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, wherein the hole transport layer comprises a hole transport material and an electron trap material; the LUMO energy level of the electron trap material is smaller than the LUMO energy level of 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, a thin film light-emitting device is provided, comprising an anode, a hole transport layer, a light-emitting layer and a cathode stacked in sequence; wherein the hole transport layer comprises a hole transport material and an electron trap material; and the LUMO energy level of the electron trap material is lower than the LUMO energy level of the hole transport material.

[0006] According to one embodiment of the present disclosure, the LUMO energy level of the electron trap material is not less than the LUMO energy level of the light-emitting layer.

[0007] According to one embodiment of the present disclosure, the mass content of the electron trap material in the hole transport layer is no more than 10%.

[0008] According to one embodiment of the present disclosure, the electron mobility of the electron trap material is no greater than 1×10 -3 cm 2 V - 1 s -1 .

[0009] According to one embodiment of the present disclosure, the rate at which the electron trap material captures electrons is faster than the rate at which holes in the hole transport material capture electrons.

[0010] According to one embodiment of the present disclosure, the rate at which the electron trap material captures electrons is faster than the rate at which excitons on the hole transport material are quenched with holes.

[0011] According to one embodiment of the present disclosure, the electron trap material captures electrons within 1 nm faster than 10 9 / Second.

[0012] According to one embodiment of the present disclosure, the electron trap material captures electrons within 2 nm faster than 10 9 / Second.

[0013] According to one embodiment of the present disclosure, the electron trap material that captures electrons can extract electrons faster than 10 3 / Second.

[0014] According to an embodiment of the present disclosure, the HOMO energy level of the electron trap material is not higher than the HOMO energy level of the hole transport material.

[0015] According to an embodiment of the present disclosure, the mass content of the electron trap material in the hole transport layer gradually decreases along the direction from the anode to the light-emitting layer.

[0016] According to one embodiment of the present disclosure, the hole transport layer includes a plurality of sequentially stacked sublayers; the mass content of the electron trap material in the sublayer closest to the light-emitting layer is less than the mass content of the electron trap material in the sublayer farthest from the light-emitting layer.

[0017] According to one embodiment of the present disclosure, the hole transport material and the electron trap material are cross-linked to form a polymer.

[0018] According to one embodiment of the present disclosure, the electron trap material is connected to at least a portion of the hole transport material via a chemical bond or a connecting group.

[0019] According to an embodiment of the present disclosure, the electron trap material includes one or more of fullerene, fullerene derivatives, small molecule semiconductor materials, and polymer semiconductor materials.

[0020] According to one embodiment of the present disclosure, the electron trap material is selected from the following materials:

[0021]

[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 or an organic 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 electron trap 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] The monomers of the hole transport material and the monomers of the electron trap material are polymerized together 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 electron trap 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 electron trap 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 an evaporation process.

[0041] According to another aspect of the present disclosure, a display panel is provided, comprising the above-mentioned thin film light emitting device.

[0042] 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

[0043] 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.

[0044] Figure 1 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0045] Figure 2 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0046] Figure 3 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

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

[0048] Figure 5 FIG. 4 is a schematic diagram of the structure of a thin film light emitting device in one embodiment.

[0049] Figure 6 is a luminescence intensity curve of each thin film in the first verification example.

[0050] Figure 7 2 are driving voltage-current density curves and driving voltage-luminance curves of various devices in the second verification example.

[0051] Figure 8 2 are driving voltage-current efficiency curves and driving voltage-external quantum efficiency curves of various devices in the second verification example.

[0052] Fig. 9 T90 life curve and voltage change curve of the control device.

[0053] Fig.10 This is the T90 life curve and voltage change curve of the first verification device. DETAILED DESCRIPTION

[0054] 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.

[0055] Although relative terms such as "upper" and "lower" are used in this specification to describe the relative relationship of one component of the illustration to another component, these terms are used in this specification only for convenience, such as according to the orientation of the examples described in the drawings. It is understood that if the device of the illustration is turned upside down, the component described as "upper" will become the component "lower". When a structure is "on" other structures, it may mean that the structure is formed integrally on the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure through another structure.

