Display device

Abstract

An embodiment of the present disclosure provides a display device including a plurality of sub-pixels emitting light of different colors, wherein at least one sub-pixel includes an anode, a cathode, a light-emitting layer disposed between the anode and the cathode, and an electron blocking layer disposed on a side of the light-emitting layer near the anode, wherein edges of the light-emitting layers of two adjacent sub-pixels emitting light of different colors overlap or are isolated; in at least one sub-pixel, the light-emitting layer includes a host material and a dopant material, wherein the host material includes an N-type material and a P-type material; and in at least one sub-pixel, the material of the electron blocking layer and the N-type material satisfy the following conditions: 2.75 eV ≤ |LUMO N‑host ‑HOMO EBL │<3.05eV;0.3<│HOMO N‑host ‑HOMO EBL │≤1eV, and │HOMO EBL │<│HOMO N‑host │.

Description

[0001] This case is a divisional application of patent application 202080003698.6. The application date of the original application is December 28, 2020, the application number is 202080003698.6, and the name of the invention is: Organic electroluminescent device and display device. Technical Field

[0002] The embodiments of the present disclosure relate to, but are not limited to, the field of display technology, and in particular to a display device. Background Art

[0003] Currently, organic electroluminescent (OLED) devices are essentially composed of an anode, a hole-transporting layer, an electron-blocking layer, a light-emitting layer, a hole-blocking layer, an electron-transporting layer, and a cathode. The electron-blocking and hole-blocking layers block excess electrons, holes, and excitons that are not utilized by the light-emitting layer. However, the electron-blocking layer is unstable to electrons and can break down over time, leading to device failure. Summary of the Invention

[0004] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0005] An embodiment of the present disclosure provides a display device including a plurality of sub-pixels emitting light of different colors, wherein at least one sub-pixel includes an anode, a cathode, a light-emitting layer disposed between the anode and the cathode, and an electron blocking layer disposed on a side of the light-emitting layer close to the anode, wherein edges of the light-emitting layers of two adjacent sub-pixels emitting light of different colors overlap or are isolated.

[0006] In at least one sub-pixel, the light-emitting layer includes a host material and a dopant material, the host material includes an N-type material and a P-type material, and the N-type material includes a compound of the following structural formula:

[0007]

[0008] Wherein, L2, L3, and L4 are independently a single bond, a benzene ring, or a biphenyl;

[0009] AR2 is selected from the following structures:

[0010]

[0011] in, Indicates the connection position with L3;

[0012] AR3 and AR4 are independently selected from: substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted heteroaryl having 5-30 ring atoms;

[0013] In at least one sub-pixel, the material of the electron blocking layer includes a compound having the following structural formula:

[0014]

[0015] Wherein, L1 is a single bond, a benzene ring or a biphenyl;

[0016] R1, R2, R3, and R4 are independently selected from the group consisting of hydrogen, CHO, C(=O)R5, P(=O)R5, S(=O)R5, cyano, nitrosilyl, borane, hydroxyl, carboxyl, C1-C4 straight-chain alkyl, C3-C40 cycloalkyl or branched alkyl, C2-C40 alkenyl or alkynyl, and aryl or heteroaryl having 5-60 ring atoms; wherein R5 in C(=O)R5, P(=O)R5, and S(=O)R5 is independently selected from the group consisting of C1-C4 straight-chain alkyl, C3-C40 cycloalkyl or branched alkyl, C2-C40 alkenyl or alkynyl, and aryl or heteroaryl having 5-60 ring atoms;

[0017] AR1 is any one of the following: substituted or unsubstituted diphenylfluorene, substituted or unsubstituted spirobifluorene, substituted or unsubstituted spirofluorene anthracene;

[0018] In at least one sub-pixel, the material of the electron blocking layer and the N-type material satisfy:

[0019] 2.75eV≤│LUMO N-host -HOMO EBL │<3.05eV;

[0020] 0.3<│HOMO N-host -HOMO EBL │≤1eV, and │HOMO EBL │<│HOMO N-host │;

[0021] Among them, LUMO N-host is the lowest unoccupied molecular orbital energy level of the N-type material, HOMO EBL is the highest occupied molecular orbital energy level of the electron blocking layer material, HOMO N-host is the highest occupied molecular orbital energy level of the N-type material.

[0022] In an exemplary embodiment, in at least one sub-pixel, a difference between a peak wavelength of an emission spectrum curve of an exciplex formed by the material of the electron blocking layer and the N-type material and an absorption band edge wavelength of an absorption spectrum curve of the doping material is Δλ, and Δλ>30 nm.

[0023] In an exemplary embodiment, wherein the AR1 is selected from any one of the following structures:

[0024]

[0025] in, represents the connection position with L1, and R represents hydrogen or hydrocarbon group on the spiro ring.

[0026] In an exemplary embodiment, the material of the electron blocking layer includes any one or more of the following:

[0027]

[0028] In an exemplary embodiment, the N-type material includes a compound having the following structural formula:

[0029]

[0030] In an exemplary embodiment, the P-type material includes a compound having the following structural formula:

[0031]

[0032] In an exemplary embodiment, the doping material includes any one or more of the following: coumarin dyes, quinacridone copper derivatives, polycyclic aromatic hydrocarbons, diamine anthracene derivatives, carbazole derivatives, and metal complexes.

