Hole transport material and application thereof in preparation of organic electroluminescent device

Abstract

The invention provides a hole transport material and application thereof in preparation of an organic electroluminescent device. Belongs to the technical field of electroluminescent materials, the prepared hole transport material is a high triplet state energy level styrene functionalized hole transport material with 3, 3-di (9H-carbazole-9-yl) biphenyl as a core, the material is prepared by introducing a styrene functional group on the core structure of the 3, 3-di (9H-carbazole-9-yl) biphenyl, and the hole transport material is a high triplet state energy level styrene functionalized hole transport material with the core structure of the 3, 3-di (9H-carbazole-9-yl) biphenyl. The compound has high triplet energy level, excellent hole transport performance and good film-forming property, and can be widely applied to the fields of organic electroluminescent devices, organic photovoltaic devices and the like.

Description

Technical Field

[0001] This invention belongs to the field of electroluminescent materials technology, specifically a hole transport material and its application in the preparation of organic electroluminescent devices. Background Technology

[0002] Circularly polarized organic light-emitting diodes (OLEDs) have great potential and have attracted much attention in fields such as next-generation displays. Chiral π-conjugated polymers (especially chiral polyfluorene derivatives) are ideal choices for their self-emissive layers due to their high carrier mobility and ease of assembly into ordered structures, which is beneficial for achieving high efficiency. g EL Its strong circularly polarized emission contributes to high-performance devices, but its low triplet energy level limits its multicolor emission potential. Summary of the Invention

[0003] To address the limitation of the low triplet energy level of chiral polyfluorene derivatives on their multicolor emission potential, strategic methods are needed to control the exciton dynamics within the device. Interface engineering is a feasible approach, the core of which is to introduce a high triplet energy hole transport layer near the chiral polyfluorene main layer. Therefore, this invention provides a hole transport material and its application in the fabrication of organic circularly polarized electroluminescent devices.

[0004] Technical solution: A hole transport material, wherein the hole transport material is p-mCBP, and the structural formula is as follows: .

[0005] Furthermore, the method for synthesizing the hole transport material is as follows: (1) Under nitrogen atmosphere, 4-hydroxycarbazole, TBAB and anhydrous K2CO3 were added to ethyl acetate. After stirring at room temperature for a period of time, iodomethane was introduced and the reaction system was refluxed at 80 °C until the reaction was complete. The solvent was removed by evaporation of the reactants, and the residue was poured into water and extracted with CH2Cl2. The organic layer obtained by extraction was washed, dried and purified to obtain white solid M1. The synthetic route is as follows:

[0006] (2) Under nitrogen atmosphere, 3,3'-dibromobiphenyl, Pd2(dba)3, P(t-Bu)3, and BuONa- t M1 was added to toluene, and the reaction system was heated to 110℃-120℃ until the reaction was complete. The solvent was evaporated to remove the solvent, and the resulting mixture was poured into water and extracted with CH2Cl2. The organic layer obtained after extraction was washed, dried, and purified to obtain a white solid M2. The synthetic route is as follows:

[0007] (3) In a nitrogen atmosphere, boron tribromide was added to a mixed solution of ultra-dry dichloromethane and M2. The reaction was carried out at 0°C because it was necessary to react in an ice-water environment. After the reaction was completed, the solvent was evaporated and the resulting mixture was poured into water and extracted with CH2Cl2. The organic layer obtained by extraction was washed, dried and purified to obtain white solid M3. The synthetic route is as follows:

[0008] (4) Under nitrogen atmosphere, 4-vinylphenol, 1,6-dibromohexane and anhydrous potassium carbonate were added to acetone, heated to 60 °C and stirred. After the reaction was completed, the solvent was evaporated and the resulting mixture was poured into water and extracted with CH2Cl2. The organic layer obtained by extraction was washed, dried and purified to obtain white solid M4. The synthetic route is as follows:

[0009] (5) Under nitrogen atmosphere, M3, M4, anhydrous potassium carbonate and TBAB were added to acetonitrile; the mixture was heated to 80°C and stirred to react. After the reaction was completed, the solvent was evaporated and removed. The resulting mixture was poured into water and extracted with CH2Cl2. The extracted organic layer was washed, dried and purified to obtain a white solid p-mCBP. The synthetic route is as follows: .

[0010] The hole transport material described above can be used to prepare hole transport layers in organic circularly polarized electroluminescent devices.

