Tri-pyrazole boron Eu (II) complex and application thereof as electroluminescent material

Abstract

The invention relates to a tri-pyrazolo boron Eu (II) complex, which has the following structure as shown in the specification, the complex shows high photoluminescence quantum yield and excellent air stability and thermal stability, and is suitable for a luminescent layer in an electroluminescent device. The Eu (II) complex Eu (Tp3Me, 5Me) 2 is used as a guest material to be doped in a host material such as SiCzCz, an efficient and stable OLED can be prepared, the maximum external quantum efficiency reaches 16.9%, LT90 reaches 1835 seconds under the initial brightness of 1000 cd / m, and compared with an OLED prepared from the Eu (II) complex Eu (Tp3Me, 5Me) 2 without large steric hindrance, the efficiency and stability are greatly improved, which shows that the performance of the Eu (II) complex OLED can be improved by introducing the large steric hindrance group.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent devices. In particular, this invention relates to a tripyrazole boron Eu(II) complex and its application as an electroluminescent material. Background Technology

[0002] Rare earth complexes are an important class of luminescent materials. Their luminescence mechanisms mainly include three types: ligand-mediated luminescence, 4f-4f transition luminescence of the central ion, and 5d-4f transition luminescence of the central ion. Among these, the luminescence of Ce(III), Eu(II), Yb(II), and Sm(II) complexes primarily originates from electric dipole-allowed 5d-4f transitions. Due to the parity-allowed nature of the 5d-4f transition, these complexes possess short excited-state lifetimes (on the order of nanoseconds). Furthermore, since the 5d orbital is easily influenced by the ligand field, the emission wavelength and luminescence efficiency of the complexes can be adjusted and optimized by modifying the coordination environment around the central ion. Based on the advantages of high luminescence efficiency, short excited-state lifetime, and tunable emission color, rare earth luminescent complexes with df transitions are considered a new generation of highly efficient and stable electroluminescent materials.

[0003] Among the four ions mentioned above, Eu(II) has a ground-state valence electron configuration of 4f. 7 5d 0 The 5d orbital is unoccupied. Eu(II) reaches an excited state via an fd transition, and its valence electron configuration changes to 4f. 6 5d 1 .because 5 The interaction between the d and 4f orbitals causes the excited state of Eu(II) to split into seven energy levels. 7 F n (n = 0–6), therefore, the excitation spectra of Eu(II) complexes have multiple broad peaks. The ground state of Eu(II) has only one energy level, so the emission peaks are mostly singlets. The energy difference between the 5d and 4f energy levels is easily affected by molecular vibrations and ligand fields, making the position of the maximum emission wavelength of Eu(II) complexes easily tunable. Furthermore, Eu(II) complexes have been shown to exhibit 100% exciton utilization in organic light-emitting diodes (OLEDs) and possess short excited-state lifetimes on the order of hundreds of nanoseconds, making them highly promising for applications in efficient and stable OLEDs. However, reports on Eu(II) complexes in OLEDs are currently scarce, and research on their device stability is still lacking. Therefore, developing efficient and stable OLEDs based on Eu(II) complexes, especially in terms of material selection and device parameter optimization, and exploring the special requirements of this type of luminescent material on device structure, is of great significance for guiding further optimization of OLEDs and promoting the further development of OLED technology. Summary of the Invention

[0004] An embodiment of the present invention provides a tripyrazole boron Eu(II) complex having the structure shown in the following structural formula: Among them, R, R 1 R 2 It is independently selected from any one of hydrogen, unsubstituted alkyl, alkoxy, unsubstituted alkenyl, halogen-substituted alkenyl, unsubstituted alkynyl, unsubstituted phenyl, substituted phenyl, unsubstituted aryl, substituted aryl, and heterocycles containing O, N, or S coordination sites; Preferably, R, R 1 R 2 It is independently selected from any one of hydrogen, unsubstituted C1-C18 alkyl, unsubstituted C1-C18 alkoxy, halogen atom, C2-C18 unsubstituted alkenyl, C2-C18 halogen-substituted alkenyl, C2-C18 unsubstituted alkynyl, phenyl, substituted phenyl, C6-C18 unsubstituted aryl, and heterocycles containing O, N, or S coordination sites; Preferably, R, R 1 R 2 It is independently selected from any one of hydrogen, methyl, ethyl, tert-butyl, phenyl, and 1-adamantyl; In a further preferred embodiment, R is hydrogen; Further preferred, R 1 Independently selected from methyl and ethyl; Further preferred, R 2 It is independently selected from tert-butyl and 1-adamantyl.

[0005] According to one embodiment of the present invention, for example, the tripyrazole boron Eu(II) complex is the following compound Eu(Tp) 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 and Eu(Tp 3Me,4Ph,5Me At least one of the following: Preferably, the tripyrazole boron Eu(II) complex is Eu(Tp) 3Et,4tBu,5Et )2.

[0006] An embodiment of the present invention provides an electroluminescent device, the light-emitting device comprising a cathode, an anode, and a light-emitting layer located between the cathode and the anode, wherein the light-emitting layer comprises the tripyrazole boron Eu(II) complex as described above.

[0007] According to one embodiment of the present invention, for example, the light-emitting layer is a mixture of a guest material and a host material, wherein the guest material includes the tripyrazole boron Eu(II) complex as described above, and the host material is selected from host materials with good thermal stability; Preferably, the main material is selected from any one of mCBP, SiCzCz, oCBP, and mCP; Preferably, the doping concentration is 1 wt%-20 wt%, more preferably 5 wt%-12 wt%, more preferably 7 wt%-10 wt%, and most preferably 10 wt%, wherein the doping concentration is the percentage of the mass of the guest material to the total mass of the guest material and the host material.

[0008] According to one embodiment of the present invention, for example, the electroluminescent device further includes an electron transport layer located between the cathode and the light-emitting layer; Preferably, the electron transport layer is an electron transport material with good thermal stability; Preferably, the electron transport layer comprises mSiTrz, DPPyA, and / or Liq; More preferably, the electron transport layer comprises mSiTrz and / or DPPyc.

[0009] According to one embodiment of the present invention, for example, the electroluminescent device further includes a hole transport layer located between the anode and the light-emitting layer; Preferably, the hole transport layer is a hole transport material with good thermal stability; Preferably, the hole transport layer includes mCBP, Com1, and / or SiCzCz.

