Near-ultraviolet hot exciton luminescent material based on multiple resonance electron donor and acceptor units and application

Abstract

The application belongs to the technical field of light emitting and display, and particularly discloses a near-violet thermal exciton luminescent material based on multiple resonance electron donor and acceptor units and application. The luminescent material takes 2,12-di-tert-butyl-5,9-diox-13b-boron naphtho[3,2,1-de] anthracene as an electron acceptor unit, and 2,5-di-tert-butyl indole [3,2,1-jk] carbazole as an electron donor unit. The two rigid MR donor and acceptor units are directly connected through a sigma bond, forming a small-angle dislocation non-coplanar structure, effectively inhibiting concentration quenching and red shift of the luminescent spectrum; meanwhile, the combination of the two MR units promotes the reverse intersystem crossing of the high-level triplet state to the degenerate singlet state (T6→S1 / S2), realizing efficient, narrow spectral band near-violet light emission of the material. The luminescent efficiency of the preferred solution processing organic light emitting device is as high as 12.01%, and has an attractive application prospect.

Description

Technical Field

[0001] This invention belongs to the field of light emission and display technology, and specifically discloses a near-ultraviolet photothermal exciton light-emitting material based on multiple resonant electron donor and acceptor units and its application. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have broad application prospects in ultra-high-definition (UHD) displays such as mobile phones, televisions, and instruments due to their advantages of light weight, thinness, high brightness, wide viewing angle, high color contrast, and flexible display capabilities. Currently, high-efficiency OLEDs are generally fabricated using vacuum deposition technology. Red, green, and blue OLEDs are already commercialized, but near-ultraviolet OLEDs still lag behind in luminous efficiency and color purity. The main reasons for this are:

[0003] (1) The wide bandgap of near-ultraviolet luminescent materials is not conducive to achieving high luminous efficiency;

[0004] (2) The lower HOMO energy level and higher LUMO energy level of near-ultraviolet luminescent materials are not conducive to carrier injection and the improvement of luminous efficiency. Furthermore, the modulation of energy levels will enhance the charge transfer (CT) transition between electron donor and acceptor units, resulting in a red shift in the material's emission and a broadening of the spectral band. This makes it difficult to meet the near-ultraviolet color coordinates (0.131, 0.046) standard specified in the latest color standard for UHD display of the International Commission on Illumination (CIE) Rec.2020. This poses a greater challenge to near-ultraviolet luminescent materials.

[0005] Pure organic thermally exciton-luminescent materials possess rapid high-order reverse intersystem crossing (hRISC) channels, enabling efficient utilization of triplet excitons through hybrid local charge transfer (HLCT) excited states and emission via locally excited (LE) states. This avoids the significant redshift emission of traditional thermally activated delayed fluorescence (TADF) materials, representing a promising direction for the development of commercial near-ultraviolet (NIUV) materials. CT state perturbation is the most effective method for constructing thermally exciton-luminescent materials; however, traditional CT state perturbation, achieved by introducing electron donor and acceptor units, struggles to control the CT transition intensity, leading to undesirable low luminescence efficiency and broad emission peaks. Therefore, exploring suitable electron donor and acceptor unit matching strategies and developing novel NIUV thermally exciton-luminescent materials based on electron donor and acceptor units is crucial for improving the luminescence efficiency and color purity of NIUV luminescent materials. Summary of the Invention

[0006] To address the issues of luminescence efficiency and color purity in near-ultraviolet (NIUV) luminescent materials, this invention designs a NIUV thermal exciton luminescent material composed of electron donor and acceptor units with multiple resonance (MR) characteristics. This NIUV luminescent material contains two simple rigid MR framework units: one is a boron / oxygen (B / O) heterocyclic aromatic hydrocarbon electron acceptor unit, namely 2,12-di-tert-butyl-5,9-dioxa-13b-boronaphtho[3,2,1-de]anthracene; the other is a nitrogen heterocyclic aromatic hydrocarbon electron donor unit, namely 2,5-di-tert-butylindole[3,2,1-jk]carbazole.

[0007] The near-ultraviolet photothermal exciton luminescent material based on multiple resonant electron donor and acceptor units provided by this invention has the structural features shown in formula (1):

[0008]

[0009] This near-ultraviolet luminescent material has the following significant structural characteristics:

[0010] (1) Both indole-carbazole and B / O heterocyclic aromatic units have rigid plane, MR effect and short-range CT effect, which are beneficial to reduce vibrational behavior and promote radiative transition.

