A self-sensitizing narrowband blue light material and its application

Abstract

This invention provides a self-sensitized blue light-emitting material with narrow-band emission characteristics. The material structure simultaneously comprises a blue photosensitizer with thermally activated delayed fluorescence properties and a blue phosphor with narrow-band emission characteristics. The distance and energy levels between the sensitizer and phosphor are matched to ensure efficient fluorescence resonance energy transfer. This type of small organic molecule exhibits a narrow emission half-width, strong blue fluorescence emission, high fluorescence quantum yield, and a small molecular weight, facilitating vacuum evaporation. When applied to organic electroluminescent devices, it can achieve pure blue photoluminescence (CIE y value less than 0.1), high current efficiency, external quantum efficiency, and low device efficiency roll-off.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials technology, specifically relating to a self-sensitized blue light material with narrow-band luminescence characteristics and its applications. Background Technology

[0002] Organic light-emitting diodes (OLEDs), employing an active-matrix emission mode and with their core functional layers composed entirely of organic materials, possess numerous advantages such as flexibility, thinness, vibrant colors, and low energy consumption, and have gradually developed into a new generation of flat panel display and lighting technology (Nat. Rev. Mater. 2018, 3, 18020). After nearly thirty years of development, OLED technology is now in mass production at numerous panel manufacturers and has been widely adopted in terminal display and lighting equipment. Currently, in terms of the three primary color emitting materials (red, green, and blue), red and green emitting materials have been iterated to the latest mature generation of thermally activated delayed fluorescence (TADF) materials, thus meeting the needs of current applications in terms of efficiency and stability. However, blue light materials still use traditional fluorescent materials, resulting in insufficient overall device performance. Although numerous blue TADF materials have been reported in literature and patents (Adv. Mater. 2021, 33, 2005630), due to the high energy of blue light materials, their stability, efficiency, and color purity still lag behind commercial applications. Blue light materials based on noble metal complexes have largely met industrialization requirements in terms of efficiency and lifespan, but they suffer from high costs and color purity that still cannot meet the demands of ultra-high-definition displays. The recently developed multiple resonance (MR) technology, which constructs fused heterocycles by arranging electron-deficient boron and electron-rich nitrogen in an alternating dislocation manner, can significantly narrow the emission spectrum and also possess TADF properties. However, such materials suffer from a large energy difference in their single triplet state (ΔE). ST The generally large value (>0.1eV) leads to its reverse intersystem jump rate (k RISC Excessively low exciton concentrations not only reduce exciton utilization but also lead to various quenching mechanisms caused by excessively high triplet exciton concentrations at high current densities, severely impacting the overall performance of the device. Introducing additional sensitizers into the emitting layer during device fabrication can largely alleviate these technical challenges, but it often results in poor matching between the sensitizer and phosphor, and low energy transfer efficiency, hindering the application of MR-TADF materials, especially blue MR-TADF materials, on production lines.

[0003] Based on the above reasons, this application is hereby submitted. Summary of the Invention

[0004] Based on the above reasons, and in view of the problems or defects existing in the prior art, the purpose of this invention is to provide a self-sensitized narrow-band blue light material and its application, to solve or at least partially solve the above-mentioned technical defects existing in the prior art: the new blue fluorescent material design concept provided by this invention combines the sensitization mechanism with multiple resonance thermally activated delayed fluorescence (MR-TADF) technology to construct a narrow-band blue light material with self-sensitization properties.

[0005] To achieve the first aspect of the present invention, the technical solution adopted by the present invention is as follows:

[0006] A self-sensitized narrow-band blue light material, wherein the molecular structure of the material contains both a sensitizer portion with thermally activated delayed fluorescence (TADF) properties and a blue light phosphor portion with narrow-band emission properties.

