Thin film light-emitting device, preparation method thereof and display panel

Abstract

The invention provides a thin film light-emitting device, a preparation method thereof and a display panel, and belongs to the technical field of display. The thin film light-emitting device comprises an anode, a hole transport layer, a light-emitting layer and a cathode which are sequentially stacked, the hole transport layer contains a hole transport material and a triplet state quenching material, and the triplet state quenching material can quench at least part of triplet state excitons in the hole transport material. The thin film light-emitting device can improve the stability of the hole transport layer.

Description

Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a thin film light emitting device and a preparation method thereof, and a display panel. Background Art

[0002] Quantum-dot light-emitting diodes are a type of light-emitting display technology that is very close to commercialization in recent years. The hole transport layer of quantum dot light-emitting diodes generally uses organic semiconductor materials, but the organic semiconductor materials are easily damaged, which leads to the performance degradation of quantum dot light-emitting diodes.

[0003] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0004] The purpose of the present disclosure is to overcome the deficiencies of the above-mentioned prior art, provide a thin film light emitting device and a preparation method thereof, and a display panel, and improve the stability of the hole transport layer.

[0005] According to one aspect of the present disclosure, there is provided a thin film light emitting device, comprising an anode, a hole transport layer, a light emitting layer and a cathode which are stacked in sequence;

[0006] The hole transport layer contains a hole transport material and a triplet quenching material, and the triplet quenching material can quench at least part of triplet excitons in the hole transport material.

[0007] According to an embodiment of the present disclosure, the HOMO energy level of the triplet quenching material is not greater than the HOMO energy level of the hole transport material.

[0008] According to one embodiment of the present disclosure, the difference between the LUMO energy level of the triplet quenching material and the LUMO energy level of the hole transport material is not less than -1 eV.

[0009] According to one embodiment of the present disclosure, the LUMO energy level of the triplet quenching material is greater than the LUMO energy level of the hole transport material.

[0010] According to an embodiment of the present disclosure, the mobility of the triplet quenching material is smaller than the mobility of the hole transport material.

[0011] According to one embodiment of the present disclosure, the triplet energy level of the triplet quenching material is smaller than the triplet energy level of the hole transport material.

[0012] According to one embodiment of the present disclosure, the singlet energy level of the triplet quenching material is greater than the singlet energy level of the hole transport material.

[0013] According to an embodiment of the present disclosure, the mass ratio of the triplet quenching material in the hole transport layer is between 0.0001% and 90%.

[0014] According to an embodiment of the present disclosure, the mass ratio of the triplet quenching material in the hole transport layer is between 1% and 30%.

[0015] According to one embodiment of the present disclosure, the triplet quenching material includes one or more of transition metal derivatives, acene, acene derivatives, cyclooctadiene, cyclooctadiene derivatives, cyclooctatetraene, cyclooctatetraene derivatives, organic small molecule semiconductor materials, and polymer semiconductor materials.

[0016] According to one embodiment of the present disclosure, the triplet quenching material includes a transition metal chelate.

[0017] According to one embodiment of the present disclosure, the triplet quenching material includes one or more of nickel chelate and zinc chelate.

[0018] According to one embodiment of the present disclosure, the triplet quenching material is selected from the following compounds:

[0019]

[0020] According to one embodiment of the present disclosure, the hole transport material and the triplet quenching material are cross-linked to form a polymer.

[0021] According to one embodiment of the present disclosure, the triplet quenching material is connected to at least a portion of the hole transport material via a chemical bond or a connecting group.

[0022] According to an embodiment of the present disclosure, the hole transport material is an organic semiconductor material; and the light-emitting layer is a quantum dot light-emitting layer.

[0023] According to an embodiment of the present disclosure, the thin film light emitting device is a blue light thin film light emitting device.

[0024] According to another aspect of the present disclosure, a method for preparing a thin film light-emitting device is provided, which is used to prepare the above-mentioned thin film light-emitting device; the preparation method comprises preparing an anode, a hole transport layer, a light-emitting layer and a cathode;

[0025] The preparation of the hole transport layer comprises:

[0026] Dissolving the hole transport material and the triplet quenching material in a solvent to obtain a precursor solution;

[0027] The hole transport layer is prepared using the precursor liquid by a coating process, a screen printing process or an inkjet printing process.

[0028] According to another aspect of the present disclosure, a method for preparing a thin film light-emitting device is provided, which is used to prepare the above-mentioned thin film light-emitting device; the preparation method comprises preparing an anode, a hole transport layer, a light-emitting layer and a cathode;

[0029] The preparation of the hole transport layer comprises:

[0030] polymerizing the monomer of the hole transport material and the monomer of the triplet quenching material to form a multifunctional polymer;

[0031] dissolving the multifunctional polymer in a solvent to obtain a precursor solution;

[0032] The hole transport layer is prepared using the precursor liquid by a coating process, a screen printing process or an inkjet printing process.

[0033] According to another aspect of the present disclosure, a method for preparing a thin film light-emitting device is provided, which is used to prepare the above-mentioned thin film light-emitting device; the preparation method comprises preparing an anode, a hole transport layer, a light-emitting layer and a cathode;

[0034] The preparation of the hole transport layer comprises:

[0035] The hole transport material and the triplet quenching material are co-evaporated to form the hole transport layer.