[0033] In an exemplary embodiment, at least one sub-pixel further includes a hole transport layer disposed between the anode and the electron blocking layer, and the material of the hole transport layer and the material of the electron blocking layer satisfy: 0eV≤|HOMO HTL -HOMO EBL │≤0.2eV; where HOMO HTL It is the highest occupied molecular orbital energy level of the material of the hole transport layer.

[0034] In an exemplary embodiment, the material of the hole transport layer includes a compound having the following structural formula:

[0035]

[0036] In an exemplary embodiment, at least one sub-pixel further includes a hole injection layer disposed between the hole transport layer and the anode, and a material of the hole injection layer includes 4,4',4 tris[2-naphthylphenylamino]triphenylamine.

[0037] In an exemplary embodiment, at least one sub-pixel further includes a hole blocking layer disposed on a side of the light-emitting layer facing the cathode, and a material of the hole blocking layer includes a compound having the following structural formula:

[0038]

[0039] In an exemplary embodiment, at least one sub-pixel further includes an electron transport layer disposed between the hole blocking layer and the cathode, and a material of the electron transport layer includes any one or more of the following: 8-hydroxyquinoline lithium or 8-hydroxyquinoline aluminum.

[0040] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are intended to provide a further understanding of the technical solutions of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the technical solutions of the present disclosure and do not constitute a limitation of the technical solutions of the present disclosure. The shapes and sizes of the components in the drawings do not reflect the actual scale and are intended only to illustrate the contents of the present disclosure.

[0042] Figure 1 A schematic diagram of the planar structure of a display area of a display substrate;

[0043] Figure 2 for Figure 1 A schematic cross-sectional structure diagram of a display substrate;

[0044] Figure 3 is a schematic structural diagram of an organic electroluminescent device according to an exemplary embodiment of the present disclosure;

[0045] Figure 4 A schematic diagram of the material energy level relationship of some film layers in an organic electroluminescent device according to an exemplary embodiment of the present disclosure;

[0046] Figure 5 Spectra of some film materials in an organic electroluminescent device according to an exemplary embodiment of the present disclosure.

[0047] The accompanying drawings are:

[0048] 101, substrate, 102, driving circuit layer, 103, light-emitting structure layer, 104, packaging structure layer;

[0049] 201, first insulating layer, 202, second insulating layer, 203, third insulating layer, 204, fourth insulating layer, 205, planarization layer, 210, driving transistor, 211, storage capacitor;

[0050] 300, pixel definition layer;

[0051] 301, anode, 302, light-emitting layer, 303, cathode, 304, hole injection layer, 305, hole transport layer, 306, electron blocking layer, 307, hole blocking layer, 308, electron transport layer, 309, electron injection layer;

[0052] 310. Light-emitting device;

[0053] 401, first encapsulation layer, 402, second encapsulation layer, 403, third encapsulation layer. DETAILED DESCRIPTION

[0054] The embodiments herein can be implemented in a variety of different forms. A person skilled in the art can easily understand that the implementation and content can be transformed into various forms without departing from the purpose and scope of the present disclosure. Therefore, the present disclosure should not be interpreted as being limited to the contents described in the following embodiments. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other in any manner.

[0055] In the drawings, the sizes of components, layer thicknesses, or regions may be exaggerated for clarity. Therefore, any implementation of the present disclosure is not necessarily limited to the dimensions shown in the drawings, and the shapes and sizes of components in the drawings do not reflect true proportions. Furthermore, the drawings schematically illustrate idealized examples, and any implementation of the present disclosure is not limited to the shapes or values shown in the drawings.

[0056] Figure 1 FIG. 1 is a schematic diagram of a planar structure of a display area of a display substrate. Figure 1 As shown, the display area may include a plurality of pixel units P arranged in a matrix, at least one of the plurality of pixel units P including a first sub-pixel P1 emitting a first color light, a second sub-pixel P2 emitting a second color light, and a third sub-pixel P3 emitting a third color light. The first sub-pixel P1, the second sub-pixel P2, and the third sub-pixel P3 each include a light-emitting device and a pixel driving circuit for driving the light-emitting device to emit light. The first sub-pixel P1, the second sub-pixel P2, and the third sub-pixel P3 may be configured to emit red light, green light, and blue light, respectively. The pixel unit P may also include sub-pixels emitting other colors, such as sub-pixels emitting white light. The shape of the sub-pixels in the pixel unit may be rectangular, rhombus, pentagonal, hexagonal, etc. When the pixel unit includes three sub-pixels, the three sub-pixels may be arranged in rows, columns, or a triangular pattern. When the pixel unit includes four sub-pixels, the four sub-pixels may be arranged in rows, columns, or a square pattern. This is not limited in the present disclosure.