[0010] More preferably, the hole transport layer comprises SiCzCz and / or Com 1.

[0011] According to one embodiment of the present invention, for example, the electroluminescent device further includes an electron transport layer located between the cathode and the light-emitting layer and a hole transport layer located between the anode and the light-emitting layer; Preferably, the hole transport layer comprises SiCzCz and / or Com 1, and the electron transport layer comprises mSiTrz and / or DPPyA; Preferably, the electroluminescent device further includes an electron injection layer located between the cathode and the electron transport layer, and the electroluminescent device further includes a hole injection layer located between the anode and the hole transport layer; More preferably, the electron injection layer comprises Liq, and the hole injection layer comprises HATCN.

[0012] According to one embodiment of the present invention, for example, the thickness of the light-emitting layer is 1-50 nm, preferably 10-40 nm, preferably 15-30 nm, preferably 20-25 nm, and most preferably 24 nm.

[0013] According to one embodiment of the present invention, for example, the structure of the electroluminescent device is: ITO / HATCN (10nm) / Com 1 (50 nm) / SiCzCz: Eu(Tp 3Et,4tBu,5Et )2(10 wt%, 20 nm) / mSiTrz (5 nm) / mSiTrz:Liq(20 nm) / LiF(1 nm) / Al(100 nm). Attached Figure Description

[0014] Figure 1 It is the Eu(II) complex Eu(Tp) characterized in the embodiments of the present invention. 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 and Eu(Tp 3Me,4Ph,5Me )2 Emission spectrum in solid powder state (excitation wavelength 280 nm).

[0015] Figure 2 It is the Eu(II) complex Eu(Tp) characterized in the embodiments of the present invention. 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 and Eu(Tp 3Me,4Ph,5Me )2 Photoluminescence quantum yield decay curve in air.

[0016] Figure 3 It is the Eu(II) complex Eu(Tp) characterized in the embodiments of the present invention. 3Et,4tBu,5Et )2 Thermogravimetric curves under nitrogen atmosphere.

[0017] Figure 4 It is the Eu(II) complex Eu(Tp) characterized in the embodiments of the present invention. 3Me,4Ad,5Me )2 Thermogravimetric curves under nitrogen atmosphere.

[0018] Figure 5 This is a current density-voltage-brightness curve of device D1 in an embodiment of the present invention.

[0019] Figure 6 This is a power efficiency-brightness-EQE curve of device D1 in an embodiment of the present invention.

[0020] Figure 7 In this embodiment of the invention, devices D1 and D5 have an initial brightness of 1000 cd / m. -2 Brightness decay curve during continuous operation. Detailed Implementation

[0021] The electroluminescent device using Eu(II) complex as the luminescent material of the present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0022] The full name of the compound corresponding to the abbreviation: Com 1: N-([1,1'-biphenyl]-2-yl)-2',7'-di-tert-butyl-N-(9,9-dimethyl-9H-fluorene-2-yl)-9,9'-spirodifluorene-2-amine mCBP: 3,3'-Di(9-carbazolyl)biphenyl oCBP: 2,2'-Di(9H-carbazole-9-yl)biphenyl SiCzCz:9-(3-(triphenylsilyl)phenyl)-9H-3,9'-biscarbazole mCP: 9,9'-(1,3-phenyl)bis-9-hydro-carbazole mSiTrz: 2-Phenylacetyl-4,6-bis(triphenylsilyl)phenyl)-1,3,5-triazine DPPyA: 9-Phenyl-10-(3-pyridyl)anthracene Liq: Lithium 8-hydroxyquinoline Given the broad application prospects of Eu(II) complex OLEDs, and the scarcity of current reports on Eu(II) complex-based OLEDs without any discussion of device stability, the inventors of this invention characterized three Eu(II) complexes, Eu(Tp). 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 and Eu(Tp 3Me,4Ph,5Me The photoluminescence properties and stability of 2, and the luminescence of all three complexes originating from the central Eu. 2+ The df transition of the ion resulted in high photoluminescent quantum yields (PLQY) in all three complexes, with Eu(Tp) exhibiting particularly high yields. 3Et,4tBu,5Et )2 also exhibits excellent air and thermal stability, indicating its superior application potential in OLEDs. Simultaneously, the inventors of this invention have also prepared a material based on Eu(Tp) 3Et,4tBu,5Et Through device structure optimization, the optimal OLED device was found to have a maximum external quantum efficiency (EQE) of 16.9% and a maximum brightness of 33770 cd / m². -2 The device is at 1000 cd m -2 The time it takes for the light to decay to 90% of its initial brightness (LT) 90The stability of the device was 1835 s, which is 4.5 times higher than that of the device without Eu(II) complex without large steric hindrance substituents. This fills the gap in the stability research of Eu(II) complex electroluminescent devices and shows the huge application potential of this type of electroluminescent device.

