An OLED device with high exciton utilization efficiency and a preparation method thereof

Abstract

The present invention relates to the technical field of organic electroluminescent materials, and specifically discloses an OLED device with high exciton utilization efficiency and a preparation method thereof, which includes a multi-layer structure stacked up and down, and successively from top to bottom are an ITO substrate, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a spacer layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode layer; the material of the organic light-emitting layer is a fluorescent material doped with a high exciton utilization efficiency and a double host material mcp and TPBi. By using a fluorescent material with high exciton utilization efficiency in combination with a host material to prepare the organic light-emitting layer, the OLED device prepared by the present invention has a high exciton utilization efficiency, and the fluorescent material has a matching molecular energy level, a high luminous efficiency, and good film-forming properties, and can be used as an efficient OLED doping material.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electroluminescent materials, and particularly relates to an OLED device with high exciton utilization efficiency and a preparation method thereof. Background Art

[0002] The scientific origin of organic electroluminescence technology can be traced back to the early 1960s. At that time, researchers observed that eosin dyes have delayed fluorescence characteristics, and at the same time, breakthrough progress was made in the electroluminescence phenomenon of phenanthrene crystals under high-pressure conditions. In the contemporary optoelectronic field, such devices have become the core components of ultra-thin display and energy-saving lighting technologies. Analyzed from the dimension of the evolution of luminescent materials, the first-generation fluorescent OLEDs are limited by the exciton statistical distribution law, and the theoretical limit of their internal quantum efficiency is only 25% - this is because 75% of the excitons generated by electrical excitation are in the triplet state and cannot participate in the radiative recombination process. To break through this bottleneck, the second-generation phosphorescent system emerged. With the strong spin-orbit coupling effect of noble metal coordination compounds such as iridium and platinum, the intersystem crossing dynamics process is significantly accelerated, and theoretically, an almost 100% full exciton utilization efficiency can be achieved. However, this system faces two challenges: the high cost of noble metal resources and the technical barrier of insufficient blue light color gamut purity. Even with the triplet-triplet annihilation enhancement mechanism, the theoretical IQE upper limit of blue light devices is still limited to the 62.5% level.

[0003] It is worth noting that the emergence of the thermally activated delayed fluorescence (TADF) mechanism has opened up a new path. This technology realizes the theoretical limit of exciton utilization efficiency without relying on noble metals by precisely regulating the singlet-triplet energy gap (ΔEst). According to Hückel's molecular orbital theory, the energy gap value ΔEst is positively correlated with the overlap degree of the wave functions of the molecular frontier orbitals (HOMO-LUMO), which prompts researchers to adopt the donor-acceptor (D-A) molecular engineering strategy for orbital spatial separation design. However, such structures are prone to significant molecular configuration relaxation, resulting in an increase in Stokes shift and broadening of the electroluminescence spectrum, and its full width at half maximum is usually extended to the range of 70 - 100 nm, seriously restricting the color purity of the device. Summary of the Invention

[0004] The purpose of the present invention is to provide an OLED device with high exciton utilization efficiency and a preparation method thereof to solve the problems of large energy loss and low external quantum efficiency of OLED devices in the prior art.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: An OLED device with high exciton utilization efficiency includes a multi-layer structure stacked up and down, which are, from top to bottom in sequence, an ITO substrate, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a spacer layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode layer;

[0006] The material of the organic light-emitting layer is a doped fluorescent material with high exciton utilization efficiency, the double host materials mcp and TPBi.

[0007] Furthermore, the fluorescent material is a blue, sky-blue and green light material based on the "hot exciton" 3-hydroxyacetophenone isomer.

[0008] Furthermore, the blue light material is DCZPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(9H-carbazol-9-yl)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows:

[0009] 。

[0010] Furthermore, the sky-blue light material is DPhCZPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows:

[0011] 。

[0012] Furthermore, the green light material is DPAPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(diphenylamino)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows:

[0013] 。

[0014] Furthermore, the anode layer is an inorganic material, specifically indium tin oxide and indium zinc oxide;

[0015] The material of the hole injection layer is MoO3 or HAT-CN, and the thickness is 1-5 nm;

[0016] The material of the hole transport layer is TAPC, and the thickness is 30-40 nm;

[0017] The material of the electron blocking layer is TCTA, and the thickness is 5-30 nm;

[0018] The material of the spacer layer is mcp, and the thickness is 5-10 nm;

[0019] The organic light-emitting layer contains 0.1%-35% of the fluorescent material, 65%-99.9% of the double host materials mcp and TPBi by mass ratio. The double host materials mcp and TPBi are in a mass ratio of 1:3-1:1, and the thickness is 25-50 nm;

[0020] The material of the hole blocking layer is TPBi, and the thickness is 5 - 10 nm;

[0021] The material of the electron transport layer is tmpypb, and the thickness is 30 - 40 nm;

[0022] The material of the electron injection layer is LiF, and the thickness is 1 - 3 nm;

[0023] The cathode layer is any one of gold, silver, copper, aluminum, and magnesium, and the thickness is 100 - 150 nm.