[0057] Figure 2 This is a schematic diagram of the cross-sectional structure of the display area of a display substrate, illustrating the structure of three sub-pixels of the OLED display substrate. Figure 2As shown, in a plane perpendicular to the display substrate, the display substrate may include a driving circuit layer 102 disposed on a substrate 101, a light-emitting structure layer 103 disposed on a side of the driving circuit layer 102 away from the substrate 101, and an encapsulation structure layer 104 disposed on a side of the light-emitting structure layer 103 away from the substrate 101. The driving circuit layer 102 includes a pixel driving circuit. The light-emitting structure layer 103 includes a plurality of OLED light-emitting devices 310, each of which is connected to a corresponding pixel driving circuit. In some possible implementations, the display substrate may include other film layers, such as spacers, etc., which are not limited in this disclosure.

[0058] In some exemplary embodiments, the substrate 101 may be a flexible substrate or a rigid substrate. The flexible substrate may include a first flexible material layer, a first inorganic material layer, a semiconductor layer, a second flexible material layer, and a second inorganic material layer stacked together. The first flexible material layer and the second flexible material layer may be made of polyimide (PI), polyethylene terephthalate (PET), or a surface-treated polymer soft film. The first inorganic material layer and the second inorganic material layer may be made of silicon nitride (SiNx) or silicon oxide (SiOx) to improve the substrate's resistance to water and oxygen. The semiconductor layer may be made of amorphous silicon (a-Si).

[0059] In some exemplary embodiments, Figure 2 As shown, the driving circuit layer 102 of each sub-pixel may include a plurality of transistors and storage capacitors constituting a pixel driving circuit. Figure 2 In the example, each sub-pixel includes a driving transistor and a storage capacitor. In some possible implementations, the driving circuit layer 102 of each sub-pixel may include: a first insulating layer 201 disposed on the substrate 101; an active layer disposed on the first insulating layer 201; a second insulating layer 202 covering the active layer; a gate electrode and a first capacitor electrode disposed on the second insulating layer 202; a third insulating layer 203 covering the gate electrode and the first capacitor electrode; a second capacitor electrode disposed on the third insulating layer 203; a fourth insulating layer 204 covering the second capacitor electrode, with vias being provided on the second insulating layer 202, the third insulating layer 203, and the fourth insulating layer 204, exposing the active layer; a source electrode and a drain electrode disposed on the fourth insulating layer 204, the source electrode and the drain electrode being connected to the active layer through the vias; and a planar layer 205 covering the aforementioned structure, with a via being provided on the planar layer 205, exposing the drain electrode. The active layer, the gate electrode, the source electrode and the drain electrode constitute the driving transistor 210 , and the first capacitor electrode and the second capacitor electrode constitute the storage capacitor 211 .

[0060] In some exemplary embodiments, Figure 2As shown, the light-emitting structure layer 103 may include an anode 301, a pixel definition layer 300, a cathode 303, and an organic functional layer located between the anode 301 and the cathode 303. The organic functional layer includes at least a light-emitting layer 302. The anode 301 is disposed on the planar layer 205 and is connected to the drain electrode of the driving transistor 210 through a via hole provided in the planar layer 205. The pixel definition layer 300 is disposed on the anode 301 and the planar layer 205. The pixel definition layer 300 is provided with a pixel opening, which exposes the anode 301. In some examples, the light-emitting layer 302 is at least partially disposed within the pixel opening and connected to the anode 301. The cathode 303 is disposed on the light-emitting layer 302 and is connected to the light-emitting layer 302. In other examples, the organic functional layer may also include a hole injection layer, a hole transport layer 305 and an electron blocking layer 306 located between the anode 301 and the light-emitting layer 302 and stacked in sequence on the anode 301, and a hole blocking layer, an electron transport layer 308 and an electron injection layer located between the light-emitting layer 302 and the cathode 303 and stacked in sequence on the light-emitting layer 302. The anode 301, the organic functional layer and the cathode 303 of each sub-pixel form an OLED light-emitting device 310, which is configured to emit light of a corresponding color under the drive of a corresponding pixel driving circuit. In some examples, the light-emitting layer 302 of each sub-pixel is located in the sub-pixel region where it is located, and the edges of the light-emitting layers of adjacent sub-pixels may overlap or be isolated. Any other film layer in the organic functional layer of all sub-pixels except the light-emitting layer may be an integrated connected film layer covering all sub-pixels, which may be referred to as a common layer.

[0061] In some exemplary embodiments, the encapsulation structure layer 104 may include a stacked first encapsulation layer 401, a second encapsulation layer 402 and a third encapsulation layer 403. The first encapsulation layer 401 and the third encapsulation layer 403 may be made of inorganic materials, and the second encapsulation layer 402 may be made of organic materials. The second encapsulation layer 402 is arranged between the first encapsulation layer 401 and the third encapsulation layer 403, which can ensure that external water vapor cannot enter the light-emitting device 310.

[0062] The inventors of this application have discovered that in some OLED devices, such as green OLED devices, the main material of the light-emitting layer uses an exciplex, including an N-type material and a P-type material. The electron-blocking layer is generally made of an aromatic amine material, which is a strong electron-donating material and unstable to electrons and excitons. The electron-blocking layer may form an exciplex with the N-type material in the main material at the interface with the light-emitting layer. If the luminescence spectrum (PL spectrum) of the formed exciplex closely overlaps with the absorption spectrum of the dopant in the light-emitting layer, the interfacial exciplex formed between the electron-blocking layer material and the N-type material in the main material of the light-emitting layer will participate in the light emission process, thereby accelerating the decomposition of the electron-blocking layer, resulting in a decrease in device performance and shortening the device life.

