Luminescent layer with multi-layer structure, white organic light-emitting device containing luminescent layer and electronic device
Through the multi-layer structure of the luminescent layer design, specific material combinations and exciton transfer strategies are adopted to solve the problems of low efficiency, large roll-off and unstable color of white organic electroluminescent devices, and an efficient and stable white light luminescence effect is achieved.
Patent Information
- Application Number
- CN202510456107.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-11
- Publication Date
- 2025-07-11
AI Technical Summary
Existing white organic electroluminescent devices have problems such as low external quantum efficiency, serious roll-off and poor color stability, and it is difficult to achieve high efficiency, high color rendering index and low efficiency roll-off at the same time.
The luminescent layer design adopts a multi-layer structure, including green, red, blue light luminescent layer and sensitization layer. Using a combination of specific host materials and guest materials, the exciton utilization rate is improved through a cascaded waterfall exciton transfer strategy and optimize device performance.
It has achieved high color rendering index, low efficiency roll-off and high efficiency white organic electroluminescent devices to meet the needs of commercial applications, with a color rendering index of 85, a small color coordinate offset, and a stable device performance.
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Figure CN120302819A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of organic electroluminescent devices, and relates to a light-emitting layer with a multi-layer structure, a white organic electroluminescent device containing the same, and an electronic device. Background Art
[0002] White organic electroluminescent devices (WOLEDs) are the core of next-generation display and lighting devices, and extensive research has been carried out in aspects such as the development of functional materials, the regulation and distribution of excitons, structural optimization, and the development of preparation technologies. It has the characteristics of self-luminescence, low power consumption, flexibility and transparency, etc., and has a wide range of applications in the fields of solid-state lighting and full-color display. At present, it is still a major challenge to prepare OLEDs with a simple structure and excellent performance. Traditional fluorescent materials can only utilize singlet excitons to emit light, and the limit of the internal quantum efficiency (IQE) is only 25%. The second-generation phosphorescent materials achieve 100% IQE by introducing the heavy-atom effect, but due to the lack of stable blue phosphorescent materials, the development of white organic light-emitting diodes (WOLEDs) has been greatly restricted. Since the Adachi group first reported thermally activated delayed fluorescence (TADF) materials, they have received extensive attention.
[0003] WOLEDs devices usually contain multiple light-emitting layers, so that the emitted light can cover a relatively wide spectral range and achieve a high color rendering index. According to the materials used in the light-emitting layer, white-light devices can be divided into three categories, namely all-fluorescent WOLEDs, all-phosphorescent WOLEDs, and hybrid (fluorescent / phosphorescent mixed) WOLEDs. All-fluorescent devices that emit light by capturing singlet excitons have high stability, but are restricted by the quantum efficiency of fluorescent materials and have low efficiency. Due to the difference in charge transport ability between different hosts in the light-emitting layer, it usually leads to problems such as unbalanced charge injection / transport in the light-emitting layer and a narrow exciton recombination region, thereby triggering a series of exciton-polaron and exciton-exciton quenching effects, increasing the efficiency roll-off of the device and reducing the device lifetime. At the same time, the exciton recombination region of multi-layer WOLEDs will drift with the increase of the driving voltage, reducing the color stability of the device.
[0004] Therefore, white organic light-emitting diodes (OLEDs) cannot simultaneously achieve high efficiency, high color stability, and low efficiency roll-off, which limits their commercial applications. The main defects of white organic light-emitting diodes in the prior art are as follows:
[0005] Limited external quantum efficiency: Since the light emitted from the internal light-emitting region of the OLED is refracted and totally reflected at the interfaces of organic materials and glass when exiting externally, most of the light is confined inside the device and cannot be effectively emitted, and the external quantum efficiency is generally low, usually only about 20%-30%.
[0006] Efficiency roll-off problem: At high current densities, white OLEDs exhibit efficiency roll-off. This is because non-radiative recombination processes such as triplet-triplet annihilation and Auger recombination occur at high current densities, as well as factors such as the disruption of charge balance, which cause the luminous efficiency to decrease significantly as the current density increases, and are not conducive to its application in scenarios such as high-brightness displays.
[0007] Poor color stability: For different luminescent materials of different colors under different working conditions, such as different current densities, temperatures, etc., the degrees of change in their luminous intensity and spectral characteristics may be different, which will cause the color coordinates of the white light to drift, affecting the stability of the display effect.
[0008] The existing red-light guest materials have a low doping concentration, and the accuracy is not easy to control. At the same time, the extremely low doping concentration also makes the excitons in the red-light guest easily enter the saturated state when the applied voltage of the whole device increases. The excess excitons can only radiatively transition in other guests, ultimately resulting in a change in the light color of the device as the brightness increases; if the hosts of each light-emitting layer are different, the transfer of electrons and holes in the light-emitting layer needs to overcome the energy level barriers generated by the energy level differences between multiple hosts, which will lead to an increase in the driving voltage of the device. Moreover, the differences in the host materials make the carrier migration rates of each light-emitting layer different. Therefore, it is very difficult to adjust the carrier balance during the device preparation, resulting in the drift of the exciton recombination region as the voltage increases, causing spectral instability.
