Luminescent material, luminescent device, display panel and display device

Abstract

The invention discloses a light-emitting material, a light-emitting device, a display panel and a display device. The light-emitting material comprises a thermally activated delayed fluorescent material. The thermally activated delayed fluorescent material can be applied to a light-emitting device, Se heavy atoms in the thermally activated delayed fluorescent material replace original halogenated heavy atoms, and the Se heavy atoms are combined with unsaturated heteroatoms and a traditional photochromic material; the material has the TADF emission performance of emitting red fluorescence under the excitation of visible light and the performance of increasing the luminous efficiency after being irradiated by an ultraviolet lamp, the luminous efficiency is improved, and the luminous life is prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of display technology, and in particular relates to a luminescent material, a luminescent device, a display panel and a display device. Background Art

[0002] With the increasing number of smart devices, the application of display screens is also becoming more and more extensive. The luminescent materials in the display screen are important materials in the display and have an important influence on the luminescent effect of the display screen, such as luminescent materials and thermally activated delayed fluorescence (TADF) materials. After the luminescent material absorbs photons (or electromagnetic waves), the electrons transition from the lower energy ground state to the higher energy excited state, and then these electrons return to the lower energy ground state and emit photons in the process. For example, some luminescent materials can emit longer wavelength light after absorbing shorter wavelength light. Thermally activated delayed fluorescence materials are the third generation of organic light-emitting materials developed after organic fluorescent materials and organic phosphorescent materials. They have great application prospects in many fields such as organic light-emitting diodes, anti-counterfeiting encryption, and analysis and detection. Compared with traditional fluorescent materials, TADF materials can utilize triplet excitons through the reverse intersystem crossing (RISC) process from T1 to the lowest singlet excited state (S1), that is, they can simultaneously utilize singlet excited states and triplet excited states, so they have a theoretical internal quantum efficiency of 100%. Compared with traditional phosphorescent materials, TADF materials are pure organic materials, do not contain heavy metals, are lower in cost and more environmentally friendly. Therefore, the development of new TADF materials is of great significance. Summary of the invention

[0003] The purpose of the embodiments of the present invention is to provide a light-emitting material, a light-emitting device, a display panel and a display apparatus, so as to solve the problem that the light-emitting efficiency of the light-emitting device is low.

[0004] In a first aspect, an embodiment of the present invention provides a luminescent material, including: a thermally activated delayed fluorescent material, wherein the thermally activated delayed fluorescent material has a structural formula of:

[0005]

[0006] Wherein, R1 and R3 are selected from alkyl, aromatic, and heterocyclic rings;

[0007] R2 is selected from -(CH2)n-, an aromatic group, a heterocycle, and a single bond, and n is a positive integer.

[0008] Optionally, the thermally activated delayed fluorescent material has a structural formula selected from structural formula a1 and structural formula a2, and structural formula a1 and structural formula a2 are:

[0009]

[0010] Structural formula a1;

[0011]

[0012] Structural formula a2.

[0013] In a second aspect, an embodiment of the present invention provides a light emitting device, including:

[0014] The luminescent materials described in the above embodiments.

[0015] Optionally, the light emitting device comprises:

[0016] A first light-emitting layer and a second light-emitting layer, wherein the first light-emitting layer comprises the light-emitting material, and the second light-emitting layer is used for emitting light having a second wavelength;

[0017] The thermally activated delayed fluorescent material in the first light emitting layer emits light having a first wavelength while absorbing light having a second wavelength, the first wavelength being greater than the second wavelength.

[0018] Optionally, the second wavelength is in the range of 630-700 nm; and / or

[0019] The second wavelength is in the range of 540-620 nm.

[0020] Optionally, the light emitting device further comprises:

[0021] An electron injection layer, a first electron transport layer, a first hole transport layer, and a hole injection layer are stacked, and the second light-emitting layer is located between the first electron transport layer and the first hole transport layer.

[0022] Optionally, the second light-emitting layer includes: a third light-emitting layer and a fourth light-emitting layer, and the light-emitting device further includes an electron generating layer and a hole generating layer;

[0023] The third light-emitting layer is located between the first electron transport layer and the hole generating layer, and the fourth light-emitting layer is located between the first hole transport layer and the electron generating layer.