[0011] (2) Indolecarbazole and B / O heterocyclic aromatic hydrocarbons have relatively moderate electron-donating and electron-accepting capabilities, which are conducive to forming a weak CT effect of the acceptor unit and avoiding emission redshift.

[0012] (3) Indobenzocarbazole is a structural unit with high stability and easy functionalization. It can be directly connected with B / O heterocyclic aromatic units through σ bonds to form a non-coplanar structure with small-angle dislocation, which is beneficial to suppress concentration quenching and reduce efficiency roll-off.

[0013] (4) Rigid B / O heterocyclic aromatic hydrocarbons with MR effect can be induced to have HLCT properties by the charge perturbation of the outer indole-carbazole, achieving 100% exciton utilization.

[0014] (5) Tert-butyl groups are introduced at the ends of both the donor and acceptor units, which can increase the solubility of the material and facilitate solution processing and low-cost fabrication of high-efficiency organic light-emitting devices (OLEDs).

[0015] The preparation method of the thermal exciton luminescent material is as follows: 2,12-di-tert-butyl-5,9-dioxa-13b-borona[3,2,1-de]anthracene, 2,5-di-tert-butylindole[3,2,1-jk]carbazole, Pd(PPh3)4, and potassium carbonate are dissolved in a mixed solvent of toluene, ethanol, and water. The mixture is degassed under a nitrogen atmosphere for 15 min, magnetically stirred, and heated to 95 °C for 12 h. After cooling to room temperature, deionized water is added to quench the reaction. The reaction mixture is extracted with dichloromethane. The collected organic layer solution is washed with deionized water and dried with anhydrous sodium sulfate. The solvent is removed by rotary distillation. The crude product is purified by silica gel column chromatography to obtain the near-ultraviolet thermal exciton luminescent material.

[0016] Another objective of this invention is to provide an application of this organic near-ultraviolet luminescent material as a guest material for the luminescent layer in the fabrication of near-ultraviolet OLEDs, thereby improving the luminous color purity and luminous efficiency of the device.

[0017] The device structure of the near-ultraviolet OLEDs of the present invention is as follows: ITO / PEDOT:PSS (30nm) / Hosts (CBP, mCBP, mCP or CzSi):1-100wt%ICz-BO (20nm) / TmPyPB (50nm) / LiF (1nm) / Al (100nm).

[0018] Indium tin oxide (ITO) conductive glass is used as the anode material;

[0019] Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) is the hole injection layer material; 1,3,5-tris[(3-pyridyl)-3-phenyl]benzene (TmPyPB) is the electron transport layer material;

[0020] Lithium fluoride (LiF) is used as the electron injection layer material, and aluminum (Al) is used as the cathode material.

[0021] The doping concentration of near-ultraviolet luminescent material ICz-BO as the guest of the luminescent layer is 1-100 wt%.

[0022] The main material of the light-emitting layer of near-ultraviolet organic light-emitting devices is: 4,4'-bis(9H-carbazole-9-yl)-1,1'-biphenyl (CBP), 3,3'-bis(9H-carbazole-9-yl)-1,1'-biphenyl (mCBP), 1,3-bis(9H-carbazole-9-yl)phenyl (mCP) or 9-(4-(tert-butyl)phenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi).

[0023] In the provided application method, organic near-ultraviolet luminescent material ICz-BO is used as the guest material of the luminescent layer, and OLEDs are prepared by solution processing.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The organic near-ultraviolet light-emitting material of the present invention has a simple molecular structure and low preparation cost. The multi-site modification of indole-carbazole can enrich the library of organic near-ultraviolet light-emitting materials.

[0026] (2) The organic near-ultraviolet light-emitting material of the present invention has high thermal stability and dual characteristics of MR effect and HLCT excited state. The material has high luminous efficiency and high color purity, which creates conditions for high-definition display.

[0027] The research results show that solution-processed OLEDs prepared from this type of near-ultraviolet thermal exciton luminescent material exhibit advantages such as high efficiency, deep color depth, and narrow spectral band. The electroluminescence peak of the device is located at 414 nm, with a luminous efficiency as high as 12.01%, a half-width of only 37 nm, and a chromaticity y-axis of only 0.031, showing promising application prospects. Attached Figure Description

[0028] Figure 1 The above is the proton NMR spectrum of ICz-BO, a near-ultraviolet thermal exciton luminescent material in Example 1 of this invention.

