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

Abstract

To provide a light-emitting element that improves color purity and brightness, reduces the driving voltage of a material, and improves the life by changing the configuration of a green stack.SOLUTION: A light-emitting device according to the present invention includes a first electrode and a second electrode facing each other, and a light-emitting unit in which a p-type charge generation layer, a hole transport layer, and a green light-emitting layer are sequentially stacked, and the green light-emitting layer may contain a triazine-based compound as a host and a phosphorescent dopant.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a light emitting device, and more particularly to a light emitting device and a light emitting display device using the same, which can improve white efficiency by evenly improving exciton efficiency for each color in a phosphorescent stack by changing materials of a hole transport layer and a green light emitting layer of a phosphorescent stack adjacent to a blue stack, thereby ensuring safety over time and improving life span. [Background technology]

[0002] Recently, light emitting display devices that do not require a separate light source and have light emitting elements within a display panel for compactness and clear color display are being considered as competitive applications.

[0003] Meanwhile, since light emitting elements used in light emitting displays are required to have higher efficiency in order to display image quality, a method of laminating a plurality of stacks is preferred.

[0004] In addition, in response to the demand for higher image quality of display devices, high color purity is required. Therefore, research is being conducted into improving the color purity and brightness of all colors by providing a single light emitting layer for each stack.

[0005] However, if a single-color light-emitting layer is provided for each stack in order to improve color purity, the number of stacks increases, which increases the driving voltage. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been devised to solve the above-mentioned problems, and aims to provide a light-emitting element and a light-emitting display device using the same that can ensure high efficiency and improved lifespan without increasing the driving voltage, even in a structure having multiple stacks including a single light-emitting layer for each stack to improve color purity. [Means for solving the problem]

[0007] In the light emitting device of the present invention, the composition of the green stack can be modified to improve color purity and brightness, while reducing the material driving voltage and improving the life span. According to an embodiment of the present invention, the light emitting device includes a first electrode and a second electrode facing each other, and a light emitting unit in which a p-type charge generation layer, a hole transport layer, and a green light emitting layer are sequentially stacked, and the green light emitting layer may include a triazine-based compound as a host and a phosphorescent dopant.

[0008] In addition, an organic light emitting display device according to an embodiment of the present invention may include a substrate including a plurality of sub-pixels, thin film transistors provided in each of the sub-pixels on the substrate, and the light emitting element connected to the thin film transistors. Effect of the Invention

[0009] The light emitting element of the present invention and the light emitting display device using the same have the following effects.

[0010] In a light emitting device having a single light emitting layer in each stack to improve brightness, the efficiency can be improved without a separate control layer around the green phosphorescent light emitting layer by changing the physical properties of the hole transport layer and the green phosphorescent light emitting layer adjacent to the green stack having a single green phosphorescent light emitting layer.

[0011] In addition, the brightness of white is improved by improving the efficiency of the green stack, which has the highest ratio in realizing white. In addition, when the brightness of white is improved under the condition of applying the same voltage, the voltage required to realize a certain brightness is reduced, so the turn-on voltage is reduced over time, thereby improving the life span. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a light emitting device according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a layer-by-layer energy band diagram of a green stack according to an embodiment of a light-emitting device of the present invention. [Diagram 3] FIG. 4 is a cross-sectional view showing a light emitting device used in the first and second experimental example groups. [Figure 4] 13 is a graph showing the emission spectrum of the first experimental example group. [Diagram 5] 13 is a graph showing the emission spectrum of the second experimental example group. [Figure 6a] FIG. 13 is a diagram showing the configuration of phosphorescent stacks in third and fourth experimental examples. [Figure 6b] FIG. 13 is a diagram showing the configuration of phosphorescent stacks in third and fourth experimental examples. [Figure 7] 10 is a cross-sectional view showing light-emitting devices according to fifth to seventh experimental examples of the present invention. [Figure 8] 8 is a graph showing white light emission spectra of the light emitting devices according to the fifth to seventh experimental examples of FIG. [Figure 9] 1 is a cross-sectional view showing a light emitting device according to another embodiment of the present invention. [Figure 10] 1 is a cross-sectional view showing an embodiment of a light-emitting display device using a light-emitting element according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The same reference numerals throughout the specification refer to substantially the same components. In the following description, if it is determined that a detailed description of a technology or configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. In addition, the names of components used in the following description have been selected in consideration of easy specification writing and may differ from the names of parts of an actual product.

[0014] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for illustrating various embodiments of the present invention are illustrative only, and the present invention is not limited to the matters shown in the drawings. The same drawing symbols refer to the same elements throughout this specification. In addition, in describing the present invention, if it is determined that a detailed description of related prior art may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. When using "including," "having," "being," etc. referred to in this specification, other parts may be added unless "only" is used. When an element is expressed in the singular, it includes the plural unless otherwise explicitly stated.

[0015] In interpreting the components included in the various embodiments of the present invention, unless otherwise expressly stated, they are to be interpreted as including a margin of error.

[0016] In describing various embodiments of the present invention, when describing a positional relationship between two parts, for example, by using "on," "at the top of," "at the bottom of," "beside," etc., one or more other parts may be located between the two parts, unless "immediately" or "directly" is used.

[0017] In describing various embodiments of the present invention, when describing a temporal relationship, for example, when describing a temporal precedence relationship using terms such as "after," "following," "next to," "before," etc., non-consecutive cases may be included unless "immediately" or "directly" is used.

[0018] In describing various embodiments of the present invention, terms such as "first", "second", etc. may be used to describe various components, but such terms are only used to distinguish between identical or similar components. Therefore, in this specification, a component modified with "first" may be the same as a component modified with "second" within the technical spirit of the present invention, unless otherwise specified.

