Light Emitting Device and Light Emitting Display Device Using the Same

Abstract

The light-emitting element of the present invention and the light-emitting display device using the same are provided with a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer adjacent to each other in at least one of a plurality of stacks, and by changing the physical properties of the light-emitting layers, non-luminous loss of excitons distributed to each other's light-emitting layers can be prevented or minimized so that there is no decrease in efficiency of both light-emitting layers and the lifespan can be improved.

Description

Technology Field

[0001] The present invention relates to a light-emitting element and a light-emitting display device using the same, which can improve the efficiency of adjacent light-emitting layers by reducing or preventing the ratio of excitons that are extinguished inside the light-emitting layer in a structure in which a blue light-emitting layer and a light-emitting layer of a different color are in contact. Background Technology

[0002] With the recent entry into the full-scale information age, the field of displays that visually represent electrical information signals has been developing rapidly. In response to this, various display devices with excellent performance characteristics such as thinness, lightness, and low power consumption have been developed and are rapidly replacing existing Cathode Ray Tubes (CRTs).

[0003] Among these, a light-emitting display device that does not require a separate light source and has a light-emitting element within the display panel for compact device design and clear color display is being considered as a competitive application. The problem to be solved

[0004] In a display device that performs display using the self-luminescence principle of a light-emitting element, the light-emitting element provided in each subpixel can display white light by including a plurality of light-emitting layers emitting different colors between two electrodes. However, due to the limitation that the blue light-emitting layer has lower efficiency compared to the other color light-emitting layer and the problem that it receives energy from the other color light-emitting layer but cannot be used for light emission, in a light-emitting element having a blue light-emitting layer adjacent to the other color light-emitting layer, the light-emitting efficiency within the blue light-emitting layer does not increase, and instead, a phenomenon may occur in which internal excitons are not used for light emission and are extinguished.

[0005] The light-emitting element and light-emitting display device using the same according to the present invention are intended to solve the aforementioned problems. In a structure in which multiple light-emitting layers are adjacent, the difference in triplet excitation levels between materials between the blue light-emitting layer and the adjacent light-emitting layer is changed, or the physical properties of the blue host that can prevent dexter transition to the blue host are changed to reduce quenched excitons, thereby improving the efficiency of both the blue light-emitting layer and the adjacent light-emitting layer. means of solving the problem

[0006] The light-emitting element of the present invention and the light-emitting display device using the same are provided with a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer adjacent to each other in at least one of a plurality of stacks, and by changing the physical properties of the light-emitting layers, non-luminous loss of excitons distributed to each other's light-emitting layers can be prevented or minimized so that there is no decrease in efficiency of both light-emitting layers and the lifespan can be improved.

[0007] A light-emitting element according to one embodiment of the present invention comprises a first electrode and a second electrode that are spaced apart from each other and facing each other, a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer that are in contact with each other between the first electrode and the second electrode, a first common layer between the first electrode and the non-blue phosphorescent light-emitting layer, and a second common layer between the blue fluorescent light-emitting layer and the second electrode, wherein the non-blue phosphorescent light-emitting layer comprises a first host and a first dopant, and the blue fluorescent light-emitting layer may comprise a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host that transfers energy to the singlet excitation level (S1) of the second dopant and suppresses a dexter energy transfer from the first dopant.

[0008] Additionally, a light-emitting element according to another embodiment of the present invention comprises a first electrode and a second electrode that are spaced apart from each other and facing each other, a plurality of stacks between the first and second electrodes, and a charge generating layer provided between the stacks. One of the stacks has a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer in contact with each other, and at least one of the other stacks has a single light-emitting layer as the light-emitting layer, and the non-blue phosphorescent light-emitting layer includes a first host and a first dopant, and the blue fluorescent light-emitting layer may include a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host having a triplet excitation level between the first dopant and the second dopant.

[0009] A light-emitting element according to another embodiment comprises a first electrode and a second electrode that are spaced apart from each other and facing each other, a plurality of stacks between the first and second electrodes, and a charge generating layer provided between the stacks. In addition, one of the stacks has a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer in contact with each other, and at least one of the other stacks has a single light-emitting layer as the light-emitting layer, and the non-blue phosphorescent light-emitting layer includes a first host and a first dopant, and the blue fluorescent light-emitting layer may include a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host having a core compound and a spacer of 1 nm or more on the outer edge of the core compound.

[0010] In addition, a light-emitting display device according to one embodiment of the present invention may include a substrate having a plurality of subpixels, a driving circuit including at least one transistor provided in each of the subpixels, and a light-emitting element described above connected to the driving circuit in each of the subpixels. Effects of the invention

[0011] The light-emitting element of the present invention and the light-emitting display device using the same have the following effects.

[0012] The present invention provides a light-emitting device having a structure in which light-emitting layers are in contact with a blue fluorescent light-emitting layer and at least one phosphorescent light-emitting layer, wherein the host of the blue fluorescent light-emitting layer has a spacer structure that suppresses dexter energy transfer to the adjacent phosphorescent light-emitting layer, or by configuring the host with a material having a high triplet excitation level in terms of physical properties, particularly a material having a triplet excitation level higher than the triplet excitation level of the dopant of the adjacent phosphorescent light-emitting layer and a triplet excitation level lower than the triplet excitation level of the dopant of the blue fluorescent light-emitting layer, thereby solving the cause of non-emissive exhaustion in the blue fluorescent light-emitting layer and enabling the excitons supplied to the adjacent blue fluorescent light-emitting layer and the phosphorescent light-emitting layer to be used for light emission with maximum efficiency.

[0013] Accordingly, the light-emitting device of the present invention has a stack having a blue fluorescent light-emitting layer and an adjacent phosphorescent light-emitting layer, and considering the light-emitting efficiency of the improved phosphorescent light-emitting layer, the initial exciton distribution is provided with more weight given to the blue fluorescent light-emitting layer, and the efficiency of phosphorescence can be converted to fluorescent blue efficiency, thereby controlling the color temperature of white light emitted when white is realized, or improving the efficiency of a desired color, particularly blue.

[0014] Through the present invention, the excitons generated can be converted into light at a rate close to 100%, which can help realize a high-efficiency white light-emitting device. Through the present invention, excess phosphorescent efficiency is converted into fluorescent blue efficiency, allowing for the emission of a white light-emitting device at a desired color temperature, and enabling the control of red, green, and blue efficiencies at a desired ratio. In addition, since a blue fluorescent light-emitting layer is used, there is an advantage in terms of lifespan. Brief explanation of the drawing

[0015] FIG. 1 is a diagram showing a layer structure according to an example of a light-emitting element of the present invention. FIG. 2 is a diagram showing the energy transfer and light emission principles of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer of FIG. 1 in a light-emitting device according to the first embodiment of the present invention. FIGS. 3a to 3c are drawings showing the internal luminescence efficiency of each light-emitting layer according to the exciton ratio of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer in a light-emitting device according to the light-emitting principle of FIG. 2. Figure 4 is a diagram showing the energy transfer and light emission principles of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer of a light-emitting device according to a comparative example. Figure 5 is a diagram showing the internal quantum efficiency of each light-emitting layer according to the exciton ratio of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer in a light-emitting device according to the light-emitting principle of Figure 4. FIG. 6 is a cross-sectional view showing a light-emitting element according to a second embodiment of the present invention. FIG. 7 is a cross-sectional view showing a light-emitting element according to a third embodiment of the present invention. FIG. 8 is a cross-sectional view according to a light-emitting element according to the fourth embodiment of the present invention. FIG. 9 is a diagram showing the energy transfer and light emission principles of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer of FIG. 1 in a light-emitting device according to the fourth embodiment of the present invention. FIG. 10 is a diagram illustrating the principle of suppressing dexter energy transfer from the first dopant of FIG. 9 to the second host. FIGS. 11a to 11c are drawings showing the internal luminescence efficiency of each light-emitting layer according to the exciton ratio of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer in a light-emitting device according to the light-emitting principle of FIG. 9. FIG. 12 is a cross-sectional view showing a light-emitting element according to another embodiment of the present invention. FIG. 13 is a cross-sectional view showing a specific example of FIG. 12. FIG. 14 is a cross-sectional view showing a light-emitting display device of the present invention applying the light-emitting element of FIG. 13. FIG. 15 is a graph showing the white spectrum of a light-emitting element according to the first to fourth experimental examples. Specific details for implementing the invention

[0016] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. Throughout the specification, identical reference numbers denote substantially identical components. In the following description, if it is determined that a detailed description of a technology or configuration related to the present invention could unnecessarily obscure the essence of the invention, such detailed description is omitted. Furthermore, the component names used in the following description have been selected for ease of drafting the specification and may differ from the actual product part names.

[0017] Shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for describing various embodiments of the present invention are exemplary, and therefore the present invention is not limited to the matters depicted in the drawings. Throughout this specification, the same reference numerals refer to the same components. Furthermore, in describing the present invention, if it is determined that a detailed description of related prior art may unnecessarily obscure the essence of the present invention, such detailed description is omitted. Where terms such as "includes," "has," or "is made up" are used in this specification, other parts may be added unless "only" is used. Where a component is expressed in the singular, it includes cases where it is included in the plural unless specifically stated otherwise.

[0018] In interpreting the components included in various embodiments of the present invention, they are interpreted to include an error range even without separate explicit description.

[0019] In describing various embodiments of the present invention, when describing positional relationships, for example, when the positional relationship between two parts is described using expressions such as 'on', 'on the upper part', 'on the lower part', 'next to', etc., unless 'immediately' or 'directly' is used, one or more other parts may be located between the two parts.

[0020] In describing various embodiments of the present invention, when describing temporal relationships, for example, when describing temporal sequence relationships using 'after', 'following', 'next', 'before', etc., cases that are not continuous may be included unless 'immediately' or 'directly' is used.

[0021] In describing various embodiments of the present invention, terms such as 'first~', 'second~', etc. may be used to describe various components, but these terms are used merely to distinguish between identical or similar components. Accordingly, unless otherwise stated, a component modified by 'first~' in this specification may be identical to a component modified by 'second~' within the technical scope of the present invention.

[0022] Each feature within various embodiments of the present invention may be combined or combined with one another, either partially or wholly, and may technically enable various interlocking and operation. Each of the various embodiments may be implemented independently of one another or may be implemented together in an associated relationship.