[0056] The terms "a", "an", "the", "said" and "at least one" are used to indicate the presence of one or more elements / components / etc.; the terms "including" and "having" are used to express an open-ended inclusive meaning and mean that additional elements / components / etc. may exist in addition to the listed elements / components / etc.; the terms "first", "second" and "third" etc. are used merely as labels and are not intended to limit the quantity of their objects.

[0057] 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 1 The 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.

[0058] For example, see Figure 2When 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.

[0059] For another example, see Figure 8 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.

[0060] 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.

[0061] exist Figure 2 and Figure 3 In the example of FIG. 1 , the light-emitting functional layer EFU has a light-emitting stack 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 rate of 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The hole transport material in the hole transport layer is an organic semiconductor material, such as an organic small molecule semiconductor material or a polymer semiconductor material. The destruction of the hole transport material will lead to a decrease in device performance. Electrons leaking from the light-emitting layer to the hole transport layer are one of the key factors in destroying the hole transport material. After the electrons leak from the light-emitting layer to the hole transport layer, they will destroy the hole transport material through a variety of different pathways. For example, hot electrons in an excited state directly destroy the hole transport material, or electrons are captured by holes to form excitons, which destroy the hole transport material through the thermal energy state generated by the nonlinear quenching process.

[0070] In the embodiment of the present disclosure, an electron trap material is introduced into the hole transport layer. The LUMO energy level of the electron trap material is lower than the LUMO energy level of the hole transport material. Therefore, the electrons leaking into the hole transport layer (hereinafter referred to as leakage electrons) can be captured by the electron trap material, for example, directly capturing the leakage electrons, or capturing electrons from the hole transport material combined with the leakage electrons. In this way, the leakage electrons entering the hole transport layer from the light-emitting layer can be at least partially captured by the electron trap material, avoiding the damage to the hole transport material caused by these leakage electrons.

[0071] 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, introducing an electron trap material 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 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.

[0072] 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 electron transport layer can be made of an inorganic semiconductor material, 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 an electron trap material to the hole transport layer to improve the stability of the hole transport layer.

[0073] In one embodiment of the present disclosure, the LUMO energy level of the electron trap material is not less than the LUMO energy level of the light-emitting layer. In this way, it is possible to avoid the LUMO energy level of the electron trap material being too low to form a significant electron leakage channel. Of course, in other embodiments of the present disclosure, the LUMO energy level of the electron trap material may also be lower than the LUMO energy level of the light-emitting layer, but it should not be too low, for example, the LUMO energy level of the electron trap material cannot be 1.5 eV lower than the LUMO energy level of the light-emitting layer.

[0074] In one embodiment of the present disclosure, the mass content of the electron trap material in the hole transport layer is not higher than 10%. In this way, it is possible to avoid the formation of a significant leakage channel due to the excessive content of the electron trap material in the hole transport layer. Further, the mass content of the electron trap material in the hole transport layer is not higher than 5%, for example, 1%, 2%, 3%, 4% or 5%.

[0075] In one embodiment of the present disclosure, the electron mobility of the electron trap material is no greater than 1×10 - 3 cm 2 V -1 s -1 In this way, it is possible to prevent the electron trap material from forming a significant leakage channel in the hole transport layer.

[0076] In one embodiment of the present disclosure, the mass content of the electron trap material in the hole transport layer gradually decreases along the direction from the anode to the light-emitting layer. In this way, the electron trap material near the light-emitting layer can be reduced, especially the electron trap material at the interface between the hole transport layer and the light-emitting layer can be reduced, thereby facilitating the reduction of leakage of the light-emitting layer to the hole transport layer through the electron trap material.

[0077] In another embodiment of the present disclosure, the hole transport layer includes a plurality of sequentially stacked sublayers; the mass content of the electron trap material in the sublayer closest to the light-emitting layer is less than the mass content of the electron trap material in the sublayer farthest from the light-emitting layer. In this way, the electron trap material close to the light-emitting layer can be reduced, especially the electron trap material at the interface between the hole transport layer and the light-emitting layer can be reduced, thereby facilitating the reduction of leakage of electricity from the light-emitting layer to the hole transport layer through the electron trap material.

