Light-emitting device and light-emitting display device comprising the same

Abstract

To provide a light-emitting display device capable of improving a luminous efficacy and a life together.SOLUTION: A light-emitting element according to an embodiment of the present specification, comprises: a first electrode and a second electrode that are opposite each other; an electron inhibition layer that is provided to between the first electrode and the second electrode; a first light emitting layer; and an electron transport layer. The first light emitting layer can comprise: a first p-type host; a second p-type host; an n-type host; and a dopant. Then, a HOMO energy reference of the first p-type host is lower than the HOMO energy reference of the second p-type host, and a positive hole movement level of the second p-type host is larger than the positive hole movement level of the first p-type host.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This specification relates to a light-emitting device, and more particularly to a light-emitting display device capable of improving both luminous efficiency and lifespan.

Background Art

[0002] With the advent of the full-fledged information age, the field of displays that visually represent electrical information signals has been rapidly developing. Accordingly, many diverse display devices having excellent performance in terms of thinning, weight reduction, and low power consumption have been developed.

[0003] Among these, a light-emitting display device that does not require a separate light source, does not have a separate light source for compactification of the device and vivid color display, and has a light-emitting element in the display panel is considered as a competitive application.

[0004] The light-emitting element includes an anode and a cathode facing each other as electrodes, includes a light-emitting layer between the anode and the cathode, and may include a common layer that transmits holes and electrons to the light-emitting layer.

[0005] On the other hand, the light-emitting element uses a light-emitting material that emits light of different wavelengths for color representation, but differences in the efficiency and lifespan of the light-emitting material may occur depending on the wavelength.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The light-emitting element and the light-emitting display device including the same in this specification attempt to improve the efficiency and lifespan of the light-emitting element simultaneously by changing the material contained inside the light-emitting layer, reduce the parasitic capacitance of the intermediate layer including the light-emitting layer between the first and second electrodes, and increase the capacitance threshold voltage of the intermediate layer to improve reliability.

Means for Solving the Problems

[0007] According to an embodiment of the present specification, a light-emitting device includes a light-emitting layer including a first p-type host having a low HOMO energy level as a p-type host for controlling hole transport and a second p-type host having a high hole mobility, and an n-type host having a high electron mobility, and can reduce the driving voltage, extend the lifetime, and increase the capacitance threshold voltage for the reliability of the device.

[0008] According to an embodiment of the present specification, a light-emitting device includes a first electrode and a second electrode facing each other, and an electron blocking layer and a first light-emitting and electron transport layer provided between the first electrode and the second electrode. The first light-emitting layer includes a first p-type host, a second p-type host, an n-type host, and a dopant. The HOMO energy level of the first p-type host is lower than the HOMO energy level of the second p-type host, and the hole mobility of the second p-type host can be greater than the hole mobility of the first p-type host.

Effects of the Invention

[0009] According to an embodiment of the present specification, a light-emitting device is configured such that the light-emitting layer includes a first p-type host having a low HOMO energy level as a p-type host for controlling hole transport, a second p-type host having a high hole mobility, and an n-type host having a high electron mobility.

[0010] The energy balance with the electron blocking layer can be maintained through the first p-type host having a low HOMO energy level, the charge trapping efficiency in the light-emitting layer can be increased, and the capacitance threshold voltage of the light-emitting layer in the light-emitting device can be maintained or increased.

[0011] The first p-type host prevents excitons or electrons from being released to the electron blocking layer by charge trapping, and the second p-type host can prevent stress at the interface between the electron blocking layer and the light-emitting layer by optimizing the mobility balance with the n-type host due to its high mobility, thereby enhancing the long-life characteristics.

[0012] In addition, there is an advantage that the hole transport characteristics can be enhanced by simultaneously providing the first and second p-type hosts, and the driving voltage can be reduced.

[0013] The light-emitting element and the light-emitting display device including the same according to the present specification can improve the light-emitting efficiency by changing the internal material of the light-emitting layer, reduce the driving voltage, reduce power consumption, thereby reducing environmental pollution, and have a sustainable effect due to the long-life characteristics, so that ESG (Environment / Social / Governance) can be realized.

Brief Description of Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the present invention will be described based on the accompanying drawings. The same reference numerals throughout the specification mean components that are substantially the same. In the following description, when it is determined that a specific description of the technology or configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Also, the names of the components used in the following description are selected in consideration of easy specification preparation and may be different from the names of the parts of the actual product.

[0016] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining various embodiments of the present invention are illustrative, and the present invention is not limited to the matters shown in the drawings. The same drawing reference numerals throughout this specification refer to the same components. Also, in the description of the present invention, when it is determined that a specific description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. When using "including", "having", "becoming", etc. mentioned in this specification, other parts can be added unless "only" is used. When expressing a component in the singular, it includes the case of including a plurality unless otherwise explicitly stated.

[0017] When interpreting the components included in various embodiments of the present invention, it is interpreted to include the error range even without a separate explicit description.

[0018] When explaining the positional relationship in describing various embodiments of the present invention, for example, when explaining the positional relationship between two parts by "on ~", "above ~", "below ~", "next to ~", etc., unless "immediately" or "directly" is used, one or more other parts can also be located between the two parts.

[0019] When explaining the time relationship in describing various embodiments of the present invention, for example, when explaining the chronological relationship by "after ~", "subsequent to ~", "next to ~", "before ~", etc., unless "immediately" or "directly" is used, it can also include the case where it is not continuous.

[0020] In describing various embodiments of the present invention, terms such as "first~" and "second~" can be used to describe various components. However, such terms are only used to distinguish components that are identical or similar to each other. Therefore, in this specification, a component modified by "first~" can be the same as a component modified by "second~" within the technical concept of the present invention unless otherwise mentioned.

[0021] Each feature of the various embodiments of the present invention can be partially or wholly combined or combined with each other, enabling various technical linkages and drives. The various embodiments can be implemented independently of each other or implemented together in an associated relationship.

[0022] In this specification, "doped" means that a substance having physical properties different from those of the substance occupying the majority weight ratio of a layer (the physical properties being different from each other, such as N-type and P-type, organic substance and inorganic substance) is added in a weight ratio of less than 30%. In other words, a "doped" layer means a layer that can be separated into a host substance and a dopant substance of a layer considering the weight ratio. And "undoped" means all cases other than those corresponding to "doped". For example, if a layer is composed of a single substance or substances with the same or similar properties are mixed to form the layer, the layer is included in the "undoped" layer. For example, if at least one of the substances constituting a layer is P-type and not all of the substances constituting the layer are N-type, the layer is included in the "undoped" layer. For example, if at least one of the substances constituting a layer is an organic substance and not all of the substances constituting the layer are inorganic substances, the layer is included in the "undoped" layer. For example, if the substances constituting a layer are all organic substances, and at least one of the substances constituting the layer is N-type and at least one other is P-type, when the weight ratio of the N-type substance is less than 30 wt% or the weight ratio of the P-type substance is less than 30 wt%, it is included in the "doped" layer.

[0023] In this specification, unless otherwise indicated, the LUMO (Lowest Unoccupied Molecular Orbitals Level) energy level and the HOMO (Highest Occupied Molecular Orbitals Level) energy level of a certain layer refer to the LUMO energy level and the HOMO energy level of the substance that occupies the majority of the weight ratio of the layer, such as the LUMO energy level and the HOMO energy level of the host substance.