[0024] Optionally, the light emitting device further comprises:

[0025] A second electron transport layer, wherein the second electron transport layer is disposed between the electron generating layer and the fourth light emitting layer; and / or

[0026] A second hole transport layer is disposed between the hole generating layer and the third light emitting layer.

[0027] In a third aspect, an embodiment of the present invention provides a display panel, including:

[0028] The light emitting device described in the above embodiments.

[0029] In a fourth aspect, an embodiment of the present invention provides a display device, including:

[0030] The display panel described in the above embodiments.

[0031] The luminescent material in the embodiment of the present invention includes: a thermally activated delayed fluorescent material, which can be applied to a light-emitting device. The Se heavy atom effect replaces the original halogenated heavy atom in the thermally activated delayed fluorescent material, and is combined with unsaturated heteroatoms and traditional photochromic materials. The material has both the TADF emission performance of emitting red fluorescence under visible light excitation and the performance of increasing luminous efficiency after ultraviolet light irradiation, thereby improving the luminous efficiency and increasing the luminous life. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a structural schematic diagram of a light emitting device in an embodiment of the present invention;

[0033] Figure 2 The H NMR spectrum of the prepared compound Me-Se-SP-n of structural formula a1;

[0034] Figure 3 This is the H NMR spectrum of the prepared compound Ph-Se-SP-n of structural formula a2.

[0035] Reference numerals

[0036] A first light emitting layer 10;

[0037] A third light-emitting layer 21; a fourth light-emitting layer 22;

[0038] Electron injection layer 30; first electron transport layer 31; second electron transport layer 32;

[0039] a hole injection layer 40;

[0040] A first hole transport layer 41; a second hole transport layer 42;

[0041] Electron generation layer 50; hole generation layer 51;

[0042] Cathode 60. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable under appropriate circumstances, so that the embodiments of the present invention can be implemented in an order other than those illustrated or described herein. In addition, the term "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0045] The luminescent material of the embodiment of the present invention includes: a thermally activated delayed fluorescent material, and the structural formula of the thermally activated delayed fluorescent material is:

[0046]

[0047] Wherein, R1 and R3 are selected from alkyl, aromatic, and heterocyclic rings;

[0048] R2 is selected from -(CH2)n-, an aromatic group, a heterocycle, and a single bond, and n is a positive integer.

[0049] The luminescent material in the embodiment of the present invention includes: a thermally activated delayed fluorescent material, which can be applied to a light-emitting device. The Se heavy atom effect replaces the original halogenated heavy atom in the thermally activated delayed fluorescent material, and is combined with unsaturated heteroatoms and traditional photochromic materials. The material has both the TADF emission performance of emitting red fluorescence under visible light excitation and the performance of increasing luminous efficiency after ultraviolet light irradiation, thereby improving the luminous efficiency and increasing the luminous life.

[0050] In some embodiments, the thermally activated delayed fluorescent material has a structural formula selected from structural formula a1 and structural formula a2, and structural formula a1 and structural formula a2 may be:

[0051]

[0052] Structural formula a1;

[0053]

[0054] Structural formula a2.

[0055] The invention discloses a method for preparing a thermally activated delayed fluorescent material.

[0056] Preparation of Se-SP-n compound:

[0057] Step 1: Under nitrogen protection, 1 mol of compound 1 was dissolved in THF, 1.2 mol of selenoether was slowly added (about 20 min) under ice-water bath conditions, and the reaction was carried out at room temperature for 8 h (TLC spot plate was used to monitor the reaction progress), and column chromatography was used for separation and purification to obtain compound 2;

[0058] Step 2: Under nitrogen protection, 1 mol of compound 2 and 1.2 mol of iodo alcohol were dissolved in ethanol, heated to 70°C and stirred for 6 h (TLC spot plate was used to monitor the reaction progress), and separated and purified by column chromatography to obtain compound 3;

[0059] Step 3: Under nitrogen protection, 1 mol of compound 4 and 2 mol of R3-OH were added to 20 ml of DMF (N,N-dimethylformamide) solvent, EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide) and DMAP (4-dimethylaminopyridine) were added, and the mixture was heated under reflux with stirring for 12 h (TLC spot plate was used to monitor the reaction progress), and after rotary evaporation to remove 95% of the solvent, the mixture was separated and purified by column chromatography to obtain compound 5;

[0060] Step 4: Under nitrogen protection, 0.1 mol of compound 3 and 0.11 mol of compound 5 were added to 10 ml of DMF solvent, heated to reflux for 6 h (TLC spot plate was used to detect the reaction progress), and after rotary evaporation to remove 95% of the solvent, column chromatography was used for separation and purification to obtain Se-SP-n. The specific reaction process is as follows:

[0061]

[0062] The compounds having the structural formula a1 and the structural formula a2 can be prepared by the above method.