[0078] In one example, the hole transport layer may include a first sublayer and a second sublayer stacked in sequence from the anode to the light-emitting layer. The mass content of the electron trap material in the second sublayer is lower than the mass content of the electron trap material in the first sublayer. For example, the mass content of the electron trap material in the second sublayer is not higher than half of the mass content of the electron trap material in the first sublayer, for example, 10%, 20%, 30%, 40% or 50% of the mass content of the electron trap material in the first sublayer.

[0079] Of course, in other embodiments of the present disclosure, other means may be used to reduce the mass content of the electron trap material at the interface between the hole transport layer and the light-emitting layer to reduce the electrons leaked from the light-emitting layer to the hole transport layer.

[0080] Of course, in other embodiments of the present disclosure, other means may be used to configure the hole transport layer to reduce the electron leakage channels that may be generated by the electron trap material. For example, the electron trap materials may be designed to be discontinuous to avoid forming a continuous electron leakage channel.

[0081] In one embodiment of the present disclosure, the rate at which the electron trap material captures electrons is faster than the rate at which the holes of the hole transport material capture electrons. In this way, the electron trap material can capture electrons more quickly and efficiently, reducing the ratio of excitons formed by recombination of leaked electrons and holes of the hole transport material, thereby more effectively reducing the damage caused by leaked electrons to the hole transport material.

[0082] In one embodiment of the present disclosure, the rate at which the electron trap material captures electrons is faster than the rate at which the excitons on the hole transport material are quenched with holes. When the holes in the hole transport material capture leaked electrons to form excitons, the excitons can quench with other holes to release / transfer energy, which may cause the hole transport material to be damaged. In an embodiment of the present disclosure, the rate at which the electron trap material captures electrons is greater than the rate at which the excitons on the hole transport material are quenched with holes, which can increase the probability that the hole transport material that has captured the leaked electrons transfers electrons to the electron trap material, thereby reducing the risk of the hole transport material being damaged by the quenching of the excitons on the hole transport material.

[0083] In one example, the rate at which the electron trap material captures electrons is faster than the rate at which holes of the hole transport material capture electrons, and faster than the rate at which excitons on the hole transport material quench with holes.

[0084] In one embodiment of the present disclosure, the electron trap material captures electrons within 1 nm faster than 10 9 / second. This allows the electron trap material to efficiently capture leaked electrons and provide effective protection for the hole transport material. Furthermore, the electron trap material captures electrons within 2 nm faster than 10 9 In this way, the ability of the electron trap material to capture leaked electrons can be further improved, and the protective effect on the hole transport material can be further enhanced.

[0085] In the embodiment of the present disclosure, the electron trap material captures electrons within 1 nm faster than 10 9 / second means that when the leakage electrons enter the range of 1nm around the electron trap material, the rate at which the leakage electrons are captured by the electron trap material is faster than 10 9 / sec. The electron trap material captures electrons within 2nm faster than 10 9 / second means that when the leakage electrons enter the range of 2nm around the electron trap material, the rate at which the leakage electrons are captured by the electron trap material is faster than 10 9 / Second.

[0086] In one embodiment of the present disclosure, the electron trap material that captures electrons extracts electrons faster than 10 3 / second. In this way, it can be ensured that the electron trap material quickly extracts the leaked electrons after capturing them, for example, the captured electrons are quickly recombined with holes in the hole transport material or holes in the electron trap material, so that the electron trap material regains the ability to capture electrons. Since the electron trap material has a lower LUMO energy level, it is not easy for the electron trap material to damage the hole transport layer when extracting electrons.

[0087] In one example, the rate at which the electron trap material captures electrons is faster than the rate at which holes in the hole transport material capture electrons, and faster than the rate at which excitons and holes on the hole transport material are quenched; the rate at which the electron trap material that captures electrons decouples electrons is faster than 10 3 In this way, the electron trap material can quickly capture electrons to protect the hole transport material, and can quickly and safely export electrons, which enables the electron trap material to provide lasting protection for the hole transport layer.

[0088] In one embodiment of the present disclosure, the HOMO energy level of the electron trap material is not higher than the HOMO energy level of the hole transport material. In this way, the electron trap material in the hole transport layer will not produce significant hole traps, thereby avoiding affecting the hole transport performance of the hole transport layer. Of course, in other embodiments of the present disclosure, the HOMO energy level of the electron trap material may also be appropriately higher than the HOMO energy level of the hole transport material, which is 0.1eV, 0.2eV or 0.3eV higher than the HOMO energy level of the hole transport material.

