Organic light-emitting diode based on soliton dye and preparation method thereof

Abstract

The invention belongs to the field of electronic devices, and discloses an organic light-emitting diode based on soliton dye and a preparation method of the organic light-emitting diode. An organic light-emitting diode based on soliton dye comprises a substrate, an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode. The light-emitting layer comprises a host material, a sensitizer and an object, the object is a soliton type dye object, and the mass of the soliton type dye object accounts for 0.01%-3% of the mass of the whole light-emitting layer. According to the invention, by reducing the doping concentration of the object, the luminescence quenching effect of the soliton type dye under high concentration caused by the strong self-absorption effect is effectively weakened, and meanwhile, the narrow emission half-peak width of the soliton type dye is ensured by the low doping concentration; the photoluminescence quantum efficiency (PLQY) of the soliton dye in a thin film state can reach up to 63.4%, and the full width at half peak of a luminescence spectrum is narrowed to 0.1 eV.

Description

Technical Field

[0001] The invention belongs to the field of electronic devices, and in particular relates to an organic light emitting diode based on a soliton-type dye and a preparation method thereof. Background Art

[0002] Compared with traditional liquid crystal displays, organic light-emitting diodes (OLEDs) have the advantages of fast response, self-luminescence, high contrast, and wide color gamut, and have received widespread attention in scientific research and business. Due to the inevitable ground-state-excited state vibration coupling and excited-state structural relaxation of organic light-emitting materials, the emission spectra of many organic fluorescent materials are usually relatively wide. This wide emission spectrum causes the color purity of OLED devices to deteriorate, making it difficult to meet the BT.2020 standard for ultra-high-definition display. The color purity problem of OLED devices can be solved to a certain extent by introducing filters or designing special optical resonant cavity structures, but this will lead to significant energy losses and increased difficulty in device processing. If a class of organic fluorescent materials with a narrow emission band can be developed, this problem will be fundamentally solved.

[0003] At present, the boron-nitrogen system materials based on multiple resonance can obtain a narrower fluorescence emission spectrum, but the device efficiency roll-off is significant and still cannot meet the standards for commercial applications. In addition, these materials have the disadvantages of low synthesis yield, limited material system types, and large conjugated fused rings required to achieve long-wavelength emission. Therefore, the production cost of boron-nitrogen system luminescent materials is relatively high. In addition, these materials are mainly prepared by vacuum evaporation, and there are challenges in preparing OLED displays on a large scale and at low cost by solution processing. Therefore, it is still an urgent commercial desire to develop new narrow-band emission systems, provide new design mechanisms, promote efficient synthesis routes, and develop low-cost processing technologies.

[0004] Many traditional soliton-type organic fluorescent dyes exhibit high luminescence quantum efficiency and very narrow fluorescence emission spectra in solution. These fluorescent dyes usually have high polarity and are soluble in highly polar solvents such as water and alcohol, which is very beneficial for designing orthogonal solution processing systems; in addition, many dye synthesis technologies are relatively mature and have low production costs, which provides the possibility for large-scale, low-cost solution processing of OLEDs in the future. However, due to the significant luminescence quenching of fluorescent dyes in the solid state, the application of traditional soliton-type dyes in OLEDs is quite limited. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the above-mentioned technologies, the primary purpose of the present invention is to provide an organic light-emitting diode based on soliton dyes, using soliton dyes as the guest material of the light-emitting layer (EML), introducing a sensitizer into the light-emitting layer and dispersing it in the host material to ensure the utilization rate of the excitons, and making full use of the high luminous efficiency and narrow emission half-width of the soliton dyes to obtain high electroluminescent efficiency and high color purity of the OLED device.

[0006] Another object of the present invention is to provide a method for suppressing luminescence quenching of soliton dyes in a thin film state, maintaining high luminescence efficiency and a narrow emission spectrum.

[0007] Another object of the present invention is to provide a method for preparing the organic light emitting diode based on soliton dyes.

[0008] In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is:

[0009] An organic light emitting diode based on soliton dye comprises a substrate, an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode.

[0010] The light-emitting layer comprises a host material, a sensitizer and a guest, and the guest is a soliton-type dye guest.

[0011] Preferably, the mass of the soliton dye guest accounts for 0.01% to 3% of the mass of the entire light-emitting layer, and more preferably 0.1%.

[0012] Preferably, the soliton guest has the structure shown in M1 to M10:

[0013]

[0014] Preferably, the host material in the light-emitting layer is one of 2,6-DCzPPy (2,6-bis((9H-carbazole-9-yl)-3,1-phenylene)pyridine), CBP (4,4'-bis(9-carbazole)biphenyl), and DPEPO (bis[2-((oxy)diphenylphosphino)phenyl]ether).