[0063] An embodiment of the present disclosure provides an organic electroluminescent device, comprising an anode, a cathode, a light-emitting layer arranged between the anode and the cathode, and an electron blocking layer arranged on the side of the light-emitting layer facing the anode; the light-emitting layer comprises a main material and a doping material, and the main material comprises an N-type material and a P-type material.

[0064] In the embodiment of the present disclosure, the N-type material in the host material of the light-emitting layer can be referred to as N-host material, the P-type material in the host material of the light-emitting layer can be referred to as P-host material, and the electron blocking layer can be referred to as EBL.

[0065] In some exemplary embodiments, the material of the electron blocking layer and the N-type material satisfy:

[0066] 2.75eV≤│LUMO N-host -HOMO EBL │<3.05eV;

[0067] 0.3<│HOMO N-host -HOMO EBL │≤1eV, and │HOMO EBL │<│HOMO N-host │;

[0068] Among them, LUMO N-host is the lowest unoccupied molecular orbital energy level of the N-type material, HOMO EBL is the highest occupied molecular orbital energy level of the electron blocking layer material, HOMO N-host is the highest occupied molecular orbital energy level of the N-type material;

[0069] The difference between the peak wavelength of the luminescence spectrum curve of the exciplex formed by the material of the electron blocking layer and the N-type material and the absorption band edge wavelength of the absorption spectrum curve of the doping material is Δλ, and Δλ>30nm.

[0070] In the embodiment of the present disclosure, by defining LUMO N-host and HOMO EBL The above energy level relationship and the limitation of Δλ>30nm can ensure that the PL spectrum (luminescence spectrum) of the exciplex formed by the electron blocking layer material and the N-host material is far away from the absorption spectrum of the doping material, so that the exciplex formed by the electron blocking layer material and the N-host material does not participate in the luminescence, thereby reducing the decomposition of the electron blocking layer material and improving the life of the device. In addition, by matching the HOMO N-host and HOMO EBL The energy level relationship can ensure that holes are better injected into the light-emitting layer and the luminous efficiency of the device is guaranteed.

[0071] In some exemplary embodiments, the organic electroluminescent device further comprises a hole transport layer (HTL) disposed between the anode and the electron blocking layer, and the material of the hole transport layer and the material of the electron blocking layer satisfy the following relationship: 0eV≤|HOMO HTL -HOMO EBL │≤0.2eV; where HOMO HTL It is the highest occupied molecular orbital energy level of the material of the hole transport layer.

[0072] In this example, by matching the HOMO energy level relationship between the hole transport layer material and the electron blocking layer material, the transmission of holes to the electron blocking layer is facilitated, thereby facilitating the improvement of the device's luminous efficiency.

[0073] Herein, the highest occupied molecular orbital energy level is referred to as the HOMO energy level, and the lowest unoccupied molecular orbital energy level is referred to as the LUMO energy level. The relationship between the HOMO or LUMO energy levels of different materials refers to the relationship between the absolute values of the HOMO or LUMO energy levels.

[0074] like Figure 4 As shown in the figure, ΔE1 is the difference in HOMO energy between the HTL material and the EBL material, and the difference in ΔE1 is 0. ΔE2 is the difference in LUMO energy between the N-host material and the HOMO energy between the EBL material, with 2.75≤ΔE2<3.05. ΔE3 is the difference in HOMO energy between the EBL material and the N-host material, and the HOMO energy level of the EBL material is smaller than that of the N-host material, with 0.3<ΔE3≤1.

[0075] In some exemplary embodiments, the material of the electron blocking layer may be as shown in formula (1):

[0076]

[0077] Wherein, in formula (1), L1 is a single bond, a benzene ring or a biphenyl;

[0078] R1, R2, R3, and R4 are independently selected from the group consisting of hydrogen, CHO, C(═O)R5, P(═O)R5, S(═O)R5, cyano, nitrosilanyl, borane, hydroxyl, carboxyl, C1-C4 straight-chain alkyl, C3-C40 cycloalkyl or branched alkyl, C2-C40 alkenyl or alkynyl, and aryl or heteroaryl having 5-60 ring atoms, and may form a ring with each other; wherein R5 in C(═O)R5, P(═O)R5, and S(═O)R5 is independently selected from the group consisting of C1-C4 straight-chain alkyl, C3-C40 cycloalkyl or branched alkyl, C2-C40 alkenyl or alkynyl, and aryl or heteroaryl having 5-60 ring atoms;

[0079] AR1 is any one of the following: substituted or unsubstituted diphenylfluorene, substituted or unsubstituted spirobifluorene, substituted or unsubstituted spirofluorene anthracene; any C atom in AR1 may be substituted by a heteroatom, and the heteroatom may be any one or more of O, S, N, and Si.

[0080] In some examples, AR1 can be selected from any of the following structures:

[0081]

[0082] in, represents the connection position with L1, and R represents H or a hydrocarbon group on the spiro ring (the H on the spiro ring may be substituted by an alkyl group or a hydrocarbon group).

