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

Abstract

To provide a light-emitting device and a light-emitting display device, capable of improving a luminous efficacy and a life.SOLUTION: A light-emitting device 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 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 p-type host; a first n-type host; a second n-type host; and a dopant. A LUMO energy reference of the first n-type host is higher than the LUMO energy reference of the second n-type host, and a positive hole movement level of the first n-type host is higher than a positive hole movement level of the second n-type host, and is lower than the positive hole movement level of the p-type host. The light-emitting device of the present specification maintains an efficiency and a capacitance-voltage characteristic, and can obtain an effect of a low voltage and a long life.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This specification relates to a light-emitting device, and more particularly, to a light-emitting device and a light-emitting display device capable of improving light-emitting 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 and has a light-emitting element in the display panel without a separate light source for device compactness and vivid color display is considered a competitive application.

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

[0005] On the other hand, the light-emitting device 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 for each wavelength.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The light-emitting device and the light-emitting display device including the same according to this specification can simultaneously improve the efficiency and lifespan of the light-emitting device by changing the material included 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 further increase the capacitance threshold voltage of the intermediate layer to improve reliability.

Means for Solving the Problems

[0007] The light-emitting device according to an embodiment of the present specification includes 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 may include a p-type host, a first n-type host, a second n-type host, and a dopant. The LUMO energy level of the first n-type host is higher than the LUMO energy level of the second n-type host, and the hole mobility of the first n-type host may be higher than the hole mobility of the second n-type host and lower than the hole mobility of the p-type host. The light-emitting device of the present specification can maintain efficiency and capacitance-voltage characteristics, and exhibit the effects of low voltage and long life.

Advantages of the Invention

[0008] The light-emitting device according to an embodiment of the present specification includes a light-emitting layer including a p-type host, a first n-type host, a second n-type host, and a dopant. The LUMO energy level of the first n-type host is higher than the LUMO energy level of the second n-type host, and the hole mobility of the first n-type host may be larger than the hole mobility of the second n-type host and smaller than the hole mobility of the p-type host.

[0009] In the light-emitting device according to an embodiment of the present specification, the first n-type host having a high LUMO energy level, high hole mobility, and high electron mobility controls the electron and hole speeds supplied to the green dopant together, and continuously maintains the balance at the recombination of holes and electrons abundantly supplied by the high content of the p-type host to maintain the hole-electron balance in the light-emitting layer, increase the charge trapping efficiency into the light emission, and maintain or increase the capacitance threshold voltage of the light-emitting layer of the light-emitting device.

[0010] In the light-emitting device according to an embodiment of the present specification, holes and electrons are supplied into the light-emitting layer at high speed by the p-type host and the second n-type host, preventing excitons or electrons from being released to the electron blocking layer by charge trapping, and preventing stress at the interface between the electron blocking layer and the light-emitting layer by optimizing the mobility balance by the mixed host, thereby enhancing the long-life characteristics.

[0011] In the light-emitting element according to the embodiment of the present specification, the p-type host is provided in a relatively larger content compared to the n-type host, so that the balance with the high electron mobility of the dopant can be achieved within the light-emitting layer, the charge trapping can be improved by rich hole supply to maintain the threshold voltage characteristics of the light-emitting element, and the capacitance threshold voltage can be improved by the second n-type host, so that the reliability of the element can be improved.

[0012] The light-emitting element according to the present specification and the light-emitting display device including the same can change the internal material of the light-emitting layer to improve the light-emitting efficiency, reduce the driving voltage, reduce the power consumption, thereby reducing the 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

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The same reference numerals throughout the specification mean substantially the same components. In the following description, when it is determined that a detailed description of a technique 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.

[0015] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining various embodiments of the present invention are exemplary, and the present invention is not limited to the matters shown in the drawings. The same drawing reference numerals throughout the specification refer to the same components. Also, in the description of the present invention, when it is determined that a detailed description of a related known technique 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 a component is expressed in the singular, it includes the case of including a plurality unless otherwise explicitly stated.

[0016] When interpreting the components included in various embodiments of the present invention, even without a separate explicit description, it shall be interpreted as including an error range.

[0017] When explaining various embodiments of the present invention and describing the positional relationship, for example, when explaining the positional relationship between two parts by means of "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.

[0018] When explaining various embodiments of the present invention and describing the time relationship, for example, when explaining the chronological relationship by means of "after ~", "subsequent to ~", "next to ~", "before ~", etc., unless "immediately" or "directly" is used, it can also include cases where it is not continuous.

[0019] When explaining various embodiments of the present invention, terms such as "first ~", "second ~", etc. can be used to describe various components, but such terms are only used to distinguish components that are the same or similar to each other. Therefore, in this specification, unless otherwise mentioned, the components modified by "first ~" can be the same as the components modified by "second ~" within the technical concept of the present invention.

[0020] Each feature of various embodiments of the present invention can be partially or wholly combined or combined with each other, various technical linkages and drives are possible, and various embodiments can be implemented independently of each other, or can also be implemented together in an associated relationship.

[0021] 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 (physical properties different from each other are, for example, N-type and P-type, organic substances and inorganic substances) is added in a weight ratio of less than 30%. In other words, a "doped" layer means a layer in which the host substance and the dopant substance of a layer can be separated considering the weight ratio. And "undoped" means all cases other than those corresponding to "doped". For example, when a layer is composed of a single substance or substances with the same or similar properties are mixed, that 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 that layer are N-type, that 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 that layer are inorganic substances, that layer is included in the "undoped" layer. For example, when all of the substances constituting a layer are organic substances, and at least one of the substances constituting that layer is N-type and at least one of the other substances is P-type, if 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.

[0022] In this specification, the LUMO (Lowest Unoccupied Molecular Orbitals Level) energy level and the HOMO (Highest Occupied Molecular Orbitals Level) energy level of a layer mean the LUMO energy level and the HOMO energy level of the substance occupying the majority weight ratio of that layer, for example, the host substance, unless otherwise indicated as the LUMO energy level and the HOMO energy level of the dopant substance doped in that layer. In this specification, the HOMO energy level is obtained by measuring the voltage corresponding to the first peak at which electrons escape from a substance by the current-voltage measurement method (CV: Cyclic Voltammetry) for the substance to be measured, 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 used as a reference in the experiments and tables of this specification has -5.5 eV as the HOMO energy level and -2.4 eV as the LUMO energy level.