[0023] In this specification, "doped" means that a material having different physical properties (e.g., N-type and P-type, organic and inorganic materials) is added to a material that constitutes the majority by weight of a layer in an amount of less than 30% by weight. In other words, a "doped" layer refers to a layer in which the host material and the dopant material of a layer can be distinguished by considering their specific gravity by weight. Furthermore, "undoped" refers to all cases other than those corresponding to "doped." For example, if a layer is composed of a single material or is composed of a mixture of materials with identical or similar properties, that layer is included in the "undoped" layer. For example, if at least one of the materials constituting a layer is P-type and not all of the materials constituting the layer are N-type, that layer is included in the "undoped" layer. For example, if at least one of the materials constituting a layer is an organic material and not all of the materials constituting the layer are inorganic materials, that layer is included in the 'undoped' layer. For example, if all of 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 other is P-type, the layer is included in the 'doped' layer if the weight ratio of the N-type material is less than 30% or the weight ratio of the P-type material is less than 30%.

[0024] Hereinafter, the light-emitting element of the present invention and the display device including the same will be described with reference to the drawings.

[0025] FIG. 1 is a diagram showing a layer structure according to an example of a light-emitting element of the present invention. FIG. 2 is a diagram showing the energy transfer and light emission principles of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer of FIG. 1 in a light-emitting element according to a first embodiment of the present invention.

[0026] As shown in FIG. 1, the light-emitting element of the present invention comprises a first electrode (300) and a second electrode (400) that are spaced apart and facing each other, a blue fluorescent light-emitting layer (330) and a non-blue phosphorescent light-emitting layer (320) that are in contact with each other between the first electrode (300) and the second electrode (400), a first common layer (CML1) between the first electrode (300) and the non-blue phosphorescent light-emitting layer (320), and a second common layer (CML2) between the blue fluorescent light-emitting layer (330) and the second electrode (400). One side of the first electrode (300) and the second electrode (400) may be located on the lower side and in contact with a substrate, and the other side may be located on the upper side.

[0027] The first common layer (CML1) may include a hole injection layer (305) and a hole transport layer (310), and has the function of injecting holes from the first electrode (300) and transporting them to the non-blue phosphorescent emitting layer (320). In addition to the hole injection layer (305) and the hole transport layer (310), the first common layer (CML1) may further include an electron blocking layer that prevents electrons from moving from the non-blue phosphorescent emitting layer (320) to the hole transport layer (310), or a hole control layer that controls the speed of movement of holes.

[0028] The second common layer (CML2) may include an electron transport layer (340) and an electron injection layer (350), and has the function of injecting electrons from the second electrode (400) and transporting them to the blue fluorescent emitting layer (330). Additionally, the second common layer (CML2) may further include a hole blocking layer or an electron control layer that controls the speed of electron movement from the second electrode (400) to prevent holes from escaping from the blue fluorescent emitting layer (330).

[0029] The first and second common layers (CML1, CML2) are layers provided to enhance the transportability of holes and electrons, because when only the light-emitting layer is provided between the electrodes, the energy barrier received by the light-emitting layer for each electrode is large, which results in a high increase in driving voltage and makes it difficult to properly supply holes and electrons to the light-emitting layer. In addition to the illustrated layers, the first and second common layers (CML1, CML2) may be further provided with additional layers to consider the hole transportability and electron transportability or carrier distribution required by the light-emitting device.

[0030] The light-emitting element illustrated in FIG. 1 has a structure in which a plurality of light-emitting layers are in contact between first and second electrodes (300, 400) facing each other. Depending on the case, it is possible for the first electrode (300) to be located on the lower side and the second electrode (400) to be located on the upper side, or it is possible for the first electrode (300) to be located on the upper side and the second electrode (400) to be located on the lower side.

[0031] Also, “S” in FIG. 1 refers to an internal stack made of organic material between the first electrode (300) and the second electrode (400). The internal stack (S) may be connected to other stacks by a charge generating layer, etc.

[0032] Here, the light-emitting layers (320, 330) in contact with each other emit light in a phosphorescent and fluorescent manner, respectively. In addition, different materials are used for the host and dopant forming the light-emitting layers (320, 330) so that the light-emitting element of the present invention can emit light of different colors with a single element.

[0033] In tandem devices requiring high color purity and high efficiency, blue high efficiency is required. The light-emitting device of the present invention is designed to maintain high phosphorescence efficiency in the non-blue phosphorescent light-emitting layer (320) by joining a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer, and to maximize quantum efficiency in each light-emitting layer without reducing blue light-emitting efficiency due to energy transfer from the blue fluorescent light-emitting layer (330) to the adjacent non-blue phosphorescent light-emitting layer (320), and to prevent or reduce non-luminescence loss.

[0034] The non-blue phosphorescent light-emitting layer (320) may be, for example, a red phosphorescent light-emitting layer, a yellow-green phosphorescent light-emitting layer, or a green phosphorescent light-emitting layer. When the non-blue phosphorescent light-emitting layer (320) is a red phosphorescent light-emitting layer, the light emitted may have an emission peak at a wavelength of 600 nm to 650 nm, when the light emitted may be a green phosphorescent light-emitting layer, the light emitted may have an emission peak at a wavelength of 510 nm to 575 nm, and when the light emitted may be a yellow-green phosphorescent light-emitting layer, the light emitted may have an emission peak at a wavelength of 540 nm to 610 nm.

[0035] The non-blue phosphorescent emitting layer (320) comprises a first host (h1) and a first dopant (d1) capable of emitting phosphorescent light with a wavelength longer than blue. The first host (h1) can be selected from a group of materials capable of transferring energy to the first dopant (d1) so that excitons formed by the recombination of holes and electrons supplied to the non-blue phosphorescent emitting layer (320) can act at the triplet excitation level (T1) of the first dopant (d1) and be used for light emission. The first dopant (d1) may use a metal complex with a metal core such as iridium (Ir), platinum (Pt), or beryllium (Be).

[0036] Meanwhile, the triplet excitation level (T1) described in this specification means that a triplet (triplet exciton) has an excited state at the corresponding energy level, and the singlet excitation level (S1) means that a singlet (singlet exciton) has an excited state at the corresponding energy level. Phosphorescent dopants emit phosphorescent light as the triplet drops energy to the ground state, and fluorescent dopants emit fluorescent light as the singlet excitation level drops energy to the ground state.

[0037] The blue fluorescent emitting layer (330) comprises a second host (h2) and a second dopant (d2) capable of emitting blue fluorescent light. The blue light emitted by the blue fluorescent emitting layer (330) may have an emission peak at a wavelength of 430 nm to 480 nm. In order to suppress the non-luminous extinction of energy dexter-transferred from an adjacent non-blue phosphorescent emitting layer (320) in the blue emitting layer (330), the second host (h2) is used as a material in which its triplet excitation level is between the triplet excitation level of the first dopant (d1) of the non-blue phosphorescent emitting layer (320) and the triplet excitation level of the second dopant (d2), as shown in FIG. 2. Additionally, the second dopant (d2) has a triplet excitation level higher than that of the second host (h2), and has the characteristic of having a small difference (ΔEst) between the singlet excitation level and the triplet excitation level. To this end, the second dopant (d2) may be a boron-based dopant. Examples of boron-based dopants include materials of chemical formulas 1 to 9. The presented examples are merely examples, and among boron-based compounds, if blue light emission is possible and the level is higher than the triplet excitation level of the second host (h2), it may be changed to another material.

[0038] [Chemical Formula 1]

[0039]

[0040] [Chemical Formula 2]

[0041]

[0042] [Chemical Formula 3]

[0043]

[0044] [Chemical Formula 4]

[0045]

[0046] [Chemical Formula 5]

[0047]

[0048] [Chemical Formula 6]

[0049]

[0050] [Chemical Formula 7]

[0051]

[0052] [Chemical Formula 8]

[0053]

[0054] [Chemical Formula 9]

[0055]

[0056] As shown in FIG. 2, the triplet excitation level of the second host (h2) is between the first dopant (d1) and the second dopant (d2), and in this case, the triplet excitation level of the second host (h2) may be between 2.1 eV and 2.4 eV. This is to reduce the ratio of excitons that are consumed as non-luminous within the blue fluorescent emitting layer (330) when a dexter energy transition occurs at the triplet excitation level between the non-blue phosphorescent emitting layer (320) and the blue fluorescent emitting layer (330). The non-blue phosphorescent emitting layer (320) is designed for phosphorescent emission, so that triplet excitons at the triplet excitation level of the first dopant (d1) emit phosphorescent light as their energy drops to the ground state.

[0057] If the triplet excitation level of the first dopant (d1) is higher than the triplet excitation level of the second host (h2) or the second dopant (d2) of the adjacent blue fluorescent emitting layer (330), a dexter energy transfer occurs to the blue fluorescent emitting layer (330), and excitons are transferred from the non-blue phosphorescent emitting layer (320) to the blue fluorescent emitting layer, but are not utilized for fluorescent emission due to the low triplet excitation level of the material forming the blue fluorescent emitting layer, and are released as thermal energy at the triplet excitation level of each material and are consumed as non-luminous energy.

[0058] A light-emitting element according to the first embodiment of the present invention prevents a dexter energy transition from a high triplet energy level to a low triplet energy level between the non-blue phosphorescent light-emitting layer (320) and the blue fluorescent light-emitting layer (330) by making the triplet excitation level of the second host (h2) or the second dopant (d2) of the blue fluorescent light-emitting layer (330) higher than that of the first dopant (d1) of the non-blue phosphorescent light-emitting layer (320) due to the energy difference. Through this, when the blue fluorescent light-emitting layer receives energy transferred via a dexter energy transition, it is possible to prevent or reduce excitons that are consumed as non-luminous energy at the triplet excitation level of the second host. And, the blue fluorescent light-emitting layer (330) emits fluorescent light as a singlet exciton falls from a singlet excitation level to a ground state in a triplet-to-singlet ratio that occurs internally in a 3:1 ratio, and additionally, two triplets in the second host (h2) interact by TTF (triplet-triplet fusion) so that singlet excitons fall from an energy singlet excitation level (S1) of the second dopant (d2) to a ground state and emit additional fluorescent light, thereby improving the luminescence efficiency of the blue fluorescent light-emitting layer (330).

[0059] There may be an exciton transfer, such as a first dexter energy transition (DET1) between the triplet energy levels of the second host (h2) and the second dexter energy transition (DET2) from the triplet energy levels of the second host (h2) to the triplet energy levels of the non-blue phosphorescent emitting layer (320), but in this case, the exciton transferred to the non-blue phosphorescent emitting layer (320) can be fully utilized for phosphorescent emission at the triplet excitation level of the first dopant (d1), thereby maximizing internal quantum efficiency.

[0060] The light-emitting element according to the first embodiment of the present invention may include, as an example of the second host (h2), a compound having a triplet excitation level (T1) between the first dopant (d1) and the second dopant (d2), and may include a component of Formula 10 as a terminal group of the compound. In addition, the second host (h2) may include at least one of carbazole, fluorene, triazine, and quinazoline in addition to the terminal group of Formula 10.