[0063] The preparation method of the Me-Se-SP-n compound having the structural formula a1 is that the R1 group of the reactant in the above-mentioned preparation step reaction process is selected as a methyl group, the R2 group is selected as a methylene group (-CH2-), and the R3 group is selected as a methyl group. The preparation method of the Ph-Se-SP-n compound having the structural formula a2 is that the R1 group of the reactant in the above-mentioned preparation step reaction process is selected as a phenyl group, the R2 group is selected as a methylene group (-CH2-), and the R3 group is selected as a methyl group. The preparation routes of the two compounds Me-Se-SP-n and Ph-Se-SP-n can refer to the above-mentioned preparation process.

[0064] The prepared compound Me-Se-SP-n in the structural formula a1 is as follows Figure 2As shown, its nuclear magnetic hydrogen spectrum data are: 1H NMR (500MHz, Chloroform) δ7.68, 7.21, 6.92, 6.65, 6.65, 6.08, 5.82, 5.70, 5.36, 4.07, 3.90, 3.85, 3.67, 3.49, 1.35. The prepared compound Ph-Se-SP-n in the structural formula a2 has the nuclear magnetic hydrogen spectrum data as shown Figure 3 shown.

[0065] The fluorescence emission / excitation spectrum and delayed fluorescence emission / excitation spectrum (delay time = 0.1 ms) data results of the Me-Se-SP-n and Ph-Se-SP-n compound materials of the present invention are shown in Table 1.

[0066] Table 1

[0067]

[0068] As can be seen from Table 1, Me-Se-SP-n and Ph-Se-SP-n compound materials can absorb yellow-green light around 580nm and emit red light around 640nm.

[0069] Device structure such as Figure 1 As shown, the thermally activated delayed fluorescent material of the present invention can be applied to the first light-emitting layer 10 between the cathode and the encapsulation layer. This greatly facilitates the selection of materials for the second red light-emitting layer, and different light-emitting materials can be selected for the third and fourth light-emitting layers.

[0070] One of the third and fourth light-emitting layers in the second light-emitting layer can select a deep red material (can be EML1 or EML2, a mixed material of EML1 and EML2, EML1 can represent a red light-emitting material, EML2 can represent another red light-emitting material, can include two or more materials of a main material and a doping material, and the optimal light-emitting wavelength can be between 630nm and 700nm); the other light-emitting layer in the third and fourth light-emitting layers in the second light-emitting layer can select a green / yellow / orange material with higher efficiency (can be EML1 or EML2, a mixed material of EML1 and EML2, can include two or more materials of a main material and a doping material, and the optimal light-emitting wavelength can be greater than 540nm and less than 620nm). The main materials in the third and fourth light-emitting layers can be the same or different, and the doping materials can be different. The presence of the first light-emitting layer can absorb the photon energy located near its optimal excitation position (i.e., the optimal absorbable light wavelength) of 580nm, and convert it into a longer wavelength photon form for emission (the fluorescent material of the present invention can emit light with a wavelength of 640nm), thereby improving the light-emitting efficiency. The efficiency of the tandem green light doped materials currently developed is much greater than the red light efficiency (for example, green light efficiency > 2 times red light efficiency). Through the presence of the first light-emitting layer, high-efficiency green light can be effectively utilized, thereby improving the red light efficiency.

[0071] The third light-emitting layer and the fourth light-emitting layer can both be orange-red materials, can be mixed light-emitting materials, can be mixed materials of EML1 and EML2, can contain two or more materials of main material and doping material, the main material and doping material in the third light-emitting layer and the fourth light-emitting layer can be the same or different, and the optimal light-emitting wavelength of the material can be 580-640nm. At present, the design of light-emitting materials needs to take into account many considerations such as color purity, efficiency, life, capacitance, etc., which poses a great challenge to the selection of materials. By introducing the first light-emitting layer, the color can be corrected, the requirements for the color purity of the material itself can be reduced, and materials with other properties such as efficiency are selected, which greatly facilitates the selection of red light-emitting materials.