[0023] In this specification, the band gap energy (Eg) is measured with an ultraviolet-visible spectrometer (UV-visble Spectrometer).

[0024] In this specification, the LUMO energy level is obtained by subtracting the band gap energy from the HOMO energy level of the substance measured above.

[0025] 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 they are larger or smaller during the comparison between substances, "larger (higher)" means being located higher in the energy band diagram and having a smaller absolute value, and "smaller (lower)" means being located lower in the energy band diagram and having a larger absolute value.

[0026] Figure 1 is a cross-sectional view showing a light-emitting element according to an embodiment of this specification, and Figure 2 is a diagram schematically showing the configuration of the light-emitting layer of Figure 1. Figure 3 is a diagram showing the energy band diagram of the compound contained in the light-emitting layer of Figure 1.

[0027] As shown in Figure 1, the 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.

[0028] Either the first electrode 110 or 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.

[0029] Either the first electrode 110 or 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.

[0030] Either one of the first electrode 110 and 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 upper side. 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 lower side. In one embodiment of this 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 a plurality of layers. For example, the reflective electrode can include a laminated structure of ITO / Ag or an Ag alloy layer / ITO, or an Ag or an Ag alloy layer / ITO.

[0031] The first electrode 110 is connected to the thin film transistor provided on the 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 over a plurality of sub-pixels and a common voltage can be applied thereto.

[0032] 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 form a complex with an organic substance.

[0033] For example, the intermediate layer OS includes a first common layer CML1, a light-emitting unit EAUN, and an nth common layer CMLn.

[0034] 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.

[0035] 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 or an electron transporting organic substance bonded to an alkali metal or an alkaline earth metal.

[0036] At least one of the first common layer CML1 and the nth common layer CMLn can have a multi-layer structure. In one embodiment of the present specification, at least one of the first common layer CML1 and the nth common layer CMLn can be another light-emitting unit that emits the same color as the light-emitting unit EAUN. A charge generation layer can be provided between adjacent light-emitting units EAUN. In another embodiment of the present specification, at least one of the first common layer CML1 and the nth common layer CMLn can be another light-emitting unit that emits a color different from that of the light-emitting unit EAUN.

[0037] The light-emitting unit EAUN includes a hole transport layer (HTL), a 120 electron blocking layer (EBL) 130, a green emitting layer (GEML) 150, a hole blocking layer (HBL) 160, and an electron transport layer (ETL) 170.

[0038] Since at least one layer included in the light-emitting unit EAUN can have its thickness or arrangement adjusted for each sub-pixel, it can be classified into a first common layer CML1 and an nth common layer CMLn that are commonly provided for the sub-pixels.

[0039] In a structure where the color emitted by the light-emitting layer is different for each sub-pixel, the green emitting layer (GEML) 150 can be provided for the green sub-pixel, a red emitting layer (not shown) can be provided for the red sub-pixel, and a blue emitting layer (not shown) can be provided for the blue sub-pixel. In a structure where the color emitted by the light-emitting layer is different for each sub-pixel, the first common layer CML1, the hole transport layer (HTL) 120, the electron blocking layer (EBL) 130, the hole blocking layer (HBL) 160, and the electron transport layer (ETL) 170 can be commonly provided for each sub-pixel. For the purpose of adjusting the optical distance, etc., it is also possible to change the thickness of at least one of the hole transport layer (HTL) 120, the electron blocking layer (EBL) 130, the hole blocking layer (HBL) 160, the electron transport layer (ETL) 170, and the nth common layer CMLn for each sub-pixel, change the material of at least one layer, omit at least one layer from a specific color sub-pixel, or add a hole auxiliary layer or an electron auxiliary layer.

[0040] In a structure where the light-emitting layer is different for each sub-pixel, the nth common layer CMLn can be commonly provided for each sub-pixel.

[0041] As shown in FIGS. 1 to 3, the green light-emitting layer 150 includes a p-type host PH1, a first n-type host PH2, a second n-type host NH, and a dopant GD. In the green light-emitting layer 150 according to the embodiments of the present specification, the p-type host PH is excellent in hole transportability to transfer holes to the dopant GD, and the first and second n-type hosts NH1 and NH2 are excellent in electron transportability to transfer electrons to the dopant GD.

[0042] In the green light-emitting layer 150, the content of the p-type host PH is more than the total content of the first and second n-type hosts NH1 and NH2, and sufficiently supplies holes to the dopant D.

[0043] In the green light-emitting layer 150, since the dopant GD has an electron mobility greater than the hole mobility, by including the p-type host PH in the green light-emitting layer 150 in a content greater than the total content of the first and second n-type hosts NH1 and NH2, holes are sufficiently supplied in the green light-emitting layer 150 by the quantitative adjustment of the host.

[0044] Also, the balance of exciton formation due to hole-electron recombination is maintained by adjusting the ratio of the p-type host PH and the first and second n-type hosts NH1 and NH2.

[0045] The n-type host material NH in the green light-emitting layer 150 includes different NH1 and NH2, and is different in HOMO-LUMO energy level and hole mobility.

[0046] Specifically, the first and second n-type hosts NH1 and NH2 are n-type hosts, each having a high electron mobility. However, the first n-type host NH1 has a higher LUMO energy level closer to the HOMO-LUMO energy level of the dopant GD than the second n-type host NH2, and is different in having a higher hole mobility than the second n-type host NH2.

[0047] The first n-type host NH1, which has both high hole mobility and high electron mobility, can transfer electrons to the dopant GD in the green light-emitting layer 150 and maintain hole-electron balance with the dopant GD, thereby reducing the driving voltage of the light-emitting device and increasing its lifespan. That is, in response to the quantitatively abundant and continuous supply of holes from the p-type host PH present in a large amount in the green light-emitting layer 150, the two n-type hosts NH1 and NH2 supply electrons, and the first n-type host NH1, which is excellent in both electron mobility and hole mobility, continuously adjusts the balance between holes and electrons in the dopant GD, thereby improving the lifespan of the light-emitting device.