[0011] The organic circularly polarized electroluminescent device includes an ITO substrate, a hole injection layer, a hole transport layer, and an emission layer sequentially disposed on the ITO substrate, and an electron injection layer and a cathode disposed on the emission layer.

[0012] The method for fabricating the organic circularly polarized electroluminescent device includes the following steps: Step 1: Spin-coat poly(3,4-ethylenedioxythiophene) and vinyl sulfonate onto an ITO substrate, and after drying, obtain a hole injection layer; Step 2: Spin-coat a chloroform solution of p-mCBP onto the hole injection layer, and anneal it to obtain the hole transport layer; Step 3: Spin-coating the emitter layer material onto the hole transport layer, followed by annealing to obtain the emitter layer; The emitter layer material is R / S doped with 4CzIPN. 0.1 -(PF8) 0.9 R / S doped with 4CzIPN and OXD-7 0.1 -(PF8) 0.9 R / S of DMAC-TRZ doped 0.1-(PF8) 0.9 R / S of DMAC-TRZ and OXD-7 doped 0.1 -(PF8) 0.9 ; Step 4: Deposit calcium on the surface of the emitter layer as an electron injection layer, and deposit silver as a cathode.

[0013] Furthermore, in step one, the mass ratio of poly(3,4-ethylenedioxythiophene) to vinyl sulfonate is 1:6; In step two, the concentration of the chloroform solution of p-mCBP is 4 mg / mL; In step three, the R / S of 4CzIPN doped 0.1 -(PF8) 0.9 The content of 4CzIPN was 3 wt%. R / S doped with 4CzIPN and OXD-7 0.1 -(PF8) 0.9 In this mixture, the content of 4CzIPN is 3 wt%, and the content of OXD-7 is 5 wt%. R / S of DMAC-TRZ doped 0.1 -(PF8) 0.9 The content of DMAC-TRZ in the sample was 3 wt%; R / S of DMAC-TRZ and OXD-7 doped 0.1 -(PF8) 0.9 The content of DMAC-TRZ was 3 wt%, and the content of OXD-7 was 5 wt%.

[0014] Beneficial effects 1) The hole transport material prepared in this invention is a high triplet-level styrene-functionalized hole transport material (p-mCBP) with 3,3-bis(9H-carbazole-9-yl)biphenyl as its core. This material is prepared by introducing styrene functional groups into the 3,3-bis(9H-carbazole-9-yl)biphenyl core structure. It possesses high triplet energy levels, excellent hole transport performance, and good film-forming properties, and can be widely used in organic electroluminescent devices, organic photovoltaic devices, and other fields.

[0015] The hole transport material developed in this invention exhibits excellent film-forming properties, enabling the formation of uniform and dense thin films during the film-forming process. This effectively reduces film defects and improves the consistency and stability of device performance. The hole transport material also demonstrates good chemical and thermal stability, effectively extending the lifespan of electronic devices. Furthermore, the preparation method of this hole transport material is simple and can effectively reduce exciton quenching, thereby improving the luminous efficiency of devices. 2) The high triplet hole transport material prepared by this invention effectively overcomes the inherent low triplet energy limitation of highly ordered chiral polyfluorene, releasing their potential as a multifunctional chiral host for high-performance organic circularly polarized electroluminescent green light-emitting devices.

[0016] The hole transport material of this invention enhances the hole transport capability of the material by introducing styrene functional groups, enabling holes to transport more efficiently in the device, thereby improving device performance. Devices manufactured without p-mCBP exhibit performance solely derived from p-mCBP. R / S The PF8 host exhibits deep blue emission. Crucially, by using cross-linked p-mCBP as the HTL, strong green circularly polarized emission is generated at a distance of 500 nm from the chiral emitter. g EL The value is as high as 0.01. The preparation of hole transport materials in this invention has promoted the development of high-performance CP-EL devices. Attached Figure Description

[0017] Figure 1 This is a graph showing the test results of the basic photophysical properties of the p-mCBP compound solution in Example 2 of this invention.

[0018] Figure 2 The graph shows the test results of the thermodynamic properties and crosslinking properties of the p-mCBP compound and the thin film in Example 3 of this invention.

[0019] Figure 3 This is a schematic diagram of the organic circularly polarized light-emitting device prepared by the p-mCBP compound in Example 4 of the present invention.

