Organic electroluminescent device based on double state sensitized fluorescence mechanism and preparation method thereof

Abstract

This invention belongs to the technical field of organic electroluminescent devices, and relates to an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism and its fabrication method. It includes a light-emitting layer; the light-emitting layer is made of a first organic compound, a second organic compound, and a third organic compound; the first organic compound has a first triplet state... T The energy level of the first organic compound must be higher than the first doublet state of the second organic compound. D 1. Energy level; the second organic compound is an organic compound with doublet luminescence properties, and the second organic compound's... D The energy level 1 is greater than the first singlet state of the third organic compound. S The first energy level; the third organic compound is a traditional fluorescent material, phosphorescent material, or a thermally activated delayed fluorescence material with multiple resonances. This invention realizes high-efficiency and low-roll-off high-color-purity light-emitting devices (especially deep blue light devices) and single-emitting-layer white light devices with excellent color coordinate stability.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent device technology, and relates to an organic electroluminescent device based on a doublet state sensitized fluorescence mechanism and its preparation method. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have shown broad application prospects in various fields such as consumer electronics, wearable and portable devices, and automotive displays due to their advantages such as self-illumination, fast response, and flexibility. Traditional fluorescent materials are limited by spin-forbidden conditions, which can only utilize 25% of singlet excitons, while the vast majority of triplet excitons are dissipated in a non-radiative manner, thus restricting the further development of OLEDs.

[0003] To fully utilize triplet excitons, phosphorescent materials have successfully utilized "dark" triplet excitons by leveraging the strong spin-orbit coupling of noble metal atoms, pushing the theoretical limit of exciton utilization to 100%, but at a high cost. Furthermore, the high excited-state energy and slow exciton dynamics (timescales from microseconds to milliseconds) of blue phosphorescent materials result in generally short device lifetimes. Thermally activated delayed fluorescence (TADF) materials, due to their smaller single-triple bandgap (Δ... E st Triple-state excitons can be converted into singlet excitons through a reverse system-reversal crossover (RISC) process, achieving 100% exciton utilization. However, due to the competitive relationship of multiple spin flips in singlet triplet states, the exciton utilization rate of TADF materials is limited, resulting in the blue TADF device's operating lifetime failing to meet practical requirements. Unlike the above materials, radical luminescent materials and d–f transition Ce(III) complexes are open-shell molecules, with both their ground and excited states being doublet states. This circumvents the limitations of spin statistics and transition forbidden states, resulting in a short excited-state lifetime (nanosecond level), making them considered an ideal class of luminescent materials. However, radical luminescent materials generally emit red and near-infrared light, making it difficult to achieve blue light. Ce(III) complexes, due to spin-orbit coupling, Ce… 3+ ground state 4f 1 The energy level will split into 2 F 5 / 2 and 2 F 7 / 2 The two energy levels have an energy difference of approximately 2000 cm. -1 The two emission peaks have a relatively large half-peak width, which is not conducive to ultra-high-definition display.

[0004] To expand the application range of OLEDs, addressing the stability issues of devices under operating conditions is crucial. On the one hand, optimizing material structure and improving the thermodynamic and photoelectric stability of materials can reduce the probability of material degradation. On the other hand, accelerating exciton dynamics processes in OLEDs and reducing the accumulation of excitons and related polarons can effectively suppress material degradation and reduce the possibility of device aging. The latter, in particular, is an important way to solve the roll-off of OLEDs at operating current density or brightness. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an organic electroluminescent device and its fabrication method based on a doublet-state sensitized fluorescence mechanism, achieving high-performance, high-color-purity blue light and single-emitting-layer warm white light. Specifically, this invention utilizes the large full width at half maximum (FWHM) and excellent luminescence performance of organic compounds with doublet-state luminescence characteristics. It can be combined with narrow-band multiple resonance TADF materials to achieve high-performance narrow-band blue light, and when combined with long-wavelength fluorescent and phosphorescent materials, only a single emitting layer is needed to achieve color coordinate-stable warm white light emission (color temperature below 5000). Furthermore, it shows promising application prospects in ultra-high-definition displays and eye-protection lighting.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, comprising a light-emitting layer; the light-emitting layer is made of a first organic compound, a second organic compound, and a third organic compound; The first organic compound is a hole-type material, an electronic material, a mixture of hole-type and electronic materials, or a traditional donor-acceptor thermally activated delayed fluorescence host material; The first triplet state of the first organic compound ( T 1) The energy level must be higher than the first doublet state of the second organic compound ( D 1) Energy level; the first singlet state of the conventional donor-acceptor thermally activated delayed fluorescence host material ( S 1) Energy levels and T The energy difference between the first and second energy levels is less than or equal to 200 mV; The second organic compound is an organic compound with doublet luminescence properties, and the second organic compound's D The energy level 1 is higher than that of the third organic compound. S 1 energy level; The third organic compound is a traditional fluorescent material, a phosphorescent material, or a thermally activated delayed fluorescence material with multiple resonances.

[0007] Preferably, the hole-type material is TCTA, mCBP, CzSi, mCP, SiCzCz, or D-SiCzCz; the electron-type material is PPF, TSPO1, DPEPO, SiTrzCz2, or D-SiTrzCz2; and the conventional donor-acceptor thermally activated delayed fluorescence host material is HTD-1, DMAC-DPS, DMAC-TRz, 4TCzBN, 4TCzPhBN, TTSA, 5TCzBN, or 5CzBN-D. The organic compound exhibiting doublet luminescence properties is a Ce(III) complex with df transition, and the Ce(III) complex with df transition is Ce-1, Ce-2, 3-Me, 1, 2-Me, 4-Pz, 4- n Bu、4- i Pr or Ce-TBO 2Et ; The conventional fluorescent material is Rubrene, TBRb, or DCJTB; The phosphorescent material is Ir(ppy)2(acac), Ir(dmppyph)2tmd, Ir(dpm)PQ2, PO-01, Ir(piq)3 or PtON-TBBI; The thermally activated delayed fluorescence material with multiple resonances is v -DABNA, o-Tol-ν-DABNA-Me or TBE02.

[0008] Preferably, when the first organic compound is a mixture of hole-type material and electronic-type material, the mass ratio of the hole-type material to the electronic-type material is 1:5 to 5:1.

[0009] Preferably, based on the total weight of the light-emitting layer, the doping concentration of the first organic compound is 67 wt% to 94.5 wt%, the doping concentration of the second organic compound is 5 wt% to 30 wt%, and the doping concentration of the third organic compound is 0.5 wt% to 3 wt%.

[0010] Preferred options also include: Substrate; An anode layer is disposed on the substrate; A hole injection layer is disposed on the anode layer; A hole transport layer is disposed on the hole injection layer; An electron blocking layer is disposed on the hole transport layer; The light-emitting layer is disposed on the electron blocking layer; A hole blocking layer is disposed on the light-emitting layer; An electron transport layer is disposed on the hole blocking layer; An electron injection layer is disposed on the electron transport layer; A metal cathode layer is disposed on the electron injection layer.