[0009] Therefore, in this field, how to fabricate hybrid white OLEDs with high color rendering index and low efficiency roll-off is the focus of research. Summary of the Invention
[0010] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a light-emitting layer with a multi-layer structure, a white organic electroluminescent device containing the same, and an electronic device.
[0011] To achieve the purpose of this invention, the present invention adopts the following technical solutions:
[0012] On the one hand, the present invention provides a light-emitting layer with a multilayer structure, which includes a green light-emitting layer, a red light-emitting layer, a sensitizing layer, and a blue light-emitting layer stacked in sequence. The green light-emitting layer includes a host material mCBP and a doped green light-emitting guest material TTPA (tris[4-(2-thienyl)phenyl]amine). The red light-emitting layer includes a host material and a doped red fluorescent guest material DBP (dibenzo-4,4,7,7-tetraphenyldiindeno[1,2,3-cd:1,2,3-lm]perylene). The sensitizing layer includes a host material and a doped green phosphorescent guest material Ir(ppy)2(acac) (bis(2-phenylpyridine)iridium(III) acetylacetonate) or (MAC*)Cu(Cz). The blue light-emitting layer includes a host material and a doped blue TADF material DMAC-DPS (bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone).
[0013] In the present invention, a multilayer light-emitting structure is constructed and used in a white organic light-emitting device, which can enable the device to have a high color rendering index, low efficiency roll-off, and high efficiency, improving the comprehensive performance of the white organic light-emitting device and meeting the requirements of commercial applications.
[0014] Preferably, the doping amount of the green light-emitting guest material TTPA in the green light-emitting layer is 1-3 wt%, such as 1 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.5 wt%, 2.8 wt%, or 3 wt%.
[0015] Preferably, the doping amount of the red fluorescent guest material DBP in the red light-emitting layer is 0.5-1 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%.
[0016] Preferably, the doping amount of the green phosphorescent guest material Ir(ppy)2(acac) in the sensitizing layer is 10-20 wt%, such as 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%.
[0017] Preferably, the doping amount of the blue TADF material DMAC-DPS in the blue light-emitting layer is 10-20 wt%, such as 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%.
[0018] Preferably, the host materials in the green light-emitting layer, the host materials in the red light-emitting layer, the host materials in the sensitizing layer, and the host materials in the blue light-emitting layer are independently selected from mCBP (3,3'-bis(9H-carbazol-9-yl)-1,1'-bicarbazole, 9-[3-(3-carbazol-9-ylphenyl)phenyl]carbazole), DPEPO (bis[2-((oxo)diphenylphosphino)phenyl]ether), or a dual-host material composed of mCBP and SiTrzCz2. In the present invention, selecting a dual-host material can balance carriers and broaden the exciton recombination region.
[0019] Preferably, the thickness of the green light-emitting layer is 2 - 4 nm, such as 2 nm, 2.5 nm, 3 nm, 3.5 nm, or 4 nm.
[0020] Preferably, the thickness of the red light-emitting layer is 4 - 6 nm, such as 4 nm, 4.5 nm, 4.8 nm, 5 nm, 5.5 nm, 5.8 nm, or 6 nm.
[0021] Preferably, the thickness of the sensitizing layer is 1 - 3 nm, such as 1 nm, 1.5 nm, 1.8 nm, 2 nm, 2.5 nm, 2.8 nm, or 3 nm.
[0022] Preferably, the thickness of the blue light-emitting layer is 6 - 12 nm, such as 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 9 nm, 10 nm, 11 nm, or 12 nm.
[0023] Preferably, the total thickness of the light-emitting layers of the multi-layer structure is 15 - 30 nm, such as 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, or 30 nm, and preferably 20 - 25 nm.
[0024] In the present invention, TTPA is selected as the guest material for the green light-emitting layer, DBP is selected as the guest material for the red light-emitting layer, Ir(ppy)2(acac) is selected as the guest material for the sensitizing layer, and the TADF material DMAC-DPS is selected as the guest material for the blue light-emitting layer. Since DBP has a relatively low exciton energy, the red light-emitting layer is inserted between the green phosphorescent Ir(ppy)2(acac) and the blue DMAC-DPS light-emitting layers to improve exciton utilization rate. And in order to inhibit the direct carrier capture and recombination effect of the fluorescent molecule DBP, the doping concentration of DBP is reduced to 0.5 - 1 wt%. A green phosphorescent light-emitting layer is additionally inserted between the blue and red light-emitting layers. Ir(ppy)2(acac) can effectively sensitize the fluorescent molecule DBP, so that after Ir(ppy)2(acac) captures excitons, it can effectively transfer the energy to DBP.