[0024] In this specification, the HOMO energy level is obtained by measuring the voltage corresponding to the first peak at which electrons jump out of the substance to be measured by the current-voltage measurement method (CV: Cyclic Voltammetry) compared with a reference substance whose HOMO energy level value is known. Here, the electrons that first come out of the substance are the electrons with the weakest binding, the outermost electrons, and the electrons in the HOMO energy level state. NPD (N, N’-Di(1-naphthyl)-N, N’-diphenyl-(1, 1’-biphenyl)-4, 4’-diamine) used as a reference in the experiments and tables of this specification has a HOMO energy level of -5.5 eV and a LUMO energy level of -2.4 eV.

[0025] In this specification, the bandgap energy (Eg) is measured with an ultraviolet-visible spectrometer (UV-visble Spectrometer).

[0026] In this specification, the LUMO energy level is the result of subtracting the bandgap energy from the HOMO energy level of the substance measured above.

[0027] In this specification, the HOMO energy level and the LUMO energy level are measured below the vacuum level of 0 eV and are negative values. When explaining whether it is larger or smaller in comparison between substances, "larger (higher)" means being located higher in the energy band diagram, meaning a smaller absolute value, and "smaller (lower)" means being located lower in the energy band diagram, meaning a larger absolute value.

[0028] Hereinafter, preferred embodiments of this specification will be described based on the accompanying drawings.

[0029] FIG. 1 is a cross-sectional view showing a light-emitting element according to an embodiment of this specification, FIG. 2 is a diagram schematically showing the configuration of the light-emitting layer of FIG. 1, and FIG. 3 is a diagram showing the energy band diagram of the compound contained in the light-emitting layer of FIG. 1. All components of each light-emitting element and each light-emitting display device can be functionally coupled in part or in whole.

[0030] As shown in FIG. 1, a light-emitting element according to an embodiment of this specification includes a first electrode 110 and a second electrode 200 facing each other, and an intermediate layer OS provided between the first electrode 110 and the second electrode 200.

[0031] Either one of the first electrode 110 and the second electrode 200 can be an anode and the other can be a cathode. FIG. 1 shows the case where the first electrode 110 is an anode and the second electrode 200 is a cathode, but the embodiments of this specification are not limited thereto.

[0032] Either one of the first electrode 110 and the second electrode 200 is connected to the thin-film transistor of each sub-pixel provided on the substrate, and the other can receive a common voltage from a plurality of sub-pixels.

[0033] Either the first electrode 110 or the second electrode 200 can be a reflective electrode, and the other can be a transparent electrode or a semi-transmissive electrode. When the first electrode 110 is a reflective electrode and the second electrode 200 is a transparent electrode or a semi-transmissive electrode, the light-emitting element emits light from the top. When the first electrode 110 is a transparent electrode and the second electrode 200 is a reflective electrode, the light-emitting element emits light from the bottom. In one embodiment of the present specification, by forming each of the first electrode 110 and the second electrode 200 as a non-reflective electrode, the light-emitting element can also emit light from both sides. When the first electrode 110 is a reflective electrode, the reflective electrode can include multiple layers. For example, the reflective electrode can include a laminated structure of ITO / Ag or Ag alloy layer / ITO, or Ag or Ag alloy layer / ITO.

[0034] The first electrode 110 is connected to a thin film transistor provided on a substrate, and a signal supplied to each sub-pixel is selectively applied. The second electrode 200 is commonly provided for the sub-pixels, and a common voltage can be applied thereto. By inverting the element configuration of FIG. 1 up and down, the second electrode 200 located on the lower side is connected to the thin film transistor, and the first electrode located on the upper side is provided across a plurality of sub-pixels and a common voltage can be applied thereto.

[0035] An intermediate layer OS is provided between the first and second electrodes 110 and 200, and the light-emitting characteristics of the light-emitting element can be controlled by the thickness of the intermediate layer OS and the layers included in the intermediate layer OS. The intermediate layer OS can include a plurality of organic layers. Some of the plurality of layers included in the intermediate layer OS can further include a metal or other inorganic substance other than a metal. The other inorganic substance other than a metal can be provided as a single body in a part of the plurality of layers, or can also form a complex with an organic substance.

[0036] For example, the intermediate layer OS includes a first common layer CML1, a light-emitting unit EAUN, and an nth common layer CMLn.

[0037] The first common layer CML1 can be, for example, a hole injection layer (HIL). The first common layer CML1 in contact with the first electrode 110 can be a hole injection material of a single organic or inorganic component, or can include a p-type dopant in a hole transporting material. The first common layer CML1 serves to reduce the barrier when receiving holes from the first electrode 110 into the intermediate layer OS.

[0038] The nth common layer CMLn can be an electron injection layer (EIL). The nth common layer CMLn is located in contact with the second electrode 200 and serves to reduce the barrier when electrons are injected from the second electrode 200 into the intermediate layer OS. The electron injection layer EIL can include a halogen atom combined with an alkali metal or alkaline earth metal or an electron transporting organic substance.

[0039] At least one of the first common layer CML1 and the nth common layer CMLn can have a multi-layer structure.

[0040] The light emitting unit EAUN includes a hole transport layer (HTL) 120, an electron blocking layer (EBL) 130, an emitting layer (EML) 150, a hole blocking layer (HBL) 160, and an electron transport layer (ETL) 170.

[0041] Since at least one layer provided in the light emitting unit EAUN can have its thickness or arrangement adjusted for each sub-pixel, it can be distinguished from the above-described first common layer CML1 and nth common layer CMLn. For example, when the substrate is provided with red, green, and blue sub-pixels, it is possible to vary the thickness of any one of the hole transport layer (HTL) 120, the electron blocking layer (EBL) 130, the light-emitting layer (EML) 150, the hole blocking layer (HBL) 160, and the electron transport layer (ETL) 170 for each sub-pixel, change the material of at least one layer, or omit at least one layer from a specific color sub-pixel. Thereby, the optical distance can be adjusted for each emission color.

[0042] The light-emitting layer has a different structure for each sub-pixel, and the remaining layers excluding the light-emitting layer (EML) 150, that is, the first common layer CML1, the hole transport layer (HTL) 120, the electron blocking layer (EBL) 130, the light-emitting layer (EML) 150, the hole blocking layer (HBL) 160, the electron transport layer (ETL) 170, and the nth common layer CMLn can be commonly provided for each sub-pixel.

[0043] At least one of the first common layer CML1, the hole transport layer (HTL) 120, the electron blocking layer (EBL) 130, the light-emitting layer (EML) 150, the hole blocking layer (HBL) 160, the electron transport layer (ETL) 170, and the nth common layer CMLn has a multi-layer structure and can be formed by changing the multi-layers and the content or type of the substance.

[0044] In the light-emitting unit EAUN of this specification, the hole transport layer 120 and the electron blocking layer 130 located below the light-emitting layer (EML) 150 are layers related to hole transport. The hole transport layer 120 and the electron blocking layer 130 have HOMO energy levels (HTL_HOMO, EBL_HOMO) lower than the HOMO energy level of the mixed host of the light-emitting layer 150 so that the holes injected from the first electrode 110 through the first common layer CML1 are smoothly transmitted to the light-emitting layer 150. The hole blocking layer 160 and the electron transport layer 170 located above the light-emitting layer (EML) 150 are layers related to electron transport. In some cases, the hole blocking layer 160 can be omitted in the embodiments of this specification. When the hole blocking layer 160 is omitted, the light-emitting layer 150 can be in direct contact with the electron transport layer 170.