[0007] Furthermore, in the above technical solution, the molecular structure of the sensitizer portion with thermally activated delayed fluorescence characteristics is as shown in Formula 1 below: the sensitizer portion consists of a boron-oxygen fused heterocycle as the acceptor and an aromatic amine electron-rich body as the donor, with N atoms bridging the acceptor and donor. The parameters such as the singlet state, triplet state, and lowest unoccupied orbital (LUMO) of the sensitizer portion are adjusted by changing the type of substituent at the boron para-position (Y).

[0008]

[0009] Specifically, in the above technical solution, the sensitizer portion with thermally activated delayed fluorescence characteristics can be appropriately matched with the acceptor. Steric hindrance groups can be appropriately introduced on the aromatic amine unit to ensure effective separation of the frontier orbitals between the acceptor and the acceptor, as well as a small singlet-triplet energy difference and rapid reverse intersystem crossing.

[0010] Furthermore, in the above technical solution, the molecular structure of the blue phosphor with narrow-band emission characteristics is as shown in one of the following formulas: it is composed of fused heterocyclic aromatic hydrocarbons and their derivatives with boron, nitrogen, nitrogen, oxygen, or boron, nitrogen, and sulfur arranged in a misaligned manner and having multiple resonance characteristics.

[0011]

[0012] Specifically, in the above technical solution, the energy levels of the sensitizer and the fluorescent agent in the self-sensitized narrow-band blue light material molecule are matched, meaning the lowest singlet state energy level of the sensitizer is higher than that of the fluorescent agent; the distance is moderate, meaning the spatial distance between the sensitizer and the fluorescent agent should not be too far, but should be within the effective range that can produce efficient fluorescence resonance energy transfer, so as to achieve efficient intramolecular fluorescence resonance energy transfer. energy transfer).

[0013] Furthermore, in the above technical solution, the self-sensitizing narrow-band blue light material has the molecular structure shown in Formula 3 below, where: Ar is an aryl group, such as a benzene ring or biphenyl; X is an O, S, or a monoaryl-substituted N; Y is a modifying substituent such as methyl, trifluoromethyl, tert-butyl, isopropyl, phenoxy, fluoro, etc.; and L is a conjugated bridging unit.

[0014]

[0015] Preferably, in the above technical solution, the structure of the self-sensitized narrow-band blue light material can be, but is not limited to, the composition or combination of the following formula four:

[0016]

[0017]

[0018]

[0019] Specifically, the above technical solution describes a self-sensitized narrow-band blue light material with narrow-band blue light emission (CIEy value less than 0.1), high fluorescence quantum yield, and small molecular weight. It can be applied to organic electroluminescent devices to obtain efficient and high-color-purity electroluminescent blue light emission.

[0020] On the other hand, the present invention provides the application of the above-described self-sensitized narrow-band blue light material as a guest light-emitting layer in organic electroluminescent devices.

[0021] The present invention provides an organic electroluminescent device, wherein at least one functional layer of the organic electroluminescent device comprises at least one of the self-sensitized narrow-band blue light-emitting materials as described above.

[0022] Preferably, the functional layer of the organic electroluminescent device includes a light-emitting layer, which contains at least one of the self-sensitized narrow-band blue light-emitting materials described above.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The organic small molecule compound of the present invention simultaneously possesses self-sensitization effect and high-efficiency narrow-band blue light emission (CIEy value less than 0.1), which solves the problems of low color purity, low luminous efficiency and severe device efficiency roll-off caused by the single function of current conventional blue light emitting materials. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Appendix Table 1 shows the optimized structural configurations of the self-sensitized narrowband blue light material molecules SSBD-1, SSBD-19, SSBD-21, and SSBD-34 prepared in Examples 1-4.

[0027] Appendix Table 2 shows the LUMO+1, LUMO, HOMO, and HOMO-1 orbital distributions of the self-sensitized narrowband blue light material molecule SSBD-1 prepared in Example 1;

[0028] Appendix Table 3 shows the LUMO+1, LUMO, HOMO, and HOMO-1 orbital distributions of the self-sensitized narrowband blue light material molecule SSBD-19 prepared in Example 2;

[0029] Appendix Table 4 shows the LUMO+1, LUMO, HOMO, and HOMO-1 orbital distributions of the self-sensitized narrowband blue light material molecule SSBD-21 prepared in Example 3;

[0030] Appendix Table 5 shows the LUMO+1, LUMO, HOMO, and HOMO-1 orbital distributions of the self-sensitized narrowband blue light material molecule SSBD-34 prepared in Example 4.