[0025] During the electroluminescence process, the blue TADF material DMAC-DPS undergoes singlet exciton radiative emission. Since it can efficiently up-convert triplet excitons to singlet excitons through RISC for radiative emission, it ensures sufficient blue light emission. Some of the triplet excitons that are not captured by the blue TADF material undergo phosphorescent radiative emission by transferring to the green triplet energy level through DET because the Ir(ppy)2(acac) green phosphorescent material has a relatively low triplet energy (2.38 eV). This energy transfer method improves the exciton radiative emission efficiency in the light-emitting layer and improves the efficiency roll-off characteristics.
[0026] The present invention constructs a "cascading waterfall" exciton transfer strategy in the multi-layer light-emitting layer to improve the exciton utilization rate, so as to optimize the performance of the white light device.
[0027] On the other hand, the present invention provides a white organic electroluminescent device, which includes a substrate, a cathode, and an organic functional layer. The organic functional layer includes a light-emitting layer, and the light-emitting layer is the light-emitting layer with the multi-layer structure as described above.
[0028] Preferably, the substrate is an ITO glass substrate.
[0029] Preferably, the organic functional layer further includes at least one of a hole injection layer, a hole transport layer, an optional electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer.
[0030] Preferably, the white organic electroluminescent device includes an anode, a hole injection layer, a hole transport layer, an optional electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode stacked in sequence, and the light-emitting layer is the light-emitting layer with the multi-layer structure as described above.
[0031] Preferably, the material of the hole injection layer is HAT-CN (1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile).
[0032] Preferably, the material of the hole transport layer is TAPC (4-[1-[4-[bis(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)aniline) or NPB (N,N′-bis(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine).
[0033] Preferably, the material of the electron blocking layer is TCTA (tris(4-carbazol-9-ylphenyl)amine).
[0034] Preferably, the material of the hole blocking layer is PPF (2,8-bis(diphenylphosphoryl)dibenz[b,d]furan).
[0035] Preferably, the material of the electron transport layer is TPBi (2,2',2”-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzoimidazole)), DPPyA (9,10-bis(6-phenylpyridin-3-yl)anthracene) or Bphen (4,7-diphenyl-1,10-phenanthroline).
[0036] Preferably, the material of the electron injection layer is Liq (lithium 8-hydroxyquinoline).
[0037] Preferably, the thickness of the hole injection layer is 3 - 10 nm, such as 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm, preferably 5 - 10 nm.
[0038] Preferably, the thickness of the hole transport layer is 40 - 60 nm, such as 40 nm, 43 nm, 45 nm, 48 nm, 50 nm, 53 nm, 55 nm, 58 nm or 60 nm, preferably 45 - 50 nm.
[0039] Preferably, the thickness of the electron blocking layer is 0 - 20 nm, such as 0 nm (in the present invention, 0 nm means the case without an electron blocking layer), 0.5 nm, 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 13 nm, 15 nm, 18 nm or 20 nm, preferably 8 - 15 nm.
[0040] Preferably, the thickness of the electron transport layer is 40 - 60 nm, such as 40 nm, 43 nm, 45 nm, 48 nm, 50 nm, 53 nm, 55 nm, 58 nm or 60 nm, preferably 50 - 55 nm.
[0041] Preferably, the thickness of the electron injection layer is 1 - 5 nm, such as 1 nm, 2 nm, 3 nm, 4 nm or 5 nm, preferably 2 - 3 nm.
[0042] Preferably, the thickness of the cathode is 80 - 200 nm, such as 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm or 200 nm, preferably 100 - 150 nm.
[0043] On the other hand, the present invention provides an electronic device, and the electronic device includes the white organic electroluminescent device as described above.
[0044] Compared with the prior art, the present invention has the following beneficial effects:
[0045] The light-emitting layer with a multi-layer structure of the present invention can enable the white organic electroluminescent device to have a high color rendering index, low efficiency roll-off and high efficiency, improving the comprehensive performance of the white organic electroluminescent device and meeting the requirements of commercial applications. Description of the Drawings
[0046] Figure 1 Schematic diagram of the structure of the white organic light-emitting device prepared in Example 1;
[0047] Figure 2 Graph of current density-voltage test results of the white organic light-emitting device prepared in Example 1;
[0048] Figure 3 Graph of luminance-voltage test results of the white organic light-emitting device prepared in Example 1;
[0049] Figure 4 Graph of external quantum efficiency-current density test results of the white organic light-emitting device prepared in Example 1;
[0050] Figure 5 Graph of current efficiency-current density test results of the white organic light-emitting device prepared in Example 1;
[0051] Figure 6 Graph of power efficiency-current density test results of the white organic light-emitting device prepared in Example 1;
[0052] Figure 7 Normalized electroluminescence spectrum diagram of the white organic light-emitting device prepared in Example 1;
[0053] Figure 8 CIE diagram of the white organic light-emitting device prepared in Example 1. Detailed Description of the Invention
[0054] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.