[0011] Preferably, the substrate is made of glass, quartz, polymer or metal; The anode is made of metal or indium tin oxide; The hole injection layer is made of HAT-CN, CuPc, MoO3 or V2O5 material; The hole transport layer is made of TAPC, TQTPA, NPB, BCFN, TPD, TCTA or mCP; Alternatively, the hole transport layer may be made of a mixture of HAT-CN and TAPC; The electron blocking layer is made of one or two of TCTA, CzSi, SiCzCz, CCP, BBSN and mCP; The hole blocking layer is made of DPEPO, PPF, TSPO1, Tm3PyP26PyB, PO-T2T, TmPyPB, TPBi or DPPyA; The electron transport layer is made of TSPO1, Tm3PyP26PyB, PO-T2T, TmPyPB, TPBi or DPPyA; The electron injection layer is made of LiF, Liq, Yb, Li2CO3 or Cs2CO3; The cathode layer is made of Al, Au, Ag or magnesium-aluminum alloy.

[0012] Preferably, when the hole transport layer is made of a mixture of HAT-CN and TAPC, the percentage of HAT-CN in the total mass of the hole transport layer is 0.05% to 0.5%.

[0013] Preferably, the hole injection layer has a thickness of 8-12 nm; the hole transport layer has a thickness of 30-60 nm; the electron blocking layer has a thickness of 5-15 nm; the light-emitting layer has a thickness of 15-25 nm; the hole blocking layer has a thickness of 5-15 nm; the electron transport layer has a thickness of 40-70 nm; the electron injection layer has a thickness of 0.8-1.5 nm; and the metal cathode layer has a thickness of 70-130 nm.

[0014] Secondly, the present invention provides a method for fabricating an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, comprising the following steps: Provide a substrate with an anode layer; A hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a metal cathode layer are sequentially deposited on the anode layer. During the evaporation processes of the hole injection layer, the hole transport layer, the electron blocking layer, the light-emitting layer, the hole blocking layer, and the electron transport layer, a vacuum level of less than 2.0 × 10⁻⁶ is maintained. -5 Pa; the evaporation process of the electron injection layer and the metal cathode layer is carried out under a vacuum degree of less than 2.0 × 10⁻⁶. -5 The experiment was conducted under the condition of Pa.

[0015] Thirdly, the present invention provides an application of an organic electroluminescent device based on a doublet state sensitized fluorescence mechanism in display devices and lighting devices.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes multiple energy transfer pathways, either doublet-state sensitized fluorescence or a combination of doublet-state sensitized fluorescence and thermally activated sensitized fluorescence systems, to reduce the accumulation of long-lived excitons, thereby suppressing energy loss and stability degradation caused by exciton annihilation. Figure 1 As shown in the energy transfer diagram, the second organic compound (an organic compound with doublet luminescence properties) is particularly important because it can convert the formed exciton into a short-lived doublet state, which is then transferred to the singlet state of the third organic compound, enabling rapid utilization and significantly improving the efficiency and lifetime of related devices in high-brightness applications. By combining organic compounds with doublet luminescence properties with traditional fluorescent materials or thermally activated delayed fluorescence materials with multiple resonances to form a doublet-sensitized fluorescence system, highly efficient (approximately 100%) and fast (>10) fluorescence rates can be achieved. 8 s -1 The device design strategy of transmitting light to the end object material in a bilinear state and radiating it solves the problem of insufficient color purity caused by the large size of organic compounds with doublet light emission characteristics. It realizes the emission of high color purity deep blue light, which is in short supply in the field, and achieves warm white light emission of a single light-emitting layer with a simple device structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the light-emitting layer structure of the doublet state sensitized fluorescence mechanism in the organic electroluminescent device of the present invention; Figure 2 Ce-TBO, a Ce(III) complex based on df transition, is an example of this invention. 2Et Current density-voltage-luminance characteristic curves of organic electroluminescent devices using luminescent materials; Figure 3 Ce-TBO, a Ce(III) complex based on df transition, is an example of this invention. 2Et External quantum efficiency-brightness characteristic curves of organic electroluminescent devices using luminescent materials; Figure 4 Ce-TBO, a Ce(III) complex based on df transition, is an example of this invention. 2Et Electroluminescence spectra of organic electroluminescent devices using light-emitting materials at 4 to 12 volts; Figure 5 Example 4 of this invention presents a deep blue organic light-emitting device with doublet-state sensitized fluorescence based on the Ce(III) complex Ce-TBO2Et with df transition, exhibiting a fluorescence intensity of 1000 cd / m². -2 Electroluminescence spectrum; Figure 6 This is the external quantum efficiency-luminescence characteristic curve of the deep blue organic light-emitting device based on the doublet state sensitized fluorescence of the Ce(III) complex Ce-TBO2Et with df transition in Example 4 of the present invention. Figure 7 Ce-TBO, a Ce(III) complex based on df transition, is described in Example 7 of this invention. 2Et Current density-voltage-brightness characteristic curves of a double-linear sensitized fluorescent single-emitting-layer white organic electroluminescent device; Figure 8 Ce-TBO, a Ce(III) complex based on df transition, is described in Example 7 of this invention. 2Et External quantum efficiency-luminance characteristic curve of double-line state sensitized fluorescent single-emitting-layer white organic electroluminescent device; Figure 9 Ce-TBO, a Ce(III) complex based on df transition, is described in Example 7 of this invention. 2Et Electroluminescence spectra of double-linear sensitized fluorescent monolayer white organic electroluminescent devices with 1000 ~ 10000 candela per square meter; Figure 10 Ce-TBO, a Ce(III) complex based on df transition, is described in Example 7 of this invention. 2Et Curves showing the variation of chromaticity coordinates in the range of 100 to 10000 candela per square meter for a double-linear sensitized fluorescent single-emitting-layer white organic electroluminescent device. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings: The first objective of this invention is to provide an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, comprising a light-emitting layer; the light-emitting layer is made of a first organic compound, a second organic compound, and a third organic compound; The first organic compound is a hole-type material, an electronic material, a mixture of hole-type materials and electronic materials (mixed co-host or excitocomplex type host) based on organic small molecules or polymers, or a traditional donor-acceptor thermally activated delayed fluorescence type host material; The first organic compound T The energy level 1 is higher than that of the second organic compound. D Level 1; the thermally activated delayed fluorescence host material S 1 energy level and T The energy difference between the first and second energy levels is less than or equal to 200 mV; The second organic compound is an organic compound with doublet luminescence properties, and the second organic compound's D The energy level 1 is higher than that of the third organic compound. S 1 energy level; The third organic compound is a traditional fluorescent material, a phosphorescent material, or a thermally activated delayed fluorescence material with multiple resonances.