[0061] [Chemical Formula 10]

[0062]

[0063] (X is any one of hydrogen, nitrogen, and boron.

[0064] R1 and R2 may independently be selected from the group consisting of a substituted or unsubstituted aryl group having 6 to 24 carbon atoms, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted condensed aryl group having 10 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 2 to 24 carbon atoms, a substituted or unsubstituted alkyl group having 1 to 24 carbon atoms, a substituted or unsubstituted heteroalkyl group having 1 to 24 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 24 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 24 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 24 carbon atoms, a substituted or unsubstituted alkylsilyl group having 1 to 24 carbon atoms, a substituted or unsubstituted arylsilyl group having 6 to 24 carbon atoms, a cyano group, a halogen group, deuterium, and hydrogen, and R1 and R2 may independently It can form condensation rings with neighboring substituents.

[0065] Also, as examples of a second host, Chemical Formula 11 and Chemical Formula 12 can be cited.

[0066] [Chemical Formula 11]

[0067]

[0068] [Chemical Formula 12]

[0069]

[0070] In the light-emitting element according to the first embodiment of the present invention, the example of the above-described formulas 11 and 12 presented as the second host (h2) is an example, and may be changed to another material insofar as it has a triplet excitation level between the first dopant (d1) and the second dopant (d2) and has a function of assisting fluorescent light emission by excitation in the second dopant (d2).

[0071] Meanwhile, in the light-emitting device of the present invention, a non-blue phosphorescent light-emitting layer (320) and a blue fluorescent light-emitting layer (330) are in contact, and excitons formed by the recombination of holes and electrons that move to the non-blue phosphorescent light-emitting layer (320) and the blue fluorescent light-emitting layer (330) by the current generated when voltage is applied to the first and second electrodes (300, 400) on both sides are distributed to both light-emitting layers (320, 330) to cause light emission. Therefore, compared to a structure in which a single light-emitting layer is used as the light-emitting layer within a stack or between two electrodes facing each other, light emission must be performed using excitons distributed to two light-emitting layers (320, 330), so increasing the efficiency of each light-emitting layer is of great significance.

[0072] When two non-blue phosphorescent light-emitting layers (320) and a blue fluorescent light-emitting layer (330) are in contact, the thickness of each light-emitting layer is adjusted, or the content of the first and second dopants (d1, d2) inside each light-emitting layer (320, 330) is adjusted, so that the distribution of excitons acting on each light-emitting layer (320, 330) can be varied.

[0073] Below, we examine the internal quantum efficiency in which excitons are used for light emission according to the exciton content distributed in the non-blue phosphorescent light-emitting layer (320) and the blue fluorescent light-emitting layer (330).

[0074] FIGS. 3a to 3c are drawings showing the internal luminescence efficiency of each light-emitting layer according to the exciton ratio of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer in a light-emitting device according to the light-emitting principle of FIG. 2.

[0075] As shown in FIG. 3a, when the exciton distribution ratio of the non-blue phosphorescent emitting layer (320) and the blue fluorescent emitting layer (330) is set to 50% and 50% by controlling the current driving, the thickness ratio of the non-blue phosphorescent emitting layer (320) and the blue fluorescent emitting layer (330), and the content of the first and second dopants (d1, d2), the blue fluorescent emitting layer (330) has an internal quantum efficiency of 12.5% ​​corresponding to 50%*1 / 4, with the singlets in the singlet excitation level (S1) functioning for blue fluorescence at a ratio of triplets and singlets generated in a 3:1 ratio.

[0076] On the other hand, the non-blue phosphorescent emitting layer (320) allows the supplied excitons to fully function for phosphorescent emission, and at the same time, the triplet in the blue fluorescent emitting layer (330) is transferred from the second dopant (d2) to the second host (h2) via a first dexter energy transfer (DET1), and then transferred from the second host (h2) to the triplet excitation level (T1) of the non-blue phosphorescent emitting layer (320) via a second dexter energy transfer (DET2), so that 50% of the excitons supplied to the non-blue phosphorescent emitting layer (320) and 37.5% (50%*3 / 4) of the triplet transferred via dexter energy from the blue fluorescent emitting layer (330) can contribute to phosphorescent emission together. That is, the non-blue phosphorescent light-emitting layer (320) receives a triplet with a long relaxation time as a dexter energy transfer from the blue fluorescent light-emitting layer (330), has an internal quantum efficiency of 87.5% (50%+37.5%), and is capable of phosphorescent light emission of the color emitted from the first dopant (d1).

[0077] In this case, the light-emitting element according to the first embodiment of the present invention functions with an efficiency of 87.5% in the non-blue phosphorescent light-emitting layer (320) and 12.5% ​​in the blue fluorescent light-emitting layer (330) without excitons being consumed as non-luminous, thereby enabling the internal quantum efficiency to be 100% and contributing to light emission.

[0078] As shown in FIG. 3b, by increasing the thickness of the blue fluorescent emitting layer (330) compared to the non-blue phosphorescent emitting layer (320) compared to FIG. 3a, increasing the content of the second dopant (d2) of the blue fluorescent emitting layer (330) compared to FIG. 3a, or by concentrating the excitons more in the blue fluorescent emitting layer (330), the exciton ratio of the non-blue phosphorescent emitting layer (320) and the blue fluorescent emitting layer (330) is 20% and 80%, respectively. Then, the blue fluorescent emitting layer (330) has an internal quantum efficiency of 20% corresponding to 80%*1 / 4, with the singlets in the singlet excitation level (S1) functioning for blue fluorescence in a ratio of triplets and singlets generated in a 3:1 ratio, thereby increasing the internal quantum efficiency in the blue fluorescent emitting layer (330) and further improving the efficiency of the blue light within the light-emitting device.

[0079] In this case, the non-blue phosphorescent emitting layer (320) is capable of phosphorescent emission by a triplet transferred via Dexter energy transfer (DET1, DET2) from the second dopant (d2) and the second host (h2) of the blue fluorescent emitting layer (330) together with 20% of the supplied excitons, and has an internal quantum efficiency corresponding to 80% (20%+80%*3 / 4).

[0080] As shown in FIG. 3c, conversely to FIG. 3b, if the thickness of the non-blue phosphorescent emitting layer (320) is increased more than that of the blue fluorescent emitting layer (330), or if the content of the first dopant (d1) of the non-blue phosphorescent emitting layer (320) is increased compared to FIG. 3a, or if the exciton concentration is greater in the non-blue phosphorescent emitting layer (320), then the exciton ratio of the non-blue phosphorescent emitting layer (320) and the blue fluorescent emitting layer (330) is 80% and 20%, respectively, the blue fluorescent emitting layer (330) has an internal quantum efficiency of 5% corresponding to 20%*1 / 4, where the singlets in the singlet excitation level (S1) function for blue fluorescence with a ratio of triplets and singlets generated in a 3:1 ratio. And, in this case, the non-blue phosphorescent emitting layer (320) is capable of phosphorescent emission by a triplet transferred via Dexter energy transfer (DET1, DET2) from the second dopant (d2) and the second host (h2) of the blue fluorescent emitting layer (330) together with 80% of the supplied excitons, and has an internal quantum efficiency corresponding to 95% (80%+20%*3 / 4).

[0081] FIGS. 3a to 3c are distinguished by controlling the initial charge ratio of the non-blue phosphorescent emitting layer (320) and the blue fluorescent emitting layer (330). In all cases, among the excitons distributed in the initial state divided by the charge ratio, the triplet that does not function to emit light in the blue fluorescent emitting layer (330) is not consumed as a non-emissive substance in the blue fluorescent emitting layer (330), but is transferred to the adjacent non-blue phosphorescent emitting layer (320) as shown in Table 1 and can function to emit phosphorescent light, thereby maximizing the efficiency of excitons in a structure where the emitting layers are adjacent. In addition, if the light-emitting element has an additional stack in addition to the stack (S) consisting of a first common layer (CML1), a non-blue phosphorescent light-emitting layer (320), a blue fluorescent light-emitting layer (330), and a second common layer (CML2) at the first and second electrodes (300, 400), the initial exciton ratio of the blue fluorescent light-emitting layer (330) can be increased as shown in FIG. 3b or the initial exciton ratio of the non-blue phosphorescent light-emitting layer (320) can be increased as shown in FIG. 3c by considering the color range of light emitted from the final light-emitting element in combination with the light-emitting color of the other stack.

[0082] division Fig. 3a Fig. 3b Fig. 3c Initial exciton ratio (320:330) 50%:50% 20%:80% 80%:20% Internal quantum efficiency IQE IQE IQE non-blue phosphorescent light-emitting layer (320) 87.5% 80% 95% blue fluorescent light-emitting layer (330) 12.5% 20% 5% Total efficiency of the light-emitting layer 100% 100% 100%

[0083] In the first embodiment described above, the triplet excitation level of the second dopant is 2.4 eV or higher.

[0084] The light-emitting element according to the first embodiment of the present invention described above utilizes a fluorescent blue dopant having a high triplet energy level relative to the phosphorescent dopant and a fluorescent blue host. In this case, through a dexter energy transition, the triplet exciton at the triplet energy level of the fluorescent dopant is transferred to the triplet energy level of the fluorescent host. This triplet exciton is then transferred again to the triplet energy level of the phosphorescent dopant of an adjacent phosphorescent red light-emitting layer through a dexter energy transition and can contribute to red light emission.

[0085] Below, we examine a light-emitting device according to a comparative example that corresponds to a case where dexter energy is transferred from a non-blue phosphorescent light-emitting layer to a blue fluorescent light-emitting layer, contrary to the light-emitting device according to the first embodiment of the present invention.

[0086] Figure 4 is a diagram showing the energy transfer and light emission principles of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer of a light-emitting device according to a comparative example, and Figure 5 is a diagram showing the internal quantum efficiency of each light-emitting layer according to the exciton ratio of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer in a light-emitting device according to the light emission principle of Figure 4.

[0087] As shown in FIG. 4, the light-emitting device according to the comparative example has the layer structure of FIG. 1, wherein the composition of the light-emitting layer is such that a non-blue phosphorescent light-emitting layer (32) containing a phosphorescent host (ph) and a phosphorescent dopant (pd) and a blue fluorescent light-emitting layer (33) containing a blue host (bh) and a blue dopant (bd) are in contact. This represents a case where the blue host (bh) and the blue dopant (bd) of the blue fluorescent light-emitting layer (33) have a triplet excitation level lower than that of the phosphorescent dopant (pd) of the non-blue phosphorescent light-emitting layer (32).

[0088] In this case, the light-emitting element according to the comparative example uses an anthracene-based host and a pyrene-based dopant, which are used in the blue light-emitting layer of a single blue light-emitting element, for the material of the blue fluorescent light-emitting layer (33).