[0045] The hole-blocking layer 160 and the electron transport layer 170 have LUMO energy levels (HBL_LUMO, ETL_LUMO) higher than the LUMO energy level of the mixed host of the light-emitting layer 150 so as to smoothly transmit the electrons injected from the second electrode 200 through the n-th common layer CMLn to the light-emitting layer 150.

[0046] On the other hand, as shown in FIGS. 1 to 3, the light-emitting layer 150 includes a first p-type host PH1, a second p-type host PH2, an n-type host NH, and a dopant D. In the light-emitting layer 150 according to the embodiments of the present specification, the first and second p-type hosts PH1 and PH2 are different from the n-type host NH having electron transporting properties in that both have hole transporting properties, and have different properties from each other as follows.

[0047] As shown in FIG. 3, the first p-type host PH1 has a low HOMO energy level, thereby enhancing the hole trapping efficiency from the adjacent electron blocking layer 130. The holes that enter the light-emitting layer 150 move directly from the first p-type host PH1 to the HOMO energy level of the dopant D or are transmitted to the HOMO energy level of the dopant D via the HOMO energy level of the second p-type host PH2 having a difference smaller than the HOMO energy level of the dopant D. The holes at the HOMO energy level of the dopant D recombine with the electrons transmitted from the LUMO energy level of the n-type host NH to the LUMO energy level of the dopant D to form excitons, which are used for light emission. Since the first p-type host PH1 induces the recombination of the holes trapped at the low HOMO energy level with the electrons that come over with high mobility through the hole blocking layer 160 or the electron transport layer 170 to occur within the light-emitting layer 150, the charge trapping in the light-emitting layer 150 can be enhanced. That is, the first p-type host PH1 causes the recombination of the holes and electrons that form excitons to mainly occur inside the light-emitting layer 150 rather than at the interface between the light-emitting layer and the electron blocking layer, thereby preventing the phenomenon that charges such as excitons are released from the electron blocking layer and preventing the efficiency reduction and lifetime reduction that occur when the formation of the light-emitting region is concentrated between the light-emitting layer and the electron blocking layer at the same time.

[0048] In addition, the charge trap pinning of the light-emitting layer 150 by the first p-type host PH1 can increase the capacitance threshold voltage of the light-emitting element.

[0049] The capacitance threshold voltage means the reference voltage at which the capacitance changes rapidly. In a C-V (Capacitance-Voltage) graph with the voltage on the horizontal axis and the capacitance on the vertical axis, the voltage value at the point where the curve occurs is called the capacitance threshold voltage.

[0050] The capacitance of the light-emitting device is generated in the intermediate layer OS between the first electrode 110 and the second electrode 200. Although the capacitance of the intermediate layer OS is due to the entire intermediate layer OS, in the embodiments of this specification, by increasing the capacitance threshold voltage of the intermediate layer OS by changing the configuration of the light-emitting layer 150 to reduce or prevent the variability of the capacitance between the first and second electrodes 110 and 200, the characteristics of the light-emitting device and the FOS (Front of Screen test) characteristics during the implementation as a light-emitting display device are stabilized.

[0051] Among the plurality of layers forming the intermediate layer OS, the light-emitting layer 150 contains different materials for each sub-pixel emitting a different color, and the other layers other than the light-emitting layer 150 can be commonly provided. Therefore, for each sub-pixel, it is possible to exhibit different capacitance or different capacitance threshold voltages mainly depending on the light-emitting layer.

[0052] If the capacitance threshold voltage is low, the capacitance of the light-emitting device may change significantly due to the low voltage applied between the first and second electrodes, causing characteristic changes. Therefore, the light-emitting device of the embodiments of this specification is provided with a first p-type host PH1 that can increase the charge trapping efficiency in the light-emitting layer to increase the capacitance threshold voltage.

[0053] The second p-type host PH2 has a relatively higher HOMO energy level than the first p-type host PH1 and a higher hole mobility than the first p-type host PH1. Such a HOMO energy level of the second p-type host PH2 has a small energy difference with respect to the HOMO energy level of the dopant D, is easy for hole transfer, and has a high hole mobility. Therefore, it can maintain a high mobility balance with electrons by the n-type host NH in the light-emitting layer, increase the recombination efficiency between holes and electrons, and reduce the generation of charges not used for recombination. Thus, it is possible to prevent the charges not used for recombination from accumulating at the interface between the light-emitting layer and the electron blocking layer, and improve the lifespan of the light-emitting device.

[0054] In the light-emitting device of the present specification, the light-emitting layer includes a first p-type host PH1, a second p-type host PH2, and an n-type host NH together, and can improve the light-emitting efficiency by roles related to hole transport in light emission and charge trapping in the light-emitting layer, can obtain low-voltage driving characteristics, can increase the electrostatic capacitance threshold voltage of the light-emitting device to improve the reliability of the capacitance-voltage characteristics, which are the electrical characteristics of the light-emitting device, and can prevent charges from being biased to the adjacent electron blocking layer to improve the effect of long life.

[0055] In the light-emitting layer (EML) 150, the first p-type host PH1, the second p-type host PH2, and the n-type host NH are pre-mixed as a host material from a single source and supplied in the vapor deposition stage, and are formed on the electron blocking layer 130 together with the dopant vapor-deposited from another source. The first p-type host PH1, the second p-type host PH2, and the n-type host NH can be uniformly distributed throughout the layer thickness of the light-emitting layer (EML) 150.

[0056] The dopant D is contained in an amount of 0.1 wt% to 20 wt% based on the total amount of the host, and adjusts the wavelength of the light emitted from the light-emitting layer 150.

[0057] For example, when the dopant D is a red dopant or a green dopant, an iridium complex dopant can be used. When the dopant D emits red light, it can have an emission peak at a wavelength of 600 nm to 650 nm. When the dopant D emits green light, it can have an emission peak at a wavelength of 510 nm to 580 nm.

[0058] As an example, the light-emitting element of the embodiment of this specification uses first and second p-type hosts PH1 and PH2 having two different physical properties in a structure where the dopant D uses a red dopant, and can enhance the effect of stabilizing the C-V (capacitance-voltage relationship) characteristics of the light-emitting element. On the other hand, the embodiment of this specification is not limited to the example of applying a red dopant, and can be extended to the case of applying dopants of other colors from the viewpoints of lowering the driving voltage, increasing the light-emitting efficiency, achieving the effect of long life, and stabilizing the C-V characteristics.

[0059] On the other hand, in the light-emitting layer (EML) 150, the total amount of the first and second p-type hosts PH1 and PH2 can be the same as or similar to the amount of the n-type host NH. This is to maintain the balance between holes and electrons in a structure where a dopant with a small energy band gap (Eg) is applied. The red dopant has a relatively smaller energy band gap than dopants of other visible light wavelengths.

[0060] When a plurality of hosts are mixed and included in the light-emitting layer (EML), the light-emitting layer (EML) thus formed by mixing has the HOMO energy level and the LUMO energy level of the mixed host from the viewpoint of the barrier with respect to the adjacent layer. Here, in the embodiment of this specification, the HOMO energy level (EMLH_HOMO) of the mixed host (Host) in the light-emitting layer is not the average value of the HOMO energy levels of the hosts, but is closest to the HOMO energy level (PH1_HOMO) of the first p-type host PH1 having a relatively low HOMO energy level among the p-type hosts having hole transport characteristics, as shown in FIG. 3. Also, in the embodiment of this specification, the LUMO energy level (EMLH_LUMO) of the mixed host (Host) in the light-emitting layer is not the average value of the LUMO energy levels of the hosts, but is closest to the LUMO energy level (NH_LUMO) of the n-type host having electron transport characteristics, as shown in FIG. 3. This is because holes and electrons move in the direction with a low energy barrier.

