An organic electroluminescent device having double light-emitting layers

Abstract

An organic electroluminescent device with double light-emitting layers, having a cathode and an anode and an organic light-emitting layer sandwiched between the two electrodes, wherein the organic light-emitting layer comprises a first and a second organic light-emitting layer. The first organic light-emitting layer comprises organic molecule I and organic molecule II, and the second organic light-emitting layer comprises organic molecule III and organic molecule IV. Organic molecules I and III are host materials, which can be the same or different, organic molecule II is a sensitizing material, and organic molecule IV is a light-emitting material.

Description

Technical Field

[0001] This invention relates to the field of organic electroluminescence technology, and in particular to a highly efficient and stable blue light device. Background Technology

[0002] Organic light-emitting diodes (OLEDs) are devices that convert electrical energy into light energy using organic materials. OLEDs offer numerous advantages, including being ultra-lightweight, ultra-thin, having high pixel count, being foldable, having a wide viewing angle, high contrast, and being energy-efficient. An OLED structure consists of a cathode, an organic functional layer, and an anode. The organic functional layer includes a hole injection layer, a hole transport layer, an emissive layer, an electron transport layer, and an electron injection layer. The light emission process of an OLED achieves electroluminescence through the injection, transport, and recombination of charge carriers. Specifically, after an external electric field is applied to the OLED, holes are injected from the anode side through the hole injection layer, and electrons are injected from the cathode side through the electron injection layer. After transport through the hole transport layer and the electron transport layer, the two electrons meet in the emissive layer to form excitons. Under the influence of the electric field, the excitons diffuse and migrate in the emissive layer, relaxing from the excited state to the ground state on the luminescent material and emitting light through radiative transitions.

[0003] With the development of OLED technology, solutions for red and green light devices have become increasingly mature. The current bottleneck remains achieving efficient and stable blue light. Using large blue light pixels and small red and green light pixels on production lines to improve screen blue light stability is clearly a compromise. This leads to high power consumption, low brightness, and short lifespan. The optimal solution is still to improve the efficiency and stability of blue light devices to match the efficiency and lifespan of red and green light. However, researchers and industry have yet to achieve stable blue light using phosphorescence and TADF, so fluorescent devices remain the final choice. Therefore, finding efficient and stable blue light has always been a goal for those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of improving the efficiency, color purity, and lifespan of existing blue OLEDs. In view of this, this invention provides a novel organic electroluminescent device, which is realized through the following blue OLED. Specifically, this invention provides:

[0005] 1) An organic electroluminescent device having a cathode, an anode, and at least two organic layers comprising a dual light-emitting layer sandwiched between the two electrodes, the dual light-emitting layer comprising a first and a second organic light-emitting layer, each organic light-emitting layer having at least one different material compared to the other light-emitting layer.

[0006] The first organic light-emitting layer comprises organic molecule I and organic molecule II, and the second organic light-emitting layer comprises organic molecule III and organic molecule IV. Organic molecule I and III are the host materials, and may be of the same or different types. Organic molecule II is the sensitizing material, and organic molecule IV is the light-emitting material.

[0007] Formula (A):E S1 (I)>E S1 (II)

[0008] Formula (B):E S1 (III) > E S1 (IV)

[0009] Formula (C):E S1 (II) > E S1 (IV)

[0010] In the above formula, E S1 (I) represents the lowest excited singlet state energy level of the organic molecule I, E S1 (II) represents the lowest excited singlet state energy level of the organic molecule II, E S1 (III) represents the lowest excited singlet state energy level of the organic molecule III, E S1 (IV) represents the lowest excited singlet energy level of the organic molecule IV;

[0011] Among them, the fluorescence radiative rate of organic molecule II is in the range of 5. 10 8 s -1 ~5 10 10 s -1 Between these values, the full width at half maximum (FWHM) of organic molecules IV is between 5 and 40 nm.

[0012] 2) According to the organic electroluminescent device described in 1), the organic molecule III emits blue light with a peak emission value between 440-490 nm.

[0013] 3) The organic electroluminescent device according to 1) or 2), wherein the thickness of the first organic light-emitting layer is 1~20 nm, and the mass content of organic molecule II is between 0.5 wt% and 20 wt%; the thickness of the second organic light-emitting layer is 1~20 nm, and the mass content of organic molecule IV is between 0.5 wt% and 20 wt%.

[0014] 4) The organic electroluminescent device according to 1) or 2), wherein the first organic light-emitting layer and the second organic light-emitting layer have no sequential order, and the first organic light-emitting layer can be either the side closer to the cathode or the side closer to the anode.