[0055] The test instruments and test conditions used in the embodiments are as follows: The current density-voltage-luminance characteristic curve diagram and the electroluminescence spectrum diagram are measured by a test system built with a Keithley 2400 source meter, an optical fiber, and a calibrated spectrometer (CS-2000 spectrometer). The current efficiency-current density-power efficiency characteristic curve diagram and the external quantum efficiency-luminance characteristic curve diagram are measured in a calibrated integrating sphere (Ocean Insight SPECTRUMTEQ-EQY).
[0056] For the raw materials used in the examples, if there are no special limitations, they are all disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art. HAT-CN, TAPC, TCTA, mCBP, Ir(ppy)2(acac), DBP, TTPA, DMAC-DPS, and Liq were all purchased from Xi'an Baolaitai Optoelectronic Technology Co., Ltd.
[0057] Example 1
[0058] This example provides a white organic light-emitting device, and its preparation method is as follows:
[0059] Step 1: Put the ITO substrate glass into acetone, isopropyl alcohol, alcohol, and deionized water in sequence and ultrasonically clean for 5 minutes each. After drying with a nitrogen gun, treat the surface of the ITO glass with ultraviolet ozone for 15 minutes.
[0060] Step 2: Put the substrate prepared in Step 1 into a vacuum evaporation machine. When the pressure of the coating machine drops to 4*10 -6When the pressure is below mbar, the evaporation of the remaining functional layers starts in sequence. First, the hole injection layer part is prepared. HAT-CN is evaporated on the substrate with a thickness of 10 nm and an evaporation rate of 0.3 Å per second; then the hole transport layer material TAPC is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second; the electron blocking layer TCTA is evaporated with a thickness of 10 nm and an evaporation rate of 0.8 Å per second; the OLED green light-emitting layer, the host material mCBP and the doped green light-emitting guest material TTPA (1 wt%) have a thickness of 1 nm, where the evaporation rate of mCBP is 0.99 Å per second and the evaporation rate of TTPA is 0.01 Å per second. Then, the red light-emitting layer is evaporated. The host material mCBP and the doped red fluorescent guest material DBP (1 wt%) have a thickness of 4 nm, where the evaporation rate of mCBP is 0.99 Å per second and the evaporation rate of DBP is 0.01 Å per second. Then, the intermediate sensitization layer is evaporated. The host material mCBP and the doped green phosphorescent guest material Ir(ppy)2(acac) (10 wt%) have a thickness of 1 nm, where the evaporation rate of mCBP is 0.80 Å per second and the evaporation rate of Ir(ppy)2(acac) is 0.20 Å per second. Finally, the blue light-emitting layer is evaporated. The host material mCBP and the doped blue TADF material DMAC-DPS (20 wt%) have a thickness of 12 nm, where the evaporation rate of mCBP is 0.80 Å per second and the evaporation rate of DMAC-DPS is 0.20 Å per second. The hole blocking layer material PPF is evaporated with a thickness of 10 nm and an evaporation rate of 0.3 Å per second; the electron transport layer material DPPyA is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second; the electron injection layer material Liq is evaporated with a thickness of 2 nm and an evaporation rate of 0.3 Å per second; finally, the metal aluminum cathode is evaporated with a thickness of 100 nm and an evaporation rate of 3 Å per second. During the device preparation process, a quartz crystal oscillator film thickness monitor is used to control the evaporation thickness and evaporation rate of each functional layer. After the device preparation is completed, the device is transferred from the evaporator to the glove box.
[0061] Step 3: Under the nitrogen environment in the glove box, the evaporated device is encapsulated using epoxy resin glue and a glass cover. The finally obtained device structure is:
[0062] ITO / HAT-CN(10nm) / TAPC(40nm) / TCTA(10nm) / mCBP:TTPA(1%,1nm) / mCB P:DBP(1%,4nm) / mCBP:Ir(ppy)2(acac)(10%,1nm) / mCBP:DMAC-DPS(20%,12nm) / PPF(10nm) / DPPYA(40nm) / Liq(2nm) / Al(100nm).
[0063] Example 2
[0064] This embodiment provides a white organic light-emitting device, and its preparation method is as follows:
[0065] Step 1: The ITO substrate glass is sequentially placed in acetone, isopropyl alcohol, alcohol, and deionized water and ultrasonically cleaned for 5 minutes each. After being dried with a nitrogen gun, the surface of the ITO glass is treated with ultraviolet ozone for 15 minutes.