[0031] Appendix 6 is a summary table of key data for the top-emitting organic light-emitting devices in Application Example 1, Application Example 3, and Comparative Application Example 1 and Comparative Application Example 2;

[0032] Appendix Figure 1 This is a schematic diagram of the top-emitting organic electroluminescent device structure in Application Example 1;

[0033] Appendix Figure 2 Comparison of electroluminescence spectra of top-emission organic electroluminescent devices in Application Example 1 (based on SSBD-1 emitting layer guest) and Comparative Application Example 1 (based on Pt-1 emitting layer guest) and Comparative Application Example 2 (based on BN-1 emitting layer guest);

[0034] Appendix Figure 3 Current-voltage-brightness curves of the device's analog-to-digital converter (ADC);

[0035] Appendix Figure 4 Power efficiency and current efficiency versus brightness curves of the device AD. Detailed Implementation

[0036] This invention provides a self-sensitized blue light-emitting material with narrow-band emission characteristics. The material has the chemical structure shown in Formula 3. This structure simultaneously comprises a blue light sensitizer with thermally activated delayed fluorescence characteristics and a blue phosphor with narrow-band emission characteristics. The distance and energy levels between the sensitizer and the phosphor are matched to ensure efficient fluorescence resonance energy transfer (FRET). (Energy transfer). These small organic molecules possess narrow emission half-width, strong blue fluorescence, high fluorescence quantum yield, and small molecular weight, which facilitates vacuum evaporation. When applied to organic electroluminescent devices, they can achieve pure blue photoluminescence (CIE y value less than 0.1), as well as high current efficiency, external quantum efficiency, and low device efficiency roll-off.

[0037] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be considered as specific limitations thereof. Regarding the 36 structures listed in Formula 4, and considering their respective structural characteristics, four different types of embodiments are provided below to illustrate the technical solution of the present invention. It should be noted that, based on the four embodiments provided by the present invention, it is natural to associate them with the 36 molecular structural formulas listed in Formula 4 above.

[0038] Example 1

[0039] As shown in Formula 5, the self-sensitizing narrow-band blue light material (SSBD-1) of this embodiment is prepared by the following method, including the following steps:

[0040] 2-Bromo-1,3-dimethyl-9H-carbazole (20 mmol), aniline (21 mmol), tris(dibenzylacetone)dipalladium Pd2(dba)3 (0.4 mmol, 2% catalytic amount), sodium tert-butoxide (22 mmol), and tri-tert-butylphosphine tetrafluoroborate (0.8 mmol) were placed in a 150 mL two-necked flask. After three purging cycles, 80 mL of ultra-dry toluene was injected under nitrogen protection using a syringe. The mixture was refluxed at 110 °C for 48 h. After cooling, the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane 2:1) to obtain a brownish-yellow solid, which was used directly in the next reaction without further identification. The collected brownish-yellow powder was placed in a 150 mL two-necked flask, and equimolar amounts of 5-bromo-2-chloro-1,3-m-diphenyl ether, 2% catalytic amount of Pd2(dba)3, sodium tert-butoxide, and tri-tert-butylphosphine tetrafluoroborate were added successively. After deoxygenation treatment, 60 mL of ultra-dry toluene was injected into the system using a syringe, and the mixture was refluxed overnight at 110 °C. After cooling, the solvent was evaporated under reduced pressure to obtain the crude product, which was then purified by silica gel column chromatography (eluting agent: petroleum ether / dichloromethane 3:1) to obtain a yellowish-brown solid 1, i.e., intermediate 1, with a yield of 65%. HRMS (ESI) theoretical calculation C 38 H 29 ClN2O2, [M] + 580.1918; the measured value is 580.1921.