[0089] As shown in FIG. 4, in the light-emitting device according to the comparative example, both the anthracene-based host and the pyrene-based dopant have triplet excitation levels lower than the triplet excitation level of the non-blue phosphorescent light-emitting layer. Therefore, in the light-emitting device according to the comparative example, dexter energy is transferred from the phosphorescent dopant (pd) of the non-blue phosphorescent light-emitting layer to the blue host (bh), and when the energy transferred from the blue dopant to the triplet state of the blue host falls to the ground state, it is consumed as heat emission and thus non-radiatively consumed. Consequently, among the excitons supplied to the light-emitting layers, the excitons transferred to the triplet state of the host dopant do not contribute to light emission, which causes a reduction in internal quantum efficiency.

[0090] The non-blue phosphorescent light-emitting layer (32) of the light-emitting element according to the comparative example used the first host and the first dopant of the non-blue phosphorescent light-emitting layer described in FIGS. 1 and 2.

[0091] As shown in FIG. 5, when the initial exciton ratio of the light-emitting element according to the comparative example is set to 50% and 50% for the non-blue phosphorescent light-emitting layer (32) and the blue fluorescent light-emitting layer (33), respectively, and when the dexter energy transfer in the non-blue phosphorescent light-emitting layer (32) occurs with half of the supplied excitons, phosphorescence is generated from the remaining half of the excitons, and the internal quantum efficiency used in phosphorescent light emission is 25%, which is equivalent to 50%*1 / 2.

[0092] Then, energy is transferred to the triplet level of the blue host of the blue fluorescent emitting layer (33) by dexter energy transfer by the exciton component corresponding to the remaining 25% from the non-blue phosphorescent emitting layer (32). Thus, the blue fluorescent emitting layer (33) generates 12.5% ​​of fluorescence by the singlet component corresponding to 1 / 4 of the 50% of the supplied exciton due to the 1:3 generation ratio difference between the internal singlet and triplet in the blue dopant, and some energy is transferred to the singlet by TTF (Triplet-triplet Fusion) action of some of the amount of triplet 62.5 (50*3 / 4+25)% that is dexter energy transferred from the blue dopant and the non-blue phosphorescent dopant to the triplet excitation level of the blue host, and then energy is transferred again to the singlet excitation level of the blue dopant, and this can be used for fluorescence. Here, since the TTF action occurs at approximately 1 / 5 of the host's triplet excitation levels, the additional fluorescence emission efficiency due to the TTF action corresponds to 12.5%, which is 62.5% * 1 / 5.

[0093] Accordingly, as shown in FIG. 5 and Table 2, the light-emitting element according to the comparative example can utilize a ratio of 25% (12.5% ​​+ 12.5%) of the excitons supplied to the light-emitting element in the blue fluorescent light-emitting layer (33) for light emission, and light emission can occur at a ratio of 25% of the excitons supplied to the light-emitting element in the non-blue phosphorescent light-emitting layer (32).

[0094] division Fig. 5 Initial exciton ratio (32:33) Non-blue phosphorescent layer (50%): blue fluorescent layer (50%) Internal quantum efficiency IQE non-blue phosphorescent light-emitting layer (32) 25% blue fluorescent light-emitting layer (33) 25% Total efficiency of the light-emitting layer 50%

[0095] Meanwhile, in the case of the light-emitting device of the comparative example, the proportion of the blue fluorescent light-emitting layer appears higher than that of the light-emitting device of the present invention due to the fact that the internal quantum efficiency of the blue fluorescent light-emitting layer receives a Dexter energy transfer from the adjacent non-blue phosphorescent light-emitting layer (32). However, in the case of the comparative example, the triplet component in the triplet excitation level of the blue host may perform a TTF function at the level of 1 / 5 during initial operation, but as time passes, the triplets react with each other and disappear due to TTA (triplet-triplet annihilation), etc., or the triplet in a non-luminescent state remains in the blue fluorescent light-emitting layer (33) and may function to inhibit fluorescent emission, which may cause a problem of reduced lifespan. In particular, in the light-emitting device of the comparative example, 4 / 5 of the triplets in the triplet energy level of the blue host do not emit light due to the structural triplet energy level difference of the material between the non-blue phosphorescent light-emitting layer (32) and the blue fluorescent light-emitting layer (33), and considering that the internal quantum efficiency is small and the blue fluorescent light-emitting layer is at the level of 1 / 5 of the internal quantum efficiency In this case, it can be understood that in a structure where a non-blue phosphorescent emitting layer and a blue fluorescent emitting layer are adjacent, it is difficult to obtain uniform efficiency in both emitting layers, and if excitons that are not used for light emission remain particularly in the blue fluorescent emitting layer, it becomes a cause of inhibiting light emission.

[0096] On the other hand, the light-emitting device according to the first embodiment of the present invention can prevent the dexter energy transfer from the non-blue phosphorescent light-emitting layer (320) to the blue fluorescent light-emitting layer (330) by making the second host and second dopant of the blue fluorescent light-emitting layer (330) have a higher triplet excitation level compared to the first dopant of the adjacent non-blue phosphorescent light-emitting layer (320) compared to the light-emitting device of the comparative example, thereby preventing the triplet from being consumed as non-luminescent loss at the triplet excitation level of the second host that occurs in the light-emitting device of the comparative example, which can prevent the decrease in internal quantum efficiency. In addition, by utilizing the excitons supplied from the light-emitting device in the non-blue phosphorescent light-emitting layer (320) and the blue fluorescent light-emitting layer (330) which have a structure in full contact, the efficiency of each light-emitting device can be maximized, and the lifespan of the light-emitting device can be improved by reducing or preventing excitons that remain unused for light emission in the light-emitting layers (320, 330).

[0097] FIG. 6 is a cross-sectional view showing a light-emitting element according to a second embodiment of the present invention.

[0098] As shown in FIG. 6, the light-emitting element of the second embodiment of the present invention follows the structure of FIG. 1, but includes a second host (h2) having a high triplet energy level along with a first host (h1) that helps the action of a phosphorescent dopant in the non-blue phosphorescent light-emitting layer (420) within the light-emitting element, thereby facilitating the dexter energy transfer from the blue fluorescent light-emitting layer (330) to the non-blue phosphorescent light-emitting layer (420).

[0099] In this case, the blue fluorescent light-emitting layer (330) includes the second host (h2) and the second dopant (d2) described above in FIGS. 1 and 2.

[0100] In the light-emitting element according to the second embodiment, the first electrode (300), the second electrode (400), the first common layer (CML1), and the second common layer (CML2) are as described above in the first embodiment.

[0101] FIG. 7 is a cross-sectional view showing a light-emitting element according to a third embodiment of the present invention.

[0102] As shown in FIG. 7, the light-emitting element according to the third embodiment of the present invention is a modified example of the second embodiment, following the structure of FIG. 1, wherein the light-emitting layers within the light-emitting element are provided with a first non-blue phosphorescent light-emitting layer (440), a second non-blue phosphorescent light-emitting layer (445), and a blue fluorescent light-emitting layer (330). Here, the first non-blue phosphorescent light-emitting layer (440) has the same configuration as the non-blue phosphorescent light-emitting layer including the first host (h1) and the first dopant (d1) of FIG. 2, the second non-blue phosphorescent light-emitting layer (445) has a configuration including the first and second hosts (h1, h2) and the first dopant (d1), and the blue fluorescent light-emitting layer (330) has a configuration including the second host (h2) and the second dopant (d2) of FIG. 2. That is, a second host (h2) having a high triplet excitation level is further included to make the Dexter energy transition between the first non-blue phosphorescent emitting layer (440) and the blue fluorescent emitting layer (330) to the first non-blue phosphorescent emitting layer (440).

[0103] The first and second non-blue phosphorescent light-emitting layers (440, 445) both contain the first dopant as a light-emitting dopant and emit the same color.

[0104] In both the second and third embodiments, the movement of the triplet with dexter energy transfer is smoothed from the blue fluorescent light-emitting layer to the non-blue phosphorescent light-emitting layer, thereby suppressing the triplet remaining at the triplet excitation level of the blue fluorescent light-emitting layer and being consumed as non-luminous loss, and thus maximizing the efficiency of excitons being used for light emission in the adjacent non-blue phosphorescent light-emitting layer and blue fluorescent light-emitting layer.

[0105] In the first to third embodiments of the present invention, since the dexter energy transfer between the first dopant of the non-blue phosphorescent emitting layer and the first host is possible when orbitals physically overlap, the dopant content in the host is relatively higher than that of the blue fluorescent emitting layer. Since the fluorescent emitting layer allows for energy transfer through the overlap of the absorption energy spectrum of the second host and the emission spectrum of the second dopant, the dopant content is relatively smaller compared to the phosphorescent emitting layer. In each non-blue phosphorescent emitting layer, the content of the first dopant relative to the first host is 20 wt% or less, preferably 10 wt% or less, and more preferably 2 wt% to 5 wt%.

[0106] In addition, in the blue fluorescent emitting layer, the content of the second dopant for the second host is 10 wt% or less, preferably 5 wt% or less, and more preferably 0.1 wt% to 4 wt%. In either case, the dopant content in the blue fluorescent emitting layer is smaller than that in the adjacent non-blue phosphorescent emitting layer and the blue fluorescent emitting layer.

[0107] The light-emitting device of the present invention can convert excitons supplied to a non-blue phosphorescent light-emitting layer and a blue fluorescent light-emitting layer into light at a rate of 100%, making it a high-efficiency light-emitting device. When applied as a single stack within a white light-emitting device, it lowers the driving voltage and enables the emission of multiple colors with high efficiency. That is, the light-emitting device of the present invention can function as a white light-emitting device by connecting it to other stacks in addition to the stack configuration from the first common layer (CML1) to the second common layer (CML2) between the first and second electrodes (300, 400).

[0108] In addition, the light-emitting device of the present invention can increase the efficiency of a non-blue phosphorescent light-emitting layer or a blue fluorescent light-emitting layer by controlling the ratio of excitons in the initial state in adjacent light-emitting layers. In addition, by not leaving the triplet in the blue fluorescent light-emitting layer and transferring it to the phosphorescent light-emitting layer via Dexter energy transfer, the extinction in the blue fluorescent light-emitting layer can be reduced, thereby improving the lifespan of a stack capable of emitting blue light.

[0109] That is, in a light-emitting device having a dual-layer structure in which a long-wavelength phosphorescent layer and a short-wavelength fluorescent layer are adjacent, when a host with a high triplet excitation level and a fluorescent dopant are used, the singlet excitons of the fluorescent dopant in the fluorescent layer emit light as their energy levels drop to the ground state, and the triplet excitons transfer energy to the phosphorescent dopant in the phosphorescent layer through a dexter energy transition, thereby contributing to phosphorescent emission. Therefore, multicolor emission is possible without a decrease in efficiency in terms of overall quantum efficiency.

