Organic light-emitting diode

Abstract

This invention provides an organic light-emitting diode with improved quantum efficiency by efficiently transferring energy from the excited complex to the dopant. [Solution] An organic light-emitting diode comprising a first electrode, a second electrode, and a light-emitting layer containing a multifunctional compound, wherein the multifunctional compound contains an excited complex-forming molecule and a light-emitting molecule.

Description

[Technical Field]

[0001] This invention relates to an organic light-emitting diode. [Background technology]

[0002] Organic light-emitting diodes (OLEDs) are devices that emit light by forming excitons in the light-emitting layer when holes injected from the anode and electrons injected from the cathode combine. They were first reported by CWTang in Appl. Phys. Lett 51, 913 in 1987. The HOMO wavefunction of the light-emitting layer host contains two electrons with different spins. In OLEDs, electrons directly enter and exit the organic material, with electrons exiting at the HOMO (Highest Occupied Molecular Orbital) level and electrons being injected at the LUMO (Lowest Unoccupied Molecular Orbital) level. At this time, the spin direction of the entering and exiting electrons is not fixed, so the formed excitons consist of a triplet with the same spin direction and a singlet with a different spin direction. In organic materials, due to the exchange energy and the repulsion energy between electrons, the energy of the triplet is usually small, around 0.5 eV to 1 eV. Theoretically, the ratio of singlet to triplet states is 25% to 75%, with singlet energy diverging into light and triplet energy being lost as heat. To increase the internal quantum efficiency of OLED devices, the triplet state must be induced to diverge into light. In a 1997 patent application (US6303238B1), Mark E. Thompson reported a technique to diverge the triplet state into light by increasing spin-orbit coupling using heavy metals such as Pt. In Nature, 2012, 492, 234-238, Chihaya Adachi designed a molecule in which the overlap of the wave functions between the HOMO and LUMO within a single molecule is minimized. In this case, efficiency is increased by thermally activated delayed fluorescence (TADF), where the energy of the triplet state is transferred to the singlet state, causing light divergence. However, methods using heavy metals such as Pt and Ir are very expensive, and furthermore, since the blue color must be produced in the triplet state, the singlet HOMO-LUMO gap energy is high, which may cause problems with the stability of the material.Methods utilizing delayed fluorescence have drawbacks: the small overlap of the HOMO and LUMO wave functions results in a wide full width at half maximum (FWHM) of the emission spectrum, making it difficult to achieve a deep blue color, and there are also issues with the stability of the material.

[0003] Another method studied to reduce the energy difference between singlet and triplet states is the formation of an excited complex between a relatively electron-rich electron-donor molecule and an electron-deficient electron-acceptor molecule. When the electron-donor (or electron-acceptor) molecule absorbs light and enters an excited state, it undergoes a Coulomb interaction with the electron-acceptor (or electron-donor) molecule in the ground state. Two substances form an exciplex through interaction (Valeur, B, Berberan-santos, MN, Wiley-VCH Verlag GmbH & co. KGaA, 2nd edition, 2012). In this state, the difference between the triplet energy and the singlet energy is small, which can increase the divergence efficiency of light. However, even when such an excited complex is formed, it has a very broad emission spectrum with a full width at half maximum, which makes it difficult to realize a deep blue color. Furthermore, when doping with a dopant to obtain a deep blue color, the energy transfer from the excited complex to the dopant is not efficient, which makes it difficult to obtain high quantum efficiency. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The objective of this invention is to provide an organic light-emitting diode with improved quantum efficiency by efficiently transferring energy. The objects of the present invention are not limited to those mentioned above, and other objects and advantages of the present invention not mentioned can be understood from the following description and will be more clearly understood from the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof shown in the claims. [Means for solving the problem]

[0005] In one embodiment of the present invention, It includes a first electrode, a second electrode, and a light-emitting layer located between the first electrode and the second electrode. The light-emitting layer further includes, or does not include, an organic layer adjacent to one or both of the aforementioned surfaces. The light-emitting layer contains a multifunctional compound, The light-emitting layer or the adjacent organic layer contains an excitation complex-forming compound. The multifunctional compound comprises an excited complex-forming molecule and a light-emitting molecule. The excited complex-forming moiety forms an excited complex with the excited complex-forming compound, The light-emitting moiety emits light upon receiving excitation energy transfer from the excited complex. We provide organic light-emitting diodes. [Effects of the Invention]

[0006] The aforementioned organic light-emitting diode enables effective energy transfer between molecules within the multifunctional compound while reducing the energy difference between singlet and triplet states. Because it facilitates the manifestation of a deep blue color and the energy transfer is efficient, high quantum efficiency can be achieved. Along with the effects described above, the specific effects of the present invention will be described together with the following explanation of the specific matters for carrying out the invention. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram illustrates the mechanism of action of the aforementioned multifunctional compound. [Figure 2]A mechanism in which the excitation energy of an exciplex is transferred between moieties within the multifunctional compound and emits light in an organic light-emitting diode according to an embodiment of the present invention is schematically shown. [Figure 3] Absorption spectra and emission spectra measured for Compounds 1, 2, and 3. [Figure 4] An emission spectrum evaluated to determine whether Compound A forms an exciplex.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention belongs can easily implement them with reference to the drawings. The present invention can be embodied in several different forms and is not limited to the embodiments described herein.

[0009] An organic light-emitting diode according to an embodiment of the present invention includes a first electrode, a second electrode, and a light-emitting layer positioned between the first electrode and the second electrode, and further includes or does not include an organic layer adjacent to one or both surfaces of the light-emitting layer; the light-emitting layer includes a multifunctional compound, the light-emitting layer or the adjacent organic layer includes an exciplex-forming compound, the multifunctional compound includes an exciplex-forming moiety and a light-emitting moiety, the exciplex-forming moiety forms an exciplex with the exciplex-forming compound, and the light-emitting moiety emits light by receiving the excitation energy transfer of the exciplex.

[0010] The organic light-emitting diode improves the light-emitting efficiency by using the multifunctional compound that can increase the rate constant value related to the energy transfer rate.

[0011] The organic light-emitting diode exhibits high quantum efficiency while realizing deep blue color.

[0012] The excited complex-forming moiety is derived from a compound capable of forming an excited complex with the excited complex-forming compound.