[0036] According to another aspect of the present disclosure, a method for preparing a thin film light-emitting device is provided, which is used to prepare the above-mentioned thin film light-emitting device; the preparation method comprises preparing an anode, a hole transport layer, a light-emitting layer and a cathode;

[0037] The preparation of the hole transport layer comprises:

[0038] Synthesizing a multifunctional material, wherein the multifunctional material is a material formed by connecting the hole transport material and the triplet quenching material via a chemical bond or a connecting group;

[0039] uniformly mixing the multifunctional material and the hole transport material to form an evaporation material;

[0040] The hole transport layer is formed by using the evaporation material and adopting an evaporation process. According to another aspect of the present disclosure, a display panel is provided, comprising the above-mentioned thin film light emitting device.

[0041] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0043] Figure 1 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0044] Figure 2 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0045] Figure 3 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0046] Figure 4 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0047] Figure 5 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0048] Figure 6 is a luminescence intensity curve of each thin film in the first verification example.

[0049] Figure 7 2 is the luminescence intensity curve of each thin film in the second verification example. DETAILED DESCRIPTION

[0050] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present disclosure will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their detailed description will be omitted. In addition, the drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale.

[0051] The present disclosure provides a thin film light emitting device and a display panel using the thin film light emitting device. Figure 1 The thin film light emitting device comprises a stacked anode AE ​​and a cathode CE, and a light emitting functional layer EFU sandwiched between the anode AE ​​and the cathode CE. Figure 1The light-emitting functional layer EFU at least includes a hole transport layer HTL and a light-emitting layer, and the hole transport layer HTL is located on the side of the light-emitting layer close to the anode AE. The anode and the cathode respectively provide electrons, holes and other carriers to the light-emitting functional layer EFU, so that the light-emitting layer of the light-emitting functional layer EFU emits light. It can be understood that the type of thin-film light-emitting device is different, and the material and film layer of the light-emitting functional layer EFU are different.

[0052] For example, see Figure 2 When the thin film light emitting device is an OLED (organic electroluminescent diode), the light emitting functional layer EFU may include an organic light emitting layer EML as a light emitting layer, and may include one or more of a hole injection layer, a hole transport layer HTL, an electron blocking layer EBL, a hole blocking layer HBL, an electron transport layer ETL and an electron injection layer EIL, and at least includes the hole transport layer HTL. Further, the organic light emitting layer EML may include a light emitting layer host material and a light emitting layer guest material, and the light emitting layer guest material may be a fluorescent dopant or a phosphorescent dopant, and in particular may be a thermally activated delayed fluorescent material. See Figure 4 When the OLED adopts a stacked structure, a charge generation layer CGL may also be provided in the light emitting functional layer EFU.

[0053] For another example, see Figure 3 When the thin film light emitting device is a QLED (quantum dot light emitting diode), the light emitting functional layer EFU may include a quantum dot light emitting layer QDL as a light emitting layer, and may include one or more of a hole injection layer, an electron transport layer ETL, an electron blocking layer EBL, a hole blocking layer HBL, an electron transport layer ETL and an electron injection layer EIL, and at least includes a hole transport layer HTL. The quantum dot light emitting layer may have quantum dots. Furthermore, the quantum dots may be connected to each other through surface modification groups. See Figure 5 When the QLED adopts a stacked structure, a charge generation layer CGL may also be provided in the light-emitting functional layer EFU.

[0054] In the embodiments of the present disclosure, see Figure 2 to Figure 5 The light-emitting functional layer EFU may include a layer of light-emitting stacked structure ELS, or may include a plurality of stacked light-emitting stacked structures ELS. When the light-emitting functional layer EFU includes a plurality of light-emitting stacked structures ELS, a charge generation layer CGL may be provided between two adjacent light-emitting stacked structures ELS. Each light-emitting stacked structure ELS is provided with one or more light-emitting layers, and the light-emitting layer may be any one of an organic light-emitting layer or a quantum dot light-emitting layer.

[0055] exist Figure 2 and Figure 3 In the example of FIG. 1 , the light-emitting functional layer EFU has a light-emitting stacked structure ELS. Figure 2 and Figure 3 , the thin film light emitting device comprises an anode AE, a light emitting stack structure ELS, and a cathode CE which are stacked in sequence; wherein the light emitting stack structure ELS comprises a hole regulating unit, a light emitting layer (such as an organic light emitting layer EML or a quantum dot light emitting layer QDL), and an electron regulating unit which are stacked in sequence. The hole regulating unit is located on the side of the light emitting layer close to the anode, and the electron regulating unit is located on the side of the light emitting layer close to the cathode. The anode is used to inject holes into the light emitting layer through the hole regulating unit, and the cathode is used to inject electrons into the light emitting layer through the electron regulating unit. The hole regulating unit and the electron regulating unit are respectively used to adjust the injection efficiency and injection speed of the holes and electrons injected into the light emitting layer, and to adjust the energy levels of the injected electrons and holes, so as to improve the balance of hole injection and electron injection, thereby improving the performance of the light emitting functional layer EFU, such as improving the luminous efficiency of the thin film light emitting device, improving the device life of the thin film light emitting device, reducing the power supply voltage of the thin film light emitting device, etc. One or more of the above.

[0056] The hole regulating unit may include one or more layers of the hole injection layer, the hole transport layer HTL, the electron blocking layer EBL and other film layers, and at least includes the hole transport layer HTL. Among them, the hole injection layer, the hole transport layer HTL, the electron blocking layer EBL and the like are stacked in sequence from the anode to the light-emitting layer. It is understood that in some examples, one or more of the hole injection layer, the hole transport layer HTL, the electron blocking layer EBL and other film layers can be set as a multi-layer stacked structure, for example, the hole transport layer HTL can include a first hole transport layer and a second hole transport layer stacked, etc.