[0020] Figure 4 These are the performance parameters of the device prepared in Embodiment 4 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0022] In this embodiment of the invention, the suppliers of TBAB, Pd2(dba)3, and (t-Bu)3P are: Anaiji Chemical & 3A (Anhui Zesheng Technology Co., Ltd.); the suppliers of 4-hydroxycarbazole, iodomethane, 3,3'-dibromobiphenyl, and 4-vinylphenol are: Bid Pharmaceutical Technology Co., Ltd.; the suppliers of R / S5011 and 1,6-dibromohexane are: Shanghai Maclean Biochemical Technology Co., Ltd.; the suppliers of dichloromethane and ethyl acetate are: Sinopharm Chemical Reagent Co., Ltd.; the suppliers of toluene, t-BuONa, anhydrous potassium carbonate, anhydrous sodium sulfate, and acetonitrile are: Nanjing Wanqing Co., Ltd.; the supplier of PF8 is: Shenzhen Ruixun; the suppliers of poly(3,4-ethylenedioxythiophene) and vinyl sulfonate are: Shenzhen Xinzhoubang Technology Co., Ltd.; the suppliers of 4CzIPN, OXD-7, and DMAC-TRZ are: Xi'an Baolai Optoelectronic Technology Co., Ltd.; and the supplier of TPBi is: Aode Technology. The structural formulas of R / S5011, PF8, 4CzIPN, OXD-7, and DMAC-TRZ are as follows:

[0023] In the following embodiments, R / S 0.1 -(PF8) 0.9 Preparation method: R / S5011 and PF8 were dissolved in xylene at an appropriate ratio to prepare a stock solution with a concentration of 8 mg / mL. The R / S5011 solution was then incorporated into the PF8 solution at a mass ratio of 10%. Subsequently, 35 μL of the mixed solution was pipetted onto an ITO substrate and spin-coated (3000 rpm, 30 s) to form a uniform film. The film was then annealed at 160°C for 5 minutes to form the chiral co-assembled film R / S5011. 0.1 -(PF8) 0.9 After annealing, a 1-hour solvent vapor exposure (SVE) treatment was performed, following this procedure: During the experiment, the hot plate surface was maintained at 50°C to promote the evaporation of toluene in the small petri dish placed on top. Using an insulated plastic bottle cap as a support, the R / S coated petri dish was placed... 0.1 -(PF8) 0.9 The ITO glass slide was raised approximately 1 cm above the surface of the heating plate. This setup avoided direct thermal contact, thus preventing the film from potentially crystallizing into the α phase. A closed chamber was formed by inverting a large petri dish over the heating plate surface. The duration of continuous vapor exposure was set to one hour.

[0024] Example 1: Preparation of p-mCBP 1) The synthetic route of p-mCBP is as follows:

[0025] Specific preparation method of p-mCBP: Step (1): Under nitrogen atmosphere, 4-hydroxycarbazole (1.0 eq, 27.2 mmol, 5.0 g), TBAB (0.01 eq, 0.27 mmol, 0.087 g), and anhydrous K2CO3 (2.0 eq, 54.5 mmol, 7.5 g) were added to 70 mL of ethyl acetate, and the mixture was stirred at room temperature for 1 h. Then, iodomethane (3.0 eq, 81.6 mmol, 5 mL) was introduced, and the reaction mixture was refluxed at 80 °C until completion, monitored by thin-layer chromatography (TLC). After the reaction was complete, the solvent was evaporated, and the residue was poured into water (50 mL) and extracted with CH2Cl2 (3 × 30 mL). The bound organic layer was washed with saturated brine, dried on anhydrous Na2SO4, and concentrated under vacuum. The crude product was purified by silica gel column chromatography to give a white solid M1 (65% yield, 3.5 g).