[0023] Example 1: Synthesis and Characterization of Coordination Compounds In embodiments of the present invention, eight ligands containing sterically hindered groups were designed and synthesized, and corresponding Eu(II) complexes were synthesized. The synthesis of the complexes was carried out in a glove box with an oxygen content of less than 0.1 ppm. The synthesis methods of the complexes are as follows: Synthesis of 4-tert-butyl-3,5-heptanedione: 3,5-heptanedione (50.0 g, 390 mmol) was added to dichloromethane (100 mL), and concentrated sulfuric acid (76.0 g, 780 mmol) was slowly added dropwise under ice bath conditions, followed by the addition of tert-butanol (43.4 g, 585 mmol). The reaction mixture was allowed to react at room temperature for 24 hours. The reaction mixture was then poured into water, and the product was extracted from the aqueous phase with dichloromethane. The combined organic phases were dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The product was then distilled under reduced pressure at 80 °C to obtain the low-boiling fraction, followed by distillation at 100 °C to obtain the product as a colorless liquid (18.8 g, 102 mmol, 26%). 1 HNMR (400 MHz, CDCl3) δ (ppm): 3.66 (s,1H), 2.48 (m, 4H), 1.06(s, 9H), 1.03(t, 6H). 3,5-Diethyl-4-tert-butylpyrazole (HPz) 3Et,4tBu,5Et Synthesis of 4-tert-butyl-3,5-heptadecane: 18.8 g (102 mmol) of 4-tert-butyl-3,5-heptadecane was diluted with ethanol, and hydrazine hydrate (13.0 g, 221 mmol, 85 wt%) was added dropwise under ice bath. After the addition was complete, the mixture was stirred and refluxed overnight. The solvent was removed by rotary evaporation, and the low-boiling components were removed by vacuum distillation. The solid solid solidified upon cooling. The obtained solid was sublimated (~10 Pa) under a temperature gradient of 120 °C–50 °C–room temperature to give product HPz. 3Et,4tBu,5Et (15.2 g, 84.4mmol, 82.7%). 1 HNMR (400 MHz, (CD3)2SO) δ (ppm): 11.81 (s, 1H), 2.64 (q, 4H), 1.28 (s, 9H), 1.15 (t, 6H). Potassium tris(3,5-diethyl-4-tert-butyl-1-pyrazolyl)borohydride (KTp) 3Et,4tBu,5EtSynthesis of KBH4 (0.313 g, 5.80 mmol) and HPz: 3Et,4tBu,5Et (4.105 g, 22.77 mmol) were mixed and stirred, then gradually heated to 245 °C and reacted for 3 hours, collecting 360 mL of hydrogen gas. After the reaction was complete, most of the pyrazole was removed by sublimation (~10 Pa) at a temperature gradient of 160 °C-90 °C-room temperature to obtain a white solid (2.521 g), consisting of the product and some HPz. 3Et,4tBu,5Et The purity is approximately 70%. 1 HNMR (400 MHz, (CD3)2SO) δ (ppm): 2.71 (q, 2H), 2.55 (q, 2H), 1.27(s, 9H), 1.05(t, 3H), 0.64(t, 3H). ESI-MS (m / z): [MK] − Calculated value [C] 33 H 58 BN6] − 549.68; Measured value: 549.48. Eu(Tp 3Et,4tBu,5Et Synthesis of )2: in KTp 3Et,4tBu,5Et A solution of EuI2 (0.605 g, 1.486 mmol) in tetrahydrofuran was added dropwise to a tetrahydrofuran solution of (2.521 g, 3.000 mmol, 70 wt%). A yellow solid precipitated with stirring. The mixture was stirred overnight, filtered, and the yellow solid was sublimated (~10 °C) at a temperature gradient of 300 °C - 240 °C - room temperature. −4 A yellow solid powder (0.310 g, 0.248 mmol, 17%) was obtained by (Pa). Elemental analysis calculated C 66 H 116 B2EuN 12 : C, 63.35%, H, 9.34%, N, 13.43%; Measured values: C, 63.42%, H, 9.51%, N, 13.67%. 3,5-Dimethyl-4-adamantylpyrazole (HPz) 3Me,4Ad,5Me Synthesis of 3,5-dimethylpyrazole (7.86 g, 81.8 mmol) and 1-bromoadamantane (17.5 g, 81.5 mmol) were mixed in a high-pressure reactor and reacted at 180 °C for 12 h. After cooling, the mixture was washed with dichloromethane and filtered to obtain a white solid. The pH was adjusted to approximately 7 with NaOH solution, and the mixture was extracted with dichloromethane. The organic phases were combined and evaporated to dryness. The resulting white solid was sublimated (~10 Pa) under a temperature gradient of 175 °C–115 °C–room temperature to give product HPz. 3Me,4Ad,5Me(9.90 g, 43.0 mmol, 52.7%). 1 HNMR (400 MHz, (CD3)2SO) δ (ppm):11.75(s, 1H), 2.23(s, 6H), 1.98(m, 3H), 1.94(d, 6H), 1.71(m, 6H). Eu(Tp 3Me,4Ad,5Me Synthesis of 2: NaBH4 (0.190 g, 5.02 mmol) and HP2 were synthesized. 3Me,4Ad,5Me (6.391 g, 27.7 mmol) were mixed and stirred, then gradually heated to 340 °C and reacted for 4 hours. After the reaction was completed, most of the pyrazole was removed by sublimation (~10 Pa) at a temperature gradient of 175 °C-115 °C-room temperature to obtain a brown powder (3.930 g), which is sodium tris(3,5-dimethyl-4-adamantyl-1-pyrazolyl)borohydride (NaTp). 3Me,4Ad,5Me The crude product consists of the product and a portion of HPz. 3Me ,4Ad,5Me The purity is approximately 70%. (NaTp) 3Me,4Ad,5Me A tetrahydrofuran solution (995 mg, 0.964 mmol, 70 wt%) containing 187 mg, 0.461 mmol of EuI2 was added dropwise. An orange-yellow solid precipitated with stirring. After stirring overnight, the mixture was filtered to obtain an orange-yellow solid (540 mg, 0.348 mmol, 75.5%). Elemental analysis calculated C. 90 H 128 B2EuN 12 • 1,4THF: C, 69.48%, H, 8.49%, N, 10.17%; Measured values: C, 68.86%, H, 8.78%, N, 9.56%. 4-Bromo-3,5-dimethyl-1-triphenylmethyl-1H-pyrazole (TrtPz) 3Me,4Br,5Me Synthesis of 4-bromo-3,5-dimethylpyrazole (26.6 g, 152 mmol) in tetrahydrofuran was added to a 500 mL round-bottom flask followed by 50 mL of tetrahydrofuran. While stirring in an ice bath, a tetrahydrofuran solution of 4-bromo-3,5-dimethylpyrazole (26.6 g, 152 mmol) was added. After reacting for 10 minutes, a tetrahydrofuran solution of triphenylchloromethane (46.6 g, 167 mmol) was added, resulting in a white turbid precipitate. The reaction proceeded for 12 h. The reaction solution was evaporated to dryness, dissolved in dichloromethane, filtered, and the filtrate was evaporated to dryness. After washing with methanol, the solution was filtered again and dried to obtain a white solid (49.9 g, 120 mmol, 79.0%). 1HNMR (400 MHz, CDCl3) δ (ppm): 7.27(m, 9H), 7.10(m, 6H), 2.19(s,3H), 1.50(s, 3H). 3,5-Dimethyl-4-phenyl-1-triphenylmethyl-1H-pyrazole (TrtPz) 3Me,4Ph,5Me Synthesis of ) : TrtPz 3Me ,4Br,5Me 15.9 g (31.0 mmol), phenylboronic acid (5.20 g, 42.6 mmol), potassium carbonate (15.2 g, 110 mmol), X-Phos (182 mg, 0.382 mmol), and X-Phos Pd G3 (323 mg, 0.382 mmol) were added to a mixture of 200 mL tetrahydrofuran and 60 mL water. After reflux for 24 h, the solution turned black. The organic phase was evaporated to dryness and washed with methanol to give a grayish-white solid (11.9 g, 28.7 mmol, 92.7%). 1 HNMR (400 MHz, CDCl3) δ (ppm): 7.35(t, 2H), 7.27(m, 9H), 7.23(d, 3H), 7.18 (m, 6H), 2.22(s, 3H), 1.49(s, 3H). 3,5-Dimethyl-4-phenylpyrazole (HPz) 3Me,4Ph,5Me Synthesis of ) : TrtPz 3Me,4Ph,5Me (10.4 g, 25.1 mmol) was dissolved in dichloromethane, passed through a simple silica gel column, and a small amount of methanol was added. 20 mL of trifluoroacetic acid was added dropwise, and the mixture was heated to reflux for 2 h. After cooling, sodium hydroxide solution was added to neutralize the solution. The mixture was separated by extraction with dichloromethane, and the combined organic phases were separated by column chromatography using ethyl acetate:petroleum ether = 1:10 as the developing solvent. The resulting white solid sublimed (~10 Pa) at a temperature gradient of 160 °C–90 °C–room temperature to give the product HPz. 3Me,4Ph,5Me (4.69 g, 27.2 mmol, 94.8%). 1 HNMR (400 MHz, (CD3)2SO) δ (ppm): 12.30(s, 1H), 7.40 (m, 2H), 7.28(s, 3H), 2.19(s, 6H). Eu(Tp 3Me,4Ph,5Me Synthesis of 2: NaBH4 (0.265 g, 7.01 mmol) and HP2 were synthesized. 3Me,4Ph,5Me(5.686 g, 33.0 mmol) were mixed and stirred, then gradually heated to 185 °C for 5 h. After the reaction was complete, most of the pyrazole was removed by sublimation (~10 Pa) at a temperature gradient of 160 °C-90 °C-room temperature to obtain a white solid (3.482 g), which was sodium tris(3,5-dimethyl-4-phenyl-1-pyrazolyl)borohydride (NaTp). 3Me,4Ph,5Me The crude product consists of the product and a portion of HPz. 3Me,4Ph,5Me The purity is approximately 75%. ESI-MS (m / z): [MK] − Calculated value [C] 33 H 34 BN6] − 525.29; Measured value 525.30. In NaTp 3Me ,4Ph,5Me A tetrahydrofuran solution containing 0.896 g (2.203 mmol) of EuI2 was added dropwise to a tetrahydrofuran solution containing 3.482 g (4.625 mmol, 75 wt%). A red solid precipitated with stirring. After stirring overnight, the mixture was filtered to obtain a red solid (2.28 g, 1.894 mmol, 86.0%). Elemental analysis calculated C. 66 H 68 B2EuN 12 • 3THF: C, 66.01%, H, 6.53%, N, 11.84%; Measured values: C, 66.16%, H, 6.690%, N, 11.72%. 