CN114525058A - Organic light-emitting layer ink, preparation method and light-emitting layer forming method - Google Patents
Organic light-emitting layer ink, preparation method and light-emitting layer forming method Download PDFInfo
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- C09D11/00—Inks
- C09D11/30—Inkjet printing inks
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- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
- H10K50/12—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants
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- H10K71/13—Deposition of organic active material using liquid deposition, e.g. spin coating using printing techniques, e.g. ink-jet printing or screen printing
- H10K71/135—Deposition of organic active material using liquid deposition, e.g. spin coating using printing techniques, e.g. ink-jet printing or screen printing using ink-jet printing
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Abstract
The invention discloses organic light-emitting layer ink, a preparation method and a light-emitting layer forming method, belonging to the field of OLED (organic light-emitting diode), wherein the ink comprises the following components in percentage by mass: 3% -30% of organic main material, 0.1% -6% of organic doped luminescent material, 0% -10% of regulator and 54% -96.9% of solvent, wherein the organic main material comprises a hole type organic main material containing a crosslinking group and an electronic type organic main material containing a crosslinking group, the ink can be thermally crosslinked at 100-200 ℃, the temperature range has no adverse effect on other layers of the OLED, the luminescent layer has the characteristic of solvent resistance after crosslinking, the luminescent layer can be prevented from being mutually dissolved with other layers, so that an electron transport layer of the OLED can be prepared by solution processing, and the hole type organic main material and the electronic type organic main material which are jointly used as the organic main material can effectively reduce the efficiency roll-off of the luminescent layer.
Description
Technical Field
The invention relates to organic light-emitting layer ink, a preparation method and a light-emitting layer forming method, and belongs to the field of OLEDs.
Background
An Organic Light-Emitting Diode (OLED) is a high-quality display device, and OLED display has many advantages over conventional display methods such as cathode ray tube display, liquid crystal display, and the like, for example, low driving voltage, high display Light-Emitting efficiency, fast response speed, Light and thin, wider display viewing angle, higher contrast, higher display definition, and the like, so the OLED display method is gradually replacing the currently prevailing liquid crystal display method, and the OLED display has more and more applications in various aspects such as mobile phones, computers, televisions, and the like. The OLED display device generally includes an anode, a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), an emission layer (ETL), an Electron Transport Layer (ETL), and a cathode, and as a driving voltage gradually increases, holes and electrons form excitons (electron-hole pairs) in the emission layer, and the excitons in an excited state transfer energy to a light emitting material, so that electrons of the light emitting material transition from a ground state to an excited state, and photons are released to emit light in a process of returning the electrons from the excited state to the ground state. Because of the different excited state energy levels of different luminescent materials, different intensities of radiation energy are generated, and different wavelengths of light, such as red, green and blue, are emitted to form the basic colors of the display device.
The OLED ink-jet printing process has the advantages of high material utilization rate, low requirements on equipment and environment, capability of large-area processing and the like, and is an OLED production and preparation process which can effectively reduce the production cost and has great advantages in preparing large-size OLED panels. The ink-jet printing OLED process accurately drops electronic ink prepared from organic materials and solvents into a prefabricated pixel pit, can realize high resolution without a fine metal mask in a vacuum evaporation process, and is expected to become a mainstream process for producing next-generation OLED display screens.
The selection of organic materials in the electronic ink of the light-emitting layer is a difficult point of the current ink-jet printing OLED process, the used materials need to be dissolved, certain viscosity requirement and tension requirement are also met during solution preparation, after the requirements are met, the selection of the materials and solvents is not many, and the properties of the materials are close, so that a problem appears, when an OLED device is printed, a plurality of layers need to be printed, when the ink of the next layer is printed, the ink is easily dissolved with the printed ink of the previous layer, most of the materials of the organic light-emitting layer and the electronic transmission layer can be dissolved in the same solvent, so that when the electronic transmission layer is printed, the light-emitting layer is often damaged.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides an organic light-emitting layer ink which can be dissolved, can be prepared into a certain viscosity and tension requirement and can be prevented from being mutually dissolved with other layers, a preparation method of the organic light-emitting layer ink and a light-emitting layer forming method using the ink.