[0083] In some examples of this embodiment, the material of the electron blocking layer may include any one or more of the following:

[0084]

[0085] In some exemplary embodiments, the structure of the N-type material in the host material of the light-emitting layer may be as shown in formula (2):

[0086]

[0087] Wherein, L2, L3, and L4 can independently be a single bond, a benzene ring, or a biphenyl;

[0088] AR2 can be selected from the following structures:

[0089]

[0090] in, Indicates the connection position with L3.

[0091] AR3 and AR4 are independently selected from: a substituted or unsubstituted C6-C30 aryl group, and a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms.

[0092] In an example of this embodiment, the N-type material in the host material of the light-emitting layer may be:

[0093]

[0094] In some exemplary embodiments, the P-type material in the host material of the light-emitting layer may be:

[0095]

[0096] In some exemplary embodiments, the electroluminescent device according to the present disclosure may be a green electroluminescent device.

[0097] In some exemplary embodiments, the doping material of the light-emitting layer may be selected from any one or more of the following: coumarin dyes, quinacridone copper derivatives, polycyclic aromatic hydrocarbons, diamine anthracene derivatives, carbazole derivatives, metal complexes, etc. For example, the doping material may be: coumarin 6 (C-6), coumarin 545T (C-525T), quinacridone copper (QA), N,N'-dimethylquinacridone (DMQA), 5,12-diphenylnaphthonaphthalene (DPT), N10,N10'-diphenyl-N10,N10'-diphthaloyl-9,9'-dianthracene-10,10'-diamine (abbreviated as BA-NPB), tris(8-hydroxyquinolinol)aluminum(III) (abbreviated as Alq3), tris(2-phenylpyridine)iridium (Ir(ppy)3), and di(2-phenylpyridine)iridium acetylacetonate (Ir(ppy)2(acac)).

[0098] Among them, the structural formula of tris(2-phenylpyridine)iridium (Ir(ppy)3) is:

[0099] In some exemplary embodiments, the doping ratio of the dopant material in the light-emitting layer may be 1 wt% to 10 wt%. The doping ratio refers to the proportion of the dopant material in the light-emitting layer, which may be expressed as a mass percentage. During the preparation of the light-emitting layer, the host material and the dopant material of the light-emitting layer may be co-deposited using a multi-source evaporation process so that the host material and the dopant material are uniformly dispersed in the light-emitting layer. The doping ratio can be regulated by controlling the evaporation rate of the dopant material during the evaporation process, or by controlling the evaporation rate ratio of the host material to the dopant material.

[0100] Figure 5 Shown are the luminescence spectrum (PL spectrum) curve f of the excited radical complex formed by the electron blocking layer material (EBL-1) and the N-host material in some examples of the devices of the present disclosure, the PL spectrum curve c of the N-host material, the PL spectrum curve b of the P-host material, and the PL spectrum curve d of the N-host:P-host blended material, the PL spectrum curve e of the blended material of the electron blocking layer material (EBL-1') and the N-host material in the comparative example device, and the absorption spectrum curve a of the dopant material (Dopant) of the light-emitting layer in the examples of the devices of the present disclosure. Figure 5 In the figure, the horizontal axis λ represents the wavelength, and the vertical axis represents the luminous intensity of the PL spectrum and the absorbance of the absorption spectrum (Abs). The absorbance of the doping material of the luminescent layer is measured by ultraviolet-visible spectrophotometry (UV-vis) to obtain the absorption spectrum curve a of the doping material of the luminescent layer. Figure 5 In the spectrum shown, the electron blocking layer material EBL-1 in the device of the present disclosure is N-host material is P-host material is The electron blocking layer material EBL-1' in the device of the comparative example is

[0101] The doping material of the light-emitting layer is Ir(ppy)3.

[0102] from Figure 5 It can be seen that: compared with curve b, curve c, curve d and curve e, the luminescence spectrum curve f of the exciplex formed by the electron blocking layer material (EBL-1) and the N-host material in the light-emitting layer in the device of the present disclosure is far away from the absorption spectrum curve a of the dopant material in the light-emitting layer, and the difference between the peak wavelength of the luminescence spectrum curve f of the formed exciplex and the absorption band edge wavelength of the absorption spectrum curve a of the dopant material is Δλ, Δλ>30nm. Thus, in some exemplary embodiments, the electron blocking layer material adopts the compound with the structure of formula (1) above, the N-host material adopts the compound with the structure of formula (2) above, and when the electron blocking layer material and the N-host material satisfy the above energy level relationship, the luminescence spectrum of the exciplex formed by the electron blocking layer material and the N-host material is far away from the absorption spectrum of the dopant material in the light-emitting layer, does not participate in the light-emitting process, and the decomposition of the electron blocking layer material is delayed, thereby effectively improving the life of the device.

[0103] In some exemplary embodiments, the material of the hole transport layer (HTL) may be selected from aromatic amines or carbazole materials having hole transport properties, such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (BAFLP), 4,4'-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl (DFLDPBi), 4,4'-bis(9-carbazolyl)biphenyl (CBP), 9-phenyl-3-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (PCzPA), and the like.