[0019] The respective features of the various embodiments of the present invention may be partially or fully combined or combined with each other, various technical interlocking and operation are possible, and the various embodiments may be implemented independently of each other or may be implemented together in a linked relationship.

[0020] In this specification, "doped" means that a material having different physical properties (different physical properties are, for example, N-type and P-type, organic and inorganic materials) from the material that occupies the majority of the weight ratio of a certain layer is added at a weight ratio of less than 30%. In other words, a "doped" layer means a layer in which the host material and the dopant material of a certain layer can be separated in consideration of the weight ratio. And, "undoped" means all cases other than those corresponding to "doped". For example, if a certain layer is composed of a single material or is composed of a mixture of materials having the same or similar properties, the layer is included in the "undoped" layer. For example, if at least one of the materials constituting a certain layer is P-type and all of the materials constituting the layer are not N-type, the layer is included in the "undoped" layer. For example, if at least one of the materials constituting a certain layer is an organic material and all of the materials constituting the layer are not inorganic materials, the layer is included in the "undoped" layer. For example, if all the materials constituting a layer are organic materials and at least one of the materials constituting the layer is N-type and at least one of the materials is P-type, the layer is considered to be "doped" if the weight ratio of the N-type material is less than 30 wt % or the weight ratio of the P-type material is less than 30 wt %.

[0021] Hereinafter, a light emitting device and a light emitting display device including the same according to the present invention will be described with reference to the accompanying drawings.

[0022] FIG. 1 is a cross-sectional view showing a light emitting device according to an embodiment of the present invention.

[0023] As shown in FIG. 1, the light emitting element according to one embodiment of the present invention includes a first electrode 110 and a second electrode 200 facing each other, and a red stack RS, a first blue stack BS1, a green stack GS, and a second blue stack BS2 are sequentially provided between the first electrode 110 and the second electrode 200, and charge generation layers CGL1, CGL2, and CGL3 are provided between each stack RS, BS1, GS, and BS2.

[0024] Here, the light emitting device according to FIG. 1 has a single light emitting layer for each of the stacks RS, BS1, GS, and BS2 so that each color has high efficiency in terms of color purity when expressing white light.

[0025] Here, each of the stacks RS, BS1, GS, and BS2 can include a color-emitting layer, a hole transport layer below the color-emitting layer (the side closer to the first electrode 110), and an electron transport layer above the color-emitting layer (the side closer to the second electrode 200).

[0026] The first electrode 110 and the second electrode 200 may be referred to as an anode and a cathode, respectively. In some cases, the anode may be provided on the upper side and the cathode may be provided on the lower side, as opposed to what is shown in FIG. At least one of the first electrode 110 and the second electrode 200 includes a transparent electrode, and the other includes a reflective electrode, and can determine the traveling direction of light.

[0027] In some cases, one of the first electrode 110 and the second electrode 200 may be made of a transparent electrode and the other may be made of a thin reflective / transmissive electrode, and by maintaining the strong cavity characteristics of the first and second electrodes 110, 200, the light emitted from each light-emitting layer may be emitted within a narrow half-width range, thereby improving the light efficiency.

[0028] 1 shows a single red stack RS and a single green stack GS, and a double blue stack BS1 and BS2. This is to compensate for the fact that the efficiency of the blue stack including a fluorescent emitting layer is relatively lower than that of the red stack RS and the green stack GS including a phosphorescent emitting layer. In some cases, the number of blue stacks can be reduced or increased by changing the material of the blue emitting layer.

[0029] Meanwhile, the positions of the red stack RS, the first blue stack BS1, the green stack GS, and the second blue stack BS2 shown in FIG. 1 can be changed as necessary.

[0030] FIG. 2 is a diagram showing an energy band diagram of layers of a green stack according to an embodiment of the light emitting device of the present invention.

[0031] 2, N may be a natural number equal to or greater than 2. Thus, the green stack as the Nth stack may be located second or more stacks from the first electrode 110 and may be among the stacks emitting other colors thereafter.

[0032] Taking Fig. 1 as an example, the green stack GS is provided between the first and second blue stacks BS1 and BS2, and can satisfy the configuration of Fig. 2. The light emitting unit including the green stack (Nth Stack) shown in Fig. 2 can include a p-type charge generation layer (pCGL) 1105, a hole transport layer (HTL) 1210, a green light emitting layer 1220, and an electron transport layer (ETL) 1230, in that order.

[0033] 2 has a hole transport layer 1210 and an electron transport layer 1230 located on both sides of a green light emitting layer 1220, and can confine holes and electrons in the green light emitting layer 1220 as a single phosphorescent light emitting layer without a separate control layer, thereby enabling emission with high external quantum efficiency in the green light emitting layer 1220. This is possible by changing the material of the electron transporting host GEH included in the green light emitting layer 1220 and the electron transport layer 1230.

[0034] In general, materials for hole transport layers used in known phosphorescent stacks and materials known as hosts for phosphorescent emitting layers are provided in a phosphorescent stack, and are designed to allow for exciton distribution to each phosphorescent emitting layer. When used in a green phosphorescent emitting layer, the position of the light emitting region is biased toward the interface with the hole transport layer or electron transport layer, making it difficult to obtain high luminous efficiency in the green phosphorescent emitting layer.

[0035] 2, the p-type charge generation layer 1105 is a layer that generates and supplies holes that are insufficient for the green light emitting layer 1220 because the green stack is not immediately adjacent to the first electrode (or anode). The p-type charge generation layer 1105 contains an amine-based compound as a host PH, and 0.1 wt% to 30 wt% of an organic material made of a fluorene-based compound is contained therein as a p-type dopant PD to promote the generation and transport of holes.

