Organic electroluminescence device, display panel and display device

Abstract

This disclosure provides an organic electroluminescent device, a display panel, and a display apparatus. The light-emitting device includes an anode, a cathode, and at least one light-emitting functional layer. The light-emitting functional layer includes a first light-emitting layer and a light-emitting modulation layer. The first light-emitting layer includes a first host material and a first guest material. The light-emitting modulation layer includes a second host material and a second guest material. The first host material, the first guest material, the second host material, and the second guest material satisfy: T1 D1 T1 D2 >T1 H1 >T1 H2 The first and second guest materials are fluorescent materials. The electron mobility and hole mobility of the first host material are of the same order of magnitude, and the ratio of the electron mobility to hole mobility of the second host material is greater than a first preset value; or T1 is satisfied. H1 T1 H2 >T1 D1 >T1 D2 The first guest material is a phosphorescent material, the spectral width of the second guest material is smaller than that of the first guest material, and the emission spectra of the second guest material and the first guest material have overlapping regions.

Description

Technical Field

[0001] This disclosure relates to the field of light-emitting device technology. More specifically, it relates to an organic electroluminescent device, a display panel, and a display device. Background Technology

[0002] Organic light-emitting diodes (OLEDs), as an advanced display technology, have received widespread attention and application due to their advantages such as self-illumination, low power consumption, thinness, and ease of realizing large-area flexible devices. Driven by stacked OLED technology, the application of OLEDs in automotive displays, medium and large-sized products, and other fields has become more extensive and in-depth. Among them, stacked OLED refers to the technology of connecting two or more OLEDs in series through a charge generation layer to significantly improve device efficiency and lifespan.

[0003] However, the efficiency and lifespan of existing OLED light-emitting devices still need to be further improved. Summary of the Invention

[0004] The purpose of this disclosure is to provide an organic electroluminescent device, a display panel, and a display apparatus to further improve the efficiency and lifespan of the light-emitting device.

[0005] To achieve the above objectives, the present disclosure adopts the following technical solution:

[0006] The first aspect of this disclosure provides an organic electroluminescent device, comprising: an anode, a cathode, and at least one light-emitting functional layer located between the anode and the cathode;

[0007] The light-emitting functional layer includes a first light-emitting layer and a light-emitting adjustment layer stacked sequentially.

[0008] The first light-emitting layer includes a first host material and a first object material;

[0009] The light-emitting modulation layer includes a second host material and a second object material;

[0010] The first subject material, the first object material, the second subject material, and the second object material satisfy: T1 D1 >T1 H1 >T1 H2 And T1 D2 >T1 H1 >T1 H2 The first and second guest materials are fluorescent materials. The electron mobility and hole mobility of the first host material are of the same order of magnitude, and the ratio of the electron mobility to hole mobility of the second host material is greater than a first preset value; or

[0011] The first subject material, the first object material, the second subject material, and the second object material satisfy: T1 H1 >T1 D1 >T1 D2 And T1 H2 >T1 D1 >T1 D2 The first guest material is a phosphorescent material, the spectral width of the emission spectrum of the second guest material is smaller than the spectral width of the emission spectrum of the first guest material, and the emission spectrum of the second guest material overlaps with the emission spectrum of the first guest material.

[0012] Among them, T1 H1 T1 represents the triplet energy level of the first host material. H2 T1 represents the triplet energy level of the second host material. D1 T1 represents the triplet energy level of the first guest material. D2 This represents the triplet energy level of the second guest material.

[0013] Optionally, when the first guest material and the second guest material are fluorescent materials, the first guest material and the second guest material are different, and the first host material, the first guest material, the second host material, and the second guest material satisfy the following:

[0014] |HOMO H2 ∣≥∣HOMO D1 |>|HOMO H1 |, and |LUMO H1 |≤|LUMO D2 |<|LUMO H2 |, of which, HOMO H1 This indicates that the highest occupied molecular orbital energy level of the first host material is HOMO. H2 This indicates that the highest occupied molecular orbital energy level of the second host material is HOMO. D1 This indicates that the highest occupied molecular orbital energy level of the first guest material is LUMO. H1 LUMO represents the lowest unoccupied molecular orbital energy level of the first host material. H2 LUMO represents the lowest unoccupied molecular orbital energy level of the second host material. D2 This represents the lowest unoccupied molecular orbital energy level of the second guest material.

[0015] Optionally, when the first guest material and the second guest material are fluorescent materials, the emission spectra of the first guest material and the second guest material satisfy the following:

[0016] 0nm≤Δλ≤2nm and 0nm≤ΔFWHM≤3nm, where Δλ represents the absolute value of the difference between the peak wavelength of the emission spectrum of the first guest material and the peak wavelength of the emission spectrum of the second guest material, and ΔFWHM represents the absolute value of the difference between the half-width at half maximum (WHM) of the emission spectrum of the first guest material and the half-width at half maximum (WHM) of the emission spectrum of the second guest material.

[0017] Optionally, when the first guest material and the second guest material are fluorescent materials, the emission spectra of the first guest material and the second guest material satisfy the following:

[0018] 2nm≤Δλ≤5nm and 3nm≤ΔFWHM≤10nm, where Δλ represents the difference between the peak wavelength of the emission spectrum of the first guest material and the peak wavelength of the emission spectrum of the second guest material, and ΔFWHM represents the absolute value of the difference between the half-width at half maximum (WHM) of the emission spectrum of the first guest material and the half-width at half maximum (WHM) of the emission spectrum of the second guest material.

[0019] Optionally, when the first guest material and the second guest material are fluorescent materials, the thickness of the first luminescent layer is 3 to 10 nm, and the thickness of the luminescence modulation layer is 10 to 17 nm.

[0020] Optionally, when the first object material is a phosphorescent material, the luminescence regulating layer is an electron blocking layer, a hole blocking layer, or a second luminescent layer.

[0021] Optionally, when the first guest material is a phosphorescent material, the second guest material is a fluorescent material, a thermally activated delayed fluorescence material, or a phosphorescent material.

[0022] Optionally, when the light-emitting adjustment layer is the second light-emitting layer, the thickness of the first light-emitting layer is 30-34 nm, and the thickness of the light-emitting adjustment layer is 1-5 nm.

[0023] Optionally, when the light-emitting modulation layer is an electron blocking layer or a hole blocking layer, the volume percentage of the second host material is 98-99.5%, and the volume percentage of the second guest material is 0.5-2%.

[0024] Optionally, the number of light-emitting functional layers is at least two. Among two adjacent light-emitting functional layers, the light-emitting functional layer closer to the anode is referred to as the first light-emitting functional layer and the light-emitting functional layer closer to the cathode is referred to as the second light-emitting functional layer. At least one of the first light-emitting functional layer and the second light-emitting functional layer includes a first light-emitting layer and a light-emitting adjustment layer that are stacked sequentially.

[0025] A second aspect of this disclosure provides a display panel including the organic electroluminescent device described above.

[0026] Optionally, the display panel includes a first-color organic light-emitting device, a second-color organic light-emitting device, and a third-color organic light-emitting device, wherein at least one of the first-color organic light-emitting device, the second-color organic light-emitting device, and the third-color organic light-emitting device is the organic light-emitting device.

[0027] A third aspect of this disclosure provides a display device, including the display panel described above.