[0013] The multifunctional compound is formed by the bonding of the excitation complex-forming compound, a compound capable of forming an excitation complex, and a luminescent compound. Thus, the excitation complex-forming moisture is derived from the excitation complex-forming compound and the compound capable of forming an excitation complex. Furthermore, the luminescent moisture is attributable to the luminescent compound.

[0014] The multifunctional compound comprises an excited complex-forming moisture originating from the excited complex-forming compound and a light-emitting moisture originating from the light-emitting compound.

[0015] The mechanism of excited complex formation is a phenomenon that occurs between two molecules, where first one molecule absorbs light corresponding to the HOMO-LUMO gap and enters an excited state. e) The molecule then forms an excited complex through interactions with other surrounding molecules. When the excited complex emits light, the two molecules return to their original state.

[0016] When the two molecules are of the same type, they are called an excited dimer or excimer; when the two molecules are of different types, they are called an excited complex or exciplex. In this specification, the excited complex is explained using the example of the two molecules being of different types, but the same type can also be used.

[0017] In this specification, for convenience, the two molecules that form the excited complex are referred to as the first excited complex-forming compound and the second excited complex-forming compound, respectively. For convenience of distinction, the compound that can form an excited complex with the aforementioned excited complex-forming compound is called the first excited complex-forming compound, and the aforementioned excited complex-forming compound is called the second excited complex-forming compound. Thus, the excited complex-forming molecule is derived from the first excited complex-forming compound, the organic layer contains the second excited complex-forming compound, and both the first excited complex-forming compound and the second excited complex-forming compound can form an excited complex.

[0018] The first excitation complex-forming compound and the second excitation complex-forming compound may each be a single molecule capable of forming an excitation complex. As stated above, in this specification, the "first" and "second" designations of the first excitation complex-forming compound and the second excitation complex-forming compound are for convenience of distinction, and for example, the first excitation complex-forming compound and the second excitation complex-forming compound may be opposite to each other.

[0019] The first excited complex-forming compound and the second excited complex-forming compound may be the same or different.

[0020] In organic light-emitting diode devices, if a material with low ionization energy and a material with high electron affinity are used together in the light-emitting layer, an excited complex is formed during the electron transfer process. If a light-emitting compound is mixed with this excited complex as a dopant, the dopant may absorb the exciton energy of the excited complex, causing light emission. For such light emission to occur, the energy transfer efficiency from the excited complex to the dopant must be high. The energy transfer method is the optical method described in Equation 1 below. There are two methods: TIFF2026065060000002.tif9127 and the electron method (Dexter Electron Transfer) shown in equation 2 below.

[0021] TIFF2026065060000003.tif9127

number

[0022] Dexter Electron Transfer

number

[0023]

number

[0024] The inventors have discovered the multifunctional compound as a novel compound that allows r to approach 0 in equations 1 and 2. The inventors reason that the advantages of r approaching 0 are as follows.

[0025] Whether the energy transfer method is the optical method shown in Equation 1 or the electronic method shown in Equation 2, the important factor is the distance (r) between the energy donor (excited complex) and the energy acceptor (dopant). In the optical energy transfer method shown in Equation 1, as the distance (r) approaches 0, the quantum (excited complex) efficiency and decay time of the energy donor become irrelevant, and theoretically, the energy transfer rate approaches infinity. On the other hand, in the electron-mediated energy transfer method shown in Equation 2, as the distance (r) between the two substances approaches 0, the energy transfer rate is only affected by the overlap (J) between the emission and absorption spectra of the two substances.

[0026] The multifunctional compound is formed as a single molecule of a compound in which one of the two molecules that form an excited complex (corresponding to the first excited complex-forming compound in this invention) is bonded to a dopant (corresponding to the light-emitting compound in this invention). Applying the concepts of equations 1 and 2 to the multifunctional compound, when one of the two molecules that form an excited complex is bonded to a dopant, the distance is fixed and minimized, and the exciton energy formed in the excited complex is transferred to the dopant at a rapid speed, causing it to emit light.

[0027] In other words, the multifunctional compound is a compound obtained by bonding a first excited complex-forming compound, which is any one of two molecules capable of forming an excited complex, with a luminescent compound. As a result, the multifunctional compound contains an excited complex-forming molecule derived from (or originating from) the first excited complex-forming compound, and also contains a luminescent molecule derived from (or originating from) the luminescent compound. Since the excited complex-forming molecule is derived from (or originating from) the first excited complex-forming compound, it is possible to form an excited complex with the second excited complex-forming compound.

[0028] The aforementioned excited complex-forming moiety is capable of forming an excited complex with the (second) excited complex-forming compound, and therefore satisfies the following energy conditions. Let the HOMO energy of the excitation complex-forming moiety be E(1). HOMO and the LUMO energy be E(1). LUMO Also, let the HOMO energy of the (second) excitation complex-forming compound be E(2). HOMO and the LUMO energy be E(2). LUMO When these conditions are met, either <Condition 1> or <Condition 2> below must be satisfied. <Condition 1> |E(1)| ≤ |E(2)| HOMO and |E(1)| ≤ |E(2)| HOMO where |E(1)| ≤ |E(2)| LUMO and |E(1)| ≤ |E(2)| LUMO are satisfied. <Condition 2> |E(1)| ≥ |E(2)| HOMO and |E(1)| ≥ |E(2)| HOMO where |E(1)| ≥ |E(2)| LUMO and |E(1)| ≥ |E(2)| LUMO are satisfied. When the excitation complex-forming moiety and the (second) excitation complex-forming compound form an excitation complex, if the maximum emission wavelength energy of the excitation complex energy is E(ex), either <Condition 3> or <Condition 4> below must be satisfied. <Condition 3> |E(1)| - |E(2)| ≥ E(ex) HOMO |E(1)| - |E(2)| ≥ E(ex) LUMO where |E( )| - |E( )| ≥ E(ex) <Condition 4> |E(2)| - |E(1)| ≥ E(ex) HOMO |E(2)| - |E(1)| ≥ E(ex) LUMO where |E( )| - |E( )| ≥ E(ex)

[0029] Since an excitation complex can be formed between the first excitation complex-forming compound and the second excitation complex-forming compound, even if the HOMO energy of the first excitation complex-forming compound is set as E(1)HOMO and the LUMO energy as E(1)LUMO instead of the excitation complex-forming moiety, the above relationships, that is, the relationships of Conditions 1 to 4, can be applied identically.