[0048] The second n-type host NH2 has high electron mobility. Since it can trap electrons transmitted from the adjacent hole blocking layer 160 and / or electron transport layer 170 and quickly transfer them to the dopant GD through the first n-type host NH1, the high efficiency of the green light-emitting layer 150 can be maintained. In addition, the second n-type host NH2 has the effect of increasing the capacitance threshold voltage of the light-emitting device and improving the reliability of the light-emitting device.

[0049] Here, the electron mobility of the second n-type host NH2 can be greater than that of the first n-type host NH1. This is because the second n-type host NH2, which has a relatively low LUMO energy level, quickly traps electrons from the hole blocking layer 160 and / or electron transport layer 170 and smoothly transfers the electrons to the first n-type host NH1 and the dopant D in the green light-emitting layer 150.

[0050] The LUMO energy level (NH1_LUMO) of the first n-type host NH1 can be lower than the LUMO energy level (GD_LUMO) of the dopant GD. The n-type host material NHM containing the first and second n-type hosts NH1 and NH2 has LUMO energy levels (NH1_LUMO, NH2_LUMO) that are lower than the LUMO energy level (GD_LUMO) of the dopant GD respectively, but the n-type host material NHM is excellent in electron mobility and can easily transfer electrons to the LUMO energy level (GD_LUMO) of the adjacent dopant GD.

[0051] The electron mobility in the green light-emitting layer 150 can gradually increase in the order of the p-type host PH, the first n-type host NH1, the dopant GD, and the second n-type host NH2. The first n-type host NH1 has a lower electron mobility than the dopant GD, but by having excellent hole mobility, the first n-type host NH1 adjusts the hole-electron ratio in the dopant GD that changes over time by the excellent inherent electron mobility of the dopant GD. Thus, the luminous efficiency is maintained high by the continuous hole-electron recombination in the green light-emitting layer 150, preventing the charges not used for recombination from moving to the interface of the green light-emitting layer 150 and preventing the phenomenon of shortened lifespan.

[0052] The second n-type host NH2 is a substance having a low HOMO energy level and a low LUMO energy level, has high electron mobility, and plays a role of inducing hole and electron charge traps in the dopant GD. Thereby, the second n-type host NH2 plays a role of increasing the efficiency and the electrostatic capacitance threshold voltage of the light-emitting element and reducing the maximum capacitance value of the light-emitting element.

[0053] If the green light-emitting layer is provided with a p-type host having a single excellent hole mobility and an n-type host having a single excellent electron mobility, the initial luminous efficiency is excellent, but since the balance between holes and electrons cannot be maintained in the green dopant, the lifespan shows a tendency to decrease significantly compared to the examples of this specification. This will be described later by experiments.

[0054] Also, the LUMO energy level (PH_LUMO) of the p-type host PH is the highest among the components included in the green light-emitting layer 150. Since the electron blocking layer 130 adjacent to the green light-emitting layer 150 has a LUMO energy level higher than the LUMO energy level (PH_LUMO) of the p-type host, it confines the exciton or electron so that it is not exceeded by the electron blocking layer 130 and is maintained in the green light-emitting layer 150.

[0055] In the light-emitting unit EAUN of this specification, the hole transport layer 120 and the electron blocking layer 130 located below with the green light-emitting layer (GEML) 150 as the center are layers related to hole transport. The hole transport layer 120 and the electron blocking layer 130 function to smoothly transmit the holes injected from the first electrode 110 through the first common layer CML1 to the green light-emitting layer 150. The HOMO energy levels of the hole transport layer 120 and the electron blocking layer 130 are approximately lower than the HOMO energy level of the p-type host PH of the green light-emitting layer 150.

[0056] The hole blocking layer 160 and the electron transport layer 170 located above with the green light-emitting layer (GEML) 150 as the center 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 green light-emitting layer 150 can be in direct contact with the electron transport layer 170. The hole blocking layer 160 and the electron transport layer 170 are such that the LUMO energy levels of the hole blocking layer 160 and the electron transport layer 170 are approximately higher than the LUMO energy levels of the first and second n-type hosts (NH1, NH2) of the green light-emitting layer 150 so as to smoothly transmit the electrons injected from the second electrode 200 through the nth common layer CMLn to the green light-emitting layer 150.

[0057] On the other hand, prior to the explanation of the increase in the capacitance threshold voltage mentioned as the effect of the second n-type host NH2, the meaning of the capacitance threshold voltage will be explained.

[0058] 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.

[0059] The capacitance of the light-emitting element 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 electrostatic capacitance threshold voltage of the intermediate layer OS due to the change in the configuration of the green light-emitting layer 150 to reduce or prevent the variability of the capacitance between the first and second electrodes 110 and 200, when configuring as a light-emitting element characteristic and a light-emitting display device, the FOS (Front of Screen test) characteristic related to the light-emitting characteristic coming out from the front is stabilized.

[0060] Among the plurality of layers forming the intermediate layer OS, the green light-emitting layer 150 has a configuration different from that of sub-pixels emitting other colors. Among the configurations of the light-emitting element shown in FIG. 1, layers other than the green light-emitting layer 150 can be provided in common to other sub-pixels.

[0061] When the light-emitting display device includes a green sub-pixel, a red sub-pixel, and a blue sub-pixel and reproduces white, since the visibility and relative luminous efficiency are high, more green sub-pixels are provided than sub-pixels of other colors.

[0062] As a result, the green sub-pixel has a higher sensitivity due to electrical characteristics than sub-pixels of other colors. The green sub-pixel particularly has a green light-emitting layer and has a configuration different from that of the red light-emitting layer.

[0063] In recent years, the light-emitting layer has been developed from the viewpoint of maintaining the hole-electron balance between the provided hosts to lower the driving voltage and increase the efficiency.