[0057] The electron regulating part may include one or more of the electron injection layer EIL, the electron transport layer ETL, the hole blocking layer HBL and other film layers, wherein the electron injection layer EIL, the electron transport layer ETL, the hole blocking layer HBL and the like are stacked in sequence along the direction from the cathode to the light-emitting layer. It is understood that in some examples, one or more of the electron injection layer EIL, the electron transport layer ETL, the hole blocking layer HBL and other film layers may be arranged as a multi-layer stacked structure, for example, the electron transport layer ETL may include a first electron transport layer and a second electron transport layer arranged in a stacked manner, etc.

[0058] exist Figure 4 and Figure 5 In the example, the light-emitting functional layer EFU has a multi-layered light-emitting stack structure ELS ( Figure 4 and Figure 5 A two-layer light emitting stack structure ELS is exemplified in FIG. Figure 4 and Figure 5The thin film light emitting device comprises an anode, a light emitting stack structure ELS and a cathode which are stacked in sequence. Among them, any layer of the light emitting stack structure ELS comprises a hole regulating part, a light emitting layer (such as an organic light emitting layer or a quantum dot light emitting layer) and an electron regulating part which are stacked in sequence, the hole regulating part is located on the side of the light emitting layer close to the anode, and the electron regulating part is located on the side of the light emitting layer close to the cathode.

[0059] Optionally, the light-emitting functional layer EFU may further include a charge generation layer CGL located between two adjacent light-emitting stack structures ELS to improve the efficiency of injecting electrons and holes into the two adjacent light-emitting stack structures ELS. For example, the charge generation layer CGL includes an N-type charge generation layer NCGL and a P-type charge generation layer PCGL stacked between two adjacent light-emitting stack structures ELS. Among them, the N-type charge generation layer NCGL is arranged adjacent to the electron adjustment part of one of the light-emitting stack structures ELS, and is used to inject electrons into the electron adjustment part of the light-emitting stack structure ELS; the P-type charge generation layer PCGL is arranged adjacent to the hole adjustment part of the other light-emitting stack structure ELS, and is used to inject holes into the hole adjustment part of the light-emitting stack structure ELS. In other words, the P-type charge generation layer PCGL is arranged on the side of the N-type charge generation layer NCGL away from the anode. Of course, it can be understood that in other examples, the charge generation layer CGL may also include other structures.

[0060] It is understood that in some other embodiments of the present disclosure, the electron regulation portion of the light emitting stacked structure ELS may be omitted, or may have other structures besides the electron injection layer EIL, the electron transport layer ETL and the hole blocking layer HBL.

[0061] It can be understood that when multiple light-emitting layers are provided in the light-emitting stack structure ELS, the colors of the multiple light-emitting layers may be the same or different, and the types of the multiple light-emitting layers may be the same or different.

[0062] It is understandable that, for any light-emitting stacked structure ELS, it may be provided with a light-emitting layer (such as a quantum dot light-emitting layer or an organic light-emitting layer), and may be provided with one or more of a hole injection layer, a hole transport layer HTL, an electron blocking layer EBL, a hole blocking layer HBL, an electron transport layer ETL, and an electron injection layer EIL, or other film layers may be added as needed. Of course, in the light-emitting stacked structure ELS, one or more of the hole injection layer, the electron blocking layer EBL, the hole blocking layer HBL, the electron transport layer ETL, and the electron injection layer EIL may also be omitted. For two light-emitting stacked structures ELS of the same thin-film light-emitting device, the film layer structures of the two light-emitting stacked structures ELS may be the same or different.

[0063] In the embodiment of the present disclosure, the thin film light emitting device includes an anode, a hole transport layer, a light emitting layer and a cathode which are stacked in sequence. The hole transport material of the hole transport layer is an organic semiconductor material, such as an organic small molecule semiconductor material or a polymer semiconductor material. When electrons leak into the hole transport layer, excitons are formed, and the excitons include triplet excitons and singlet excitons.

[0064] Singlet excitons usually have a short lifetime (e.g. -10 ns), and can spontaneously decay relatively quickly. However, due to the limitation of the selection rule of conservation of angular momentum, the lifetime of triplet excitons is relatively long, which can reach the order of us or even ms. Moreover, from a statistical point of view, the probability of formation of triplet excitons is 75%, which is also greater than the 25% probability of formation of singlet excitons. These factors cause the concentration of triplet excitons in the hole transport layer to be much greater than the concentration of singlet excitons. Triplet excitons can affect the stability of the hole transport layer in many ways. When the energy level is appropriate, triplet excitons can react with trace oxygen in the film to form singlet oxygen, which can attack the unsaturated CC bonds of the hole transport layer. Triplet excitons can undergo quenching reactions with carriers in the hole transport layer to produce high-energy carriers or excited states, thereby having enough energy to attack various chemical bonds in the hole transport layer. Triplet excitons may also react with other triplet excitons or singlet excitons to generate the same high-energy state to destroy the hole transport layer.

[0065] In the embodiment of the present disclosure, the hole transport layer HTL may include a triplet quenching material in addition to the hole transport material. The triplet quenching material may quench at least part of the triplet excitons in the hole transport material. Specifically, the triplet quenching material may capture the triplet excitons in the hole transport layer HTL and convert them into a non-destructive final state, thereby reducing the damage of the triplet excitons to the hole transport material, reducing the aging speed of the hole transport layer HTL, and increasing the life of the thin film light-emitting device.

[0066] Optionally, the triplet quenching material captures triplet excitons via a Dexter charge transfer mechanism or a collision energy exchange mechanism. Further, the triplet quenching material can capture triplet excitons within a surrounding range of 1 nm.