[0030] The HOMO energy of a compound or moiety can be measured by methods such as cyclic voltage-current spectroscopy (CV), ultraviolet photoelectron spectroscopy (UPS), and AC2, while the LUMO energy can be measured using UV absorption spectroscopy or cyclic voltage-current spectroscopy (CV). Furthermore, the quantum efficiency of the materials mentioned herein can be obtained by measuring the luminescent material after dissolving it in a solution, by fabricating it as a film by co-depositing it with a host material, or by simultaneously dissolving the host material and luminescent material in a solution and then fabricating a film using spin coating or casting methods.

[0031] Figure 1 is a diagram illustrating the mechanism of action of the aforementioned multifunctional compound. Figure 1 shows a multifunctional compound formed by chemically linking a first excited complex-forming compound with a large HOMO-LUMO gap energy and a luminescent compound with a relatively small HOMO-LUMO gap energy. When the excited complex-forming moisture induced from the first excited complex-forming compound within the multifunctional compound is excited, energy is transferred to the luminescent moisture induced from the luminescent compound. This can be confirmed by comparing the absorption and emission spectra of compound 1 (the first excited complex-forming compound), compound 2 (the luminescent compound), and compound 3 (the multifunctional compound) in Figure 3.

[0032] The phenomenon in which the excitation complex energy is transferred from the excited complex formed by the interaction between the excited complex-forming moisture and the (second) excited complex-forming compound to the light-emitting moisture can be confirmed by fabricating an organic light-emitting diode. That is, when a charge is injected into the light-emitting layer of the organic light-emitting diode, the excited complex-forming moisture inside the multifunctional compound and the (second) excited complex-forming compound will first form an excited complex, and the energy of this excited complex will be transferred to the light-emitting moisture through the excited complex moisture. When the energy of the excited complex formed by the excited complex becomes greater than the energy of the light-emitting moisture, the excitation complex energy will be transferred to the light-emitting moisture.

[0033] Figure 2 schematically illustrates the mechanism by which the excitation energy of an excited complex is transferred between molecules within the multifunctional compound to produce light in an organic light-emitting diode according to one embodiment of the present invention.

[0034] The excited complex-forming moisture or the (second) excited complex-forming compound absorbs energy from the outside to form an excited complex, and the excitation energy of this excited complex is transferred to the light-emitting moisture connected through a chemical bond, causing a light-emitting phenomenon in the light-emitting moisture.

[0035] More specifically, when a charge is injected into the light-emitting layer composed of the excited complex-forming molecule of the multifunctional compound or the (second) excited complex-forming compound within the organic light-emitting diode, the excited complex-forming molecule and the second excited complex-forming compound interact within the multifunctional compound to form an excited complex. The energy of this thus formed excited complex is then transferred to the light-emitting molecule, which is located very close to the molecule within the multifunctional compound. This energy transfer between molecules within the multifunctional compound results in a very large rate constant, as the distance r in equations 1 and 2 becomes nearly zero, leading to highly efficient and fast energy transfer. Since the excited complex energy is transferred to the light-emitting molecule, and the light-emitting molecule can emit light with minimal energy loss, the multifunctional compound ultimately achieves the effect of emitting light with high efficiency by utilizing the excited complex energy.

[0036] The aforementioned organic light-emitting diode has the advantage of reducing the energy difference between singlet and triplet states by utilizing an excitation complex, while enabling effective energy transfer between molecules within the multifunctional compound. Because it contains light-emitting molecules, it facilitates the manifestation of a deep blue color, and the energy transfer is efficient, resulting in high quantum efficiency. However, the present invention is not limited to the manifestation of blue light, but can be applied to the emission of green, red, and near-infrared light.

[0037] The light-emitting molecule can be derived from a light-emitting material (referred to herein as a light-emitting compound) that can emit light through the movement of electrons in an organic light-emitting diode.

[0038] The aforementioned light-emitting compound (light-emitting material) may be a compound that can typically be used as a dopant in organic light-emitting diodes. A dopant capable of realizing a desired color can be selected to suit the purpose.

[0039] In one embodiment, the light-emitting moisture can have a conjugated structure with a quantum efficiency of 50% or more in the visible light wavelength range of 400 nm to 700 nm.

[0040] In one embodiment, the light-emitting moisture can have a conjugated structure with a quantum efficiency of 10% or more in the near-infrared wavelength region of 700 nm to 2200 nm.

[0041] Specific examples of the aforementioned light-emitting compound (or light-emitting material) may include, but are not limited to, the following compounds. [ka]

[0042] In the above formula, Ar and R may each be a substituted or unsubstituted C1 to C20 alkyl, a substituted or unsubstituted C6 to C30 aryl, a substituted or unsubstituted C5 to C30 heteroaryl, or a substituted or unsubstituted C6 to C30 arylamine, and X is the element nitrogen, oxygen, sulfur, carbon, silicone, Ge, or P.

[0043] Thus, the luminescent compound may be a boron compound, pyrene compound, or a compound having a conjugated structure containing nitrogen, as shown in the structural formula above, but is not limited to these. In addition, the luminescent compound can be any substance known to be a luminescent material. For example, the luminescent compound may be a luminescent material having a conjugated structure, such as anthracene, perylene, tetracene, chrysene, coumarin, or pyrometane.

[0044] In one embodiment, the luminescent compound and the luminescent moisture may contain boron and have a conjugated structure.

[0045] In one embodiment, the luminescent compound and the luminescent moisture may include a metal.

[0046] The emission mechanism of the aforementioned luminescent moiety can include fluorescence, which emits light in the singlet state; phosphorescence, which emits light in the triplet state; and delayed fluorescence, which emits light when energy is transferred from the triplet state to the singlet state.

[0047] In one embodiment, in the multifunctional compound, the excited complex-forming molecule linked by the chemical bond does not change the band gap energy of the luminescent molecule by more than 0.2 eV compared to the band gap energy of the luminescent compound before the chemical bond was formed. In this case, the excited complex molecule may not significantly affect the emission wavelength of the luminescent molecule, making it convenient to apply the known properties of the luminescent compound used in the design of color embodiment to the luminescent molecule.