[0025] Among them, for traditional donor-acceptor type thermally activated delayed fluorescence (TADF) host materials, high quantum fluorescence yield is preferred, especially in the case of pure thin films, with high quantum fluorescence yield (PLQY>80%) and reverse intersystem crossing rate (…). k RISC >10 6 s 1 The faster TADF material system serves as the main carrier for charge carrier transport and exciton recombination. The second organic compound is a compound with doublet luminescence properties, including pure organic small molecules and doublet luminescent dyes containing metal elements, particularly preferably coordination compounds containing rare earth elements, and especially preferably compounds with both high quantum fluorescence yield (PLQY > 60%) and... D 1→ D 0 radiative transition rate is fast ( k D >10 7 s 1 Coordination compounds of rare earth cerium with df transitions, and its D The energy level 1 is higher than that of the first organic compound. T The first organic compound has a low energy level, thus enabling energy transfer from the first organic compound to the second organic compound, including Foster resonance energy transfer (FRET) based on long-range dipole interactions and Dexter energy transfer (DET) based on short-range electron exchange, thereby ensuring exciton utilization and short exciton lifetime based on energy transfer; the third compound is a fluorescent material, phosphorescent material, or thermally activated delayed fluorescence material with a fast radiative transition rate, especially preferably a traditional fluorescent material with a pure hydrocarbon structure, or a multi-resonant or boron dipyrrole type with a narrow spectrum (FWHM < 50 nm), particularly preferably with high quantum fluorescence yield (PLQY > 80%) and S 1 / T 1→ S Dyes with fast 0 radiative transition rates, S The energy level of the first organic compound is compared to that of the second organic compound. TThe concentration of the third organic compound is low to ensure energy transfer between the first and second organic compounds. When achieving monochromatic light, the final luminescence of the system must be dominated by the third organic compound (its luminescence accounts for at least 70% of the system intensity). When achieving white light, the second and third organic compounds need to emit light simultaneously, with the doping concentration of the third organic compound not exceeding 1 wt% and its luminescence accounting for less than 70% of the system intensity.

[0026] The cavity-type material is TCTA (4,4',4”-tris(carbazole-9-yl)triphenylamine), mCBP (3,3'-bis(9H-carbazole-9-yl)-1,1'-biphenyl), CzSi (9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole), mCP (9,9'-(1,3-phenyl)bis-9H-carbazole), SiCzCz (9-[3-(triphenylsilyl)phenyl)-9H-3,9'-bicarbazole), or D-SiCzCz (deuterated SiCzCz). The electronic material is PPF (2,5-diphenylfuran), TSPO1 (diphenyl[4-(triphenylsilyl)phenyl]oxophosphine), DPEPO (di[2-((oxo)diphenylphosphino)phenyl] ether), SiTrzCz2 (9,9'-[6-[3-(triphenylsilyl)phenyl)-1,3,5-triazine-2,4-diyl]bis-9H-carbazole) or D-SiTrzCz2 (deuterated SiTrzCz2); The conventional donor-acceptor thermoactivated delayed fluorescence host materials are HTD-1, DMAC-DPS (bis[4-(9,9-dimethyl-9,10-dihydroacrylidine)phenyl]sulfone), DMAC-TRz (10-(4-(4,6-diphenyl-1,3,5-triazol-2-yl)phenyl)-9,9-dimethyl-9,10-dihydroacrylidine), 4TCzBN (2,3,5,6-tetrakis(3,6-di-tert-butyl-9H-carbazole-9-yl)benzonitrile), and 4TCzPhBN (2',3'). 5',6'-tetra(3,6-di-tert-butyl-9H-carbazole-9-yl)-[1,1'-biphenyl]-4-nitrile, TTSA (10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-methylphenyl)-10H-spiro[acridin-9,9-fluorene), 5TCzBN (2,3,4,5,6-penta(3,6-di-tert-butyl-9H-carbazole-9-yl)benzonitrile) or 5CzBN-D (deuterated 2,3,4,5,6-penta(9H-carbazole-9-yl)benzonitrile); The organic compound exhibiting doublet luminescence properties is a Ce(III) complex with df transition or bis(2-phenyl-4,5-dimethylimidazolium)ferro(III) hexafluorophosphate ([Fe(phtmeimb)2]PF6), wherein the Ce(III) complex with df transition is Ce-1, Ce-2, 3-Me, 1, 2-Me, 4-Pz, 4- n Bu、4- i Pr or Ce-TBO 2Et ; The conventional fluorescent materials are Rubrene (5,6,11,12-tetraphenylnaphthonaphthyl), TBRb (5,6,11,12-tetraphenylnaphthonaphthyl), or DCJTB ((E)-4-diacetonide-2-tert-butyl-6-(1,1,7,7-tetramethyljulonidin vinyl)pyran). The phosphorescent materials are Ir(ppy)2(acac) (bis(2-phenylpyridine)iridium(III) acetylacetonate), Ir(dmppyph)2tmd (bis(2-(3,5-dimethylphenyl)-4-phenylpyridine)(2,2,6,6-tetramethylheptane-3,5-diketoester)iridium(III)), Ir(dpm)PQ2 (bis(2-phenylquinoline)(2,2,6,6-tetramethylheptane-3,5-diketoester)iridium(III)), and PO-01 (bis(4-... phenyl-thiophene[3,2-C]pyridine-C2,N)iridium(III)), Ir(piq)3 (tris[1-phenylisoquinoline-C2,N]iridium(III)) or PtON-TBBI (platinum,[2-[3-[3-3,5-bis(1,1-dimethylethyl)phenyl]-1H-benzimidazol-1-yl-KC2]phenoxy-KC2]-9-[4-(1,1-dimethylethyl)-2-pyridyl-KN]-9H-carbazole(4-)-KC1]-,(SP-4-4)-); The multi-resonance thermally activated delayed fluorescence material is v -DABNA (N7,N7,N13,N13,5,9,11,15-octaphenyl-5,9,11,15-tetrahydro-5,9,11,15-tetraaza-19B,20B-diboronaphtho[3,2,1-DE:1',2',3'-JK]pentaphenyl-7,13-diamine), TBE02 (5H,9H-[1,4]benzazoleboron[2,3,4-kl]benzazoleboron compound) or o-Tol-ν-DABNA-Me.

[0027] The structures of TCTA, mCBP, CzSi, PPF, TSPO1, DPEPO, mCP, SiCzCz, SiTrzCz2, D-SiCzCz and D-SiTrzCz2 are shown below, respectively;

[0028]

[0029] The structures of HTD-1, DMAC-DPS, DMAC-TRz, 4TCzBN, 4TCzPhBN, TTSA, 5TCzBN, or 5CzBN-D are shown below:

[0030]

[0031] The Ce-1, Ce-2, 3-Me, 1, 2-Me, 4-Pz, 4- n Bu、4- i Pr and Ce-TBO 2Et The structures are shown below:

[0032]

[0033] The structure of [Fe(phtmeimb)2]PF6 is shown below:

[0034] The Rubrene, TBRb, DCJTB, Ir(ppy)2(acac), Ir(dmppyph)2tmd, Ir(dpm)PQ2, PO-01, Ir(piq)3, PtON-TBBI, v The structures of -DABNA, TBE02, and o-Tol-ν-DABNA-Me are shown below:

[0035]

[0036]

[0037] The organic electroluminescent device based on the doublet state sensitized fluorescence mechanism provided by this invention can realize rapid energy transfer from high energy level to low energy level to the terminal guest material and emit light, and can emit narrow-band deep blue light and white light.