[0028] The beneficial effects of this disclosure are as follows:

[0029] The organic electroluminescent device of this disclosure, by setting a light-emitting functional layer including a first light-emitting layer and a light-emitting modulation layer, and for fluorescent light-emitting devices, where both the first guest material and the second guest material are fluorescent materials, can have the light-emitting modulation layer as the second light-emitting layer, i.e., the light-emitting functional layer has a dual-light-emitting layer structure. By setting the electron mobility and hole mobility of the first host material in the first light-emitting layer to be roughly equal, the electron mobility of the second host material in the light-emitting modulation layer to be greater than the hole mobility, and setting the triplet energy levels of both the first and second guest materials to be greater than the triplet energy level of the first host material, the triplet energy level of the first host material is greater than the triplet energy level of the second host material, electrons, holes, and triplet excitons can be spatially separated, effectively avoiding... By eliminating TPA (Transient Photoexcitation Acid), the efficiency and lifespan of the light-emitting device are improved. For phosphorescent light-emitting devices, the first guest material is a phosphorescent material. By setting the spectral width of the emission spectrum of the second guest material in the emission modulation layer to be smaller than that of the first guest material, and the emission spectrum of the second guest material having an overlapping region with that of the first guest material, and the triplet energy levels of the first host material and the second host material being greater than those of the first guest material, the color gamut of the light-emitting device can be improved, the concentration of triplet excitons in the first guest material can be reduced, and the efficiency loss caused by TTA and TPA can be reduced, thereby improving the efficiency and lifespan of the light-emitting device. Attached Figure Description

[0030] The specific embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the structure of organic electroluminescent devices in related technologies;

[0032] Figure 2 A schematic diagram of the structure of an embodiment of the organic electroluminescent device provided in this disclosure;

[0033] Figure 3 When the luminescent functional layer provided in this disclosure is a blue fluorescent luminescent functional layer, the excited state energy level relationship diagram of the first luminescent layer and the luminescent modulation layer is shown.

[0034] Figure 4 This is a schematic diagram of the emission spectra of fluorescent and phosphorescent materials provided in the embodiments of this disclosure;

[0035] Figure 5 When the luminescent functional layer is a green phosphorescent luminescent functional layer and the luminescence modulation layer is a second luminescent layer, the excited state energy level relationship diagram of the first luminescent layer and the luminescence modulation layer is shown.

[0036] Figure 6 A schematic diagram showing the spectral comparison of green phosphorescent luminescent functional layers with single-emissive-layer and double-emissive-layer structures;

[0037] Figure 7 When the luminescent functional layer is a green phosphorescent luminescent functional layer and the luminescence modulation layer is an electron blocking layer, the excited state energy level relationship diagram of the first luminescent layer and the luminescence modulation layer is shown.

[0038] Figure 8 A schematic diagram of the energy level relationship between the first host material, the first guest material, the second host material, and the second guest material when the luminescent functional layer is a blue fluorescent luminescent functional layer;

[0039] Figure 9 A schematic diagram showing that the first light-emitting functional layer 20A of the stacked organic electroluminescent device provided in the embodiments of this disclosure has a dual-light-emitting layer structure;

[0040] Figure 10 A schematic diagram showing that the second light-emitting functional layer 20B of the stacked organic electroluminescent device provided in the embodiments of this disclosure has a dual-light-emitting layer structure;

[0041] Figure 11 A schematic diagram of a stacked organic electroluminescent device provided in the embodiments of this disclosure, in which both the first light-emitting functional layer 20A and the second light-emitting functional layer 20B are dual light-emitting layer structures;

[0042] Figure 12 for Figure 11 The diagram shown is a schematic of a red-green-blue stacked organic electroluminescent device. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0044] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “including,” “comprising,” or “containing,” and similar terms mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0045] Luminous efficiency and lifetime are important performance indicators affecting the application of organic light-emitting diodes. Stacked OLED technology is an innovative technology that connects two or more OLEDs in series through a charge generation layer, thereby multiplying the efficiency and lifetime of the light-emitting device.

[0046] In related technologies, the structure of red, green, and blue OLED stacked light-emitting devices is as follows: Figure 1 As shown, the structure includes, from bottom to top, an anode 100, a hole injection layer 101, a hole transport layer 102, an electron blocking layer 103, a light-emitting layer 104, a hole blocking layer 105, an electron transport layer 106, a charge generation layer 107 (including an electron generation layer 1071 and a hole generation layer 1072), a hole transport layer 108, an electron blocking layer 109, a light-emitting layer 110, a hole blocking layer 111, an electron transport layer 112, an electron injection layer 113, a cathode 114, and a capping layer 115. Figure 1In the red-green-blue multilayer light-emitting device (RGB) structure, R-Prime-1, G-Prime-1, and B-Prime-1 represent the electron blocking layers corresponding to the red, green, and blue light-emitting units in the first layer, respectively. RH1:RD1, GH1:GD1, and BH1:BD1 represent the light-emitting layers corresponding to the red, green, and blue light-emitting units in the first layer, respectively. Similarly, R-Prime-2, G-Prime-2, and B-Prime-2 represent the electron blocking layers corresponding to the red, green, and blue light-emitting units in the second layer, respectively. RH2:RD2, GH2:GD2, and BH2:BD2 represent the light-emitting units corresponding to the red, green, and blue light-emitting units in the second layer, respectively. The light-emitting layers typically include a host material and a dopant material. The host material is typically... Figure 1 As shown in RH1, BH1, GH1, RH2, BH2, and GH2, the object material is as follows: Figure 1 As shown in Figures RD1, BD1, GD1, RD2, BD2, and GD2, the host material typically possesses excellent carrier (electron and hole) transport properties. In OLED devices, electrons from the cathode and holes from the anode need to meet and recombine in the emissive layer to form excitons. The host material can efficiently transport these carriers, ensuring their effective recombination in the emissive layer. After receiving electrons and holes, the host material is excited to a high-energy state. Subsequently, the host material transfers energy to the doped guest material through energy transfer mechanisms (such as Forster energy transfer or Dexter energy transfer). The guest material typically has extremely high luminous efficiency and can rapidly emit light after receiving energy transferred from the host material.

[0047] For any layer of light-emitting device, the light emission process includes the following stages:

[0048] (1) Carrier injection: Under the action of an applied voltage, electrons are injected from the cathode and holes are injected from the anode. Electrons and holes enter the electron transport layer and hole transport layer respectively through the electron injection layer and hole injection layer.

[0049] (2) Carrier transport: The electron transport layer transports electrons to the light-emitting layer, and the hole transport layer transports holes to the light-emitting layer.

[0050] (3) Carrier recombination: In the luminescent layer, electrons and holes meet and recombine to form excitons (i.e., electron-hole pairs). The excitons are in an unstable high-energy state (excited state). Specifically, excited states mainly include two types: singlet state (usually denoted as S1) and triplet state (usually denoted as T1).

[0051] (4) Exciton de-excitation luminescence: Excitons transition from a high-energy state to a low-energy state (i.e., the ground state S0) through radiative relaxation and release energy as photons. For example, excitons in the singlet state S1 can return to the ground state S0 through radiative transition (i.e., luminescence), or excitons in the triplet state T1 can return to the ground state S0 through radiative transition (i.e., luminescence).

[0052] for Figure 1 The stacked light-emitting devices shown all have single-layer light-emitting layers, and their performance (such as luminous efficiency and lifetime) is close to its limit, making further improvement difficult. However, the demands on the performance of light-emitting devices continue to increase, thus requiring the development of new device structures to further improve the luminous efficiency and lifetime of these devices.

[0053] To address the aforementioned technical problems, this disclosure provides an organic electroluminescent device, a display panel, and a display apparatus. The embodiments of this disclosure are described in detail below with reference to specific examples.

[0054] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of the organic electroluminescent device provided in the embodiments of this disclosure, as shown below. Figure 2 As shown, the organic electroluminescent device includes an anode 10, a cathode 30, and at least one light-emitting functional layer 20 located between the anode 10 and the cathode 30. The light-emitting functional layer 20 includes a first light-emitting layer (EML1) 201 and a light-emitting modulation layer 202 stacked sequentially. The first light-emitting layer 201 includes a first host material (denoted as H1) and a first guest material (denoted as D1). The light-emitting modulation layer 202 includes a second host material (denoted as H2) and a second guest material (denoted as D2).

[0055] Among them, the first host material H1, the first object material D1, the second host material H2, and the second object material D2 satisfy: T1 D1 >T1 H1 >T1 H2 And T1 D2 >T1 H1 >T1 H2 The first guest material D1 and the second guest material D2 are fluorescent materials. The electron mobility and hole mobility of the first host material H1 are of the same order of magnitude, and the ratio of the electron mobility to hole mobility of the second host material H2 is greater than a first preset value; or

[0056] The first subject material H1, the first object material D1, the second subject material H2, and the second object material D2 satisfy: T1 H1 >T1 D1>T1 D2 And T1 H2 >T1 D1 >T1 D2 The first guest material D1 is a phosphorescent material, the spectral width of the emission spectrum of the second guest material D2 is smaller than the spectral width of the emission spectrum of the first guest material D1, and the emission spectrum of the second guest material D2 has an overlapping region with the emission spectrum of the first guest material D1.