[0048] In one embodiment, the second excitation complex-forming compound may not form an excitation complex with the luminescent compound. If the luminescent compound can form an excitation complex with the second excitation complex-forming compound, it can affect the emission wavelength of the luminescent moisture. If the emission wavelength of the luminescent moisture changes, it may be difficult to apply the properties of conventionally known luminescent compounds to the luminescent moisture when designing color realization, or when attempting to use a predetermined luminescent compound to realize a specific color, the change in the emission wavelength of the luminescent moisture may make it difficult to realize the desired hue.

[0049] In one embodiment, the band gap energy of the excited complex-forming moisture is 1 eV to 4.7 eV, and the band gap energy of the luminescent moisture is 0.5 eV to 3.5 eV.

[0050] In one embodiment, the difference in band gap energy between the excited complex-forming moisture and the luminescent moisture may be within 2 eV.

[0051] In one embodiment, the difference between the HOMO energy level of the excited complex-forming moisture and the HOMO energy level of the luminescent moisture may be within 1.9 eV.

[0052] In one embodiment, the difference in energy levels between the LUMO energy of the excited complex-forming moiety and the LUMO energy of the luminescent moiety may be within 1.9 eV.

[0053] In the multifunctional compound, the excited complex-forming molecule and the luminescent molecule are linked by a chemical bond. Specifically, the chemical bond may be a single bond, a double bond, a triple bond, or a coordination bond. Specifically, the chemical bond may be formed by a linking group mediated by the excited complex-forming molecule and the luminescent molecule, or by a direct bond without a linking group. Alternatively, the multifunctional compound may be formed by linking the excited complex-forming molecule and the luminescent molecule in a spiro structure.

[0054] When the first excitation complex-forming compound and the luminescent compound chemically bond to form the multifunctional compound, substituents and other components are appropriately deformed for these chemical bonds, thereby inducing the excitation complex-forming molecule and the luminescent molecule. At this time, the deformed portion for the chemical bond does not significantly change the intrinsic luminescence properties, band gap energy, energy efficiency, and other characteristics of the first excitation complex-forming compound and the luminescent compound, respectively. For example, substituents of the luminescent compound may be replaced by other substituents for the chemical bond to form the luminescent molecule, but the replaced substituents do not significantly affect the luminescence properties, band gap energy, energy efficiency, and other characteristics of the luminescent molecule.

[0055] The phrase "does not significantly affect" means that it does not deviate from the detailed explanation of the excited complex-forming moisture and the luminescent moisture described herein. Specifically, the fact that substituents of the first excited complex-forming compound and the luminescent compound are "appropriately" deformed during chemical bonding means that the excited complex-forming moisture of the resulting multifunctional compound maintains the conditions that satisfy the formation of an excited complex with the excited complex-forming compound, and that the luminescent moisture emits light upon receiving excitation energy transfer from the excited complex.

[0056] In one embodiment, the chemical bond can be mediated by substituted or unsubstituted carbon-6 to carbon-20 arylene, carbon, oxygen, nitrogen, silicone, Ge, S, or P atoms. For example, the chemical bond may also be formed by a linking group, which may include carbon, oxygen, nitrogen, silicone, Ge, S, or P atoms. For example, the chemical bond may be in a form in which the first excited complex-forming compound and the luminescent compound are directly linked without a linking group, and carbon, oxygen, nitrogen, silicone, Ge, S, or P contained in the excited complex-forming moisture or the luminescent moisture can be the linking positions.

[0057] In one embodiment, the excited complex-forming moisture and the light-emitting moisture are linked by a spiro structure. The spiro structure can be linked via carbon, silicone, or Ge.

[0058] The aforementioned multifunctional compound may have at least one hydrogen atom substituted with deuterium.

[0059] The multifunctional compound may contain a plurality of the excitation complex-forming molecules. In one embodiment, the multifunctional compound may contain a first excitation complex-forming molecule and a second excitation complex-forming molecule, and a detailed description of the first excitation complex-forming molecule and the second excitation complex-forming molecule is the same as that of the excitation complex-forming molecule, and these molecules may be identical or different from each other. The second excitation complex-forming molecule may be connected to the luminescent molecule or the first excitation complex-forming molecule.

[0060] The first excitation complex-forming compound and the second excitation complex-forming compound may be compounds capable of forming an excitation complex, as described above. The excitation complex can be formed between an electron donor molecule with a low ionization energy and an electron acceptor molecule with a high electron affinity.

[0061] Therefore, the first excited complex-forming compound and the second excited complex-forming compound may be electron donor molecules or electron acceptor molecules. However, if the first excited complex-forming compound is an electron donor molecule, the second excited complex-forming compound becomes an electron acceptor molecule, and if the first excited complex-forming compound is an electron acceptor molecule, the second excited complex-forming compound becomes an electron donor molecule.

[0062] Electron donor substances that primarily contain arylamines, where the nitrogen atom is located outside the aromatic ring, can be used. For example, the electron donor substance can be represented by the following chemical formula 1. [ka]

[0063] In the aforementioned chemical formula 1, Each Ar may independently be a substituted or unsubstituted aryl ring having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl ring having 5 to 30 carbon atoms, or a substituted or unsubstituted alkyl ring having 1 to 20 carbon atoms, and the two Ars can be linked together to form a fusion ring having 12 to 30 carbon atoms. In the aforementioned chemical formula 1, at least one hydrogen atom is either substituted for or unsubstituted for deuterium.

[0064] Electron acceptor substances primarily have a structure in which nitrogen is located within an aromatic ring, and those containing the following structures can be used. For example, the electron acceptor material may be any one of the structures represented by the following chemical formula 2. [ka]

[0065] In the aforementioned chemical formula 2, X may be nitrogen or carbon. n and m are integers from 0 to 6, except that if X is nitrogen, n+m is an integer from 1 to 3, and if X is carbon, n+m is an integer from 1 to 6. Each Ar may independently be a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C5 to C30 heteroaryl group, a substituted or unsubstituted C6 to C30 arylsilyl group, a substituted or unsubstituted C6 to C30 aryloxy group, a substituted or unsubstituted C1 to C20 alkylsilyl group, a substituted or unsubstituted C1 to C20 alkyl group, or a substituted or unsubstituted C6 to C30 aryl group containing phosphine or phosphine oxide, and the two Ars can be linked to form a C12 to C30 fusion ring. In the aforementioned chemical formula 2, at least one hydrogen atom is either substituted for or left unsubstituted for deuterium.