[0061] In the light-emitting layer (EML) 150, not only the first and second p-type hosts PH1, PH2 and the n-type host NH but also the dopant D are uniformly distributed throughout the layer, and excitons are generated by the dopants distributed throughout the light-emitting layer 150 by the energy received from each host, thereby emitting light. On the other hand, the first p-type host PH1 is a tertiary arylamine compound and can be represented by the following Chemical Formula 1. [Chemical Formula]

[0062] Here, X can be independently selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl (Alkyl), C3-C20 cycloalkyl, substituted or unsubstituted C6-C30 aryl (Aryl), and substituted or unsubstituted C5-C30 heteroaryl (Heteracryl).

[0063] A and Ar can each be independently selected from substituted or unsubstituted C6-C30 aryl (Aryl) and substituted or unsubstituted C5-C30 heteroaryl (Heteracryl). A and Ar can be the same as or different from each other.

[0064] R is hydrogen, deuterium, or substituted or unsubstituted aryl.

[0065] The second p-type host PH2 is a tertiary arylamine compound. In some cases, the second p-type host PH2 can use the same core as Chemical Formula 1, but by changing the components of the organic substituents bonded to nitrogen, the HOMO energy level can be adjusted compared to the first p-type host PH1, and the hole mobility can be designed to be faster.

[0066] The n-type host NH can be a substance having a high electron mobility. For example, the n-type host NH can be a quinazoline derivative. The N-type host NH can contain any one of triazole, triazine, benzothiazole, carbazole, benzimidazole, and oxadiazole.

[0067] Hereinafter, an example in which the light-emitting element of this specification is applied to a red sub-pixel will be described.

[0068] FIG. 4 is a diagram showing an energy band diagram of a red light-emitting layer and an adjacent layer in a red light-emitting element according to an embodiment of this specification.

[0069] As shown in FIG. 4, from the viewpoint of hole transport, the HOMO energy levels (HTL_HOMO, EBL_HOMO, EMLH_HOMO, RD_HOMO) of the hole transport layer (HTL), the electron blocking layer (EBL), the mixed host (RHost) of the red light-emitting layer (EML), and the red dopant (RD) increase (rise) in this order. That is, it has the relationship of HTL_HOMO < EBL_HOMO < EMLH_HOMO < RD_HOMO.

[0070] The electron blocking layer is designed to have a LUMO energy level higher than the LUMO energy level of the mixed host (RHost) so as to prevent excitons or electrons from being emitted from the red light-emitting layer (REML).

[0071] Also, from the viewpoint of transport, the LUMO energy levels (HBL_LUMO, EMLH_LUMO, RD_LUMO) of the hole blocking layer (HBL), the mixed host (RHost) of the red light-emitting layer (EML), and the red dopant (RD) decrease (fall) in this order. That is, it has the relationship of HBL_LUMO > EMLH_LUMO > RD_LUMO.

[0072] The hole-blocking layer (HBL) is designed to have a HOMO energy level lower than that of the HOMO energy level of the mixed host (RHost) so as to prevent holes from being emitted from the red-emitting layer (REML).

[0073] On the other hand, the hole-transporting layer (HTL), which has not been described, can have a LUMO energy level (HTL_LUMO) higher than the LUMO energy level (EMLH_LUMO) of the mixed host (RHost) in order to further enhance the blocking of excitons or electrons. However, the examples in this specification are not limited thereto.

[0074] When the hole-blocking layer (HBL) is omitted, the red-emitting layer (REML) can be in direct contact with the electron-transporting layer (ETL). Here, the energy bandgap (Eg) of the electron-transporting layer (ETL) is set to have a LUMO energy level higher than the LUMO energy level of the mixed host (RHost) and a HOMO energy level lower than the HOMO energy level.

[0075] The HOMO energy level (EMLH_HOMO) of the mixed host (RHost) of the red-emitting layer (REML) is lower than the HOMO energy level (RD_HOMO) of the red dopant (RD) (EMLH_HOMO < RD_HOMO), and the LUMO energy level (EMLH_LUMO) of the mixed host (RHost) of the red-emitting layer (REML) can be higher than the LUMO energy level (RD_LUMO) of the red dopant (RD) (EMLH_LUMO > RD_LUMO).

[0076] The triplet energy level (EBL_T1) of the electron-blocking layer (EBL) can be 0.1 eV to 0.7 eV higher than each of the triplet energies (PH1_T1, PH2_T1) of the first and second p-type hosts. Thereby, the transfer of triplet energy from the red-emitting layer to the electron-blocking layer is less likely to occur, and excitons can be confined within the emitting layer.

[0077] Since the second p-type host PH2 with a high hole mobility has a larger LUMO energy level difference (PH2_LUMO - PH1_LUMO) than the HOMO energy level difference (PH2_HOMO - PH1_HOMO) with respect to the first p-type host PH1, the energy band gap (PH2_Eg) of the second p-type host PH2 can be larger than the energy band gap (PH1_Eg) of the first p-type host.

[0078] The energy band gaps of the n-type host NH, the second p-type host PH2, the first p-type host PH1, and the red dopant (RD) can decrease in this order (NH_Eg > PH2_Eg > PH1_Eg > RD_Eg).

[0079] In the following description, the specific physical properties of the first and second p-type hosts and the n-type host used in the experiment will be described.

[0080] The HOMO energy levels, LUMO energy levels, triplet energy levels, and energy band gaps of the first and second p-type hosts and the n-type host used in the experiment are as shown in Table 1, and the glass transition temperature (Tg) and decomposition temperature (Td) are as shown in Table 2.

Table 1

[0081] Table 1 further compares the physical properties of the materials of the electron blocking layer (EBL) having electron and exciton blocking functions together with the first p-type host, the second p-type host, and the n-type host.

[0082] Here, in Table 1, the three materials of the mixed host have component contents of 0.25:0.25:0.5, respectively, and the HOMO energy level, LUMO energy level, triplet level, and energy band gap are observed.

Table 2

[0083] Table 2 shows the glass transition temperature (Tg) and decomposition temperature (Td) during evaporation of each of the host materials PH1, PH2, and NH that form the light-emitting layer, and the glass transition temperature (Tg) and decomposition temperature (Td) during evaporation of the mixed host in a state where the three host materials PH1, PH2, and NH are premixed.

[0084] The glass transition temperature (Tg) is the temperature at which the amorphous part in the host material transitions. Generally, the light-emitting element is driven at a temperature lower than the glass transition temperature of the material. It can be said that the higher the glass transition temperature of the material, the higher the thermal safety or reliability.

[0085] The decomposition temperature (Td) is such that when depositing the light-emitting layer, the premixed mixed host is vaporized and deposited. So, heat is applied above the decomposition temperature, and the premixed mixed host together with the dopant is deposited on the substrate on which the electron blocking layer (EBL) is formed.

[0086] The glass transition temperatures of the first and second p-type hosts PH1 and PH2 are higher than the glass transition temperature of the n-type host NH. However, in the state of the mixed host (3mixed R Host), the glass transition temperature is adjusted close to the average value of the glass transition temperatures of the p-type hosts PH1 and PH2 and the n-type host NH.