[0057] Among them, T1 H1 T1 represents the triplet energy level of the first host material H1. H2 T1 represents the triplet energy level of the second host material H2. D1 T1 represents the triplet energy level of the first guest material D1. D2 This represents the triplet energy level of the second guest material D2.

[0058] in, Figure 2 In the schematic diagram shown, the first light-emitting layer 201 is positioned close to the anode 10 and the light-emitting adjustment layer 202 is positioned close to the cathode 30. It can be understood that the first light-emitting layer 201 can also be positioned close to the cathode 30 and the light-emitting adjustment layer 202 can be positioned close to the anode 10.

[0059] Ideally, the electron mobility and hole mobility of the first host material H1 should be the same, while the electron mobility of the second host material H2 should be much greater than the hole mobility. In practice, the electron mobility and hole mobility of the first host material H1 can be of the same order of magnitude, and the ratio of the order of magnitude of the electron mobility and hole mobility of the second host material H2 can be greater than a first preset value K, such as K being a natural number greater than 1. For example, K could be a natural number such as 5, 10, or 12.

[0060] Optionally, in this embodiment, the light-emitting functional layer 20 is a fluorescent light-emitting functional layer or a phosphorescent light-emitting functional layer. The fluorescent light-emitting functional layer can be a red fluorescent light-emitting functional layer, a green fluorescent light-emitting functional layer, or a blue fluorescent light-emitting functional layer, and the phosphorescent light-emitting functional layer can be a red phosphorescent light-emitting functional layer, a green phosphorescent light-emitting functional layer, or a blue phosphorescent light-emitting functional layer.

[0061] When the light-emitting functional layer 20 is a fluorescent light-emitting functional layer (i.e., fluorescent light-emitting), the first guest material D1 and the second guest material D2 are both fluorescent materials. At this time, the light-emitting adjustment layer 202 is a second light-emitting layer (EML2) stacked with the first light-emitting layer 201. That is, the light-emitting functional layer 20 includes the first light-emitting layer 201 and the second light-emitting layer stacked in sequence.

[0062] When the light-emitting functional layer 20 is a phosphorescent functional layer (i.e., phosphorescence), the first guest material D1 is a phosphorescent material, and the second guest material D2 needs to satisfy the requirement that the spectral width of its emission spectrum is smaller than that of the emission spectrum of the first guest material D1, and that the emission spectrum of the second guest material D2 overlaps with that of the first guest material D1. In this case, the light-emitting adjustment layer 202 can be formed by doping the second guest material D2 into the electron blocking layer adjacent to the first light-emitting layer 201, or by doping the second guest material D2 into the hole blocking layer adjacent to the first light-emitting layer 201, or by adding a separate second light-emitting layer. Correspondingly, the light-emitting adjustment layer 202 can be understood as an electron blocking layer, a hole blocking layer, or a second light-emitting layer.

[0063] When the luminescent functional layer 20 is a fluorescent luminescent functional layer, combined with Figure 3 Describe the light-emitting principle of the light-emitting functional layer 20. Figure 3 The diagram shows the excited-state energy level relationship between the first luminescent layer 201 and the luminescence modulation layer (i.e., the second luminescent layer) 202 when the luminescent functional layer is a blue fluorescent luminescent functional layer. Figure 3 As shown, the first light-emitting layer 201 and the light-emitting modulation layer 202 satisfy T1 D1 >T1 H1 >T1 H2 And T1 D2 >T1 H1 >T1 H2 Assume that the first host material is denoted as BH1, the first guest material as BD1, the second host material as BH2, and the second guest material as BD2. The singlet excitons formed in the first host material BH1 are denoted as S1(BH1) and the triplet excitons as T1(BH1). The singlet excitons formed in the first guest material BD1 are denoted as S1(BD1) and the triplet excitons as T1(BD1). The singlet excitons formed in the second host material BH2 are denoted as S1(BH2) and the triplet excitons as T1(BH2). The singlet excitons formed in the second guest material BD2 are denoted as S1(BD2) and the triplet excitons as T1(BD2). In this case, the energy level relationships of the first host material BH1, the first guest material BD1, the second host material BH2, and the second guest material BD2 are as follows: Figure 3 As shown: The triplet energy level satisfies: T1 BD1 >T1 BH1 >T1 BH2 And T1 BD2 >T1 BH1 >T1 BH2 And the singlet energy level satisfies: S1 BH1 >S1 BH2 >S1 BD1 And S1BH1 >S1 BH2 >S1 BD2 S1 BH1 S1 BH2 S1 BD1 S1 BD2 Let T1 represent the singlet energy levels of the first host material BH1, the second host material BH2, the first guest material BD1, and the second guest material BD2, respectively. BH1 T1 BH2 T1 BD1 T1 BD2 These represent the triplet energy levels of the first host material BH1, the second host material BH2, the first guest material BD1, and the second guest material BD2, respectively.

[0064] At this point, since the electron mobility and hole mobility of the first host material BH1 are comparable (e.g., of the same order of magnitude), and the electron mobility of the second host material BH2 is greater than the hole mobility (e.g., the ratio of electron mobility to hole mobility is greater than or equal to 10), the second host material BH2 is more inclined to transport electrons. At this time, electrons and holes will mainly meet and recombine in the first host material BH1 to form singlet exciton S1 (BH1) and triplet exciton T1 (BH1). The singlet exciton S1 (BH1) transfers energy to the first guest material BD1 via Forster energy transfer, forming a singlet exciton S1 (BD1). The singlet exciton S1 (BD1) then returns to the ground state S0 via radiative transition (i.e., luminescence). Simultaneously, since the triplet exciton T1 (BH1) has a higher energy level than T1 (BH2), it can transfer energy to the adjacent second host material BH2 via Dexter energy transfer (electron exchange excitation transfer), forming a triplet exciton T1 (BH2). In the luminescence modulation layer 202, the triplet exciton T1 (BH2) can transfer energy via TTA (Triplet-Triplet)... Annihilation (triple-triple annihilation) processes interact to form singlet exciton S1(BH2); singlet exciton S1(BH2) transfers energy to the second guest material BD2 through Forster energy transfer to form singlet exciton S1(BD2); singlet exciton S1(BD2) returns to the ground state S0 through radiative transition (i.e., luminescence).

[0065] In the above-mentioned light emission process, the recombination region of electrons and holes is mainly distributed in the first light-emitting layer 201. By setting the triplet energy level of the first host material BH1 to be greater than that of the second host material BH2, triplet excitons T1 (BH1) in the first host material BH1 can be efficiently transferred to the second host material BH2 to form triplet excitons T1 (BH2). This setting can help reduce the direct quenching of triplet excitons T1 (BH1) in the first light-emitting layer 201, thereby improving the efficiency of the device. Furthermore, by spatially separating electrons and holes (mainly distributed in the first light-emitting layer 201) and triplet excitons T1 (mainly distributed in the light-emitting modulation layer 202), triplet-triplet annihilation (TPA) is effectively avoided, thereby improving the efficiency and lifetime of the light-emitting device.

[0066] When the luminescent functional layer 20 is a phosphorescent luminescent functional layer, the following is combined with Figures 4 to 7 Describe the light-emitting principle of the light-emitting functional layer 20.

[0067] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the emission spectra of fluorescent and phosphorescent materials. Figure 4 It can be seen that when the luminescent material is a phosphorescent material, due to the relatively weak rigidity of phosphorescent molecules, there is usually a high proportion of shoulder peaks and a wide half-peak width in the emission spectrum, resulting in low color purity and significant efficiency loss in the device. For the phosphorescent luminescent functional layer, the luminescence modulation layer 202 is mainly used to improve device efficiency and lifetime by narrowing the emission spectrum and reducing the concentration of triplet excitons in the first guest material.