[0066] In this specification, the term “substitution” means that a hydrogen atom bonded to a carbon atom in a compound is replaced by another substituent. The site where substitution occurs means the site where the hydrogen atom is substituted. The site is not limited to any site where the hydrogen can be replaced by a substituent. If two or more substitutions occur, the two or more substituents may be the same or different.

[0067] In this specification, the substituent being "substituted" may be, for example, one selected from the group consisting of hydrogen, deuterium, C1 to C20 alkyl groups, C1 to C20 alkoxy groups, halogens, cyano groups, carboxyl groups, carbonyl groups, amine groups, C1 to C20 alkylamine groups, nitro groups, C1 to C20 alkylsilyl groups, C1 to C20 alkoxysilyl groups, C3 to C30 cycloalkylsilyl groups, C6 to C30 arylsilyl groups, C6 to C30 aryl groups, C6 to C30 arylamine groups, C5 to C30 heteroaryl groups, C6 to C30 arylphosphine oxide groups, C6 to C30 arylphosphinyl groups, C6 to C30 alkylphosphine oxides, C6 to C30 alkylsulfonyl groups, or any combination thereof, but the present invention is not limited thereto.

[0068] The following are examples of compounds used as electron donor molecules. [ka] TIFF2026065060000011.tif179130TIFF2026065060000012.tif160124

[0069] The following are examples of compounds used as electron acceptor molecules. [ka] TIFF2026065060000014.tif174139TIFF2026065060000015.tif183153

[0070] In one embodiment, the first excitation complex-forming compound may be an organic substance or an organometallic complex, and the excitation complex-forming moiety may be a derivative thereof. In one embodiment, the multifunctional compound may be any one of the compounds represented by the following structural formulas.

[0071] [ka] TIFF2026065060000017.tif187155TIFF2026065060000018.tif187149TIFF2026065060000019.tif185143TIFF2026065060000020.tif184137

[0072] The organic light-emitting diode can contain the multifunctional compound at a level higher than the normal dopant content. This means that the content of the light-emitting molecule can be higher than the dopant content. For example, the multifunctional compound may be at a level higher than the normal dopant content in order to increase the ratio of excited complex formation between the excited complex-forming molecule of the multifunctional compound and the second excited complex-forming compound. However, in this case, the excited complex-forming molecule of the multifunctional compound can efficiently suppress the concentration quenching phenomenon that occurs due to the interaction between light-emitting molecules, so even if the doping amount of the multifunctional compound increases, it is highly likely that the efficiency and color perception will not be significantly affected. The proportion of the multifunctional compound in the light-emitting layer can be, for example, in the range of 1 to 50 mol% of the total material constituting the light-emitting layer, and can be higher depending on the application.

[0073] In one embodiment, the multifunctional compound can be used as the excited complex-forming compound that forms the excited complex and as the excited complex-forming moiety of the multifunctional compound.

[0074] Specifically, when an electron-donating molecule is made into an excited complex-forming molecule and this molecule is bonded to a light-emitting molecule, the multifunctional compound formed in this way is called the first multifunctional compound, and when an electron-accepting molecule is made into an excited complex-forming molecule and this molecule is bonded to a light-emitting molecule, the multifunctional compound formed in this way is called the second multifunctional compound. Even if the light-emitting layer is composed only of the first and second multifunctional compounds, an excited complex can be formed between each electron-accepting molecule and electron-donating molecule, allowing energy to be transferred to the light-emitting molecule.

[0075] In this case, the aforementioned multifunctional compound becomes the first multifunctional compound, and the aforementioned excited complex-forming compound becomes the second multifunctional compound. At this time, depending on the mixing ratio of the first multifunctional compound and the second multifunctional compound, the content of either the first or second multifunctional compound may exceed 50 mol%. For example, the light-emitting layer may contain more than 50 mol% of the first multifunctional compound, and this is an example of a case where the content of the multifunctional compound exceeds 50 mol%, as described above.

[0076] To further enhance the luminescence efficiency of the light-emitting layer, phosphorescent material can be added to the light-emitting layer.

[0077] In one embodiment, the light-emitting layer may further include a phosphorescent material containing Pt or Ir.

[0078] The compounds represented by the structural formulas below are examples of organometallic complexes commonly used as phosphorescent substances. In the formulas below, R may be an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or the like. [ka]

[0079] To further improve the luminescence efficiency of the light-emitting layer, the light-emitting layer can contain additional delayed-fluorescence materials.

[0080] In one embodiment, the light-emitting layer may further contain a delayed fluorescent substance in which the energy difference between singlet and triplet states is 0.3 eV or more.

[0081] The compounds represented by the structural formulas below are examples of commonly used delayed fluorescent substances. Ar may be an alkyl group with 1 to 20 carbon atoms, an aryl group with 6 to 30 carbon atoms, etc. [ka]

[0082] The organic light-emitting diode may include one selected from the group consisting of a hole injection layer, a hole transport layer, an electron barrier layer, a hole barrier layer, an electron transport layer, an electron injection layer, and combinations thereof as the organic layer.

[0083] In one embodiment, the organic light-emitting diode may sequentially include an anode, a hole injection layer (HIL), a hole transport layer (HTL), a light-emitting layer (EML), an electron transport layer (ETL), and a cathode.

[0084] The organic light-emitting diode may be a tandem type organic light-emitting diode comprising a plurality of organic light-emitting units. Each organic light-emitting unit includes a light-emitting layer and may further include at least one organic layer. The organic layer may include one selected from the group consisting of a hole injection layer, a hole transport layer, an electron barrier layer, a hole barrier layer, an electron transport layer, an electron injection layer, and combinations thereof.

[0085] Multiple organic light-emitting units can be stacked sequentially, and a charge generation layer (CGL) may be included between each organic light-emitting unit. The charge generation layer is located between the organic light-emitting units and allows for the smooth distribution of charge to the light-emitting layer of each organic light-emitting unit.