[0089] In one embodiment of the present disclosure, in the hole transport layer, the hole transport material and the electron trap material are two independent materials, that is, there is no strong chemical bond such as a covalent bond between the two. The electron trap material is evenly dispersed in the hole transport layer. In one example, a solution containing a hole transport material and an electron trap 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 electron trap material can be co-evaporated to form a hole transport layer, and the evaporation rate of the hole transport material and the electron trap material determines the content of the electron trap material in the hole transport layer.

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

[0091] Dissolving the hole transport material and the electron trap material in a solvent to obtain a precursor solution;

[0092] The hole transport layer is prepared using the precursor liquid by a coating process, a screen printing process or an inkjet printing process.

[0093] In this example, the hole transport material, electron trap material and solvent should be selected so that the hole transport material and the electron trap material can be evenly and non-aggregatedly distributed in the solution, thereby facilitating the formation of a film layer (such as a hole transport layer) with uniform thickness.

[0094] In another example, the hole transport layer can be prepared by the following method:

[0095] The hole transport material and the electron trap material are co-evaporated to form the hole transport layer.

[0096] For example, the hole transport material and the electron trap 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 electron trap 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 electron trap material can be controlled between 1:1 and 1000:1 according to different doping designs. In this example, the melting point of the electron trap material can be made less than 800°C to ensure that the electron trap material can be effectively evaporated.

[0097] In another embodiment of the present disclosure, the hole transport material and the electron trap 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 electron capture. For example, the chemical formula of the multifunctional polymer is [A] x [B] y , A represents a monomer of a hole transport conductive polymer, and B represents an electron trap material or a monomer thereof. x represents the number of repeating units of A, and y represents the number of repeating units of the electron trap material or a monomer thereof. The polymer may be a random dimer polymer, a diblock polymer, or an alternating polymer.

[0098] In this way, the multifunctional polymer can be directly used as a hole transport layer, and its hole transport material and electron trap material are integrated into the multifunctional polymer, which can ensure the material ratio of the electron trap material and the uniformity of distribution in the hole transport layer. Compared with the direct mixing scheme, the component distribution of the film layer prepared by using this polymer is more stable, and the distribution of its electron trap material will not change with time, annealing conditions, etc., thereby maximizing the reduction of changes in the electrical properties of the hole transport layer caused by the diffusion of the electron trap material and reducing the negative effects of the electron trap material on adjacent layers.

[0099] 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.

[0100] It can be understood that in the polymer, B can be directly a monomer of the electron trap material, or it can be a modified electron trap material, and the modified electron trap material is an electron trap material monomer with a condensation functional group (such as a double bond, isocyanate, etc.) introduced to enable the modified electron trap material to polymerize with A.

[0101] In one example, the electron trap material can be linked to a polymer that serves as a hole transport material through chemical synthesis to form a new polymer.

[0102] In another example, the monomers of the electron trap material and the monomers of the hole transport material may be polymerized together to generate a desired polymer.

[0103] In one example, the hole transport layer can be prepared by the following method:

[0104] The preparation of the hole transport layer comprises:

[0105] The monomer of the hole transport material and the monomer of the electron trap material are polymerized together to form a multifunctional polymer;

[0106] dissolving the multifunctional polymer in a solvent to obtain a precursor solution;

[0107] The hole transport layer is prepared using the precursor liquid by a coating process, a screen printing process or an inkjet printing process.

[0108] In some other embodiments, the electron trap 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 a hole transport material and an electron trap material by a chemical bond or a linking group; for example, the structure of the multifunctional material is a structure formed by directly connecting a hole transport material and an electron trap material by a chemical bond (such as a single bond), or a structure formed by connecting a hole transport material and an electron trap 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 hole transport materials and electron trap materials 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 a hole transport material and an electron trap material. The multifunctional material has both hole transport function and electron capture function. When preparing a hole transport layer, hole transport materials and multifunctional materials can be used as raw materials. For example, a mixture of hole transport materials and multifunctional materials (evaporation materials) is used for co-evaporation to form a hole transport layer.

[0109] For example, the hole transport material is A, the electron trap 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 electron trap material in the hole transport layer can be adjusted.