[0068] in, Figure 5 The diagram shows the excited-state energy level relationship between the first luminescent layer and the luminescent modulation layer when the luminescent functional layer is an organic layer with a green phosphorescent luminescent functional layer and the luminescence modulation layer is a second luminescent layer. (See diagram for example.) Figure 5 As shown, assuming the first host material H1 is denoted as GH1, the second host material H2 as GH2, the first guest material D1 as PGD, and the second guest material D2 as FGD, the singlet excitons formed in the first host material GH1 are denoted as S1(GH1) and the triplet excitons as T1(GH1), the singlet excitons formed in the first guest material PGD are denoted as S1(PGD) and the triplet excitons as T1(PGD), the singlet excitons formed in the second host material GH2 are denoted as S1(GH2) and the triplet excitons as T1(GH2), and the singlet excitons formed in the second guest material FGD are denoted as S1(FGD) and the triplet excitons as T1(FGD), then in this case, the triplet energy levels of the materials in the first luminescent layer 201 and the luminescence modulation layer 202 satisfy: T1 GH1 >T1 PGD >T1 FGDAnd T1 GH2 >T1 PGD >T1 FGD The singlet energy level satisfies: S1 GH1 >S1 PGD >S1 FGD And S1 GH2 >S1 PGD >S1 FGD Among them, S1 BH1 S1 BH2 S1 PGD S1 FGD Let T1 represent the singlet energy levels of the first host material BH1, the second host material BH2, the first guest material PGD, and the second guest material FGD, respectively. BH1 T1 BH2 T1 PGD T1 FGD These represent the triplet energy levels of the first host material BH1, the second host material BH2, the first guest material PGD, and the second guest material FGD, respectively.

[0069] Optionally, the first host material GH1 and the second host material GH2 can be the same material or different materials. The charge transport characteristics of the first host material GH1 and the second host material GH2 must satisfy the bipolar transport characteristic, that is, they can simultaneously transport electrons and holes, and the electron mobility is faster than the hole mobility. When the first host material GH1 and the second host material GH2 are the same material, T1 GH1 =T1 GH2 S1 BH1 =S1 BH2 Specifically, the light-emitting process is as follows:

[0070] When the anode 10 and cathode 30 are energized, electrons and holes meet and recombine in the first host material GH1 to form singlet exciton S1(GH1) and triplet exciton T1(GH1); the singlet exciton S1(GH1) transfers energy to the first guest material PGD through Forster energy transfer and Dexter energy transfer, forming singlet exciton S1(PGD); due to T1 GH1 >T1 PGDTherefore, the triplet exciton T1 (GH1) can transfer energy to the first guest material PGD via Dexter energy transfer, forming the triplet exciton T1 (PGD). Simultaneously, the singlet exciton S1 (PGD) transfers energy to the triplet exciton T1 (PGD) via intersystem crossing (ISC), and the triplet exciton T1 (PGD) returns to the ground state S0 via radiative transition (i.e., luminescence). At the same time, since there is an overlapping region in the emission spectra of the first guest material PGD and the second guest material FGD, it can promote the triplet exciton T1 (PGD) to transfer energy to the second guest material FGD via Forster energy transfer, forming the singlet exciton S1 (FGD). The singlet exciton S1 (FGD) returns to the ground state S0 via radiative transition (i.e., luminescence).

[0071] It should be noted that, Figure 5 In this process, electrons and holes also meet and recombine in the second host material GH2 to form singlet exciton S1(GH2) and triplet exciton T1(GH2). The singlet exciton S1(GH2) transfers energy to the second guest material FGD through Forster energy transfer and Dexter energy transfer, forming singlet exciton S1(FGD). Furthermore, due to T1... GH2 >T1 FGD Therefore, triplet exciton T1(GH2) can transfer energy to the second guest material FGD via Dexter energy transfer, forming triplet exciton T1(FGD). However, the proportion of this energy transfer is relatively small. Figure 5 The text is not indicated.

[0072] In the aforementioned luminescence process, due to the overlapping region of the emission spectra of the first guest material PGD and the second guest material FGD, effective Forster energy transfer can be ensured between the triplet exciton T1 (PGD) and the singlet exciton S1 (FGD). This energy transfer not only improves the excitation efficiency of the second guest material FGD but also reduces the concentration of triplet exciton T1 (PGD) in the first guest material PGD, thereby reducing efficiency losses caused by triplet-triplet annihilation (TTA) and triplet polaron annihilation (TPA), and simultaneously improving device lifetime. Furthermore, since the peak wavelengths of the emission spectra of the second guest material FGD and the first guest material PGD are close (as close as possible), and the emission spectrum of the second guest material FGD is narrower than that of the first guest material PGD, the overall spectrum of the device obtained by combining the first guest material PGD and the second guest material FGD will be narrower (e.g., ...). Figure 6 As shown, Figure 6(A schematic diagram comparing the spectra of the green phosphorescent luminescent functional layer with a single luminescent layer structure and a double luminescent layer structure) This is beneficial for improving the color purity and color gamut coverage of the device.

[0073] Figure 7 The diagram shows the excited-state energy level relationship between the first luminescent layer and the luminescent modulation layer when the luminescent functional layer is a green phosphorescent luminescent functional layer and the luminescence modulation layer is an electron blocking layer. In this case, the second host material H2 is an electron blocking material. The charge transport characteristics of the first host material GH1 and the second host material GH2 satisfy the bipolar transport characteristic, meaning they can simultaneously transport electrons and holes, and the electron mobility is faster than the hole mobility. Figure 7 As shown, the specific light-emitting process is as follows:

[0074] When the anode 10 and cathode 30 are energized, electrons and holes meet and recombine in the first host material GH1 to form singlet exciton S1(GH1) and triplet exciton T1(GH1); the singlet exciton S1(GH1) transfers energy to the first guest material PGD through Forster energy transfer and Dexter energy transfer, forming singlet exciton S1(PGD); due to T1 GH1 >T1 PGD Therefore, the triplet exciton T1 (GH1) can transfer energy to the first guest material PGD via Dexter energy transfer, forming the triplet exciton T1 (PGD). Simultaneously, the singlet exciton S1 (PGD) transfers energy to the triplet exciton T1 (PGD) via intersystem crossing (ISC), and the triplet exciton T1 (PGD) returns to the ground state S0 via radiative transition (i.e., luminescence). At the same time, since there is an overlapping region in the emission spectra of the first guest material PGD and the second guest material FGD, it can promote the triplet exciton T1 (PGD) to transfer energy to the second guest material FGD via Forster energy transfer, forming the singlet exciton S1 (FGD). The singlet exciton S1 (FGD) returns to the ground state S0 via radiative transition (i.e., luminescence).

[0075] and Figure 5 The illustrated embodiment is similar. Figure 7 In this process, electrons and holes also meet and recombine in the second host material GH2 to form singlet exciton S1(GH2) and triplet exciton T1(GH2). The singlet exciton S1(GH2) transfers energy to the second guest material FGD through Forster energy transfer and Dexter energy transfer, forming singlet exciton S1(FGD). Furthermore, due to T1... GH2 >T1 FGDTherefore, triplet exciton T1(GH2) can transfer energy to the second guest material FGD via Dexter energy transfer, forming triplet exciton T1(FGD). However, the proportion of this energy transfer is relatively small. Figure 7 The text is not indicated.

[0076] For example, when the light-emitting modulation layer is an electron blocking layer or a hole blocking layer, the volume percentage of the second host material is 98-99.5%, and the volume percentage of the second guest material is 0.5-2%. It is understood that when the light-emitting modulation layer is a hole blocking layer, the second host material is a hole blocking material. The energy level relationships of the first host material, the first guest material, the second host material, and the second guest material when the light-emitting modulation layer is a hole blocking layer are the same as the energy level relationships of the materials when the light-emitting modulation layer is an electron blocking layer, and will not be elaborated further here.