[0086] The tandem type organic light-emitting diode includes at least one organic light-emitting unit which contains a light-emitting layer comprising the multifunctional compound. The light-emitting layer containing the multifunctional compound further includes, or does not include, an organic layer adjacent to one or both sides of the light-emitting layer. The light-emitting layer containing the multifunctional compound or the adjacent organic layer contains an excitation complex-forming compound. The multifunctional compound comprises an excited complex-forming molecule and a light-emitting molecule. The excited complex-forming moiety forms an excited complex with the excited complex-forming compound, The light-emitting moiety emits light upon receiving excitation energy transfer from the excited complex.

[0087] Detailed explanations regarding the multifunctional compound, the excitation complex-forming compound, and the like in the tandem-type organic light-emitting diode are as described above.

[0088] The following describes examples and comparative examples of the present invention. The following examples are merely one embodiment of the present invention, and the present invention is not limited to these examples. [Examples]

[0089] Synthesis Example 1 Compound 3, described below, was synthesized as a multifunctional compound. [ka]

[0090] Compound 1 is the aforementioned first excitation complex-forming compound, and Compound 2 is the aforementioned luminescent compound. These two compounds are chemically bonded to form a spiro structure, resulting in the synthesis of Compound 3 as a multifunctional compound. In the structural formula of Compound 3, the "compound 1 portion" corresponds to the excitation complex-forming molecule derived from Compound 1, and the "compound 2 portion" corresponds to the luminescent molecule derived from Compound 2. The multifunctional compound Compound 3 has a structure in which the excitation complex-forming molecule and the luminescent molecule are spiro-bonded via carbon.

[0091] [ka]

[0092] 3.95 g (10.0 mmol) of compound 1-1, 2.01 g (0.012 mol) of compound 1-2, 0.275 g (0.3 mmol) of tris(dibenzylideneacetone)dipalatium(0), 2.88 g (0.03 mol) of sodium-t-butoxide, 0.606 g (0.3 mmol) of tri-t-butylphosphine, and 60 ml of toluene were added to a round-bottom flask reactor and stirred under reflux for 2 hours. After the reaction was complete, the mixture was cooled to room temperature. The reaction solution was extracted with dichloromethane and water. The organic layer was separated, treated anhydrous with magnesium sulfate, and then concentrated under reduced pressure. The substance was separated and purified by column chromatography, and then recrystallized with dichloromethane and acetone to obtain (3.1 g, 36%). After cooling the reaction mixture to room temperature, cooled water was added, and the organic layer was extracted using ethyl acetate. The solvent of the extracted organic layer was dried over MgSO4 and then filtered. The filtrate was concentrated under reduced pressure and purified using silica gel column chromatography (DCM / Hexane). Subsequently, the compound 1-1 was recrystallized and purified in a DCM / Acetone mixed solvent to obtain 3.2 g of compound 1-1 in 60% yield. MS (MALDI-TOF) m / z: 481[M]+

[0093] [ka]

[0094] Starting material 2-1 was dissolved in 9.52 g (10.0 mmol) of t-butylbenzene (32 ml) and then cooled to 0°C. Under a nitrogen atmosphere, 8.0 mL (20.0 mmol) of 2.5 M n-butyllithium solution (in hexane) was added and the mixture was stirred at room temperature for 3 hours. After this, the reaction mixture was cooled again to 0°C, 1.90 mL (20.0 mmol) of boron tripromide was added, and the mixture was stirred at room temperature for 0.5 hours. The reaction mixture was cooled again to 0°C, 3.51 mL (20.0 mmol) of N,N-diisopropylethylamine was added, and the mixture was stirred at 60-70°C for 2 hours. The reaction mixture was cooled to room temperature, and the organic layer was extracted with ethyl acetate. The solvent of the extracted organic layer was dried over MgSO4 and then filtered. The filtrate was concentrated under reduced pressure and purified using silica gel column chromatography (DCM / Hexane). Subsequently, the compound 2 was purified by recrystallization in a DCM / acetone mixed solvent to obtain 1.05 g of compound 2 in a 12% yield. MS (MALDI-TOF) m / z: 880[M]+ NMR:δ H (400MHz;CDCl3;Me4Si)9.13(1H,s), 8.86-8.83(1H,m), 7.92-7.90(1H,m), 7.78(1H,d,J8.0), 7.73-7.64(4H,m), 7.44-7.27(8H,m), 7 .17‐6.86(11H,m), 6.80‐6.57(5H,m), 6.49(1H,d,J4.0), 6.37(1H,d,J8.0), 6.12(2H,t), 5.89(1H,d,J8.0), 2.36(3H,s), 0.96(9H,s)

[0095] [ka]

[0096] The procedure was carried out in the same manner as described above (synthesis of compound 2), except that compound 3-1 was used instead of compound 2-1 in the same molar ratio. Subsequently, 1.0 g of compound 3 was obtained in a 9% yield. MS (MALDI-TOF) m / z: 1046[M]+ NMR:δ H(400MHz;CDCl3;Me4Si)9.13(1H,s), 8.86-8.83(1H,m), 7.92-7.90(1H,m), 7.78(1H,d,J8.0), 7.73-7.64(6H,m), 7.44-7.27(11H,m), 7.17-6.86(13H,m), 6.80-6.57(5H,m), 6.49(1H,d,J4.0), 6.37(1H,d,J8.0), 6.12(2H,t), 5.89(1H,d,J8.0), 2.36(3H,s), 0.96(9H,s)

[0097] Evaluation Example 1 The energy transition phenomena of compounds 1, 2, and 3 were compared and confirmed, and an energy transition between moieties was observed in compound 3. Figure 3 shows the absorption and emission spectra measured for compounds 1, 2, and 3. Each sample was dissolved in toluene solution to a concentration of 2 micromoles and measured using a SHIMADZU RF5301PC and a SHIMADZU UV 2550.

[0098] Comparing the absorption spectra of compound 2 and compound 3, we can confirm that compound 3 shows an increase in absorption in the 300-350 nm region, which is due to absorption by the excited complex-forming molecule of compound 3. The absorption rate of compound 3 at 330 nm increased by approximately twofold compared to compound 2. In compound 3, a multifunctional compound, the phenomenon of energy transfer from the excited complex-forming molecule to the luminescent molecule can be confirmed through the emission spectra of the two substances. When compound 2 and compound 3 were excited to 330 nm, the luminescence of the luminescent molecule of compound 3 increased by approximately 1.8 times compared to compound 2, and the emission spectrum of the excited complex-forming molecule completely disappeared. Through this, we can clearly confirm that the energy transfer phenomenon explained in Figure 1 was realized.