[0038] Using this device structure as the emitting layer of an electroluminescent device, the resulting device exhibits excellent performance and application value. First, an organic compound with doublet emission characteristics is used as the second organic compound. Its emission mechanism is doublet emission, possessing parity-allowed characteristics and an excited-state lifetime on the nanosecond scale, achieving 100% exciton utilization, thus fabricating a high-efficiency, low-roll-off blue electroluminescent device. Second, compared to traditional devices using thermally activated or phosphorescently activated fluorescence, this invention introduces an organic compound with doublet emission characteristics as the second organic compound and uses conventional fluorescence or multiple resonance thermally activated delayed fluorescence as the third organic compound, proposing and implementing a doublet-sensitized fluorescence strategy. This strategy avoids the slow exciton dynamics process caused by triplet states in traditional sensitization methods. Since the doublet exciton generation of the organic compound with doublet emission characteristics is not subject to spin statistics, and its doublet radiative transitions and energy transfers are unrestricted by spin, efficient and rapid exciton utilization can be achieved, thereby obtaining a high-performance narrow-bandgap deep blue OLED. Furthermore, by combining organic compounds with doublet emission properties as the second organic compound with third organic compounds such as conventional fluorescence, phosphorescence, or multiple resonance thermally activated delayed fluorescence, the doping concentration of the third organic compound in doublet-sensitized fluorescence technology can be controlled, thereby enabling the realization of high-efficiency and color coordinate-stable single-emitting-layer white light devices.

[0039] In summary, this invention, by selecting an organic compound with doublet emission characteristics as the second organic compound, achieves a balanced carrier distribution and effectively improves exciton utilization, thereby significantly delaying efficiency roll-off while improving device efficiency and brightness. Organic compounds with doublet emission characteristics can be used to prepare high-efficiency and stable blue OLEDs; when used as narrow-band dyes or traditional fluorescent and phosphorescent photosensitizers, they contribute to the realization of high-efficiency and stable high-color-purity deep blue OLEDs and high-efficiency white OLEDs with stable color coordinates.

[0040] When the organic host material is a mixture of the hole-type material and the electron-type material, the mass ratio of the hole-type material to the electron-type material is 1:5 to 5:1. By limiting the mass ratio of the hole-type and electron-type materials in the mixed host material to this range, they can form an effective exciton complex or construct a continuous energy level gradient, promoting the maximization of the overlap of hole and electron spatial distribution within the emitting layer. This solves the problems of exciton recombination region shift, increased leakage current, and decreased device efficiency caused by carrier injection imbalance. It can significantly improve the carrier balance rate, optimize the exciton generation position and confine it to the central region of the emitting layer, thereby improving the radiative recombination probability and the overall performance stability of the device.

[0041] For example, based on the total weight of the luminescent layer, the doping concentration of the first organic compound is 67 wt% to 94.5 wt%, the doping concentration of the second organic compound is 5 wt% to 30 wt%, and the doping concentration of the third organic compound is 0.5 wt% to 3 wt%. To achieve high color purity deep blue light from DSF, we need to precisely control the doping concentration of the third organic compound (0.5 wt% to 3.0 wt%) to maximize the Förster resonance energy transfer (FRET) process while optimizing the doping concentration. If the doping concentration of the third organic compound is too high, aggregation-induced quenching will lead to poor luminescence performance; if the doping concentration is too low, energy transfer will be insufficient, resulting in a stronger luminescence intensity of the blue photosensitizer and reduced color purity.

[0042] A second objective of this invention is to provide an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, further comprising: Substrate; An anode layer is disposed on the substrate; A hole injection layer is disposed on the anode layer; A hole transport layer is disposed on the hole injection layer; An electron blocking layer is disposed on the hole transport layer; The light-emitting layer is disposed on the electron blocking layer; A hole blocking layer is disposed on the light-emitting layer; An electron transport layer is disposed on the hole blocking layer; An electron injection layer is disposed on the electron transport layer; A metal cathode layer is disposed on the electron injection layer.

[0043] By utilizing a hole injection layer and a hole transport layer to achieve efficient hole injection, an electron blocking layer to prevent premature electron penetration of the light-emitting layer, a hole blocking layer to restrict hole diffusion, and an electron transport layer and an electron injection layer to promote electron injection, and a positive and negative electrodes to establish a working electric field, the systemic problems such as carrier imbalance, exciton leakage, and nonradiative recombination at the interface caused by relying solely on the design of the light-emitting layer are solved. This is conducive to achieving precise confinement and efficient recombination of excitons in the light-emitting layer, significantly reducing the start-up voltage, and improving the maximum brightness and external quantum efficiency.

[0044] For example, the substrate may be made of glass, quartz, polymer or metal.

[0045] The anode layer is made of metal, graphene, or indium tin oxide.

[0046] The hole injection layer is made of HAT-CN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene), CuPc (copper phthalocyanine(II)), MoO3 (molybdenum oxide), or V2O5 (vanadium pentoxide). The structures of HAT-CN and CuPc are shown below:

[0047] The hole transport layer is made of TAPC (4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline]), TQTPA (tris(4-(quinolin-8-yl)phenyl)amine), NPB (N,N'-bis(naphthyl-1-yl)-N,N'-bis(phenyl)-benzidine), BCFN (N-(4-biphenyl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)-9H-fluorene-2-amine), TPD (N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine), TCTA or mCP; Alternatively, the hole transport layer may be made of a mixture of HAT-CN and TAPC, in which case the percentage of HAT-CN in the total mass of the hole transport layer is 0.05% to 0.5%.

[0048] The structures of TAPC, TQTPA, NPB, or TPD are shown below:

[0049] The electron blocking layer is made of one or two of TCTA, CzSi, SiCzCz, CCP (9-phenyl-3,9'-bis-9H-carbazole), BBSN (N-(biphenyl-2-yl)-N-(biphenyl-4-yl)-9,9'-spirodifluorenyl-4-amine) and mCP.

[0050] The structures of CCP and BBSN are as follows:

[0051] The hole-blocking layer is made of DPEPO, PPF, TSPO1, Tm3PyP26PyB (1,3,5-tris(6-(3-(pyridin-3-yl)phenyl)pyridin-2-yl)benzene), PO-T2T (2,4,6-tris[3-(diphenylphosphoxy)phenyl]-1,3,5-triazole), TmPyPB (1,3,5-tris[(3-pyridin)-3-phenyl]benzene), TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene) or DPPyA (9,10-bis(6-phenylpyridin-3-yl)anthracene).

[0052] The structures of Tm3PyP26PyB, PO-T2T, TmPyPB, and TPBi are shown below:

[0053] The electron transport layer is made of TSPO1, Tm3PyP26PyB, PO-T2T, TmPyPB (1,3,5-tris[(3-pyridine)-3-phenyl]benzene), and TPBi.

[0054] The electron injection layer is made of LiF (lithium fluoride), Liq (8-hydroxyquinoline-lithium), Li2CO3 (lithium carbonate), or Cs2CO3 (cesium carbonate).

[0055] The metal cathode layer is made of Al (aluminum), Au (gold), Ag (silver) or a magnesium-aluminum alloy.

[0056] Furthermore, when the hole transport layer is made of a mixture of HAT-CN and TAPC, the percentage of HAT-CN in the total mass of the hole transport layer is 0.05% to 0.5%. The inclusion of trace amounts of HAT-CN can create a suitable energy level gradient at the interface, promoting a smooth transition of holes from the injection layer to the transport layer, while also avoiding exciton quenching or decreased material stability caused by excessive doping.

[0057] For example, the hole injection layer has a thickness of 8-12 nm; the hole transport layer has a thickness of 30-60 nm; the electron blocking layer has a thickness of 5-15 nm; the light-emitting layer has a thickness of 15-25 nm; the hole blocking layer has a thickness of 5-15 nm; the electron transport layer has a thickness of 40-70 nm; the electron injection layer has a thickness of 0.8-1.5 nm; and the metal cathode layer has a thickness of 70-130 nm.