[0087] In contrast, since evaporation is possible only when all materials can be vaporized, the decomposition temperature (Td) of the mixed host (3mixed R Host) is higher than the respective decomposition temperatures of the individual host materials (PH1, PH2, NH).

[0088] The glass transition temperature (Tg) and decomposition temperature (Td) of the first p-type host PH1 may differ from those of the second p-type host PH2. For example, the glass transition temperature (Tg) and decomposition temperature (Td) of the first p-type host PH1 may be higher than those of the second p-type host PH2, respectively. However, the examples in this specification are not limited to this. For example, either one or both of the glass transition temperature (Tg) and decomposition temperature (Td) of the first p-type host PH1 may be the same as those of the second p-type host PH2. In some cases, the glass transition temperature (Tg) and decomposition temperature (Td) of the first p-type host PH1 may be lower than at least one of those of the second p-type host PH2. Alternatively, the glass transition temperature (Tg) of the first p-type host PH1 may be lower than that of the second p-type host PH2, and the decomposition temperature (Td) of the first p-type host PH1 may be higher than that of the second p-type host PH2. As yet another example, the glass transition temperature (Tg) of the first p-type host PH1 may be higher than that of the second p-type host PH2, and the decomposition temperature (Td) of the first p-type host PH1 may be lower than that of the second p-type host PH2.

[0089] Hereinafter, the hole mobilities of the first and second hosts are compared using a Hole Only Device (HOD).

[0090] The HOD device is a device proposed to examine the hole transport characteristics of a specific substance. Since it is necessary to compare the hole transport properties of the first p-type host and the second p-type host, the device characteristics are compared using either one of the first p-type host and the second p-type host as the host together with a red dopant in the light-emitting layer. For this purpose, the layers other than the light-emitting layer contain a hole transport material. The hole transport material can include, for example, NPD.

[0091] The configuration of the HOD device including the first p-type host as the host is as follows.

[0092] That is, a first electrode (AND) having a stacked structure of ITO / Ag / ITO is provided on a substrate.

[0093] A first hole injection layer (HIL1) containing a p-type dopant and a hole transport material is provided on the first electrode.

[0094] Next, a hole transport layer (HTL) containing a hole transport material is provided on the first hole injection layer.

[0095] Next, a hole transport auxiliary layer (RHTL) containing a hole transport material for auxiliary adjustment of the optical distance is provided on the hole transport layer.

[0096] An electron blocking layer (EBL) containing an electron blocking material is provided on the hole transport auxiliary layer.

[0097] Next, a red light emitting layer (REML[PH1:RD]) is provided by doping a first p-type host with a red dopant.

[0098] Next, a second hole injection layer (HIL2) containing the same p-type dopant and hole transport material as the first hole injection layer is provided on the red light emitting layer.

[0099] Next, the configuration of the HOD element is completed by forming a second electrode (CAT) of aluminum (Al) on the second hole injection layer.

[0100] The configuration of the HOD element including a second p-type host as a host is the same except that the first p-type host is replaced with the second p-type host when forming the red light emitting layer of the above configuration.

[0101] FIG. 5 is a graph comparing the J-V characteristics of the first host and the second host using the HOD element.

[0102] As shown in FIG. 5 and Table 3, when comparing Hole Only Device (HOD) elements using the first p-type host and the second p-type host as hosts respectively, it can be seen that relatively, the second p-type host has a higher current density at the driving voltage.

Table 3

[0103] Referring to FIG. 5, when the hole mobility of the first p-type host is set to 1.00 at a driving voltage of 3V, it can be seen that the hole mobility of the second p-type host is approximately 1.56. Such hole mobility can be obtained by J (current density)-V (voltage) analysis of the same HOD element. The examples in this specification are not limited to the examples of hole mobility presented in Table 3.

[0104] The hole mobility of each of the predetermined material layers can be measured by replacing the intermediate layer with the predetermined material layer in a Hole Only Device (HOD) element having an intermediate layer between opposing electrodes and analyzing the J-V characteristics with the same E-field. In an HOD element with the same E-field of 500V / μm, the hole mobility of the red emission layer (REML) having the first and second p-type hosts PH1, PH2, n-type host NH, and red dopant (RD) together is 4.44E-08 cm 2 / V·s, and the hole mobility of the electron blocking layer (EBL) can be 2.82E-07 cm 2 / V·s. Also, the electron mobility of each of the predetermined material layers can be measured by replacing the intermediate layer with the predetermined material layer in an Electron only device (EOD) element having an intermediate layer between opposing electrodes and analyzing the J-V characteristics with the same E-field. In an EOD element with the same E-field of 500V / μm, the electron mobility of the red emission layer (REML) having the first and second p-type hosts PH1, PH2, n-type host NH, and red dopant (RD) together is 1.91E-06 cm 2 / V·s, and the electron mobility of the hole blocking layer (HBL) is 1.49E-07 cm 2It can be / V·s. Experiments measuring the hole mobility and electron mobility of such a layer were conducted at the same E-field of 500 V / μm. The charge mobility (hole mobility or electron mobility) can vary depending on the structure of the HOD element or the EOD element or the use of other equipment.

[0105] The red light-emitting element is driven at approximately 2V to 4V. When driving the first and second p-type hosts PH1 and PH2 together, it can be seen that the hole mobility of the second p-type host PH2 is always greater than that of the first p-type host PH1 within the driving voltage range of the red light-emitting element.

[0106] Hereinafter, the element characteristics depending on the ratio of the host material in the light-emitting element according to an embodiment of the present specification will be described.

[0107] In the following experiment, a red light-emitting element having the configuration of the element in FIG. 1 is used, but there is a difference in that a hole transport auxiliary layer (RHTL) is further formed between the hole transport layer (HTL) 120 and the electron blocking layer (EBL) 130 for adjusting the optical distance.

[0108] Referring to FIG. 1, the light-emitting element of the first experimental example (EX1) has the following configuration.

[0109] A first electrode (AND) 110 having a stacked structure of ITO / Ag / ITO is provided on the substrate.

[0110] On the first electrode, a first common layer CML1 containing a p-type dopant and a hole transport material is provided.

[0111] Next, a hole transport layer (HTL) 120 containing a hole transport material is provided on the first common layer CML1.

[0112] Next, a hole transport auxiliary layer (RHTL) containing a hole transport material for assisting in adjusting the optical distance is provided on the hole transport layer (HTL) 120.

[0113] Next, an electron blocking layer (EBL) 130 containing an electron blocking substance is provided on the hole transport auxiliary layer (RHTL).

[0114] Next, a red light-emitting layer (REML[PH1:NH:RD]) 150 is provided by doping a host in which an n-type host is mixed with a first p-type host with a red dopant.

[0115] Next, a hole blocking layer (HBL) 160 containing a hole blocking substance is provided on the red light-emitting layer 150.

[0116] Next, an electron transport layer (ETL) 170 is provided on the hole blocking layer (HBL).

[0117] Next, a first n-common layer CMLn containing an electron injection substance is provided on the electron transport layer (ETL) 170.

[0118] Next, the structure of the light-emitting element according to the first experimental example (EX1) is completed by forming a second electrode (CAT) 200 with a semi-transparent metal, such as an AgMg alloy, on the first n-common layer CMLn.

[0119] The second experimental example (EX2) includes a second p-type host as a p-type host except for the first p-type host when forming the red light-emitting layer 150, and the red light-emitting layer (REML) has a configuration of PH2:NH:RD.