[0077] Compared with related technologies, the embodiments of this disclosure, by setting the light-emitting functional layer to include a first light-emitting layer and a light-emitting modulation layer, and in the case of a fluorescent light-emitting device, where both the first guest material and the second guest material are fluorescent materials, the light-emitting modulation layer can be the second light-emitting layer, i.e., the light-emitting functional layer is a dual-light-emitting layer structure. By setting the electron mobility and hole mobility of the first host material in the first light-emitting layer to be equivalent, and the electron mobility of the second host material in the light-emitting modulation layer to be greater than the hole mobility, and by setting the triplet energy levels of both the first guest material and the second guest material to be greater than the triplet energy level of the first host material, the triplet energy level of the first host material is greater than the triplet energy level of the second host material, electrons, holes, and triplet excitons can be spatially separated, effectively avoiding triplet-triplet annihilation. The occurrence of TPA (Transient Photoexciton A) improves the efficiency and lifetime of the light-emitting device. For phosphorescent light-emitting devices, the first guest material is a phosphorescent material. By setting the spectral width of the emission spectrum of the second guest material in the light-emitting modulation layer to be smaller than that of the first guest material, and by having an overlapping region between the emission spectra of the second and first guest materials, and by ensuring that the triplet energy levels of the first and second host materials are greater than those of the first guest material, the color gamut of the light-emitting device can be improved. This reduces the concentration of PGD triplet excitons T1 (PGD) in the first guest material, thus reducing efficiency losses caused by TTA and TPA, thereby improving the efficiency and lifetime of the light-emitting device. In other words, this embodiment of the present disclosure, through the structural design of the light-emitting functional layer and by precisely controlling the distribution and conversion processes of electrons, holes, and excitons, can achieve a significant improvement in the efficiency and lifetime of OLED devices.

[0078] In one possible implementation, when the light-emitting functional layer 20 is a fluorescent light-emitting functional layer, the thickness of the first light-emitting layer 201 is less than the thickness of the light-emitting modulation layer 202. The first light-emitting layer 201 is mainly used for the recombination of electrons and holes, and the light-emitting modulation layer 202 is mainly used for the storage and further conversion of triplet excitons (T1). For example, the thickness of the first light-emitting layer 201 is 3-10 nm, and the thickness of the light-emitting modulation layer 202 is 10-17 nm.

[0079] In one possible implementation, when the light-emitting functional layer 20 is a fluorescent light-emitting functional layer, the first guest material D1 and the second guest material D2 can be the same material or different materials. The first guest material D1 is mainly used to receive energy from the first host material H1 and emit fluorescence; the second guest material D2 is mainly used to receive energy from the second host material H2 and emit fluorescence.

[0080] Optionally, the first object material D1 and the second object material D2 are different, and the first host material, the first object material, the second host material, and the second object material satisfy: |HOMO H2 ∣≥∣HOMO D1 |>|HOMO H1 |, and |LUMO H1 |≤|LUMO D2 |<|LUMO H2 |, where HOMO represents the highest occupied molecular orbital energy level, LUMO represents the lowest unoccupied molecular orbital energy level, and HOMO H1 This indicates that the highest occupied molecular orbital energy level of the first host material H1 is HOMO. H2 This indicates that the highest occupied molecular orbital energy level of the second host material H2 is HOMO. D1 This indicates that the highest occupied molecular orbital energy level of the first guest material D1 is LUMO. H1 The lowest unoccupied molecular orbital energy level of the first host material H1, LUMO H2 The lowest unoccupied molecular orbital energy level of the second host material H1, LUMO D2 This represents the lowest unoccupied molecular orbital energy level of the second guest material D2.

[0081] Please refer to Figure 8 , Figure 8 This is a schematic diagram illustrating the energy level relationships among the first host material, the first object material, the second host material, and the second object material, as shown below. Figure 8As shown, the HOMO level of the first guest material D1 near the anode 10 is deeper than that of the first host material H1, thus reducing the probability of the first guest material D1 capturing holes; the LUMO level of the second guest material D2 near the cathode 30 is shallower than that of the second host material H2, thus reducing the probability of the second guest material D2 capturing electrons; by reducing the probability of the guest materials (including the first guest material D1 and the second guest material D2) capturing charges (including electrons and holes), the efficiency of the device can be further improved. It is understood that the first host material H1, the first guest material D1, the second host material H2, and the second guest material D2 in this embodiment of the disclosure also satisfy: T1 D1 >T1 H1 >T1 H2 And T1 D2 >T1 H1 >T1 H2 .

[0082] In one possible implementation, when the light-emitting functional layer 20 is a fluorescent light-emitting functional layer, the light-emitting characteristics of the organic electroluminescent device can also be adjusted by regulating the emission spectra of the first guest material D1 and the second guest material D2.

[0083] Optionally, the emission spectra of the first guest material D1 and the second guest material D2 are similar, such as the emission spectra of the first guest material D1 and the second guest material D2 satisfying:

[0084] 0nm≤Δλ≤2nm and 0nm≤ΔFWHM≤3nm

[0085] Where Δλ represents the absolute value of the difference between the peak wavelength (PL Peak) of the emission spectrum of the first guest material D1 and the peak wavelength of the emission spectrum of the second guest material D2, and ΔFWHM represents the absolute value of the difference between the half-width at half-maximum (FWHM) of the emission spectrum of the first guest material D1 and the half-width at half-maximum (FWHM) of the emission spectrum of the second guest material D2. The peak wavelength (PL Peak) refers to the wavelength at which the light intensity in the emission spectrum reaches its maximum value; the half-width at half-maximum (FWHM) refers to the wavelength range occupied when the spectral intensity drops from the peak intensity to half. Specifically, in the emission spectrum, the light intensity corresponding to the peak wavelength is found, and then extended to both sides until the light intensity drops to half of the peak intensity. The wavelength difference between these two points is the half-width at half-maximum. FWHM reflects the width or dispersion of the spectrum.

[0086] When the emission spectra of the first guest material D1 and the second guest material D2 are similar, there will be a large overlap in their spectra. When the first guest material D1 and the second guest material D2 emit light simultaneously, the emitted light will appear more visually consistent due to the similarity of their spectra, thereby improving the color purity of the device. Color purity is an important indicator for measuring the purity of emitted color, and it is especially important for applications requiring high color accuracy (such as display technology).

[0087] Optionally, the emission spectra of the first guest material D1 and the second guest material D2 differ significantly, for example: the emission spectra of the first guest material D1 and the second guest material D2 satisfy the following:

[0088] 2nm≤Δλ≤5nm and 3nm≤ΔFWHM≤10nm

[0089] Wherein, Δλ represents the difference between the peak wavelength of the emission spectrum of the first guest material D1 and the peak wavelength of the emission spectrum of the second guest material D2, and ΔFWHM represents the absolute value of the difference between the half-width at half maximum (WHM) of the emission spectrum of the first guest material D1 and the half-width at half maximum (WHM) of the emission spectrum of the second guest material D2.

[0090] In this embodiment, the emission spectra of the first guest material D1 and the second guest material D2 differ to some extent in terms of the PL Peak and FWHM, meaning their spectra do not completely overlap. When the first guest material D1 and the second guest material D2 emit light simultaneously, their emission spectra complement each other to a certain extent, thereby broadening the overall emission spectrum range of the device and forming a wider emission spectrum. With a wider emission spectrum, color changes at different viewing angles are relatively smaller, maintaining better viewing angle stability. Therefore, broadening the emission spectrum helps improve the brightness decay (L-Decay) of the OLED device with varying viewing angles.

[0091] Optionally, when the light-emitting functional layer 20 is a fluorescent light-emitting functional layer, the thickness of the first light-emitting layer 201 is 3–10 nm, and the thickness of the light-emitting modulation layer is 10–17 nm. Setting the thickness of the light-emitting modulation layer to be thicker (greater than the thickness of the first light-emitting layer 201) can guide more triplet excitons T1 (BH1) to transfer energy to the second host material through Dexter energy transfer to form triplet excitons T1 (BH2), thereby reducing adverse processes such as TTA in the first light-emitting layer, improving device efficiency and lifetime, and providing sufficient space for electrons and holes to migrate and distribute before recombination, so that electrons and holes mainly recombine in the first light-emitting layer 201.

[0092] In embodiments where the luminescent functional layer is a phosphorescent luminescent functional layer, i.e., when the first guest material is a phosphorescent material, the second guest material is a fluorescent material, a thermally activated delayed fluorescence material, or a phosphorescent material. Specifically, as long as the spectral width of the emission spectrum of the second guest material is smaller than the spectral width of the emission spectrum of the first guest material, and the emission spectra of the second guest material overlap with those of the first guest material, the spectral width of the luminescent functional layer can be narrowed, the concentration of triplet excitons T1 (PGD) can be reduced, and the device lifetime and efficiency can be improved.