[0026] Compound M1 (8 mg) was dissolved in 0.5 mL of a deuterated reagent, and its structure was characterized using a 400 Hz NMR instrument. The structure of M1 was determined by 1H NMR spectroscopy as follows: M1 proton NMR spectrum determination data: 1 H NMR (CDCl3, 400 MHz) δ (ppm): 8.32 (d, J =7.8 Hz, 1H), 7.93 (s, 1H), 7.40-7.29 (m, 3H), 7.26-7.20 (m, 1H), 6.99 (d, J =8.4 Hz, 1H), 6.66 (d, J = 8.0 Hz, 1H), 4.05 (s, 3H). Step (2): Under nitrogen atmosphere, 3,3-dibromobiphenyl (1.0 eq, 2.54 mmol, 792 mg), Pd2(dba)3 (0.22 eq, 0.56 mmol, 513 mg), P(t-Bu)3 (0.22 eq, 0.56 mmol, 114 mg) and BuONa- t(2.2 eq, 5.6 mmol, 539 mg) was added to a mixture of M1 (2.2 eq, 5.58 mmol, 1.1 g) in 20 mL of toluene. The reaction was then heated to 120°C and maintained overnight until completion (monitored by TLC). After the reaction was complete, the solvent was evaporated, the resulting mixture was poured into water, extracted with CH2Cl2, the bound organic layer was washed with saturated brine, dried on anhydrous Na2SO4, and concentrated under vacuum to give an oily product. The crude product was purified by silica gel column chromatography to give a white solid M2 (yield 32%, 1.3 g).

[0027] Compound M2 (8 mg) was dissolved in 0.5 mL of a deuterated reagent, and its structure was characterized using a 400 Hz NMR instrument. The structure of M2 was determined by 1H NMR spectroscopy as follows: M2 1H NMR spectrum determination data: 1 H NMR (CDCl3, 400 MHz) δ (ppm): 8.42 (d, J =4.4 Hz, 2H), 7.87 (s, 2H), 7.71 (d, J = 13.2 Hz, 4H), 7.59 (s, 2H), 7.49-7.28(m, 8H), 7.09 (d, J = 4.4 Hz, 2H), 6.76 (d, J = 4.8 Hz, 2H), 4.13 (s, 6H). Step (3): Under nitrogen atmosphere, treat the mixture of M2 (1 eq, 2.2 mmol, 1.2 g) in ultradry dichloromethane (DCM, 20 mL) with boron tribromide (BBr3, 2.5 eq, 5.5 mmol, 0.6 mL) and react at 0 °C until complete as monitored by TLC. After the reaction is complete, evaporate to remove the solvent, pour the resulting mixture into water, extract with CH2Cl2, wash the bound organic layer with saturated brine, dry on anhydrous Na2SO4, and concentrate under vacuum to obtain an oily product. Purify the crude product by silica gel column chromatography; M3 is a white solid (yield 35.4%, 400 mg).

[0028] Compound M3 (8 mg) was dissolved in 0.5 mL of a deuterated reagent, and its structure was characterized using a 400 Hz NMR instrument. The structure of M3 was determined by 1H NMR spectroscopy as follows: M3 1H NMR spectrum determination data: 1 H NMR (400 MHz, DMSO- d 6) δ (ppm): 10.32 (s, 2H), 8.27 (d, J = 7.6 Hz, 2H), 8.01 (s, 2H), 7.92 (d, J = 8.0 Hz, 2H), 7.76(t, J = 7.8 Hz, 2H), 7.63 (d, J = 7.6 Hz, 2H), 7.44-7.32 (m, 4H), 7.28-7.16(m, 4H), 6.90 (d, J = 8.0 Hz, 2H), 6.70 (d, J = 8.0 Hz, 2H). Step (4): Under a nitrogen atmosphere, 4-vinylphenol (1.0 eq, 15 mmol, 1.8 g), 1,6-dibromohexane (1.5 eq, 22.5 mmol, 5.5 g), and anhydrous K₂CO₃ (3.0 eq, 45 mmol, 6.2 g) were added to 25 mL of acetone. The mixture was heated to 60 °C and stirred for 18 hours. After the reaction was complete, the solvent was evaporated, the resulting mixture was poured into water, extracted with CH₂Cl₂, the bound organic layer was washed with saturated brine, dried on anhydrous Na₂SO₄, and concentrated under vacuum to obtain an oily product. The crude product was purified by silica gel column chromatography to obtain a white solid M₄ (yield 57%, 2.4 g).