[0015] 5) The organic electroluminescent device according to 1) or 2), wherein the organic molecule I and organic molecule II of the light-emitting layer have molecular structures as shown in general formulas 1 to 6:

[0016]

[0017] Ar 1 and Ar 2 Each can be independently represented as one of the following: aryl group with 6-50 cyclic carbon atoms (substituted or unsubstituted), heteroaryl group with 5-50 cyclic atoms (substituted or unsubstituted), arylamine group with 6-50 cyclic atoms (substituted or unsubstituted), or heteroarylamine group with 3-50 cyclic atoms (substituted or unsubstituted); Ar 1 and Ar 2 Same or different;

[0018] R(R 1 ~R 10 Ra) represents one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 carbon atoms, substituted or unsubstituted heteroaryl group with 5 to 50 carbon atoms, substituted or unsubstituted arylamino group with 6 to 50 carbon atoms, and substituted or unsubstituted heteroarylamino group with 3 to 50 carbon atoms; and R 1 ~R 10 Two adjacent groups can bond together with the adjacent benzene ring to form one of the following: substituted or unsubstituted aryl group with 6-50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5-50 cyclic atoms, and at least one hydrogen atom in the formed ring can be replaced by any one of the following: halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1-20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3-20 cyclic carbon atoms, substituted or unsubstituted alkoxy group with 1-20 carbon atoms, substituted or unsubstituted aralkyl group with 7-30 carbon atoms, substituted or unsubstituted aryloxy group with 6-30 cyclic carbon atoms, substituted or unsubstituted aryl group with 6-50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5-50 cyclic atoms, substituted or unsubstituted arylamino group with 6-50 cyclic atoms, or substituted or unsubstituted heteroarylamino group with 3-50 cyclic atoms.

[0019] m is a positive integer, ranging from 0 to 5;

[0020] n is a positive integer, ranging from 1 to 3.

[0021] 6) The organic electroluminescent device according to 1) or 2), wherein the organic molecule II of the first light-emitting layer has a molecular structure as shown in general formulas 7-9:

[0022]

[0023] X represents O, S, and NR. 11 Or R 12 CR 13 ;

[0024] Ar 1 Ar 2 Ar 3 Each can be independently represented as one of the following: aryl group with 6-50 cyclic carbon atoms (substituted or unsubstituted), heteroaryl group with 5-50 cyclic atoms (substituted or unsubstituted), arylamine group with 6-50 cyclic atoms (substituted or unsubstituted), or heteroarylamine group with 3-50 cyclic atoms (substituted or unsubstituted); Ar 1 Ar 2 Ar 3 Same or different;

[0025] R(R 1 ~R 13 ) represents one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 carbon atoms, substituted or unsubstituted heteroaryl group with 5 to 50 carbon atoms, substituted or unsubstituted arylamino group with 6 to 50 carbon atoms, and substituted or unsubstituted heteroarylamino group with 3 to 50 carbon atoms; and R 1 ~R 10 Two adjacent groups can bond together with the adjacent benzene ring to form one of the following: aryl group with 6-50 substituted or unsubstituted cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted cyclic atoms, and at least one hydrogen atom in the formed ring can be replaced by any one of the following: halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1-20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3-20 carbon atoms, substituted or unsubstituted alkoxy group with 1-20 carbon atoms, substituted or unsubstituted aralkyl group with 7-30 carbon atoms, substituted or unsubstituted aryloxy group with 6-30 carbon atoms, substituted or unsubstituted aryl group with 6-50 cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted arylamino group with 6-50 substituted or unsubstituted arylamino group with 3-50 substituted or unsubstituted cyclic atoms.

[0026] 7) The organic electroluminescent device according to 1) or 2), wherein the organic molecule IV of the light-emitting layer has a molecular structure as shown in general formulas 10-14:

[0027]

[0028] Ar 1 and Ar 2 Each and every one of the following can be independently represented: aryl group with 6-50 carbon atoms (substituted or unsubstituted), heteroaryl group with 5-50 cyclic atoms (substituted or unsubstituted), arylamine group with 6-50 cyclic atoms (substituted or unsubstituted), or heteroarylamine group with 3-50 cyclic atoms (substituted or unsubstituted); Ar 1 and Ar 2 Same or different;