[0120] Examples 3 to 5 used the first and second p-type hosts and the n-type host together as shown in the examples of this specification, and only the composition of the red light-emitting layer was different from that of the first experimental example (EX1) described above. That is, as shown in Tables 4 and 5, in common among Examples 3 to 5 (EX3, EX4, EX5), the n-type host NH was set to 0.5 times the total host content, and the content ratio of the first p-type host and the second p-type host was changed. In the third experimental example (EX3), the content ratio of the first p-type host and the second p-type host was set to 0.17:0.33. In the fourth experimental example (EX4), the content ratio of the first p-type host and the second p-type host was set to 0.25:0.25. In the fifth experimental example (EX5), the content ratio of the first p-type host and the second p-type host was set to 0.33:0.17.

[0121] Figure 6 is a graph showing the J-V characteristics of Examples 1 to 5. Figure 7 is a graph showing the lifetimes of Examples 1 to 5.

Table 4

[0122] Based on the first experimental example (EX1) that applied the first p-type host among the two p-type hosts PH1 and PH2, compare Examples 2 to 5 (EX2, EX3, EX4, EX5) in terms of the threshold voltage change (Δthreshold voltage), drive voltage change (Δdrive voltage), efficiency, and lifetime of the light-emitting device.

[0123] On the other hand, in the experiment according to Table 4 above, the threshold voltage change (Δthreshold voltage), drive voltage change (Δdrive voltage), and efficiency were measured in an environment with a luminance of 600 nit and a temperature of 25°C of the light-emitting device, and the lifetime was measured in an accelerated environment with a luminance of 600 nit and a temperature of 35°C of the light-emitting device. The lifetime was measured as the time until the luminance reached 95% from the initial luminance and was compared with the lifetime of the first experimental example (EX1).

[0124] Compared with the first experimental example (EX1) including a single first p-type host PH1 having low HOMO energy level characteristics as a p-type host, the second experimental example (EX2) including a single second p-type host PH2 having high hole mobility has a decreased turn-on threshold voltage of the light-emitting device and also has an improved effect on the lifetime, but the luminous efficiency is lower than that of the first experimental example (EX1).

[0125] On the other hand, different from the first and second experimental examples (EX1, EX2), it can be confirmed that any of the third to fifth experimental examples (EX3, EX4, EX5) including the first and second p-type hosts PH1 and PH2 together have an efficiency at the same level or higher and a more improved lifetime compared with the first experimental example (EX1). That is, the third to fifth experimental examples (EX3, EX4, EX5) including the first and second p-type hosts PH1 and PH2 together mean that high efficiency and long lifetime can be achieved compared with the first and second experimental examples (EX1, EX2) including a p-type host of a single material.

[0126] Referring to Table 4, the host content ratios of the first p-type host PH1, the second p-type host PH2, and the n-type host NH can be diverse. For example, the content ratio of the first p-type host PH1 can be the same as, smaller than, or larger than the content ratio of the second p-type host PH2. In various examples of this specification, the content ratio of the first p-type host PH1 can be the same as or different from the content ratio of the n-type host NH. That is, the content ratio of the first p-type host PH1 can be 0.00 times to 0.50 times the content ratio of the n-type host NH. Here, 0.50 times means that the content ratios of the first p-type host PH1 and the n-type host NH are the same. Similarly, that is, the content ratio of the second p-type host PH2 can be 0.00 times to 0.50 times the content ratio of the n-type host NH. In various examples of this specification, the content ratio of the combination of the first and second p-type hosts PH1 and PH2 can be the same as or different from the content ratio of the n-type host NH. The content ratio of the combination of the first and second p-type hosts PH1 and PH2 can be 0.50 times or more in the red light-emitting layer. The examples of this specification are not limited thereto. For example, in one example of the examples of this specification, the content ratio of the combination of the first and second p-type hosts PH1 and PH2 may not be larger than the content ratio of the n-type host NH.

[0127] In FIG. 6, the graphs of the first to fifth experimental examples (EX1 to EX5) having an S-curve on the left side depend on the exponential current density on the right vertical axis, and the graphs of the first to fifth experimental examples (EX1 to EX5) on the right side depend on the current density on the left vertical axis. In FIG. 6, the variation (ΔV) of the driving voltage can be found in the graphs of the first to fifth experimental examples (EX1 to EX5) on the left side, and in the graphs of the first to fifth experimental examples (EX1 to EX5) on the right side, the point in time when the curve occurs corresponds to the voltage value on the horizontal axis being the threshold voltage (ΔVth) of the light-emitting element.

[0128] Referring to FIG. 6, it can be seen that the threshold voltage value of the light-emitting element decreases in the second to fifth experimental examples (EX2, EX3, EX4, EX5) compared to the first experimental example (EX1).

[0129] Referring to FIG. 7, it can be confirmed that the lifetime is improved in the second to fifth experimental examples (EX2, EX3, EX4, EX5) compared to the first experimental example (EX1).

[0130] In the results of Table 4, the threshold voltage change (ΔVth) means the comparison of the threshold voltage required at the turn-on of the light-emitting element with the threshold voltage of the first experimental example (EX1), and has a different meaning from the capacitance threshold voltage described above. That is, the threshold voltage change (ΔVth) means that it has a voltage required at turn-on only when the value is small, and a small value means an element with excellent front-of-screen (FOS) characteristics.

[0131] In Table 5 below, the component content ratios of the three materials of the mixed host are changed, and the HOMO energy level, LUMO energy level, triplet level, and energy bandgap are observed.

Table 5

[0132] Here, the LUMO energy level of the mixed host (3mixed R Host) is close to the LUMO energy level of the n-type host NH in common for each experimental example (EX1, EX2, EX3).

[0133] Since the HOMO energy level of the mixed host (3mixed R Host) depends on the hole transport characteristics, it is close to the HOMO energy level of the p-type host. In the examples of this specification, two types of p-type hosts are used. In the third experimental example (EX3), it shows a tendency to be close to the HOMO energy level of the second p-type host PH2 with a relatively high content. In the fourth and fifth experimental examples (EX4, EX5), when the content ratio of the first and second p-type hosts PH1 and PH2 is 1:1 or more, it shows a tendency to be closer to the lower HOMO energy level of the first p-type host PH1. Including the first and second p-type hosts PH1 and PH2, the HOMO energy level of the mixed host is closest to the HOMO energy of the first p-type host PH1.

[0134] As shown in Table 5, in the third to fifth experimental examples (EX3, EX4, EX5), the difference between the LUMO energy level and the HOMO energy level of the mixed host in the first light-emitting layer is 2.29 eV to 2.31 eV, which is smaller than the energy band gap of the individual hosts.

[0135] Hereinafter, not only the first to fifth experimental examples but also more diverse examples of hosts will be described together with the changes in device characteristics and capacitance characteristics due to material changes when using a plurality of hosts.

Table 6

[0136] In the experiments of Table 6, the first to ninth experimental examples (EX1 to EX9) have the device configurations described based on Table 5 above. The first to fifth experimental examples (EX1 to EX5) have the HOMO energy levels, LUMO energy levels, energy band gaps, and mobility characteristics of the first p-type host PH1, the second p-type host PH2, and the n-type host NH described in Tables 1 to 3.

[0137] The sixth experimental example (EX6) uses the first p-type host as the p-type host and the n-type host NHA, which has lower LUMO energy level characteristics than the above-described n-type host NH and has a slow electron mobility, as the n-type host to form the host of the light-emitting layer.