[0024] A method for preparing an OLED device with high exciton utilization rate, used to prepare the above-mentioned OLED device with high exciton utilization rate, includes the following steps:

[0025] S1. Use acetone, absolute ethanol, and ultrapure water to ultrasonically clean the ITO glass substrate for 15 minutes each time, a total of 4 times. After cleaning, put the ITO glass substrate into a drying oven and dry it for 2 hours;

[0026] S2. Perform plasma pretreatment on the surface of the ITO glass substrate to clean the organic substances adhering to the surface of the ITO glass substrate;

[0027] S3. Vacuum deposit a hole injection layer on the anode layer of the ITO glass substrate;

[0028] S4. Vacuum deposit a hole transport layer on the hole injection layer;

[0029] S5. Vacuum deposit an electron blocking layer on the hole transport layer;

[0030] S6. Vacuum deposit a spacer layer on the electron blocking layer;

[0031] S7. Vacuum deposit an organic light-emitting layer on the spacer layer;

[0032] S8. Vacuum deposit a hole blocking layer on the organic light-emitting layer;

[0033] S9. Vacuum deposit an electron transport layer on the hole blocking layer;

[0034] S10. Vacuum deposit an electron injection layer on the electron transport layer;

[0035] S11. Vacuum deposit a cathode layer on the electron injection layer to obtain an OLED device with high exciton utilization rate.

[0036] Furthermore, the preparation method of the organic light-emitting layer using a blue light material is as follows:

[0037] S7.1. Take methyl p-bromobenzoate and p-bromoacetophenone and mix them into a dry three-necked flask. Add sodium hydride into a dry dropping funnel, seal it with a rubber stopper and a sealing film, evacuate and blow nitrogen through a double-row tube three times, insert a nitrogen balloon, and add tetrahydrofuran to dissolve, cool the entire device to 0 °C, adjust the droplet falling speed to a constant, and then heat to reflux temperature for reaction. After the reaction, neutralize the reaction solution with dilute hydrochloric acid, separate the organic phase, wash it twice with brine, and then dry it with anhydrous sodium sulfate. After concentrating the organic phase, recrystallize it with ethyl acetate, filter it, and vacuum dry it to obtain gray flaky crystals (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one;

[0038] S7.2. The gray flaky crystals obtained in S7.1, carbazole, palladium acetate, tri-tert-butylphosphine tetrafluoroborate and sodium tert-butoxide were added to a dry Schlenk reaction tube. After evacuation and nitrogen bubbling three times using a double-row tube, deoxygenated xylene was injected. After the reaction, the mixture was cooled to room temperature, extracted three times with dichloromethane and water, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. After purification by a silica gel column, a light yellow solid was obtained. The reaction formula is:

[0039] .

[0040] Furthermore, the preparation method of the organic light-emitting layer using the sky blue light material is as follows:

[0041] The (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one, 3,6-diphenylcarbazole, palladium acetate, tri-tert-butylphosphine tetrafluoroborate and sodium tert-butoxide prepared in step S7.1 were added to a dry Schlenk reaction tube, and vacuumed and nitrogen-filled the tube three times using a double-row tube, and then deoxygenated xylene was injected. After the reaction, the mixture was cooled to room temperature, extracted three times with dichloromethane and water, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. After purification by silica gel column, a yellow solid was obtained, and the reaction formula is:

[0042] .

[0043] Furthermore, the preparation method of the organic light-emitting layer using the green light material is as follows:

[0044] The (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one prepared in step S7.1, diphenylamine, palladium acetate, tri-tert-butylphosphine tetrafluoroborate and sodium tert-butoxide were added to a dry Schlenk reaction tube, and vacuumed and nitrogen-filled the tube three times using a double-row tube, and then deoxygenated xylene was injected. After the reaction, the mixture was cooled to room temperature, extracted three times with dichloromethane and water, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. After purification by silica gel column, a yellow solid was obtained, and the reaction formula is:

[0045] 。

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. By using a fluorescent material with high exciton utilization efficiency in combination with a host material to prepare the organic light-emitting layer, the OLED device prepared by the present invention has a high exciton utilization efficiency. Moreover, the molecular energy levels of this fluorescent material are matched, the luminous efficiency is high, and it has good film-forming properties, and can be used as an efficient OLED doping material.

[0048] 2. The blue, sky-blue, and green light materials based on the "hot exciton" 3-hydroxyacetophenone isomers of the present invention are simple to prepare and inexpensive. The OLED devices all have high device efficiency and high exciton utilization efficiency. The maximum external quantum efficiency of the prepared blue OLED device is 4.68%, the maximum external quantum efficiency of the prepared sky-blue OLED device is 12.59%, and the maximum external quantum efficiency of the prepared green OLED device is 23.66%. The external quantum efficiencies of both DPHCZPDO and DPAPDO luminescent materials exceed the theoretical maximum value (5%) of traditional fluorescent OLED devices.