[0110] It can be understood that one multifunctional material may be connected to one electron trap material or multiple electron trap materials.

[0111] In one example, the hole transport layer can be prepared by the following method:

[0112] Synthesizing a multifunctional material, wherein the multifunctional material is a material formed by connecting the hole transport material and the electron trap material via a chemical bond or a connecting group;

[0113] uniformly mixing the multifunctional material and the hole transport material to form an evaporation material;

[0114] The hole transport layer is formed by using the evaporation material and an evaporation process.

[0115] Optionally, the electron trap material includes one or more of fullerene, fullerene derivatives, small molecule semiconductor materials, and polymer semiconductor materials.

[0116] For example, the electron trap material is selected from the following materials:

[0117]

[0118]

[0119] Among them, the LUMO energy levels and HOMO energy levels of some of the above materials are shown in Table 1:

[0120] Table 1: HOMO and LUMO energy levels of some fullerene materials

[0121] PCBM <![CDATA[PC 71 BM]]> Bis-PCBM ICBA ICTA C60 C70 LUMO(eV) -4.2 -4.2 -3.6 -4.0 -3.36 -4.1 -3.7 HOMO(eV) -6.0 -6.1 -6.0 -5.9 -5.80 -6.3 -6.3

[0122] The fullerene materials in Table 1 have fast electron receiving capabilities and can therefore capture electrons at a high rate. However, fullerene materials have a low LUMO energy level and present a greater risk of leakage. Therefore, when using fullerene materials as electron trap materials, it is necessary to comprehensively balance the performance of various aspects, reduce the risk of leakage of the light-emitting layer through the electron trap material, or match it with a more suitable hole transport material.

[0123] For example, the HOMO energy level of TFB is -5.4 eV, and the LUMO energy level is -2.8 eV. The HOMO energy level of fullerene is relatively low, deeper than -5.4 eV.

[0124] When TFB is used as a hole transport material and fullerene material is used as an electron trap material, fullerene material has a relatively good electron trapping ability, and its HOMO energy level is deep enough to not form a significant hole trap. However, its LUMO energy level is too small, which can easily cause leakage of the light-emitting layer and result in efficiency loss.

[0125] In addition, the LUMO energy levels and HOMO energy levels of some of the above materials are shown in Table 2:

[0126] Table 2: HOMO and LUMO energy levels of some organic semiconductor materials

[0127] IDIC-4CI PM6 (3) (4) (5) LUMO(eV) -3.83 -3.65 -3.37 -3.4 -3.17 HOMO(eV) -5.72 -5.45 -5.39 -7.0 -5.70

[0128] It can be seen from Table 2 that the HOMO energy levels of these organic semiconductor materials are not significantly higher than TFB, and their LUMO energy levels are lower than TFB and closer to TFB. Therefore, from the perspective of HOMO energy level and LUMO energy level, these organic semiconductor materials can form a better energy level match with TFB when used as electron trap materials.

[0129] It can be understood that in the embodiments of the present disclosure, the electron trap material is not limited to the above materials.

[0130] The disclosed embodiment also provides a verification example to verify the protective effect of adding electron trap materials to hole transport materials on hole transport materials.

[0131] First verification example:

[0132] The hole transport material is a 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 electron trap material is PCBM. The hole transport material and the electron trap material are co-dissolved in chlorobenzene to obtain a hole transport layer precursor solution.

[0133] 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 the above-mentioned hole transport layer precursor was spin-coated. The concentration of the material (hole transport material + electron trap 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.

[0134] In this verification example, a first verification film, a second verification film, a third verification film, and a fourth verification film were prepared. In the first verification film, the mass proportion of the electron trap material was 2%; in the second verification film, the mass proportion of the electron trap material was 5%; in the third verification film, the mass proportion of the electron trap material was 10%; in the fourth verification film, the mass proportion of the electron trap material was 20%.

[0135] The first verification film, the second verification film, the third verification film and the fourth verification 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 electron trap material on the hole transport material. Among them, the hole transport material generates photogenerated excitons (electron-hole pairs) after being exposed to light. The electron trap material can protect the hole transport material by capturing the electrons of the photogenerated excitons, thereby reducing a series of damages to the hole transport material caused by the electrons generated by the photogenerated excitons. The verification test results are shown in Figure 6 middle.