[0093] Optionally, when the first guest material is a phosphorescent material, the peak wavelengths of the first guest material D1 and the second guest material D2 should be kept as consistent as possible. For example, the emission spectra of the first guest material D1 and the second guest material D2 should satisfy: 0nm≤Δλ≤5nm, where Δλ represents the absolute value of the difference between the peak wavelength of the emission spectrum of the first guest material D1 and the peak wavelength of the emission spectrum of the second guest material D2. In this case, the first guest material D1 and the second guest material D2 will have a large overlap region in the spectrum.

[0094] The narrow spectral characteristics of the second guest material D2 help to narrow the overall emission spectrum of the OLED device and improve color purity. Furthermore, the emission spectrum of the second guest material D2 overlaps with that of the first guest material D1, which can promote Forster energy transfer (T1(D1)) → S1(D2) (singlet excitons of the second guest material D2). Through the Forster energy transfer mechanism, on the one hand, the triplet energy of the first guest material D1 is effectively utilized, reducing energy loss and improving luminous efficiency; on the other hand, the triplet exciton concentration is reduced, decreasing the occurrence of harmful processes such as TTA and TPA, and extending the device's lifespan.

[0095] In one possible implementation, the thickness of the first light-emitting layer is 30–34 nm, and the thickness of the light-emitting modulation layer is 1–5 nm. By setting the thickness of the light-emitting modulation layer to be relatively thin (e.g., 1–5 nm), it is beneficial for the light-emitting modulation layer to receive energy from the phosphorescent material in the first light-emitting layer through the Forster energy transfer mechanism and emit light with a narrower spectrum, thereby improving the color purity and efficiency of the device.

[0096] In one possible implementation, the number of light-emitting functional layers is at least two. Among two adjacent light-emitting functional layers, the light-emitting functional layer closer to the anode is referred to as the first light-emitting functional layer and the light-emitting functional layer closer to the cathode is referred to as the second light-emitting functional layer. At least one of the first light-emitting functional layer and the second light-emitting functional layer includes a first light-emitting layer and a light-emitting adjustment layer that are stacked sequentially.

[0097] When the light-emitting adjustment layer is the second light-emitting layer, the light-emitting functional layer includes a first light-emitting layer and a second light-emitting layer stacked sequentially. In this case, the light-emitting functional layer can be understood as a dual-light-emitting layer structure. At least one of the first light-emitting functional layer and the second light-emitting functional layer is a dual-light-emitting layer structure.

[0098] For example, an organic electroluminescent device includes a first light-emitting functional layer 20A and a second light-emitting functional layer 20B disposed between an anode and a cathode. Please refer to... Figures 9 to 11 , Figure 9 This is a schematic diagram of the first light-emitting functional layer 20A, which has a dual-light-emitting layer structure. Figure 10 This is a schematic diagram of the second light-emitting functional layer 20B, which has a dual-light-emitting layer structure. Figure 11 This is a schematic diagram showing that both the first light-emitting functional layer 20A and the second light-emitting functional layer 20B are dual-light-emitting layer structures. Figures 9 to 11 Taking the blue fluorescent luminescent functional layer as an example, it can be understood that the luminescent functional layer can also be a green or red fluorescent luminescent functional layer or a red, green, or blue phosphorescent luminescent functional layer.

[0099] Optional, such as Figures 9 to 11 As shown, the first light-emitting functional layer 20A and the second light-emitting functional layer 20B are connected in series through the charge-generating layer 40, and the organic electroluminescent device also includes a capping layer 50, which is located on the side of the cathode 30 away from the anode 10.

[0100] The first light-emitting functional layer 20A includes: a first hole injection layer (HIL) 201A, located between the anode 10 and the second light-emitting functional layer 20B; a first hole transport layer (HTL) 202A, located between the first hole injection layer 201A and the second light-emitting functional layer 20B; a first electron blocking layer (EBL) 203A, located between the first hole transport layer 202A and the second light-emitting functional layer 20B; a light-emitting layer 204A, located between the first electron blocking layer 203A and the second light-emitting functional layer 20B; a first hole blocking layer (HBL) 205A, located between the light-emitting layer 204A and the second light-emitting functional layer 20B; and a first electron transport layer (ETL) 206A, located between the first hole blocking layer 205A and the second light-emitting functional layer 20B.

[0101] The charge generation layer 40 includes: an electron generation layer (NCGL) 401, located between the first electron transport layer 206A and the second light-emitting functional layer 20B; and a hole generation layer (PCGL) 402, located between the electron generation layer 401 and the second light-emitting functional layer 20B.

[0102] The second light-emitting functional layer 20B includes: a second hole transport layer (HTL) 201B, located between the charge generation layer 40 and the cathode 30; a second electron blocking layer (EBL) 202B, located between the second hole transport layer 201B and the cathode 30; a light-emitting layer 203B, located between the second electron blocking layer 202B and the cathode 30; a second hole blocking layer (HBL) 204B, located between the light-emitting layer 203B and the cathode 30; a second electron transport layer (ETL) 205B, located between the second hole blocking layer 204B and the cathode 30; and a first electron injection layer (EIL) 206B, located between the second electron transport layer 205B and the cathode 30.

[0103] like Figure 9 As shown, when the first light-emitting functional layer 20A is a dual-light-emitting layer structure and the second light-emitting functional layer 20B is a single-light-emitting layer structure, the light-emitting layer 204A includes: a first light-emitting layer (EML1A) 2041A, which is located between the first electron blocking layer 203A and the second light-emitting functional layer 20B; and a second light-emitting layer (EML2A) 2042A, which is located between the first light-emitting layer 2041A and the second light-emitting functional layer 20B; the light-emitting layer 203B includes only a single light-emitting layer 2031B.

[0104] like Figure 10 As shown, when the first light-emitting functional layer 20A is a single light-emitting layer structure and the second light-emitting functional layer 20B is a double light-emitting layer structure, the light-emitting layer 204A only includes a single light-emitting layer 2041A; the light-emitting layer 203B includes a first light-emitting layer (EML1B) 2031B, which is located between the second electron blocking layer 202B and the cathode 30; and a second light-emitting layer (EML2B) 2032B, which is located between the first light-emitting layer 2031B and the cathode 30.

[0105] like Figure 11 As shown, when both the first light-emitting functional layer 20A and the second light-emitting functional layer 20B are dual-light-emitting layer structures, the light-emitting layer 204A includes a first light-emitting layer (EML1A) 2041A, located between the first electron blocking layer 203A and the second light-emitting functional layer 20B; a second light-emitting layer (EML2A) 2042A, located between the first light-emitting layer 2041A and the second light-emitting functional layer 20B; the light-emitting layer 203B includes a first light-emitting layer (EML1B) 2031B, located between the second electron blocking layer 202B and the cathode 30; and a second light-emitting layer (EML2B) 2032B, located between the first light-emitting layer 2031B and the cathode 30.

[0106] For example, taking an organic electroluminescent device as a blue fluorescent device (with a blue fluorescent light-emitting functional layer) as an example, Figure 1Using the stacked OLED device shown as a benchmark, the efficiency and lifetime of the organic electroluminescent devices in different structures in the embodiments of this disclosure are compared and analyzed. Please refer to Table 1 for details.

[0107] Table 1. Luminous efficiency and lifetime of light-emitting devices with different structures.

[0108]

[0109]

[0110] Structure 11 in Table 1 is the OLED structure used as a benchmark in related technologies for analysis. Its specific structure is as follows: Figure 1 The diagram shows the following layers: anode / hole injection layer (10nm) / hole transport layer (15nm) / electron blocking layer (5nm) / light-emitting layer (BH:BD, 20nm) / hole blocking layer (5nm) / electron transport layer (10nm) / electron generation layer (NCGL, 180nm) / hole generation layer (PCGL, 90nm) / hole transport layer (34nm) / electron blocking layer (5nm) / light-emitting layer (BH:BD, 20nm) / hole blocking layer (5nm) / electron transport layer (30nm) / electron injection layer (2nm) / cathode (13nm) / capping layer (60nm). The two light-emitting layers have identical structures, and the BH doping concentration in the light-emitting layer is 98–99.5%, while the BD doping concentration is 0.5–2%. In this embodiment, the doping concentration of each material can be a volume percentage, and the hole injection layer (10nm) indicates that the hole injection layer has a thickness of 10nm.