[0029] R(R 1 ~R 16 Each of the following groups independently represents one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5 to 50 cyclic atoms, substituted or unsubstituted arylamino group with 6 to 50 cyclic atoms, and substituted or unsubstituted heteroarylamino group with 3 to 50 cyclic atoms; and R 1 ~R 10 Two adjacent groups can bond together with the adjacent benzene ring to form one of the following: aryl group with 6-50 substituted or unsubstituted cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted cyclic atoms, and at least one hydrogen atom in the formed ring can be replaced by any one of the following: halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1-20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3-20 carbon atoms, substituted or unsubstituted alkoxy group with 1-20 carbon atoms, substituted or unsubstituted aralkyl group with 7-30 carbon atoms, substituted or unsubstituted aryloxy group with 6-30 carbon atoms, substituted or unsubstituted aryl group with 6-50 cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted arylamino group with 6-50 substituted or unsubstituted arylamino group with 3-50 substituted or unsubstituted cyclic atoms.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] Because OLEDs operate at high current density in their emissive layer, the emissive layer is always in a state of high exciton concentration. High exciton concentration leads to various side reactions, such as singlet-singlet annihilation and singlet-polaron annihilation, resulting in reduced device efficiency, accelerated aging, and decreased device stability. Increasing the radiative rate of the luminescent molecules can significantly improve exciton utilization, ensuring the OLED maintains a low exciton concentration even under high current density operation, fundamentally reducing the aforementioned side reactions and thus improving device efficiency and stability. However, currently, molecules with ultra-high radiative rates have very broad spectra, and using only these as guest molecules obviously cannot achieve ideal color purity. Therefore, this invention introduces a dual emissive layer. The first emissive layer is doped with fluorescent molecules with ultra-high radiative rates as sensitizers, and the second emissive layer is doped with fluorescent molecules with narrow-spectrum emission as guest molecules. By selecting host molecules, sensitizers, and guest molecules at appropriate energy levels and adjusting the positions and thicknesses of the first and second emissive layers, exciton recombination is achieved in the first emissive layer but not in the second. The energy of the sensitizer molecules is then transferred to the guest molecules through the FRET process, ultimately achieving narrow-spectrum emission. In this invention, the exciton utilization rate is greatly improved by introducing sensitizing molecules with ultra-high radiation rates, thereby reducing the exciton density of the OLED light-emitting layer during operation and improving the efficiency and stability of the device. Furthermore, the device spectrum is narrowed by guest molecules with narrow-spectrum emission, resulting in ideal color purity. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the structure of an organic electroluminescent device. Detailed Implementation

[0033] This invention provides a method for simultaneously improving device efficiency, color purity, and lifespan. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. The specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0034] In the embodiments of this invention, the fluorescence radiative rate and full width at half maximum (FWHM) of the organic materials play a crucial role. These concepts are described in detail below.

[0035] The fluorescence emission rate is the rate constant (k) for a substance to transition from an excited state back to the ground state and emit fluorescence, which can be expressed by:

[0036] Equation (B): k=Ф / τ

[0037] The calculation is performed, where Ф is the fluorescence quantum yield of the substance, defined as the ratio of the number of fluorescence photons emitted after the substance absorbs light to the number of photons of the absorbed excitation light. τ is the fluorescence lifetime of the substance, defined as the time required for the fluorescence intensity of the substance to drop to 1 / e of the maximum fluorescence intensity I0 at excitation after the excitation light is removed. Both the fluorescence quantum yield and lifetime can be measured using steady-state or transient fluorescence spectrometry.

[0038] Half-width at half-maximum (HWHM) is the width of a spectral peak at half its height. It is the distance between two points where a straight line drawn through the midpoint of the peak height intersects the two sides of the peak.

[0039] The organic electroluminescent blue light device of the present invention comprises an anode, a cathode, and an organic layer between the anode and the cathode. The organic layer includes at least a light-emitting layer, and the present invention has distinctive features in the composition of the light-emitting layer.

[0040] The organic layer can consist solely of a light-emitting layer, or it can have one or more organic layers in addition to the light-emitting layer. Other organic layers can be hole injection layers, hole transport layers, electron blocking layers, electron transport layers, electron injection layers, etc. Specific device structures are as follows: Figure 1 As shown in the diagram. 1 represents the substrate, 2 represents the anode, 3 represents the hole injection layer, 4 represents the hole transport layer, 5 represents the electron blocking layer, 6 represents the light-emitting layer, 7 represents the hole blocking layer, 8 represents the electron transport layer, 9 represents the electron injection layer, and 10 represents the cathode. The following provides a detailed description of each layer.

[0041] [Emitting Layer]

[0042] The light-emitting layer is a layer in which holes and electrons injected from the anode and cathode combine to generate excitons and emit light.

[0043] This invention comprises first and second organic light-emitting layers. The first organic light-emitting layer comprises organic molecule I and organic molecule II, and the second organic light-emitting layer comprises organic molecule III and organic molecule IV. Organic molecule I and III are the host materials, and may be of the same or different types. Organic molecule II is a sensitizing material, and organic molecule IV is a light-emitting material.

[0044] Formula (A):E S1 (I)>E S1 (II)

[0045] Formula (B):E S1 (III) > E S1 (IV)

[0046] Formula (C):E S1 (II) > E S1 (IV)

[0047] In the above formula, E S1(I) represents the lowest excited singlet state energy level of the organic molecule I, E S1 (II) represents the lowest excited singlet state energy level of the organic molecule II, E S1 (III) represents the lowest excited singlet state energy level of the organic molecule III, E S1 (IV) represents the lowest excited singlet energy level of the organic molecule IV.

