Light emitting material, light emitting device, display panel, and display device

Abstract

The application discloses a luminescent material, a luminescent device, a display panel and a display device, and relates to the technical field of luminescent materials.The luminescent material comprises a thermally activated delayed fluorescence material.The thermally activated delayed fluorescence material can be applied to a luminescent device, the Se heavy atom effect replaces the original halogenated heavy atom in the thermally activated delayed fluorescence material, and the thermally activated delayed fluorescence material is combined with an unsaturated heteroatom and a traditional photochromic material, so that the material has the TADF emission performance of emitting red fluorescence under visible light excitation and the performance of increasing luminous efficiency after ultraviolet lamp irradiation, the luminous efficiency is improved, and the luminous life is improved.

Description

Technical Field

[0001] This invention belongs to the field of display technology, specifically relating to a light-emitting material, a light-emitting device, a display panel, and a display apparatus. Background Technology

[0002] With the increasing application of smart devices, displays are also becoming more widely used. Light-emitting materials in displays are crucial, significantly impacting their luminescence performance. Examples include luminescent materials and thermally activated delayed fluorescence (TADF) materials. In luminescent materials, after absorbing photons (or electromagnetic waves), electrons transition from a lower-energy ground state to a higher-energy excited state. These electrons then return to the lower-energy ground state, emitting photons in the process. For instance, some luminescent materials can absorb shorter wavelengths of light but emit longer wavelengths. Thermally activated delayed fluorescence (TADF) materials are the third generation of organic light-emitting materials, following organic fluorescent and organic phosphorescent materials, and have enormous application potential in fields such as organic light-emitting diodes (OLEDs), anti-counterfeiting encryption, and analytical detection. Compared to traditional fluorescent materials, TADF materials can utilize triplet excitons through a reverse systematic crossover (RISC) process from T1 to the lowest singlet excited state (S1), meaning they can simultaneously utilize both singlet and triplet excited states, thus theoretically achieving 100% internal quantum efficiency. Compared to traditional phosphorescent materials, TADF materials are purely organic, contain no heavy metals, and are more cost-effective and environmentally friendly. Therefore, the development of novel TADF materials is of great significance. Summary of the Invention

[0003] The purpose of this invention is to provide a luminescent material, a luminescent device, a display panel, and a display apparatus to solve the problem of low luminous efficiency of the luminescent device.

[0004] In a first aspect, embodiments of the present invention provide a luminescent material, comprising: a thermally activated delayed fluorescence material, wherein the thermally activated delayed fluorescence material has the following structural formula:

[0005]

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

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

[0008] Optionally, the structural formula of the thermally activated delayed fluorescence material is selected from structural formula a1 and structural formula a2, wherein structural formula a1 and structural formula a2 are:

[0009]

[0010] Structural formula a1;

[0011]

[0012] Structural formula a2.

[0013] Secondly, embodiments of the present invention provide a light-emitting device, comprising:

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

[0015] Optionally, the light-emitting device includes:

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

[0017] The thermally activated delayed fluorescent material in the first luminescent layer emits light with a first wavelength when it absorbs light with a second wavelength, the first wavelength being greater than the second wavelength.

[0018] Optionally, the second wavelength ranges from 630 to 700 nm; and / or

[0019] The second wavelength ranges from 540 to 620 nm.

[0020] Optionally, the light-emitting device further includes:

[0021] The electron injection layer, the first electron transport layer, the first hole transport layer, and the hole injection layer are stacked together, 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 generation layer, and the fourth light-emitting layer is located between the first hole transport layer and the electron generation layer.

[0024] Optionally, the light-emitting device further includes:

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

[0026] The second hole transport layer is disposed between the hole generation layer and the third light-emitting layer.

[0027] Thirdly, embodiments of the present invention provide a display panel, including:

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

[0029] Fourthly, embodiments of the present invention provide a display device, comprising:

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

[0031] The luminescent material in this embodiment of the invention includes a thermally activated delayed fluorescence material. This thermally activated delayed fluorescence material can be applied to light-emitting devices. In the thermally activated delayed fluorescence material, the original halogenated heavy atoms are replaced by the Se heavy atom effect. Combined with unsaturated heteroatoms and traditional photochromic materials, the material simultaneously possesses the TADF emission performance of emitting red fluorescence under visible light excitation and the performance of increased luminous efficiency after ultraviolet lamp irradiation, thereby improving luminous efficiency and extending luminous lifetime. Attached Figure Description

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

[0033] Figure 2 The 1H NMR spectrum of the compound Me-Se-SP-n with structural formula a1 was prepared.

[0034] Figure 3 The 1H NMR spectrum of the compound Ph-Se-SP-n with the structural formula a2 was prepared.