[0136] See also Figure 6When the film is irradiated with a detection light of lower intensity, all four films are excited and emit light under the light. However, it is obvious that when the mass content of the electron trap material is between 5% and 20%, the stability of the film is better. This shows that the electron trap 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 four films is from large to small, namely the third verification film C13, the fourth verification film C14, the second verification film C12, and the first verification film C11. This shows that the stability of the film added with electron trap material under strong light is greatly improved, and the stability of the film is correlated with the amount of electron trap material added. Within a certain content range, the more the electron trap material is added, the better the stability of the hole transport material.

[0137] Second verification example

[0138] A control device and three verification devices (a first verification device, a second verification device, and a third verification device) were prepared as follows.

[0139] 1) TFB (as a hole transport material) and PC71BM (as an electron trap material) were dissolved in chlorobenzene to obtain a hole transport layer precursor solution; in the precursor solution, the total mass concentration of TFB and PC71BM was 12 mg / mL.

[0140] 2) Performing UV treatment and ozone treatment on the patterned ITO substrate (ITO layer + glass layer).

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 7) Evaporated cathode, made of aluminum with a thickness of 100 nm.

[0146] In this way, the prepared 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 an electron trap material (except for the control device); the material of the electron transport layer is zinc oxide; and the material of the cathode is aluminum.

[0147] The control device does not contain electron trap materials in the hole transport layer. In the first verification device, the mass proportion of electron trap materials in the hole transport layer is 5%; in the second verification device, the mass proportion of electron trap materials in the hole transport layer is 10%; in the third verification device, the mass proportion of electron trap materials in the hole transport layer is 20%.

[0148] The performance of each of the above devices was tested. The current density and brightness of each device under different voltages were tested, and the test results are shown in Figure 7 The current efficiency and external quantum efficiency of each device were tested at different voltages, and the test results are shown in Figure 8 In. According to Figure 7 and Figure 8 It can be seen that doping electron trap materials in the hole transport layer will lead to a certain efficiency loss.

[0149] The control device was tested at an initial brightness of 1000cd / m 2 The T90 life curve under the condition of , and the voltage change curve under constant current density, the test results are shown in Fig. 9 The first verification device was tested at an initial brightness of 1000 cd / m 2 The T90 life curve under the condition of , and the voltage change curve under constant current density, the test results are shown in Fig.10 In. According to Fig. 9 and Fig.10 It can be seen that by doping the hole transport layer with 5% PC71BM, the T90 life of the device can be extended from 5.5 hours to 33 hours, significantly improving the performance of the device. Figures 7-10 It can be seen that doping the hole transport layer with 5% PC71BM can better improve the stability of the hole transport layer and increase the life of the thin film light-emitting device.

[0150] 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.

[0151] Example 1

[0152] 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 PCBM; the material of the electron transport layer is zinc oxide; and the material of the cathode is aluminum.

[0153] The thin film light emitting device can be prepared by the following method.

[0154] 1) TFB and PCBM are dissolved in chlorobenzene to obtain a hole transport layer precursor solution; in the precursor solution, the total mass concentration of TFB and PCBM is 12 mg / mL; in the film-forming material (UV-1084+TFB), the mass proportion of PCBM is 2% to 20%.

[0155] 2) Performing UV treatment and ozone treatment on the patterned ITO substrate (ITO layer + glass layer).

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 7) Evaporated cathode, made of aluminum with a thickness of 100 nm.

[0161] Example 2

[0162] 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:

[0163]

[0164] 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.

[0165] In this example, the hole transport material and the electron trap material are cross-linked to form a polymer, so that the multifunctional polymer has a hole transport segment and an electron trap segment.

[0166] 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.

[0167] Example 3

[0168] 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 C70; the material of the electron transport layer is zinc oxide; and the material of the cathode is ITO.

[0169] The structure of CBP is as follows:

[0170]

[0171] The thin film light emitting device can be prepared by the following method.

[0172] 1) Perform UV treatment and ozone treatment on a patterned ITO substrate (ITO layer + glass layer).

[0173] 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.

[0174] 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.

[0175] 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 C70 (evaporation rate was 0.1 nm / min), and the co-evaporation was 50 nm.