[0110] Hereinafter, a light-emitting device according to the fourth embodiment of the present invention will be described, which applies a method of suppressing dexter energy transfer from a blue fluorescent light-emitting layer to a non-blue phosphorescent light-emitting layer by a principle different from that of the first to third embodiments described above.

[0111] FIG. 8 is a cross-sectional view of a light-emitting element according to a fourth embodiment of the present invention, and FIG. 9 is a diagram showing the energy transfer and light emission principles of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer of FIG. 8 in the light-emitting element according to the fourth embodiment of the present invention. FIG. 10 is a diagram showing the principle of suppressing dexter energy transfer from the first dopant of FIG. 9 to the second host.

[0112] As shown in FIG. 8, a light-emitting element according to the fourth embodiment of the present invention may include a first electrode (500) and a second electrode (600) that are opposite and spaced apart from each other, and a stack (S) between the first and second electrodes (500, 600) comprising a hole injection layer (505), a hole transport layer (510), a non-blue phosphorescent light-emitting layer (520), a blue fluorescent light-emitting layer (530), an electron transport layer (540), and an electron injection layer (550). In addition to the stack (S), another stack may be further included between the electron transport layer (540) and the electron injection layer (550), or between the hole injection layer (505) and the hole transport layer (510). Furthermore, the additional stack may have a structure of a light-emitting layer different from that of the stack (S) shown in FIG. 8. Additionally, the additional stack may be a plurality of stacks, and at least one of the plurality of stacks may be a stack that includes a blue light-emitting layer as a single light-emitting layer. It may include a plurality of stacks and a charge generation layer provided between the stacks.

[0113] Meanwhile, in the light-emitting element according to the fourth embodiment of the present invention, the non-blue phosphorescent light-emitting layer (520) includes a first dopant (d1) that phosphorescently emits a non-blue wavelength and a first host (h1) that assists in the excitation action of the first dopant (d1). The configuration of the non-blue phosphorescent light-emitting layer (520) of the light-emitting element according to the fourth embodiment of the present invention may be the same as the non-blue phosphorescent light-emitting layer used in the first to third embodiments described above, and a description is omitted.

[0114] A second host (h2) of a blue fluorescent light-emitting layer (530) has a core compound (531a) and a spacer (531b) of 1 nm or more on the outer edge of the core compound (531a).

[0115] Here, even if the core compound (531a) in the second host (h2) of the blue fluorescent light-emitting layer (530) has a triplet excitation level lower than the triplet excitation level of the first dopant (d1) as in FIG. 9, as in FIG. 10, the second host (h2) further provides a spacer (531b) as a structure capable of preventing dexter energy transfer from the adjacent non-blue phosphorescent light-emitting layer (520) to the host in the blue fluorescent light-emitting layer (530) by providing a spacer (531b) on the outer edge of the core compound (531a), thereby preventing dexter energy transfer from the adjacent non-blue phosphorescent light-emitting layer (520) to the host in the blue fluorescent light-emitting layer (530).

[0116] Dexter energy transitions caused by the triplet excitation level difference of a triplet are possible in the adjacent or overlapping orbitals. Dexter energy transitions are possible when the distance between the side receiving the dexter energy transition and the side giving the dexter energy transition is approximately less than 1 nm. The spacer (531b) on the outer edge of the second host (h2) of the present invention is made to be 1 nm or more so that the dexter energy transition is physically suppressed.

[0117] The core compound of the second host (h2) may be a compound containing an anthracene at the center, and the spacer (531b) may be a methyl group, a tertiary-butyl group, a phenyl group, etc. The spacer (531b) may be substituted on the terminal group of the core compound (531a).

[0118] For example, when the core compound of the second host (h2) is the same as Formula 13, the second host (h2) may be any one of Formulas 14 to 16.

[0119] [Chemical Formula 13]

[0120]

[0121] [Chemical Formula 14]

[0122]

[0123] [Chemical Formula 15]

[0124]

[0125] [Chemical Formula 16]

[0126]

[0127] Meanwhile, the second dopant of the blue fluorescent light-emitting layer (530) is a boron-based dopant, and as described in the first to third embodiments, the singlet-triplet excitation level difference (ΔEst) is smaller and the triplet excitation level (T1) is higher than that of the first dopant (d1) of the non-blue phosphorescent light-emitting layer (520).

[0128] The light-emitting device according to the fourth embodiment of the present invention also further comprises a spacer (531b), which is a spatial obstruction structure, so that the second host (h2) structurally suppresses the dexter energy transfer caused by adjacent materials, thereby suppressing the dexter energy transfer from the non-blue phosphorescent dopant to the second host within the blue fluorescent light-emitting layer due to the triplet level difference, and causing the triplet to act in the non-blue phosphorescent light-emitting layer. By doing so, the non-luminous loss caused by the triplet remaining at the triplet excitation level of the second host can be reduced, and the quenching phenomenon caused by the triplet within the blue fluorescent light-emitting layer (530) can be prevented. Accordingly, the light-emitting device according to the fourth embodiment of the present invention can also maximize the efficiency of excitons being used for light emission in the adjacent non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer, and an improved lifespan can be expected.

[0129] FIGS. 11a to 11c are drawings showing the internal luminescence efficiency of each light-emitting layer according to the exciton ratio of the non-blue phosphorescent light-emitting layer and the blue fluorescent light-emitting layer in a light-emitting device according to the light-emitting principle of FIG. 9.

[0130] As shown in FIG. 11a, when the initial exciton distribution ratio of the non-blue phosphorescent emitting layer (520) and the blue fluorescent emitting layer (530) is set to 50% and 50% by controlling the current drive, the thickness ratio of the non-blue phosphorescent emitting layer (520) and the blue fluorescent emitting layer (530), and the content of the first and second dopants (d1, d2), the non-blue phosphorescent emitting layer (520) cannot spatially receive a dexter energy transfer from the second host (h2) of the adjacent blue fluorescent emitting layer (530), so that all internal excitons can contribute to phosphorescent emission. That is, the non-blue phosphorescent emitting layer (520) can utilize all of the supplied 50% of excitons for emission, thus having an internal quantum efficiency of 50%.

[0131] In this case, the blue fluorescent emitting layer (530) is formed with a ratio of triplets to singlets of 3:1, with singlets in the singlet excitation level (S1) functioning for blue fluorescence, and between the triplet excitation levels of the second dopant (d2) and the second host (h2), a dexter energy transition occurs from the second dopant (d2), which has a higher second triplet excitation level, to the second host (h2), which has a lower second triplet excitation level, and transitions to a singlet excitation transition through TTF action between the triplets in the triplet excitation level of the second host (h2), which enables additional fluorescent fluorescence through transition to the singlet excitation level of the second dopant (d2). Approximately, additional fluorescent fluorescence using TTF action is possible at an exciton ratio of 1 / 5. Accordingly, the blue fluorescent emitting layer (530) has an internal quantum efficiency of 20% (50%*1 / 4+37.5%*1 / 5), which is the sum of 12.5% ​​corresponding to 50%*1 / 4 due to a singlet ratio of 1 / 4 and 37.5%*1 / 5 due to additional fluorescent emission caused by dexter energy transfer from the internal second dopant (d2) to the second host (h2) and TTF action.

[0132] That is, as shown in Table 3, in the case of FIG. 11a, the sum of the internal quantum efficiencies of the non-blue phosphorescent emitting layer (520) and the blue fluorescent emitting layer (530) is 70%, and it can be confirmed that there is an improvement in internal quantum efficiency compared to the comparative example in which the Dexter energy transfer cannot be suppressed.

[0133] FIG. 11b shows that the initial exciton ratio is distributed with a current drive ratio of 75% and a non-blue phosphorescent emitting layer (520) and a blue fluorescent emitting layer (530) of 25%. Since the second host (h2) of the adjacent blue fluorescent emitting layer (530) cannot spatially receive a dexter energy transfer in the non-blue phosphorescent emitting layer (520), all internal excitons can contribute to phosphorescent emission. That is, the non-blue phosphorescent emitting layer (520) can utilize all of the supplied 75% of excitons for emission, thus having an internal quantum efficiency of 75%.

[0134] In this case, the blue fluorescent emitting layer (530) is formed with a ratio of triplets to singlets of 3:1, with singlets in the singlet excitation level (S1) functioning for blue fluorescence, and between the triplet excitation levels of the second dopant (d2) and the second host (h2), a dexter energy transition occurs from the second dopant (d2), which has a higher second triplet excitation level, to the second host (h2), which has a lower second triplet excitation level, and transitions to a singlet excitation transition through TTF action between the triplets in the triplet excitation level of the second host (h2), which enables additional fluorescent fluorescence through transition to the singlet excitation level of the second dopant (d2). Approximately, additional fluorescent fluorescence using TTF action is possible at an exciton ratio of 1 / 5. Accordingly, the blue fluorescent emitting layer (530) has an internal quantum efficiency of 10% (25%*1 / 4+18.75%*1 / 5), which is the sum of 6.25% corresponding to 25%*1 / 4 due to a singlet ratio of 1 / 4 and 18.75%*1 / 5 due to additional fluorescent emission caused by dexter energy transfer from the internal second dopant (d2) to the second host (h2) and TTF action.

[0135] That is, as shown in Table 3, in the case of FIG. 11b, the combined value of the internal quantum efficiency of the non-blue phosphorescent emitting layer (520) and the blue fluorescent emitting layer (530) is 85%, and it can be confirmed that there is an improvement in internal quantum efficiency compared to the comparative example in which the Dexter energy transfer cannot be suppressed.

[0136] FIG. 11c shows that the initial exciton ratio is distributed with a current drive ratio of 80% and a non-blue phosphorescent emitting layer (520) and a blue fluorescent emitting layer (530), respectively, so that the non-blue phosphorescent emitting layer (520) cannot spatially receive a dexter energy transfer from the second host (h2) of the adjacent blue fluorescent emitting layer (530), and thus all internal excitons can contribute to phosphorescent emission. That is, the non-blue phosphorescent emitting layer (520) can utilize all of the supplied 80% of excitons for emission, thus having an internal quantum efficiency of 80%.