[0048] Among them, the fluorescence radiative rate of organic molecule II in the first luminescent layer is 5 10 8 s -1 ~5 10 10 s -1 In this way, the excitons of the emitting layer can be quickly consumed to achieve high device efficiency. The half-width of the organic molecule IV in the second emitting layer is between 5 and 40 nm. The energy of the organic molecule II is converted into the luminescence of the organic molecule IV through the Föster energy resonance transfer process, thereby narrowing the spectrum and improving the color purity of the device.

[0049] As a preferred host material, unless otherwise specified, molecules represented by the following general formulas 1 to 6 may be preferred as organic molecule I.

[0050]

[0051] Ar 1 and Ar 2 Each can be independently represented as one of the following: aryl group with 6-50 cyclic carbon atoms (substituted or unsubstituted), heteroaryl group with 5-50 cyclic atoms (substituted or unsubstituted), arylamine group with 6-50 cyclic atoms (substituted or unsubstituted), or heteroarylamine group with 3-50 cyclic atoms (substituted or unsubstituted); Ar 1 and Ar 2 Same or different;

[0052] R(R 1 ~R 10 Ra) represents one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 carbon atoms, substituted or unsubstituted heteroaryl group with 5 to 50 carbon atoms, substituted or unsubstituted arylamino group with 6 to 50 carbon atoms, and substituted or unsubstituted heteroarylamino group with 3 to 50 carbon atoms; and R 1 ~R 10Two adjacent groups can bond together with the adjacent benzene ring to form one of the following: substituted or unsubstituted aryl group with 6-50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5-50 cyclic atoms, and at least one hydrogen atom in the formed ring can be replaced by any one of the following: halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1-20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3-20 cyclic carbon atoms, substituted or unsubstituted alkoxy group with 1-20 carbon atoms, substituted or unsubstituted aralkyl group with 7-30 carbon atoms, substituted or unsubstituted aryloxy group with 6-30 cyclic carbon atoms, substituted or unsubstituted aryl group with 6-50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5-50 cyclic atoms, substituted or unsubstituted arylamino group with 6-50 cyclic atoms, or substituted or unsubstituted heteroarylamino group with 3-50 cyclic atoms.

[0053] m is a positive integer, ranging from 0 to 5;

[0054] n is a positive integer, ranging from 1 to 3;

[0055] Hereinafter, specific examples of molecules represented by general formulas 1 to 6 are shown. However, the molecules represented by general formulas 1 to 6 that can be used in this invention should not be limited to these specific examples.

[0056]

[0057]

[0058]

[0059]

[0060]

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[0070]

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[0090]

[0091]

[0092]

[0093] As a preferred sensitizing material, unless otherwise specified, molecules represented by the following general formulas 7 to 9 may be preferred as organic molecule II.

[0094]

[0095] X represents O, S, and NR. 11 Or R 12 CR 13 ;

[0096] Ar 1 Ar 2 Ar 3 Each is independently represented as one of the following: a substituted or unsubstituted aryl group with 6-50 carbon atoms in the cyclic ring, or a substituted or unsubstituted heteroaryl group with 5-50 cyclic atoms; Ar 1 Ar 2 Ar 3 Same or different;

[0097] R(R 1 ~R 13 () represents one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 carbon atoms, and substituted or unsubstituted heteroaryl group with 5 to 50 carbon atoms;

[0098] The following examples illustrate specific examples of molecules represented by general formulas 7-9. However, the molecules represented by general formulas 7-9 that can be used in this invention should not be limited to these specific examples.

[0099]

[0100]

[0101]

[0102]

[0103]

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[0125]

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[0127]

[0128]

[0129] As a preferred luminescent material, unless otherwise specified, molecules represented by the following general formulas 10 to 14 can preferably be used as organic molecules IV.

[0130]

[0131] Ar 1 and Ar 2 Each and every one of the following, independently representing aryl groups with 6-50 carbon atoms in a cyclic ring (substituted or unsubstituted), or heteroaryl groups with 5-50 carbon atoms in a cyclic ring (substituted or unsubstituted); Ar 1 and Ar 2 Same or different;

[0132] R(R 1 ~R 16 The following can be independently represented: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 cyclic atoms, or substituted or unsubstituted heteroaryl group with 5 to 50 cyclic atoms.

[0133] The following examples illustrate specific examples of molecules represented by general formulas 10-14. However, the molecules represented by general formulas 10-14 that can be used in this invention should not be limited to these specific examples.

[0134]

[0135]

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[0166]

[0167] [Substrate]

[0168] The OLED device of the present invention is supported by a substrate, which can be made of glass, transparent plastic, quartz, silicon, etc.

[0169] [anode]

[0170] Metals, alloys, and conductive molecules with a high work function (above 4 eV) can be used as the anode electrode material, such as metals like Au, CuI, indium tin oxide (ITO), SnO2, and ZnO, which are conductive and transparent materials. Alternatively, transparent amorphous materials such as IDIXO (In2O3-ZnO) can also be used.