[0104] In some examples, the hole transport layer (HTL) material may include:

[0105]

[0106] In some exemplary embodiments, Figure 3As shown, the electroluminescent device includes an anode 301, a hole injection layer 304, a hole transport layer 305, an electron blocking layer 306, a light-emitting layer 302, a hole blocking layer 307, an electron transport layer 308, an electron injection layer 309, and a cathode 303 stacked in sequence. The hole injection layer 304 can lower the hole injection barrier and improve the hole injection efficiency. The hole transport layer 305 can increase the hole transport rate and lower the hole injection barrier, thereby improving the hole injection efficiency. The electron blocking layer 306 can block electrons and excitons in the light-emitting layer from migrating toward the anode, thereby improving the luminous efficiency. The hole blocking layer 307 can block holes and excitons in the light-emitting layer from migrating toward the cathode, thereby improving the luminous efficiency. The electron transport layer 308 can increase the electron transport rate. The electron injection layer 309 can lower the electron injection barrier and improve the electron injection efficiency.

[0107] In some exemplary embodiments, anode 301 may be made of a material with a high work function. For bottom-emitting OLEDs, anode 301 may be made of a transparent oxide material, such as indium tin oxide (ITO) or indium zinc oxide (IZO), and the thickness of the anode may be approximately 80 nm to 200 nm. For top-emitting OLEDs, anode 301 may be made of a composite structure of metal and transparent oxide, such as Ag / ITO, Ag / IZO, or ITO / Ag / ITO. The thickness of the metal layer in the anode may be approximately 80 nm to 100 nm, and the thickness of the transparent oxide in anode 301 may be approximately 5 nm to 20 nm.

[0108] In some exemplary embodiments, cathode 303 may be formed of a metal material by an evaporation process. The metal material may be magnesium (Mg), silver (Ag), or aluminum (Al), or an alloy material such as a Mg:Ag alloy. The thickness of the cathode may be approximately 150 nm.

[0109] In some exemplary embodiments, the material of the hole injection layer may be 4,4',4-tris[2-naphthylphenylamino]triphenylamine (2-TNATA), and the structural formula of 2-TNATA is:

[0110] Alternatively, the hole injection layer can be made of a mixture of a hole transport material (host material) and a p-type dopant material, such as MoO3 (molybdenum trioxide) doped with TAPC (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]), i.e., TAPC:MoO3. The thickness of the hole injection layer can be approximately 60 nm.

[0111] In some exemplary embodiments, the material of the electron transport layer may include any one or more of the following: 8-hydroxyquinoline lithium (Liq), 8-hydroxyquinoline aluminum (Alq3). The structural formulas of 8-hydroxyquinoline lithium (Liq) and 8-hydroxyquinoline aluminum (Alq3) are as follows:

[0112]

[0113] In some exemplary embodiments, the electron injection layer may be made of materials such as lithium fluoride (LiF), ytterbium (Yb), magnesium (Mg), or calcium (Ca).

[0114] In some exemplary embodiments, the thickness of the hole injection layer may be approximately 60 nm, the thickness of the hole transport layer may be approximately 60 nm, the thickness of the electron blocking layer may be approximately 30 nm, the thickness of the light emitting layer may be approximately 30 nm, the thickness of the hole blocking layer may be approximately 10 nm, the thickness of the electron transport layer may be approximately 40 nm, and the thickness of the electron injection layer may be approximately 0.2 nm.

[0115] In some exemplary embodiments, a display substrate including an OLED device may be prepared using the following preparation method. First, a driving circuit layer is formed on a substrate by a patterning process, and the driving circuit layer of each sub-pixel may include a driving transistor and a storage capacitor constituting a pixel driving circuit. Subsequently, a flat layer is formed on the substrate forming the aforementioned structure, and a via is formed on the flat layer of each sub-pixel to expose the drain electrode of the driving transistor. Subsequently, an anode is formed on the substrate forming the aforementioned structure by a patterning process, and the anode of each sub-pixel is connected to the drain electrode of the driving transistor through the via on the flat layer. Subsequently, a pixel definition layer is formed on the substrate forming the aforementioned structure by a patterning process, and a pixel opening exposing the anode is formed on the pixel definition layer of each sub-pixel, and each pixel opening serves as the light-emitting area of each sub-pixel. Subsequently, on the substrate forming the aforementioned structure, an open mask is first used to sequentially evaporate a hole injection layer and a hole transport layer, and the hole injection layer and the hole transport layer are common layers, that is, the hole injection layers of all sub-pixels are connected as a whole, and the hole transport layers of all sub-pixels are connected as a whole. The areas of the hole injection layer and the hole transport layer are roughly the same, but their thicknesses are different. Subsequently, a fine metal mask is used to evaporate the electron blocking layer and the red light-emitting layer, the electron blocking layer and the green light-emitting layer, and the electron blocking layer and the blue light-emitting layer in different sub-pixels. The electron blocking layer and the light-emitting layer of adjacent sub-pixels can have a small amount of overlap or can be isolated. Subsequently, an open mask is used to sequentially evaporate the hole blocking layer, the electron transport layer, the electron injection layer and the cathode. The hole blocking layer, the electron transport layer, the electron injection layer and the cathode are all common layers, that is, the hole blocking layers of all sub-pixels are connected as a whole, the electron transport layers of all sub-pixels are connected as a whole, the electron injection layers of all sub-pixels are connected as a whole, and the cathodes of all sub-pixels are connected as a whole.