[0137] In this case, the blue fluorescent emitting layer (530) is formed with a ratio of triplets to singlets of 3:1, with singlets in the singlet excitation level (S1) functioning for blue fluorescence, and between the triplet excitation levels of the second dopant (d2) and the second host (h2), a dexter energy transition occurs from the second dopant (d2), which has a higher second triplet excitation level, to the second host (h2), which has a lower second triplet excitation level, and transitions to a singlet excitation transition through TTF action between the triplets in the triplet excitation level of the second host (h2), which enables additional fluorescent fluorescence through transition to the singlet excitation level of the second dopant (d2). Approximately, additional fluorescent fluorescence using TTF action is possible at an exciton ratio of 1 / 5. Accordingly, the blue fluorescent emitting layer (530) has an internal quantum efficiency of 8% (20%*1 / 4+15%*1 / 5), which is the sum of 5% corresponding to 20%*1 / 4 due to a singlet ratio of 1 / 4 and 15%*1 / 5 due to additional fluorescent emission caused by dexter energy transfer from the internal second dopant (d2) to the second host (h2) and TTF action.

[0138] That is, as shown in Table 3, in the case of FIG. 11c, the sum of the internal quantum efficiencies of the non-blue phosphorescent emitting layer (520) and the blue fluorescent emitting layer (530) is 88%, and it can be confirmed that there is an improvement in internal quantum efficiency compared to the comparative example in which the Dexter energy transfer cannot be suppressed.

[0139] Experiments in FIGS. 11a to 11c and Table 3 show that the non-blue phosphorescent emitting layer (520) is fully utilized for phosphorescent emission, and it can be confirmed that the utilization of internal quantum efficiency is high when the initial exciton distribution ratio of the non-blue phosphorescent emitting layer (520) is increased. However, in any case, the non-blue phosphorescent emitting layer (520) does not have exciton reduction due to dexter energy transfer, and thus it can be confirmed that the light-emitting device according to the fourth embodiment of the present invention can increase internal quantum efficiency without exciton reduction of the non-blue phosphorescent emitting layer.

[0140] division Fig. 11a Fig. 11b Fig. 11c Initial exciton ratio (520:530) 50%:50% 75%:25% 80%:20% Internal quantum efficiency IQE IQE IQE non-blue phosphorescent light-emitting layer (520) 50% 75% 80% blue fluorescent light-emitting layer (530) 20% 10% 8% Total efficiency of the light-emitting layer 70% 85% 88%

[0141] Below, we examine an example of applying a light-emitting element with a multiple stack structure.

[0142] FIG. 12 is a cross-sectional view showing a light-emitting element according to another embodiment of the present invention, and FIG. 13 is a cross-sectional view showing a specific example of FIG. 12.

[0143] As shown in FIG. 12, a light-emitting element according to another embodiment of the present invention comprises first to fourth stacks (S1, S2, S3, S4) separated by charge generating layers (CGL1, CGL2, CGL3, CGL4) between first and second electrodes (110, 200) facing each other.

[0144] Any one of the first to fourth stacks (S1 to S4) (S1) may be a stack comprising a hole transport layer (310), a non-blue phosphorescent emitting layer (320 or 520), a blue fluorescent emitting layer (330 or 530), and an electron transport layer (340), as described in FIGS. 1 and 8. In the illustrated example, the first stack (S1) is shown as having a structure in which the non-blue phosphorescent emitting layer (320 or 520) and the blue fluorescent emitting layer (330 or 520) are in contact. However, not limited to the illustrated example, the configuration of the stack in which the non-blue phosphorescent emitting layer (320 or 520) and the blue fluorescent emitting layer (330 or 520) are in contact may be placed in any one of the second to fourth stacks (S2 to S4) other than the first stack (S1).

[0145] Here, the non-blue phosphorescent light-emitting layer (320 or 520) may be a light-emitting layer that emits red light. In this case, the non-blue phosphorescent light-emitting layer (320 or 520) may have a light-emitting peak of 600 nm to 650 nm wavelength, and the blue fluorescent light-emitting layer (330 or 530) may have a light-emitting peak of 430 nm to 480 nm wavelength.

[0146] In addition, the remaining stacks (S2 to S4) have a different configuration from the first stack (S1) and have at least a single light-emitting layer as the light-emitting layer, one of which may be a green stack including a green light-emitting layer, and the remaining stacks may be blue stacks including a blue light-emitting layer. In the illustrated example, the third stack (S3) is a green stack and the second and fourth stacks (S2, S4) are blue stacks, but this is not limited thereto, and the light-emitting stack having a structure in which the non-blue phosphorescent light-emitting layer (320 or 520) and the blue fluorescent light-emitting layer (330 or 530) are in contact, or the green stack having a green light-emitting layer as the light-emitting layer, may be changed to a different location.

[0147] The light-emitting element according to another embodiment of the present invention shown in FIG. 12 implements white light through multiple stacking. As a light-emitting layer, a green stack (S3) that includes a single green light-emitting layer that emits green light with the highest contribution to white light, and the remaining stack configuration includes a blue light-emitting layer to compensate for the lack of efficiency of blue light.

[0148] Meanwhile, the example of FIG. 12 shows an example in which four stacks are configured between the first and second electrodes (110, 200). However, the concept of the present invention is applicable as long as the light-emitting element of the present invention has a configuration of two or more stacks, including a non-blue phosphorescent light-emitting layer (320 or 520) and a blue fluorescent light-emitting layer (330 or 530) as light-emitting layers in one stack, and a light-emitting stack capable of emitting green light in the remaining stack. That is, as a light-emitting element according to another embodiment of the present invention, it is possible to modify the example to include a stack having a multilayer light-emitting layer in contact with a non-blue phosphorescent light-emitting layer and a blue fluorescent light-emitting layer, and a green stack including a green light-emitting layer as a basic configuration, and additionally include one or more blue light-emitting stacks to supplement the insufficient efficiency of blue.

[0149] The layer not described in Fig. 12 is a common layer of the hole transport layer or electron transport layer.

[0150] As shown in FIG. 13, a light-emitting element according to another embodiment of the present invention includes a first electrode (110) and a second electrode (200) facing each other, and first to fourth stacks (S1, S2, S3, S4) separated by a charge generating layer (171, 172, 173) between the first electrodes (110, 200).

[0151] The charge generation layers (171, 172, 173) include an n-type charge generation layer (171n, 172n, 173n) that generates electrons and transfers them to the electron transport layer of an adjacent stack, and a p-type charge generation layer (171p, 172p, 173p) that generates holes and transfers them to the hole transport layer of an adjacent stack.

[0152] The first stack (S1) includes a hole injection layer (131), a first hole transport layer (132), a red phosphorescent emitting layer (133), a blue fluorescent emitting layer (134), and a first electron transport layer (135), and emits red and blue light together. As described in the light-emitting device according to the first to fourth embodiments above, adjacent red phosphorescent emitting layers (133) and blue fluorescent emitting layers (134) are in the same stack, and since light emission occurs through the distribution of excitons, the initial exciton distribution ratio can be adjusted to increase the red light emission efficiency or the blue light emission efficiency. The blue fluorescent emitting layer (134) has a triplet excitation level of the second host (h2) that is between the triplet excitation level of the second dopant (d2) in the blue fluorescent emitting layer (134) and the triplet excitation level of the first dopant (o1) of the red phosphorescent emitting layer (133), or the second host (h2) further has a spacer that can prevent dexter energy transfer from the red dopant on the outer edge of the core compound, thereby suppressing dexter energy transfer from the red phosphorescent emitting layer (133) to the blue fluorescent emitting layer (134). Accordingly, the red phosphorescent emitting layer (133) can utilize all of the initially distributed excitons for light emission, and in some cases, conversely, there is an advantage that the efficiency of phosphorescent light emission can be improved by the triplet added through dexter energy transfer in the blue fluorescent emitting layer (134). In addition, the blue fluorescent light-emitting layer (134) prevents the phenomenon of extinguishing due to residual triplet by suppressing the dexter energy transfer from the red phosphorescent light-emitting layer (133) so that additional triplets are not supplied, thereby enabling an improved lifespan.

[0153] The red phosphorescent light-emitting layer (133) provided in the first stack (S1) follows the characteristics and material composition of the non-blue phosphorescent light-emitting layer (320 or 520) of the light-emitting element described in the first to fourth embodiments, and the blue fluorescent light-emitting layer (134) follows the characteristics and material composition of the blue fluorescent light-emitting layer (330 or 530) of the light-emitting element described in the first to fourth embodiments.

[0154] The first host (h1) of the red phosphorescent light-emitting layer (133) may be, for example, any one of BeBq2, BeMq2 and BAlq, and the first dopant (d1) may be, for example, an iridium complex compound.

[0155] The second stack (S2) includes a second hole transport layer (141), a first blue light-emitting layer (142), and a second electron transport layer (143), and emits blue light.

[0156] The third stack (S3) includes a third hole transport layer (151), a green light-emitting layer (152), and a third electron transport layer (153), and emits green light.

[0157] The fourth stack (S4) includes a fourth hole transport layer (161), a second blue light-emitting layer (162), a fourth electron transport layer (163), and an electron injection layer (164), and emits blue light.

[0158] The second and fourth stacks (S2, S4) emitting blue light are intended to compensate for the insufficient efficiency of blue light, which has lower visibility compared to other colors in a white light-emitting element. The first and second blue light-emitting layers (142, 162) provided in the second and fourth stacks (S2, S4) preferably have a full width at half maximum of 40 nm or less to enhance pure color characteristics when the light-emitting element is used in a display device. The first and second blue light-emitting layers (142, 162) may each, or a part thereof, be the same material as the blue fluorescent light-emitting layer (134) in the first stack (S1). In some cases, the first and second blue light-emitting layers (142, 162) are identical to the second dopant (d2) of the blue fluorescent light-emitting layer (134), and the second host (h2) may have different components from the second host of the blue fluorescent light-emitting layer (134) to enhance the excitation characteristics of the second dopant (d2). In some cases, at least one of the first and second blue light-emitting layers (142, 162) may use a blue phosphorescent dopant instead of a blue fluorescent dopant, or may include a combination of a fluorescent dopant and a phosphorescent dopant.

[0159] In addition, the green light-emitting layer (152) of the third stack (S3) may be a green phosphorescent light-emitting layer. The light-emitting element according to another embodiment of the present invention according to FIG. 13 includes a green phosphorescent light-emitting layer that emits a single green color as a light-emitting layer, and thus can improve efficiency by more than 2 times compared to a structure in which excitons are distributed in a configuration in which a plurality of phosphorescent light-emitting layers are in contact. In addition, the red phosphorescent light-emitting layer (133) of the first stack (S1) can significantly reduce the ratio of excitons that are extinguished by suppressing the dexter energy transfer from the red phosphorescent light-emitting layer (133) to the blue fluorescent light-emitting layer (134) when the first to fourth embodiments of the present invention are applied, and can increase the efficiency within the red phosphorescent light-emitting layer (133), and thus can improve efficiency compared to a stack structure in which a red phosphorescent light-emitting layer and a different color phosphorescent light-emitting layer are in contact.