[0036] The LUMO energy level of the p-type dopant PD is almost the same as the HOMO energy level of the host material PH in the p-type charge generation layer 1105. The material of the hole transport layer HTL1210 has a HOMO energy level of approximately −5.8 eV to −5.4 eV, which is lower than the HOMO energy level of the host material PH of the p-type charge generation layer (pCGL) 1105 in order to receive holes from the adjacent p-type charge generation layer (pCGL) 1105.

[0037] Furthermore, the green light-emitting layer 1220 of the green stack in the light-emitting device of the present invention contains an electron-transporting host GEH and a hole-transporting host GHH, as well as a green dopant GD doped into these hosts GEH and GHH at 1 wt % to 30 wt %.

[0038] The hole transporting host GHH has a HOMO energy level of about -6.1 eV to -5.4 eV, and has a HOMO energy level equal to or lower than the HOMO energy level of the adjacent hole transporting layer HTL1210 in order to receive holes from the hole transporting layer HTL1210.

[0039] The electron transporting host GEH receives electrons and effectively transfers them to the green dopant GD, and has an overall lower energy band gap than the hole transporting host GHH. Therefore, the HOMO energy level of the electron transporting host GEH is approximately -6.8 eV to -5.6 eV.

[0040] In addition, the green dopant GD preferably has a HOMO energy level higher than that of the hole-transporting host GHH in order to receive holes from the hole-transporting host GHH. The green dopant GD has an emission peak at a wavelength of 510 nm to 550 nm and may be a metal complex compound such as an iridium complex compound.

[0041] In the light emitting device of the present invention, the green light emitting layer 1220 has a single structure without being in contact with light emitting layers of other colors, and has maximum light emitting efficiency. For this purpose, the green light emitting layer 1220 is in contact with the hole transport layer 1210 on one side and with the electron transport layer 1230 on the other side.

[0042] In addition, the other side of the electron transport layer 1230 that is not in contact with the green light emitting layer 1220 may be in contact with an n-type charge generation layer (nCGL) or an electron injection layer (EIL in FIG. 7) of a charge generation layer (see CGL in FIG. 1) between the next stack (N+1)th Stack. The n-type charge generation layer (nCGL) may be an organic layer doped with a metal, and the electron injection layer may be an inorganic or organic-inorganic compound having a metal compound such as LiF or Liq (lithium quinolate).

[0043] In addition, the electron transport layer 1230 may be in contact with a metal-doped organic layer or an inorganic layer having a metal compound on the other side not in contact with the green light emitting layer. At least one of the p-type charge generation layer and the n-type charge generation layer may be adjacent to a blue stack (BS1 or BS2 in FIG. 1) including a blue light emitting layer, and the blue light emitting layer may include a blue dopant having an emission peak at a wavelength of 420 nm to 480 nm.

[0044] In the light emitting device of the present invention, the electron transporting host GEH of the green light emitting layer 1220 may be composed of a triazine compound represented by the following Chemical Formula 1.

[0045] [ka]

[0046] Here, Re includes at least one of a dibenzofuran group, a dibenzothiophene group, a triphenyl group, a triphenylene group, a carbazole group, a benzocarbazole group, an indenocarbazole group, a biscarbazole group, a fluorene group, and a phenyl-carbazole group, and L can be a single bond or at least one of a phenyl group, a phenylene group, a biphenyl group, a biphenylene group, a dibenzofuran group, a dibenzofurylene group, a dibenzothiophene group, and a dibenzothienylene group. In one embodiment, L is a biphenyl group or a phenyl group, and Re is an indenocarbazole (e.g., 7,7-dimethyl-5,7-dihydroindeno[2,1-b]carbazole). In one embodiment, L is a single bond and Re can be two phenyl-carbazoles.

[0047] In one embodiment, L is a dibenzofuran or dibenzothiophene group and Re is a phenyl-carbazole or triphenylene group.

[0048] Examples of the compound of the above-mentioned Chemical Formula 1 include TRZ-01 to TRZ-27.

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] [ka]

[0057] [ka]

[0058] The hole transport layer 1210 in contact with the green light emitting layer GEML 1220 is a biscarbazole-based compound shown below, and can smoothly transport holes without accumulation at the interface even without a separate control layer between the green light emitting layer 1220.

[0059] The biscarbazole-based compound forming the hole transport layer 1210 may include a second material represented by Chemical Formula 2.

[0060] [ka]

[0061] Here, Ra to Rd are each independently selected from hydrogen, deuterium, halogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 9 carbon atoms, a carbazole group, a dibenzofuran group, a dibenzothiophene group, a trialkylsilyl group, and a triarylsilyl group. m and p are independently selected from integers of 0 to 4. n and o are independently selected from integers of 0 to 3. R1 to R 10are each independently selected from hydrogen, deuterium, halogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 8 carbon atoms, a carbazole group, a phenylcarbazole group, a dibenzofuran group, and a dibenzothiophene group, or two or more of R1 to R 10 may form a fused aryl group together with the phenyl group to which it is bonded. The aryl group having 6 to 18 carbon atoms is preferably a phenyl group, a biphenyl group, or a triphenylene group. The fused aryl group is preferably a naphthyl group, a phenanthrene group, or a triphenylene group, and the heteroaryl group having 5 to 9 carbon atoms preferably contains one or more heteroatoms selected from oxygen, sulfur, and nitrogen in the aryl ring structure.

[0062] In one embodiment, m, n, o, and p are 0. In one embodiment, four of R1 through R5 are independent of one another, and one of R1 through R5 is a phenyl group, a biphenyl group, a dibenzofuran group, a dibenzothiophene group, a carbazole group, or a phenyl-carbazole group. 10 At least one of R6 to R 10 Up to four of the groups may be independently selected from hydrogen, phenyl, triphenylene, phenanthrene, anthracene, naphthyl, or together with the phenyl group to which they are attached, R6 to R 10 Two or more of may form a fused aryl group, which is preferably a naphthyl group, a phenanthrene group, or a triphenylene group.