[0067] In one embodiment of the present disclosure, the thin film light emitting device is a blue thin film light emitting device. Compared with the red thin film light emitting device and the green thin film light emitting device, the hole transport layer of the blue thin film light emitting device is more easily damaged; therefore, a triplet quenching material is introduced into the hole transport layer of the blue thin film light emitting device to increase the life of the blue thin film light emitting device, which can more effectively improve the restriction of the blue thin film light emitting device on the life of the display panel or the light emitting panel.

[0068] In one embodiment of the present disclosure, the thin film light emitting device is a QLED, that is, the light emitting layer is a quantum dot light emitting layer. In this embodiment, the hole electron transport layer can be made of inorganic semiconductor materials, such as zinc oxide or magnesium oxide; the hole transport material is an organic semiconductor material. This makes the hole transport layer the most easily damaged film layer in the QLED, which restricts the life of the device. In the embodiment of the present disclosure, the life of the QLED can be improved by adding a triplet quenching material to the hole transport layer to improve the stability of the hole transport layer.

[0069] In one embodiment of the present disclosure, the HOMO (highest occupied molecular orbital) energy level of the triplet quenching material is not greater than the HOMO energy level of the hole transport material. In this way, compared with the hole transport material, the triplet quenching material has a deeper HOMO energy level, which can avoid the generation of hole traps in the hole transport layer and ensure the smooth transmission of holes in the hole transport layer. For example, taking the hole transport material as TFB (poly [9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) as an example, its HOMO energy level is -5.4eV, then the HOMO energy level of the triplet quenching material may not be greater than -5.4eV. Of course, in other embodiments of the present disclosure, it may also be slightly higher than -5.4eV, so as not to introduce significant hole traps.

[0070] In one embodiment of the present disclosure, the difference between the LUMO (lowest unoccupied molecular orbital) energy level of the triplet quenching material and the LUMO energy level of the hole transport material is not less than -1eV. In this way, it is possible to avoid the LUMO energy level of the triplet quenching material being too low to produce a significant electron leakage channel. For example, if the hole transport material is TFB, and its LUMO energy level is -2.8eV, then the LUMO energy level of the triplet quenching material can be not less than -3.8eV.

[0071] Furthermore, the LUMO energy level of the triplet quenching material is greater than the LUMO energy level of the hole transport material, so that the possibility of forming an electron leakage channel can be further reduced.

[0072] In one embodiment of the present disclosure, the mobility of the triplet quenching material is less than the mobility of the hole transporting material. In this way, the influence of the triplet quenching material on the hole transporting performance of the hole transporting layer can be reduced. When the situation permits, the hole mobility of the triplet quenching material can be reduced as much as possible, for example, the hole mobility of the triplet quenching material is less than 1e - 5 cm / V / S.

[0073] In one embodiment of the present disclosure, the triplet energy level of the triplet quenching material is lower than the triplet energy level of the hole transport material. In this way, triplet excitons on the hole transport material can be transferred to the triplet quenching material, thereby quenching the triplet excitons on the hole transport material without overcoming the energy level barrier.

[0074] In one embodiment of the present disclosure, the speed at which the triplet quenching material transitions from the triplet state to the ground state is greater than the speed at which the hole transport material transitions from the triplet state to the ground state.

[0075] In one embodiment of the present disclosure, the singlet energy level of the triplet quenching material is greater than the singlet energy level of the hole transport material. In this way, the triplet quenching material will not affect the transmission and blocking properties of the singlet excitons of the hole transport material, and can better maintain the singlet characteristics in the main body.

[0076] In one embodiment of the present disclosure, the mass ratio of the triplet quenching material in the hole transport layer is between 0.0001% and 90%. Furthermore, the mass ratio of the triplet quenching material in the hole transport layer is between 1% and 30%, for example, 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%. In this way, the hole transport performance of the hole transport layer can be maintained as much as possible while reducing the risk of damage to the hole transport material due to triplet excitons.

[0077] In one embodiment of the present disclosure, in the hole transport layer, the hole transport material and the triplet quenching material are two independent materials, that is, there is no strong chemical bond such as a covalent bond between the two. The triplet quenching material is uniformly dispersed in the hole transport layer. In one example, a solution containing a hole transport material and a triplet quenching material can be used as a raw material to form a hole transport layer by a solution process such as coating, spin coating, printing or inkjet printing. In another example, the hole transport material and the triplet quenching material can be co-evaporated to form a hole transport layer, and the evaporation speed of the hole transport material and the triplet quenching material determines the content of the triplet quenching material in the hole transport layer.

[0078] In one example, the hole transport layer can be prepared by the following method:

[0079] Dissolving the hole transport material and the triplet quenching material in a solvent to obtain a precursor solution;

[0080] The hole transport layer is prepared using the precursor solution by using a coating process (e.g., a spin coating process), a screen printing process, or an inkjet printing process. In this example, the hole transport material, the triplet quenching material, and the solvent need to be selected so that the hole transport material and the triplet quenching material can be evenly and non-aggregatedly distributed in the solution, thereby facilitating the formation of a film layer with uniform thickness.

[0081] In another example, the hole transport layer can be prepared by the following method:

[0082] The hole transport material and the triplet quenching material are co-evaporated to form the hole transport layer.

[0083] For example, the hole transport material and the triplet quenching material can be placed in evaporation pool 1 and evaporation pool 2, respectively. The evaporation rate of the hole transport material is controlled at 0.1 angstroms to 10 nanometers per minute, and the evaporation rate of the triplet quenching material is controlled at 0.1 angstroms to 10 nanometers per minute. In this way, the evaporation rate ratio of the hole transport material and the triplet quenching material can be controlled between 1:1 and 1000:1 according to different doping designs. In this example, the melting point of the triplet quenching material can be made less than 800°C to ensure that the triplet quenching material can be effectively evaporated.