[0171] [cathode]

[0172] Cathodes using metals, alloys, and conductive molecules with low work functions (below 4 eV) as electrode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper alloys, magnesium / silver alloys, magnesium / aluminum alloys, magnesium / indium alloys, aluminum / alumina (Al2O3) mixtures, indium, lithium / aluminum mixtures, and rare earth metals.

[0173] [Injection Layer]

[0174] The injection layer is a functional layer sandwiched between the electrode and the organic layer. It assists in the injection of holes from the anode or electrons from the cathode into the organic layer, thereby reducing the driving voltage and increasing the luminous brightness.

[0175] [Blocking Layer]

[0176] The blocking layer is a functional layer that blocks the diffusion of charge carriers (electrons or holes) and / or excitons from the light-emitting layer to the outside of the light-emitting layer, while simultaneously transporting charge carriers (electrons or holes).

[0177] [Cavity barrier]

[0178] The hole blocking layer serves the dual purpose of transporting electrons and blocking holes from entering the electron transport layer, thereby increasing the probability of exciton generation in the luminescent layer.

[0179] [Electron blocking layer]

[0180] The electron blocking layer serves both to transport holes and to block electrons from entering the hole transport layer, thereby increasing the probability of exciton generation in the luminescent layer.

[0181] Hole transport layer

[0182] The hole transport layer has the function of either hole injection or transport, or electron blocking, and can be either organic or inorganic, and can be a single layer or multiple layers.

[0183] [Electron transport layer]

[0184] The electron transport layer has the function of either electron injection or transport, or hole blocking, and can be either organic or inorganic, and can be a single layer or multiple layers.

[0185] Hereinafter, preferred molecules that can be used to fabricate devices are specifically illustrated, but the materials that can be used in this invention are not limited to the illustrated molecules. Furthermore, even molecules illustrated as materials with specific functions can be used as materials with other functions.

[0186] First, a list of preferred molecules that can be used as hole injection materials is provided.

[0187]

[0188] Secondly, a list of preferred molecules that can be used as hole transport materials is provided.

[0189]

[0190]

[0191]

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[0197] Secondly, a list of preferred molecules that can be used as electron blocking materials is provided.

[0198]

[0199]

[0200] Secondly, a list of preferred molecules that can be used as hole-blocking materials is provided.

[0201]

[0202] Secondly, a list of preferred molecules that can be used as electron transport materials is provided.

[0203]

[0204]

[0205]

[0206]

[0207]

[0208] Secondly, a list of preferred molecules that can be used as electron injection materials is provided.

[0209]

[0210] The organic electroluminescent element of this invention can be applied to any of the following: a single device, an array device, and a matrix device. The blue OLED of this invention can be applied to a variety of uses, such as manufacturing organic electroluminescent displays, lighting, or backlighting devices.

[0211] Example

[0212] The following examples further illustrate the features of the present invention. The materials, processing methods, and processing order shown below can be appropriately modified without departing from the purpose of the present invention. The scope of the present invention is not limited by the specific examples shown below.

[0213] The luminescence performance was tested using the following equipment: steady-state fluorescence spectrometer (manufactured by Horiba: PTI QM40), transient fluorescence testing system (manufactured by Horiba: deltaflex-1), power meter (manufactured by Keithley: 2400 Series), luminance meter (manufactured by Beijing Normal University Optoelectronic Instrument Factory: ST-86LA), fiber optic spectrometer (manufactured by Avantes: UL2048CL-EVO-RS), and OLED aging lifetime tester (manufactured by Shanghai University: ZJLS-4).

[0214] The fluorescence emission rates and full width at half maximum (FWHM) of the molecules used in the examples and comparative examples were determined by the following method.

[0215] Fluorescence radiative rate: The molecule was dissolved in toluene solution at a concentration of 5.0 × 10⁻⁶. -5 The fluorescence quantum yield Ф of the sample was determined at room temperature using a QM40 quantum yield assay at a concentration of mol / L, with a xenon lamp as the excitation source. The fluorescence lifetime τ of the sample was then determined at room temperature using a deltaflex-1 excitation system at a wavelength of 370 nm and a full width at half maximum (FWHM) of 50 ps. The fluorescence radiative rate k of the molecule was calculated using equation (B).

[0216] Half-peak width: The molecule was dissolved in toluene solution at a concentration of 5.0 × 10⁻⁶. -5 The fluorescence spectrum of the sample was measured at room temperature using a QM40 excitation source, with a concentration of mol / L and an excitation source of xenon lamp. The vertical axis of the fluorescence spectrum represents the luminescence intensity, and the horizontal axis represents the wavelength. A straight line parallel to the horizontal axis was drawn through the midpoint of the peak height of the curve. The difference between the two points where this straight line intersects the curve is the half-width at half-maximum (WHM).