[0049] 3. The luminescent materials based on 3-hydroxyacetophenone isomers of the present invention have both an electron acceptor and an ESIPT group (β-diketone core), and can achieve full-color gamut coverage from blue light to green light through molecular structure regulation, and are suitable for fields such as flexible display, high-resolution OLED screens, and solid-state lighting. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The schematic diagrams in the specification that form a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0051] Figure 1 are the structural formulas of DCZPDO, DPHCZPDO, and DPAPDO of the present invention. From top to bottom on the left are the structural formulas of the alcohol configurations of DCZPDO, DPHCZPDO, and DPAPDO respectively, and from top to bottom on the right are the structural formulas of the keto configurations of DCZPDO, DPHCZPDO, and DPAPDO respectively.

[0052] Figure 2 is the schematic structural diagram of the OLED device of the present invention.

[0053] Figure 3 is the comparison chart of the photoluminescence spectra and lifetimes of DCZPDO, DPHCZPDO, and DPAPDO of the present invention before and after purging nitrogen in toluene solvent.

[0054] Figure 4It is the electroluminescence spectrum diagram of the blue light OLED device of the present invention.

[0055] Figure 5 It is the electroluminescence spectrum diagram of the sky blue light OLED device of the present invention.

[0056] Figure 6 It is the electroluminescence spectrum diagram of the green light OLED device of the present invention.

[0057] Figure 7 It is the current density-voltage-brightness curve diagram of the OLED device of the present invention.

[0058] Figure 8 It is the current efficiency-brightness diagram of the OLED device of the present invention.

[0059] Figure 9 It is the power efficiency-brightness diagram of the OLED device of the present invention.

[0060] Figure 10 It is the brightness-external quantum efficiency diagram of the OLED device of the present invention.

[0061] Figure 11 It is the molecular energy level diagram of the blue light material DCZPDO of the present invention.

[0062] Figure 12 It is the molecular energy level diagram of the sky blue light material DPHCZPDO of the present invention.

[0063] Figure 13 It is the molecular energy level diagram of the green light material DPAPDO of the present invention.

[0064] Figure 14 It is the horizontal dipole ratio diagram of the blue light material DCZPDO of the present invention.

[0065] Figure 15 It is the horizontal dipole ratio diagram of the sky blue light material DPHCZPDO of the present invention.

[0066] Figure 16 It is the horizontal dipole ratio diagram of the green light material DPAPDO of the present invention.

[0067] Figure 17 It is the hydrogen spectrum of the blue light material DCZPDO of the present invention.

[0068] Figure 18 It is the hydrogen spectrum of the sky blue light material DPHCZPDO of the present invention.

[0069] Figure 19 It is the hydrogen spectrum of the green light material DPAPDO of the present invention.

[0070] Figure 20This is a diagram showing the relationship between the solvent polarity and Stokes shift of DCZPDO, DPHCZPDO, and DPAPDO from top to bottom for the present invention.

[0071] Figure 21 This is the crystal structure diagram of DPAPDO for the present invention.

[0072] Among them: B1 is the OLED device of DCZPDO, B2 is the OLED device based on DPHCZPDO, and G1 is the OLED device based on DPAPDO. Detailed implementation manners

[0073] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0074] Please refer to Figure 1-21 。

[0075] Embodiment 1:

[0076] The OLED device of the present invention with high exciton utilization rate includes a multi-layer structure stacked up and down, which are, from top to bottom, an ITO substrate, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a spacer layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode layer;

[0077] The material of the organic light-emitting layer is a blue light material doped with a "thermal exciton" 3-hydroxyacetone isomer, a double host material mcp, and TPBi.

[0078] The blue light material is DCZPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(9H-carbazol-9-yl)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows:

[0079] 。

[0080] The anode layer is an inorganic material, specifically indium tin oxide;

[0081] The material of the hole injection layer is MoO3, and the thickness is 1 nm;

[0082] The material of the hole transport layer is TAPC, and the thickness is 40 nm;

[0083] The material of the electron blocking layer is TCTA, and the thickness is 5 nm;

[0084] The material of the spacer layer is mcp, and the thickness is 5 nm;

[0085] The organic light-emitting layer consists of 20% blue light material, 80% double host materials mcp and TPBi by mass ratio. The mass ratio of the double host materials mcp and TPBi is 1:3, and the thickness is 25 nm;

[0086] The material of the hole blocking layer is TPBi, and the thickness is 5 nm;

[0087] The material of the electron transport layer is tmpypb, and the thickness is 30 nm;

[0088] The material of the electron injection layer is LiF, and the thickness is 3 nm;

[0089] The cathode layer is any one of gold, silver, copper, aluminum, and magnesium, and the thickness is 100 nm.