3,5-Dimethyl-4-(4-carbazolylphenyl)pyrazole (HPz) 3Me,4CzPh,5Me Synthesis of 1-(carbazol-9-yl)pentane-2,4-dione (35.00 mmol) and 50 mL of ethanol were placed in a 100 mL round-bottom flask, and 2.4 mL of hydrazine hydrate (42 mmol) was added dropwise with stirring. The system was repeatedly evacuated and purged with nitrogen three times, heated to reflux, and stirred for 12 h. For post-treatment, the system was placed at -10 °C to cool and crystallize. Filtration yielded 5.168 g of white needle-like crystals, with a yield of 56.5%. 1 H NMR (400MHz, DMSO- d 6) δ 12.31 (s, 1H), 8.13 (d, J = 7.7 Hz, 2H), 7.68 (d, J = 8.2 Hz, 2H), 7.44 (t, J = 7.1 Hz, 2H), 7.19 (t, J= 7.0 Hz, 2H), 5.71 (s, 1H), 5.48 (s, 2H), 2.07 (s, 3H). Eu(Tp 3Me,4CzPh,5Me Synthesis of 2: NaBH4 (0.265 g, 7.01 mmol) and HP2 were synthesized. 3Me,4CzPh,5Me (6.85 g, 33.0 mmol) were mixed and stirred, then gradually heated to 220 °C for 5 h. After the reaction was complete, most of the pyrazole was removed by sublimation (~10 Pa) at a temperature gradient of 160 °C-90 °C-room temperature to obtain a white solid (5.361 g), which was sodium tris(3,5-dimethyl-4-(4-carbazolylphenyl)-1-pyrazolyl)borohydride (NaTp). 3Me,4CzPh,5Me ESI-MS (m / z): [MK] − Calculated value [C] 33 H 34 BN6] − 815.80; Measured value 815.81. In NaTp 3Me,4CzPh,5Me Adding a tetrahydrofuran solution of EuI2 (0.889 g, 2.200 mmol) to a tetrahydrofuran solution of (3.671 g, 4.500 mmol) resulted in the precipitation of a red solid upon stirring. The mixture was stirred overnight and filtered to obtain an orange-red solid (2.60 g, 1.496 mmol, 68.0%). Elemental analysis calculated C. 138 H 98 B2EuN 12 : C, 79.00%, H, 4.71%, N, 8.01%; Measured values: C, 78.05%, H, 4.93%, N, 7.89%. Synthesis of 2-(carbazole-9-yl)ethyl acetate: 10.033 g carbazole (60.000 mmol), 13.268 g potassium carbonate (96.000 mmol), and 100 mL ultradry N,N-dimethylformamide were placed in a 250 mL three-necked flask. The system was repeatedly evacuated and purged with nitrogen three times. The temperature was raised to 55 °C and the reaction was stirred for 2 h. 10.6 mL of ethyl bromoacetate (96.0 mmol) was slowly added dropwise to the system, and the reaction was maintained at 55 °C with stirring for 12 h. For post-treatment, the system was first cooled to room temperature, and 100 mL of water was added. The mixture was filtered, and the filter cake was collected and dried in a vacuum oven at 70 °C to obtain 14.838 g of a light yellow solid powder, with a yield of 97.6%. 1 H NMR (400 MHz, Chloroform- d ) δ 8.10 (d, J = 7.8 Hz, 2H), 7.46 (d,J = 8.3 Hz, 2H), 7.34 (d, J =8.2 Hz, 2H), 7.26 (t, J = 7.5 Hz, 2H), 5.00 (s, 2H), 4.20 (q, J = 7.1 Hz, 2H), 1.22 (t, J = 7.1 Hz, 3H). Synthesis of 1-(carbazole-9-yl)pentane-2,4-dione: 2.400 g of sodium hydride and 40 mL of redistilled tetrahydrofuran were placed in a 250 mL three-necked flask. The system was repeatedly evacuated and purged with nitrogen three times. 3.485 g of acetone was slowly added dropwise. After stirring at room temperature for 1 h, 10.13 g of a 40 mL tetrahydrofuran solution of 2-(carbazole-9-yl)ethyl acetate was slowly added dropwise, and the mixture was stirred at room temperature for 12 h. For post-treatment, an appropriate amount of dilute sulfuric acid aqueous solution was slowly added dropwise to adjust the pH to 13. The mixture was filtered, and the filtrate was collected and concentrated by rotary evaporation. The pH was further adjusted to 5, and the mixture was filtered again. The filter cake was collected to obtain 10.107 g of a light yellow solid powder, with a yield of 95.8%. 1 H NMR (400 MHz, Chloroform- d ) δ 15.37 (s, 1H), 8.13 (d, J = 7.8 Hz, 2H), 7.48 (t, J = 7.1 Hz,2H), 7.35 - 7.25 (m, 4H), 5.11 (s, 1H), 4.98 (s, 2H), 1.87 (s, 3H). 9-((5-methylpyrazol-3-yl)methyl)carbazole (HPz) 3Me,5CzCH2 Synthesis of 1-(carbazol-9-yl)pentane-2,4-dione (35.00 mmol) and 50 mL of ethanol were placed in a 100 mL round-bottom flask, and 2.4 mL of hydrazine hydrate (42 mmol) was added dropwise with stirring. The system was repeatedly evacuated and purged with nitrogen three times, heated to reflux, and stirred for 12 h. For post-treatment, the system was placed at -10 °C to cool and crystallize, and 5.168 g of white needle-like crystals were obtained by filtration, with a yield of 56.5%. 1 H NMR (400 MHz, DMSO- d 6) δ 12.31 (s, 1H), 8.13 (d, J = 7.7 Hz, 2H), 7.68 (d, J = 8.2 Hz, 2H), 7.44 (t, J= 7.1 Hz, 2H), 7.19 (t, J = 7.0 Hz, 2H), 5.71 (s, 1H), 5.48 (s, 2H), 2.07 (s, 3H). Eu(Tp 3Me,5CzCH2 Synthesis of 2: using NaBH4 (0.265 g, 7.01 mmol), HP2 3Me,5CzCH2 Using EuI2 (0.889 g, 2.200 mmol) as raw materials, according to the Eu(Tp) formula above... 3Me,4CzPh,5Me The synthetic route of )2 yielded an orange-red solid Eu(Tp) 3Me,5CzCH2 )2 (1.80 g, 1.254 mmol, 57.0%). Elemental analysis calculated C 98 H 84 B2EuN 12 :C, 70.04%, H, 4.08%, N, 6.91%; Measured values: C, 69.28%, H, 3.93%, N, 6.76%. Synthesis of 4-bromo-1-triphenylmethylpyrazole: 7.348 g of 4-bromopyrazole (50.00 mmol) was placed in a 250 mL three-necked flask and dissolved in 70 mL of N,N-dimethylformamide. The mixture was evacuated and purged with nitrogen three times. Under ice bath conditions, 6.172 g of potassium tert-butoxide (55.00 mmol) and 15.333 g of triphenylchloromethane (55.00 mmol) were slowly added. The system was heated to room temperature and stirred for 1 h. For post-treatment, a large amount of water was added to the system, and the mixture was filtered. The filter cake was collected, dried, dissolved in 300 mL of tetrahydrofuran, and recrystallized by rotary evaporation. The resulting light yellow solid powder was obtained by filtration, yielding 18.312 g (94.1%). 1 H NMR (400 MHz, Chloroform- d ) δ 7.62 (s, 1H), 7.38 (s, 1H), 7.35 - 7.27 (m, 9H), 7.16 - 7.09 (m, 6H). Synthesis of 9-(1-triphenylmethylpyrazol-4-yl)carbazole: 2.857 g cuprous iodide (15.00 mmol), 2.703 g o-phenanthroline (15.00 mmol), and 4.146 g potassium carbonate (30 mmol) were placed in a 250 mL three-necked flask. 100 mL of N,N-dimethylformamide was added. The system was evacuated and purged with nitrogen three times. After stirring at room temperature for ten minutes, 6.019 g carbazole (36.00 mmol) and 11.68 g 4-bromo-1-triphenylmethylpyrazol (30.00 mmol) were added. The evacuation and nitrogen purging were repeated three times. The system was heated to 110 °C and stirred for 24 h. In the post-processing, the system was first cooled to room temperature, filtered, and the filter residue was washed with N,N-dimethylformamide. The filtrate was collected, and 200 mL of water was added dropwise to the filtrate with stirring. The filtrate was then filtered, and the filter cake was collected. The crude product was dissolved in 100 mL of dichloromethane, and the insoluble matter was removed by filtration. The filtrate was dried by rotary evaporation and recrystallized with acetone to obtain 9.622 g of white solid powder, with a yield of 65.8%. 1 H NMR (400 MHz, Acetone- d 6) δ 8.16 (d, J = 7.8 Hz, 2H),7.99 (s, 1H), 7.86 (s, 1H), 7.48 - 7.29 (m, 19H), 7.25 (t, J = 7.4 Hz, 2H). Synthesis of 9-(pyrazol-4-yl)carbazole: 4.756 g of 9-(1-triphenylmethylpyrazol-4-yl)carbazole was placed in a 100 mL round-bottom flask, and 18 mL of hydrogen chloride methanol solution (1.1 mol / L) was added. -1 20 mmol) and 15 mL of dichloromethane were added. The system was heated to 40 °C and stirred for 3 h. For post-treatment, the system was first cooled to room temperature, the solvent was removed by rotary evaporation, and recrystallized from toluene to give 2.360 g of white solid powder, yield 87.5%. 1 H NMR (400 MHz, Methanol- d 4) δ 8.51 (s, 2H), 8.14 (d, J = 7.8 Hz, 2H), 7.50 - 7.33 (m, 4H), 7.29 (t, J = 7.4 Hz, 2H). Eu(Tp 4Cz Synthesis of 2: using NaBH4 (0.265 g, 7.01 mmol), HP2 4CzUsing EuI2 (4.84 g, 28.00 mmol) and EuI2 (0.889 g, 2.200 mmol) as raw materials, according to the Eu(Tp) formula above... 3Me,4CzPh,5Me The synthetic route of )2 yielded an orange-red solid Eu(Tp) 4Cz )2 (2.50 g, 2.028 mmol, 92.2%). Elemental analysis calculated C. 66 H 60 B2EuN 12 : C, 58.92%, H, 3.72%, N, 6.33%; Measured values: C, 58.42%, H, 3.50%, N, 6.06%. 3,5-Dimethyl-4-pentafluoroethylpyrazole: In a 250 mL three-necked flask, 7.03 g (32.2 mmol) of 3-pentafluoroethyl-2,4-pentanedione, 2.65 g (38.6 mmol) of hydrazine hydrochloride, and 80 mL of anhydrous ethanol were added. While stirring, a solution of sodium carbonate (1.15 g, 9.7 mmol) in 40 mL of water was added dropwise using a constant pressure dropping funnel. The mixture was heated under reflux for 12 h. After cooling, the ethanol was removed by rotary evaporation, 10 mL of water was added, and the mixture was extracted twice with 100 mL of dichloromethane. The combined organic phases were dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated to obtain a pale yellow liquid, HPz. 3Me,4C2F5,5Me (4.62 g, 24.8 mmol). Yield: 77.0%. 1 H NMR (C6D6): δ 6.20 (d, J =2.3 Hz, 1H), δ 6.85 (t, J =1.2 Hz, 1H), δ 12.90(br, 1H). ESI-MS: m / z [M+H] + =187.03.