[0015] Preferably, the sensitizer is one of the following: a thermoexciton material PAC (2-(4-(10-(3-(9H-carbazole-9-yl)phenyl)anthracene-9-ylphenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole), a thermally activated delayed fluorescence material 2,6-DPEAD (2,6-bis(diphenylamino)anthraquinone), or a metal phosphorescent complex material Ir(piq)2(acac) (acetylacetonate di(1-phenylisoquinoline-C2,N)iridium(III)).

[0016] Preferably, the mass of the sensitizer accounts for 1% to 50% of the mass of the entire light-emitting layer, and more preferably 15%.

[0017] Preferably, the emission spectrum of the sensitizer in the light-emitting layer needs to have a large overlap with the absorption spectrum of the soliton dye.

[0018] Preferably, the substrate is one of quartz, glass, polymer or metal materials.

[0019] Preferably, the anode material is one of indium tin oxide and metal, and the thickness of the anode is 100-150 nm.

[0020] Preferably, the hole injection layer is PEDOT:PSS [poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)] or (PEDOT:PSS):PFI [poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid):perfluoroionomer], and has a thickness of 20 to 60 nm.

[0021] Preferably, the hole transport layer is PF8Cz [poly (9,9-n-dioctyl-2,7-fluorene-alt-9-isooctyl-3,6-carbazole)] with a thickness of 10 to 60 nm and PVK [poly (9-vinylcarbazole)] with a thickness of 5 to 60 nm.

[0022] Preferably, the electron transport layer is SPPO13 [2,7-bis(diphenylphosphinyl)-9,9'-spirobifluorene] or TPBi [1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene] or TmPyPb (1,3,5-tri[(3-pyridyl)-3-phenyl]benzene), with a thickness of 10 to 60 nm.

[0023] Preferably, the electron injection layer used is one of lithium fluoride (LiF), lithium carbonate (Li2CO3) or cesium carbonate (Cs2CO3), and has a thickness of 1 to 3 nm.

[0024] Preferably, the cathode material used is one of aluminum (Al), silver (Ag) or magnesium:aluminum (Mg:Al), and the thickness is 50-150 nm.

[0025] The method for preparing the organic light-emitting diode based on soliton dye comprises the following steps:

[0026] First, the substrate with the anode is cleaned, dried and then plasma treated. Then, a hole injection layer, a hole transport layer, a light-emitting layer and an electron transport layer are sequentially coated on the plasma-treated substrate with the anode. An electron injection layer and a cathode are added by vacuum evaporation to obtain an organic light-emitting diode based on soliton dyes.

[0027] Preferably, the cleaning comprises ultrasonic cleaning with deionized water, ITO cleaning solution, or isopropyl alcohol;

[0028] The coating is to place the substrate with the anode on a coating machine and coat it in sequence;

[0029] The vacuum evaporation is to place the coating machine in a vacuum chamber and use a mechanical pump and a molecular pump to evacuate the coating machine to a pressure of 1×10 - 4 Below Pa.

[0030] More specifically, the substrate with the anode is first cleaned, including using deionized water, ITO cleaning solution, and isopropanol ultrasonic cleaning, each for 15 to 45 minutes. After cleaning, the substrate with the anode is dried using a vacuum blower drying oven and treated using a plasma plasma cleaning machine for 5 to 30 minutes. Then, the substrate with the anode is placed on a solution processing device such as a coating machine or a doctor blade, and a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer are sequentially coated (the electron transport layer can also be formed by vacuum evaporation equipment), and then an electron injection layer and a cathode are added by vacuum evaporation to obtain an organic light-emitting diode based on a soliton dye.

[0031] The present invention effectively weakens the luminescence quenching effect of soliton dyes at high concentrations caused by strong self-absorption by reducing the guest doping concentration (the guest mass ratio in the light-emitting layer does not exceed 3%). At the same time, the low doping concentration ensures the narrow emission half-width of the soliton dyes, thereby achieving high luminescence efficiency and narrow emission half-width of the soliton dyes in a thin film state.

[0032] Generally speaking, reducing the guest doping concentration will be detrimental to the energy transfer between the host and the guest or between the sensitizer and the guest. The present invention utilizes the high molar extinction coefficient of the soliton dye to ensure effective energy transfer between the sensitizer and the guest at low doping concentration. Resonance energy transfer, thus achieving efficient transfer and utilization of excitons.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] 1. Since soliton dyes exhibit high luminescence performance in solution, but have severe luminescence quenching and significant spectrum broadening in the solid state, it is difficult for the existing technology to fully utilize the advantages of high luminescence efficiency and narrow half-peak width of soliton dyes, making it difficult to apply such dyes to solid-state luminescence. The present invention achieves high luminescence efficiency and narrow half-peak width of soliton dyes in thin films, and achieves high exciton utilization in electroluminescence, thereby ensuring good performance of OLED devices. Based on the technology of the present invention, it is possible to achieve a photoluminescence quantum efficiency (PLQY) of up to 63.4% and a luminescence spectrum half-peak full width as narrow as 0.1eV in the thin film state of soliton dyes.