[0041] Intermediate 1 (10 mmol), 3-bromo-2-chloro-N,N-diphenylaniline (11 mmol), tris(dibenzylacetone)dipalladium Pd2(dba)3 (0.2 mmol, 2% catalytic amount), sodium tert-butoxide (11 mmol), and tri-tert-butylphosphine tetrafluoroborate (0.4 mmol) were placed in a 100 mL round-bottom flask, purged three times, filled with argon gas, and then injected with 40 mL of ultra-dry toluene. The mixture was refluxed overnight at 110 °C. After cooling, the solvent was evaporated under reduced pressure to obtain the crude product, which was then purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane 4:1) to obtain a pale yellow solid 2, i.e., intermediate 2, with a yield of 58%. HRMS (ESI) theoretical calculation C 56 H 39 BClN3O2, [M] + 831.2824; measured value is 831.2829.

[0042] 5 mmol of intermediate 2 was placed in a 100 mL screw-top pressure-resistant flask. After three purgings, argon gas was refilled. Then, 30 mL of ultra-dry tricresylbenzene was added, and the system was cooled to -40 °C. At this temperature, tert-butyllithium (16.2 mL, 15 mmol, 0.93 M) was slowly added dropwise. The temperature was slowly raised to 80 °C, and the reaction was carried out for 3–5 hours. Then, the system was further cooled to an ice bath, and boron tribromide (30 mmol) was added. The mixture was stirred overnight at room temperature, and then N2 was added. N,N-diisopropanolamine (30 mmol) was added, and the mixture was heated to 180 °C for 24 hours. After cooling to room temperature, an appropriate amount of N,N-diisopropanolamine was added to quench the reaction. The mixture was extracted with a dichloromethane / water mixed solvent, and the organic phases were combined. The organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was then subjected to silica gel column chromatography (eluting agent: petroleum ether / dichloromethane, 3:1), recrystallized (toluene / isopropanol), and sublimed to obtain a white pure product SSBD-1 (yield 26%). HRMS (ESI) theoretical calculation C 56 H 37 B2N3O2, [M] + 805.3072; measured value is 805.3068. 1 H NMR(500MHz,Chloroform-d)δ9.05–9.02(m,1H),8.87–8.83(m,1H),8.46–8.40( m,1H),8.13(dd,J=7.4,1.1Hz,1H),7.71(dd,J=7.5,1.9Hz,4H),7.46–7.38(m,3H ),7.37–7.22(m,6H),7.22–7.12(m,2H),7.09–7.05(m,2H),7.03–6.88(m,8H),6. 57(dd,J=7.5,1.9Hz,1H),6.51(dd,J=7.5,1.9Hz,1H),2.45(s,3H),2.41(s,3H).

[0043]

[0044] Example 2

[0045] As shown in Formula 6, a self-sensitizing narrow-band blue light material (SSBD-19) of this embodiment is prepared by the following method, including the following steps:

[0046] 1-Bromo-5-chloro-2-phenoxy-9-phenyl-9H-carbazole (10 mmol) was placed in a 100 mL screw-top pressure-resistant flask. After three purgings, argon gas was introduced, followed by the addition of 20 mL of ultra-dry thallium. The system was cooled to -40 °C, and n-butyllithium (5.33 mL, 12 mmol, 2.25 M) was slowly added dropwise at this temperature. The temperature was slowly increased to 80 °C, and the reaction was allowed to proceed for 3–5 hours. The system was then further cooled to an ice bath, and boron tribromide (1... 5 mmol), stirred overnight at room temperature, then N,N-diisopropanolamine (15 mmol), heated to 180 °C and reacted for 24 hours. After cooling to room temperature, an appropriate amount of N,N-diisopropanolamine was added to quench the reaction. Extraction was performed with a dichloromethane / water mixed solvent. The organic phases were combined, and the organic solvent was removed by vacuum distillation to obtain the crude product. Then, silica gel column chromatography (eluent: petroleum ether / dichloromethane, 3:1) was performed to obtain a pale yellow solid 3, i.e., intermediate 3, with a yield of 58%.