[0090] A method for preparing an OLED device with high exciton utilization rate, which is used to prepare the above-mentioned OLED device with high exciton utilization rate, includes the following steps:

[0091] S1. Use acetone, absolute ethanol and ultrapure water to ultrasonically clean the ITO glass substrate for 15 minutes each time, and clean it 4 times in total. The purpose is to clean the impurities on the ITO surface and make the cleanliness of the ITO surface meet the requirements of vacuum evaporation. After cleaning, the ITO glass substrate is placed in a drying oven and dried for 2 hours;

[0092] S2. Perform plasma pretreatment on the surface of the ITO glass substrate to clean the organic substances adhered to the surface of the ITO glass substrate, improve the work function of the ITO to a certain extent, and reduce the injection barrier of holes;

[0093] S3. Vacuum deposit a hole injection layer on the anode layer of the ITO glass substrate at a vacuum evaporation rate of 2 Hz / s;

[0094] S4. Vacuum deposit a hole transport layer on the hole injection layer at a vacuum evaporation rate of 2 Hz / s;

[0095] S5. Vacuum deposit an electron blocking layer on the hole transport layer at a vacuum evaporation rate of 2 Hz / s;

[0096] S6. Vacuum deposit a spacer layer on the electron blocking layer at a vacuum evaporation rate of 2 Hz / s;

[0097] S7. Vacuum deposit an organic light-emitting layer on the spacer layer at a vacuum evaporation rate of 2 Hz / s;

[0098] S8. Vacuum deposit a hole blocking layer on the organic light-emitting layer at a deposition rate of 2 Hz / s;

[0099] S9. Vacuum deposit an electron transport layer on the hole blocking layer at a deposition rate of 2 Hz / s;

[0100] S10. Vacuum deposit an electron injection layer on the electron transport layer at a deposition rate of 0.1 Hz / s;

[0101] S11. Vacuum deposit a cathode layer on the electron injection layer to obtain an OLED device with high exciton utilization efficiency.

[0102] The specific steps of the plasma pretreatment are as follows:

[0103] 1. Open the nitrogen valve, fill nitrogen to 1.1 x 10 5 Pa, open the chamber, close the nitrogen valve, and take out the flat glass;

[0104] 2. Blow the ITO glass substrate clean with a nitrogen gun, then place it at the mold position of the flat glass and push it into the correct position with tweezers;

[0105] 3. Close the chamber door, evacuate with a vacuum pump for 3 min (below 6 Pa), then open the oxygen valve and introduce O2 for 5 min;

[0106] 4. Turn off the bottom display meter;

[0107] 5. Turn on the "power" of the CTP-2000. When the inside of the chamber turns bright white with a purple tint, start timing for 30 s, then turn off the "power", the oxygen valve, and the vacuum pump;

[0108] 6. After the treatment is completed, loosen the chamber door screws, open the nitrogen valve to fill nitrogen, and open the chamber;

[0109] 7. Take out the wafer, close the chamber door, evacuate to 6 Pa, and then turn off the vacuum pump.

[0110] The preparation method of the organic light-emitting layer using a blue light material is as follows:

[0111] S7.1. Take methyl p-bromobenzoate (6 g, 27.9 mmol) and p-bromoacetophenone (4.98 g, 25 mmol) and mix them in a 250 ml dry three-necked flask. Add sodium hydride (1.52 g, 63.3 mmol) into a dry constant pressure dropping funnel. Use rubber stoppers and sealing films to seal the joints of the device and the mouths of the three-necked flask and the dropping funnel. After vacuuming and bubbling nitrogen through a double-row tube three times, insert a nitrogen balloon and add tetrahydrofuran to dissolve. Cool the entire device to 0 °C, adjust the droplet falling speed to 1 drop / s, and heat to 60 °C after 30 min for 16 min. h. After the reaction, the reaction solution was neutralized with 10% dilute hydrochloric acid. The organic phase was separated, washed twice with brine and dried over anhydrous sodium sulfate. The organic phase was concentrated and recrystallized with ethyl acetate. After filtration, it was dried under vacuum to obtain gray flaky crystals (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one. Hydrogen spectrum analysis: 1 H NMR (400 MHz, Chloroform-d) δ7.89–7.80 (m, 4 H), 7.68–7.57 (m, 4 H), 6.77 (s, 1 H);

[0112] S7.2. Take the gray flaky crystals (0.5 g, 1.13 mmol), carbazole (0.51 g, 3.05 mmol), palladium acetate (0.014 g, 0.065 mmol), tri-tert-butylphosphine tetrafluoroborate (0.0056 g, 0.19 mmol) and sodium tert-butoxide (0.29 g, 3.05 mmol) obtained in S7.1 and add them to a dry 50 ml Schlenk reaction tube. After vacuuming and bubbling nitrogen three times with a double-row tube, inject 20 ml of deoxygenated xylene, react at 130 °C for 48 h, cool to room temperature, extract three times with dichloromethane and water, dry with anhydrous sodium sulfate, and remove the solvent under reduced pressure. Theoretically, 0.73 g of solid product should be obtained. After purification by silica gel column, 0.55 g of light yellow solid was obtained with a yield of 75.77%. The reaction formula is:

[0113] .