[0217] The device fabrication process is as follows: The substrate with the anode material is ultrasonically treated in a cleaning agent, rinsed with deionized water, baked in a clean environment until all moisture is removed, and then cleaned with ultraviolet light and ozone. The substrate is then placed in a vacuum evaporation chamber at a vacuum degree of 5.0 × 10⁻⁶. -5Under Pa conditions, functional layers were deposited on a glass substrate with indium tin oxide (ITO) as the anode. First, a 10 nm hole injection layer was deposited on the ITO, followed by a 40 nm hole transport layer and a 5 nm electron blocking layer. The host and guest molecules were co-deposited from different evaporation sources to form the second emitting layer, and then the host and sensitized molecules were co-deposited to form the first emitting layer. Next, a 5 nm hole blocking layer and a 30 nm electron transport layer were deposited sequentially. Finally, a 1 nm electron injection layer and a 100 nm cathode were deposited to obtain the organic light-emitting device.

[0218] The device embodiments and comparative examples of the present invention were completed according to the above preparation steps. The specific design scheme of the light-emitting layer is detailed in the following embodiments and Table 1.

[0219] Example 1

[0220] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% D46 (5nm) / H51: 2wt% S21 (15nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0221] The anode is ITO; the hole injection layer is made of HI3; the hole transport layer is made of HI1; the electron blocking layer is made of EB3; the host material of the second light-emitting layer is H51, the guest molecule is D46, and the doping concentration is 2wt%; the host material of the first light-emitting layer is H51, the sensitizing molecule is S21, and the doping concentration is 2wt%; the hole blocking layer is made of HB3; the electron transport layer is made of ET11; and the electron injection layer and cathode materials are EI1 and metallic aluminum.

[0222] Comparative Example 1-1

[0223] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% S21 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0224] Compared to Example 1, only the first light-emitting layer is present; all other layers are the same as in Example 1.

[0225] Comparative Examples 1-2

[0226] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% D46 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0227] Compared to Example 1, only the second light-emitting layer is present; all other layers are the same as in Example 1.

[0228] Example 2

[0229] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H107: 2wt% D46 (5nm) / H107: 2wt% S21 (15nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0230] Compared with Example 1, the main material of the first and second light-emitting layers is changed to H107. Otherwise, the other layers are the same as in Example 1.

[0231] Comparative Example 2-1

[0232] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H107: 2wt% S21 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0233] Compared to Example 2, only the first light-emitting layer is present; all other layers are the same as in Example 2.

[0234] Comparative Example 2-2

[0235] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H107: 2wt% D46 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0236] Compared to Example 2, only the second light-emitting layer is present; all other layers are the same as in Example 2.

[0237] Example 3

[0238] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% D46 (5nm) / H51: 2wt% S45 (15nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0239] Compared with Example 1, the first light-emitting layer uses S45 as the sensitizing molecule. All other layers are the same as in Example 1.

[0240] Comparative Example 3-1

[0241] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H107: 2wt% S45 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0242] Compared to Example 3, only the first light-emitting layer is present; all other layers are the same as in Example 3.

[0243] Comparative Example 3-2

[0244] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H107: 2wt% D46 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0245] Compared to Example 3, only the second light-emitting layer is present; all other layers are the same as in Example 3.

[0246] Example 4

[0247] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% D74 (5nm) / H51: 2wt% S21 (15nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0248] Comparative Example 4-1

[0249] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% S21 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0250] Compared to Example 4, only the first light-emitting layer is present; all other layers are the same as in Example 4.

[0251] Comparative Example 4-2

[0252] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% D74 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0253] Compared to Example 4, only the second light-emitting layer is present; all other layers are the same as in Example 4.

[0254] Example 5

[0255] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H87: 2wt% D46 (5nm) / H51: 2wt% S21 (15nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0256] Compared with Example 1, the main materials of the first and second light-emitting layers are H51 and H87, respectively. Apart from this, the other layers are the same as in Example 1.

[0257] Comparative Example 5-1

[0258] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H87: 2wt% S21 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0259] Compared to Example 5, only the first light-emitting layer is present; all other layers are the same as in Example 5.

[0260] Comparative Example 5-2

[0261] Device structure: ITO / HI3 (10nm) / HT1 (40nm) / EB3 (5nm) / H51: 2wt% D46 (20nm) / HB3 (5nm) / ET11: 50wt% EI1 (30nm) / EI1 (1nm) / Al (100nm)

[0262] Compared to Example 5, only the second light-emitting layer is present; all other layers are the same as in Example 5.