[0047] Intermediate 3 (5 mmol), aniline (5 mmol), tris(dibenzylacetone)dipalladium Pd2(dba)3 (0.2 mmol, 2% catalytic amount), sodium tert-butoxide (11 mmol), and tri-tert-butylphosphine tetrafluoroborate (0.4 mmol) were placed in a 100 mL round-bottom flask, purged three times, filled with argon gas, and then injected with 40 mL of ultra-dry toluene. The mixture was refluxed overnight at 110 °C. Then, a bromoboroxyhexacyclic aromatic hydrocarbon intermediate (6 mmol) was added, and the reaction was continued at 110 °C for 24 hours. After cooling, the solvent was evaporated under reduced pressure to obtain the crude product, which was then purified by silica gel column chromatography (eluting agent: petroleum ether / dichloromethane 4:1) to obtain a pale yellow solid SSBD-19 (yield 48%). HRMS (ESI) theoretical calculation C 48 H 28 B2N2O3, [M] + 702.2286; measured value is 702.2293. 1 H NMR(500MHz,Chloroform-d)δ9.06–8.97(m,4H),8.29–8.21(m,2H),7.89(dd,J=7.5,1.9Hz,1H),7.71(dd,J=7.5, 1.9Hz,3H),7.56(td,J=7.4,2.0Hz,1H),7.40–7.18–7.10(m,9H),7.04–6.91(m,6H),6.78(dd,J=13.1,1.8Hz,2H).

[0048]

[0049] Example 3

[0050] As shown in Formula 7, a self-sensitizing narrow-band blue light material (SSBD-21) of this embodiment is prepared by the following method, including the following steps:

[0051] Spirobiacin (10 mmol), 5-bromo-2-chlorodi-m-methylphenoxyhalogen precursor (10 mmol), tris(dibenzylacetone)dipalladium Pd2(dba)3 (0.4 mmol, 2% catalytic amount), sodium tert-butoxide (22 mmol), and tri-tert-butylphosphine tetrafluoroborate (0.8 mmol) were placed in a 100 mL two-necked flask. After three purging cycles, 50 mL of ultra-dry toluene was injected under nitrogen protection using a syringe. The mixture was refluxed at 110 °C for 12 h. Then, another haloalkane precursor (2-chloro-3-bromo-triphenylamine, 12 mmol) was added under argon atmosphere, and the reaction was continued for 24 h. After cooling, the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane 4:1) to obtain yellow intermediate 4.

[0052] Take intermediate 4 (3 mmol) and place it in a 50 mL screw-top pressure-resistant bottle. After purging three times, refill with argon gas, then add 10 mL of ultra-dry tricresylbenzene. Cool the system to -40 °C, and slowly add tert-butyllithium (12.9 mL, 12 mmol, 0.93 M) dropwise at this temperature. Slowly raise the temperature to 80 °C and react for 3-5 hours. Then continue to cool to an ice bath, add boron tribromide (15 mmol), stir overnight at room temperature, then add N,N-diisopropanolamine (15 mmol), raise the temperature to 180 °C and react for 24 hours. After cooling to room temperature, add an appropriate amount of N,N-diisopropanolamine to quench the reaction, extract with dichloromethane / water mixed solvent, combine the organic phases, remove the organic solvent by vacuum distillation to obtain crude product, then perform silica gel column chromatography (eluting agent: petroleum ether / dichloromethane, 3:1), recrystallize, and sublimate to obtain pale yellow pure product SSBD-21 (yield 18%). HRMS (ESI) theoretical calculation C 63 H 41 B2N3O2, [M] + 893.3385; the measured value is 893.3392. 1 H NMR(500MHz,Chloroform-d)9.05–8.94(m,4H),8.33–8.24(m,2H),δ7.79–7.75(m,2H),7.74–7.58(m,5H),7.52(dd,J=7.4,1.9Hz,1H),7 .48–7.34(m,6H),7.27–6.90(m,12H),6.58(dd,J=7.5,1.9Hz,1H),5.76(dd,J=7.5,1.9Hz,1H),5.58(dd,J=7.5,1.9Hz,1H),2.35(s,6H).