[0066] Step 2: The substrate prepared in Step 1 is placed in a vacuum evaporation machine. When the pressure of the evaporation machine drops below 4×10 -6 mbar, the remaining functional layers are sequentially evaporated. First, the hole injection layer part is prepared. HAT-CN is evaporated on the substrate with a thickness of 10 nm and an evaporation rate of 0.3 Å per second; then the hole transport layer material TAPC is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second; the electron blocking layer TCTA is evaporated with a thickness of 10 nm and an evaporation rate of 0.8 Å per second; the OLED green light-emitting layer, the host material mCBP and the doped green light-emitting guest material TTPA (1 wt%) have a thickness of 3 nm, where the evaporation rate of mCBP is 0.99 Å per second and the evaporation rate of TTPA is 0.01 Å per second. Then, the red light-emitting layer is evaporated. The host material mCBP and the doped red fluorescent guest material DBP (1 wt%) have a thickness of 4 nm, where the evaporation rate of mCBP is 0.99 Å per second and the evaporation rate of DBP is 0.01 Å per second. Then, the intermediate sensitizing layer is evaporated. The host material mCBP and the doped green phosphorescent guest material Ir(ppy)2(acac) (20 wt%) have a thickness of 1 nm, where the evaporation rate of mCBP is 0.80 Å per second and the evaporation rate of Ir(ppy)2(acac) is 0.20 Å per second. Finally, the blue light-emitting layer is evaporated. The host material mCBP and the doped blue TADF material DMAC-DPS (20 wt%) have a thickness of 12 nm, where the evaporation rate of mCBP is 0.80 Å per second and the evaporation rate of DMAC-DPS is 0.20 Å per second. The hole blocking layer material PPF is evaporated with a thickness of 10 nm and an evaporation rate of 0.3 Å per second; the electron transport layer material DPPyA is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second; the electron injection layer material Liq is evaporated with a thickness of 2 nm and an evaporation rate of 0.3 Å per second; and finally, the metal aluminum cathode is evaporated with a thickness of 100 nm and an evaporation rate of 3 Å per second. During the device preparation process, a quartz crystal oscillator film thickness monitor is used to control the evaporation thickness and evaporation rate of each functional layer. After the device is prepared, it is transferred from the evaporation machine to a glove box.
[0067] Step 3: In the nitrogen environment of the glove box, the evaporated device is encapsulated with epoxy resin glue and a glass cover. The final device structure obtained is:
[0068] ITO / HAT-CN(10 nm) / TAPC(40 nm) / TCTA(10 nm) / mCBP:TTPA(1%, 3 nm) / mCBP:DBP(1%, 4 nm) / mCBP:Ir(ppy)2(acac)(20%, 1 nm) / mCBP:DMAC-DPS(20%, 12 nm) / PPF(10 nm) / DPPYA(40 nm) / Liq(2 nm) / Al(100 nm).
[0069] Example 3
[0070] This example provides a white organic light-emitting device, and its preparation method is as follows:
[0071] Step 1: Put the ITO substrate glass into acetone, isopropyl alcohol, alcohol, and deionized water in sequence, ultrasonically clean for 5 minutes respectively, and after drying with a nitrogen gun, treat the surface of the ITO glass with ultraviolet ozone for 15 minutes.
[0072] Step 2: Put the substrate prepared in Step 1 into a vacuum evaporation machine. When the pressure of the evaporation machine drops to 4*10 -6When the pressure is below millibar, the evaporation of the remaining functional layers starts in sequence. First, the hole injection layer part is prepared. HAT-CN is evaporated on the substrate with a thickness of 10 nanometers and an evaporation rate of 0.3 angstroms per second; then the hole transport layer material TAPC is evaporated with a thickness of 40 nanometers and an evaporation rate of 1 angstrom per second; the electron blocking layer TCTA is evaporated with a thickness of 10 nanometers and an evaporation rate of 0.8 angstroms per second; the OLED green light emitting layer, the host material mCBP and the doped green light guest material TTPA (1 wt%) have a thickness of 3 nanometers, where the evaporation rate of mCBP is 0.99 angstroms per second and the evaporation rate of TTPA is 0.01 angstroms per second. Then, the red light emitting layer is evaporated. The host material mCBP and the doped red light fluorescent guest material DBP (1 wt%) have a thickness of 4 nanometers, where the evaporation rate of mCBP is 0.99 angstroms per second and the evaporation rate of DBP is 0.01 angstroms per second. Then, the intermediate sensitizing layer is evaporated. The host material mCBP and the doped green phosphorescent guest material Ir(ppy)2(acac) (20 wt%) have a thickness of 1 nanometer, where the evaporation rate of mCBP is 0.80 angstroms per second and the evaporation rate of Ir(ppy)2(acac) is 0.20 angstroms per second. Finally, the blue light emitting layer is evaporated. The host material mCBP and the doped blue TADF material DMAC-DPS (20 wt%) have a thickness of 6 nanometers, where the evaporation rate of mCBP is 0.80 angstroms per second and the evaporation rate of DMAC-DPS is 0.20 angstroms per second. The hole blocking layer material PPF is evaporated with a thickness of 10 nanometers and an evaporation rate of 0.3 angstroms per second; the electron transport layer material DPPyA is evaporated with a thickness of 40 nanometers and an evaporation rate of 1 angstrom per second; the electron injection layer material Liq is evaporated with a thickness of 2 nanometers and an evaporation rate of 0.3 angstroms per second; finally, the metal aluminum cathode is evaporated with a thickness of 100 nanometers and an evaporation rate of 3 angstroms per second. During the device preparation process, a quartz crystal oscillator film thickness monitor is used to control the evaporation thickness and evaporation rate of each functional layer. After the device preparation is completed, the device is transferred from the evaporator to the glove box.