[0064] The light-emitting device according to an embodiment of the present specification includes a green light-emitting layer. In particular, not only from the viewpoints of driving voltage and efficiency, but also to increase the reliability of the green light-emitting layer 150 against visual changes, the capacitance threshold voltage in the light-emitting device by the green light-emitting layer is increased to prevent capacitance fluctuations below the threshold voltage. For this purpose, the light-emitting device of the present specification includes, in the green light-emitting layer, together with a p-type host PH, a first n-type host NH1 having both high hole mobility and high electron mobility, and a second n-type host NH2 having high electron mobility and low HOMO energy level and low LUMO energy level. By doing so, the driving voltage is reduced and the efficiency is improved. Furthermore, the balance between holes and electrons is continuously maintained by the dopant GD, and the capacitance threshold voltage is increased along with the improvement of the light-emitting efficiency, thereby reducing the sensitivity of capacitance change in the green light-emitting device and improving the device reliability.

[0065] In the light-emitting device according to the embodiment of the present specification, although the light-emitting layer is exemplified by the green light-emitting layer, it is also applicable to light-emitting layers of other colors. For example, when the light-emitting layer includes a p-type host PH that mainly transfers holes to the dopant and an n-type host that mainly transfers electrons, if it includes an n-type host material NHM that transfers electrons and the dopant energy band diagram has a LUMO energy level deviating from the energy band diagram of the n-type host material NHM, it can be applied when it includes an additional n-type host having a LUMO energy level closer to the LUMO energy level of the dopant material and having high hole mobility.

[0066] If the capacitance threshold voltage is low, the capacitance of the light-emitting device may change significantly even by a low voltage applied between the first and second electrodes, causing a change in characteristics. Therefore, the light-emitting device of the embodiment of the present specification includes a p-type host PH and a second n-type host NH2 that can increase the charge trapping efficiency in the light-emitting layer to increase the capacitance threshold voltage. In addition, the first n-type host NH1 has high hole mobility and adjusts the rich hole supply rate by the p-type host PH, so that recombination of holes and electrons can finally occur optimally by the dopant GD.

[0067] The dopant GD is contained in an amount of 0.1 wt% to 20 wt% based on the total content of the host, and adjusts the wavelength of the light emitted from the light-emitting layer 150.

[0068] For example, the dopant GD can be a green dopant. The dopant GD can have a heavy metal such as iridium or platinum as the core. As an example, an iridium complex dopant can be used as the dopant. When the dopant GD emits green light, it can have an emission peak at a wavelength of 500 nm to 580 nm.

[0069] The light-emitting device of the embodiment of the present specification, as an example, has a dopant GD as a green dopant, and is included in a single p-type host PH and first and second n-type hosts NH1 and NH2 having two different physical properties. Along with the effects of reducing the driving voltage, improving the efficiency, and extending the lifespan, it can lower the maximum capacitance of the light-emitting device and increase the capacitance threshold voltage of the light-emitting device, thereby enhancing the effect of stabilizing the C-V (capacitance-voltage relationship) characteristics. On the other hand, the embodiments of the present specification are not limited to the example of applying a green dopant, and can also be extended to the case of applying dopants of other colors from the perspective of lowering the driving voltage, increasing the light-emitting efficiency, and stabilizing the C-V characteristics along with the effect of extending the lifespan.

[0070] On the other hand, in the green light-emitting layer (GEML) 150, the total amount of the first and second n-type hosts NH1 and NH2 can be less than the amount of the p-type host PH. Considering all of the lifespan, efficiency, voltage change of the light-emitting device, and the threshold voltage, when the total content of the hosts in the green light-emitting layer (GEML) 150 is set to 1 , the content of the single p-type host PH is set to 0.6 to 0.8, and the remaining amount of the hosts is the total amount of the first and second n-type hosts NH1 and NH2. If the content of the p-type host PH exceeds 0.8 or is less than or equal to 0.6 in terms of the total content of the hosts, the hole-electron balance may not be maintained in the green light-emitting layer, resulting in a possible decrease in efficiency and lifespan.

[0071] A plurality of hosts included in the emission layer (EML) can be mixed first during evaporation to form a mixed host composition, and the mixed host composition and the dopant can be supplied from other sources and co-evaporated onto a substrate on which a light-emitting element is formed.

[0072] In the green emission layer (EML) 150, not only the p-type host PH and the first and second n-type hosts NH1 and NH2 but also the dopant D are uniformly distributed throughout the layer, and excitons are generated by the dopants distributed throughout the emission layer 150 by the energy received from each host, thereby emitting light.

[0073] On the other hand, the p-type host PH can be composed of a substituted or unsubstituted 3,3'-biscarbazole compound. For example, the p-type host PH can be represented by the following Chemical Formula 1.

Chemical Formula

[0074] Ar1 and Ar2 can be independently selected from a substituted or unsubstituted aryl having 6 to 30 carbon atoms and a substituted or unsubstituted heteroaryl having 5 to 30 carbon atoms.

[0075] R1 to R 14 can be independently selected from hydrogen, deuterium, halogen, cyano (CN), alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms, and substituted or unsubstituted heteroaryl having 5 to 30 carbon atoms.

[0076] The first n-type host NH1 can include a triazene substituent or a pyrimidine substituent.

[0077] The second n-type host NH2 can be represented by the following Chemical Formula 2.

Chemical Formula

[0078] In Chemical Formula 2, at least two of X1 to X3 are N (nitrogen). When none of X1 to X3 is N, it may be C-R.

[0079] R, R 15 、R 16 may be independently selected from hydrogen, deuterium, halogen, cyano (CN), alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms, and substituted or unsubstituted heteroaryl having 5 to 30 carbon atoms.

[0080] Ar3 and Ar4 may be independently selected from substituted or unsubstituted aryl having 6 to 30 carbon atoms, and substituted or unsubstituted heteroaryl having 5 to 30 carbon atoms.