[0111] Structure 12 in Table 1 is Figure 9 The structure shown is as follows: Anode / hole injection layer (10nm) / hole transport layer (15nm) / electron blocking layer (5nm) / EML1 (BH1:BD1,5nm) / EML2 (BH2:BD2,15nm) / hole blocking layer (5nm) / electron transport layer (10nm) / electron generation layer (NCGL,180nm) / hole generation layer (PCGL,90nm) / hole transport layer (34nm) / electron blocking layer (5nm) / light emitting layer (BH:BD,20nm) / hole blocking layer (5nm) / electron transport layer (30nm) / electron injection layer (2nm) / cathode (13nm) / capping layer (60nm).

[0112] Structure 13 in Table 1 is Figure 10The structure shown is as follows: Anode / hole injection layer (10nm) / hole transport layer (15nm) / electron blocking layer (5nm) / light-emitting layer (BH:BD, 20nm) / hole blocking layer (5nm) / electron transport layer (10nm) / electron generation layer (NCGL, 180nm) / hole generation layer (PCGL, 90nm) / hole transport layer (34nm) / electron blocking layer (5nm) / EML1 (BH1:BD1, 5nm) / EML2 (BH2:BD2, 15nm) / hole blocking layer (5nm) / electron transport layer (30nm) / electron injection layer (2nm) / cathode (13nm) / capping layer (60nm).

[0113] Structure 14 in Table 1 is... Figure 11 The structure shown is as follows: Anode / hole injection layer (10nm) / hole transport layer (15nm) / electron blocking layer (5nm) / EML1 (BH1:BD1,5nm) / EML2 (BH2:BD2,15nm) / hole blocking layer (5nm) / electron transport layer (10nm) / electron generation layer (NCGL,180nm) / hole generation layer (PCGL,90nm) / hole transport layer (34nm) / electron blocking layer (5nm) / EML1 (BH1:BD1,5nm) / EML2 (BH2:BD2,15nm) / hole blocking layer (5nm) / electron transport layer (30nm) / electron injection layer (2nm) / cathode (13nm) / capping layer (60nm).

[0114] As shown in Table 1, when the first light-emitting functional layer adopts a dual-emitting-layer structure and the second light-emitting functional layer adopts a single-emitting-layer structure, the efficiency of the organic electroluminescent device is improved by 6% and the device lifetime is improved by 13% compared with the single-emitting-layer structure. When the second light-emitting functional layer adopts a dual-emitting-layer structure and the first light-emitting functional layer adopts a single-emitting-layer structure, the efficiency of the organic electroluminescent device is improved by 9% and the device lifetime is improved by 21% compared with the single-emitting-layer structure. When both the first and second light-emitting functional layers adopt a dual-emitting-layer structure, the efficiency of the organic electroluminescent device is improved by 16% and the device lifetime is improved by 37% compared with the single-emitting-layer structure.

[0115] It is understandable that for red and green fluorescent light-emitting devices, the efficiency and lifespan of the device can be significantly improved by using a double-emitting-layer structure compared to a single-emitting-layer structure. Since the principle is the same, it will not be elaborated here.

[0116] For example, taking an organic electroluminescent device as a green phosphorescent device (with a green phosphorescent luminescent layer) as an example, and using a stacked OLED device in related technologies as a benchmark, the efficiency and lifetime of the organic electroluminescent device in different structures in the embodiments of this disclosure are compared and analyzed. Please refer to Table 2 for details.

[0117] Table 2 Luminous efficiency and lifetime of light-emitting devices with different structures.

[0118] Light-emitting device structure Luminous efficiency life Structure 21 100％ 100％ Structure 22 102％ 110％ Structure 23 102％ 110％

[0119] Structure 21 in Table 2 is the OLED structure analyzed as a benchmark in related technologies, that is, the OLED structure when the light-emitting functional layer is a single layer. Its specific structure is represented as follows: anode / hole injection layer (10nm) / hole transport layer (15nm) / electron blocking layer (10nm) / light-emitting layer (GH:GD, 35nm) / hole blocking layer (5nm) / electron transport layer (10nm) / electron generation layer (NCGL, 180nm) / hole generation layer (PCGL, 90nm) / hole transport layer (34nm) / electron blocking layer (25nm) / light-emitting layer (GH:GD, 35nm) / hole blocking layer (5nm) / electron transport layer (30nm) / electron injection layer (2nm) / cathode (13nm) / capping layer (60nm). The two light-emitting layers have the same structure, and the GH doping concentration in the light-emitting layer is 88-96%, and the GD doping concentration is 4-12%.

[0120] Structure 22 in Table 2 represents an embodiment of an organic electroluminescent device comprising two stacked light-emitting functional layers between the anode and cathode, each of which is a dual-emitting-layer structure, namely including a first light-emitting layer (EML1) and a light-emitting modulation layer (second light-emitting layer EML2). Its specific structure is represented as: Anode / Hole injection layer (10nm) / Hole transport layer (15nm) / Electron blocking layer (10nm) / EML1 (GH1:PGD, 30nm) / EML2 (GH2:FGD, 5nm) The light-emitting layer consists of a hole blocking layer (5nm), an electron transport layer (10nm), an electron generation layer (NCGL, 180nm), a hole generation layer (PCGL, 90nm), a hole transport layer (34nm), an electron blocking layer (25nm), an EML1 (GH1:PGD, 30nm), an EML2 (GH2:FGD, 5nm), a hole blocking layer (5nm), an electron transport layer (30nm), an electron injection layer (2nm), a cathode (13nm), and a capping layer (60nm). The light-emitting layer contains GH1 with a doping concentration of 88–96%, PGD with a doping concentration of 4–12%, GH2 with a doping concentration of 98–99.5%, and FGD with a doping concentration of 0.5–2%. GH1 and GH2 are made of the same material.

[0121] Structure 23 in Table 2 represents an embodiment where an organic electroluminescent device includes two stacked light-emitting functional layers between the anode and cathode, and each light-emitting functional layer includes a first light-emitting layer and a light-emitting modulation layer, with the light-emitting modulation layer being an electron blocking layer. Its specific structure is shown as: Anode / Hole injection layer (10nm) / Hole transport layer (15nm) / Electron blocking layer (electron blocking material: FGD, 10nm) / Light-emitting layer (GH:GD, 35nm) / Hole blocking layer (5nm) / Electron transport layer (10nm) / Electron generation layer (NCGL, 180nm) / Hole injection layer (10nm) / Electron generation layer (NCGL, 180nm) / Electron emission layer (1 ... The structure consists of a hole generation layer (PCGL, 90nm), a hole transport layer (34nm), an electron blocking layer (electron blocking material: FGD, 25nm), an emissive layer (GH:GD, 35nm), a hole blocking layer (5nm), an electron transport layer (30nm), an electron injection layer (2nm), a cathode (13nm), and a capping layer (60nm). In the emissive layer, the GH doping concentration is 88–96%, and the GD doping concentration is 4–12%. In the electron blocking layer, the electron blocking material doping concentration is 98–99.5%, and the FGD doping concentration is 0.5–2%.

[0122] As shown in Table 2, for green phosphorescent light-emitting devices, when both light-emitting functional layers adopt a double-emitting-layer structure, the efficiency of the organic electroluminescent device is improved by 2% and the device lifetime is improved by 10% compared to the single-emitting-layer structure. Furthermore, adopting a double-emitting-layer structure for both functional layers can reduce the optimal CIEx of the green phosphorescent device from 0.20 to 0.19. When both light-emitting functional layers include a first light-emitting layer, and an electron blocking layer forms a light-regulating layer, the efficiency of the organic electroluminescent device is improved by 2% and the device lifetime is improved by 10% compared to the single-emitting-layer structure. Moreover, doping the electron blocking layer with a second guest material (such as a fluorescent material) can keep the other layers unchanged. This approach offers advantages over existing... Figure 1 The mass production structure shown has fewer modifications and is easier to implement in mass production.