[0029] Compound M4 (8 mg) was dissolved in 0.5 mL of a deuterated reagent, and its structure was characterized using a 400 Hz NMR instrument. The structure of M4 was determined by 1H NMR spectroscopy as follows: M4 1H NMR spectrum determination data: 1 H NMR (CDCl3, 400 MHz) δ (ppm): 7.37-7.30 (m,2H), 6.88-6.82 (m, 2H), 6.66 (dd, J = 17.6, 10.8 Hz, 1H), 5.60 (dd, J = 17.6, 1.2 Hz, 1H), 5.12 (dd, J = 10.8, 1.2 Hz, 1H), 3.96 (t, J = 6.4 Hz, 2H), 3.43(t, J = 6.8 Hz, 2H), 1.90 (m, J=6.6 Hz, 2H), 1.79 (m, J = 6.6 Hz, 2H), 1.55-1.46 (m, 4H). (5) Under nitrogen atmosphere, M3 (1.0 eq, 0.75 mmol, 0.385 g), M4 (3.0 eq, 2.25 mmol, 0.637 g), K2CO3 (3.0 eq, 3.0 mmol, 0.415 g), and TBAB (0.1 eq, 0.075 mmol, 0.025 g) were added to 6 mL of acetonitrile solution. The mixture was heated to 80 °C and stirred for 32 hours. After the reaction was complete, the solvent was evaporated, and the resulting mixture was poured into water and extracted with CH2Cl2. The bound organic layer was washed with saturated brine, dried on anhydrous Na2SO4, and concentrated under vacuum to obtain an oily product. The crude product was purified by silica gel column chromatography to obtain a white solid p-mCBP (yield 54%, 0.37 g).

[0030] The compound p-mCBP (8 mg) was dissolved in 0.5 mL of a deuterated reagent, and its structure was characterized using a 400 Hz NMR instrument. The structure of p-mCBP was determined by 1H NMR spectroscopy as follows: p-mCBP proton NMR spectrum determination data: 1 H NMR (CDCl3, 400 MHz) δ (ppm): 8.41 (d, J = 7.2 Hz, 2H), 7.86 (s, 2H), 7.70 (dt, J = 15.4, 8.0 Hz, 4H), 7.58 (d, J =7.6 Hz, 2H), 7.44 (d, J = 8.0 Hz, 2H), 7.39 (d, J = 5.6 Hz, 2H), 7.35-7.27(m, 8H), 7.06 (d, J = 8.0 Hz, 2H), 6.86 (d, J = 8.8 Hz, 4H), 6.77-6.61 (m,4H), 5.61 (d, J = 18.8 Hz, 2H), 5.12 (d, J = 10.8 Hz, 2H), 4.29 (t, J = 6.4Hz, 4H), 4.01 (t, J= 6.4 Hz, 4H), 2.10-2.04 (m, 4H), 1.91-1.85 (m, 4H), 1.74(t, J = 8.4 Hz, 4H), 1.70-1.62 (m, 4H). Example 2: Photophysical property testing of compound p-mCBP solution p-mCBP was prepared into 1×10 -5 A mol / L toluene solution was subjected to fluorescence spectroscopy using a Hitachi F-4700 fluorescence spectrometer. The obtained data were imported into Origin software for normalization and plotting. Figure 1 In (a), the luminescence lifetime of the solution was measured using an Edinburgh FLS980 steady-state-transient fluorescence spectrometer. The obtained data were imported into Origin software for normalization and plotting. Figure 1 (b) and (c) in the text.

[0031] like Figure 1 As shown in (a), the absorption peak between 220 and 300 nm is assigned to the π-π* transition of the benzene ring, while the weak absorption peak between 300 and 350 nm originates from the n-π* transition. Furthermore, p-mCBP exhibits emission peaks at 342 nm and 355 nm, and a phosphorescence peak at 475 nm was measured at 77 K. These spectral characteristics indicate that the singlet (S1) and triplet (T1) energy levels are 3.62 eV and 2.82 eV, respectively. Figure 1 As shown in (b), the fluorescence lifetime of this compound is 7.8 ns.

[0032] Example 3: Thermodynamic properties and film crosslinking properties of compound p-mCBP The p-mCBP compound powder was placed in a crucible, and the glass transition temperature was obtained in the temperature range of 25 °C to 300 °C under nitrogen atmosphere using a DSC214 differential scanning calorimeter. T g). Import the test data into Origin software for plotting. Figure 2 (a) The sample was then prepared as a 4 mg / mL chloroform solution and spin-coated onto a quartz plate at 3000 rpm under a nitrogen atmosphere. After heating at 160°C for 30 min, a p-mCBP crosslinking network was prepared. UV spectra before and after crosslinking and cleaning were measured, and the data were imported into Origin software for plotting. Figure 2 (b) is an example. Then, the surface roughness of the cross-linked film was tested using atomic force microscopy, and the resulting images were obtained. Figure 2 (c) and (d).