[0081] The electron blocking layer 130 can be selected from substances having hole transporting properties and having a large energy band gap, and in particular, substances having a high LUMO energy level. The LUMO energy level of the electron blocking layer 130 can be 0.7 eV or more greater than that of the p-type host PH having the highest LUMO energy level in the green light emitting layer 150, and 1 eV or more greater than that of the first n-type host NH1.

[0082] All of the HOMO energy level and LUMO energy level described in this specification are negative values. When it is said that the HOMO energy level or LUMO energy level of substance A is higher than that of substance B, it means that the absolute value of the HOMO energy level or LUMO energy level is smaller.

[0083] In Table 1 below, the characteristics of the internal substances of the light emitting layer and the substances of the adjacent layers used in the experiment are compared.

Table 1

[0084] As shown in FIG. 3 and Table 1, in the green light-emitting layer 150, the LUMO energy level (NH1_LUMO) of the first n-type host NH1 is -3.10 eV, the LUMO energy level (NH2_LUMO) of the second n-type host NH2 is -3.49 eV, and it can be seen that the LUMO energy level (NH1_LUMO) of the first n-type host NH1 is higher than the LUMO energy level (NH2_LUMO) of the second n-type host NH2.

[0085] In Table 1, for each material of the green light-emitting layer, the current density was set to 10 mA / cm 2 and the driving voltage was measured for each of the Hole Only Device (HOD) and the Electron Only Device (EOD).

[0086] The HOD device is for detecting the hole mobility of the evaluation substance. The HOD device evaluated in Table 1 has a laminated structure of the first electrode (AND) of ITO / Ag / ITO laminate, the first hole injection layer (HIL1) co-evaporated with the p-type dopant and the hole transport substance, the hole transport layer (HTL) containing the hole transport substance, the hole transport assisting layer (GHTL), the electron blocking layer (EBL), the green light-emitting layer (GEML) doped with the green dopant in the evaluation substance, the second hole injection layer (HIL2), and the second electrode (CAT).

[0087] The EOD device is for detecting the electron mobility of the evaluation substance. The EOD device evaluated in Table 1 has a laminated structure of the first electrode (AND) of ITO / Ag / ITO laminate, the first electron injection layer (EIL1) co-evaporated with the n-type dopant and the n-type charge generation substance, the green light-emitting layer (GEML) doped with the green dopant in the evaluation substance, the hole blocking layer (HBL), the electron transport layer (ETL), the second electron injection layer (EIL2), and the second electrode (CAT).

[0088] The p-type host PH has a driving voltage of 2.3 V for the HOD element but 13.0 V for the EOD element, indicating that the resistance for hole transport is low while that for electron transport is high. That is, it can be seen that the p-type host PH is a material with excellent hole mobility but very low electron mobility.

[0089] On the other hand, the first n-type host NH1 has a driving voltage of 2.9 V for the HOD element and 1.4 V for the EOD element, showing that it has excellent hole transportability and electron transportability. That is, the first n-type host NH1 is a material with both excellent hole mobility and electron mobility.

[0090] The second n-type host NH2 has a driving voltage of 7.6 V for the HOD element and 0.9 V for the EOD element, indicating that it has high resistance during hole transport and low resistance during electron transport. It can be seen that the second n-type host NH2 is a material with high electron mobility but low hole mobility.

[0091] In the experiment of Table 1, a large driving voltage for the HOD element and the EOD element means high resistance, and the mobility is inversely proportional to the driving voltage.

[0092] As shown in Table 1, the LUMO energy level of the first n-type host NH1 is higher than that of the second n-type host NH2.

[0093] Also, the hole mobility of the first n-type host NH1 can be larger than that of the second n-type host NH2 and smaller than that of the p-type host PH.

[0094] At the same current density of the EOD element, the driving voltage of the second n-type host NH2 being smaller than that of the first n-type host NH1 means that the electron mobility of the second n-type host NH2 is larger than that of the first n-type host NH1.

[0095] The LUMO energy level of the first n-type host NH can be lower than that of the dopant.

[0096] As shown in Table 1, in the green light-emitting layer, at the same current density of the EOD element, the driving voltage gradually decreases in the order of the p-type host PH, the first n-type host NH1, the dopant GD, and the second n-type host NH2. Conversely, the electron mobility can increase in the order of the p-type host PH, the first n-type host NH1, the dopant GD, and the second n-type host NH2.

[0097] The LUMO energy level of the p-type host PH is -2.64 eV, which is the highest among the components contained in the light-emitting layer. The LUMO energy level of the electron blocking layer (EBL) is -1.88 eV, which can be higher than the LUMO energy level of the p-type host PH. The reason why the LUMO energy level of the electron blocking layer (EBL) has a large difference and is higher than the LUMO energy levels of the materials contained in the green light-emitting layer is to prevent electrons from being emitted from the green light-emitting layer through the electron blocking layer (EBL).

[0098] As shown in Table 1, the energy band gap of the first n-type host NH1 is 3.0 eV, which can be larger than the energy band gap of 2.75 eV of the second n-type host (NH2).

[0099] The p-type host PH and the first and second n-type hosts NH1 and NH2 can all transfer the energy required for exciton formation to the triplet energy level of the dopant GD in the green light-emitting layer (GEML). In this regard, the triplet energy levels of the p-type host PH and the first and second n-type hosts NH1 and NH2 can be larger than the triplet energy level of the red dopant. Among these, in terms of sequential electron transfer, the triplet energy level of the second n-type host NH2 can be larger than the triplet energy level of the first n-type host NH1.

[0100] The HOMO energy level of the p-type host PH is, for example, -5.62 eV, which can be lower than the -5.13 eV of the HOMO energy level of the dopant. The HOMO energy level of the p-type host PH has a difference of approximately 0.1 eV to 0.6 eV with respect to the HOMO energy level of the dopant GD and can be lower.

[0101] The material of the hole-blocking layer (HBL) not described in Table 1 has a HOMO energy level of -5.36 eV, which is lower than the HOMO energy level of the dopant GD, so it functions to prevent holes from coming over from the green emission layer (GEML).

[0102] Hereinafter, the device characteristics and the capacitance-voltage characteristics of the light-emitting device are examined by experiments while changing the contents of the p-type host material and the first and second n-type host materials of the emission layer.