[0063] Moreover, examples of such biscarbazole compounds include the following materials BCA-01 to BCA-44.

[0064] [ka]

[0065] [ka]

[0066]

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[0067]

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[0068]

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[0069]

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[0070]

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[0071]

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[0072]

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[0073]

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[0074]

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[0075]

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[0076]

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[0077] [ka]

[0078] [ka]

[0079] [ka]

[0080] Hereinafter, in a light-emitting device structure having a single stack of green phosphorescent-emitting layers, the significance of each material will be described by changing the material of the electron-transporting host in the adjacent green phosphorescent-emitting layer and the material of the hole-transporting host in the hole-transporting layer.

[0081] For the first experimental example group (Ex1-1 to Ex1-52) and the second experimental example group (Ex2-1 to Ex2-71), light emitting devices as shown in FIG. 3 were formed and comparative experiments were carried out.

[0082] 3 is a cross-sectional view showing the light emitting devices used in the first and second experimental example groups. As shown in FIG. 3, the light emitting devices according to the first experimental example group (Ex1-1 to Ex1-52) are formed in the following order.

[0083] First, the first electrode 10 made of ITO is formed.

[0084] Next, DNTPD and MgF2 are co-evaporated in a weight ratio of 1:1 to form a hole injection layer (HIL) 11 to a thickness of 7.5 nm.

[0085] Next, an amine-based material (HM-01 to HM-25) is evaporated to a thickness of 15 nm to form a hole transport layer (HTL) 12.

[0086] Next, CBP is used as a hole-transporting host, and a triazine-based compound is mixed as an electron-transporting host GEH in a weight ratio of 1:1, and this is doped with Ir(ppy)3 at 15 wt % to form a green light-emitting layer (GEML) 13 with a thickness of 40 nm.

[0087] A TPBI component is then evaporated to 25 nm to form the electron transport layer (ETL) 14 .

[0088] Next, LiF components are evaporated to 2 nm to form an electron injection layer (EIL) 15, and then a second electrode 20 is formed from aluminum (Al).

[0089] In the experiments of the first experimental example group (Ex1-1 to Ex1-52), an amine-based material was used as the compound material for the hole transport layer 12, and a triazine-based compound of Chemical Formula 1 was used as the electron transport host for the green phosphorescent-emitting layer.

[0090] The amine-based compounds used in the first experimental group (Ex1-1 to Ex1-52) may be HM-01 to HM-25 below.

[0091] [ka]

[0092] [ka]

[0093] [ka]

[0094] [ka]

[0095] [ka]

[0096] [ka]

[0097] The driving voltage, efficiency, and external quantum efficiency of the first experimental example group (Ex1-1 to Ex1-52) are as shown in Tables 1-1 and 1-2 below.

[0098] [Table 1-1]

[0099] [Table 1-2]

[0100] That is, in the first experimental example group (Ex1-1 to Ex1-52), it was confirmed that when an amine-based compound was used as the hole transport layer 12 of FIG. 3, the external quantum efficiency had a variability of 16% to 19.5%. It was confirmed that such a characteristic occurs regardless of the material of the electron transport host of the green light-emitting layer. In the second experimental example group (Ex2-1 to Ex2-71), the device structure of FIG. 3 was used, the material of the hole transport layer 12 was changed to a biscarbazole-based compound, and the material of the electron transport host of the green light-emitting layer 13 was a triazine-based compound. The results are shown in Tables 2-1 and 2-2.

[0101] [Table 2-1]

[0102] [Table 2-2]

[0103] Looking at Tables 2-1 and 2-2, it can be seen that the second experimental example group (Ex2-1 to Ex2-71), unlike the first experimental example group (Ex1-1 to Ex1-52), has an external quantum efficiency (EQE) that has leveled out upward to 22% or more, and it can be confirmed that the efficiency has been greatly improved compared to the first experimental example group (Ex1-1 to Ex1-52) in which the hole transport layer is amine-based.

[0104] FIG. 4 is a graph showing the emission spectrum of the first experimental example group, and FIG. 5 is a graph showing the emission spectrum of the second experimental example group.

[0105] It can be seen that the green emission intensity of the emission spectrum of the second experimental example group in FIG. 5 is increased by 25% to 30% or more compared to FIG. 4. It can also be seen that when a triazine-based compound is used as an electron transport host of the material of the green single phosphorescent emission layer and a biscarbazole-based compound is used as a hole transport host of the hole transport layer, the green emission efficiency is also improved at a high rate.

[0106] The following describes the relationship between the driving voltage, efficiency, and lifetime in the structure of the third experimental example (Ex3), in which the external quantum efficiency was improved by changing the structure, and the structure of the fourth experimental example (Ex4), which has the hole transport layer and green light-emitting layer structure of the present invention. The third experimental example (Ex3) and the fourth experimental example (Ex4) include green light-emitting elements that use a green light-emitting layer as the light-emitting layer.

[0107] [Table 3]

[0108] 6a and 6b are diagrams illustrating the configuration of the green phosphorescent stack GS of the third and fourth experimental examples.

[0109] As shown in FIG. 6a, the green phosphorescent stack GS of the third experimental example has an electron blocking layer EBL between the green light-emitting layer GEML and the hole transport layer HTL to prevent electrons from moving from the green light-emitting layer GEML to the hole transport layer HTL, and a hole blocking layer HBL between the green light-emitting layer GEML and the electron transport layer ETL to prevent holes from moving from the green light-emitting layer GEML to the electron transport layer ETL.