[0116] In some exemplary embodiments, the evaporated light-emitting layer can adopt a multi-source co-evaporation method to form a light-emitting layer including a main material and a dopant material. The doping ratio of the dopant material can be regulated by controlling the evaporation rate of the dopant material during the evaporation process, or the doping ratio of the dopant material can be regulated by controlling the evaporation rate ratio of the main material and the dopant material.

[0117] The performance of the device of the embodiment of the present disclosure is compared with the performance of the devices of the two comparative examples. Among them, the device of the embodiment of the present disclosure and the devices of the two comparative examples all include an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer and a cathode stacked in sequence. Regarding the materials of the film layers in the device structure, except that the material of the electron blocking layer in the device of the embodiment of the present disclosure is different from that in the two comparative examples, the materials of the other film layers are the same. The materials of the electron blocking layers of the device of Example 1 of the present disclosure, the device of Example 2, the device of Example 3 and the device of Example 4 are EBL-1, EBL-2, EBL-3 and EBL-4, respectively, and the materials of the electron blocking layers of the device of Comparative Example 1 and the device of Comparative Example 2 are EBL-1' and EBL-2', respectively.

[0118] The materials of the relevant film layers of the device of the embodiment of the present disclosure and the devices of the two comparative examples are as follows:

[0119] EBL-1':

[0120]

[0121] EBL-2':

[0122]

[0123] EBL-1:

[0124]

[0125] EBL-2:

[0126]

[0127] EBL-3:

[0128]

[0129] EBL-4:

[0130]

[0131] P-host:

[0132]

[0133] N-host:

[0134]

[0135] Doping material of the light-emitting layer: tris(2-phenylpyridine)iridium (Ir(ppy)3); HIL: 2-TNATA;

[0136] HTL:

[0137]

[0138] HBL:

[0139]

[0140] ETL: 8-hydroxyquinoline aluminum (Alq3);

[0141] EIL:LiF.

[0142] The material energy levels of the electron blocking layer, P-host, and N-host of the device of the embodiment of the present disclosure and the devices of the two comparative examples are shown in Table 1 below:

[0143] Table 1 Material energy level parameters

[0144] HOMO / eV LUMO / eV EBL-1' -5.44 -2.31 EBL-2' -5.57 -2.45 EBL-1 -5.38 -2.41 EBL-2 -5.30 -2.32 EBL-3 -5.19 -2.09 EBL-4 -5.25 -2.19 P-host -5.47 -2.19 N-host -5.83 -2.39

[0145] In Table 1, the energy level relationship between the electron blocking layer material (EBL-1) and the N-host material is calculated using the device of Example 1 of the present disclosure as an example. The difference between the LUMO energy level of the N-host material and the HOMO energy level of the EBL-1 material is: ΔE2 = │-2.39-(-5.38)│ = 2.99, satisfying: 2.75≤ΔE2<3.05. The difference between the HOMO energy level of the EBL-1 material and the HOMO energy level of the N-host material is:

[0146] ΔE3 = |-5.38-(-5.83)| = 0.45, satisfying: 0.3 < ΔE3 ≤ 1, and the HOMO energy level of the EBL-1 material is shallower than the HOMO energy level of the N-host material. Similarly, the electron blocking layer materials and N-host materials of the devices of Examples 2, 3, and 4 of the present disclosure satisfy the above energy level relationship.

[0147] The performance comparison results of the device of the embodiment of the present disclosure and the devices of the two comparative examples are shown in Table 2:

[0148] Table 2 Device performance comparison results

[0149] Voltage efficiency Lifespan (T95) Comparative Example 1 100％ 100％ 100％ Comparative Example 2 113％ 102％ 105％ Example 1 103％ 98.5％ 153％ Example 2 101％ 99.3％ 138％ Example 3 103％ 97.8％ 169％ Example 4 105％ 96.5％ 192％

[0150] In Table 2, the device performance data of Comparative Example 2 and Examples 1 to 4 are compared and explained with reference to the device performance data of Comparative Example 1. As can be seen from Table 2, the efficiency and life of the device of Comparative Example 2 are not significantly increased compared to Comparative Example 1, but the voltage is larger. The efficiency and voltage of the devices of Examples 1 to 4 of the present disclosure are comparable to those of Comparative Examples 1 and 2, but the device life is significantly improved compared to Comparative Examples 1 and 2. This shows that: since the luminescence spectrum of the excited radical complex formed by the electron blocking layer material and the N-type material in the main material of the light-emitting layer in the device of the embodiment of the present disclosure is far away from the absorption spectrum of the doping material of the light-emitting layer, it does not participate in the light-emitting process, thereby effectively improving the life of the device without affecting the voltage and efficiency of the device. In Table 2, the device life is measured by T95, which refers to the luminescence time required for the brightness of the light emitted by the device to decay to 95% of the initial brightness.