[0099] Through this evaluation example 1, we confirmed that energy transfer occurs efficiently when the distance between the energy donor (first excitation complex-forming compound) and the energy acceptor (luminescent compound) is made very small through chemical bonding (i.e., through chemical bonding).

[0100] Examples 1-4 and Comparative Examples 1-4 The following compounds were prepared. [ka]

[0101] Compound A can form an excited complex with compound 1. [ka]

[0102] <Fabrication of Organic Light-Emitting Diodes> The ITO surface was treated with UV ozone at atmospheric pressure for 3 minutes. 10- 7 The elements were processed in Torr's vacuum chamber using the following procedure.

[0103] Comparative Example 1 HATCN was deposited as the hole injection material to a thickness of 50 Å. Compound B was deposited as a hole transport material to a thickness of 1000 Å. Compound 1 was deposited on the electron blocking layer to a thickness of 50 Å. Compound A was deposited onto the light-emitting layer to a thickness of 250 Å. Compounds C and LiQ were deposited on the electron transport layer in a 1:1 ratio to a thickness of 300 Å. The compound LiQ was deposited on the electron injection layer to a thickness of 10 Å. Al was deposited onto the electrode to a thickness of 500 Å.

[0104] Comparative Example 2 An organic light-emitting diode was fabricated in the same manner as in Comparative Example 1, except that the electron blocking layer was doped with 5 mol% of compound 2 and the light-emitting layer was doped with 5 mol% of compound 2.

[0105] Comparative Example 3 An organic light-emitting diode was fabricated in the same manner as in Comparative Example 1, except that the electron blocking layer was doped with 5 mol% of compound 2 and the light-emitting layer was doped with 10 mol% of compound 2.

[0106] Comparative Example 4 An organic light-emitting diode was fabricated in the same manner as in Comparative Example 1, except that the electron blocking layer was doped with 5 mol% of compound 2 and the light-emitting layer was doped with 15 mol% of compound 2.

[0107] Example 1 An organic light-emitting diode was fabricated in the same manner as in Comparative Example 1, except that the electron blocking layer was doped with 5 mol% of compound 3 and the light-emitting layer was doped with 5 mol% of compound 3.

[0108] Example 2 An organic light-emitting diode was fabricated in the same manner as in Comparative Example 1, except that the electron blocking layer was doped with 5 mol% of compound 3 and the light-emitting layer was doped with 10 mol% of compound 3.

[0109] Example 3 An organic light-emitting diode was fabricated in the same manner as in Comparative Example 1, except that the electron blocking layer was doped with 5 mol% of compound 3 and the light-emitting layer was doped with 15 mol% of compound 1.

[0110] Example 4 An organic light-emitting diode was fabricated in the same manner as in Comparative Example 1, except that the electron blocking layer was doped with 5 mol% of compound 3 and the light-emitting layer was doped with 20 mol% of compound 1.

[0111] Evaluation Example 2 Figure 4 shows the emission spectrum indicating that excited complex formation does not readily occur between compound A and compound 2a, but does occur between compound A and compound 1. In this case, compound A and compound 2a, and compound A and compound 1 were mixed in a 6:4 molar ratio, dissolved in toluene solution, and a film was fabricated using a casting method. The emission spectrum was then obtained by exciting the film with 330 nm light. The absence of a new wavelength peak between compound A and compound 2a indicates that an excited complex is not formed. In the mixed film of compound A and compound 1, the peak of compound 1 disappears, and a new peak in the 490 nm region is observed, indicating that an excited complex is formed.

[0112] The portion of compound 2 shown below has the structure of compound 2a; therefore, compound 2 does not form an excited complex with compound A. [ka]

[0113] On the other hand, compound 3 forms an excited complex with compound A by replacing the compound 2a portion of compound 2 with a moiety derived from compound 1 (the portion of compound 1, corresponding to the excited complex-forming moiety).

[0114] In Comparative Examples 2-4, where the device was fabricated using compound 2, no excitation complex was formed, resulting in no increase in efficiency. In Examples 1-4, where the device was fabricated using compound 3, an excitation complex was formed, resulting in an increase in efficiency. This can be confirmed by the evaluation results for the devices described below.

[0115] Evaluation Example 3 The organic light-emitting diodes fabricated in Examples 1-4 and Comparative Examples 1-4 were evaluated for their device characteristics at room temperature using a current supply source (KEITHLEY) and a photometer (PR 650). Table 1 below shows the driving voltage (V), maximum EQE (external quantum efficiency), and CIE chromaticity coordinate measurement results for the organic light-emitting diodes of Examples 1-4 and Comparative Examples 1-4.

[0116] [Table 1]

[0117] As can be seen in Table 1 above, in the case of organic light-emitting diodes using the multifunctional compounds of Examples 1 to 4, it can be confirmed that they exhibit high quantum efficiency and color stability due to increased doping concentration.

[0118] As demonstrated in the examples above, it is obvious that the present invention is applicable not only to organic light-emitting diodes manufactured by a vapor deposition process, but also to organic light-emitting diodes manufactured by a solution process.

[0119] As described above, the present invention has been explained with reference to the illustrative drawings, but the present invention is not limited by the embodiments and drawings disclosed herein, and it is obvious that various modifications can be made by an ordinary person within the scope of the technical concept of the present invention. At the same time, even if the effects of the configuration of the present invention are not explicitly described while describing embodiments of the present invention, it is natural that predictable effects from the relevant configuration should also be recognized.

Claims

1. It includes a first electrode, a second electrode, and a light-emitting layer located between the first electrode and the second electrode. The light-emitting layer further includes, or does not include, an organic layer adjacent to one or both of the aforementioned surfaces. The light-emitting layer contains a multifunctional compound, The light-emitting layer or the adjacent organic layer contains an excitation complex-forming compound. The multifunctional compound comprises an excited complex-forming molecule and a light-emitting molecule. The excited complex-forming moiety forms an excited complex with the excited complex-forming compound, The light-emitting moiety emits light upon receiving excitation energy transfer from the excited complex. Organic light-emitting diode.