[0114] As the doping concentration of blue light material DCZPDO increases (2.5%→35%), the emission color of the device remains stable in the blue light range, and EQE max Stable in the range of 3.28~4.68%.

[0115] Figure 3 a in the figure is the photoluminescence spectrum of DCZPDO material before and after nitrogen bubbling in toluene solvent;

[0116] Figure 3In this, d is the transient lifetime spectrogram of the DCZPDO material before and after purging nitrogen in toluene solvent.

[0117] Example 2:

[0118] An OLED device with high exciton utilization rate, including a multi-layer structure stacked up and down, which are, from top to bottom in sequence, an ITO substrate, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a spacer layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode layer;

[0119] The material of the organic light-emitting layer is doped with a fluorescent material with high exciton utilization rate, a double host material mcp and TPBi.

[0120] The fluorescent material is a sky blue light material based on the "hot exciton" 3-hydroxypropenone isomer.

[0121] The sky blue light material is DPhCZPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl)-3-hydroxyprop-2-en-1-one, and its molecular structural formula is as follows:

[0122] 。

[0123] The anode layer is an inorganic material, specifically indium tin oxide and indium zinc oxide;

[0124] The material of the hole injection layer is MoO3, and the thickness is 2 nm;

[0125] The material of the hole transport layer is TAPC, and the thickness is 30 nm;

[0126] The material of the electron blocking layer is TCTA, and the thickness is 30 nm;

[0127] The material of the spacer layer is mcp, and the thickness is 10 nm;

[0128] The organic light-emitting layer contains 20% of the sky blue light material, 80% of the double host materials mcp and TPBi by mass ratio, and the double host materials mcp and TPBi are in a mass ratio of 1:1, and the thickness is 40 nm;

[0129] The material of the hole blocking layer is TPBi, and the thickness is 10 nm;

[0130] The material of the electron transport layer is tmpypb, and the thickness is 30 nm;

[0131] The material of the electron injection layer is LiF, and the thickness is 1 nm;

[0132] The cathode layer is any one of gold, silver, copper, aluminum and magnesium, and has a thickness of 100 nm.

[0133] Method for preparing an organic light-emitting layer using sky blue light material:

[0134] S7.1. Take methyl p-bromobenzoate (6 g, 27.9 mmol) and p-bromoacetophenone (4.98 g, 25 mmol) and mix them in a 250 ml dry three-necked flask. Add sodium hydride (1.52 g, 63.3 mmol) into a dry constant pressure dropping funnel. Use rubber stoppers and sealing films to seal the joints of the device and the mouths of the three-necked flask and the dropping funnel. After vacuuming and bubbling nitrogen through a double-row tube three times, insert a nitrogen balloon and add tetrahydrofuran to dissolve. Cool the entire device to 0 °C, adjust the droplet falling speed to 1 drop / s, and heat to 60 °C after 30 min for 16 min. h. After the reaction, the reaction solution was neutralized with 10% dilute hydrochloric acid. The organic phase was separated, washed twice with brine and dried over anhydrous sodium sulfate. The organic phase was concentrated and recrystallized with ethyl acetate. After filtration, it was dried under vacuum to obtain gray flaky crystals (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one. Hydrogen spectrum analysis: 1 H NMR (400 MHz, Chloroform-d) δ7.89–7.80 (m, 4 H), 7.68–7.57 (m, 4 H), 6.77 (s, 1 H);

[0135] (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one (0.5 g, 1.13 mmol), 3,6-diphenylcarbazole (0.97 g, 3.05 mmol), palladium acetate (0.014 g, 0.065 mmol), tri-tert-butylphosphine tetrafluoroborate (0.056 g, 0.19 mmol) and sodium tert-butoxide prepared in step S7.1 were added to a dry 50 ml Schlenk reaction tube. After vacuuming and nitrogen bubbling three times using a double-row tube, 20 ml of deoxygenated xylene was injected and reacted at 130 °C for 48 h. After cooling to room temperature, the mixture was extracted three times with dichloromethane and water, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. Theoretically, 1.12 g of solid product should be obtained. After purification by silica gel column, 1.01 g of yellow solid was obtained with a yield of 89.84%. The reaction formula is:

[0136] .

[0137] As the doping concentration of the blue light material DPHCZPDO increases (5%→30%), the luminous color of the sky blue OLED device remains stable in the blue light range. max The improvement is significant (1.90~12.59%).