[0033] Figure 2 In Figure (a), differential scanning calorimetry (DSC) was used to find the appropriate crosslinking temperature for p-mCBP. The DSC plot showed distinct endothermic and exothermic peaks near 160 °C, indicating that the crosslinking reaction occurred within this temperature range. The absence of a phase transition during the second heating scan confirmed that the crosslinking groups were almost completely consumed during the formation of the polymer network. Subsequently, Figure 2 In section (b), the crosslinking efficiency of p-mCBP was evaluated by assessing the solvent resistance of its spin-coated film using UV-Vis spectroscopy. After rinsing with xylene, the crosslinked film showed minimal absorbance loss, retaining 82% of its original absorbance, indicating high solvent resistance. This demonstrates that p-mCBP possesses efficient thermal self-crosslinking and good optical stability. Furthermore, Figure 2 (c) and (d) show the surface morphology of the crosslinked film analyzed by atomic force microscopy (AFM) before and after rinsing with xylene. The average roughness increased slightly from 0.406 nm (before rinsing) to 0.664 nm (after rinsing), indicating no significant structural degradation. The moderate increase in surface roughness may enhance interfacial contact with the subsequent emitter layer and expand the exciton recombination region.

[0034] Example 4: Fabrication of an organic circularly polarized electroluminescent green light-emitting device based on p-mCBP material and performance testing of the device. (1) Figure 3 This is a schematic diagram of the AF structure of the device prepared based on the compound p-mCBP. The preparation method is as follows: Step 1: Fabricate a hole injection layer (HIL) on an ITO substrate; A commercial indium tin oxide (ITO) coated glass substrate (1.4 × 1.5 cm²) was cleaned sequentially with dichloromethane, deionized water, acetone, and ethanol, each cleaning step lasting 20 minutes. After drying at 120 °C, the cleaned substrate was subjected to UV ozone treatment for 20 minutes. Subsequently, poly(3,4-ethylenedioxythiophene):vinyl sulfonate (PEDOT:PSS) at a mass ratio of 1:6 was spin-coated onto the ITO substrate at 3000 rpm for 30 seconds as a hole injection layer (HIL), and then dried at 120 °C for 30 minutes; the thickness of the hole injection layer (HTL) was 25 nm.

[0035] Step 2: Spin-coat a chloroform solution of p-mCBP onto the hole injection layer (HTL) to prepare the hole transport layer; For devices containing a hole injection layer (HTL), 4 mg of the hole transport material p-mCBP was weighed and dissolved in 1 mL of chloroform solution. After thorough stirring and dissolution, it was spin-coated onto the surface of PEDOT:PSS (hole injection layer) at 3000 rpm for 30 seconds. Then, it was annealed at 160°C for 30 minutes under a nitrogen atmosphere. The thickness of the hole transport layer was 20 nm.

[0036] Devices A and CF have the same hole transport layer (HTL) and hole transport layer fabrication method. Device B does not have a hole injection layer (HTL).

[0037] Step 3: Fabrication of Emitting Layers (EMLs); The emitter layers (EMLs) of the device AF were prepared by spin coating under a nitrogen atmosphere with parameters set to 3000 rpm for 30 s. After annealing at 160 °C for 5 min, the EMLs were subjected to SVE treatment.

[0038] The emitter layers (EMLs) of the device AF are different, among which: The emitter layer in device A has a thickness of 30 nm and is made of R. 0.1 -(PF8) 0.9。

[0039] Device B has an emitter layer thickness of 30 nm, and the material is R-type silicon doped with 3 wt% 4CzIPN. 0.1 -(PF8) 0.9。

[0040] The emitter layer in device C has a thickness of 30 nm and is made of R-type material doped with 3 wt% 4CzIPN. 0.1 -(PF8) 0.9。

[0041] The emitter layer in device D has a thickness of 30 nm and is made of R / S material doped with 3 wt% 4CzIPN. 0.1 -(PF8) 0.9。

[0042] The emitter layer in device E has a thickness of 30 nm and is made of R / S material doped with 3 wt% 4CzIPN and 5 wt% OXD-7. 0.1 -(PF8) 0.9。

[0043] The emitter layer in device F has a thickness of 30 nm and is made of R / S material doped with 3 wt% DMAC-TRZ and 5 wt% OXD-7. 0.1 -(PF8) 0.9。

[0044] Step 4: Subsequently, all devices undergo vacuum deposition: at 5 × 10⁻⁶-4 At a base pressure of Pa, calcium (Ca, 10 nm) is deposited on the surface of EMLs as an electron injection layer (EIL), followed by silver (Ag, 100 nm) as a cathode.