[0110] Here, an amine-based material was used as the hole transport layer HTL in the third experimental example (Ex3), and a known electron transport host material used together with a phosphorescent dopant such as TPBi was used as the electron transport host in the green light-emitting layer GEML.

[0111] In the third experimental example (Ex3), the current density was set to 100 mA / cm 2 When this is done, if the external quantum efficiency (EQE) is to be 23.5%, a drive voltage of 7.6 V is required, as shown in Table 3.

[0112] 6b, the green phosphorescent stack GS of the fourth experimental example (Ex4) is different from the third experimental example (Ex3) described above in that the green (phosphorescent) emitting layer (GEML) 1220 is in contact with the hole transport layer HTL 1210 and the electron transport layer (ETL) 1230, and does not include a control layer related to the transport of holes and electrons other than a separate transport layer. However, the hole transport layer HTL 1210 of the fourth experimental example (Ex4) uses an amine-based compound, and the electron transport host of the green emitting layer uses a triazine-based compound, which are the materials used in the first experimental example group in Table 1.

[0113] In this case, in the fourth experimental example (Ex4), the use of layers in the green phosphorescent stack GS was reduced, and it was confirmed that the driving voltage was reduced to 4.5 V, a 41% reduction compared to the third experimental example, as shown in Table 3. This is because the driving voltage was reduced by reducing the number of interfaces in the green phosphorescent stack GS.

[0114] Also, compared to the third experimental example, the lifespan is at 111%, confirming an improvement of 11%.

[0115] Meanwhile, as described in Table 2, it can be seen that, compared to the first experimental example, when a biscarbazole-based compound is used as the material of the hole transport layer in contact with the green light-emitting layer 1220, electrons and holes are restricted, and the recombination rate of electrons and holes inside the green light-emitting layer 1220 is increased, thereby increasing the efficiency. From this, it can be seen that the light-emitting element of the present invention can obtain the effects of lowering the driving voltage and improving the lifetime at the same time as increasing the efficiency by using a biscarbazole-based compound as the material of the hole transport layer in a green phosphorescent stack including at least a single green light-emitting layer and using a triazine-based compound as the electron transport host of the green light-emitting layer in contact with the hole transport layer.

[0116] Hereinafter, an example of a light emitting device that is implemented in the four-stack structure of FIG. 1 including the above-mentioned green phosphorescent stack structure will be described.

[0117] FIG. 7 is a cross-sectional view showing light-emitting devices according to fifth to seventh experimental examples of the present invention.

[0118] As shown in FIG. 7, the inner stack OS between the first electrode 110 and the second electrode 200 of the light-emitting element OLED of the present invention is formed by sequentially forming a red stack RS, a first charge generation layer CGL1, a first blue stack BS1, a second charge generation layer CGL2, a green stack GS, a third charge generation layer CGL3, and a second blue stack BS2 on the first electrode 110.

[0119] Here, the red stack RS and the green stack GS consist of phosphorescent stacks, and the first and second blue stacks BS1, BS2 consist of fluorescent stacks.

[0120] The red stack RS comprises, on the first electrode 110, a hole injection layer (HTL) 121, a first hole transport layer (HTL1) 122, a red light emitting layer 123, and a first electron transport layer (ETL1) 124, in that order.

[0121] The first to third charge generation layers CGL1, CGL2, and CGL3 each include an n-type charge generation layer nCGL1, nCGL2, and nCGL3, and a p-type charge generation layer pCGL1, pCGL2, and pCGL3, respectively.

[0122] The first blue stack BS1 is formed on the first charge generation layer CGL1 and includes a second hole transport layer (HTL2) 131, a first electron blocking layer (EBL1) 132, a first blue light-emitting layer (BEML1) 133, and a second electron transport layer (ETL2) .

[0123] The green stack GS also includes a third hole transport layer 141 , a green light emitting layer 142 , and a third electron transport layer 143 .

[0124] The second blue stack BS2 is formed on the third charge generation layer CGL3 and includes a fourth hole transport layer (HTL4) 151, a second electron blocking layer (EBL2) 152, a second blue light emitting layer (BEML2) 153, and a fourth electron transport layer (ETL4) 154.

[0125] Here, the first and second blue stacks BS1 and BS2, unlike the stacks of the other colors, include first and second electron blocking layers 132 and 152, respectively, which are made of a material having a high mobility to increase efficiency corresponding to the adjacent phosphorescent stack and to prevent electrons from moving from the electron transport layer 134 and 154 to the hole transport layer 131 and 151. In some cases, the material of the hole transport layer 131 and 151 can be changed and omitted.

[0126] The fifth to seventh experimental examples were performed with different materials in the third hole transport layer 141 and the green light emitting layer 142 of the green stack GS, and the electron transport host and the remaining layers were performed under the same conditions.

[0127] [Table 4]

[0128] FIG. 8 is a graph showing white light emission spectra of the light emitting devices according to the fifth to seventh experimental examples of FIG.

[0129] In the fifth experimental example (Ex5) and the sixth experimental example (Ex6), like Ex1-15 in the first experimental example group, the third hole transport layer 141 was made of HM-15, and the electron transport host GEH of the green light-emitting layer 142 was made of TRZ-20. However, in the fifth experimental example (Ex5), an electron blocking layer EBL and a hole blocking layer HBL were further formed in contact with the green light-emitting layer 142 for the purpose of improving efficiency.

[0130] In the seventh experimental example (Ex7), the third hole transport layer 141 was made of BCA-03, and the electron transport host GEH of the green light-emitting layer 142 was made of TRZ-20.

[0131] The fifth experimental example (Ex5) has an improved efficiency, especially for green light, as shown in FIG. 8, but the driving voltage is more than 4V higher than that of the sixth experimental example (Ex6) as shown in Table 4. In other words, it is a structure in which the driving voltage increases, and it is expected that the power consumption will be large when driven for a long time, which will affect the lifespan.