[0160] Hereinafter, a light-emitting display device of the present invention applying the light-emitting element of the present invention will be described.

[0161] Meanwhile, the light-emitting element described above can be applied commonly to multiple subpixels to emit white light toward the electrode side of the emission side.

[0162] FIG. 14 is a cross-sectional view showing a light-emitting display device of the present invention applying the light-emitting element of FIG. 13.

[0163] As shown in FIG. 14, the display device of the present invention may include a substrate (100) having a plurality of subpixels (R_SP, G_SP, B_SP, W_SP), a white light-emitting element (OLED) commonly provided on the substrate (100), a thin-film transistor (TFT) provided on each of the subpixels and connected to the first electrode (110) of the white light-emitting element (OLED), and a color filter layer (109R, 109G, 109B) provided on the lower side of the first electrode (110) of at least one of the subpixels.

[0164] The illustrated example describes an example including a white subpixel (W_SP), but is not limited thereto; a structure in which the white subpixel (W_SP) is omitted and only red, green, and blue subpixels (R_SP, G_SP, B_SP) are provided may also be possible. In some cases, a combination of cyan, magenta, and yellow subpixels that can express white by replacing and combining the red, green, and blue subpixels is also possible.

[0165] The thin-film transistor (TFT) described above includes, for 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). Additionally, a channel protection layer (105) may be further provided above the portion where the channel of the semiconductor layer (104) is located to prevent direct connection between the source / drain electrodes (106a, 106b) and the semiconductor layer (104).

[0166] A gate insulating film (103) is provided between the gate electrode (102) and the semiconductor layer (104).

[0167] The semiconductor layer (104) may be, for example, any one of oxide semiconductor, amorphous silicon, and polycrystalline silicon, or a combination of two or more of the above-mentioned ones. For example, if the semiconductor layer (104) is an oxide semiconductor, the heating temperature required for forming a thin-film transistor can be lowered, so the degree of freedom in using the substrate (100) is high, making it advantageous for application as a flexible display device.

[0168] Additionally, the drain electrode (106b) of the thin-film transistor (TFT) can be connected to the first electrode (110) and the contact hole (CT) region provided within the first and second protective films (107, 108).

[0169] The first protective layer (107) is provided primarily to protect the thin-film transistor (TFT), and a color filter (109R, 109G, 109B) may be provided on top of it.

[0170] A light-emitting element capable of producing white is required as a display device, and a subpixel can produce various colors by transmitting light of the corresponding wavelength for each subpixel through a color filter (109R, 109G, 109B) selected by wavelength transmittance.

[0171] When the plurality of subpixels include a red subpixel, a green subpixel, a blue subpixel, and a white subpixel, the color filter is divided into first to third color filters (109R, 109G, 109B) for the remaining subpixels excluding the white subpixel (W_SP), thereby allowing white light emitted through the first electrode (110) to pass through according to each wavelength. Then, a second protective film (108) is formed on the lower side of the first electrode (110), covering the first to third color filters (109R, 109G, 109B). The first electrode (110) is formed on the surface of the second protective film (108), excluding the contact hole (CT).

[0172] The example illustrated above shows that a color filter is omitted in the white subpixel (W_SP), but is not limited thereto; a transparent organic film may also be provided in the area corresponding to the light-emitting part to reduce the step difference with the adjacent subpixel corresponding to the white subpixel (W_SP).

[0173] Here, the light-emitting element (OLED) is characterized by having a structure in which a non-blue phosphorescent light-emitting layer and a blue fluorescent light-emitting layer are in contact between the hole transport layer and the electron transport layer in any one of the stacks (S1, S2, S3, S4) separated into charge generation layers (CGL1, CGL2, CGL3, CGL4) as shown in FIG. 13, between the first and second electrodes (110, 200), a transparent first electrode (110), a second electrode (200) of a reflective electrode opposite thereto, and between the first and second electrodes (110, 200).

[0174] The first electrode (110) is divided into separate subpixels, and the remaining layers of the white light-emitting element (OLED) are provided integrally across the entire display area without separation by subpixel.

[0175] Here, 119, which is not described, represents a Bank, and BH between banks means a Bank Hole. Light emission occurs in the area opened through the Bank Hole, and the Bank Hole defines the light-emitting part of each subpixel.

[0176] Meanwhile, the lower side of the first electrode (110) includes a substrate (100), and is referred to as a thin film transistor array substrate (1000) including a thin film transistor (TFT), a color filter (109R, 109G, 109B), and insulating films on which these components are arranged.

[0177] FIG. 15 is a graph showing the white spectrum of a light-emitting element according to the first to fourth experimental examples (Ex1 to Ex4).

[0178] division EQE(%) Color temperature (K) Full White [nit] BT2020 Overlap (%) Blue Green Red R_SP G_SP B_SP W_SP Ex1 16.6 22.2 22.6 5632 510.1 388.6 282.2 195.5 85.7 Ex2 18.6 22.2 20.6 6402 465.9 387.9 316.8 240.1 86.1 Ex3 20.6 22.2 18.6 7381 421.9 387.5 351.5 259.5 86.3 Ex4 22.6 22.2 16.6 8669 378.0 387.5 386.4 270.4 86.4

[0179] The first experimental example (Ex1) of FIG. 15 and Table 1 has an external quantum efficiency (EQE) of blue light emitted through the light-emitting element of FIG. 13 set to 16.6%, an external quantum efficiency of green light set to 22.2%, and an external quantum efficiency of red light set to 22.6%. In addition to the blue fluorescent light-emitting layer (134) in contact with the red phosphorescent light-emitting layer of the first stack in the light-emitting element of FIG. 13, the second and fourth blue light-emitting stacks also have first and second blue light-emitting layers (142, 163), thereby supplementing the external quantum efficiency of blue light when a single blue light-emitting layer is provided. The external quantum efficiency (EQE) is before the application of the color filter. Furthermore, the second experimental example (Ex2) to the fourth experimental example (Ex4) each show that, compared to the first experimental example (Ex1), the blue luminescence efficiency was increased to 2%, 4%, and 6%, and the red luminescence efficiency was decreased to 2%, 4%, and 6%. This switching of luminescence efficiency between the red phosphorescent emitting layer and the blue fluorescent emitting layer is possible by adjusting the initial exciton ratio of the adjacent red phosphorescent emitting layer and the blue fluorescent emitting layer, as shown in FIGS. 3a to 3c or FIGS. 11a to 11c.

[0180] In addition, the illuminance when full white is applied in each experimental example (Ex1 to Ex4) represents the illuminance appearing in the red, green, blue, and white subpixels when the light-emitting element of Fig. 13 is applied to the light-emitting display device of Fig. 14.

[0181] In the first experimental example (Ex1), when full white is applied, the white illuminance corresponds to 195.5 nits, and in this case, the color temperature is 5632K. In this case, it can be seen that there is an overlap ratio of 85.7% with respect to the BT2020 standard value representing the color gamut.

[0182] As shown in Table 4 and Figure 15, in the second experimental example (Ex2), when the external quantum efficiency of blue is increased by 2% and the external quantum efficiency of red is increased by 2% compared to the first experimental example (Ex1), the illuminance at the white subpixel becomes 240.1 nit and the color temperature becomes 6402K, confirming that the efficiency of white is improved. In addition, the overlap ratio with respect to the BT2020 standard value of the second experimental example (Ex2) is 86.1%, which is improved compared to the first experimental example (Ex1).

[0183] As shown in Table 4 and Figure 15, in the third experimental example (Ex3), when the external quantum efficiency of blue and the external quantum efficiency of red are increased by 4% compared to the first experimental example (Ex1), the illuminance at the white subpixel becomes 259.5 nit and the color temperature becomes 7381K, confirming that the efficiency of white is improved. In addition, the overlap ratio with respect to the BT2020 standard value of the third experimental example (Ex3) is 86.3%, which is improved compared to the second experimental example (Ex2).

[0184] As shown in Table 4 and Figure 15, in the fourth experimental example (Ex4), when the external quantum efficiency of blue is increased by 6% and the external quantum efficiency of red is increased by 6% compared to the first experimental example (Ex1), the illuminance in the white subpixel becomes 270.4 nit and the color temperature becomes 8660K, confirming that the efficiency of white is improved. In addition, the overlap ratio with respect to the BT2020 reference value of the fourth experimental example (Ex4) is 86.3%, which is improved compared to the third experimental example (Ex3).

[0185] In other words, the experiment according to Table 4 and Fig. 15 implies that in a structure where a red phosphorescent emitting layer and a blue fluorescent emitting layer are in contact, when the external quantum efficiency is switched to the blue fluorescent emitting layer according to the initial ratio of excitons, the efficiency of white can be significantly improved, high color temperature expression is possible, and high color gamut standards increase the overlap ratio with BT2020, enabling high-quality display. In particular, as one moves toward the fourth experimental example (Ex4), the brightness balance between the red subpixel, green subpixel, and blue subpixel improves when full white is applied, and the difference in the required driving voltage for each subpixel can be reduced. In addition, brightness can be increased under the same driving voltage conditions as the first to third experimental examples (Ex1 to Ex3). Furthermore, a display device applying a light-emitting element in the fourth experimental example (Ex4), which has improved blue efficiency, causes each subpixel to undergo similar temporal changes during driving, thereby reducing the degradation deviation by region, enabling high color temperature expression, improving image quality, and meeting high color gamut standards.

[0186] Accordingly, the light-emitting element of the present invention and the light-emitting display device using the same prevent triplet concentration by dexter energy transfer to the blue fluorescent light-emitting layer in a multilayer light-emitting layer structure by contacting the blue fluorescent light-emitting layer and the non-blue phosphorescent light-emitting layer, and can utilize excitons with maximum efficiency without non-luminous loss in adjacent light-emitting layers.

[0187] In addition, by applying a structure combining a blue light-emitting stack and a green light-emitting stack in addition to a stack having a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer, the efficiency of blue can be improved. When expressing white using multiple stacks, the initial exciton ratio between adjacent blue fluorescent light-emitting layers and non-blue phosphorescent light-emitting layers is adjusted to increase the color temperature when expressing white, and when expressing full white, the balance of each subpixel is maintained, thereby reducing driving voltage deviation and enabling a similar lifespan in changes over time.

[0188] A light-emitting element according to one embodiment of the present invention comprises a first electrode and a second electrode that are spaced apart from each other and facing each other, a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer that are in contact with each other between the first electrode and the second electrode, a first common layer between the first electrode and the non-blue phosphorescent light-emitting layer, and a second common layer between the blue fluorescent light-emitting layer and the second electrode, wherein the non-blue phosphorescent light-emitting layer comprises a first host and a first dopant, and the blue fluorescent light-emitting layer may comprise a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host that transfers energy to the singlet excitation level (S1) of the second dopant and suppresses a dexter energy transfer from the first dopant.