[0035] Figure Labels

[0036] First light-emitting layer 10;

[0037] Third light-emitting layer 21; Fourth light-emitting layer 22;

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

[0039] Hole injection layer 40;

[0040] First hole transport layer 41; Second hole transport layer 42;

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

[0042] Cathode 60. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention 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 the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention can be implemented in orders other than those illustrated or described herein. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0045] The luminescent material of this invention includes: a thermally activated delayed fluorescence material, wherein the structural formula of the thermally activated delayed fluorescence material is:

[0046]

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

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

[0049] The luminescent material in this embodiment of the invention includes a thermally activated delayed fluorescence material. This thermally activated delayed fluorescence material can be applied to light-emitting devices. In the thermally activated delayed fluorescence material, the original halogenated heavy atoms are replaced by the Se heavy atom effect. Combined with unsaturated heteroatoms and traditional photochromic materials, the material simultaneously possesses the TADF emission performance of emitting red fluorescence under visible light excitation and the performance of increased luminous efficiency after ultraviolet lamp irradiation, thereby improving luminous efficiency and extending luminous lifetime.

[0050] In some embodiments, the structural formula of the thermally activated delayed fluorescence material is selected from structural formula a1 and structural formula a2, and structural formula a1 and structural formula a2 can be:

[0051]

[0052] Structural formula a1;

[0053]

[0054] Structural formula a2.

[0055] The present invention relates to a method for preparing thermally activated delayed fluorescence materials.

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

[0057] Step 1: Under nitrogen protection, 1 mol of compound 1 was dissolved in THF, and 1.2 mol of selenium ether was slowly added (about 20 min) under ice-water bath conditions. The reaction was carried out at room temperature for 8 h (the reaction progress was monitored by TLC). The compound 2 was obtained by column chromatography.

[0058] Step 2: Under nitrogen protection, 1 mol of compound 2 and 1.2 mol of iodoethanol were dissolved in ethanol, heated to 70°C and stirred for 6 h (the reaction progress was detected by TLC), 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, followed by the addition of EDC (1-ethyl-(3-dimethylaminopropyl)carbodiimide) and DMAP (4-dimethylaminopyridine). The mixture was heated under reflux and stirred for 12 h (the reaction progress was monitored by TLC). After removing 95% of the solvent by rotary evaporation, the mixture was 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, and the mixture was heated under reflux for 6 h (the reaction progress was monitored by TLC). After removing 95% of the solvent by rotary evaporation, the mixture was purified by column chromatography to obtain Se-SP-n. The specific reaction process is as follows:

[0061]

[0062] Compounds with structural formulas a1 and a2 can be prepared using the above method.

[0063] The preparation method for Me-Se-SP-n compounds with structural formula a1 involves selecting methyl as the R1 group, methylene (-CH2-) as the R2 group, and methyl as the R3 group in the reaction steps described above. Similarly, the preparation method for Ph-Se-SP-n compounds with structural formula a2 involves selecting phenyl as the R1 group, methylene (-CH2-) as the R2 group, and methyl as the R3 group in the reaction steps described above. The preparation routes for both Me-Se-SP-n and Ph-Se-SP-n compounds can be found in the above-described preparation process.

[0064] The compound Me-Se-SP-n with structural formula a1 was prepared, such as Figure 2As shown, its 1H NMR data are: 1H NMR (500MHz, Chloroform) δ 7.68, 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 compound Ph-Se-SP-n with structure a2 prepared has the following 1H NMR data: Figure 3 As shown.

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

[0066] Table 1

[0067]

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

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

[0070] One of the third and fourth luminescent layers in the second luminescent layer can be a deep red material (which can be EML1 or EML2, or a mixture of EML1 and EML2; EML1 can represent one red luminescent material, and EML2 can represent another red luminescent material; it can contain two or more materials, including a host material and dopant materials; the optimal emission wavelength can be between 630nm and 700nm). The other luminescent layer in the third and fourth luminescent layers in the second luminescent layer can be a more efficient green / yellow / orange material (which can be EML1 or EML2, or a mixture of EML1 and EML2; it can contain two or more materials, including a host material and dopant materials; the optimal emission wavelength can be greater than 540nm and less than 620nm). The host materials in the third and fourth luminescent layers can be the same or different, and the dopant materials can be different. The presence of the first luminescent layer can absorb photon energy located near its optimal excitation position (i.e., the optimal absorbable light wavelength) of 580nm and convert it into photons with longer wavelengths for emission (the fluorescent material of this invention can emit light with a wavelength of 640nm), thereby improving luminous efficiency. The efficiency of the green light doped material developed at this stage is much greater than that of the red light (e.g., green light efficiency > 2 times red light efficiency). Through the presence of the first light-emitting layer, the high-efficiency green light can be effectively utilized, thereby improving the red light efficiency.

[0071] Both the third and fourth emitting layers can be orange-red materials, or they can be mixed emitting materials, or a mixture of EML1 and EML2 materials. They can contain two or more materials, including a host material and dopants. The host material and dopants in the third and fourth emitting layers can be the same or different. The optimal emission wavelength of the material can be 580-640nm. Currently, the design of emitting materials needs to simultaneously consider many factors such as color purity, efficiency, lifetime, and capacitance, which poses a significant challenge to material selection. Introducing a first emitting layer can correct the color and reduce the requirement for the material's own color purity, allowing for the selection of materials with superior efficiency and other properties, greatly facilitating the selection of red emitting materials.