[0138] Figure 3 In which, b is the photoluminescence spectrum of the DPHCZPDO material before and after purging nitrogen in toluene solvent;

[0139] Figure 3 In which, e is the transient lifetime spectrum of the DPHCZPDO material before and after purging nitrogen in toluene solvent.

[0140] Example 3:

[0141] An OLED device with high exciton utilization rate, including a multi-layer structure stacked up and down, which are, from top to bottom in sequence, an ITO substrate, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a spacer layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode layer;

[0142] The material of the organic light-emitting layer is doped with a fluorescent material with high exciton utilization rate and double host materials mcp and TPBi.

[0143] The fluorescent material is a green light material based on the "hot exciton" 3-hydroxyacetophenone isomer.

[0144] The green light material is DPAPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(diphenylamino)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows:

[0145] .

[0146] The anode layer is an inorganic material, specifically indium tin oxide and indium zinc oxide;

[0147] The material of the hole injection layer is HAT-CN, and the thickness is 5 nm;

[0148] The material of the hole transport layer is TAPC, and the thickness is 30 nm;

[0149] The material of the electron blocking layer is TCTA, and the thickness is 5 nm;

[0150] The material of the spacer layer is mcp, and the thickness is 5 nm;

[0151] The organic light-emitting layer contains 13% fluorescent material, 87% double host materials mcp and TPBi by mass ratio, and the double host materials mcp and TPBi are in a mass ratio of 1:1, and the thickness is 50 nm;

[0152] The material of the hole blocking layer is TPBi, and the thickness is 10 nm;

[0153] The material of the electron transport layer is tmpypb, and the thickness is 40 nm;

[0154] The electron injection layer is made of LiF and has a thickness of 1 nm;

[0155] The cathode layer is any one of gold, silver, copper, aluminum and magnesium, and has a thickness of 150 nm.

[0156] The preparation method of the organic light-emitting layer using green light material is as follows:

[0157] S7.1. Take methyl p-bromobenzoate (6 g, 27.9 mmol) and p-bromoacetophenone (4.98 g, 25 mmol) and mix them in a 250 ml dry three-necked flask. Add sodium hydride (1.52 g, 63.3 mmol) into a dry constant pressure dropping funnel. Use rubber stoppers and sealing films to seal the joints of the device and the mouths of the three-necked flask and the dropping funnel. After vacuuming and bubbling nitrogen through a double-row tube three times, insert a nitrogen balloon and add tetrahydrofuran to dissolve. Cool the entire device to 0 °C, adjust the droplet falling speed to 1 drop / s, and heat to 60 °C after 30 min for 16 min. h. After the reaction, the reaction solution was neutralized with 10% dilute hydrochloric acid. The organic phase was separated, washed twice with brine and dried over anhydrous sodium sulfate. The organic phase was concentrated and recrystallized with ethyl acetate. After filtration, it was dried under vacuum to obtain gray flaky crystals (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one. Hydrogen spectrum analysis: 1 H NMR (400 MHz, Chloroform-d) δ7.89–7.80 (m, 4 H), 7.68–7.57 (m, 4 H), 6.77 (s, 1 H);

[0158] (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one (1 g, 2.62 mmol), diphenylamine (1.03 g, 6.11 mmol), palladium acetate (0.029 g, 0.13 mmol), tri-tert-butylphosphine tetrafluoroborate (0.8 g, 0.39 mmol) and sodium tert-butoxide (0.58 g, 6.11 mmol) prepared in step S7.1 were added to a dry 50 ml Schlenk reaction tube. After vacuuming and bubbling nitrogen three times using a double-row tube, 30 ml of deoxygenated xylene was injected. After reacting at 130 °C for 48 h and cooling to room temperature, the mixture was extracted three times with dichloromethane and water, dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. Theoretically, 1.46 g of solid product should be obtained. After purification by silica gel column, 0.43 g of yellow solid was obtained with a yield of 29.41%. The reaction formula is:

[0159] .

[0160] As the doping concentration of the green light material DPAPDO in the green OLED device increases (0.1% → 20%), the emission color of the device has been stable in the green light range, and the EQE max increases significantly (6.44% → 23.66%).

[0161] Figure 3 In which, c is the photoluminescence spectrum of the DPAPDO material before and after purging nitrogen in toluene solvent;

[0162] Figure 3 In which, f is the transient lifetime spectrum of the DPAPDO material before and after purging nitrogen in toluene solvent.

[0163] Please refer to Figure 4-21 .

[0164] By introducing the hot exciton mechanism on the basis of β-diketone, it shows the characteristics of hybrid-local charge transfer excited state, and high exciton utilization rate of ESIPT materials can be achieved through the rapid reverse intersystem crossing from the high-energy triplet state to the lowest singlet state energy level. These emitters show rapid ESIPT of keto emission from the hot exciton enol isomer and keto isomer.