[0045] In addition, after depositing a 35 nm thick layer of 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBi) as an electron transport layer (ETL) for device D, calcium and silver were then deposited.

[0046] (2) The performance of the fabricated device was tested, and the results are as follows: Devices fabricated using p-mCBP as the hole transport layer exhibit green emission, while devices without p-mCBP as the hole transport layer emit blue emission.

[0047] The electroluminescence spectrum of the device AF was measured using a PR-655 spectrometer, and the obtained data were imported into Origin software for plotting. Figure 4 (a) in the middle Figure 4 Figure (b) illustrates the process from the non-chiral emitter 4CzIPN to the chiral host R. 0.1 -(PF8) 0.9 The energy reverse transfer can be suppressed by using an HTL with a higher triplet energy level, specifically through the interface energy transfer mechanism mediated by this HTL. The device performance of devices E and F was tested using a Keithley 2602A source table and accompanying testing software. The obtained data were imported into Origin software for plotting. Figure 4 In (c) and (d), devices E and F were tested using a JASCO CPL-300 spectrometer to measure their circularly polarized electroluminescence spectra and electroluminescence asymmetry factors. The obtained data were imported into Origin software for plotting. Figure 4 (e) and (f) in the text.

[0048] like Figure 4 As shown in (a), devices A, B, and D can observe the origin from R. 0.1 -(PF8) 0.9 A distinct blue EL was observed, but no EL from 4CzIPN (λ) was detected. EL Electroluminescence at 500 nm was observed in device C. However, after introducing p-mCBP as a hole transport layer (HTL), device C exhibited strong EL at 508 nm, a characteristic of 4CzIPN emission. In device D, the introduction of TPBi altered the exciton recombination region, resulting in luminescence still originating from R. 0.1 -(PF8) 0.9 The distinct blue EL. These results indicate that inhibition of the chiral emitter 4CzIPN to the chiral host R0.1 -(PF8) 0.9 The reverse energy transfer can be achieved through HTL-mediated interface energy transfer with higher triplet energy levels. Figure 4 The above conclusion is also illustrated in (b).

[0049] To further improve the electron emission contribution and device efficiency of 4CzIPN, an electron transport host material (OXD-7) was added to the electron transport layers (EMLs) of device C to enhance electron transport performance. This resulted in improved electron transport performance in device E. R and E S Its manufacturing process, with the following structure: ITO / PEDOT: PSS / p-mCBP / R / S 0.1 -(PF8) 0.9 : 3 wt% 4CzIPN: 5 wt% OXD-7 / Ca / Ag. As expected, the EL spectrum is dominated by green emission at 500 nm, which is characteristic of 4CzIPN. Furthermore, the device E... R and E S It exhibits improved performance: maximum brightness ( L max The values ​​are 1240 / 1166 cd / m³. 2 Maximum current efficiency ( CE max The values ​​are 0.61 / 0.58 cd / A, obtained through... Figure 4 (c) and (d) are obtained. Crucially, device E... R and E S A significant mirrored CP-EL signal was observed at 500 nm, with electroluminescence asymmetry factors of -0.012 / +0.009. Figure 4 As can be seen in (e) and (f).

[0050] Based on this strategy, another green emitter (DMAC-TRZ) was selected as the circularly polarized emitter to construct the device F: ITO / PEDOT: PSS / p-mCBP / R / S 0.1 -(PF8) 0.9 3 wt% DMAC-TRZ; 5 wt% OXD-7 / Ca / Ag. Device F also exhibits a unique and strong green CP-EL signal at 498 nm. g EL The value is -0.009 / +0.011, and the device performance is... L max = 1126 / 1110 cd / m 2 , CE max = 1.1 / 1.36 cd / A, given by Figure 4 You can see it in CF.

[0051] Example 4 demonstrates an efficient strategy for generating CP-ELs from a non-chiral green emitter using a chiral polyfluorene host and a high triplet energy HTL.

[0052] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention.

