic light-emitting diode ② are stronger. As a result, organic light-emitting diode ② has a lower turn-on voltage and higher current efficiency. Correspondingly, the device lifetime and device sheet resistance of organic light-emitting diode ② are slightly lower than those of organic light-emitting diode ①.

[0119] Figure 4 schematically shows a cross-sectional view of a display substrate according to some embodiments of the present disclosure.

[0120] At least some embodiments of this disclosure also provide a display substrate. Referring to FIG4, the display substrate includes a substrate 1, a driving circuit layer 2 located on the substrate 1, a plurality of organic light-emitting diodes (OLEDs) 3 located on the side of the driving circuit layer 2 away from the substrate 1, and an encapsulation layer 4 located on the side of the plurality of OLEDs 3 away from the substrate 1. For the sake of simplifying the fabrication process, a portion of the film layer of the OLEDs 3 is formed as a common film layer, which is a continuous film layer covering the entire display area of ​​the display substrate. Adjacent OLEDs 3 are connected through the common film layer, which may pose a risk of lateral crosstalk problems.

[0121] Referring to Figures 3 and 4, by way of example, 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 generation unit 50, and the interface functional layer 60 in the organic light-emitting diode 3 is a common film layer.

[0122] The organic light-emitting diode 3 in the display substrate is the organic light-emitting diode described above. Because an interface functional layer located between the charge generation 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 display defects caused by lateral crosstalk.

[0123] At least some embodiments of this disclosure also provide a display device comprising the display substrate described above. The display device may include any device or product with display functionality. For example, the display device may be a smartphone, mobile phone, e-book reader, desktop computer (PC), laptop PC, netbook PC, personal digital assistant (PDA), portable multimedia player (PMP), digital audio player, mobile medical device, camera, wearable device (e.g., head-mounted device, electronic clothing, electronic bracelet, electronic necklace, electronic accessory, electronic tattoo, or smartwatch), television set, etc.

[0124] It should be understood that the display device according to some exemplary embodiments of this disclosure has all the features and advantages of the display substrate described above, which can be referred to in the above description of the display substrate and will not be repeated here.

[0125] As used herein, the terms “substantially,” “approximately,” “about,” and other similar terms are used as terms of approximation rather than as terms of degree, and they are intended to account for 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 variations, measurement problems, and errors associated with the measurement of a particular quantity (i.e., limitations of the measurement system), “approximately” or “about” as used herein includes the stated value and indicates that the particular value is within an acceptable range of deviation for one of ordinary skill in the art. For example, “approximately” may mean within one or more standard deviations, or within ±10% or ±5% of the stated value.

[0126] While some embodiments based on the general inventive concept of this disclosure have been illustrated and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the general inventive concept of this 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 includes: anode; The first light-emitting unit is located on the anode; A charge generating unit is located on the side of the first light-emitting unit away from the anode, and the charge generating unit contains a metallic elemental dopant; The second light-emitting unit is located on the side of the charge-generating unit away from the anode; and The cathode is located on the side of the second light-emitting unit away from the anode; An interface functional layer is further provided between the charge generating unit and the first light-emitting unit. The material of the interface functional layer includes an auxiliary electron transport material, which has the ability to form coordination bonds with metal ions from the metal elemental dopant.

2. The organic light-emitting diode according to claim 1, wherein, The auxiliary electron transport material includes a coordination functional group, which 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 coordinating 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 of the aforementioned coordination functional groups.

5. The organic light-emitting diode according to any one of claims 2-4, 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-tris(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 1-5, 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 alkali metal halide has a mass percentage content of 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 1-8, wherein, The charge generation unit includes an N-type charge generation layer located on the side of the interface functional layer away from the anode and a side of the N-type charge generation layer away from the anode, wherein the thickness of the interface functional layer is less than the thickness 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 comprises a host electron transport material and the metal elemental dopant, wherein the host electron transport material and the auxiliary electron transport material comprise the same material.

12. The organic light-emitting diode according to claim 11, wherein, The material of the interface functional layer does not include elemental metals.

13. The organic light-emitting diode according to any one of claims 1-12, wherein, The first light-emitting unit includes a first hole transport layer located on the anode, a first light-emitting layer located on the 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, wherein 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.

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 includes an organic light-emitting diode as described in any one of claims 1-14.

16. A display device, wherein, The display device includes the display substrate as described in claim 15.

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