[0165] The properties of the OLED devices prepared in Examples 1-3 were tested. The maximum brightness of the DCZPDO, DPHCZPDO and DPAPDO devices were 6015.43, 16472.05 and 11499.49 cd / m 2 respectively. The maximum current efficiency was 6.02, 31.13 and 72.04 cd / A, the maximum power efficiency was 6.08, 25.23 and 75.72 lm / W, and the maximum external quantum efficiency was 4.68%, 12.59% and 23.66%.

[0166] The fluorescence quantum efficiency of the devices was measured, and the measured fluorescence quantum efficiencies were 23.4%, 51.3%, and 41.6%, and through the formula η r = EQE max / (γ × η PL × η out ), the exciton utilization rates of the devices were calculated to be 58%, 94% and 228%.

[0167] As Figure 11 shown is the molecular energy level diagram of DCZPDO. The energy gaps between the alcohol structure T3 and S1, T2 and S1 are relatively small, which are 0.07 and 0.170 eV respectively; the energy gaps between the keto structure T3 and S2, T3 and S1 are relatively small, which are 0.064 and 0.122 eV respectively;

[0168] As Figure 12The molecular energy level diagram of DPHCZPDO is shown. The energy gaps between the enol structures T3 and S2, and T3 and S1 are relatively small, being 0.010 and 0.132 eV respectively; the energy gaps between the keto structures T3 and S2, and T1 and S1 are relatively small, being 0.178 and 0.228 eV respectively.

[0169] As Figure 13 The molecular energy level diagram of DPAPDO is shown. The energy gaps between the enol structures T3 and S2, and T3 and S1 are relatively small, being 0.210 and 0.117 eV respectively; the energy gaps between the keto structures T3 and S2, and T3 and S1 are relatively small, being 0.128 and 0.017 eV respectively.

[0170] Combined with the molecular energy level diagram, it is shown that the excitons within the molecules of the 3-hydroxypropenone isomer materials for the said blue light, sky blue light and green light can undergo reverse intersystem crossing transitions from the high-energy triplet state to the singlet state.

[0171] The said blue light, sky blue light and green light OLED devices all show stable electroluminescence spectra as the voltage increases from 4 V to around 10 V. The experimental results are as Figure 4 - Figure 13 shown.

[0172] As Figure 20 and Figure 20 shown in the illustrations in, the illustrations are respectively the natural transition orbits of the first excited state of the corresponding enol form. As the solvent polarity increases, the enol form emissions of the three materials show a good linear relationship, and the corresponding dipole moments (μe) are 18.65 d, 25.23 d and 15.02 d respectively, showing HLCT characteristics dominated by CT, which is consistent with the natural transition orbit of S0→S1.

[0173] Regarding the isomer emitters, the ESIPT TADF emitters used in the prior art have demonstrated green OLEDs with an EQE of 14%.

[0174] Moreover, high-performance green and yellow TADF ESIPT emitters based on 3-hydroxyacetone have achieved EQEs of 23.9% and 18.8% respectively.

[0175] Using the enol structure materials with hot exciton characteristics, deep blue OLEDs with an EQE of 7.1% have been fabricated, and WOLEDs and sky blue light OLEDs with EQEs of 6.3% and 8.0% respectively have been prepared.

[0176] Combined with the attached Figure 7-10 , it can be seen that the performance of the sky blue light and green light OLEDs of this patent is the highest among the hot exciton emitters.

[0177] The present invention designs and proposes a highly efficient organic fluorescent "hot exciton" 3-hydroxypropenone isomer material based on high-energy reverse intersystem crossing, and uses blue light, sky blue light, and green light materials of enol-keto tautomers with proton transfer and double host doping of mcp and TPBI as the light-emitting layer to prepare blue light, sky blue light, and green light OLED devices. The sky blue light OLED and the green light OLED devices described in the present invention both have high device efficiency and high exciton utilization rate, and the ratio is easy to regulate with high repeatability. The electroluminescence performance is stable under different voltages, and it has high application and popularization value.

[0178] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. An OLED device with high exciton utilization efficiency, characterized in that, It includes a multi-layer structure stacked up and down, which are, from top to bottom in sequence, an ITO substrate, an anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, a spacer layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode layer; The material of the organic light-emitting layer is a fluorescent material doped with high exciton utilization rate, and the double host materials mcp and TPBi; The fluorescent material is a blue light, sky blue light, and green light material based on the "hot exciton" 3-hydroxypropiophenone isomer; The blue light material is DCZPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(9H-carbazol-9-yl)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows: ； The sky blue light material is DPhCZPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows: ； The green light material is DPAPDO containing an electron acceptor and an ESIPT group, named (Z)-1,3-bis(4-(diphenylamino)phenyl)-3-hydroxyprop-2-en-1-one, and the molecular structural formula is as follows: 。 2. The OLED device with high exciton utilization rate according to claim 1, characterized in that, The anode layer is an inorganic material, specifically indium tin oxide and indium zinc oxide; The material of the hole injection layer is MoO3 or HAT-CN, and the thickness is 1-5 nm; The material of the hole transport layer is TAPC, and the thickness is 30-40 nm; The material of the electron blocking layer is TCTA, and the thickness is 5-30 nm; The material of the spacer layer is mcp, and the thickness is 5-10 nm; The organic light-emitting layer is composed of 0.1%-35% of the fluorescent material, 65%-99.9% of the double host materials mcp and TPBi by mass ratio. The double host materials mcp and TPBi are in a mass ratio of 1:3-1:1, and the thickness is 25-50 nm; The material of the hole blocking layer is TPBi, and the thickness is 5-10 nm; The material of the electron transport layer is tmpypb, and the thickness is 30-40 nm; The material of the electron injection layer is LiF, and the thickness is 1-3 nm; The cathode layer is any one of gold, silver, copper, aluminum, and magnesium, and the thickness is 100-150 nm.