[0029] Figure 2 Figure 1 shows the theoretical calculation diagram of the near-ultraviolet thermal exciton luminescent material ICz-BO in Example 1 of this invention. Figure 1a shows the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) diagrams. Figure 2b shows the root mean square difference between the first singlet excited state (S1) and the ground state (S0). Figure 2c shows the mechanism of excited state energy levels, exciton intersystem crossing, and reverse intersystem crossing. Figure 3d shows the spin-orbit coupling (SOC) diagram of reverse intersystem crossing in each excited state.

[0030] Figure 3 The diagram shows the single-crystal diffraction structure of the near-ultraviolet thermal exciton luminescent material ICz-BO in Embodiment 1 of the present invention, with top and front view views respectively.

[0031] Figure 4 The image shows the thermogravimetric (TG) loss of the near-ultraviolet thermal exciton luminescent material ICz-BO in Example 1 of this invention.

[0032] Figure 5 The inset shows the cyclic voltammogram of the near-ultraviolet thermal exciton luminescent material ICz-BO in Example 1 of this invention. The inset is a ferrocene reference.

[0033] Figure 6 The images show the UV-Vis absorption spectrum and photoluminescence spectrum of the near-ultraviolet thermal exciton luminescent material ICz-BO in toluene solution in Example 1 of this invention, as well as the photoluminescence spectrum of a 2wt% ICz-BO-doped CBP thin film.

[0034] Figure 7 The image shows the low-temperature fluorescence and phosphorescence spectrum of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP film in Example 1 of the present invention at a doping concentration of 2wt% and a temperature of 77K.

[0035] Figure 8 The near-ultraviolet thermal exciton luminescent material ICz-BO in Example 1 of this invention was tested in different polar solvents (10... -5 The UV-Vis absorption spectra of M) were obtained with solvents including n-hexane, toluene, dioxane, triethylamine, butyl ether, isopropyl ether, chloroform, diethyl ether, ethyl acetate, diethylene glycol dimethyl ether, tetrahydrofuran, dichloromethane, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, acetone, and acetonitrile.

[0036] Figure 9 The near-ultraviolet thermal exciton luminescent material ICz-BO in Example 1 of this invention was tested in different polar solvents (10... -5 The photoluminescence spectrum of M) was obtained, with solvents including n-hexane, toluene, dioxane, triethylamine, butyl ether, isopropyl ether, chloroform, diethyl ether, ethyl acetate, diethylene glycol dimethyl ether, tetrahydrofuran, dichloromethane, N-methylpyrrolidone, and dimethyl sulfoxide. Dimethylformamide, acetone, acetonitrile.

[0037] Figure 10 This is a graph showing the relationship between the Stokes shift and solvent polarity parameters of the near-ultraviolet thermal exciton luminescent material ICz-BO in Example 1 of the present invention.

[0038] Figure 11 This is a fluorescence lifetime curve of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP film in Example 1 of the present invention at a doping concentration of 2wt%.

[0039] Figure 12 This is the electroluminescence emission peak diagram of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP device in Embodiment 1 of the present invention.

[0040] Figure 13 This is a graph showing the relationship between the current efficiency, power efficiency, and external quantum efficiency of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP device in Embodiment 1 of the present invention and the brightness.

[0041] Figure 14 This is a graph showing the relationship between the current density and brightness of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP device in Embodiment 1 of the present invention as a function of driving voltage.

[0042] Figure 15This is the electroluminescence emission peak diagram of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP, mCBP, mCP, CzSi device in Example 1 of the present invention.

[0043] Figure 16 This is a graph showing the relationship between the current efficiency, power efficiency, and external quantum efficiency of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP, mCBP, mCP, and CzSi devices in Example 1 of the present invention and brightness.

[0044] Figure 17 This is a graph showing the relationship between current density and brightness of the near-ultraviolet thermal exciton luminescent material ICz-BO-doped CBP, mCBP, mCP, CzSi device as a function of driving voltage in Embodiment 1 of the present invention. Detailed Implementation

[0045] The organic near-ultraviolet light-emitting material provided by this invention is used as a guest material for the light-emitting layer in organic electroluminescent diode devices. The preferred device structure is ITO / PEDOT:PSS (30nm) / CBP:2.0wt%ICz-BO (20nm) / TmPyPB (50nm) / LiF (1nm) / Al (100nm).