[0024] Eu(Tp 3Me,4C2F5,Me Synthesis of 2: using NaBH4 (0.265 g, 7.01 mmol), HP2 3Me,4C2F5,5Me Using EuI2 (0.889 g, 2.200 mmol) as raw materials, according to the Eu(Tp) formula above... 3Me,4CzPh,5Me The synthetic route of )2 yielded an orange-red solid Eu(Tp) 3Me,4C2F5,5Me )2 (1.34 g, 1.540 mmol, 35%). Calculated elemental analysis value C 42 H 36 B2EuN 12 F 30: C, 68.52%, H, 3.98%, N, 6.87%; Measured values: C, 68.26%, H, 3.22%, N, 6.36%. 3,5-Dimethyl-4-heptafluoroisopropylpyrazole: In a 250 mL three-necked flask, 7.56 g (30.0 mmol) of 3-heptafluoroisopropyl-2,4-pentanedione, 2.65 g (38.6 mmol) of hydrazine hydrochloride, and 80 mL of anhydrous ethanol were added. While stirring, a solution of sodium carbonate (1.15 g, 9.7 mmol) in 40 mL of water was added dropwise using a constant-pressure dropping funnel. The mixture was heated under reflux for 12 h. After cooling, the ethanol was removed by rotary evaporation, 10 mL of water was added, and the mixture was extracted twice with 100 mL of dichloromethane. The combined organic phases were dried over anhydrous sodium sulfate, filtered, and the solvent was evaporated to obtain a pale yellow liquid, HPz. 3Me,4C3F7,5Me (4.33 g, 22.9 mmol). Yield: 71.8%. 1 H NMR (C6D6): δ 6.28 (d, J =2.3 Hz, 1H), δ 6.91 (t, J =1.2 Hz, 1H), δ12.91 (br, 1H). ESI-MS: m / z [M+H] + =223.04.