[0138] The seventh experimental example (EX7) uses the second p-type host as the p-type host and the n-type host NHA, which has lower LUMO energy level characteristics than the above-described n-type host NH and has a slow electron mobility, as the n-type host to form the host of the light-emitting layer.

[0139] The eighth experimental example (EX8) uses the third p-type host PH3, which has a higher HOMO energy level than the first p-type host and each of the first and second p-type hosts and has a slow hole mobility, as the p-type host and uses the above-described n-type host NH to form the host of the light-emitting layer.

[0140] The ninth experimental example (EX9) uses the third p-type host PH3, which has a higher HOMO energy level than the second p-type host and each of the first and second p-type hosts and has a slow hole mobility, as the p-type host and uses the above-described n-type host NH to form the host of the light-emitting layer.

[0141] Figure 8 is a graph showing the C-V characteristics of the first to fifth experimental examples.

[0142] The capacitance threshold voltage (Vth@Cap) means the reference voltage at which the capacitance changes abruptly. In a C-V graph with the voltage on the horizontal axis and the capacitance on the vertical axis, the voltage value at the point where the curve occurs is called the capacitance threshold voltage.

[0143] Referring to Figure 8 and Table 6, it can be seen that the capacitance threshold voltage of the second experimental example (EX2) is the lowest in the second experimental example (EX2), and the capacitance threshold voltages increase in both the first experimental example (EX1) and the third to fifth experimental examples (EX3 to EX5).

[0144] In FIG. 8, the threshold voltage of the fourth experimental example (EX4) is displayed.

[0145] This means that there is no change in the capacitance of the light-emitting element at a voltage value below the threshold voltage. If the capacitance threshold voltage increases in both the first experimental example (EX1) and the third to fifth experimental examples (EX3 to EX5), it means that the reliability of the element is improved by the voltage change.

[0146] On the other hand, the maximum value of the capacitance (Max Cap) has a difference of at most 0.03E-09 in the first to fifth experimental examples (EX1 to EX5) and has similar levels.

[0147] The sixth experimental example (EX6) uses a single first p-type host PH1 and NH:NHA as the n-type host. In this case, the lifetime characteristics are very low, indicating the limit of the light-emitting element.

[0148] The seventh experimental example (EX7) uses a single second p-type host PH2 and NH:NHA as the n-type host. In this case, although the lifetime characteristics are improved, the luminous efficiency tends to decrease.

[0149] The eighth experimental example (EX8) and the ninth experimental example (EX9) use either one of the first and second p-type hosts of the above-described third to fifth experimental examples (EX3 to EX5) instead of using them together. Compared with the case of using a single p-type host, they have an effect equal to or better than that of the first experimental example (EX1) in terms of luminous efficiency and lifetime.

[0150] That is, the first and second experimental examples (EX1, EX2) and the sixth to ninth experimental examples (EX6 to EX7) are red light-emitting elements, meaning that making the p-type host among the p-type host and the n-type host into a plurality of different types is more effective than providing the n-type host with a plurality of different types.

[0151] FIG. 9 is a cross-sectional view showing a light-emitting element according to an embodiment of the present specification.

[0152] As shown in FIG. 9, a light-emitting device according to an embodiment of the present specification includes an intermediate layer OS having two or more stacks S1, S2, ... that emit light of the same color between a first electrode 110 and a second electrode 200. Each of the stacks S1, S2, ... can be divided into charge generation layers CGL1, CGL2, ....

[0153] Each of the stacks S1, S2, ... can include the structure of the light-emitting unit EAUN of the hole transport layer (HTL), electron blocking layer (EBL), light-emitting layer 150, hole blocking layer (HBL), and electron transport layer (ETL) described above with reference to FIG. 1. Optionally, the hole transport layer (HTL) can further include a hole transport auxiliary layer below or above it.

[0154] The light-emitting layer of each stack includes a first p-type host PH1, a second p-type host PH2, and an n-type host NH having different physical properties from each other, and a dopant D.

[0155] The p-type hosts are different in that the HOMO energy level (PH1_HOMO) of the first p-type host PH1 is lower than the HOMO energy level (PH2_HOMO) of the second p-type host PH2 (PH1_HOMO_1 < PH2_HOMO2), and the hole mobility of the second p-type host is greater than the hole mobility of the first p-type host.

[0156] When a plurality of stacks are provided, the light-emitting efficiency of the light-emitting layer can be further improved, and together with the reduction of the threshold voltage, improvement of the light-emitting efficiency, and long-life effect of the light-emitting device described in the third to fifth experimental examples (EX3, EX4, EX5), there is an effect of increasing the capacitance threshold voltage to improve the safety of the device.

[0157] FIG. 10 is a cross-sectional view showing a light-emitting display device according to an embodiment of the present specification.

[0158] As shown in FIG. 10, a light-emitting display device according to an embodiment of the present specification can apply the above-described light-emitting device to at least one of a plurality of sub-pixels SP1, SP2, SP3, SP4.

[0159] As shown in FIG. 10, a light-emitting display device according to an embodiment of the present specification may include a substrate 100 having a plurality of sub-pixels, a light-emitting element ED provided in common on the substrate 100, and a thin-film transistor TFT provided in each of the sub-pixels and connected to the first electrode 110 of the light-emitting element ED.

[0160] The thin-film transistor TFT includes, as an example, a gate electrode 102, a semiconductor layer 104, and a source electrode 106a and a drain electrode 106b connected to both sides of the semiconductor layer 104. And, an upper portion of a site where the channel of the semiconductor layer 104 is located may further include a channel protection layer to prevent direct connection between the source / drain electrodes 106a, 106b and the semiconductor layer 104. The thin-film transistor TFT may include a buffer layer 101 on the substrate 100 and may be located on the buffer layer 101.

[0161] A gate insulating film 103 is provided between the gate electrode 102 and the semiconductor layer 104.

[0162] The semiconductor layer 104 may be, for example, any one of an oxide semiconductor, amorphous silicon, and polycrystalline silicon, or may also be composed of a combination of two or more of the foregoing. For example, when the semiconductor layer 104 is an oxide semiconductor, the heating temperature required for forming the thin-film transistor can be lowered, so that the degree of freedom in using the substrate 100 is high and it can be advantageously applied to a flexible display device.

[0163] The gate electrode 102 is provided on the gate insulating film 103, and an interlayer insulating film 105 may be further provided between the gate electrode 102 and the source electrode 106a / drain electrode 106b.

[0164] Also, the drain electrode 106b of the thin-film transistor TFT may be connected to the first electrode 110 in a contact hole CT region provided in the first and second protective films 107, 108.

[0165] The first protective film 107 is provided primarily to protect the thin-film transistor TFT, and color filters 109R, 109G, and 109B can be provided on the upper part of the first protective film 107.

[0166] A second protective film 108 is provided on the first protective film 107 including the color filters 109R, 109G, and 109B.

[0167] When including red sub-pixels, green sub-pixels, blue sub-pixels, and white sub-pixels (W_SP) as a plurality of sub-pixels, the light-emitting element ED described in FIG. 1 or FIG. 9 can be applied to at least the red sub-pixels. In some cases, in each sub-pixel, the light-emitting layer can be divided and patterned. Some of the sub-pixels with different emission colors may be provided with a hole transport auxiliary layer, and the rest may not be provided. In sub-pixels with different emission colors, the hole transport auxiliary layer is further provided to compensate for the optical distance. For example, the thickness of the hole transport auxiliary layer can be greater in the red sub-pixels than in the green sub-pixels or the blue sub-pixels.