[0046] The near-ultraviolet luminescent material ICz-BO is used as the guest material of the luminescent layer, and the doping concentration in the CBP film is preferably 2wt%, with chlorobenzene solvent used in the blending solution.

[0047] The thicknesses of the hole injection layer and the luminescent layer were measured using a probe-type surface profilometer (Dektak-XT). TmPyPB, LiF, and Al were deposited using a vacuum evaporation apparatus (ZD-400), and their thicknesses and deposition rates were measured using a thin film coating controller (SQC-310C). Except for ITO and PEDOT:PSS, the operation of the remaining functional layers was performed in a nitrogen-filled glove box. The electroluminescence spectra of the OLEDs were measured using a PR-735 spectroradiometer; current density-voltage and luminance-voltage curves were measured using a Keithley 2400 source measurement unit. The external quantum efficiency was calculated based on the electroluminescence spectra, current density, and luminance, assuming Lambert emission.

[0048] The specific fabrication process of the above-mentioned organic light-emitting diode device is as follows:

[0049] Step 1: Clean the ITO conductive glass (substrate) with ITO cleaning solution, deionized water, acetone and isopropanol in sequence for 20 minutes, and then dry it in a vacuum drying oven at 80℃.

[0050] Step 2: Perform a 15-minute ultraviolet ozone plasma surface treatment on the substrate treated in Step 1. This treatment method utilizes the strong oxidizing properties of ozone generated under microwaves to clean residual organic matter on the ITO surface. At the same time, it can increase the oxygen vacancies on the ITO surface and improve the work function of the ITO surface.

[0051] Step 3: Spin-coat PEDOT:PSS aqueous solution onto the substrate treated in Step 2 at a speed of 3000 rpm / min for 30 s, and anneal at 150℃ for 15 min to a thickness of 30 nm.

[0052] Step 4: Spin-coat the luminescent layer solution onto the substrate treated in Step 3, wherein CBP is the host material and ICz-BO is the guest material, with a blending ratio of 98:2, and chlorobenzene is used as the solvent at a concentration of 10 mg / mL. Stir at 60°C for 1 h. Spin-coat the luminescent layer solution at 3000 rpm / min for 30 s, anneal at 60°C for 15 min, and achieve a thickness of 20 nm.

[0053] Step 5: Place the substrate treated in Step 4 onto the mask template and evacuate the vacuum chamber to 3×10⁻⁶. -4 Pa, evaporation of electron transport layer TmPyPB, rate is The thickness is 50nm.

[0054] Step 6: Deposit an electron-implanted LiF layer onto the substrate treated in step 5 at a rate of [missing information]. The thickness is 1 nm.

[0055] Step 7: Open the vacuum chamber and replace it with a precision mask template with electrode patterns. Similarly, evacuate the vacuum chamber to 3×10⁻⁶. -4 Pa, cathode Al vapor deposition rate is With a thickness of 100 nm, the resulting device has a light-emitting area of ​​0.04 cm². 2 .

[0056] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific details described below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0057] In this invention, the preparation methods are all conventional unless otherwise specified. The raw materials used are all available from publicly available commercial sources unless otherwise specified.

[0058] Example 1: Preparation of near-ultraviolet thermal exciton luminescent material ICz-BO

[0059] The specific synthesis route of the near-ultraviolet thermal exciton luminescent material ICz-BO of this invention is as follows:

[0060]

[0061] Compound 1 (200 mg, 0.39 mmol), compound 2 (167 mg, 0.39 mmol), Pd(PPh3)4 (68 mg, 0.06 mmol), and potassium carbonate (430 mg, 3.93 mmol) were dissolved in a mixed solvent of toluene, ethanol, and water (8:1:1). The mixture was degassed under a nitrogen atmosphere for 15 min, magnetically stirred, and heated to 95 °C for 12 h. After cooling to room temperature, the reaction was quenched with deionized water. The reaction mixture was extracted with dichloromethane, and the collected organic layer was washed with deionized water and dried over anhydrous sodium sulfate. The solvent was removed by rotary distillation. The crude product was purified by silica gel column chromatography (eluent: n-hexane / dichloromethane = 5 / 1, v / v) to obtain a white solid near-ultraviolet thermal exciton luminescent material ICz-BO (173 mg), yield: 68.0%. 1 ¹H NMR (400MHz, Chloroform-d): δ / ppm = 8.77 (s, 2H), 8.20 (d, J = 6.6Hz, 3H), 7.94 (s, 2H), 7.82 (dd, J = 17.1, 8.6Hz, 3H), 7.61 (s, 3H), 7.53 (d, J = 8.7Hz, 2H), 1.60 (s, 10H). NMR spectra are shown below. Figure 1 As shown.