[0103] The experiments are first divided into the first to fifth experimental examples (EX1, EX2, EX3, EX4, EX5), the contents of the p-type host material and the first and second n-type host materials in the emission layer are made different from each other, and the remaining configurations are the same.

[0104] The laminated structure of the light-emitting devices of the first to fifth experimental examples (EX1 to EX5) is as follows as shown in FIG. 1.

[0105] That is, the light-emitting devices of the first to fifth experimental examples have a laminated structure of a first electrode (AND) 110 of an ITO / Ag / ITO laminate, a hole injection layer (HIL) in which a p-type dopant and a hole transport material are co-evaporated, a hole transport layer (HTL) 120 containing a hole transport material, a hole transport auxiliary layer (GHTL), an electron blocking layer (EBL) 130, and a green emission layer (GEML) 150 doped with a green dopant in any one of the host material combinations of the first to fifth experimental examples (EX1 to EX5), a hole blocking layer (HBL) 160, an electron transport layer (ETL) 170, an electron injection layer EIL, and a second electrode (CAT) 200.

[0106] In the first to fifth experimental examples (EX1 to EX5), the content of the p-type host PH was set to 0.7, and the content ratios of the first and second n-type hosts NH1 and NH2 with the remaining content of 0.3 were made different from each other. That is, in the first experimental example (EX1), the content of the single first n-type host NH1 was set to 0.3, and in the second experimental example (EX2), the content of the single second n-type host NH2 was set to 0.3. In the third experimental example (EX3), the content ratio of the first n-type host NH1 and the second n-type host NH2 was set to 0.2:0.1. In the fourth experimental example (EX4), the content ratio of the first n-type host NH1 and the second n-type host NH2 was set to 0.15:0.15. In the fifth experimental example (EX5), the content ratio of the first n-type host NH1 and the second n-type host NH2 was set to 0.1:0.2.

[0107] Figure 4 is a graph showing the threshold voltage when the ratio of the first and second n-type hosts in the light-emitting layer is changed in a light-emitting device according to an embodiment of the present specification. Figure 5 is a graph showing the efficiency when the ratio of the first and second n-type hosts in the light-emitting layer is changed in a light-emitting device according to an embodiment of the present specification. Figure 6 is a graph showing the lifetime when the ratio of the first and second n-type hosts in the light-emitting layer is changed in a light-emitting device according to an embodiment of the present specification.

[0108] From the experiments in Table 2 and Figures 4 to 6, the element characteristics were examined by changing the content of the p-type host material and the first and second n-type host materials in the light-emitting layer, and the capacitance-voltage characteristics of the light-emitting device were evaluated by the experiments in Table 3.

Table 2

[0109] In the experiment, the change in the threshold voltage (ΔVth), the change in the driving voltage (ΔV), the efficiency, the C-V characteristics, and the efficiency were measured at a luminance of 600 nit of the light-emitting device in an environment of 25°C, and the lifetime was measured at a luminance of 600 nit of the light-emitting device in an accelerated environment of 35°C. The lifetime was measured as the time until the luminance reached 95% of the initial luminance.

[0110] In Table 1, the changes in threshold voltage, driving voltage, efficiency, and lifetime were compared and evaluated based on the case where the second n-type host NH2 with high electron mobility was used alone.

[0111] As shown in FIG. 4 and Table 1, the threshold voltage of the light-emitting device tends to increase as the content of the second n-type host NH2 increases, and the threshold voltage tends to decrease as the content of the first n-type host NH1 increases.

[0112] And it can be confirmed that the driving voltage is lower in the first experimental example (EX1) using the first n-type host NH1 as the n-type host, and the third to fifth experimental examples (EX3, EX4, EX5) compared to the second experimental example (EX2) using only the single second n-type host NH2 as the n-type host.

[0113] Also, as shown in FIG. 5 and Table 1, it is shown that the second to fifth experimental examples (EX2, EX3, EX4, EX5) containing the second n-type host NH2 commonly ensure a similar efficiency of 99% or more.

[0114] As shown in FIG. 6 and Table 1, the lifetime is the lowest in the second experimental example (EX2) using only the single second n-type host NH2 as the n-type host, and it can be confirmed that there is a lifetime increase of 163% or more in the first experimental example (EX1) using the first n-type host NH1 as the n-type host and the third to fifth experimental examples (EX3, EX4, EX5).

[0115] That is, it can be seen that the characteristics of the device are more excellent for the second n-type host NH2 as a single n-type host, but there is a limit to the lifetime of the material, and the single first n-type host NH1 has the characteristic of long lifetime but the efficiency decreases. When the first and second n-type hosts NH1 and NH2 are used together, particularly advantageous points for the lifetime can be confirmed.

[0116] Hereinafter, using the light-emitting devices of the first to fifth experimental examples (EX1 to EX5), in the experiments of Table 3, the p-type host material of the light-emitting layer and the contents of the first and second n-type host materials are changed to examine the C-V characteristics and the initial luminance value.

[0117] FIG. 7 is a graph showing J-V curves when the ratio of the first and second n-type hosts of the light-emitting element according to an embodiment of the present specification is changed. FIG. 8 is a graph showing C-V curves when the ratio of the first and second n-type hosts of the light-emitting element according to an embodiment of the present specification is changed. FIG. 9 is a graph showing the capacitance threshold voltage when the ratio of the first and second n-type hosts in the light-emitting layer of the light-emitting element according to an embodiment of the present specification is changed. FIG. 10 is a graph showing the luminance characteristics when the ratio of the first and second n-type hosts of the light-emitting element according to an embodiment of the present specification is changed.

Table 3

[0118] In the experiments in Table 3, for the first to fifth experimental examples (EX1 to EX5), the capacitance threshold voltage (CV Vth) and the maximum capacitance of the light-emitting element were evaluated as capacitance-voltage (C-V) characteristics, and the luminance of the initial frame was compared with the luminance of the sixth frame for evaluation (ΔY: FFR / SFR).