[0132] In the sixth experimental example (Ex6), the driving voltage was improved, and in the realization of white, the efficiency of green was 10.7 Cd / A lower than that of the fifth experimental example (Ex5) when the proportion of green was high. Therefore, when realizing an element that emits white light, it is expected that a compensation means other than the light-emitting element will be necessary to achieve the desired white brightness.

[0133] In contrast, in the case of the seventh experimental example (Ex7) of the light emitting device of the present invention, the efficiency is improved to a level higher than that of the fifth experimental example (Ex5), and compared to the sixth experimental example (Ex6) having the same layer structure, the driving voltage is at the same level, but the green efficiency is improved to 11.5 Cd / A or more, and it is expected that when embodied in a white light emitting device, the effect of improving efficiency can be obtained even in a state where the driving voltage is reduced. This means that it can be operated at a low driving voltage during long-term driving, and it can be understood that it has a direct impact on improving the lifespan.

[0134] Other examples of the light-emitting device of the present invention will be described below.

[0135] FIG. 9 is a cross-sectional view showing a light emitting device according to another embodiment of the present invention.

[0136] 9, the red and blue stack RBS of the internal stack OS between the first electrode 310 and the second electrode 400 of the light emitting device according to another embodiment of the present invention has a first blue light emitting layer (BEML) 324 in contact with the red light emitting layer (REAML) 323, a first electron transport layer (ETL1) 325 on top of the first blue light emitting layer (BEML) 324, a first hole transport layer (HTL1) 322 provided under the red light emitting layer (REAML) 323, and further includes a blue light emitting layer in contact with the red light emitting layer 323, which is a phosphorescent light emitting layer, in response to a request for improving the color temperature.

[0137] In this case, the first and second blue stacks BS1, BS2 each have a hole transport layer (HTL2, HTL4) 331, 351, an electron blocking layer (EBL1, EBL2) 332, 352, a blue light-emitting layer (BEML2, BEML3) 333, 353, and an electron transport layer (ETL2, ETL4) 334, 354, and the second blue stack BS2 in contact with the cathode 400 further comprises an electron injection layer (ETL) 360.

[0138] 7, the green stack GS has a simple structure of a hole transport layer (HTL3) 341, a green light emitting layer (GEML) 342, and an electron transport layer (ETL3) 343. As described above, the green stack GS has a simple structure and can reduce the driving voltage, and by changing the electron transporting host material in the hole transport layer 341 and the green light emitting layer 342, it can have the effects of improving efficiency, reducing the driving voltage, and improving lifespan at the same time.

[0139] An example in which the light-emitting element of the present invention is used in a light-emitting display device will be described below.

[0140] FIG. 10 is a cross-sectional view showing an embodiment of a light-emitting display device using a light-emitting element of the present invention.

[0141] As shown in FIG. 10, the display device of the present invention includes a substrate 100 having a plurality of sub-pixels R_SP, G_SP, B_SP, and W_SP emitting red light R, green light G, blue light B, and white light W, respectively, a light emitting element OLED commonly provided on the substrate 100, a thin film transistor TFT provided in each of the sub-pixels and connected to the first electrode 110 of the light emitting element OLED, and color filter layers 109R, 109G, and 109B provided under the first electrode 110 of at least one of the sub-pixels.

[0142] The illustrated example describes an example including a white sub-pixel W_SP, but is not limited thereto, and a structure including only red, green, and blue sub-pixels R_SP, G_SP, and B_SP without the white sub-pixel W_SP may be possible. In some cases, instead of the red, green, and blue sub-pixels, a combination of cyan, magenta, and yellow sub-pixels that can be combined to express white may be used.

[0143] For example, the thin film transistor TFT includes 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. A channel protection layer 105 may be further provided on an upper portion of the semiconductor layer 104 where a channel is located to prevent a direct connection between the source / drain electrodes 106a and 106b and the semiconductor layer 104. A gate insulating film 103 is provided between the gate electrode 102 and the semiconductor layer 104 .

[0144] The semiconductor layer 104 may be made of, for example, any one or a combination of two or more of an oxide semiconductor, amorphous silicon, and polycrystalline silicon. For example, when the semiconductor layer 104 is an oxide semiconductor, the heating temperature required for forming a thin film transistor can be lowered, and the substrate 100 can be used with high flexibility, which is advantageous for application to a flexible display device.

[0145] In addition, the drain electrode 106b of the thin film transistor TFT may be connected to the first electrode 110 in the region of a contact hole CT provided in the first and second passivation films 107 and .

[0146] The first passivation film 107 is provided to primarily protect the thin film transistor TFT, and color filters 109R, 109G, and 109B may be provided thereon.

[0147] When the sub-pixels include a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel, the color filter is divided into first to third color filters 109R, 109G, and 109B and provided in the remaining sub-pixels except for the white sub-pixel W_SP, and transmits white light emitted through the first electrode 110 according to wavelength. A second protective film 108 is formed under the first electrode 110 to cover the first to third color filters 109R, 109G, and 109B. The first electrode 110 may be formed on the surface of the second protective film 108 through a contact hole CT and connected to the thin film transistor TFT.

[0148] Here, the thin film transistor array substrate 1000 includes the substrate 100, the thin film transistor TFT, the color filter layers 109R, 109G, and 109B, and the first and second protective films 107 and .

[0149] The light emitting element OLED is formed on a thin film transistor array substrate 100 including a bank 119 defining a light emitting portion BH. The light emitting element OLED includes, for example, a transparent first electrode 110 and a reflective second electrode 200 facing the transparent first electrode 110, and has a structure including a single green light emitting layer of a green phosphorescent stack between the first electrode 110 and the second electrode 200 as described above. The material of the hole transport layer in contact with the green light emitting layer is a biscarbazole-based compound represented by Chemical Formula 2, and the material of the electron transport host in the green light emitting layer is a triazine-based compound represented by Chemical Formula 1, thereby improving efficiency, reducing the driving voltage, and improving lifespan.