[0062] Example 2: Theoretical Calculations of Near-Ultraviolet Thermal Exciton Luminescent Material ICz-BO

[0063] Density functional theory (DFT) calculations were performed on the near-ultraviolet thermal exciton luminescent material ICz-BO at the B3LYP / 6-31G(d,p) level using the Gaussian 09 program to explore its geometry and electron distribution. Figure 2 As can be seen from this, the highest occupied molecular orbital (HOMO) is mainly distributed on the indole-carbazole unit, and the lowest unoccupied molecular orbital (LUMO) is mainly distributed on rigid B / O heterocyclic aromatic hydrocarbons, both extending slightly to the weakly conjugated benzene ring, proving that ICz-BO is a typical donor-acceptor structure. Figure 2 As can be seen from b, the root mean square error (RMSD) between the ICz-BO excited state and the ground state is: This indicates that the contribution of non-radiative transitions such as vibrational relaxation is very small. Figure 2 c and Figure 2 As can be seen from d, ICz-BO has multiple RISC channels and forms a reverse intersystem crossing (hRISC) channel from high-level triplet state to degenerate singlet state (T6→S1 / S2). Spin-orbit coupling (SOC) calculations show that the hRISC channel plays a dominant role.

[0064] Example 3: Single-crystal analysis of near-ultraviolet thermal exciton luminescent material ICz-BO

[0065] The near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 was dissolved in dichloromethane, and methanol was added. A slow diffusion method was used to obtain single crystals of ICz-BO, and their precise geometry was then determined using a single-crystal X-ray diffractometer (XRD). Figure 3 It is known that indolocarbazole and rigid B / O heterocyclic aromatic hydrocarbons have a small angular misalignment, which can effectively prevent the close packing of molecules.

[0066] Example 4: Thermogravimetric analysis of near-ultraviolet thermal exciton luminescent material ICz-BO

[0067] The near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 was heated at a rate of 20°C / min within the range of 30–600°C under N2 protection, and its thermogravimetric curve was measured. Figure 4 It can be seen that the temperature at which ICz-BO loses 5 wt% of thermal decomposition is 472℃, indicating that the material has high thermal stability.

[0068] Example 5: Electrochemical Performance Analysis of Near-Ultraviolet Thermal Exciton Luminescent Material ICz-BO

[0069] The near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 was dissolved in dichloromethane. Cyclic voltammetry (CV) was performed using a CHI 620 voltammeter with a platinum wire as the working electrode, Ag / AgCl as the reference electrode, and a 0.1 M tetrabutylammonium hexafluorophosphonate (nBu4NPF6) acetonitrile solution as the electrolyte. Ferrocene / ferrocene cations (Fc / Fc) were also used. + Using the redox couple as a reference, the cyclic voltammetry performance was tested at a scan rate of 50 mV / s. Figure 5 It can be seen that the measured ferrocene / ferrocene cation (Fc / Fc) + The oxidation potential of ICz-BO is 0.37 eV, and the oxidation potential of ICz-BO is 1.31 eV. The calculated HOMO level of ICz-BO is -5.74 eV, and the LUMO level can be calculated from the optical band gap and the HOMO level, which is -2.64 eV.

[0070] Example 6: UV-Vis absorption and photoluminescence spectra of the near-ultraviolet thermal exciton luminescent material ICz-BO

[0071] The near-ultraviolet thermoluminescent material ICz-BO from Example 1 was dissolved in a toluene solution (10). -5 M), the UV-Vis absorption spectrum and photoluminescence spectrum of an ICz-BO toluene solution at room temperature, and the photoluminescence spectrum of an ICz-BO-doped CBP film at a doping concentration of 2 wt% were measured. Figure 6 It can be seen that the toluene solution of ICz-BO shows a strong and sharp absorption peak at 382 nm, which is attributed to the short-range charge transfer transition absorption of the entire rigid molecular structure. The emission spectrum is at 404 nm, accompanied by an extremely small Stokes shift of 22 nm. The emission spectrum of its doped CBP film is red-shifted to 413 nm.