[0053]

[0054] Example 4

[0055] As shown in Formula 8, a self-sensitizing narrow-band blue light material (SSBD-34) of this embodiment is prepared by the following method, including the following steps:

[0056] 2-Bromo-1-chloro-12-phenyl-11,12-diH-indole[2,3-a]carbazole (10 mmol), diphenylamine (11 mmol), tris(dibenzylacetone)dipalladium Pd2(dba)3 (0.4 mmol, 2% catalytic amount), sodium tert-butoxide (22 mmol), and tri-tert-butylphosphine tetrafluoroborate (0.8 mmol) were placed in a 100 mL two-necked flask. After three purging cycles, 50 mL of ultra-dry toluene was injected under nitrogen protection using a syringe. The mixture was refluxed at 110 °C for 12 h. Then, another haloalkane precursor (5-bromo-2-chlorodi-m-methylphenoxy haloalkane precursor, 12 mmol) was added under argon atmosphere, and the reaction was continued for 24 h. After cooling, the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane 4:1) to obtain yellow intermediate 5.

[0057] Take intermediate 5 (3 mmol) and place it in a 50 mL screw-top pressure-resistant bottle. After purging three times, refill with argon gas, then add 10 mL of ultra-dry tricresylbenzene. Cool the system to -40°C, and at this temperature, slowly add tert-butyllithium (12.9 mL, 12 mmol, 0.93 M) dropwise. Then slowly raise the temperature to 80°C and continue the reaction for 3–5 hours. Then cool it again to an ice bath, add boron tribromide (15 mmol), and stir overnight at room temperature. Then, N,N-diisopropanolamine (15 mmol) was added, and the mixture was heated to 180°C and reacted for 24 hours. After cooling to room temperature, an appropriate amount of N,N-diisopropanolamine was added to quench the reaction. The mixture was extracted with a dichloromethane / water mixed solvent, and the organic phases were combined. The organic solvent was removed by vacuum distillation to obtain the crude product. The crude product was then subjected to silica gel column chromatography (eluent: petroleum ether / dichloromethane, 3:1), recrystallized, and purified by sublimation to obtain a pale yellow pure product, SSBD-34 (yield 15%). HRMS (ESI) theoretical calculation C 54 H 31 B2N3O2, [M] + 775.2602; the measured value is 775.2608. 1H NMR(500MHz,Chloroform-d)δ9.06–8.96(m,4H),8.79(dd,J=7.5,1.2Hz,1H),8.23(dd,J=7.4,1.1Hz,1H),8.06(dd,J=7.5,1.9Hz,1H),7.71(dd ,J=7.5,1.9Hz,3H),7.66–7.55(m,2H),7.39(dd,J=7.5,1.9Hz,1H),7.3 4–7.12(m,8H),7.12–7.05(m,4H),7.04–6.97(m,3H),7.00–6.86(m,3H).

[0058]

[0059] Theoretical simulation:

[0060] Furthermore, to elucidate the superiority of the self-sensitizing narrow-band blue light material of this invention, theoretical simulation data of key molecular parameters based on Gaussian 16 software are provided below. The optimization of the ground state configuration is based on the B3LYP / def2-svp level, and then TD-DFT calculations are performed based on this optimized configuration. The visualization of the frontier orbitals is based on Gaussview 6.0 software.

[0061] Calculations revealed that the optimized molecular configurations of SSBD-1, SSBD-19, SSBD-21, and SSBD-34 exhibit tunable spatial distances between the sensitizer and fluorophore fragments, thereby achieving effective fluorescence resonance energy transfer. Lateral and longitudinal comparisons in Appendices 2-4 showed that all these self-sensitized blue light molecules possess relatively separated LUMO+1, LUMO, HOMO, and HOMO-1 orbitals. This allows for diverse electronic transitions, including charge-transfer transitions to produce smaller singlet triplet energy differences, and also lower-energy multiple resonance transitions, achieving narrow-band blue light emission.