[0073] Step 3: Under the nitrogen environment in the glove box, the evaporated device is encapsulated using epoxy resin glue and a glass cover. The finally obtained device structure is:
[0074] ITO / HAT-CN(10nm) / TAPC(40nm) / TCTA(10nm) / mCBP:TTPA(1%,3nm) / mCB P:DBP(1%,4nm) / mCBP:Ir(ppy)2(acac)(20%,1nm) / mCBP:DMAC-DPS(20%,6nm) / P PF(10nm) / DPPYA(40nm) / Liq(2nm) / Al(100nm).
[0075] Example 4
[0076] This embodiment provides a white organic light-emitting device, and its preparation method is as follows:
[0077] Step 1: The ITO substrate glass is successively placed in acetone, isopropyl alcohol, alcohol, and deionized water and ultrasonically cleaned for 5 minutes each. After being dried with a nitrogen gun, the surface of the ITO glass is treated with ultraviolet ozone for 15 minutes.
[0078] Step 2: The substrate prepared in Step 1 is placed in a vacuum evaporation machine. When the pressure of the evaporation machine drops below 4 * 10 -6 mbar, the remaining functional layers are successively evaporated. First, the hole injection layer part is prepared. HAT-CN is evaporated on the substrate with a thickness of 10 nm and an evaporation rate of 0.3 Å per second; then the hole transport layer material TAPC is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second; the electron blocking layer TCTA is evaporated with a thickness of 10 nm and an evaporation rate of 0.8 Å per second; the OLED green light-emitting layer, the host material mCBP and the doped green light-emitting guest material TTPA (1 wt%) have a thickness of 3 nm, where the evaporation rate of mCBP is 0.99 Å per second and the evaporation rate of TTPA is 0.01 Å per second. Then, the red light-emitting layer is evaporated. The host material mCBP and the doped red fluorescent guest material DBP (1 wt%) have a thickness of 4 nm, where the evaporation rate of mCBP is 0.99 Å per second and the evaporation rate of DBP is 0.01 Å per second. Then, the intermediate sensitizing layer is evaporated. The host material mCBP and the doped green phosphorescent guest material Ir(ppy)2(acac) (10 wt%) have a thickness of 1 nm, where the evaporation rate of mCBP is 0.80 Å per second and the evaporation rate of Ir(ppy)2(acac) is 0.20 Å per second. Finally, the blue light-emitting layer is evaporated. The host material mCBP and the doped blue TADF material DMAC-DPS (20 wt%) have a thickness of 6 nm, where the evaporation rate of mCBP is 0.80 Å per second and the evaporation rate of DMAC-DPS is 0.20 Å per second. The hole blocking layer material PPF is evaporated with a thickness of 10 nm and an evaporation rate of 0.3 Å per second; the electron transport layer material DPPyA is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second; the electron injection layer material Liq is evaporated with a thickness of 2 nm and an evaporation rate of 0.3 Å per second; finally, the metal aluminum cathode is evaporated with a thickness of 100 nm and an evaporation rate of 3 Å per second. During the device preparation process, a quartz crystal oscillator film thickness monitor is used to control the evaporation thickness and evaporation rate of each functional layer. After the device is prepared, it is transferred from the evaporation machine to a glove box.
[0079] Step 3: In the nitrogen environment of the glove box, the evaporated device is encapsulated using epoxy resin glue and a glass cover. The final device structure obtained is:
[0080] ITO / HAT-CN (10 nm) / TAPC (40 nm) / TCTA (10 nm) / mCBP:TTPA (1%, 3 nm) / mCBP:DBP (1%, 4 nm) / mCBP:Ir(ppy)2(acac) (10%, 1 nm) / mCBP:DMAC-DPS (20%, 6 nm) / PPF (10 nm) / DPPYA (40 nm) / Liq (2 nm) / Al (100 nm).
[0081] Example 5
[0082] This example provides a white organic light-emitting device, and its preparation method is as follows:
[0083] Step 1: Put the ITO substrate glass into acetone, isopropyl alcohol, alcohol and deionized water in sequence and ultrasonically clean for 5 minutes each. After drying with a nitrogen gun, treat the surface of the ITO glass with ultraviolet ozone for 15 minutes.