The technical scheme adopted by the invention for solving the technical problems is as follows:
in a first aspect, the present application provides an organic light emitting layer ink comprising the following components in mass fraction: 3% -30% of organic main material, 0.1% -6% of organic doped luminescent material, 0% -10% of regulator and 54% -96.9% of solvent, wherein the organic main material comprises a hole type organic main material containing a crosslinking group and an electronic type organic main material containing the crosslinking group, and the thermal crosslinking temperature range of the crosslinking group is 100-200 ℃.
The application provides an organic light emitting layer ink carries out heat crosslinking after printing and handles, has anti soluble characteristic after the crosslinking, avoids other layers with OLED intersolubility.
Further, the hole-type organic host material containing a crosslinking group is selected from one of the following H1 to H6:
the solubility of H1-H6 is good, so that the types of solvents in the organic light-emitting layer ink have more choices, and the concentration of the organic host material in the organic light-emitting layer ink can be adjusted to be higher.
Further, the electronic type organic host material containing a crosslinking group is selected from one of the following E1 to E6:
the solubility of E1-E6 is good, so that the types of solvents in the organic light-emitting layer ink have more choices, and the concentration of the organic host material in the organic light-emitting layer ink can be adjusted to be higher.
Further, the mixing ratio of the hole-type organic host material containing a crosslinking group to the electron-type organic host material containing a crosslinking group ranges from 1: 0.1 to 1: 5.
further, the organic doped luminescent material is a phosphorescent material.
Further, the organic doped luminescent material is selected from one of the following D1-D8:
further, the regulator comprises a viscosity regulator and a surface tension regulator which are mixed in any proportion, wherein the viscosity regulator is selected from one or more of alcohol, ether and ester, and the surface tension regulator is selected from one or more of imidazole, imidazole derivative, phenol, hydroquinone and isopropyl toluene.
Further, the solvent is selected from one or more of liquid organic compounds containing benzene ring structures and liquid naphthalene compounds.
In a second aspect, the present application provides a method for preparing an organic light emitting layer ink, comprising the steps of: weighing the components according to the components and the component content in the first aspect; dissolving the organic main body material and the organic doped luminescent material in the solvent, and heating and stirring at 30-80 ℃ for 30 minutes to 12 hours in the dissolving process to obtain a first mixed solution; adding the regulator into the first mixed solution, and stirring until the regulator and the first mixed solution are uniformly mixed to obtain a second mixed solution; and filtering the second mixed solution to obtain the organic light-emitting layer ink.
In a third aspect, the present application provides a method for forming a light-emitting layer, wherein the organic light-emitting layer ink of the first aspect is deposited on a substrate or a preformed hole transport layer by means of inkjet printing, dried under vacuum, and then heat-treated at 100 ℃ to 200 ℃ for 15 minutes to 2 hours to form the light-emitting layer.
The invention has the beneficial effects that: the hole type organic main body material and the electron type organic main body material in the organic light-emitting layer ink disclosed by the invention both contain crosslinking groups, can be subjected to thermal crosslinking at 100-200 ℃, the temperature range has no adverse effect on other layers of an OLED (organic light-emitting diode), the light-emitting layer has the characteristic of solvent resistance after crosslinking, the light-emitting layer and other layers can be prevented from being mutually soluble, an electron transport layer of the OLED can be prepared by solution processing, and the hole type organic main body material and the electron type organic main body material which are jointly used as the organic main body material can also effectively reduce the efficiency roll-off of the light-emitting layer.
Additional features and advantages of the present application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the present application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
Fig. 1 shows the uv-vis absorption spectrum of the organic light-emitting layer formed in example 1, which was measured without elution.
Fig. 2 is a uv-vis absorption spectrum of the organic light-emitting layer formed in example 1 after elution with o-dichlorobenzene.
Fig. 3 is a uv-vis absorption spectrum measured when the organic light emitting layer formed in example 2 is not eluted.
Fig. 4 is a uv-vis absorption spectrum of the organic light emitting layer formed in example 2 measured after elution with methyl benzoate.
Fig. 5 shows the uv-vis absorption spectrum of the organic light-emitting layer formed in example 3, which was measured without elution.
Fig. 6 is an ultraviolet-visible absorption spectrum of the organic light-emitting layer formed in example 3 after elution with cyclohexylbenzene.
Fig. 7 is a uv-vis absorption spectrum measured when the organic light emitting layer formed in comparative example 1 was not eluted.
Fig. 8 is a uv-vis absorption spectrum of the organic light emitting layer formed in comparative example 1, which was measured after elution with o-dichlorobenzene.