[0025] Eu(Tp 3Me,4C3F7,Me Synthesis of 2: using NaBH4 (0.265 g, 7.01 mmol), HP2 3Me,4C3F7,5Me Using EuI2 (0.889 g, 2.200 mmol) as raw materials, according to the Eu(Tp) formula above... 3Me,4CzPh,5Me The synthetic route of )2 yielded an orange-red solid Eu(Tp) 3Me,4C3F7,5Me )2 (0.55 g, 6.5 mmol, 15%). Calculated elemental analysis value C 48 H 36 B2EuN 12 F 42 : C, 60.52%, H, 3.28%, N, 6.00%; Measured values: C, 59.93%, H, 3.05%, N, 5.92%. Example 2: Photophysical properties of the coordination compound The three complexes with the highest brightness under 365 nm ultraviolet light irradiation, Eu(Tp), were selected from the above complexes. 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 to Eu(Tp 3Me,4Ph,5Me)2 (The structure is shown below).

[0026] At room temperature, Eu(Tp) 3Et,4tBu,5Et )2 and Eu(Tp 3Me,4Ph,5Me Eu(Tp) is difficult to dissolve in common solvents (such as dichloromethane, tetrahydrofuran, acetonitrile, toluene, and n-hexane). 3Me,4Ad,5Me Eu(II)2 is soluble in dichloromethane, but its stability in dichloromethane is poor; the complex is oxidized during solution preparation and ceases to emit light. Therefore, the photoluminescence properties of the three complex solid powders were tested in this embodiment. The emission spectra of the three Eu(II) complexes are as follows: Figure 1 As shown. From Eu(Tp) 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 to Eu(Tp 3Me,4Ph,5Me The maximum emission wavelength of the )2 complex is red-shifted sequentially, Eu(Tp) 3Et,4tBu,5Et The solid powder has a PLQY of 80%, a maximum emission wavelength of 536 nm, a green emission color, and an excited-state lifetime of 675 ns. Eu(Tp) was measured. 3Me,4Ad,5Me The solid powder PLQY is 62%, and its state may correspond to its amorphous state. Unlike its crystalline form, which emits green and orange-red light, the powder sample showed a maximum emission wavelength of 560 nm and emitted yellow light. The emission decayed with a double-exponential lifetime, with excited-state lifetimes of 167 ns and 486 ns, respectively. Eu(Tp) 3Me,4Ph,5Me The solid powder PLQY is 60%, with a maximum emission wavelength of 625 nm, emitting red light, and an excited-state lifetime of 590 ns. The excited-state lifetimes of the three complexes are consistent with the excited-state lifetimes of Eu(II) complexes with df transitions reported in the literature.