[0084] Step 2: Put the substrate prepared in Step 1 into a vacuum evaporation machine. When the pressure of the evaporation machine drops to 4*10 -6When the pressure is below millibar, the evaporation of the remaining functional layers starts successively. First, the hole injection layer part is prepared. HAT-CN is evaporated on the substrate with a thickness of 10 nm and an evaporation rate of 0.3 Å per second. Then, the hole transport layer material TAPC is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second. The electron blocking layer TCTA is evaporated with a thickness of 10 nm and an evaporation rate of 0.8 Å per second. The OLED green light-emitting layer, with the host material mCBP and the doped green light-emitting guest material TTPA (1 wt%) with a thickness of 3 nm, is evaporated. Among them, the evaporation rate of mCBP is 0.99 Å per second, and the evaporation rate of TTPA is 0.01 Å per second. Then, the red light-emitting layer is evaporated. The host material mCBP and the doped red fluorescent guest material DBP (1 wt%) with a thickness of 4 nm are evaporated. Among them, the evaporation rate of mCBP is 0.99 Å per second, and the evaporation rate of DBP is 0.01 Å per second. Then, the intermediate sensitizing layer, with the host material mCBP and the doped green phosphorescent guest material Mac*(Cu)Cz (20 wt%) with a thickness of 1 nm, is evaporated. Among them, the evaporation rate of mCBP is 0.80 Å per second, and the evaporation rate of Mac*(Cu)Cz is 0.20 Å per second. Finally, the blue light-emitting layer, with the host material mCBP and the doped blue TADF material DMAC-DPS (20 wt%) with a thickness of 8 nm, is evaporated. Among them, the evaporation rate of mCBP is 0.80 Å per second, and the evaporation rate of DMAC-DPS is 0.20 Å per second. The hole blocking layer material PPF is evaporated with a thickness of 10 nm and an evaporation rate of 0.3 Å per second. The electron transport layer material DPPyA is evaporated with a thickness of 40 nm and an evaporation rate of 1 Å per second. The electron injection layer material Liq is evaporated with a thickness of 2 nm and an evaporation rate of 0.3 Å per second. Finally, the metal aluminum cathode is evaporated with a thickness of 100 nm and an evaporation rate of 3 Å per second. During the device preparation process, a quartz crystal oscillator film thickness monitor is used to control the evaporation thickness and evaporation rate of each functional layer. After the device preparation is completed, the device is transferred from the evaporator to the glove box.
[0085] Step 3: Under the nitrogen environment in the glove box, the evaporated device is encapsulated using epoxy resin glue and a glass cover. The finally obtained device structure is:
[0086] ITO / HAT-CN(10nm) / TAPC(40nm) / TCTA(10nm) / mCBP:TTPA(1%,3nm) / mCBP:DBP(1%,4nm) / mCBP:Mac*(Cu)Cz(20%,1nm) / mCBP:DMAC-DPS(20%,8nm) / PPF(10nm) / DPPYA(40nm) / Liq(2nm) / Al(100nm).
[0087] Comparative Example 1
[0088] Compared with Example 1, the difference is only that no intermediate sensitization layer is prepared in the light-emitting layer of the organic electroluminescent device.
[0089] Performance test:
[0090] Performance test of the device obtained in Example 1. The current-voltage characteristic curve, brightness-voltage characteristic curve, external quantum efficiency-current density characteristic curve, current efficiency-current density characteristic curve, power efficiency-current density characteristic curve, electroluminescence spectrum diagram and chromaticity coordinate diagram of the white light OLED device prepared in Example 1 are respectively as Figures 2 - 8 shown. Figure 2 It can be seen that the dark current is small, indicating that the substrate is cleaned cleanly; Figure 3 It can be seen that the turn-on voltage is 3.3 V; Figure 4 It can be seen that the maximum external quantum efficiency is 21.57%; Figure 5 It can be seen the characteristic curve of the current efficiency varying with the current density. It can be seen that the current efficiency of the device is 38.6 cd A -1 ; Figure 6 It can be seen the characteristic curve of the power efficiency varying with the current density. It can be seen that the power efficiency (PE) of the device is 37.9 lm·W-1; Figure 7 The electroluminescence spectrum can be seen, and the emission peaks of each material; Figure 8 It can be seen that the chromaticity coordinates deviate from the chromaticity coordinates. From Figure 8 it can be seen that the device emits white light.
[0091] High color rendering index: The color rendering index (CRI) reaches 85, which can better restore the true color of objects and meet the application requirements such as indoor lighting. However, the color rendering index of some existing devices is relatively low and cannot meet this requirement.
[0092] Good spectral stability: In the practical brightness range (1000 - 5000 cd·m-2), the chromaticity coordinate deviation is small. For example, the CIE deviation of W2 is only (0.005, 0.006), which is better than some existing devices, ensuring the stability of the emission color.