[0263] Comparative examples and comparative studies demonstrate the improved performance of the dual-emitting layer. In Comparative Example 1-1, the device using the ultra-high radiative rate fluorescent molecule S21 as the guest molecule achieved an ultra-high EQE of 15.2%, but the half-width at half-maximum (WHM) of the electroluminescence spectrum was 46 nm, with color coordinates of (0.138, 0.147), indicating poor color purity. In Comparative Example 1-2, the device using the ultra-narrow spectrum fluorescent molecule D46 as the guest molecule had a WHM of only 14 nm and color coordinates of (0.135, 0.079), exhibiting excellent color purity, but the EQE was only 9.3%, indicating low efficiency. Example 1, however, prepared a device combining both methods using a dual-emitting layer, achieving an ultra-high EQE of 14.9% and a WHM of 16 nm with color coordinates of (0.136, 0.080). Its EQE was significantly improved compared to Comparative Examples 1-2, almost equivalent to that of Comparative Example 1-1, while the color purity was also much improved compared to Comparative Example 1-1. This indicates that using the high-radiative-rate fluorescent molecule S21 as the sensitizer to prepare the first emissive layer and the ultra-narrow-spectrum fluorescent molecule D46 as the emissive molecule to prepare the second emissive layer can improve both the device's EQE and the spectral narrowing, thus improving color purity. The devices of Example 1, Comparative Example 1-1, and Comparative Example 1-2 achieved a EQE of 20 mA / cm². 2 The LT95 at different current densities were 70.1 h, 73.4 h, and 52 h, respectively. The device lifetimes of Example 1 and Comparative Example 1-1 were comparable, but significantly improved compared to Comparative Example 1-2. This indicates that the device lifetime is determined by the first emitting layer, and the poor stability of narrow-spectrum emitting molecules is overcome in the dual-emitting-layer device. Compared to their respective comparative examples, the dual-emitting-layer devices in Examples 2-5 all outperformed the single-emitting-layer devices. In summary, the data analysis shows that the dual-emitting-layer device of the present invention can achieve both high efficiency and lifetime, as well as narrow-spectrum emission and improved color purity.

[0264] The device characteristic results of Examples 1-4 and Comparative Examples are listed in Table 1.

[0265] Table 1

[0266]

[0267] The photophysical properties of the molecules used in Examples 1-5 and the comparative examples are listed in Table 2.

[0268] Table 2

[0269]

[0270] Note: S1 is the singlet state energy level, Ф is the fluorescence quantum yield, τ is the fluorescence lifetime, and k is the fluorescence energy level. f The fluorescence radiative rate is calculated using equation (B).

[0271] [Practicality]

[0272] The organic electroluminescent blue light device of the present invention exhibits good stability, high luminous efficiency, and high color purity, making it suitable for application in display devices. Therefore, the present invention has high industrial applicability.

Claims

1. An organic electroluminescent device with a dual-emitting layer, characterized in that: The device comprises a cathode, an anode, and at least two organic layers sandwiched between the two electrodes, each containing a dual-emissivity layer. The dual-emissivity layer includes first and second organic light-emitting layers. The first organic light-emitting layer contains organic molecule I and organic molecule II, and the second organic light-emitting layer contains organic molecule III and organic molecule IV. Organic molecules I and III are host materials, and may be of the same or different types. Organic molecule II is a sensitizing material, and organic molecule IV is a light-emitting material. Formula (A): E S1 (I) > E S1 (II) Formula (B): E S1 (III) > E S1 (IV) Formula (C): E S1 (II) > E S1 (IV) In the above formula, E S1 (I) represents the lowest excited singlet state energy level of the organic molecule I, E S1 (II) represents the lowest excited singlet state energy level of the organic molecule II, E S1 (III) represents the lowest excited singlet state energy level of the organic molecule III, E S1 (IV) represents the lowest excited singlet energy level of the organic molecule IV; Among them, the fluorescence radiative rate of organic molecule II is in the range of 5. 10 8 s -1 ~5 10 10 s -1 Between these values, the full width at half maximum (FWHM) of organic molecules IV is between 5 and 40 nm.

2. The organic electroluminescent device according to claim 1, characterized in that: Organic molecule III emits blue light, with a peak emission between 440 and 490 nm.

3. The organic electroluminescent device according to claim 1 or 2, characterized in that: The thickness of the first organic light-emitting layer is 1~20 nm, and the mass content of organic molecule II is between 0.5 wt% and 20 wt%; the thickness of the second organic light-emitting layer is 1~20 nm, and the mass content of organic molecule IV is between 0.5 wt% and 20 wt%.

4. The organic electroluminescent device according to claim 1 or 2, characterized in that: The first organic light-emitting layer and the second organic light-emitting layer have no specific order. The first organic light-emitting layer can be located either near the cathode or near the anode.