[0035] 2. Existing multi-resonance materials often need to increase the conjugated area or introduce large donor and acceptor groups to achieve such long-wavelength emission, so the molecular weight is usually greater than 700, which significantly increases the sublimation temperature of vacuum evaporation processing, bringing challenges to device preparation. Soliton dyes can achieve ultra-narrowband long-wavelength emission at a relatively low molecular weight, such as square acid cyanine dyes, which usually have a molecular weight of about 400 and can emit long-wavelength red light with a wavelength of 660nm and a half-peak width of less than 0.1nm.

[0036] 3. Soliton dyes usually have high polarity and good solubility in polar solvents such as water and alcohol. This provides a new material option for the low-cost, large-area preparation of high-performance narrow-band OLEDs through solution processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The soliton dye squaryl cyanine M10 was dissolved in a dilute dichloromethane solution (10 -5 mol / L) in UV-visible absorption and fluorescence emission spectra.

[0038] Figure 2 Figure 5 is the fluorescence emission spectrum of the soliton dye cyanine M10 in a low doping concentration film (host PMMA: 0.1wt%).

[0039] Figure 3 Schematic diagram of the device structure of the OLED device prepared in Example 1 and Example 2.

[0040] Figure 4 This is the electroluminescence spectrum of the OLED device prepared in Example 1.

[0041] Figure 5 The EQE-brightness (EQE-L) curve of the OLED device prepared in Example 1.

[0042] Figure 6 This is the electroluminescence spectrum of the OLED device prepared in Example 2.

[0043] Figure 7 This is an electroluminescence spectrum of the OLED device prepared in comparative example. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with specific embodiments, but the embodiments of the present invention are not limited thereto. For process parameters not particularly noted, conventional techniques may be used.

[0045] The soliton dyes used in the examples can all be purchased through commercial channels.

[0046] Example 1 Preparation of OLED Device Based on Soliton Dye

[0047] The indium tin oxide (ITO) conductive glass was ultrasonically cleaned with acetone, isopropanol, deionized water, ITO cleaning solution, acetone, deionized water, and isopropanol for 30 minutes each, and then dried and treated with plasma for 15 minutes. ITO was used as an anode and a film was formed by spin coating using a homogenizer. A 60nm thick poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid):perfluoroionomer=1:5[(PEDOT:PSS):PFI=1:5] was spin coated on the surface of ITO as a hole injection layer, and a 60nm thick 2,6-bis((9H-carbazole-9-yl)-3,1-phenylene)pyridine:2,6-bis(diphenylamino)anthraquinone:solitary dye (mass ratio of 2,6-DCzPPy:2,6-DPEAD:M10=84.9%:15%:0.1%) was used as a light-emitting layer (the three raw materials were mixed in the above proportions and spin coated on a homogenizer to form a film). Then put it into the coating machine and use mechanical pump and molecular pump to evacuate the coating machine to a pressure of 1×10 -4 Pa below, the electron injection layer and cathode are added by vacuum evaporation, 60nm thick 2,7-bis(diphenylphosphinyl)-9,9'-spirobifluorene is used as the electron transport layer, 1nm thick lithium fluoride (LiF) is used as the electron injection layer, and 100nm thick aluminum (Al) is used as the electron cathode. The device structure is: ITO / PEDOT-PSS:PFI(1:5)(60nm) / EML(60nm) / SPPO13(60nm) / LiF(1nm) / Al(100nm).

[0048] The data of the organic electroluminescent device prepared in the above manner are shown in Table 1.

[0049] Table 1 Organic electroluminescent properties of the doped device (device A) based on compound M10 in Example 1

[0050]

[0051] Example 2

[0052] The difference from Example 1 is that the light-emitting layer contains 2,6-bis((9H-carbazole-9-yl)-3,1-phenylene)pyridine: 2,6-bis(diphenylamino)anthraquinone: soliton dye (mass ratio is 2,6-DCzPPy: 2,6-DPEAD: M10 = 67%: 30%: 3%), and the other conditions are the same as those in Example 1. The device performance is shown in Table 2. The electroluminescent performance is shown in Table 2. Figure 6 shown.