Fig. 9 is a uv-vis absorption spectrum measured when the organic light emitting layer formed in comparative example 2 was not eluted.
Fig. 10 is a uv-vis absorption spectrum of the organic light emitting layer formed in comparative example 2, which was measured after elution with methyl benzoate.
Detailed Description
An organic light-emitting layer ink comprises the following components in percentage by mass: 3-30% of organic main material, 0.1-6% of organic doped luminescent material, 0-10% of regulator and 54-96.9% of solvent, wherein the organic main material comprises a hole type organic main material containing a crosslinking group and an electronic type organic main material containing the crosslinking group, and the thermal crosslinking temperature range of the crosslinking group is 100-200 ℃. The mixing ratio range of the hole type organic main body material containing the crosslinking group and the electron type organic main body material containing the crosslinking group is 1: 0.1 to 1: 5.
at present, the electron transport layer in most devices adopts a vacuum evaporation process, the selected main material has the characteristic of thermal crosslinking, and the thermal crosslinking is realized in the luminescent layer so as to avoid mixing with the electron transport layer, thereby being beneficial to realizing the preparation of the all-solution processing type OLED device.
Wherein the crosslinking group is a vinyl group. The hole-type organic host material containing a crosslinking group is selected from one of the following H1 to H6:
the electronic organic host material containing the crosslinking group is selected from one of the following E1-E6:
the above main materials have good hole or electron transmission capability, and are beneficial to improving the carrier transmission balance capability in the light-emitting layer through specific combination. The existing luminescent layer electronic ink capable of resisting solvents is usually a high molecular material; according to the scheme of the application, the small molecular material with the crosslinking performance is convenient to dissolve in preparation, and the luminescent layer is resistant to solvents after being formed, which is not common. The organic host material comprises a hole type organic host material and an electron type organic host material, and the mixture of the hole type organic host material and the electron type organic host material can enable the formed light-emitting layer to have bipolar transmission performance.
The organic doped luminescent material is a phosphorescent material, and is selected from one of the following D1-D8:
the hole type organic main body materials containing the crosslinking groups from H1 to H6, the electron type organic main body materials containing the crosslinking groups from E1 to E6 and the organic doping luminescent materials from D1 to D8 have good solubility, so that the types of solvents in the organic luminescent layer ink have more choices, the concentration of the organic main body materials in the organic luminescent layer ink can be adjusted to be higher, and the thickness of a luminescent layer film formed by ink-jet printing can be higher. The solvent can be one of liquid organic compounds containing benzene ring structures, liquid naphthalene compounds or a plurality of liquid naphthalene compounds mixed in any proportion.
The regulator comprises a viscosity regulator and a surface tension regulator which are mixed in any proportion, wherein the viscosity regulator is selected from one of alcohol, ether and ester or a plurality of mixed in any proportion, and the surface tension regulator is selected from one of imidazole, imidazole derivative, phenol, hydroquinone and isopropyl toluene or a plurality of mixed in any proportion. The viscosity regulator is used for regulating the viscosity of the organic luminous layer ink to 1cps to 20 cps; the surface tension regulator is used for regulating the surface tension of the organic light-emitting layer ink to be 20 dyne/cm-60 dyne/cm.
The method for preparing the organic light-emitting layer ink by adopting the components comprises the following steps: weighing the components according to the components and the component content; dissolving an organic main material and an organic doped luminescent material in a solvent, and heating and stirring at 30-80 ℃ for 30 minutes to 12 hours in the dissolving process to obtain a first mixed solution; adding a regulator into the first mixed solution, and stirring until the regulator is uniformly mixed with the first mixed solution (if the regulator is solid, stirring until the regulator is completely dissolved) to obtain a second mixed solution; and filtering the second mixed solution to obtain the organic light-emitting layer ink.
The prepared ink can be deposited on a substrate or a prefabricated hole transport layer in an ink-jet printing mode, dried under vacuum and then heated for 15 minutes to 2 hours at 100 ℃ to 200 ℃ to form a light-emitting layer.
Example 1
Weighing the components of the organic luminous layer ink according to the mass fraction; comprises 4.5 percent of crosslinking organic main body material, wherein the mass fraction of the cavity type organic main body material is 3.6 percent, and the mass fraction of the electron type organic main body material is 0.9 percent; 0.5% of organic doped luminescent material; 5% of a regulator, wherein the mass fraction of the viscosity regulator is 4%, and the mass fraction of the surface tension regulator is 1%; and 90% of a solvent.