[0027] Example 3: Air stability of the complex The air stability of the complexes was characterized by exposing solid powders of the complexes to air and measuring PLQY. Three complexes, Eu(Tp) 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 to Eu(Tp 3Me,4Ph,5Me The normalized change of PLQY over time is as follows: Figure 2 As shown. Eu(Tp) 3Et,4tBu,5Et Eu(Tp)2 exhibits good air stability; after 27 hours of exposure to air, PLQY retains 95% of its initial value. 3Me,4Ad,5Me )2 After exposure to air for 30 minutes, PLQY decayed to 50% of its initial value, and then slowly decayed to 30% of its initial value. Eu(Tp) 3Me,4Ph,5MeEu(II) complex exhibits poor air stability, failing to emit light after 10 minutes of air exposure, and the solid powder changes from red to brownish-yellow. This demonstrates that increasing the steric hindrance of the pyrazole boron ligand does indeed significantly improve the stability of the Eu(II) complex. In particular, increasing the steric hindrance of the pyrazole 3- and 5-position groups directly enhances the encapsulation of the central Eu(II) ligand.

[0028] Example 4: Thermal stability of the complex Thermogravimetric analysis was used to study Eu(Tp) 3Et,4tBu,5Et )2 and Eu(Tp 3Me,4Ad,5Me Thermal stability of 2 Figure 3 and Figure 4 Eu(Tp) 3Et,4tBu,5Et The temperature of weight loss of 2 T d The temperature at which 5% mass loss occurs is 360 °C, which is below the sublimation temperature of the complex, indicating very good thermal stability. Eu(Tp) 3Me,4Ad,5Me The weight loss below 100℃ originates from the loss of tetrahydrofuran, a solvent present in the sample. This corresponds to the elemental analysis results indicating the presence of the solvent. The weight loss temperature reaches as high as 420℃, demonstrating good thermal stability. Differential thermal analysis revealed that Eu(Tp) 3Et,4tBu,5Et )2 and Eu(Tp 3Me,4Ad,5Me Neither of them has a glass transition temperature.

[0029] Based on the above characterization results, the complex Eu(Tp) 3Et,4tBu,5Et )2 has higher luminous efficiency, better air stability and thermal stability, exhibiting the best overall performance and is the most promising candidate for preparing high-efficiency and stable OLEDs.

[0030] Example 5: Electroluminescent Device Considering that Eu(Tp) in the three complexes 3Et,4tBu,5Et Eu(Tp) has higher luminous efficiency, better air stability, and better thermal stability. The inventors of this invention used Eu(Tp) as the luminous efficiency. 3Et,4tBu,5Et Taking Eu(Tp)2 as an example, this type of coordination compound was studied as a light-emitting material in OLEDs. To screen Eu(Tp)2... 3Et,4tBu,5Et Eu(Tp)2 is the optimal host material for luminescent materials, and Eu(Tp)2 is prepared by vapor deposition. 3Et,4tBu,5Et A pure thin film of Eu(Tp)2 was prepared with a quantum yield of 60%. Doped thin films of Eu(Tp)2 in the host materials mCBP, SiCzCz, mCP, and oCBP were also prepared with a doping concentration of 10 wt%, yielding quantum yields of 46%, 98%, 85%, and 79%, respectively. 3Et,4tBu,5Et Doping SiCzCz and oCBP as light-emitting layers may have better performance.

[0031] Using SiCzCz and oCBP as the main materials, Com 1 and SiCzCz as hole transport layer materials, and mSiTrz and Liq as electron transport layer materials, the following device structures were fabricated: D1: ITO / HATCN (10 nm) / Com 1 (50 nm) / SiCzCz: Eu(Tp 3Et,4tBu,5Et )2(10 wt%, 20nm) / mSiTrz (5 nm) / mSiTrz:Liq(20 nm) / LiF(1 nm) / Al(100 nm) D2: ITO / HATCN (10 nm) / Com 1 (50 nm) / oCBP: Eu(Tp 3Et,4tBu,5Et )2(10 wt%, 20nm) / mSiTrz (5 nm) / mSiTrz:Liq(20 nm) / LiF(1 nm) / Al(100 nm) D3: ITO / HATCN (10 nm) / SiCzCz (50 nm) / SiCzCz: Eu(Tp 3Et,4tBu,5Et )2(10 wt%,20 nm) / mSiTrz (5 nm) / mSiTrz:Liq(20 nm) / LiF(1 nm) / Al(100 nm) D4: ITO / HATCN (10 nm) / SiCzCz (50 nm) / oCBP: Eu(Tp 3Et,4tBu,5Et )2(10 wt%, 20nm) / mSiTrz (5 nm) / mSiTrz:Liq(20 nm) / LiF(1 nm) / Al(100 nm) The electroluminescence properties of devices D1-D4 are summarized in Table 1. As can be seen from the table, D1, with SiCzCz as the host material and Com1 as the hole transport material, exhibits the best electroluminescence performance, with a maximum external quantum efficiency of 16.9% and a maximum luminance of 33770 cd / m². −2 The current density-voltage-luminance curves and power-luminance-EQE curves for device D1 are listed below. Figure 5 and Figure 6 .

[0032] Table 1 Main parameters of devices D1-D4 a Start-up voltage; b Maximum EQE; c 1000 cd m -2 EQE at brightness;d Maximum brightness; e 1000 cd m -2 CIE under brightness Example 6: Improved Stability of Electroluminescent Devices Considering the improvement in air stability of the complex due to the increased steric hindrance of the pyrazole boron ligand, this embodiment further determined the Eu(Tp) content. 3Et,4tBu,5Et Eu(Tp)2 and Eu(II) complex 3Me,5Me The device stability comparison of Eu(Tp)2, in which Eu(Tp)2 3Me,5Me )2 Due to the small burial volume, the luminescence is significantly reduced under ultraviolet light after exposure to air, and the air stability is poor.