[0084] In another embodiment of the present disclosure, the hole transport material and the triplet quenching material are cross-linked to form a multifunctional polymer, so that the multifunctional polymer has both a segment for hole transport and a segment for quenching triplet excitons. For example, the chemical formula of the multifunctional polymer is [A] x [B] y , A represents a monomer of a hole transport conductive polymer, B represents a triplet quenching material or a monomer thereof. x represents the number of repeating units of A, and y represents the number of repeating units of a triplet quenching material or a monomer thereof. The polymer may be a random dimer polymer, a diblock polymer, or an alternating polymer.

[0085] In this way, the multifunctional polymer can be directly used as a hole transport layer, and its hole transport material and triplet quenching material are integrated into the multifunctional polymer, which can ensure the material ratio of the triplet quenching material and the uniformity of its distribution in the hole transport layer.

[0086] Optionally, A can be TFB monomer, PVK (English name: Poly (N-vinyl carbazole), Chinese name: poly (N-vinyl carbazole)) monomer, TPD (English name: (N,N'-bis (3-methylphenyl) -N,N'-diphenyl-benzidine); Chinese name: N,N'-diphenyl-N,N'-di (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine)) or other monomers.

[0087] It can be understood that in the multifunctional polymer, B can be directly a monomer of a triplet quencher material, or it can be a modified triplet quencher material, and the modified triplet quencher material is a triplet quencher material monomer in which a condensation functional group (such as a double bond, isocyanate, etc.) is introduced so that the modified triplet quencher material can polymerize with A.

[0088] In one example, a triplet quenching material can be linked to a polymer that is a hole transport material through chemical synthesis to form a new polymer.

[0089] In another example, the monomers of the triplet quenching material and the monomers of the hole transporting material may be polymerized together to generate a desired polymer.

[0090] In one example, the hole transport layer can be prepared by the following method:

[0091] polymerizing the monomer of the hole transport material and the monomer of the triplet quenching material to form a multifunctional polymer;

[0092] dissolving the multifunctional polymer in a solvent to obtain a precursor solution;

[0093] The hole transport layer is prepared using the precursor liquid by a coating process, a screen printing process or an inkjet printing process.

[0094] In some other embodiments, the triplet quenching material is connected to at least part of the hole transport material by a chemical bond or a linking group. In this embodiment, a multifunctional material can be synthesized first, and the multifunctional material is a material formed by connecting the hole transport material and the triplet quenching material by a chemical bond or a linking group; for example, the structure of the multifunctional material is a structure formed by directly connecting the hole transport material and the triplet quenching material by a chemical bond (such as a single bond), or a structure formed by connecting the hole transport material and the triplet quenching material by a linking group (such as a methylene group, a phenylene group, etc.). It can be understood that it is not necessarily required to use the hole transport material and the triplet quenching material as raw materials to synthesize the required multifunctional material, and the structure of the synthesized material is based on the interconnection of the multifunctional material as the hole transport material and the triplet quenching material. The multifunctional material has both hole transport function and triplet quenching function. When preparing the hole transport layer, the hole transport material and the multifunctional material can be used as raw materials. For example, a mixture of the hole transport material and the multifunctional material (evaporation material) is used for co-evaporation to form the hole transport layer.

[0095] For example, the hole transport material is A, the triplet quenching material is B, and the multifunctional material is AB. When the hole transport layer is prepared by evaporation, the evaporation source material is A with a mass content of x, and AB with a mass content of 1-a. x is a positive number less than 1. By adjusting a, the mass content of the triplet quenching material in the hole transport layer can be adjusted.

[0096] It can be understood that one multifunctional material can be connected to one triplet quenching material or multiple triplet quenching materials.

[0097] In one example, the hole transport layer can be prepared by the following method:

[0098] Synthesizing a multifunctional material, wherein the multifunctional material is a material formed by connecting the hole transport material and the triplet quenching material via a chemical bond or a connecting group;

[0099] uniformly mixing the multifunctional material and the hole transport material to form an evaporation material;

[0100] The hole transport layer is formed by using the evaporation material and an evaporation process.

[0101] Optionally, the triplet quenching material includes one or more of transition metal derivatives, acene, acene derivatives, cyclooctadiene, cyclooctadiene derivatives, cyclooctatetraene, cyclooctatetraene derivatives, organic small molecule semiconductor materials, and polymer semiconductor materials.

[0102] In one embodiment of the present disclosure, the transition metal derivative may be a transition metal chelate, for example, a nickel derivative, in particular, a nickel chelate, or of course, a chelate of other transition metals, for example, a zinc chelate.

[0103] For example, the triplet quenching material is selected from the following compounds:

[0104]

[0105] Nickel chelates have multiple triplet quenching mechanisms, which can quench at least 1.1eV triplet excitons without affecting singlet excitons in hole transport materials. The quenching rate can reach 10 8 Moreover, nickel chelates can sometimes quench free radicals and decompose peroxides, further improving the protection of hole transport materials.

[0106] Acene and acene derivatives usually have a relatively large energy level difference between singlet and triplet states, so they can quench the triplet state in the hole transport material while better maintaining the singlet state in the hole transport material. For example, the singlet energy level of anthracene is 3.1eV, and the triplet energy level is 1.78eV.