[0058] By controlling the thickness of each functional layer within a specific range optimized by optical and electrical simulations, we can ensure that each layer has sufficient physical integrity to realize its function (such as blocking, transmission, and injection), while avoiding excessive thickness that would lead to increased series resistance or microcavity effect detuning. This allows for the coordinated control of optical microcavity effect and carrier transit time, achieving a balance between high brightness, low voltage, high efficiency, and excellent stability.

[0059] Meanwhile, this invention provides a method for fabricating an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, comprising the following steps: Provide a substrate with an anode layer; A hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a metal cathode layer are sequentially deposited on the anode layer. During the evaporation processes of the hole injection layer, the hole transport layer, the electron blocking layer, the light-emitting layer, the hole blocking layer, and the electron transport layer, a vacuum degree of < 2.0 × 10⁻⁶ is maintained. -5 Pa; the evaporation process of the electron injection layer and the metal cathode layer is carried out under a vacuum degree < 2.0 × 10⁻⁶. -5 The experiment was conducted under the condition of Pa.

[0060] By setting a strict evaporation sequence and a high vacuum environment (< 2.0×10⁻⁶), -5 (Pa) ensures that the molecular free path is much larger than the cavity size, achieving conformal deposition and pure interface construction. Stepwise evaporation avoids metal source contamination of organic materials, thus solving common failure modes such as interface contamination, oxidation, and mutual solubility in multilayer structure preparation. This results in low defect density and high purity multilayer films, supporting the high reproducibility of device performance and mass production feasibility.

[0061] A third objective of this invention is to provide another organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, further comprising: Substrate; An anode layer is disposed on the substrate; A hole injection layer is disposed on the anode layer; A hole transport layer is disposed on the hole injection layer; The light-emitting layer is disposed on the electron blocking layer; An electron transport layer is disposed on the hole blocking layer; An electron injection layer is disposed on the electron transport layer; A metal cathode layer is disposed on the electron injection layer.

[0062] This invention simplifies the manufacturing process and reduces production costs by omitting the electron blocking layer and hole blocking layer, while maintaining the basic performance of the device. Specifically, by optimizing the energy level matching between the hole transport layer and the light-emitting layer, and the blocking ability of the electron transport layer to block holes, excitons are effectively confined within the light-emitting layer for recombination and luminescence. Simultaneously, the simplified structure reduces the number of interfaces, helping to reduce interface defects and non-radiative recombination risks. This, in turn, improves the device's process compatibility and scalability potential while maintaining high luminous efficiency, making it particularly suitable for large-area lighting or display applications that are cost-sensitive and require moderate performance.

[0063] For example, the materials and thickness ranges of the substrate, the anode layer, the hole injection layer, the hole transport layer, the electron transport layer, the electron injection layer, and the metal cathode layer are all as described above.

[0064] Meanwhile, this invention provides a method for fabricating an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, comprising the following steps: Provide a substrate with an anode layer; A hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a metal cathode layer are sequentially deposited on the anode layer. During the evaporation processes of the hole injection layer, the hole transport layer, the light-emitting layer, and the electron transport layer, a vacuum level of < 2.0 × 10⁻⁶ is maintained. -5 Pa; the evaporation process of the electron injection layer and the metal cathode layer is carried out under a vacuum degree < 2.0 × 10⁻⁶. -5 The experiment was conducted under the condition of Pa.

[0065] A fourth objective of this invention is to provide another organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, further comprising: Substrate; An anode layer is disposed on the substrate; A hole injection layer is disposed on the anode layer; A hole transport layer is disposed on the hole injection layer; An electron blocking layer is disposed on the hole transport layer; The light-emitting layer is disposed on the electron blocking layer; An electron transport layer is disposed on the hole blocking layer; An electron injection layer is disposed on the electron transport layer; A metal cathode layer is disposed on the electron injection layer.

[0066] The electron blocking layer effectively suppresses the leakage of electrons from the luminescent layer to the hole transport layer, ensuring efficient recombination of excitons within the luminescent layer. At the same time, the electron transport layer's own excellent hole blocking properties replace the function of an independent hole blocking layer, simplifying the multilayer film structure.

[0067] For example, the materials and thickness ranges of the substrate, the anode layer, the hole injection layer, the hole transport layer, the electron blocking layer, the electron transport layer, the electron injection layer, and the metal cathode layer are all as described above.

[0068] Meanwhile, this invention provides a method for fabricating an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, comprising the following steps: Provide a substrate with an anode layer; A hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a metal cathode layer are sequentially vapor-deposited on the anode layer. During the evaporation processes of the hole injection layer, the hole transport layer, the electron blocking layer, the light-emitting layer, and the electron transport layer, a vacuum level of < 2.0 × 10⁻⁶ is maintained. -5 Pa; the evaporation process of the electron injection layer and the metal cathode layer is carried out under a vacuum degree < 2.0 × 10⁻⁶. -5 The experiment was conducted under the condition of Pa.

[0069] The fifth objective of this invention is to provide an application of an organic electroluminescent device based on a double-linear state-sensitized fluorescence mechanism in display and lighting devices. Experimental results show that the organic electroluminescent device prepared by this invention exhibits good luminous efficiency and color stability in AMOLED displays and solid-state lighting models, and therefore can be used to prepare health lighting devices for preventing and / or treating visual fatigue, as well as high color gamut full-color display devices. This is achieved by utilizing the high efficiency of this device (high color purity deep blue light device EQE based on double-linear state-sensitized fluorescence). max >30%; Single-emitting-layer warm white light device EQE max With advantages such as >20%, low efficiency roll-off, narrow band emission (approximately 20 nm), and stable white light color coordinates (Δx / y < 0.01), it solves the problems of short lifespan, high cost, and color distortion faced by traditional OLEDs in ultra-high-definition display and eye-protection lighting applications.

[0070] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0071] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0072] Example 1 First, the glass substrate with the ITO pattern is ultrasonically cleaned sequentially with cleaning solution and deionized water, then placed in an oven until dry. The dried substrate is then transferred to a tray and moved to the pretreatment vacuum chamber, and finally to the organic evaporation chamber, where the vacuum level is <2.0 × 10⁻⁶. -5 In an organic evaporation chamber, an 8 nm thick HAT-CN hole injection layer, a 40 nm thick TAPC hole transport layer, and a 25 nm thick light-emitting layer are sequentially deposited on an ITO layer. v -DABNA(1 wt%):Ce-TBO 2Et (9 wt%): SiCzCz (90 wt%), where wt% is the weight percentage of each component in the light-emitting layer] and a 50 nm thick TmPyPB electron transport layer. Next, the unfinished device was transferred to a metal evaporation chamber, at < 2.0 × 10⁻⁶. -5 A 1 nm thick LiF electron injection layer was deposited under a vacuum atmosphere. Finally, a 100 nm thick Al metal electrode layer was deposited on the LiF layer using a specially designed mask to fabricate a structure of ITO / HAT-CN (8 nm) / TAPC (40 nm) / v -DABNA(1 wt%):Ce-TBO 2Et (9 wt%): SiCzCz (90 wt%, 25 nm) / TmPyPB (50 nm) / LiF (1 nm) / Al (100 nm). During the evaporation process, the evaporation rate of HAT-CN in the hole injection layer was controlled at 0.01 nm / s, and the evaporation rate of TAPC in the hole transport layer was controlled at 0.05 nm / s. In the light-emitting layer... v -DABNA and Ce-TBO 2EtThe evaporation rates were controlled sequentially at 0.0005 nm / s and 0.005 nm / s, respectively. The evaporation rate of SiCzCz was controlled at 0.05 nm / s, the evaporation rate of TmPyPB in the electron transport layer was controlled at 0.05 nm / s, the evaporation rate of LiF in the electron injection layer was controlled at 0.005 nm / s, and the evaporation rate of Al in the metal cathode layer was controlled at 0.5 nm / s. The deposition rate and thickness of each functional layer were controlled using a quartz crystal film thickness gauge. The resulting device was measured directly in atmospheric conditions without further encapsulation. Under DC voltage drive, the turn-on voltage was 3.1 V, the maximum external quantum efficiency was 31.3%, the maximum luminance was 23890 candela per square meter, and the color coordinates were (0.133, 0.140). When the luminance was 1000 candela per square meter, the external quantum efficiency was 27.0%, and the efficiency roll-off was 13.7%.