[0119] The variability of the light-emitting element can be reduced by changes such as voltage or temperature only when the maximum capacitance value of the light-emitting element decreases and the capacitance threshold voltage (CV Vth) is large.

[0120] In the C-V graph of FIG. 8, the voltage at which the curve occurs is the capacitance threshold voltage, and the second experimental example (EX2) shows an excellent capacitance threshold voltage.

[0121] Also, as shown in Table 3, in the first to fifth experimental examples (EX1 to EX5), when the content of the second n-type host NH2 is increased, the maximum capacitance of the light-emitting element tends to decrease.

[0122] Referring to FIG. 10 and Table 3, in the first to fifth experimental examples (EX1 to EX5), when evaluating by comparing the luminance of the initial frame with that of the sixth frame, it is found that when only the first n-type host NH1 is used, the initial luminance is very low, and when including a part of the second n-type host NH2, it is found that it has an initial luminance of 65% or more.

[0123] Also, referring to FIG. 8, it can be seen that the capacitance of the second experimental example (EX2) changes at a high voltage. Also, as shown in FIG. 10, the initial luminance of the second experimental example (EX2) is relatively excellent. On the other hand, as shown in FIGS. 8 and 10, in the first experimental example (EX1), the capacitance changes at a low voltage and the initial luminance decreases relatively significantly.

[0124] That is, from the experiments in FIGS. 8 to 10 and Table 3, in the second experimental example (EX2) using a single second n-type host NH2, the C-V characteristics and luminance (ΔY) characteristics are excellent. However, as examined in the experiments of Table 2 and FIG. 6, it can be confirmed that the second experimental example (EX2) has a large limit of life and a driving voltage higher than that of other experimental examples. And the first experimental example (EX1) using a single first n-type host NH1 has a good life but very low efficiency and initial luminance, and since the maximum capacitance of the light-emitting element is large, it is difficult to satisfy the required efficiency of the light-emitting element.

[0125] The light-emitting element of this specification aims to obtain a structure that can not only ensure element characteristics including the driving voltage, efficiency, and life in the green light-emitting layer, but also stabilize the C-V characteristics in terms of reliability to ensure a capacitance threshold voltage for ensuring a certain luminance under temperature changes or the initial frame state at a certain level or higher, and lower the maximum capacitance of the light-emitting element. By changing the host of the light-emitting layer. In the first to fifth experimental examples described above, when the content of the p-type host is made larger than the total content of the first and second n-type hosts, and the content ratio of the first n-type host and the second n-type host is 1:1 (0.15:0.15), it is found that all characteristics are the most excellent.

[0126] In the following experiment, as a representative example of two hosts in the light-emitting layer, compared with the second experimental example, the characteristics of the device were evaluated by changing the content of the p-type host in a structure using three hosts in the light emission.

Table 4

[0127] In the second experimental example (EX2), only the second n-type host NH2 was used as a single n-type host. In the sixth experimental example (EX6), the fourth experimental example (EX4), and the seventh experimental example (EX7), the content ratios of the first and second n-type hosts NH1 and NH2 were made the same, and the content of the p-type host PH was gradually increased for evaluation. That is, in the sixth experimental example (EX6), the content ratio of the p-type host, the first n-type host, and the second n-type host was 0.6:0.2:0.2. In the fourth experimental example (EX4), the content ratio of the p-type host, the first n-type host, and the second n-type host was 0.7:0.15:0.15. In the seventh experimental example (EX7), the content ratio of the p-type host, the first n-type host, and the second n-type host was 0.8:0.1:0.1.

[0128] Looking at the results in Table 4, it can be seen that in the fourth experimental example (EX4), the change in the threshold voltage, the change in the driving voltage, the efficiency, and the lifetime of the light-emitting device are all excellent.

[0129] And it can be confirmed that when the content of the p-type host PH is less than or equal to three times or more than eight times the content of each of the first and second n-type hosts NH1 and NH2, the effects of efficiency and lifetime begin to decline. That is, in the examples of this specification, it can be confirmed that compared with the content of each of the first and second n-type hosts NH1 and NH2, it is advantageous in terms of efficiency, driving voltage, and long lifetime that the content of the p-type host is greater than three times and less than eight times. In this case, the first n-type host and the second n-type host in the light-emitting layer can be in the same amount.

[0130] FIG. 11 is a cross-sectional view showing a light-emitting device according to an embodiment of this specification.

[0131] As shown in FIG. 11, a light-emitting device according to an embodiment of the present specification can include an intermediate layer OS having two or more stacks S1, S2, ··· that emit light of the same color between the first and second electrodes 110 and 200. Each stack S1, S2, ··· can be divided into charge generation layers CGL1, CGL2 ···.

[0132] Each stack 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.

[0133] The light-emitting layer of each stack includes a p-type host PH with excellent hole mobility and the first and second n-type hosts NH1 and NH2 and dopant GD having different physical properties described above.

[0134] The LUMO energy level of the first n-type host NH1 is higher than the LUMO energy level of the second n-type host NH2, and the hole mobility of the first n-type host NH1 is larger than the hole mobility of the second n-type host NH2 and smaller than the hole mobility of the p-type host PH, so the first and second n-type hosts NH1 and NH2 are different from each other.

[0135] The electron mobility of the second n-type host NH2 can be larger than the electron mobility of the first n-type host NH1.

[0136] The first n-type host NH1 has a high LUMO energy level and is distinguished from the second n-type host NH2 in that it has high hole mobility and electron mobility.

[0137] Also, the LUMO energy level of the first n-type host NH1 can be lower than the LUMO energy level of the dopant GD.

[0138] When a plurality of stacks are provided, the luminous efficiency of the light-emitting layer can be further improved. Along with the decrease in the threshold voltage, the improvement in luminous efficiency, and the effect of long life of the light-emitting element described in the third to fifth experimental examples (EX3, EX4, EX5), there is an effect that the capacitance threshold voltage can be increased to improve the safety of the element.

[0139] FIG. 12 is a cross-sectional view showing a light-emitting display device according to an embodiment of the present specification.