[0072] The light emitting device according to the embodiment of the present invention comprises:

[0073] The luminescent materials described in the above embodiments.

[0074] The luminescent materials in the embodiments of the present invention include: thermally activated delayed fluorescent materials, which can be applied to light-emitting devices. A photoluminescent layer having the fluorescent material can be added to the top of the device, which can re-emit long-wavelength light based on the light emitted by the device, thereby effectively improving and regulating the efficiency of the device and increasing the service life of the device.

[0075] In an embodiment of the present invention, Figure 1As shown, the light emitting device may include:

[0076] The first light-emitting layer 10 and the second light-emitting layer, the first light-emitting layer 10 includes a light-emitting material, the second light-emitting layer is used to emit light with a second wavelength, the thermally activated delayed fluorescent material in the first light-emitting layer 10 emits light with a first wavelength when absorbing the light with the second wavelength, and the first wavelength is greater than the second wavelength. The first light-emitting layer 10 can be a photoluminescent layer, and during the light-emitting process of the second light-emitting layer in the light-emitting device, the light emitted by the second light-emitting layer can be absorbed by the thermally activated delayed fluorescent material in the first light-emitting layer 10, and the thermally activated delayed fluorescent material emits light with a longer wavelength when absorbing the light with the second wavelength, thereby improving the light-emitting efficiency.

[0077] In some embodiments, the second wavelength may be in the range of 630-700 nm, for example, the second wavelength may be 630 nm, 650 nm, 680 nm or 700 nm, and the specific wavelength may also be selected as needed.

[0078] The second wavelength may be in the range of 540-620 nm. For example, the second wavelength may be in the range of 540 nm, 580 nm, 600 nm or 620 nm. The specific wavelength may also be selected as required.

[0079] In an embodiment of the present invention, the light emitting device may further include:

[0080] The electron injection layer 30, the first electron transport layer 31, the first hole transport layer 41, and the hole injection layer 40 are stacked, and the second light-emitting layer is located between the first electron transport layer 31 and the first hole transport layer 41. The first light-emitting layer 10 and the second light-emitting layer 20 can be stacked, the electron injection layer 30 and the first electron transport layer 31 can be arranged between the first light-emitting layer 10 and the second light-emitting layer, the second light-emitting layer emits light with a second wavelength, and the thermally activated delayed fluorescent material in the first light-emitting layer 10 emits light with a first wavelength when absorbing the light with the second wavelength. The first wavelength is greater than the second wavelength, thereby improving the luminous efficiency.

[0081] In some embodiments of the present invention, the light emitting device may further include:

[0082] The anode and the cathode, the cathode can be arranged on the side of the electron injection layer 30 away from the first electron transport layer 31, and the anode can be arranged on the side of the hole injection layer 40 away from the first hole transport layer 41. The second light-emitting layer can be made to emit light by driving the anode and the cathode. The thermally activated delayed fluorescent material in the first light-emitting layer 10 absorbs the light emitted by the second light-emitting layer and emits light with a longer wavelength, thereby improving the light-emitting efficiency.

[0083] In an embodiment of the present invention, the second light-emitting layer may include: a third light-emitting layer 21 and a fourth light-emitting layer 22, and the light-emitting device may further include an electron generation layer 50 and a hole generation layer 51, the third light-emitting layer 21 is located between the first electron transport layer 31 and the hole generation layer 51, and the fourth light-emitting layer 22 is located between the first hole transport layer 41 and the electron generation layer 50. The electrons generated by the electron generation layer 50 and the holes generated by the hole generation layer 51 can make the third light-emitting layer 21 and the fourth light-emitting layer 22 emit light.

[0084] In some embodiments, the light emitting device may further include:

[0085] The second electron transport layer 32 may be disposed between the electron generation layer 50 and the fourth light emitting layer 22 .

[0086] In some embodiments, the light emitting device may further include:

[0087] The second hole transport layer 42 may be disposed between the hole generating layer 51 and the third light emitting layer 21 .

[0088] In some embodiments, the light emitting device may further include:

[0089] The first electron blocking layer 71 may be disposed between the first hole transport layer 41 and the fourth light emitting layer 22 .

[0090] The second electron blocking layer 72 may be disposed between the second hole transport layer 42 and the third light emitting layer 21 .