[0073] Example 2 Maintaining the same experimental procedure and device structure as in Example 1, v - Replace the doping concentration of DABNA with 0.5 wt%, and replace Ce-TBO 2Et The doping concentration was replaced with 5 wt%, and the SiCzCz doping concentration was replaced with 94.5 wt%. The device has a turn-on voltage of 3.2 V, a maximum external quantum efficiency of 30.5%, a maximum luminance of 29366 candela per square meter, and color coordinates of (0.158, 0.180). When the luminance is 1000 candela per square meter, the external quantum efficiency is 26.2%, and the efficiency roll-off is 14.1%.

[0074] Example 3 Maintaining the same experimental procedure and device structure as in Example 1, v - The doping concentration of DABNA was replaced with 3 wt%, and the Ce(III) complex Ce-TBO with df transition was replaced. 2Et The doping concentration was replaced with 30wt%, and the SiCzCz doping concentration was replaced with 67wt%. The device has a turn-on voltage of 2.8V, a maximum external quantum efficiency of 28.6%, a maximum luminance of 18876 candela per square meter, and color coordinates of (0.133, 0.121). When the luminance is 1000 candela per square meter, the external quantum efficiency is 23.3%, and the efficiency roll-off is 18.5%.

[0075] Example 4 Maintaining the same experimental procedure and device structure as in Example 1, the light-emitting layer [ v -DABNA(1 wt%):Ce-TBO 2Et [(9 wt%):SiCzCz(90 wt%)] is replaced with [o-Tol- ν -DABNA-Me (2 wt%):Ce-TBO2Et (9 wt%):SiCzCz (44.5 wt%):SiTrzCz2 (44.5 wt%)]. The device has a turn-on voltage of 3.4 V, a maximum external quantum efficiency of 31.8%, a maximum luminance of 25763 candela per square meter, and color coordinates of (0.132, 0.156). When the luminance is 1000 candela per square meter, the external quantum efficiency is 28.0%, and the efficiency roll-off is 11.9%.

[0076] Example 5 Maintaining the same experimental procedure and device structure as in Example 4, the o-Tol- light-emitting layer was applied. ν - The doping concentration of DABNA-Me was replaced with 0.5 wt%, Ce-TBO 2Et The doping concentration was replaced with 10.5 wt%. The device has a turn-on voltage of 3.4 V, a maximum external quantum efficiency of 29.9%, a maximum luminance of 31570 candela per square meter, and color coordinates of (0.124, 0.171). When the luminance is 1000 candela per square meter, the external quantum efficiency is 25.7%, and the efficiency roll-off is 14.0%.

[0077] Example 6 Maintaining the same experimental procedure and device structure as in Example 4, the o-Tol- in the light-emitting layer ν The concentration of -DABNA-Me was replaced with 3.0 wt%, Ce-TBO 2Et The doping concentration was replaced with 8.0 wt%. The device has a turn-on voltage of 3.1 V, a maximum external quantum efficiency of 28.2%, a maximum luminance of 21168 candela per square meter, and color coordinates of (0.121, 0.148). When the luminance is 1000 candela per square meter, the external quantum efficiency is 24.1%, and the efficiency roll-off is 14.5%.

[0078] Example 7 First, the glass substrate with the ITO pattern is ultrasonically cleaned sequentially with cleaning solution and deionized water, then placed in an oven until dry. The dried substrate is then transferred to a tray and moved to the pretreatment vacuum chamber, and finally to the organic evaporation chamber. The process continues until the vacuum level is less than 2.0 × 10⁻⁶. -5 In an organic vapor deposition chamber, an 8 nm thick HAT-CN hole injection layer, a 30 nm thick TAPC hole transport layer, and a 20 nm thick light-emitting layer [TBRb(0.5 wt%):Ce-TBO] are sequentially deposited on an ITO layer. 2Et (9.5 wt%): SiCzCz (90 wt%), where wt% is the weight percentage of each component in the light-emitting layer] and a 50 nm thick TmPyPB electron transport layer. Next, the unfinished device was transferred to a metal evaporation chamber, where the deposition temperature was less than 2.0 × 10⁻⁶. -5A 1 nm thick LiQ electron injection layer was deposited under a vacuum atmosphere of Pa. Finally, a 100 nm thick metal Al electrode layer was deposited on the LiQ layer using a specially made mask to prepare a structure of ITO / HAT-CN (8 nm) / TAPC (40 nm) / TBRb (0.5 wt%):Ce-TBO. 2Et (9.5 wt%): SiCzCz (90 wt%, 20 nm) / TmPyPB (50 nm) / Liq (1 nm) / Al (100 nm). During the evaporation process, the evaporation rate of HAT-CN in the hole injection layer was controlled at 0.01 nm / s, the evaporation rate of TAPC in the hole transport layer was controlled at 0.05 nm / s, and the evaporation rates of TBRb and Ce-TBO in the light-emitting layer were controlled at 0.05 nm / s. 2Et The evaporation rates were controlled sequentially at 0.0005 nm / s and 0.005 nm / s, respectively. The evaporation rate of SiCzCz was controlled at 0.05 nm / s, the evaporation rate of TmPyPB in the electron transport layer was controlled at 0.05 nm / s, the evaporation rate of Liq in the electron injection layer was controlled at 0.005 nm / s, and the evaporation rate of Al in the metal cathode layer was controlled at 0.5 nm / s. The evaporation rates and thicknesses of each functional layer were controlled using a quartz crystal film thickness gauge. The resulting device was measured directly in atmospheric conditions without further encapsulation. Under DC voltage drive, the turn-on voltage was 4.5 V, the maximum current efficiency was 55.4 candela per ampere, the maximum external quantum efficiency was 20.2%, the maximum luminance was 20904 candela per square meter, and the color coordinates were (0.36, 0.43). When the luminance was 1000 candela per square meter, the external quantum efficiency was 17.2%, and when the luminance reached 10000 candela per square meter, the external quantum efficiency still remained at 11.0%. Within the brightness range of 1000 to 10000 candela per square meter, the change in the x-coordinate value is 0.009, and the change in the y-coordinate value is 0.006.