3. A method for preparing an OLED device with high exciton utilization efficiency, characterized in that, The method for preparing the OLED device with high exciton utilization rate as described in any one of claims 1-2 includes the following steps: S1. Ultrasonically clean the ITO glass substrate with acetone, absolute ethanol, and ultrapure water, and then put the cleaned ITO glass substrate into a drying oven for drying; S2. Perform plasma pretreatment on the surface of the ITO glass substrate to remove the organic matter adhering to the surface of the ITO glass substrate; S3. Vacuum deposit a hole injection layer on the anode layer of the ITO glass substrate; S4. Vacuum deposit a hole transport layer on the hole injection layer; S5. Vacuum deposit an electron blocking layer on the hole transport layer; S6. Vacuum deposit a spacer layer on the electron blocking layer; S7. Vacuum deposit an organic light-emitting layer on the spacer layer; S8, vacuum evaporating a hole blocking layer on the organic light-emitting layer; S9, vacuum evaporating an electron transport layer on the hole blocking layer; S10, vacuum evaporating an electron injection layer on the electron transport layer; S11. Vacuum-evaporating a cathode layer on the electron injection layer to obtain an OLED device with high exciton utilization rate.

4. The preparation method of the OLED device with high exciton utilization rate according to claim 3, characterized in that, The preparation method of the organic light-emitting layer using blue light material is as follows: S7.

1. Take methyl p-bromobenzoate and p-bromoacetophenone and mix them into a dry three-necked flask. Add sodium hydride into a dry dropping funnel, seal it with a rubber stopper and a sealing film, evacuate and blow nitrogen through a double-row tube three times, insert a nitrogen balloon, and add tetrahydrofuran to dissolve, cool the entire device to 0 °C, adjust the droplet falling speed to a constant, and then heat to reflux temperature for reaction. After the reaction, neutralize the reaction solution with dilute hydrochloric acid, separate the organic phase, wash it twice with brine, and then dry it with anhydrous sodium sulfate. After concentrating the organic phase, recrystallize it with ethyl acetate, filter it, and vacuum dry it to obtain gray flaky crystals (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one; S7.

2. The gray flaky crystals obtained in S7.1, carbazole, palladium acetate, tri-tert-butylphosphine tetrafluoroborate and sodium tert-butoxide were added to a dry Schlenk reaction tube. After evacuation and nitrogen bubbling three times using a double-row tube, deoxygenated xylene was injected. After the reaction, the mixture was cooled to room temperature, extracted three times with dichloromethane and water, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. After purification by a silica gel column, a light yellow solid was obtained. The reaction formula is: 。 5. The method for preparing an OLED device with high exciton utilization rate according to claim 4, wherein The preparation method of the organic light-emitting layer using sky blue light material is as follows: The (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one, 3,6-diphenylcarbazole, palladium acetate, tri-tert-butylphosphine tetrafluoroborate and sodium tert-butoxide prepared in step S7.1 were added to a dry Schlenk reaction tube, and vacuumed and nitrogen-filled the tube three times using a double-row tube, and then deoxygenated xylene was injected. After the reaction, the mixture was cooled to room temperature, extracted three times with dichloromethane and water, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. After purification by silica gel column, a yellow solid was obtained, and the reaction formula is: 。 6. The preparation method of the OLED device with high exciton utilization rate according to claim 4, characterized in that, The preparation method of the organic light-emitting layer using green light material is as follows: The (Z)-1,3-bis(4-bromophenyl)-3-hydroxyprop-2-en-1-one prepared in step S7.1, diphenylamine, palladium acetate, tri-tert-butylphosphine tetrafluoroborate and sodium tert-butoxide were added to a dry Schlenk reaction tube, and vacuumed and nitrogen-filled the tube three times using a double-row tube, and then deoxygenated xylene was injected. After the reaction, the mixture was cooled to room temperature, extracted three times with dichloromethane and water, dried with anhydrous sodium sulfate, and the solvent was removed under reduced pressure. After purification by silica gel column, a yellow solid was obtained, and the reaction formula is: 。

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