[0189] Additionally, the second host may have a triplet excitation level between the first dopant and the second dopant. The triplet excitation level of the second host may be 2.1 eV to 2.4 eV.

[0190] And, the singlet excitation level of the second host is higher than the singlet excitation level of the second dopant, and a Dexter energy transition may occur from the triplet excitation level of the second host to the triplet excitation level of the first dopant.

[0191] Alternatively, the second host may have a core compound and a spacer of 1 nm or more on the outer edge of the core compound.

[0192] The spacer is any one of a methyl group, a tertiary-butyl group, and a phenyl group, and the spacer may be substituted on the terminal group of the core compound. The core compound of the second host may have a triplet excitement level lower than that of the first dopant.

[0193] The above non-blue phosphorescent emitting layer may have an emission peak at a wavelength of 600 nm to 650 nm, and the above blue fluorescent emitting layer may have an emission peak at a wavelength of 430 nm to 480 nm.

[0194] A first stack comprising the first common layer, the non-blue phosphorescent emitting layer, the blue fluorescent emitting layer, and the second common layer, and a second to fourth stack may be further included between the second electrode. Additionally, a charge generating layer may be included between each of the first to fourth stacks, and any one of the second to fourth stacks may include a green phosphorescent emitting layer as a single emitting layer, and at least one other stack may include a blue fluorescent emitting layer as a single emitting layer.

[0195] The above second host may be further included in the above non-blue phosphorescent light-emitting layer.

[0196] The above-mentioned non-blue phosphorescent emitting layer may include a first layer comprising the first host, the second host, and the first dopant, which is in contact with one surface of the blue fluorescent emitting layer, and a second layer comprising the first host and the first dopant, which is in contact with the other surface of the first layer that is not in contact with the blue fluorescent emitting layer.

[0197] Additionally, a light-emitting element according to another embodiment of the present invention comprises a first electrode and a second electrode that are spaced apart from each other and facing each other, a plurality of stacks between the first and second electrodes, and a charge generating layer provided between the stacks. One of the stacks has a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer in contact with each other, and at least one of the other stacks has a single light-emitting layer as the light-emitting layer, and the non-blue phosphorescent light-emitting layer includes a first host and a first dopant, and the blue fluorescent light-emitting layer may include a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host having a triplet excitation level between the first dopant and the second dopant.

[0198] In addition, the second host may include at least one compound among carbazole-based, fluorine-based, dibenzofuran-based, triazine-based, and quinazoline-based compounds.

[0199] A light-emitting element according to another embodiment comprises a first electrode and a second electrode that are spaced apart from each other and facing each other, a plurality of stacks between the first and second electrodes, and a charge generating layer provided between the stacks. In addition, one of the stacks has a blue fluorescent light-emitting layer and a non-blue phosphorescent light-emitting layer in contact with each other, and at least one of the other stacks has a single light-emitting layer as the light-emitting layer, and the non-blue phosphorescent light-emitting layer includes a first host and a first dopant, and the blue fluorescent light-emitting layer may include a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host having a core compound and a spacer of 1 nm or more on the outer edge of the core compound.

[0200] The above spacer is any one of a methyl group, a tertiary-butyl group, and a phenyl group, and the above spacer can be substituted on the terminal group of the core compound.

[0201] The above non-blue phosphorescent emitting layer may have an emission peak at a wavelength of 600 nm to 650 nm, and the above blue fluorescent emitting layer may have an emission peak at a wavelength of 430 nm to 480 nm.

[0202] The plurality of stacks between the first and second electrodes may include four or more, and the stack having the non-blue phosphorescent emitting layer and the blue fluorescent emitting layer in contact may be in contact with at least one of the first electrode and the second electrode.

[0203] The plurality of stacks between the first and second electrodes may include four or more, and the stack having a non-blue phosphorescent emitting layer and a blue fluorescent emitting layer in contact may include a blue stack having at least one blue emitting layer and a phosphorescent stack having a phosphorescent emitting layer that emits a color different from the blue phosphorescent emitting layer.

[0204] In addition, a light-emitting display device according to one embodiment of the present invention may include a substrate having a plurality of subpixels, a driving circuit including at least one transistor provided in each of the subpixels, and a light-emitting element described above connected to the driving circuit in each of the subpixels.

[0205] Corresponding to at least one of the plurality of subpixels, a color filter may be further included between the substrate and the light-emitting element.

[0207] Meanwhile, it will be obvious to those skilled in the art that the present invention described above is not limited to the embodiments and attached drawings described above, and that various substitutions, modifications, and changes are possible within the scope of the technical concept of the present invention. Explanation of the symbols

[0208] 100: Substrate 110, 300, 500: First electrode 131, 305: Hole injection layer 132, 141, 151, 161: Hole transport layer 133: Red phosphorescent emitting layer 134: Blue fluorescent emitting layer 135, 143, 153, 163, 340: Electron transport layer 164, 350: Electron injection layer 200, 400, 600: Second electrode 320, 520: Non-blue phosphorescent emissive layer 330, 530: Blue fluorescent emissive layer S, S1~S4: Stacks CML1: First common layer CML2: Second common layer h1: First host d1: 1st Dopant h2: 2nd Host d2: Second Dopant

Claims

Claim 1 A light-emitting device comprising: a first electrode and a second electrode spaced apart from each other; a blue fluorescent emitting layer and a non-blue phosphorescent emitting layer in contact with each other between the first electrode and the second electrode; a first common layer between the first electrode and the non-blue phosphorescent emitting layer; and a second common layer between the blue fluorescent emitting layer and the second electrode, wherein the non-blue phosphorescent emitting layer comprises a first host and a first dopant, and the blue fluorescent emitting layer comprises a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host that transfers energy to the singlet excitation level (S1) of the second dopant and suppresses a dexter energy transfer from the first dopant. Claim 2 In claim 1, the second host is a light-emitting element having a triplet excitation level between the first dopant and the second dopant. Claim 3 A light-emitting element according to claim 2, wherein the triplet excitation level of the second host is 2.1 eV to 2.4 eV. Claim 4 A light-emitting device according to claim 2, wherein the singlet excitation level of the second host is higher than the singlet excitation level of the second dopant, and a dexter energy transition occurs from the triplet excitation level of the second host to the triplet excitation level of the first dopant. Claim 5 In claim 1, the second host is a light-emitting element having a core compound and a spacer of 1 nm or more on the outer edge of the core compound. Claim 6 In claim 5, the spacer is any one of a methyl group, a tertiary-butyl group, and a phenyl group, and the spacer is a light-emitting element substituted at the terminal group of the core compound. Claim 7 In claim 6, the core compound of the second host is a light-emitting element having a triplet excitation level lower than that of the first dopant. Claim 8 A light-emitting device according to claim 1, wherein the non-blue phosphorescent light-emitting layer has a light emission peak of 600 nm to 650 nm wavelength, and the blue fluorescent light-emitting layer has a light emission peak of 430 nm to 480 nm wavelength. Claim 9 A light-emitting device according to claim 8, further comprising a first stack including the first common layer, the non-blue phosphorescent light-emitting layer, the blue fluorescent light-emitting layer, and the second common layer, and second to fourth stacks between the second electrode, wherein each of the first to fourth stacks includes a charge generating layer, and any one of the second to fourth stacks includes a green phosphorescent light-emitting layer as a light-emitting layer and at least one other includes a blue fluorescent light-emitting layer as a light-emitting layer. Claim 10 In claim 1, the second host is a light-emitting element further included in the non-blue phosphorescent light-emitting layer. Claim 11 In claim 1, the non-blue phosphorescent emitting layer comprises a first layer having one surface in contact with the blue fluorescent emitting layer and including the first host, the second host, and the first dopant, and a second layer having the other surface of the first layer that is not in contact with the blue fluorescent emitting layer and including the first host and the first dopant. Claim 12 A light-emitting device comprising: a first electrode and a second electrode spaced apart from each other; a plurality of stacks between the first and second electrodes; and a charge generating layer provided between the stacks, wherein any one of the stacks has a blue fluorescent emitting layer and a non-blue phosphorescent emitting layer in contact with each other, and at least one of the other stacks has a single emitting layer as the emitting layer, wherein the non-blue phosphorescent emitting layer includes a first host and a first dopant, and the blue fluorescent emitting layer includes a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host having a triplet excitation level between the first dopant and the second dopant. Claim 13 In claim 12, the second host is a light-emitting device comprising at least one compound among carbazole-based, fluorine-based, dibenzofuran-based, triazine-based, and quinazoline-based compounds. Claim 14 A light-emitting device comprising: a first electrode and a second electrode spaced apart from each other; a plurality of stacks between the first and second electrodes; and a charge generating layer provided between the stacks, wherein any one of the stacks has a blue fluorescent emitting layer and a non-blue phosphorescent emitting layer in contact with each other, and at least one of the other stacks has a single emitting layer as the emitting layer, wherein the non-blue phosphorescent emitting layer includes a first host and a first dopant, and the blue fluorescent emitting layer includes a second dopant having a singlet-triplet excitation level difference (ΔEst) smaller than that of the first dopant and a triplet excitation level (T1) higher, and a second host having a core compound and a spacer of 1 nm or more on the outer edge of the core compound. Claim 15 In claim 14, the spacer is any one of a methyl group, a tertiary-butyl group, and a phenyl group, and the spacer is a light-emitting element substituted at the terminal group of the core compound. Claim 16 A light-emitting device according to claim 14 or 15, wherein the non-blue phosphorescent light-emitting layer has a light emission peak of 600 nm to 650 nm wavelength and the blue fluorescent light-emitting layer has a light emission peak of 430 nm to 480 nm wavelength. Claim 17 In claim 14 or 15, the plurality of stacks between the first and second electrodes comprises four or more, and the stack having the non-blue phosphorescent emitting layer and the blue fluorescent emitting layer in contact is a emitting element in contact with at least one of the first electrode and the second electrode. Claim 18 In claim 14 or 15, the plurality of stacks between the first and second electrodes comprises four or more, and a stack other than the stack having the non-blue phosphorescent emitting layer and the blue fluorescent emitting layer in contact comprises a blue stack including at least one blue emitting layer and a phosphorescent stack including a phosphorescent emitting layer emitting a color different from the non-blue phosphorescent emitting layer. Claim 19 A light-emitting display device comprising: a substrate having a plurality of subpixels; a driving circuit including at least one transistor provided in each of the subpixels; and a light-emitting element according to any one of claims 1 to 11, connected to the driving circuit in each of the subpixels. Claim 20 In claim 19, a light-emitting display device further comprising a color filter between the substrate and the light-emitting element, corresponding to at least one of the plurality of subpixels.

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