[0072] Example 7: Low-temperature fluorescence and phosphorescence spectra of the near-ultraviolet thermal exciton luminescent material ICz-BO

[0073] The near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 was doped into a CBP film to prepare a 2wt% ICz-BO doped CBP film. The low-temperature fluorescence and phosphorescence spectrum of this doped film was measured at 77 K. Figure 7 It can be seen that the initial peak positions of the fluorescence and phosphorescence spectra are obtained by using the tangent, and the ΔE of ICz-BO can be calculated. ST It is 0.48 eV.

[0074] Example 8: Solvation absorption spectrum of near-ultraviolet thermal exciton luminescent material ICz-BO

[0075] The near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 was dissolved in different solvents to prepare ICz-BO solutions in different solvents (10). -5 M), and their UV-Vis absorption properties were tested. These solvents were n-hexane, toluene, dioxane, triethylamine, butyl ether, isopropyl ether, chloroform, diethyl ether, ethyl acetate, diethylene glycol dimethyl ether, tetrahydrofuran, dichloromethane, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, acetone, and acetonitrile. Figure 8 It can be seen that the UV-Vis absorption spectrum of ICz-BO did not change significantly with the increase of solvent polarity.

[0076] Example 9: Solvation emission spectrum of near-ultraviolet thermal exciton luminescent material ICz-BO

[0077] The near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 was dissolved in different solvents to obtain ICz-BO solutions in different solvents (10 -5 M), and their photoluminescence spectra were measured. These solvents were n-hexane, toluene, dioxane, triethylamine, butyl ether, isopropyl ether, chloroform, diethyl ether, ethyl acetate, diethylene glycol dimethyl ether, tetrahydrofuran, dichloromethane, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, acetone, and acetonitrile. Figure 9It can be seen that ICz-BO has a significant solvation effect. As the solvent polarity increases, it exhibits solvation color change. When the solvent polarity is small, the emission wavelength hardly redshifts, while when the solvent polarity is large, the emission wavelength redshifts significantly and becomes wider, indicating the presence of CT effect.

[0078] Example 10: Solvated Stokes shift of near-ultraviolet thermal exciton luminescent material ICz-BO

[0079] The solvation test results of the near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 in Examples 7 and 8 were used, combined with the Lippert-Mataga solvation color change model, to plot the relationship between Stokes shift and solvent polarity parameters. Figure 10 It can be seen that when the solvent polarity is low, the Stokes shift of ICz-BO is very small, while when the solvent polarity increases, the Stokes shift of ICz-BO also increases, thus exhibiting different Stokes shifts in low-polarity and high-polarity solvents.

[0080] Example 11 Fluorescence lifetime of near-ultraviolet thermal exciton luminescent material ICz-BO

[0081] The near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 was doped into a CBP film at a doping concentration of 2 wt% to prepare an ICz-BO-doped CBP film. Its fluorescence lifetime was tested under ambient temperature and atmospheric conditions. Figure 11 It can be seen that the fluorescence lifetime has a delayed component. The fitting results show that the transient lifetime of ICz-BO is 3.3 ns and the delayed lifetime is 10.1 ns. No exciton lifetimes of microseconds or longer were detected.

[0082] Example 12: Performance of electroluminescent devices based on the near-ultraviolet thermal exciton luminescent material ICz-BO

[0083] Using the near-ultraviolet thermal exciton luminescent material ICz-BO from Example 1 as the guest material of the luminescent layer and CBP as the host material, luminescent devices with different concentrations of ICz-BO-doped CBP were prepared. The device structure was ITO / PEDOT:PSS (30nm) / CBP:x wt% ICz-BO (x=1,2,3,5,10,100)(20nm) / TmPyPB (50nm) / LiF (1nm) / Al (100nm). (See Table 1 and...) Figure 12-14 It can be seen that the maximum external quantum efficiency of the light-emitting device at a doping concentration of 2wt% reaches 12.01%, the maximum emission peak is located at 414nm, and the full width at half maximum (FWHM) is 37nm. (CIE) y =0.031.

[0084] Table 1 Electroluminescence performance parameters of ICz-BO devices with different doping concentrations in Example 1 of the present invention.