[0093] Low efficiency roll-off: The device can maintain good performance at different current densities, reducing the efficiency roll-off and improving the service life and stability of the device.
[0094] The maximum external quantum efficiency, maximum current efficiency and maximum power efficiency of the devices prepared in the examples and comparative examples are shown in Table 1.
[0095] Table 1
[0096]
[0097] As can be seen from Table 1, when the light-emitting layer with a multi-layer structure of the present invention is applied to a white organic electroluminescent device, the maximum external quantum efficiency of the device can be above 14.1%, the maximum current efficiency is as high as 29 cd A -1 or above, and the maximum power efficiency is above 20 lm W -1 or above.
[0098] The applicant declares that the present invention uses the above embodiments to illustrate the light-emitting layer with a multi-layer structure of the present invention, the white organic electroluminescent device containing the same, and the electronic device. However, the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.
Claims
1. A light-emitting layer of a multilayer structure, characterized in that, The light-emitting layer of the multi-layer structure includes a green light-emitting layer, a red light-emitting layer, a sensitizing layer, and a blue light-emitting layer stacked in sequence. The green light-emitting layer includes a host material and a doped green light-emitting guest material TTPA. The red light-emitting layer includes a host material and a doped red fluorescent guest material DBP. The sensitizing layer includes a host material and a doped green phosphorescent guest material Ir(ppy)2(acac) or (MAC*)Cu(Cz). The blue light-emitting layer includes a host material and a doped blue TADF material DMAC-DPS.
2. The light-emitting layer of the multilayer structure according to claim 1, characterized in that The doping amount of the green light-emitting guest material TTPA in the green light-emitting layer is 1-3 wt%; Preferably, the doping amount of the red fluorescent guest material DBP in the red light-emitting layer is 0.5-1 wt%; Preferably, the doping amount of the green phosphorescent guest material Ir(ppy)2(acac) in the sensitizing layer is 10-20 wt%; Preferably, the doping amount of the blue TADF material DMAC-DPS in the blue light-emitting layer is 10-20 wt%; Preferably, the host material in the green light-emitting layer, the host material in the red light-emitting layer, the host material in the sensitizing layer, and the host material in the blue light-emitting layer are independently selected from mCBP or DPEPO, or a dual-host material composed of mCBP and SiTrzCz2.
3. The light-emitting layer of the multilayer structure according to claim 1 or 2, characterized in that The thickness of the green light-emitting layer is 2-4 nm; Preferably, the thickness of the red light-emitting layer is 4-6 nm; Preferably, the thickness of the sensitizing layer is 1-3 nm, preferably 1 nm; Preferably, the thickness of the blue light-emitting layer is 6-12 nm.
4. The light-emitting layer of the multilayer structure according to any one of claims 1-3, characterized in that The total thickness of the light-emitting layer of the multi-layer structure is 15-30 nm, preferably 20-25 nm.
5. A white organic electroluminescent device, characterized in that, The white organic light-emitting device includes a substrate, a cathode, and an organic functional layer. The organic functional layer includes a light-emitting layer, and the light-emitting layer is the light-emitting layer of the multi-layer structure according to any one of claims 1-4.
6. The white organic electroluminescent device according to claim 5, wherein The substrate is an ITO glass substrate.
7. The white organic electroluminescent device according to claim 5, characterized in that, The organic functional layer further includes at least one of a hole injection layer, a hole transport layer, an optional electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer; Preferably, the white organic light-emitting device includes an anode, a hole injection layer, a hole transport layer, an optional electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode stacked in sequence. The light-emitting layer is the light-emitting layer of the multi-layer structure according to any one of claims 1-4.
8. The white organic electroluminescent device according to claim 7, wherein The material of the hole injection layer is HAT-CN; Preferably, the material of the hole transport layer is TAPC or NPB; Preferably, the material of the electron blocking layer is TCTA; Preferably, the material of the hole blocking layer is PPF; Preferably, the material of the electron transport layer is TPBi, DPPyA, or Bphen; Preferably, the material of the electron injection layer is Liq.
9. The white organic electroluminescent device according to claim 7, wherein, The thickness of the hole injection layer is 3-10 nm, preferably 5-10 nm; Preferably, the thickness of the hole transport layer is 40-60 nm, preferably 45-50 nm; Preferably, the thickness of the electron blocking layer is 0 - 20 nm, preferably 8 - 15 nm; Preferably, the thickness of the electron transport layer is 40 - 60 nm, preferably 50 - 55 nm; Preferably, the thickness of the electron injection layer is 1 - 5 nm, preferably 2 - 3 nm; Preferably, the thickness of the cathode is 80 - 200 nm, preferably 100 - 150 nm.
10. An electronic device, characterized in that, The electronic device includes the white organic electroluminescent device according to any one of claims 5 - 9.