2. The excited complex-forming compound is derived from a compound capable of forming an excited complex with the excited complex-forming compound. The organic light-emitting diode according to claim 1.

3. The HOMO energy of the excited complex-forming moiety is E(1) HOMO , LUMO energy E(1) LUMO The HOMO energy of the excited complex-forming compound is E(2) HOMO , LUMO energy E(2) LUMO When this is the case, the following conditions 1 or 2 must be met, <Condition 1> │E(1) HOMO │≦│E(2) HOMO │and │E(1) LUMO │≦│E(2) LUMO That is the case. <Condition 2> │E(1) HOMO │≧│E(2) HOMO │where │E(1) LUMO │≧│E(2) LUMO │is ru. When the excited complex-forming moiety and the excited complex-forming compound form an excited complex, and the maximum emission wavelength energy of the excited complex energy is E(ex), then the following conditions 3 or 4 are satisfied. <Condition 3> │E(1) HOMO │‐│E(2) LUMO │≧E(ex) <Condition 4> │E(2) HOMO │‐│E(1) LUMO │≧E(ex) The organic light-emitting diode according to claim 1.

4. The aforementioned light-emitting moisture was derived from the light-emitting material. The organic light-emitting diode according to claim 1.

5. The aforementioned light-emitting moisture has a conjugated structure with a quantum efficiency of 50% or more in the visible light wavelength range of 400 nm to 700 nm. The organic light-emitting diode according to claim 1.

6. The aforementioned light-emitting moisture has a conjugated structure with a quantum efficiency of 10% or more in the near-infrared wavelength region of 700 nm to 2200 nm. The organic light-emitting diode according to claim 1.

7. The emission mechanism of the aforementioned luminescent moiety includes fluorescence, where light is emitted from a singlet state; phosphorescence, where light is emitted from a triplet state; and delayed fluorescence, where energy is transferred from the triplet state to the singlet state to emit light. The organic light-emitting diode according to claim 1.

8. The band gap energy of the excited complex-forming moiety is greater than the band gap energy of the luminescent moiety. The organic light-emitting diode according to claim 1.

9. In the aforementioned multifunctional compound, the excited complex-forming moisture and the light-emitting moisture are linked by a chemical bond. The organic light-emitting diode according to claim 1.

10. The aforementioned multifunctional compound is substituted with deuterium, The organic light-emitting diode according to claim 1.

11. The aforementioned chemical bond is a single bond, double bond, triple bond, or coordinate bond. The organic light-emitting diode according to claim 9.

12. The aforementioned chemical bonds are linked by arylene having 6 to 20 carbon atoms, carbon atoms, oxygen atoms, nitrogen atoms, silicone atoms, Ge atoms, S atoms, or P atoms. The organic light-emitting diode according to claim 9.

13. The excited complex-forming moisture and the light-emitting moisture are connected by a spiro structure via carbon, silicone, or Ge. The organic light-emitting diode according to claim 9.

14. The luminescent molecule is derived from the luminescent compound before the chemical bonding, In the aforementioned multifunctional compound, the excited complex-forming moisture linked by the chemical bond does not cause the band gap energy of the luminescent moisture to change by 0.2 eV or more compared to the band gap energy of the luminescent compound before the chemical bond was formed. The organic light-emitting diode according to claim 9.

15. The band gap energy of the excited complex-forming moisture is 1 eV to 4.7 eV, and the band gap energy of the luminescent moisture is 0.5 eV to 3.5 eV. The difference in band gap energy between the excited complex-forming moisture and the luminescent moisture is within 2 eV. The organic light-emitting diode according to claim 1.

16. The difference between the HOMO energy level of the excited complex-forming moiety and the HOMO energy level of the luminescent moiety is within 1.9 eV. The difference in energy levels between the LUMO energy of the excited complex-forming moisture and the LUMO energy of the light-emitting moisture is within 1.9 eV. The organic light-emitting diode according to claim 1.

17. The aforementioned excited complex-forming moiety is derived from an electron-donating substance represented by the following chemical formula 1, or from a substance with one electron acceptor in the structure represented by the following chemical formula 2. The organic light-emitting diode according to claim 1. 【Chemistry 1】 In the aforementioned chemical formula 1, Each Ar may independently be a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the two Ars can be linked together to form a fusion ring having 12 to 30 carbon atoms. In the aforementioned chemical formula 1, at least one hydrogen atom is either substituted with deuterium or left unsubstituted. 【Chemistry 2】 In the aforementioned chemical formula 2, X may be nitrogen or carbon. n and m are integers from 0 to 6, except that if X is nitrogen, n+m is an integer from 1 to 3, and if X is carbon, n+m is an integer from 1 to 6. Each Ar may independently be a substituted or unsubstituted C6 to C30 aryl group, a substituted or unsubstituted C5 to C30 heteroaryl group, a substituted or unsubstituted C6 to C30 arylsilyl group, a substituted or unsubstituted C6 to C30 aryloxy group, a substituted or unsubstituted C1 to C20 alkylsilyl group, a substituted or unsubstituted C1 to C20 alkyl group, or a substituted or unsubstituted C6 to C30 aryl group containing phosphine or phosphine oxide, and the two Ar groups can be linked to form a C12 to C30 fusion ring. In the aforementioned chemical formula 2, at least one hydrogen atom is either substituted for deuterium or left unsubstituted.

18. The aforementioned excited complex-forming moiety is derived from an organic or organometallic complex. The organic light-emitting diode according to claim 1.

19. The aforementioned light-emitting molecule contains boron and has a conjugated structure. The organic light-emitting diode according to claim 1.

20. The aforementioned light-emitting material includes metal. The organic light-emitting diode according to claim 1.

21. The light-emitting layer further comprises a phosphorescent material containing Ir or Pt. The organic light-emitting diode according to claim 1.

22. The light-emitting layer further contains a delayed fluorescent material in which the energy difference between singlet and triplet states is 0.3 eV or more. The organic light-emitting diode according to claim 1.

23. The aforementioned organic light-emitting diode is a tandem type organic light-emitting diode including a plurality of organic light-emitting units, At least one of the plurality of organic light-emitting units includes the light-emitting layer. The organic light-emitting diode according to claim 1.

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