[0150] The light emitting device and the light emitting display device using the same of the present invention form a light emitting device that realizes white light by connecting a fluorescent stack and a phosphorescent stack. Among them, the phosphorescent stack has a higher internal quantum efficiency than the fluorescent stack, and different phosphorescent light emitting layers are adjacently formed to share the use of excitons. The light emitting device and the light emitting display device using the same of the present invention change the material of the red light emitting layer between the hole transport layer and another phosphorescent light emitting layer to prevent loss of excitons generated at the interface with the hole transport layer and to allow excitons to be evenly distributed and generated across the adjacent phosphorescent light emitting layer, thereby adjusting the efficiency of the adjacent phosphorescent light emitting layer to not be biased to one side in order to display white light.

[0151] As a result, by balancing the efficiency between the red light-emitting layer and the adjacent phosphorescent light-emitting layer, the luminance of the phosphorescent light-emitting layer in a white light-emitting device can be increased in a balanced manner, and the efficiency of the light-emitting display device can also be improved. The light emitting device of the present invention includes a first electrode and a second electrode facing each other, and a light emitting unit in which a p-type charge generation layer, a hole transport layer, and a green light emitting layer are sequentially stacked, and the green light emitting layer may include a first material represented by Chemical Formula 1 and a phosphorescent dopant.

[0152] [ka]

[0153] Here, Re includes at least one of a dibenzofuran group, a dibenzothiophene group, a triphenyl group, a triphenylene group, a carbazole group, a benzocarbazole group, an indenocarbazole group, a biscarbazole group, a fluorene group, and a phenylcarbazole group, and L includes at least one of a phenyl group, a phenylene group, a biphenyl group, a biphenylene group, a dibenzofuran group, a dibenzofurylene group, a dibenzothiophene group, and a dibenzothienylene group.

[0154] The hole transport layer may include a second material of Formula 2.

[0155] [ka]

[0156] Here, Ra to Rd are each independently selected from hydrogen, deuterium, halogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 9 carbon atoms, a carbazole group, a dibenzofuran group, a dibenzothiophene group, a trialkylsilyl group, and a triarylsilyl group. m and p are independently selected from integers of 0 to 4. n and o are independently selected from integers of 0 to 3. R1 to R 10 are each independently selected from hydrogen, deuterium, halogen, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, a carbazole group, a phenylcarbazole group, a dibenzofuran group, and a dibenzothiophene group, or two or more of R1 to R 10 may form a fused aryl group together with the phenyl group to which it is attached.

[0157] The phosphorescent dopant may be a metal complex compound having an emission peak at a wavelength of 510 nm to 550 nm.

[0158] The green light-emitting layer may be in contact with an electron transport layer on the other side thereof that is not in contact with the hole transport layer.

[0159] The electron transport layer may be in contact with an electron injection layer or an n-type charge generation layer on the other side not in contact with the green light emitting layer.

[0160] The electron transport layer may be an organic layer doped with a metal or an inorganic layer having a metal compound on the other side not in contact with the green light emitting layer.

[0161] At least one of the p-type charge generation layer and the n-type charge generation layer may be adjacent to a blue stack including a blue light emitting layer, the blue light emitting layer including a blue dopant having an emission peak at a wavelength of 420 nm to 480 nm.

[0162] The p-type charge generation layer may be spaced from the first electrode by 50 nm or more.

[0163] In addition, a light emitting device according to another embodiment of the present invention includes a first electrode and a second electrode facing each other, and a light emitting unit in which a p-type charge generation layer, a hole transport layer, a green light emitting layer, and an electron transport layer are sequentially stacked, wherein the green light emitting layer includes a first material of Formula 1 above and a phosphorescent dopant, and the hole transport layer includes a second material of a biscarbazole-based compound.

[0164] In addition, a light emitting device according to yet another embodiment of the present invention includes a first electrode and a second electrode facing each other, and a red stack, a first blue stack, a green stack, and a second blue stack sequentially provided between the first electrode and the second electrode, the green stack sequentially including a hole transport layer, a green light emitting layer, and an electron transport layer, the green light emitting layer including a first material of Formula 1 above and a phosphorescent dopant, and the hole transport layer including a second material of a biscarbazole-based compound.

[0165] And, an organic light emitting display device according to an embodiment of the present invention may include a substrate including a plurality of sub-pixels, thin film transistors provided in each of the sub-pixels on the substrate, and the above-mentioned light emitting element connected to the thin film transistor.

[0166] On the other hand, the present invention described above is not limited to the above-mentioned embodiments and accompanying drawings, and it will be apparent to those having ordinary skill in the art to which the present invention pertains that various substitutions, modifications and alterations are possible within the scope of the technical idea of ​​the present invention. [Explanation of symbols]

[0167] 100 Substrates 110 1st electrode 1105 p-type charge generation layer 1210 Hole transport layer 1220 Green light-emitting layer 1230 Electron transport layer 200 2nd electrode GS Green Stack GEH Electron-transporting host GHH Hole transporting host GD Green dopant

Claims

1. a first electrode and a second electrode facing each other; a light-emitting unit in which a p-type charge generation layer, a hole transport layer, and a green light-emitting layer are laminated in this order; the green light-emitting layer includes a first material represented by Chemical Formula 1 and a phosphorescent dopant; 【Chemistry 1】 Re comprises at least one of a triphenyl group, a carbazole group, an indenocarbazole group, a biscarbazole group, and a phenyl-carbazole group; L is a single bond or contains at least one of a phenylene group, a biphenylene group, a dibenzofurylene group, and a dibenzothienylene group; The hole transport layer includes a second material represented by Formula 2, 【Chemistry 2】 Ra-Rd are each independently selected from hydrogen; m and p are independently selected from integers from 0 to 4; n and o are independently selected from among integers from 0 to 3; R １ ~R １０ are each independently selected from hydrogen, an unsubstituted aryl group having 6 carbon atoms, a carbazole group substituted with a phenyl group, an unsubstituted carbazole group, an unsubstituted dibenzofuran group, and an unsubstituted dibenzothiophene group, or two or more R １ ~R １０ forms a fused aryl group together with the phenyl group to which it is attached.