[0062] Application Example 1

[0063] The self-sensitized narrowband blue light material SSBD-1 prepared in Example 1 was used as a light-emitting guest in a vapor-deposited, top-emission organic light-emitting device (corresponding to device C). The device includes at least the following components arranged sequentially from bottom to top: Figure 1 The film structure shown is as follows: anode layer 100, hole injection layer 101, hole transport layer 102, light-emitting layer 103, electron transport layer 104, electron injection layer 105, cathode layer 106, and capping layer 107; wherein:

[0064] The anode layer 100 is made of indium tin oxide (ITO).

[0065] The hole injection layer 101 has a thickness of 10 nm and is made of 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene (HAT-CN).

[0066] The hole transport layer 102 has a thickness of 60 nm and is made of N,N'-diphenyl-N,N'-di(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (α-NPB).

[0067] The luminescent layer 103 has a thickness of 40 nm and is made of 1,3-bis(9H-carbazole-9-yl)benzene (mCP) and a luminescent layer guest. The mass ratio of mCP to the luminescent layer guest is 90:10. The luminescent layer guest is the self-sensitized narrow-band blue light material SSBD-1 prepared in Example 1.

[0068] The electron transport layer 104 has a thickness of 40 nm and is made of 1,3,5-tris(3-(3-pyridyl)phenyl)benzene Tm3PyPB.

[0069] The electron injection layer 105 has a thickness of 1 nm and is made of lithium fluoride (LiF).

[0070] The cathode layer 106 has a thickness of 20 nm and is made of magnesium (Mg) and silver (Ag) mixed in a weight ratio of 9:1.

[0071] The cover layer 107 has a thickness of 60 nm and is made of N. 4 N 4 N 4 ',N 4 '-Tetra([1,1'-biphenyl]-4-yl)-[1,1'-biphenyl]-4,4'-diamine (CPL).

[0072] Application Example 2

[0073] This application embodiment is basically the same as application embodiment 1, except that the light-emitting layer guest used in this application embodiment is the self-sensitized narrow-band blue light material SSBD-21 prepared in embodiment 3, corresponding to device code D.

[0074] Comparative Application Example 1

[0075] This comparative example is basically the same as Application Example 1, except that the guest light-emitting layer used in this comparative example is the classic platinum group metal complex blue light-emitting material Pt-1 (N-(3,5-di-tert-butyl)-N-3-phenoxy-phenylbenzimidazole carbazole tert-butylphenyl platinum complex), corresponding to device number B.

[0076] Comparative Application Example 2

[0077] This comparative example is basically the same as Application Example 1, except that the light-emitting layer guest used in this comparative example is BN-1 (5,9-diphenyl-5,9-dihydro-5,9-diaza-13b-boronatholo[3,2,1-de]anthracene), corresponding to device number A.

[0078] The structure of the materials involved in the above application examples and comparative application examples is shown in Equation Nine below:

[0079]

[0080] Appendix Table 1 shows the optimized structural configurations of the self-sensitized narrowband blue light-emitting materials SSBD-1, SSBD-19, SSBD-21, and SSBD-34 prepared in Examples 1-4. The results in Appendix Table 1 show that the sensitizer and phosphor motifs of SSBD-1, SSBD-19, SSBD-21, and SSBD-34 corresponding to Examples 1-4 exhibit suitable spatial distances, avoiding strong π-π interactions between them. It also falls within the effective range of fluorescence resonance energy transfer. This ensures efficient self-sensitization and narrow-band blue fluorescence.