[0053] Table 2 Organic electroluminescent properties of the doped device (device B) based on compound M10 in Example 2

[0054]

[0055] Example 3

[0056] Different from Example 1 and Example 2, the soliton dye in the light-emitting layer is M2. The light-emitting layer contains 2,6-bis((9H-carbazole-9-yl)-3,1-phenylene)pyridine: 2,6-bis(diphenylamino)anthraquinone: soliton dye (mass ratio is 2,6-DCzPPy: 2,6-DPEAD: M2 = 74%: 25%: 1%). The device performance is shown in Table 3.

[0057] Table 3 Organic electroluminescent properties of the doped device (device C) based on compound M2 in Example 3

[0058]

[0059] Comparative Example

[0060] Different from Examples 1-3, the soliton dye in the light-emitting layer is selected as M2. The light-emitting layer comprises 2,6-bis((9H-carbazole-9-yl)-3,1-phenylene)pyridine: 2,6-bis(diphenylamino)anthraquinone: soliton dye (mass ratio is 2,6-DCzPPy: 2,6-DPEAD: M10 = 90%: 10%: 0.005%). Since the doping concentration of the soliton dye is too low, lower than the preferred doping concentration of 0.01%, incomplete energy transfer between the sensitizer and the guest is caused, thereby causing emission of the sensitizer. Therefore, the emission peak of the soliton dye is weak, and the efficient electroluminescence of the soliton dye cannot be achieved. Specifically, Figure 7 The device in the comparative example is named device D, and the electroluminescence spectrum of device D is shown in Figure 7 shown.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An organic light-emitting diode based on soliton dye, characterized in that: It includes a substrate, an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode; The light-emitting layer comprises a host material, a sensitizer and a guest, and the guest is a soliton-type dye guest.

2. The soliton dye organic light emitting diode according to claim 1, characterized in that: The mass of the soliton dye guest accounts for 0.01% to 3% of the mass of the entire light-emitting layer.

3. The soliton dye organic light emitting diode according to claim 1, characterized in that: The soliton dye guest has the structure shown in M1 to M10:

4. The soliton dye organic light emitting diode according to claim 1, characterized in that: The main material in the light-emitting layer is one of 2,6-bis((9H-carbazole-9-yl)-3,1-phenylene)pyridine, 4,4'-bis(9-carbazole)biphenyl and bis[2-((oxy)diphenylphosphino)phenyl]ether.

5. The organic light emitting diode of soliton dye according to any one of claims 1 to 4, characterized in that: The sensitizer is one of a thermal exciton material, a thermally activated delayed fluorescent material, and a metal phosphorescent complex material.

6. The soliton dye organic light emitting diode according to claim 5, characterized in that: The thermoexciton material is 2-(4-(10-(3-(9H-carbazole-9-yl)phenyl)anthracen-9-ylphenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole; The thermally activated delayed fluorescent material is 2,6-bis(diphenylamino)anthraquinone; The metal phosphorescent complex material is bis(1-phenylisoquinoline-C2, N)iridium(III) acetylacetonate.

7. The soliton dye organic light emitting diode according to claim 1, characterized in that: The mass of the sensitizer accounts for 1% to 50% of the mass of the entire light-emitting layer.

8. The soliton dye organic light emitting diode according to claim 1, characterized in that: The substrate is one of quartz, glass, polymer or metal materials; The anode material is one of indium tin oxide or metal material, with a thickness of 100 to 150 nm; The hole injection layer is PEDOT:PSS or (PEDOT:PSS):PFI, with a thickness of 20 to 60 nm; The hole transport layer is PF8Cz with a thickness of 10 to 60 nm and / or PVK with a thickness of 5 to 60 nm; The electron transport layer is SPPO13 or TPBi or TmPyPb, and has a thickness of 10 to 60 nm; The electron injection layer is one of lithium fluoride, lithium carbonate or cesium carbonate, and has a thickness of 1 to 3 nm; The cathode material is one of aluminum, silver or magnesium: aluminum, and the thickness is 50-150nm.

9. The method for preparing an organic light-emitting diode based on a soliton dye according to any one of claims 1 to 8, characterized in that: The following steps are involved: First, the substrate with the anode is cleaned, dried and then plasma treated. Then, a hole injection layer, a hole transport layer, a light-emitting layer and an electron transport layer are sequentially coated on the plasma-treated substrate with the anode. An electron injection layer and a cathode are added by vacuum evaporation to obtain an organic light-emitting diode based on soliton dyes.

10. The preparation method according to claim 9, characterized in that: The cleaning includes deionized water, ITO cleaning solution, and isopropyl alcohol ultrasonic cleaning; The coating is to place the substrate with the anode on a coating machine and coat it in sequence; The vacuum evaporation is to place the coating machine in a vacuum chamber and use a mechanical pump and a molecular pump to evacuate the coating machine to a pressure of 1×10 -4 Below Pa.

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