[0033] D1: ITO / HATCN (10 nm) / Com 1 (50 nm) / SiCzCz: Eu(Tp 3Et,4tBu,5Et )2(10 wt%, 20nm) / mSiTrz (5 nm) / mSiTrz:Liq(20 nm) / LiF(1 nm) / Al(100 nm) D5: ITO / HATCN (10 nm) / Com 1 (50 nm) / SiCzCz: Eu(Tp 3Me,5Me )2(10 wt%, 20nm) / mSiTrz (5 nm) / mSiTrz:Liq(20 nm) / LiF(1 nm) / Al(100 nm) The electroluminescence properties of devices D1 and D5 are summarized in Table 2. As can be seen from the table, Eu(Tp) exhibits greater steric hindrance. 3Et ,4tBu,5Et )2. Significant improvements were observed in device efficiency, brightness, and stability. Device efficiency increased by 2.81 times, brightness by 6.65 times, and stability by 4.49 times. This indicates that the introduction of sterically hindered substituents not only improved thermal and air stability but also significantly enhanced the stability of the electroluminescent device. Figure 7It is evident that the brightness of device D5 decays to 90% of its initial value after approximately 400 seconds, while the brightness of device D1 remains above 90% of its initial value after 1800 seconds. Improving the stability of electroluminescent devices is crucial for their commercial application: contact between the luminescent material and oxygen and water in the air leads to decomposition of the luminescent material and a rapid decline in the performance of the electroluminescent device. Therefore, device encapsulation is critical during the fabrication process. To ensure that electroluminescent devices can operate in an oxygen- and water-free environment for as long as possible, significant time and effort are required to develop effective encapsulation structures. However, effective encapsulation structures can significantly increase the manufacturing cost of electroluminescent devices, accounting for approximately 20% of the total cost, thus hindering their commercial application. The electroluminescent material provided by this invention exhibits excellent device stability and is not sensitive to oxygen and water in the air. This greatly reduces the requirements for water- and oxygen-proof encapsulation of the electroluminescent device, inevitably leading to a substantial reduction in manufacturing costs and ultimately facilitating its commercial application.

[0034] Table 2 Main parameters of devices D1 and D5 In the table above, LT 90 The time it takes for the device brightness to drop to 90% of its initial value, expressed in seconds.

[0035] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tripyrazole boron Eu(II) complex, characterized in that, The tripyrazole boron Eu(II) complex has the following structure: Among them, R, R 1 R 2 It is independently selected from any one of hydrogen, unsubstituted alkyl, alkoxy, unsubstituted alkenyl, halogen-substituted alkenyl, unsubstituted alkynyl, unsubstituted phenyl, substituted phenyl, unsubstituted aryl, substituted aryl, alkyl or heterocyclic containing O, N, or S coordination sites; Preferably, R, R 1 R 2 It is independently selected from any one of hydrogen, unsubstituted C1-C18 alkyl, unsubstituted C1-C18 alkoxy, halogen atom, C2-C18 unsubstituted alkenyl, C2-C18 halogen-substituted alkenyl, C2-C18 unsubstituted alkynyl, phenyl, substituted phenyl, C6-C18 unsubstituted aryl, and heterocycles containing O, N, or S coordination sites; Preferably, R, R 1 R 2 It is independently selected from any one of hydrogen, methyl, ethyl, tert-butyl, phenyl, and 1-adamantyl; In a further preferred embodiment, R is hydrogen; Further preferred, R 1 Independently selected from methyl and ethyl; Further preferred, R 2 It is independently selected from tert-butyl and 1-adamantyl.

2. The tripyrazole boron Eu(II) complex according to claim 1, characterized in that, The tripyrazolone boron Eu(II) complex is Eu(Tp) 3Et,4tBu,5Et 2. Eu(Tp) 3Me,4Ad,5Me )2 or Eu(Tp 3Me,4Ph,5Me )2, its structure is as follows: Preferably, the tripyrazole boron Eu(II) complex is Eu(Tp) 3Et,4tBu,5Et )2.

3. An electroluminescent device, characterized in that, The light-emitting device includes a cathode, an anode, and a light-emitting layer located between the cathode and the anode, wherein the light-emitting layer includes the tripyrazole boron Eu(II) complex as described in claim 1 or 2.

4. The electroluminescent device according to claim 3, characterized in that, The light-emitting layer is a mixture of a guest material and a host material, wherein the guest material includes the tripyrazole boron Eu(II) complex as described in claim 1 or 2, and the host material is selected from host materials with good thermal stability; Preferably, the main material is selected from any one of mCBP, SiCzCz, oCBP, and mCP; Preferably, the doping concentration is 1 wt%-20 wt%, more preferably 5 wt%-12 wt%, more preferably 7 wt%-10 wt%, and most preferably 10 wt%, wherein the doping concentration is the percentage of the mass of the guest material to the total mass of the guest material and the host material.

5. The electroluminescent device according to claim 3 or 4, characterized in that, The electroluminescent device further includes an electron transport layer located between the cathode and the light-emitting layer; Preferably, the electron transport layer is an electron transport material with good thermal stability; Preferably, the electron transport layer comprises mSiTrz, DPPyA, and / or Liq; More preferably, the electron transport layer comprises mSiTrz and / or DPPyc.

6. The electroluminescent device according to claim 3 or 4, characterized in that, The electroluminescent device further includes a hole transport layer located between the anode and the light-emitting layer; Preferably, the hole transport layer is a hole transport material with good thermal stability; Preferably, the hole transport layer includes mCBP, Com1, and / or SiCzCz; More preferably, the hole transport layer comprises SiCzCz and / or Com 1.

7. The electroluminescent device according to claim 5 or 6, characterized in that, The electroluminescent device further includes an electron transport layer located between the cathode and the light-emitting layer, and a hole transport layer located between the anode and the light-emitting layer; Preferably, the hole transport layer comprises SiCzCz and / or Com 1, and the electron transport layer comprises mSiTrz and / or DPPyA; Preferably, the electroluminescent device further includes an electron injection layer located between the cathode and the electron transport layer, and the electroluminescent device further includes a hole injection layer located between the anode and the hole transport layer; More preferably, the electron injection layer comprises Liq, and the hole injection layer comprises HATCN.

8. The electroluminescent device according to any one of claims 3-7, characterized in that, The thickness of the light-emitting layer is 1-50 nm, preferably 10-40 nm, more preferably 15-30 nm, more preferably 20-25 nm, and most preferably 20 nm.

9. The electroluminescent device according to claim 3, characterized in that, The electroluminescent device structure is: ITO / HATCN (10 nm) / Com 1 (50 nm) / SiCzCz (12 nm) / SiCzCz: Eu(Tp) 3Et,4tBu,5Et )2(10 wt%, 24 nm) / SiCzCz (6 nm) / mSiTrz (5 nm) / mSiTrz:Liq(31 nm) / LiF(1 nm) / Al(100 nm).

Images