[0107] Cyclooctatetraene (COT) is a non-classical triplet quencher. In addition to having a higher triplet excited state (energy level of 2.56eV), it has a very low triplet energy level (energy level of 0.8eV) under relaxation conditions, which can effectively quench the triplet state in the host material. At the same time, its singlet energy level is relatively high (reaching 4.39eV), which can not affect the singlet state in the hole transport material and the charge transport in the hole transport material. The triplet lifetime of cyclooctatetraene is relatively short compared to anthracene, and it can decay the triplet state accepted from the hole transport material relatively quickly.

[0108] BSBCZ has a lower triplet energy level (1.48eV) and a higher singlet energy level (2.97eV). BSBCZ is a representative of a more traditional and widely used small molecule or polymer semiconductor material that can be used as a triplet quencher. The energy level of this type of triplet quencher needs to meet certain matching conditions with the energy level of the hole transport material, for example, the triplet energy level of the triplet quencher must be lower than the triplet energy level of the hole transport material. Ideally, the singlet energy level of the triplet quencher should be higher than the singlet energy level of the hole transport material, the HOMO energy level of the triplet quencher should be lower than the HOMO energy level of the hole transport material, and the LUMO energy level of the triplet quencher should be higher than the HOMO energy level of the hole transport material.

[0109] The disclosed embodiments also provide a verification example to verify the protective effect of adding a triplet quenching material to the hole transport material on the hole transport material.

[0110] First verification example:

[0111] The hole transport material is the polymer TFB (Poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine), Chinese name: Poly[9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine]), and the triplet quenching material is UV-1084 (chemical full name: 2,2′-Thiobis(4-tert-octylphenolato)-n-butylamine nickel(II), Chinese name: 2,2-Thiobis(4-tert-octylphenol)-n-butylamine nickel salt).

[0112] Among them, the structure of UV-1084 is shown as:

[0113]

[0114] The hole transport material and the triplet quenching material were co-dissolved in chlorobenzene to obtain a hole transport layer precursor. The ITO patterned glass substrate was treated with UV and ozone. Then PEDOT:PSS was spin-coated at a speed of 3000 rpm for 1 minute; then, it was annealed at 150°C in air for 30 minutes to form a hole injection layer. The device was transferred to an inert ring and spin-coated with the above-mentioned hole transport layer precursor. The concentration of the material (hole transport material + triplet quenching material) in the precursor was 12 mg / mL, the spin-coating rate was 2000 rpm, the spin-coating time was 1 minute, and annealed at 120°C for 10 minutes to obtain a hole transport layer film for testing.

[0115] In this verification example, a first verification film, a second verification film and a first reference film were prepared. In the first verification film, the mass proportion of triplet quenching material was 5%; in the second verification film, the mass proportion of triplet quenching material was 10%; and the first reference film did not contain triplet quenching material.

[0116] The first verification film, the second verification film and the reference film are irradiated with detection light (low intensity), aging light (high intensity) and detection light (low intensity) in turn, and the wavelength of the irradiation light is 405 nanometers. At the same time, the intensity of the light emitted by the hole transport material after being excited is detected, and the light intensity can reflect the degree of damage to the hole transport material. The stronger the light intensity, the less damage to the hole transport material, and the better the protection effect of the triplet quenching material on the hole transport material. Among them, the hole transport material generates photogenerated excitons after being exposed to light, and the triplet quenching material can protect the hole transport material by quenching the triplet excitons. The verification test results are shown in Figure 6 middle.

[0117] See also Figure 6 , when the film is irradiated with a detection light of lower intensity, all three films are excited and emit light under the light. However, it is obvious that the luminescence intensity of the first reference film C10 without the addition of triplet quenching material decreases relatively quickly, while the luminescence intensity of the first verification film C11 and the second verification film C12 is maintained relatively well. This shows that the triplet quenching material has a good protective effect on the hole transport material. When the film is irradiated with a higher intensity of aging light, the luminescence intensity of the three films is, from large to small, the second verification film C12, the first verification film C11 and the first reference film C10. This shows that the stability of the film added with the triplet quenching material under strong light is greatly improved, and the stability of the film is correlated with the amount of triplet quenching material added. Within a certain content range, the more triplet quenching material is added, the better the stability of the hole transport material.

[0118] Second verification example

[0119] Referring to the first verification example, the second reference film, the third verification film, the fourth verification film, the fifth verification film, and the sixth verification film were prepared. Among them, the second reference film does not contain a triplet quenching material, and the hole transport material is TFB. The triplet quenching material in the third verification film, the fourth verification film, the fifth verification film, and the sixth verification film is 1,3,5,7-cyclooctatetraene-1,2-dicarboxylic acid methyl ester, and the mass content is 2%, 5%, 10%, and 20%, respectively. The thickness of each film is about 20nm.

[0120] Among them, the structural formula of 1,3,5,7-cyclooctatetraene-1,2-dicarboxylic acid methyl ester is:

[0121]

[0122] Each film is irradiated with detection light (low intensity), aging light (high intensity), and detection light (low intensity) in turn, and the wavelength of the irradiation light is 405 nanometers. At the same time, the intensity of the light emitted by the hole transport material after being excited is detected, and the light intensity can reflect the degree of damage to the hole transport material. The stronger the light intensity, the less damage to the hole transport material, and the better the protection effect of the triplet quenching material on the hole transport material. Among them, the hole transport material generates photogenerated excitons after being exposed to light, and the triplet quenching material can protect the hole transport material by quenching the triplet excitons. The verification test results are shown in Figure 7 middle.

[0123] See also Figure 7 When triplet quenching materials are added to the film, the stability of the film under strong light is greatly improved. This shows that triplet quenching materials can protect hole transport materials.

[0124] As follows, the structure, materials and preparation method of the thin-film light-emitting device in the embodiment of the present disclosure are exemplified by taking multiple embodiments as examples.