2. 2. The light-emitting device according to claim 1, wherein the phosphorescent dopant is a metal complex compound having an emission peak in the wavelength range of 510 nm to 550 nm.

3. The light-emitting device according to claim 1 , wherein the green light-emitting layer is in contact with an electron transport layer on the other side thereof that is not in contact with the hole transport layer.

4. The light-emitting device according to claim 3 , wherein the other side of the electron transport layer, which is not in contact with the green light-emitting layer, is in contact with an electron injection layer or an n-type charge generation layer.

5. The light-emitting device according to claim 3 , wherein a metal-doped organic layer or an inorganic layer having a metal compound is in contact with a side of the electron transport layer that is not in contact with the green light-emitting layer.

6. at least one of the p-type charge generation layer and the n-type charge generation layer is adjacent to a blue stack including a blue light emitting layer; 5. The light-emitting device according to claim 4, wherein the blue light-emitting layer contains a blue dopant having an emission peak in the wavelength range of 420 nm to 480 nm.

7. The light emitting device of claim 1 , wherein the p-type charge generation layer is spaced from the first electrode by 50 nm or more.

8. 2. The light-emitting device of claim 1, wherein the material of Chemical Formula 1 is one of the following compounds TRZ-01 to TRZ-27. 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 【Chemistry 7】 【Chemistry 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】

9. A first electrode and a second electrode opposed to each other, a light-emitting unit in which a p-type charge generation layer, a hole transport layer, and a green light-emitting layer are laminated in this order; the green light-emitting layer includes a first material represented by Chemical Formula 1 and a phosphorescent dopant; 【Chemistry 12】 Re comprises at least one of a triphenyl group, a carbazole group, an indenocarbazole group, a biscarbazole group, and a phenyl-carbazole group; L is a single bond or contains at least one of a phenylene group, a biphenylene group, a dibenzofurylene group, and a dibenzothienylene group; The light-emitting device, wherein the hole transport layer contains one of the following compounds BCA-01 to BCA-44. 【Chemistry 13】 【Chemistry 14】 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 【Chemistry 18】 【Chemistry 19】 【Chemistry 20】 【Chemistry 21】 【Chemical 22】 【Chemistry 23】 【Chemistry 24】 【Chemistry 25】 【Chemistry 26】 【Chemistry 27】 【Chemistry 28】

10. a first electrode and a second electrode facing each other; a light-emitting unit including a p-type charge generating layer, a hole transport layer, a green light-emitting layer, and an electron transport layer stacked in this order; the green light-emitting layer includes a first material represented by Chemical Formula 1 and a phosphorescent dopant; the hole transport layer includes a second material that is a biscarbazole compound; 【Chemical Formula 29】 Re comprises at least one of a triphenyl group, a carbazole group, an indenocarbazole group, a biscarbazole group, and a phenyl-carbazole group; L is a single bond or contains at least one of a phenylene group, a biphenylene group, a dibenzofurylene group, and a dibenzothienylene group; The second material is represented by Formula 2, 【Chemistry 30】 Ra-Rd are each independently selected from hydrogen; m and p are independently selected from integers from 0 to 4; n and o are independently selected from among integers from 0 to 3; R １ ~R １０ each is independently selected from hydrogen, an unsubstituted aryl group having 6 carbon atoms, an unsubstituted carbazole group, a carbazole group substituted with a phenyl group, an unsubstituted dibenzofuran group, and an unsubstituted dibenzothiophene group, or two or more R １ ~R １０ forms a fused aryl group together with the phenyl group to which it is attached.

11. a first electrode and a second electrode facing each other; a red stack, a first blue stack, a green stack, and a second blue stack disposed in sequence between the first electrode and the second electrode; the green stack comprising, in order, a hole transport layer, a green light emitting layer, and an electron transport layer; the green light-emitting layer includes a first material represented by Chemical Formula 1 and a phosphorescent dopant; the hole transport layer includes a second material that is a biscarbazole compound; 【Chemistry 31】 Re comprises at least one of a triphenyl group, a carbazole group, an indenocarbazole group, a biscarbazole group, and a phenyl-carbazole group; L is a single bond or contains at least one of a phenylene group, a biphenylene group, a dibenzofurylene group, and a dibenzothienylene group; The second material is represented by Formula 2, 【Chemistry 32】 Ra-Rd are each independently selected from hydrogen; m and p are independently selected from integers from 0 to 4; n and o are independently selected from among integers from 0 to 3; R １ ~R １０ are each independently selected from hydrogen, an unsubstituted aryl group having 6 carbon atoms, a carbazole group substituted with a phenyl group, an unsubstituted carbazole group, an unsubstituted dibenzofuran group, and an unsubstituted dibenzothiophene group, or two or more R １ ~R １０ forms a fused aryl group together with the phenyl group to which it is attached; Light emitting element.

12. a substrate including a plurality of sub-pixels; A thin film transistor provided in each of the sub-pixels on the substrate; A light-emitting display device comprising the thin film transistor and the light-emitting element according to any one of claims 1 to 11 connected thereto.

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