[0168] The second protective film 108 is formed under the first electrode 110. The first electrode 110 is formed on the surface of the second protective film 108 except for the contact hole CT and is connected to either the drain electrode 106b or the source electrode 106a of the thin-film transistor TFT, and receives an electrical signal from the thin-film transistor TFT.

[0169] Here, it can be said that the thin-film transistor array substrate 1000 includes the thin-film transistor TFT and the first and second protective films 107 and 108 from the substrate 100.

[0170] The light-emitting element ED is formed on a thin-film transistor array substrate 1000 including a bank 119 that defines a light-emitting portion BH. The light-emitting element ED includes a reflective first electrode 110, a second electrode 200 of a reflective transmissive electrode facing the first electrode 110, and an intermediate layer OS described in FIG. 1 or FIG. 9 provided between the first electrode 110 and the second electrode 200. For example, if the light-emitting element ED of FIG. 1 or FIG. 9 is provided in a red sub-pixel, the first common layer CML1, the hole transport layer (HTL), the electron blocking layer (EBL), the hole blocking layer (HBL), the electron transport layer (ETL), the n-th common layer (CML2), or the charge generation layer (CGL) can also be continuous in the remaining sub-pixels. The energy band gap varies depending on the dopant provided for each light-emitting layer, and the host and the light-emitting dopant can be changed and used.

[0171] Therefore, when the red light-emitting layer of the red sub-pixel uses two types of p-type hosts and one type of n-type host, in the light-emitting layers of other colors, a single p-type host or a single n-type host can be used, or either one or both of a plurality of p-type hosts and a plurality of n-type hosts can be used.

[0172] Since the hosts used in the light-emitting layers of different colors and the energy band gap of the dopant of the emission color are different from those of the red dopant, at least one of the red light-emitting layers can be different for optimal emission.

[0173] The first electrode 110 is divided by each sub-pixel, and the remaining layers except the first electrode 110 of the light-emitting element ED can be integrally provided for the entire display area without division by sub-pixel.

[0174] Either one of the first electrode 110 or the second electrode 200 can be connected to the thin-film transistor TFT.

[0175] By providing a capping layer (not shown) on the second electrode 200, the light extraction efficiency can be improved and the light-emitting element ED can be protected.

[0176] A sealing layer or a sealing substrate (not shown) can be further provided on the second electrode 200 so as to protect the light-emitting element ED.

[0177] Although the illustrated example is shown in consideration of top emission, the embodiments of this specification are not limited thereto.

[0178] The light-emitting element according to the embodiments of this specification is configured to include a first p-type host having a low HOMO energy level as a p-type host that controls hole transport and a second p-type host having a high hole mobility, and an n-type host having a high electron mobility.

[0179] The first p-type host having a low HOMO energy level can maintain the energy balance with the electron blocking layer, increase the charge trapping efficiency in the light emission, and maintain or increase the capacitance threshold voltage of the light-emitting layer in the light-emitting element.

[0180] On the other hand, it will be apparent to those of ordinary skill in the art to which this specification pertains that this specification is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible without departing from the technical idea of this specification.

Claims

1. A first electrode and a second electrode facing each other; An electron blocking layer, a first light emitting layer, and an electron transport layer provided between the first electrode and the second electrode; The first light emitting layer includes a first p-type host, a second p-type host, an n-type host, and a dopant; The HOMO energy level of the first p-type host is lower than the HOMO energy level of the second p-type host; The hole mobility of the second p-type host is greater than the hole mobility of the first p-type host. A light emitting device.

2. The HOMO energy level of the mixed host of the first light emitting layer is closer to the HOMO energy level of the first p-type host than to the HOMO energy level of the second p-type host; The LUMO energy level of the mixed host of the first light emitting layer is closest to the LUMO energy level of the n-type host among the first p-type host, the second p-type host, and the n-type host. The light emitting device according to claim 1.

3. The difference between the LUMO energy level and the HOMO energy level of the mixed host of the first light emitting layer is 2.29 eV to 2.31 eV. The light emitting device according to claim 2.

4. The dopant is a red dopant; The HOMO energy level of the mixed host of the first light emitting layer is lower than the HOMO energy level of the dopant; The LUMO energy level of the mixed host of the first light emitting layer is higher than the LUMO energy level of the dopant. The light emitting device according to claim 2.

5. The absolute value of the LUMO energy level of the first p-type host is greater than the triplet energy level of the first p-type host; The absolute value of the LUMO energy level of the second p-type host is smaller than the triplet energy level of the second p-type host. The light emitting device according to claim 1.

6. The triplet energy level of the electron blocking layer is 0.1 eV to 0.7 eV higher than the respective triplet energy levels of the first p-type host and the second p-type host. The light emitting device according to claim 1.

7. The energy band gap of the second p-type host is greater than the energy band gap of the first p-type host. The light emitting device according to claim 1.

8. The energy band gaps are in decreasing order of the n-type host, the second p-type host, the first p-type host, and the dopant. The light emitting device according to claim 1.

9. The light-emitting element according to claim 1, wherein the dopant has a light emission peak at a wavelength of 600 nm to 650 nm.

10. The light-emitting element according to claim 1, further comprising a hole blocking layer between the first light-emitting layer and the electron transport layer.

11. The light-emitting element according to claim 10, wherein a difference between the LUMO energy level of the first light-emitting layer and the LUMO energy level of the electron blocking layer is larger than a difference between the HOMO energy level of the first light-emitting layer and the HOMO energy level of the hole blocking layer.

12. The light-emitting element according to claim 1, wherein a total amount of the first p-type host and the second p-type host is the same as an amount of the n-type host.

13. At least one of between the first electrode and the electron blocking layer and between the electron transport layer and the second electrode includes one or more stacks, the stack includes a first common layer, a second light-emitting layer, and a second common layer, The light-emitting element according to claim 1, wherein the second light-emitting layer emits light having the same hue as the first light-emitting layer.

14. The light-emitting element according to claim 13, wherein the second light-emitting layer includes the first p-type host, the second p-type host, and a red dopant.

15. The first p-type host and the second p-type host are tertiary arylamine compounds, The light-emitting element according to claim 1, wherein a component of an organic substituent bonded to nitrogen in the tertiary arylamine compound of the second p-type host is different from the arylamine compound of the first p-type host.

16. The light-emitting element according to claim 1, wherein the n-type host includes any one of triazole, triazine, benzothiazole, carbazole, benzimidazole, and oxadiazole.

17. The light-emitting element according to claim 1, wherein a content ratio of the first p-type host is the same as or smaller than a content ratio of the second p-type host.

18. A first electrode and a second electrode facing each other, including an electron blocking layer, a first light-emitting layer, and an electron transport layer provided between the first electrode and the second electrode, the first light-emitting layer includes a first p-type host, a second p-type host, an n-type host, and a dopant, The HOMO energy level of the first p-type host is different from the HOMO energy level of the second p-type host, An organic light-emitting device, wherein at least one of the first p-type host and the second p-type host is a tertiary arylamine compound. **Claim 19** The organic light-emitting device according to claim 18, wherein the hole mobility of the second p-type host is greater than the hole mobility of the first p-type host. **Claim 20** A substrate including a plurality of sub-pixels, A thin film transistor provided for each of the plurality of sub-pixels, A light-emitting display device including the light-emitting device according to any one of claims 1 to 19, which is connected to the thin film transistor in at least one of the plurality of sub-pixels.

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