[0125] Example 1

[0126] The thin film light emitting device includes an anode, a hole injection layer, a hole transport layer, a quantum dot light emitting layer, an electron transport layer and a cathode which are stacked in sequence. In this example, the material of the anode is ITO; the material of the hole transport layer is PEDOT:PSS; the material of the hole transport layer is a mixture of TFB and UV-1084; the material of the electron transport layer is zinc oxide; and the material of the cathode is aluminum.

[0127] The thin film light emitting device can be prepared by the following method.

[0128] 1) TFB and UV-1084 were dissolved in chlorobenzene to obtain a hole transport layer precursor solution; in the precursor solution, the total mass concentration of TFB and UV-1084 was 12 mg / mL; in the film-forming material (UV-1084+TFB), the mass proportion of UV-1084 was 1%.

[0129] 2) Performing UV treatment and ozone treatment on the patterned ITO substrate (ITO layer + glass layer).

[0130] 3) Spin coating PEDOT:PSS at a rotation speed of 3000 rpm for 1 minute, and then annealing at 150° C. in air for 30 minutes to form a hole injection layer.

[0131] 4) The device was transferred to an inert environment, and a hole transport layer precursor solution was spin-coated at a rotation speed of 2000 rpm for 1 minute; then, annealed at 120° C. for 10 minutes to form a hole transport layer.

[0132] 5) Spin coating a quantum dot liquid, wherein the quantum dot content in the quantum dot liquid is 20 mg / mL, the rotation speed is 2000 rpm, and the rotation time is 1 minute; and then annealing at 100° C. for 10 minutes to form a quantum dot light-emitting layer.

[0133] 6) Spin coating a zinc oxide precursor solution at a rotation speed of 2000 rpm for 1 minute; and then annealing at 100° C. for 10 minutes to obtain an electron transport layer.

[0134] 7) Evaporated cathode, made of aluminum with a thickness of 100 nm.

[0135] Example 2

[0136] The thin film light emitting device includes an anode, a hole injection layer, a hole transport layer, a quantum dot light emitting layer, an electron transport layer and a cathode which are stacked in sequence. In this example, the material of the anode is ITO; the material of the hole transport layer is PEDOT:PSS; the material of the electron transport layer is zinc oxide; and the material of the cathode is aluminum. The material of the hole transport layer is the following multifunctional polymer:

[0137]

[0138] Wherein, x represents the number of repeating units of the TFB monomer, which is 200; and y represents the number of repeating units of the cyclooctatetraene derivative monomer, which is 2.

[0139] In this example, the hole transport material and the triplet quenching material are cross-linked to form a multifunctional polymer, such that the multifunctional polymer has a hole transporting segment and a triplet quenching segment.

[0140] In this embodiment, the thin film light emitting device can be prepared by referring to the preparation method of embodiment 1, except that the multifunctional polymer of this embodiment is used as the film-forming material when preparing the hole transfer layer precursor solution. In the hole transfer layer precursor solution, the mass concentration of the film-forming material is 12 mg / mL.

[0141] Example 3

[0142] The thin film light emitting device includes an anode, a hole transport layer, a quantum dot light emitting layer, an electron transport layer and a cathode which are stacked in sequence. In this example, the material of the anode is molybdenum oxide / silver; the material of the hole transport layer is CBP doped with anthracene; the material of the electron transport layer is zinc oxide; and the material of the cathode is ITO.

[0143] The structure of CBP is as follows:

[0144]

[0145] The thin film light emitting device can be prepared by the following method.

[0146] 1) Perform UV treatment and ozone treatment on a patterned ITO substrate (ITO layer + glass layer).

[0147] 2) Spin coating a zinc oxide precursor solution at a rotation speed of 2000 rpm for 1 minute; and then annealing at 100° C. for 10 minutes to obtain an electron transport layer.

[0148] 3) Spin coating a quantum dot liquid, wherein the quantum dot content in the quantum dot liquid is 20 mg / mL, the rotation speed is 2000 rpm, and the rotation time is 1 minute; and then annealing at 100° C. for 10 minutes to form a quantum dot light-emitting layer.

[0149] 4) A stable hole transport layer was formed by a co-evaporation process. Source 1 used CBP (evaporation rate was 1 nm / min) and source 2 used anthracene (evaporation rate was 0.1 nm / min), and the co-evaporation was 50 nm.

[0150] 5) Evaporated cathode, the material is molybdenum oxide / silver, the thickness is 3nm / 100nm.

[0151] Example 4

[0152] The thin film light emitting device includes an anode, a hole transport layer, a quantum dot light emitting layer, an electron transport layer and a cathode which are stacked in sequence. In this example, the material of the anode is molybdenum oxide / silver; the material of the hole transport layer is a mixture of CPB and CPB modified by COT; the material of the electron transport layer is zinc oxide; and the material of the cathode is ITO.

[0153] The structure of COT-modified CPB (multifunctional material) is as follows:

[0154]

[0155] The thin film light emitting device can be prepared by the following method.

[0156] 1) Perform UV treatment and ozone treatment on a patterned ITO substrate (ITO layer + glass layer).

[0157] 2) Spin coating a zinc oxide precursor solution at a rotation speed of 2000 rpm for 1 minute; and then annealing at 100° C. for 10 minutes to obtain an electron transport layer.

[0158] 3) Spin coating a quantum dot liquid, wherein the quantum dot content in the quantum dot liquid is 20 mg / mL, the rotation speed is 2000 rpm, and the rotation time is 1 minute; and then annealing at 100° C. for 10 minutes to form a quantum dot light-emitting layer.