[0176] 5) Evaporated cathode, the material is molybdenum oxide / silver, the thickness is 3nm / 100nm.

[0177] Example 4

[0178] 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 C60-modified CPB; the material of the electron transport layer is zinc oxide; and the material of the cathode is ITO.

[0179] The structure of C60-modified CPB is as follows:

[0180]

[0181] The thin film light emitting device can be prepared by the following method.

[0182] 1) Perform UV treatment and ozone treatment on a patterned ITO substrate (ITO layer + glass layer).

[0183] 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.

[0184] 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.

[0185] 4) A stable hole transport layer was formed by an evaporation process. The source material was a mixture of CBP and C60-modified CPB (1:1). The evaporation rate was 1 nm / min, and a total evaporation thickness of 50 nm was achieved.

[0186] 5) Evaporated cathode, the material is molybdenum oxide / silver, the thickness is 3nm / 100nm.

[0187] 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.

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; wherein: The hole transport layer comprises a hole transport material and an electron trap material; the LUMO energy level of the electron trap material is lower than the LUMO energy level of the hole transport material.

2. The thin film light emitting device according to claim 1, wherein: The LUMO energy level of the electron trap material is not less than the LUMO energy level of the light emitting layer.

3. The thin film light emitting device according to claim 1, wherein: The mass content of the electron trap material in the hole transport layer is not higher than 10%.

4. The thin film light emitting device according to claim 1, wherein: The electron mobility of the electron trap material is no greater than 1×10 -3 cm 2 V -1 s -1 .

5. The thin film light emitting device according to claim 1, wherein: The electron trap material captures electrons at a faster rate than the holes of the hole transport material capture electrons.

6. The thin film light emitting device according to claim 1, wherein: The electron trap material captures electrons faster than the rate at which excitons on the hole transport material quench with holes.

7. The thin film light emitting device according to claim 1, wherein: The electron trap material captures electrons within 1 nm faster than 10 9 / Second.

8. The thin film light emitting device according to claim 7, wherein: The electron trap material captures electrons within 2nm faster than 10 9 / Second.

9. The thin film light emitting device according to claim 1, wherein: The electron trap material that captures electrons releases electrons faster than 10 3 / Second.

10. The thin film light emitting device according to claim 1, wherein: The HOMO energy level of the electron trap material is not higher than the HOMO energy level of the hole transport material.

11. The thin film light emitting device according to any one of claims 1 to 10, wherein: Along the direction from the anode to the light-emitting layer, the mass content of the electron trap material in the hole transport layer gradually decreases.

12. The thin film light emitting device according to any one of claims 1 to 10, wherein: The hole transport layer includes a plurality of sequentially stacked sublayers; the mass content of the electron trap material in the sublayer closest to the light-emitting layer is less than the mass content of the electron trap material in the sublayer farthest from the light-emitting layer.

13. The thin film light emitting device according to any one of claims 1 to 10, wherein: The hole transport material and the electron trap material are cross-linked to form a polymer.

14. The thin film light emitting device according to any one of claims 1 to 10, wherein: The electron trap material is connected to at least a portion of the hole transport material via a chemical bond or a connecting group.

15. The thin film light emitting device according to any one of claims 1 to 10, wherein: The electron trap material includes one or more of fullerene, fullerene derivatives, small molecule semiconductor materials, and polymer semiconductor materials.

16. The thin film light emitting device according to any one of claims 1 to 10, wherein: The electron trap material is selected from the following materials:

17. The thin film light emitting device according to any one of claims 1 to 10, wherein: The hole transport material is an organic semiconductor material; the light-emitting layer is a quantum dot light-emitting layer or an organic light-emitting layer.

18. The thin film light emitting device according to any one of claims 1 to 10, wherein: The thin film light emitting device is a blue light thin film light emitting device.

19. 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 12 and claims 15 to 18; 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 electron trap 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.

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 and claims 15 to 18; 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 monomer of the hole transport material and the monomer of the electron trap material are polymerized together 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.

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 12 and claims 15 to 18; 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 electron trap material are co-evaporated to form the hole transport layer.

22. 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 12 and claims 14 to 18; 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 electron trap 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.

23. A display panel comprising the thin film light emitting device according to any one of claims 1 to 18.

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