[0085]

[0086] a) Doping concentration; b) Turn-on voltage; c) Electroluminescence peak; d) Full width at half maximum (FWHM) of the electroluminescence spectrum; e) Maximum current efficiency; f) Maximum power efficiency; g) Maximum external quantum efficiency; c) International Commission on Illumination (ICI) y-axis coordinates of the electroluminescence spectrum.

[0087] Furthermore, light-emitting devices were fabricated by doping ICz-BO with different host materials at a concentration of 2wt%. The preferred device structure was ITO / PEDOT:PSS (30nm) / Hosts:2wt% ICz-BO (20nm) / TmPyPB (50nm) / LiF (1nm) / Al (100nm). (See Table 2 and...) Figure 15-17 It can be seen that the preferred light-emitting device can form narrow-band near-ultraviolet light emission under different host materials, with good electroluminescence performance parameters and wide applicability.

[0088] Table 2 Electroluminescence performance parameters of ICz-BO doped host devices in Example 1 of the present invention

[0089]

[0090] a) Doping concentration; b) Turn-on voltage; c) Electroluminescence peak; d) Full width at half maximum (FWHM) of the electroluminescence spectrum; e) Maximum current efficiency; f) Maximum power efficiency; g) Maximum external quantum efficiency; c) International Commission on Illumination (ICI) y-axis coordinates of the electroluminescence spectrum.

[0091] Although the invention has been described in conjunction with preferred embodiments, the invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the invention. Guided by the inventive concept, those skilled in the art should recognize that any modifications made to the various embodiments of the invention will be covered by the spirit and scope of the claims.

Claims

1. A near-ultraviolet thermoluminescent material based on multiple resonant electron donor and acceptor units, characterized in that, The thermal exciton luminescent material is 2,12-di-tert-butyl-5,9-dioxa-13b-boronaphthalo[3,2,1- de Anthracene is an electron acceptor unit, 2,5-di-tert-butylindolo[3,2,1- jk Carbazole as an electron donor unit; The chemical structure of the thermal exciton luminescent material is shown in formula (1): ， Equation (1).

2. The near-ultraviolet photothermal exciton luminescent material based on multiple resonant electron donor and acceptor units according to claim 1, characterized in that, The thermal exciton luminescent material is prepared by: 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxoboropentenyl-2-yl)-5,9-dioxa-13b-boronaphthalo[3,2,1- de Anthracene 11-Bromo-2,5-di-tert-butylindole [3,2,1- jk ] carbazole Pd(PPh3)4 and potassium carbonate were dissolved in a solvent, degassed under a nitrogen atmosphere for 15 min, magnetically stirred, and heated to 95℃ for 12 h. After cooling to room temperature, the reaction was quenched, and the material was purified by extraction, washing, drying, and rotary distillation to remove the solvent, thus obtaining a near-ultraviolet thermal exciton luminescent material.

3. The application of the near-ultraviolet photothermal exciton luminescent material based on multiple resonant electron donor and acceptor units according to claim 1, characterized in that, The thermal exciton luminescent material is used as the guest material of the luminescent layer to prepare near-ultraviolet organic light-emitting devices.

4. The application of the near-ultraviolet photothermal exciton luminescent material based on multiple resonant electron donor and acceptor units according to claim 3, characterized in that, The doping concentration of the thermal exciton luminescent material, which serves as the guest material of the luminescent layer, is 1-100 wt%.

5. The application of the near-ultraviolet photothermal exciton luminescent material based on multiple resonant electron donor and acceptor units according to claim 3, characterized in that, The main material of the light-emitting layer of the near-ultraviolet organic light-emitting device is CBP, mCBP, mCP or CzSi.

6. The application of the near-ultraviolet photothermal exciton luminescent material based on multiple resonant electron donor and acceptor units according to claim 3, characterized in that, The near-ultraviolet organic light-emitting device is prepared by solution processing.

7. The application of the near-ultraviolet photothermal exciton luminescent material based on multiple resonant electron donor and acceptor units according to claim 3, characterized in that, The structure of the near-ultraviolet organic light-emitting device is ITO / PEDOT:PSS 30 nm / HostsCBP, mCBP, mCP or CzSi:ICz-BO 20 nm / TmPyPB 50 nm / LiF 1 nm / Al 100 nm.

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