Claims

1. A hole transport material, characterized in that, The hole transport material is p-mCBP, with the following structural formula: 。 2. The hole transport material according to claim 1, characterized in that, The method for synthesizing the hole transport material is as follows: (1) Under nitrogen atmosphere, 4-hydroxycarbazole, TBAB and anhydrous K2CO3 were added to ethyl acetate. After stirring at room temperature for a period of time, iodomethane was introduced and the reaction system was refluxed at 80 °C until the reaction was complete. The solvent was removed by evaporation of the reactants, and the residue was poured into water and extracted with CH2Cl2. The organic layer obtained by extraction was washed, dried and purified to obtain white solid M1. The synthetic route is as follows: ； (2) Under nitrogen atmosphere, 3,3'-dibromobiphenyl, Pd2(dba)3, P(t-Bu)3, BuONa-t and M1 were added to toluene. The reaction system was heated to 110℃-120℃ until the reaction was complete. The solvent was evaporated and removed. The resulting mixture was poured into water and extracted with CH2Cl2. The extracted organic layer was washed, dried and purified to obtain white solid M2. The synthetic route is as follows: ； (3) In a nitrogen atmosphere, boron tribromide was added to a mixed solution of ultra-dry dichloromethane and M2. The reaction was carried out at 0°C because it was necessary to react in an ice-water environment. After the reaction was completed, the solvent was evaporated and the resulting mixture was poured into water and extracted with CH2Cl2. The organic layer obtained by extraction was washed, dried and purified to obtain white solid M3. The synthetic route is as follows: ； (4) Under nitrogen atmosphere, 4-vinylphenol, 1,6-dibromohexane and anhydrous potassium carbonate were added to acetone, heated to 60 °C and stirred. After the reaction was completed, the solvent was evaporated and the resulting mixture was poured into water and extracted with CH2Cl2. The organic layer obtained by extraction was washed, dried and purified to obtain white solid M4. The synthetic route is as follows: ； (5) Under nitrogen atmosphere, M3, M4, anhydrous potassium carbonate and TBAB were added to acetonitrile; the mixture was heated to 80°C and stirred to react. After the reaction was completed, the solvent was evaporated and removed. The resulting mixture was poured into water and extracted with CH2Cl2. The extracted organic layer was washed, dried and purified to obtain a white solid p-mCBP. The synthetic route is as follows: 。 3. The application of the hole transport material according to any one of claims 1-2 in the fabrication of organic circularly polarized electroluminescent devices, characterized in that, Used to prepare hole transport layers.

4. The application according to claim 3, characterized in that, The organic circularly polarized electroluminescent device includes an ITO substrate, a hole injection layer, a hole transport layer, and an emission layer sequentially disposed on the ITO substrate, and an electron injection layer and a cathode disposed on the emission layer.

5. The application according to claim 4, characterized in that, The method for fabricating the organic circularly polarized electroluminescent device includes the following steps: Step 1: Spin-coat poly(3,4-ethylenedioxythiophene) and vinyl sulfonate onto an ITO substrate, and after drying, obtain a hole injection layer; Step 2: Spin-coat a chloroform solution of p-mCBP onto the hole injection layer, and anneal it to obtain the hole transport layer; Step 3: Spin-coating the emitter layer material onto the hole transport layer, followed by annealing to obtain the emitter layer; The emitter layer material is R / S doped with 4CzIPN. 0.1 -(PF8) 0.9 R / S doped with 4CzIPN and OXD-7 0.1 -(PF8) 0.9 R / S of DMAC-TRZ doped 0.1 -(PF8) 0.9 R / S of DMAC-TRZ and OXD-7 doped 0.1 -(PF8) 0.9 ; Step 4: Deposit calcium on the surface of the emitter layer as an electron injection layer, and deposit silver as a cathode.

6. The application according to claim 5, characterized in that, In step one, the mass ratio of poly(3,4-ethylenedioxythiophene) to vinyl sulfonate is 1:6; In step two, the concentration of the chloroform solution of p-mCBP is 4 mg / mL; In step three, the R / S of 4CzIPN doped 0.1 -(PF8) 0.9 The content of 4CzIPN was 3 wt%. R / S doped with 4CzIPN and OXD-7 0.1 -(PF8) 0.9 In this mixture, the content of 4CzIPN is 3 wt%, and the content of OXD-7 is 5 wt%. R / S of DMAC-TRZ doped 0.1 -(PF8) 0.9 The content of DMAC-TRZ in the sample was 3 wt%; R / S of DMAC-TRZ and OXD-7 doped 0.1 -(PF8) 0.9 The content of DMAC-TRZ was 3 wt%, and the content of OXD-7 was 5 wt%.

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