[0072] The light-emitting device of this invention includes:

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

[0074] The luminescent material in this embodiment of the invention includes a thermally activated delayed fluorescence material. This thermally activated delayed fluorescence material can be applied to a light-emitting device. A photoluminescent layer with this fluorescence material can be added to the top of the device. It can emit long-wavelength light on its own after absorbing the light emitted by the device, which can effectively improve and control the device efficiency and increase the device's lifespan.

[0075] In embodiments of the present invention, such as Figure 1As shown, the light-emitting device may include:

[0076] A first light-emitting layer 10 and a second light-emitting layer, wherein the first light-emitting layer 10 includes a light-emitting material, and 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 absorbs light with the second wavelength and emits light with a first wavelength, which is longer than the second wavelength. The first light-emitting layer 10 can be a photoluminescent layer. During the luminescence process of the second light-emitting layer in the light-emitting device, the thermally activated delayed fluorescent material in the first light-emitting layer 10 can absorb the light emitted by the second light-emitting layer. The thermally activated delayed fluorescent material, upon absorbing light with the second wavelength, emits light with a longer wavelength, thereby improving luminous efficiency.

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

[0078] The second wavelength can be in the range of 540-620nm, for example, the range of the second wavelength can be 540nm, 580nm, 600nm or 620nm, and the specific wavelength can be selected as needed.

[0079] In embodiments 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 together, with the second light-emitting layer 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, and the electron injection layer 30 and the first electron transport layer 31 can be disposed 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 it absorbs 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 cathode are located on the side of the electron injection layer 30 away from the first electron transport layer 31, and the anode is located 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 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 luminous efficiency.

[0083] In embodiments of the present invention, the second light-emitting layer may include a third light-emitting layer 21 and a fourth light-emitting layer 22. The light-emitting device may further include an electron-generating layer 50 and a hole-generating layer 51. The third light-emitting layer 21 is located between the first electron transport layer 31 and the hole-generating layer 51, and the fourth light-emitting layer 22 is located between the first hole transport layer 41 and the electron-generating layer 50. Electrons generated by the electron-generating layer 50 and holes generated by the hole-generating layer 51 enable the third light-emitting layer 21 and the fourth light-emitting layer 22 to 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 can be disposed between the hole generation layer 51 and the third light emission 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 other embodiments, the light-emitting device may further include:

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

[0093] The second hole blocking layer 82 can 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 can be disposed on the side of the electron injection layer 30 away from the second light-emitting layer 20, and the cathode 60 can be a polyimide layer.

[0096] The first light-emitting layer 10 can be disposed on the side of the cathode 60 away from the electron injection layer 30. The light with a 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 a first wavelength when it absorbs the light with the second wavelength. The first wavelength is greater than the second wavelength. When the thermally activated delayed fluorescent material in the first light-emitting layer 10 absorbs the light emitted by the second light-emitting layer, it emits light with a longer wavelength, which will enable the conversion and utilization of low-wavelength energy and improve the luminous efficiency.

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

[0098] Table 2

[0099]

[0100] As shown in Table 2, the fluorescent material in this invention can improve the luminous efficiency of the light-emitting device and increase its service life.

[0101] The display panel of this 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 embodiments has high luminous efficiency and long service life.

[0104] The display device of this invention includes:

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

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

[0107] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A luminescent material, characterized by, Comprising: a thermally activated delayed fluorescence material, the thermally activated delayed fluorescence material having a structural formula selected from structural formula a1 or structural formula a2, structural formula a1 and structural formula a2 being: Formula a1; Structural Formula a2.

2. A light emitting device, characterized by Comprising: the luminescent material as claimed in claim 1.

3. The light emitting device of claim 2, wherein, the luminescent device comprising: a first luminescent layer comprising the luminescent material and a second luminescent layer for emitting light having a second wavelength; the thermally activated delayed fluorescence material in the first luminescent layer emits light having a first wavelength upon absorption of light having the second wavelength, the first wavelength being greater than the second wavelength.

4. The light emitting device of claim 3, wherein, the second wavelength ranges from 630-700 nm; and / or the second wavelength ranges from 540-620 nm.

5. The light emitting device of claim 3, wherein the first and second light emitting devices are arranged in a vertical direction. the luminescent device further comprising: a first electron transport layer, a first hole transport layer, and a hole injection layer, the second luminescent layer being located between the first electron transport layer and the first hole transport layer.

6. The light emitting device of claim 5, wherein, the second luminescent layer comprising: a third luminescent layer and a fourth luminescent layer, the luminescent device further comprising an electron generation layer and a hole generation layer; the third luminescent layer being located between the first electron transport layer and the hole generation layer, and the fourth luminescent layer being located between the first hole transport layer and the electron generation layer.

7. The light emitting device according to claim 6, characterized in that Further comprising: a second electron transport layer, the second electron transport layer being located between the electron generation layer and the fourth luminescent layer; and / or a second hole transport layer, the second hole transport layer being located between the hole generation layer and the third luminescent layer.

8. A display panel, characterized by, Comprising: the luminescent device as claimed in any one of claims 2-7.

9. A display device, characterized by comprising: Comprising: the display panel as claimed in claim 8.

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