[0140] As shown in FIG. 12, the light-emitting display device according to an embodiment of the present specification can apply the above-described light-emitting element to at least one of a plurality of sub-pixels SP1, SP2, SP3, and SP4.

[0141] As shown in FIG. 12, the light-emitting display device according to an embodiment of the present specification can 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.

[0142] 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 can include a buffer layer 101 on the substrate 100 and can be located on the buffer layer 101.

[0143] A gate insulating film 103 is provided between the gate electrode 102 and the semiconductor layer 104.

[0144] The semiconductor layer 104 can be, for example, any one of an oxide semiconductor, amorphous silicon, and polycrystalline silicon, or can 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.

[0145] A gate electrode 102 is provided on the gate insulating film 103, and an interlayer insulating film 105 can be further provided between the gate electrode 102 and the source electrode 106a / drain electrode 106b.

[0146] Also, the drain electrode 106b of the thin film transistor TFT can be connected to the first electrode 110 in a contact hole CT region provided in the first and second protective films 107 and 108.

[0147] The first protective film 107 is provided to primarily protect the thin film transistor TFT, and color filters 109R, 109G, and 109B can be provided on the first protective film 107.

[0148] A second protective film 108 is provided on the first protective film 107 including the color filters 109R, 109G, and 109B.

[0149] When including a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel (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-pixel. In some cases, in each sub-pixel, the light-emitting layer can be divided and patterned. Some of the sub-pixels having different emission colors may be provided with a hole transport auxiliary layer, and the rest may not be provided. In sub-pixels having different emission colors, a 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-pixel than in the green sub-pixel or the blue sub-pixel.

[0150] A second protective film 108 is formed below 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.

[0151] 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.

[0152] The light emitting element ED is formed on the thin film transistor array substrate 1000 including the bank 119 that defines the 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 the 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 the 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 nth common layer (CML2) or the charge generation layer (CGL) can 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.

[0153] Therefore, when the green light emitting layer of the green sub-pixel uses two types of n-type hosts and one type of p-type host, in the light emitting layer of the sub-pixels of other colors, a single p-type host or a single n-type host can be used, or one or both of a plurality of p-type hosts and a plurality of n-type hosts can be used. Since the energy band gap of the dopant of the light emitting color of the host used by the light emitting layer of other colors is different from that of the green dopant, at least one of the hosts included in the green light emitting layer can be different for optimal light emission.

[0154] The first electrode 110 is divided and split for each sub-pixel, and the remaining layers except the first electrode 110 of the light-emitting element ED can be provided integrally for the entire display area without division by sub-pixel.

[0155] Either one of the first electrode 110 or the second electrode 200 can be connected to the thin-film transistor TFT.

[0156] 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.

[0157] On the second electrode 200, a sealing layer or a sealing substrate (not shown) can be further provided so as to protect the light-emitting element ED.

[0158] Although the illustrated example is shown in consideration of top emission, the embodiments of this specification are not limited thereto.

[0159] The light-emitting element according to the embodiments of this specification includes a first n-type host having a high LUMO energy level, a high hole mobility, and a high electron mobility as an n-type host that controls electron transport in the light-emitting layer, and a second n-type host having a LUMO energy level relatively lower than that of the first n-type host, a low hole mobility, and a high electron mobility. And the host includes a p-type host that supplies abundant holes so as to act together with the n-type host and the dopant.

[0160] The first n-type host having a high LUMO energy level, a high hole mobility, and a high electron mobility controls the electron and hole speeds supplied to the green dopant together, maintains the balance at the time of recombination of holes and electrons abundantly supplied by the high content of the p-type host, maintains the hole-electron balance in the light-emitting layer, increases the charge trapping efficiency in the light emission, and can maintain or increase the electrostatic capacitance threshold voltage of the light-emitting layer in the light-emitting element.

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, and including: The first light-emitting layer includes a p-type host, a first n-type host, a second n-type host, and a dopant; The LUMO energy level of the first n-type host is higher than the LUMO energy level of the second n-type host; The hole mobility of the first n-type host is greater than the hole mobility of the second n-type host and less than the hole mobility of the p-type host, a light-emitting device.

2. The light-emitting device according to claim 1, wherein the electron mobility of the second n-type host is greater than the electron mobility of the first n-type host.

3. The light-emitting device according to claim 1, wherein the LUMO energy level of the first n-type host is lower than the LUMO energy level of the dopant.

4. In the first light-emitting layer, the electron mobility gradually increases in the order of the p-type host, the first n-type host, the dopant, and the second n-type host, the light-emitting device according to claim 1.

5. The LUMO energy level of the p-type host is the highest among the components included in the light-emitting layer; The LUMO energy level of the electron blocking layer is higher than the LUMO energy level of the p-type host, the light-emitting device according to claim 1.

6. The light-emitting device according to claim 1, wherein the energy band gap of the first n-type host is greater than the energy band gap of the second n-type host.

7. The light-emitting device according to claim 1, wherein the triplet energy level of the second n-type host is greater than the triplet energy level of the first n-type host.

8. The light-emitting device according to claim 1, wherein the HOMO energy level of the p-type host is lower than the HOMO energy level of the dopant and has a difference of 0.1 eV to 0.6 eV with respect to the dopant.

9. The light-emitting device according to claim 1, wherein the total content of the first n-type host and the second n-type host is less than the content of the p-type host.

10. The light-emitting device according to claim 9, wherein the content of the p-type host is 3 to 8 times the content of each of the first n-type host and the second n-type host.

11. In the first light-emitting layer, the first n-type host and the second n-type host are in the same amount, the light-emitting device according to claim 10.

12. The light-emitting element according to claim 1, wherein the dopant has a light emission peak at a wavelength of 500 nm to 580 nm.

13. 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.

14. including one or more stacks between at least one of between the first electrode and the electron blocking layer and between the electron transport layer and the second electrode, 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 of the same hue as the first light-emitting layer.

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

16. 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 element according to any one of claims 1 to 15, which is connected to the thin film transistor in at least one of the plurality of sub-pixels.

Images