[0079] Example 8 Maintaining the same experimental procedure and device structure as in Example 7, the doping concentration of TBRb was replaced with 1 wt%, and Ce-TBO was used instead. 2Et The doping concentration was replaced with 30wt%, and the SiCzCz doping concentration was replaced with 69wt%. The device's turn-on voltage was 4.8V, the maximum external quantum efficiency was 18.8%, the maximum luminance was 18976 candela per square meter, and the color coordinates were (0.34, 0.38). When the luminance was 1000 candela per square meter, the external quantum efficiency was 16.1%, and when the luminance reached 10000 candela per square meter, the external quantum efficiency remained at 10.2%. The change in the x-value of the color coordinate within the luminance range of 1000 to 10000 candela per square meter was 0.009, and the change in the y-value of the color coordinate was 0.008.

[0080] Example 9 Maintaining the same experimental procedure and device structure as in Example 7, the doping concentration of TBRb was replaced with 0.8 wt%, and Ce-TBO was used instead. 2Et The doping concentration was replaced with 89.2 wt%, and the SiCzCz doping concentration was replaced with 10 wt%. The device's turn-on voltage was 4.3 V, the maximum external quantum efficiency was 17.5%, the maximum luminance was 22359 candela per square meter, and the color coordinates were (0.34, 0.45). The external quantum efficiency was 14.8% at a luminance of 1000 candela per square meter, and it still maintained 9.6% at a luminance of 10000 candela per square meter. The change in the x-value of the color coordinates was 0.008 and the change in the y-value of the color coordinates was 0.007 within the luminance range of 1000 to 10000 candela per square meter.

[0081] Example 10 Unlike Example 7, the doping concentration of TBRb was replaced with 3 wt%, and Ce-TBO was used instead. 2Et The doping concentration was replaced with 30 wt%, and the SiCzCz doping concentration was replaced with 67 wt%. Next, a 15 nm thick CCP electron blocking layer was deposited on the TAPC hole transport layer, and then a 25 nm thick light-emitting layer was deposited on the CCP electron blocking layer.

[0082] Example 11 Unlike Example 10, a 15 nm DPEPO hole blocking layer was deposited on the light-emitting layer, and then an electron transport layer was deposited on the DPEPO hole blocking layer; the thickness of the CCP electron blocking layer was 5 nm.

[0083] Example 12 Unlike Example 11, the thickness of the DPEPO hole blocking layer is 5 nanometers.

[0084] Example 13 Unlike Example 11, the thickness of the light-emitting layer is 15 nanometers.

[0085] Example 14 Unlike Example 11, the hole injection layer has a thickness of 12 nanometers.

[0086] Example 15 Unlike Example 11, the hole transport layer has a thickness of 60 nanometers.

[0087] Example 16 Unlike Example 11, the thickness of the electron transport layer is 40 nanometers.

[0088] Example 17 Unlike Example 11, the thickness of the electron transport layer is 70 nanometers.

[0089] Example 18 Unlike Example 11, the thickness of the electron injection layer is 0.8 nanometers.

[0090] Example 19 Unlike Example 11, the thickness of the electron injection layer is 1.5 nanometers.

[0091] Example 20 Unlike Example 11, the thickness of the metal cathode layer is 70 nanometers.

[0092] Example 21 Unlike Example 11, the thickness of the metal cathode layer is 130 nanometers.

[0093] Example 22 Unlike Example 11, the hole transport layer is made of a mixture of HAT-CN and TAPC, in which the HAT-CN accounts for 0.05% of the total mass of the hole transport layer.

[0094] Example 23 Unlike Example 11, the hole transport layer is made of a mixture of HAT-CN and TAPC, in which the HAT-CN accounts for 0.5% of the total mass of the hole transport layer.

[0095] Example 24 Unlike Example 11, Ce-TBO 2Et Replace with [Fe(phtmeimb)2]PF6.

[0096] Comparative Example 1 Maintaining the same experimental procedure and device structure as in Example 1, only the Ce-TBO light-emitting layer was modified. 2Et A thermally activated sensitized fluorescent (TSF) device was fabricated using 3,5-bis(9H-carbazol-9-yl)-2,6-bis(3,6-diphenyl-9H-carbazol-9-yl)-5'-phenyl-[1,1':3',1''-terphenyl]-4-nitrile (HDT-1). The resulting device exhibited a turn-on voltage of 3.0 V under DC driving, a maximum external quantum efficiency of 27.0%, a maximum luminance of 15698 candela per square meter, and color coordinates of (0.15, 0.20). At a luminance of 1000 candela per square meter, the external quantum efficiency was 20.0%.

[0097] Comparative Example 2 Maintaining the same experimental procedure and device structure as in Example 1, only the Ce-TBO light-emitting layer was modified. 2EtA phosphorescent photofluorescent (PSF) device was fabricated using 3,5-bis(9H-carbazol-9-yl)-2,6-bis(3,6-diphenyl-9H-carbazol-9-yl)-5'-phenyl-[1,1':3',1''-terphenyl]-4-nitrile (PtON-TBBI). The resulting device exhibited a turn-on voltage of 3.5 V under DC driving, a maximum external quantum efficiency of 29.5%, a maximum luminance of 6083 candela per square meter, and color coordinates of (0.13, 0.10). At a luminance of 1000 candela per square meter, the external quantum efficiency was 20.6%.

[0098] Comparative Example 3 Maintaining the same experimental procedure and device structure as in Example 7, only the Ce-TBO light-emitting layer was modified. 2Et A TSF device was fabricated using bis[4-(9,9-dimethyl-9,10-dihydroacrylidine)phenyl]sulfone (DMAC-DPS). The resulting device had a turn-on voltage of 3.6 V under DC driving, a maximum external quantum efficiency of 14.6%, a maximum luminance of 16750 candela per square meter, and color coordinates of (0.37, 0.48). When the luminance was 1000 candela per square meter, the external quantum efficiency was 11.9%.

[0099] Comparative Example 4 Maintaining the same experimental procedure and device structure as in Example 7, only the Ce-TBO light-emitting layer was modified. 2Et A TSF device was fabricated using 2,3,4,5,6-penta(3,6-di-tert-butyl-9-carbazolyl)-benzonitrile (5TCzBN). The resulting device exhibited a turn-on voltage of 3.2 V under DC drive, a maximum external quantum efficiency of 19.6%, a maximum luminance of 19690 candela per square meter, and color coordinates of (0.33, 0.45). At a luminance of 1000 candela per square meter, the external quantum efficiency was 15.4%.

[0100] Comparative Example 5 Maintaining the same experimental procedure and device structure as in Example 7, except that the TBRb of the emitting layer is replaced with a df transition rare earth complex (Eu(Tp)). 2Et )2) Fabricate a single-emitting-layer white light device. Among them, the df transition rare-earth complex (Eu(Tp)) 2Et The structure of )2) is shown below:

[0101] The obtained device has a turn-on voltage of 4.2 volts under DC voltage drive, a maximum external quantum efficiency of 15.9%, a maximum luminance of 19,300 candela per square meter, and color coordinates of (0.33, 0.39). When the luminance is 1,000 candela per square meter, the external quantum efficiency is 13.8%.