[0151] The present disclosure also provides a display device comprising the aforementioned organic electroluminescent device. The display device can be any product or component with a display function, such as a mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, navigation system, car display, smart watch, smart bracelet, or the like.

[0152] Although the embodiments disclosed in this disclosure are as described above, the contents described are merely embodiments adopted to facilitate understanding of the disclosure and are not intended to limit the disclosure. Any person skilled in the art may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope of the disclosure. However, the scope of patent protection of this application shall still be based on the scope defined by the attached claims.

Claims

1. A display device comprising a plurality of sub-pixels emitting light of different colors, wherein at least one sub-pixel comprises an anode, a cathode, a light-emitting layer disposed between the anode and the cathode, and an electron blocking layer disposed on a side of the light-emitting layer proximal to the anode, wherein edges of the light-emitting layers of two adjacent sub-pixels emitting light of different colors overlap or are isolated from each other; In at least one sub-pixel, the light-emitting layer includes a host material and a dopant material, the host material includes an N-type material and a P-type material, and the N-type material includes a compound of the following structural formula: in, L2, L3, and L4 are independently a single bond, a benzene ring, or a biphenyl; AR2 is selected from the following structures: in, Indicates the connection position with L3; AR3 and AR4 are independently selected from: substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted heteroaryl having 5-30 ring atoms; In at least one sub-pixel, the material of the electron blocking layer includes a compound having the following structural formula: Wherein, L1 is a single bond, a benzene ring or a biphenyl; R1, R2, R3, and R4 are independently selected from the group consisting of hydrogen, CHO, C(=O)R5, P(=O)R5, S(=O)R5, cyano, nitrosilyl, borane, hydroxyl, carboxyl, C1-C4 straight-chain alkyl, C3-C40 cycloalkyl or branched alkyl, C2-C40 alkenyl or alkynyl, and aryl or heteroaryl having 5-60 ring atoms; wherein R5 in C(=O)R5, P(=O)R5, and S(=O)R5 is independently selected from the group consisting of C1-C4 straight-chain alkyl, C3-C40 cycloalkyl or branched alkyl, C2-C40 alkenyl or alkynyl, and aryl or heteroaryl having 5-60 ring atoms; AR1 is any one of the following: substituted or unsubstituted diphenylfluorene, substituted or unsubstituted spirobifluorene, substituted or unsubstituted spirofluorene anthracene; In at least one sub-pixel, the material of the electron blocking layer and the N-type material satisfy: 2.75eV≤│LUMO N-host -HOMO EBL │<3.05eV; 0.3<│HOMO N-host -HOMO EBL │≤1eV, and │HOMO EBL │<│HOMO N-host │; Among them, LUMO N-host is the lowest unoccupied molecular orbital energy level of the N-type material, HOMO EBL is the highest occupied molecular orbital energy level of the electron blocking layer material, HOMO N-host is the highest occupied molecular orbital energy level of the N-type material.

2. The display device according to claim 1, wherein in at least one sub-pixel, a difference between a peak wavelength of a luminescence spectrum curve of an excimer complex formed by the material of the electron blocking layer and the N-type material and an absorption band edge wavelength of an absorption spectrum curve of the doping material is Δλ, and Δλ>30 nm.

3. The display device according to claim 1, wherein The AR1 is selected from any one of the following structures: in, represents the connection position with L1, and R represents hydrogen or hydrocarbon group on the spiro ring.

4. The display device according to claim 1, wherein The material of the electron blocking layer includes any one or more of the following:

5. The display device according to claim 1, wherein The N-type material includes a compound having the following structural formula: The display device according to claim 1 , wherein: The P-type material includes a compound having the following structural formula:

7. The display device according to claim 1, wherein: The doping material includes any one or more of the following: coumarin dyes, quinacridone copper derivatives, polycyclic aromatic hydrocarbons, diamine anthracene derivatives, carbazole derivatives, and metal complexes.

8. The display device according to claim 1 , wherein at least one sub-pixel further comprises a hole transport layer disposed between the anode and the electron blocking layer, wherein the material of the hole transport layer and the material of the electron blocking layer satisfy the following conditions: 0 eV ≤ |HOMO HTL -HOMO EBL │≤0.2eV; where, HOMO HTL It is the highest occupied molecular orbital energy level of the material of the hole transport layer.

9. The display device according to claim 8, wherein: The material of the hole transport layer includes a compound having the following structural formula: 10 . The display device according to claim 8 , wherein at least one sub-pixel further comprises a hole injection layer disposed between the hole transport layer and the anode, wherein a material of the hole injection layer comprises 4,4′,4 tris[2-naphthylphenylamino]triphenylamine.

11. The display device according to claim 1 , wherein at least one sub-pixel further comprises a hole blocking layer disposed on a side of the light-emitting layer facing the cathode, wherein a material of the hole blocking layer comprises a compound having the following structural formula: 12 . The display device according to claim 11 , wherein at least one sub-pixel further comprises an electron transport layer disposed between the hole blocking layer and the cathode, wherein a material of the electron transport layer comprises any one or more of the following: 8-hydroxyquinoline lithium or 8-hydroxyquinoline aluminum.

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