5. The organic electroluminescent device according to claim 1 or 2, characterized in that: Organic molecule I and organic molecule III have molecular structures as shown in general formulas 1-6: Ar 1 and Ar 2 Each can be independently represented as one of the following: aryl group with 6-50 cyclic carbon atoms (substituted or unsubstituted), heteroaryl group with 5-50 cyclic atoms (substituted or unsubstituted), arylamine group with 6-50 cyclic atoms (substituted or unsubstituted), or heteroarylamine group with 3-50 cyclic atoms (substituted or unsubstituted); Ar 1 and Ar 2 Same or different; R 1 ~R 10 Ra and Ra independently represent one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 carbon atoms, substituted or unsubstituted heteroaryl group with 5 to 50 carbon atoms, substituted or unsubstituted arylamino group with 6 to 50 carbon atoms, and substituted or unsubstituted heteroarylamino group with 3 to 50 carbon atoms; and R 1 ~R 10 Two adjacent groups can bond together with the adjacent benzene ring to form one of the following: substituted or unsubstituted aryl group with 6-50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5-50 cyclic atoms, and at least one hydrogen atom in the formed ring can be replaced by any one of the following: halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1-20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3-20 cyclic carbon atoms, substituted or unsubstituted alkoxy group with 1-20 carbon atoms, substituted or unsubstituted aralkyl group with 7-30 carbon atoms, substituted or unsubstituted aryloxy group with 6-30 cyclic carbon atoms, substituted or unsubstituted aryl group with 6-50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5-50 cyclic atoms, substituted or unsubstituted arylamino group with 6-50 cyclic atoms, or substituted or unsubstituted heteroarylamino group with 3-50 cyclic atoms. m is a positive integer, ranging from 0 to 5; n is a positive integer, ranging from 1 to 3.

6. The organic electroluminescent device according to claim 1 or 2, characterized in that: The organic molecule II has a molecular structure as shown in general formulas 7-9: X represents O, S, and NR. 11 Or R 12 CR 13 ; Ar 1 Ar 2 Ar 3 Each can be independently represented as one of the following: aryl group with 6-50 cyclic carbon atoms (substituted or unsubstituted), heteroaryl group with 5-50 cyclic atoms (substituted or unsubstituted), arylamine group with 6-50 cyclic atoms (substituted or unsubstituted), or heteroarylamine group with 3-50 cyclic atoms (substituted or unsubstituted); Ar 1 Ar 2 Ar 3 Same or different; R 1 ~R 13 Each of the following independently represents one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5 to 50 cyclic atoms, substituted or unsubstituted arylamino group with 6 to 50 cyclic atoms, and substituted or unsubstituted heteroarylamino group with 3 to 50 cyclic atoms; and R 1 ~R 10 Two adjacent groups can bond together with the adjacent benzene ring to form one of the following: aryl group with 6-50 substituted or unsubstituted cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted cyclic atoms, and at least one hydrogen atom in the formed ring can be replaced by any one of the following: halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1-20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3-20 carbon atoms, substituted or unsubstituted alkoxy group with 1-20 carbon atoms, substituted or unsubstituted aralkyl group with 7-30 carbon atoms, substituted or unsubstituted aryloxy group with 6-30 carbon atoms, substituted or unsubstituted aryl group with 6-50 cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted arylamino group with 6-50 substituted or unsubstituted arylamino group with 3-50 substituted or unsubstituted cyclic atoms.

7. The organic electroluminescent device according to claim 1 or 2, characterized in that: The organic molecule IV has a molecular structure as shown in general formulas 10-14: Ar 1 and Ar 2 Each and every one of the following can be independently represented: aryl group with 6-50 carbon atoms (substituted or unsubstituted), heteroaryl group with 5-50 cyclic atoms (substituted or unsubstituted), arylamine group with 6-50 cyclic atoms (substituted or unsubstituted), or heteroarylamine group with 3-50 cyclic atoms (substituted or unsubstituted); Ar 1 and Ar 2 Same or different; R 1 ~R 16 Each of the following independently represents one of the following: hydrogen atom, deuterium atom, tritium atom, halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 20 carbon atoms, substituted or unsubstituted aralkyl group with 7 to 30 carbon atoms, substituted or unsubstituted aroxy group with 6 to 30 carbon atoms, substituted or unsubstituted aryl group with 6 to 50 cyclic atoms, substituted or unsubstituted heteroaryl group with 5 to 50 cyclic atoms, substituted or unsubstituted arylamino group with 6 to 50 cyclic atoms, and substituted or unsubstituted heteroarylamino group with 3 to 50 cyclic atoms; and R 1 ~R 10 Two adjacent groups can bond together with the adjacent benzene ring to form one of the following: aryl group with 6-50 substituted or unsubstituted cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted cyclic atoms, and at least one hydrogen atom in the formed ring can be replaced by any one of the following: halogen atom, cyano group, substituted or unsubstituted silyl group, substituted or unsubstituted alkyl group with 1-20 carbon atoms, substituted or unsubstituted cycloalkyl group with 3-20 carbon atoms, substituted or unsubstituted alkoxy group with 1-20 carbon atoms, substituted or unsubstituted aralkyl group with 7-30 carbon atoms, substituted or unsubstituted aryloxy group with 6-30 carbon atoms, substituted or unsubstituted aryl group with 6-50 cyclic atoms, heteroaryl group with 5-50 substituted or unsubstituted arylamino group with 6-50 substituted or unsubstituted arylamino group with 3-50 substituted or unsubstituted cyclic atoms.

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