[0102] Table 1. Summary of device performance in Examples 1-9 and Comparative Examples 1-5

[0103] in, a (%) represents the external quantum efficiency at maximum external quantum efficiency / 1000 candela per square meter.

[0104] Combination Figures 1-10 Analysis of the device characterization test results in Table 1 shows that: The double-line state sensitized fluorescence DSF narrowband OLED proposed and implemented based on df transition Ce(III) complexes (Examples 1-6) can not only achieve high performance and high color purity deep blue light emission, but also has a significantly better efficiency roll-off than thermally activated sensitized fluorescence (Comparative Example 1) and phosphorescent sensitized fluorescence (Comparative Example 2) devices prepared under the same conditions. This successfully verifies the possibility and great potential of double-line state sensitized fluorescence based on df transition Ce(III) complexes in realizing efficient, stable and wide color gamut OLEDs. Double-line sensitized fluorescent warm white OLEDs based on df-transition Ce(III) complexes (Examples 7-9) exhibit excellent color coordinate stability due to their rapid exciton utilization. The resulting single-emitting-layer warm white OLEDs show variations in x and y values ​​of color coordinates less than 0.01 within a brightness range of 1000 to 10000 candela per square meter. Furthermore, the external quantum efficiency reaches 20.2%, superior to Comparative Examples 1 and 2 (single-emitting-layer white light devices fabricated using TADF and TBRb fluorescent materials) and Comparative Example 3 (single-emitting-layer white light devices fabricated using df-transition Ce(III) and Eu(II) complexes). This demonstrates the possibility and great potential of double-line sensitized fluorescence based on df-transition Ce(III) complexes in achieving highly efficient and stable single-emitting-layer warm white OLEDs.

[0105] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism, characterized in that, Includes a light-emitting layer; the light-emitting layer is made of a first organic compound, a second organic compound, and a third organic compound; The first organic compound is a hole-type material, an electronic material, a mixture of hole-type and electronic materials, or a traditional donor-acceptor thermally activated delayed fluorescence host material; The first triplet state of the first organic compound ( T 1) The energy level must be higher than the first doublet state of the second organic compound ( D 1) Energy level; the first singlet state of the conventional donor-acceptor thermally activated delayed fluorescence host material ( S 1) Energy levels and T The energy difference between the first and second energy levels is less than or equal to 200 mV; The second organic compound is an organic compound with doublet luminescence properties, and the second organic compound's D The energy level 1 is higher than that of the third organic compound. S 1 energy level; The third organic compound is a traditional fluorescent material, a phosphorescent material, or a thermally activated delayed fluorescence material with multiple resonances.

2. The organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to claim 1, characterized in that, The hole-type material is TCTA, mCBP, CzSi, mCP, SiCzCz, or D-SiCzCz; the electron-type material is PPF, TSPO1, DPEPO, SiTrzCz2, or D-SiTrzCz2; the traditional donor-acceptor thermally activated delayed fluorescence host material is HTD-1, DMAC-DPS, DMAC-TRz, 4TCzBN, 4TCzPhBN, TTSA, 5TCzBN, or 5CzBN-D. The organic compound exhibiting doublet luminescence properties is a Ce(III) complex with df transition, and the Ce(III) complex with df transition is Ce-1, Ce-2, 3-Me, 1, 2-Me, 4-Pz, 4- n Bu、4- i Pr or Ce-TBO 2Et ; The conventional fluorescent material is Rubrene, TBRb, or DCJTB; The phosphorescent material is Ir(ppy)2(acac), Ir(dmppyph)2tmd, Ir(dpm)PQ2, PO-01, Ir(piq)3 or PtON-TBBI; The thermally activated delayed fluorescence material with multiple resonances is v -DABNA, o-Tol-ν-DABNA-Me or TBE02.

3. The organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to claim 1, characterized in that, When the first organic compound is a mixture of hole-type material and electronic-type material, the mass ratio of the hole-type material to the electronic-type material is 1:5 to 5:

1.

4. The organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to claim 1, characterized in that, Based on the total weight of the light-emitting layer, the doping concentration of the first organic compound is 67 wt% to 94.5 wt%, the doping concentration of the second organic compound is 5 wt% to 30 wt%, and the doping concentration of the third organic compound is 0.5 wt% to 3 wt%.

5. An organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to claim 1, characterized in that, Also includes: Substrate; An anode layer is disposed on the substrate; A hole injection layer is disposed on the anode layer; A hole transport layer is disposed on the hole injection layer; An electron blocking layer is disposed on the hole transport layer; The light-emitting layer is disposed on the electron blocking layer; A hole blocking layer is disposed on the light-emitting layer; An electron transport layer is disposed on the hole blocking layer; An electron injection layer is disposed on the electron transport layer; A metal cathode layer is disposed on the electron injection layer.

6. An organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to claim 5, characterized in that, The substrate is made of glass, quartz, polymer or metal. The anode is made of metal or indium tin oxide; The hole injection layer is made of HAT-CN, CuPc, MoO3 or V2O5 material; The hole transport layer is made of TAPC, TQTPA, NPB, BCFN, TPD, TCTA or mCP; Alternatively, the hole transport layer may be made of a mixture of HAT-CN and TAPC; The electron blocking layer is made of one or two of TCTA, CzSi, SiCzCz, CCP, BBSN and mCP; The hole blocking layer is made of DPEPO, PPF, TSPO1, Tm3PyP26PyB, PO-T2T, TmPyPB, TPBi or DPPyA; The electron transport layer is made of TSPO1, Tm3PyP26PyB, PO-T2T, TmPyPB, TPBi or DPPyA; The electron injection layer is made of LiF, Liq, Yb, Li2CO3 or Cs2CO3; The cathode layer is made of Al, Au, Ag or magnesium-aluminum alloy.

7. An organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to claim 6, characterized in that, When the hole transport layer is made of a mixture of HAT-CN and TAPC, the percentage of HAT-CN in the total mass of the hole transport layer is 0.05% to 0.5%.

8. An organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to claim 5, characterized in that, The hole injection layer has a thickness of 8-12 nm; the hole transport layer has a thickness of 30-60 nm; the electron blocking layer has a thickness of 5-15 nm; the light-emitting layer has a thickness of 15-25 nm; the hole blocking layer has a thickness of 5-15 nm; the electron transport layer has a thickness of 40-70 nm; the electron injection layer has a thickness of 0.8-1.5 nm; and the metal cathode layer has a thickness of 70-130 nm.

9. A method for fabricating an organic electroluminescent device based on a doublet-state sensitized fluorescence mechanism according to any one of claims 5 to 8, characterized in that, Includes the following steps: Provide a substrate with an anode layer; A hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a metal cathode layer are sequentially deposited on the anode layer. During the evaporation processes of the hole injection layer, the hole transport layer, the electron blocking layer, the light-emitting layer, the hole blocking layer, and the electron transport layer, a vacuum level of less than 2.0 × 10⁻⁶ is maintained. -5 Pa; the evaporation process of the electron injection layer and the metal cathode layer is carried out under a vacuum degree of less than 2.0 × 10⁻⁶. -5 The experiment was conducted under the condition of Pa.

10. The application of an organic electroluminescent device based on a doublet state sensitized fluorescence mechanism according to any one of claims 1 to 8 in display devices and lighting devices.

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