[0091] In some other embodiments, the light emitting device may further include:

[0092] The first hole blocking layer 81 may be disposed between the first electron transport layer 31 and the third light emitting layer 21 .

[0093] The second hole blocking layer 82 may be disposed between the second electron transport layer 32 and the fourth light emitting layer 22 .

[0094] In some embodiments, the light emitting device may further include:

[0095] The cathode 60 may be disposed on a side of the electron injection layer 30 away from the second light emitting layer 20 , and the cathode 60 may be a polyimide layer.

[0096] The first light-emitting layer 10 can be arranged on a side of the cathode 60 away from the electron injection layer 30. The light with the second wavelength emitted by the second light-emitting layer is absorbed by the thermally activated delayed fluorescent material in the first light-emitting layer 10. The thermally activated delayed fluorescent material in the first light-emitting layer 10 emits light with the first wavelength while absorbing the light with the second wavelength. The first wavelength is greater than the second wavelength. The thermally activated delayed fluorescent material in the first light-emitting layer 10 absorbs the light emitted by the second light-emitting layer and emits light with a longer wavelength, which will enable the low-wavelength energy to be converted and utilized, thereby improving the luminous efficiency.

[0097] Light-emitting device performance: Figure 1 In the structure, the third light-emitting layer and the fourth light-emitting layer can both have an emission wavelength of 615 nm, and are made of high-efficiency orange-red materials. The thickness of the three can be adjusted to be basically consistent with CIEX through the optical microcavity effect, and the efficiency is compared, as shown in Table 2.

[0098] Table 2

[0099]

[0100] It can be seen from Table 2 that the fluorescent material in the present invention can improve the luminous efficiency of the light-emitting device and increase the service life.

[0101] A display panel according to an embodiment of the present invention includes:

[0102] The light emitting device described in the above embodiments.

[0103] The display panel having the light emitting device described in the above embodiment has high light emitting efficiency and long service life.

[0104] A display device according to an embodiment of the present invention includes:

[0105] The display panel described in the above embodiments.

[0106] The display device having the display panel described in the above embodiment has high luminous efficiency and long service life.

[0107] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A luminescent material, characterized in that: include: Thermally activated delayed fluorescent material, the structural formula of the thermally activated delayed fluorescent material is: Wherein, R1 and R3 are selected from alkyl, aromatic, and heterocyclic rings; R2 is selected from -(CH2)n-, an aromatic group, a heterocycle, and a single bond, and n is a positive integer.

2. The luminescent material according to claim 1, characterized in that The structural formula of the thermally activated delayed fluorescent material is selected from structural formula a1 and structural formula a2, and structural formula a1 and structural formula a2 are:

3. A light emitting device, characterized in that: include: The luminescent material according to any one of claims 1 to 2.

4. The light emitting device according to claim 3, characterized in that: The light emitting device comprises: A first light-emitting layer and a second light-emitting layer, wherein the first light-emitting layer comprises the light-emitting material, and the second light-emitting layer is used for emitting light having a second wavelength; The thermally activated delayed fluorescent material in the first light emitting layer emits light having a first wavelength while absorbing light having a second wavelength, the first wavelength being greater than the second wavelength.

5. The light emitting device according to claim 4, characterized in that: The second wavelength is in the range of 630-700 nm; and / or The second wavelength is in the range of 540-620 nm.

6. The light emitting device according to claim 4, characterized in that: The light emitting device further comprises: An electron injection layer, a first electron transport layer, a first hole transport layer, and a hole injection layer are stacked, and the second light-emitting layer is located between the first electron transport layer and the first hole transport layer.

7. The light emitting device according to claim 6, characterized in that: The second light-emitting layer includes: a third light-emitting layer and a fourth light-emitting layer, and the light-emitting device further includes an electron generating layer and a hole generating layer; The third light-emitting layer is located between the first electron transport layer and the hole generating layer, and the fourth light-emitting layer is located between the first hole transport layer and the electron generating layer.

8. The light emitting device according to claim 7, characterized in that: Also includes: A second electron transport layer, wherein the second electron transport layer is disposed between the electron generating layer and the fourth light emitting layer; and / or A second hole transport layer is disposed between the hole generating layer and the third light emitting layer.

9. A display panel, characterized in that: include: The light emitting device according to any one of claims 3 to 8.

10. A display device, characterized in that: include: The display panel as claimed in claim 9.

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