[0123] It is understood that for red phosphorescent devices and blue phosphorescent devices, the structure design of the light-emitting functional layer described in the embodiments of this disclosure can further improve the device efficiency and lifespan compared to the single light-emitting layer structure. Since the principle is the same, it will not be described again here.

[0124] It is understood that the specific composition of the first host material, the first guest material, the second host material, and the second guest material is not particularly limited in this invention. Those skilled in the art can select and adjust them according to actual needs, as long as the above materials meet the requirements of the corresponding energy level relationship and charge transport characteristics.

[0125] A second aspect of this disclosure provides a display panel including the aforementioned organic electroluminescent device.

[0126] Optionally, the display panel includes a first-color organic light-emitting device, a second-color organic light-emitting device, and a third-color organic light-emitting device, wherein at least one of the first-color organic light-emitting device, the second-color organic light-emitting device, and the third-color organic light-emitting device is the organic light-emitting device.

[0127] For example, the first color is red, the second color is green, and the third color is blue. It is understood that the first, second, and third colors can also be other colors.

[0128] For example, at least one of the first-color organic light-emitting device, the second-color organic light-emitting device, and the third-color organic light-emitting device is a fluorescent organic light-emitting device. For the fluorescent organic light-emitting device, the embodiment described above, in which the first guest material is the fluorescent material, can be used.

[0129] For example, at least one of the first-color organic light-emitting device, the second-color organic light-emitting device, and the third-color organic light-emitting device is a phosphorescent organic light-emitting device. For the phosphorescent organic light-emitting device, the embodiment described above, in which the first guest material is a phosphorescent material, can be adopted.

[0130] For example, the display panel can be applied to devices with display functions such as mobile phones, computer monitors, tablet computers, televisions, and advertising screens, which will not be listed in detail here. The beneficial effects of the display device are described in detail in the above method embodiments, and will not be repeated here.

[0131] A third aspect of this disclosure provides a display device including a display panel as shown above.

[0132] Obviously, the above embodiments of this disclosure are merely examples for clearly illustrating this disclosure, and are not intended to limit the implementation of this disclosure. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all implementation methods here. Any obvious variations or modifications derived from the technical solutions of this disclosure are still within the protection scope of this disclosure.

Claims

1. An organic electroluminescent device, characterized in that, include: An anode, a cathode, and at least one light-emitting functional layer located between the anode and the cathode; The light-emitting functional layer includes a first light-emitting layer and a light-emitting adjustment layer stacked sequentially. The first light-emitting layer includes a first host material and a first object material; The light-emitting modulation layer includes a second host material and a second object material; The first subject material, the first object material, the second subject material, and the second object material satisfy: T1 D1 >T1 H1 >T1 H2 And T1 D2 >T1 H1 >T1 H2 The first guest material and the second guest material are fluorescent materials. The electron mobility and hole mobility of the first host material are of the same order of magnitude. The ratio of the electron mobility and hole mobility of the second host material is greater than a first preset value. The material selection and structural setting of the light-emitting functional layer are such that: electrons and holes recombine in the first light-emitting layer to form excitons, triplet excitons are transferred from the first light-emitting layer to the light-emitting modulation layer, and singlet excitons are generated in the light-emitting modulation layer through triplet-triplet annihilation. or The first subject material, the first object material, the second subject material, and the second object material satisfy: T1 H1 >T1 D1 >T1 D2 And T1 H2 >T1 D1 >T1 D2 The first guest material is a phosphorescent material, the spectral width of the emission spectrum of the second guest material is smaller than the spectral width of the emission spectrum of the first guest material, and the emission spectrum of the second guest material overlaps with the emission spectrum of the first guest material. During the emission process, the triplet excitons of the first guest material transfer energy to the second guest material through Foster energy transfer. Among them, T1 H1 T1 represents the triplet energy level of the first host material. H2 T1 represents the triplet energy level of the second host material. D1 T1 represents the triplet energy level of the first guest material. D2 This represents the triplet energy level of the second guest material.

2. The organic electroluminescent device according to claim 1, characterized in that, When the first guest material and the second guest material are fluorescent materials, the first guest material and the second guest material are different, and the first host material, the first guest material, the second host material, and the second guest material satisfy the following: |HOMO H2 ∣≥∣HOMO D1 |>|HOMO H1 |, and |LUMO H1 |≤|LUMO D2 |<|LUMO H2 |, of which, HOMO H1 This indicates that the highest occupied molecular orbital energy level of the first host material is HOMO. H2 This indicates that the highest occupied molecular orbital energy level of the second host material is HOMO. D1 This indicates that the highest occupied molecular orbital energy level of the first guest material is LUMO. H1 LUMO represents the lowest unoccupied molecular orbital energy level of the first host material. H2 LUMO represents the lowest unoccupied molecular orbital energy level of the second host material. D2 This represents the lowest unoccupied molecular orbital energy level of the second guest material.

3. The organic electroluminescent device according to claim 1, characterized in that, When the first guest material and the second guest material are fluorescent materials, the emission spectra of the first guest material and the second guest material satisfy the following: 0nm≤Δλ≤2nm and 0nm≤ΔFWHM≤3nm, where Δλ represents the absolute value of the difference between the peak wavelength of the emission spectrum of the first guest material and the peak wavelength of the emission spectrum of the second guest material, and ΔFWHM represents the absolute value of the difference between the half-width at half maximum (WHM) of the emission spectrum of the first guest material and the half-width at half maximum (WHM) of the emission spectrum of the second guest material.

4. The organic electroluminescent device according to claim 1, characterized in that, When the first guest material and the second guest material are fluorescent materials, the emission spectra of the first guest material and the second guest material satisfy the following: 2nm≤Δλ≤5nm and 3nm≤ΔFWHM≤10nm, where Δλ represents the difference between the peak wavelength of the emission spectrum of the first guest material and the peak wavelength of the emission spectrum of the second guest material, and ΔFWHM represents the absolute value of the difference between the half-width at half maximum (WHM) of the emission spectrum of the first guest material and the half-width at half maximum (WHM) of the emission spectrum of the second guest material.

5. The organic electroluminescent device according to claim 1, characterized in that, When the first guest material and the second guest material are fluorescent materials, the thickness of the first luminescent layer is 3~10nm, and the thickness of the luminescence modulation layer is 10~17nm.

6. The organic electroluminescent device according to claim 1, characterized in that, When the first object material is a phosphorescent material, the light-emitting adjustment layer is an electron blocking layer, a hole blocking layer, or a second light-emitting layer.

7. The organic electroluminescent device according to claim 6, characterized in that, When the first guest material is a phosphorescent material, the second guest material is a fluorescent material, a thermally activated delayed fluorescence material, or a phosphorescent material.

8. The organic electroluminescent device according to claim 6, characterized in that, When the light-emitting adjustment layer is the second light-emitting layer, the thickness of the first light-emitting layer is 30~34nm, and the thickness of the light-emitting adjustment layer is 1~5nm.

9. The organic electroluminescent device according to claim 6, characterized in that, When the light-emitting modulation layer is an electron blocking layer or a hole blocking layer, the volume percentage of the second host material is 98-99.5%, and the volume percentage of the second guest material is 0.5-2%.

10. The organic electroluminescent device according to claim 1, characterized in that, The number of light-emitting functional layers is at least two. Among two adjacent light-emitting functional layers, the light-emitting functional layer closer to the anode is referred to as the first light-emitting functional layer and the light-emitting functional layer closer to the cathode is referred to as the second light-emitting functional layer. At least one of the first light-emitting functional layer and the second light-emitting functional layer includes a first light-emitting layer and a light-emitting adjustment layer that are stacked sequentially.

11. A display panel, characterized in that, Including the organic electroluminescent device as described in any one of claims 1 to 10.

12. The display panel according to claim 11, characterized in that, The display panel includes a first-color organic light-emitting device, a second-color organic light-emitting device, and a third-color organic light-emitting device, wherein at least one of the first-color organic light-emitting device, the second-color organic light-emitting device, and the third-color organic light-emitting device is the organic light-emitting device.

13. A display device, characterized in that, Includes the display panel as described in claim 11 or 12.

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