[0081] Appendix Tables 2-5 present the orbital distributions of LUMO+1, LUMO, HOMO, and HOMO-1 for the SSBD-1, SSBD-19, SSBD-21, and SSBD-34 molecules corresponding to Examples 1-4. Clearly, these four energy levels are highly correlated with self-sensitization and narrow-band emission. First, the separated HOMO and LUMO orbitals help ensure a small singlet triplet energy difference, thereby ensuring a high reverse intersystem crossing rate in the sensitizer and high exciton utilization in the device. Second, the partial overlap of the HOMO-1 and LUMO regions, as well as the complete atomic separation of LUMO+1 and HOMO (multiple resonance characteristics), ensures the narrow bandgap of the phosphor and strong blue light emission.

[0082] Appendix Table 6 is a summary table of key data for the top-emission organic electroluminescent devices in Application Example 1, Application Example 2, and Comparative Application Example 1 and Comparative Application Example 2. Among them: photoluminescent quantum yield was measured using the absolute quantum yield method under argon gas conditions, based on the Quantaurus-QY testing system (C9920-02, Hamamatsu Photonics); the effective area of ​​all devices was 0.09 cm². 2The current-voltage curves and electroluminescence spectra of all devices were measured using a Keithley 2400 and a PHOTO RESEARCH SpectraScan PR 735 spectrometer, respectively. The external quantum efficiency was calculated based on the current density, brightness, and electroluminescence spectra.

[0083] Appendix 6 and Appendix Figure 2-4 The device results presented show that, compared with the comparative embodiments, the device performance is significantly improved when using the material provided by the present invention as the guest light-emitting layer. Specifically, the emission full width at half maximum (FWHM) is narrowed (~12 nm), the CIE coordinates (y~0.05) are closer to the blue light requirements of BT2020, the photofluorescence quantum yield (PLQY) is higher (close to 100%), and the current efficiency, power efficiency, and external quantum efficiency are improved by nearly 50% or more. In addition, the efficiency roll-off is also reduced at 1000 cd m 2 The roll-off value at standard brightness is only around 5%. The improvement in device performance is mainly due to the advantages of the material design technology of this invention. The efficient matching of sensitizer and phosphor not only ensures the improvement of exciton utilization and effectively suppresses the accumulation of triplet excitons, but also ensures efficient fluorescence resonance energy transfer and narrow-band blue light emission.

[0084] In summary, it is clear that compared to the second-generation platinum-based blue light materials that are about to be put into production, as well as the conventional boron-nitrogen fused heterocyclic blue light materials, the self-sensitized narrow-band blue light material provided by this invention has significant technical advantages: firstly, it has a narrower maximum half-width at half-maximum (WHM) of the emission spectrum (~12nm), making it easier to achieve ultra-high-definition display with a wide color gamut (CIE y value less than 0.1); secondly, the current efficiency and power efficiency of the device are also significantly improved.

[0085] The applicant declares that this invention illustrates a self-sensitizing narrow-band blue light material and its application through the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

[0086] Appendix 1

[0087]

[0088] Appendix 2

[0089]

[0090] Appendix 3

[0091]

[0092] Appendix 4

[0093]

[0094] Appendix 5

[0095]

[0096] Appendix 6

[0097]

Claims

1. A self-sensitizing narrow-band blue material, characterized by: The structure of the self-sensitizing narrow-band blue light material is any one or more of the following Formula IV:

2. The self-sensitizing narrow-band blue material according to claim 1, characterized in that: The self-sensitizing narrow-band blue light material has a narrow-band blue light emission, wherein the CIE y value is less than 0.

1.

3. Use of the self-sensitizing narrow-band blue light material of claim 1 as a guest in a light-emitting layer in an organic electroluminescent device.

4. An organic electroluminescent device, characterized by: At least one functional layer of the organic electroluminescent device comprises at least one of the self-sensitizing narrow-band blue light materials of claim 1.

5. The organic electroluminescent device according to claim 4, characterized in that: The functional layer of the organic electroluminescent device comprises a light-emitting layer, and the light-emitting layer comprises at least one of the self-sensitizing narrow-band blue light materials of claim 1.

Images