[0159] 4) A stable hole transport layer was formed by an evaporation process. The source material was a mixture of CBP and COT-modified CPB (1:1). The evaporation rate was 1 nm / min, and a total of 50 nm was evaporated.

[0160] 5) Evaporated cathode, the material is molybdenum oxide / silver, the thickness is 3nm / 100nm.

[0161] The embodiment of the present disclosure also provides a display panel, which includes any one of the thin film light emitting devices described in the above thin film light emitting device embodiment. The display panel can be a smart phone screen, a smart watch screen, or other types of display screens. Since the display panel includes any one of the thin film light emitting devices described in the above thin film light emitting device embodiment, it has the same beneficial effects, and the present disclosure will not be repeated here.

[0162] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A thin film light emitting device comprising an anode, a hole transport layer, a light emitting layer and a cathode stacked in sequence; The hole transport layer contains a hole transport material and a triplet quenching material, and the triplet quenching material can quench at least part of triplet excitons in the hole transport material.

2. The thin film light emitting device according to claim 1, wherein: The HOMO energy level of the triplet quenching material is not greater than the HOMO energy level of the hole transport material.

3. The thin film light emitting device according to claim 1, wherein: The difference between the LUMO energy level of the triplet quenching material and the LUMO energy level of the hole transport material is not less than -1 eV.

4. The thin film light emitting device according to claim 3, wherein: The LUMO energy level of the triplet quenching material is greater than the LUMO energy level of the hole transporting material.

5. The thin film light emitting device according to claim 1, wherein: The mobility of the triplet quenching material is less than the mobility of the hole transporting material.

6. The thin film light emitting device according to claim 1, wherein: The triplet energy level of the triplet quenching material is smaller than the triplet energy level of the hole transporting material.

7. The thin film light emitting device according to claim 1, wherein: The singlet energy level of the triplet quenching material is greater than the singlet energy level of the hole transporting material.

8. The thin film light emitting device according to claim 1, wherein: The mass ratio of the triplet quenching material in the hole transport layer is between 0.0001% and 90%.

9. The thin film light emitting device according to claim 8, wherein: The mass ratio of the triplet quenching material in the hole transport layer is between 1% and 30%.

10. The thin film light emitting device according to any one of claims 1 to 9, wherein: The triplet quenching material includes one or more of transition metal derivatives, acene, acene derivatives, cyclooctadiene, cyclooctadiene derivatives, cyclooctatetraene, cyclooctatetraene derivatives, organic small molecule semiconductor materials, and polymer semiconductor materials.

11. The thin film light emitting device according to any one of claims 1 to 9, wherein: The triplet quenching material includes a transition metal chelate.

12. The thin film light emitting device according to any one of claims 1 to 9, wherein: The triplet quenching material includes one or more of nickel chelate and zinc chelate.

13. The thin film light emitting device according to any one of claims 1 to 9, wherein: The triplet quenching material is selected from the following compounds:

14. The thin film light emitting device according to any one of claims 1 to 9, wherein: The hole transport material and the triplet quenching material are cross-linked to form a polymer.

15. The thin film light emitting device according to any one of claims 1 to 9, wherein: The triplet quenching material is connected to at least a portion of the hole transport material via a chemical bond or a connecting group.

16. The thin film light emitting device according to any one of claims 1 to 9, wherein: The hole transport material is an organic semiconductor material; the light-emitting layer is a quantum dot light-emitting layer.

17. The thin film light emitting device according to any one of claims 1 to 9, wherein: The thin film light emitting device is a blue light thin film light emitting device.

18. A method for preparing a thin film light emitting device, used for preparing the thin film light emitting device according to any one of claims 1 to 13, claim 16 and claim 17; the preparation method comprises preparing an anode, a hole transport layer, a light emitting layer and a cathode; The preparation of the hole transport layer comprises: Dissolving the hole transport material and the triplet quenching material in a solvent to obtain a precursor solution; The hole transport layer is prepared using the precursor liquid by a coating process, a screen printing process or an inkjet printing process.

19. A method for preparing a thin film light emitting device, for preparing the thin film light emitting device according to any one of claims 1 to 14, claim 16 and claim 17; the preparation method comprises preparing an anode, a hole transport layer, a light emitting layer and a cathode; The preparation of the hole transport layer comprises: polymerizing the monomer of the hole transport material and the monomer of the triplet quenching material to form a multifunctional polymer; dissolving the multifunctional polymer in a solvent to obtain a precursor solution; The hole transport layer is prepared using the precursor liquid by a coating process, a screen printing process or an inkjet printing process.

20. A method for preparing a thin film light emitting device, used for preparing the thin film light emitting device according to any one of claims 1 to 13, claim 16 and claim 17; the preparation method comprises preparing an anode, a hole transport layer, a light emitting layer and a cathode; The preparation of the hole transport layer comprises: The hole transport material and the triplet quenching material are co-evaporated to form the hole transport layer.

21. A method for preparing a thin film light emitting device, used for preparing the thin film light emitting device according to any one of claims 1 to 13 and claims 15 to 17; the preparation method comprises preparing an anode, a hole transport layer, a light emitting layer and a cathode; The preparation of the hole transport layer comprises: Synthesizing a multifunctional material, wherein the multifunctional material is a material formed by connecting the hole transport material and the triplet quenching material via a chemical bond or a connecting group; uniformly mixing the multifunctional material and the hole transport material to form an evaporation material; The hole transport layer is formed by using the evaporation material and an evaporation process.

22. A display panel comprising the thin film light emitting device according to any one of claims 1 to 17.

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