The hole type organic main material is H1, the electron type organic main material is E3, the organic doped luminescent material is D7, the surface tension regulator is hydroquinone, the viscosity regulator is methyl o-methoxybenzoate, and the main solvent is o-dichlorobenzene.
Dissolving the weighed crosslinking organic main body material and the organic doped luminescent material in a solvent, and heating and stirring the solution at 60 ℃ for 1 hour in the dissolving process to obtain a first mixed solution. Adding the weighed regulator into the first mixed solution, stirring for 0.5 hour, and completely dissolving the surface tension regulator and the viscosity regulator in the mixed solution to obtain a second mixed solution; and filtering the second solution by using a needle filter with the pore diameter of 0.22 micron to obtain the organic light-emitting layer ink, wherein the particle size of the filtered organic light-emitting layer ink is less than 0.2 micron.
The surface tension regulator is added to regulate the surface tension of the organic light-emitting layer ink, and the surface tension of the organic light-emitting layer ink of the embodiment is 34 dyne/cm. The viscosity regulator is added to regulate the viscosity of the organic light-emitting layer ink, and the viscosity of the organic light-emitting layer ink of the embodiment is 1.8 cps.
The prepared organic luminescent layer ink is used in the preparation process of the organic luminescent layer through an ink-jet printing process. Specifically, the organic light-emitting layer ink is deposited on a prepared substrate by an ink-jet printing mode, vacuum drying is carried out for 10 minutes under the condition of 0.1Pa, and then the organic light-emitting layer is formed after heating treatment is carried out for 30 minutes under the condition of 150 ℃.
FIG. 1 (abscissa of FIGS. 1 to 10 represents wavelength in nm; ordinate represents spectral intensity in normalized units) is a UV-VIS absorption spectrum measured when the finally-formed organic light-emitting layer in example 1 is not eluted, and FIG. 2 is a UV-VIS absorption spectrum measured when the finally-formed organic light-emitting layer in example 1 is eluted with o-dichlorobenzene. Through the comparison between fig. 1 and fig. 2, it can be seen that the ultraviolet-visible absorption spectrum intensity of the organic light-emitting layer after being eluted by the solvent is reduced, but the reduction range is very small, which indicates that the organic light-emitting layer has certain solvent resistance.
Example 2
Providing components of the organic light-emitting layer ink according to mass fractions; comprises 3 percent of crosslinking organic main material, wherein the mass fraction of the cavity type organic main material is 1.8 percent, and the mass fraction of the electron type organic main material is 1.2 percent; 0.6% of organic doped luminescent material; 3% of regulator, 2% of viscosity regulator and 1% of surface tension regulator; and 93.4% of a solvent.
The hole type organic host material is H2, the electron type organic host material is E1, the organic doped luminescent material is D1, the surface tension regulator is isopropyl toluene, the viscosity regulator is diphenyl ether, and the main solvent is methyl benzoate.
Dissolving the weighed crosslinking organic main body material and the organic doped luminescent material in a solvent, and heating and stirring the solution at 80 ℃ for 30 minutes in the dissolving process to obtain a first mixed solution. Adding the weighed regulator into the first mixed solution, stirring for 0.5 hour, and completely dissolving the surface tension regulator and the viscosity regulator in the mixed solution to obtain a second mixed solution; and filtering the second solution by using a needle filter with the pore diameter of 0.22 micron to obtain the organic luminescent layer ink, wherein the particle size of the filtered organic luminescent layer ink is less than 0.2 micron.
The surface tension regulator is added to regulate the surface tension of the organic light-emitting layer ink, and the surface tension of the organic light-emitting layer ink of the embodiment is 38.5 dyne/cm. The viscosity regulator is added to regulate the viscosity of the organic light-emitting layer ink, and the viscosity of the organic light-emitting layer ink of the embodiment is 2.4 cps.
The prepared organic light-emitting layer ink is deposited on a substrate by means of ink-jet printing, is dried in vacuum for 10 minutes under the condition of 0.1Pa, and is heated and treated for 45 minutes under the condition of 180 ℃ to form an organic light-emitting layer.
Fig. 3 is a uv-vis absorption spectrum measured when the organic light emitting layer finally formed in example 2 is not eluted, and fig. 4 is a uv-vis absorption spectrum measured when the organic light emitting layer finally formed in example 2 is eluted with methyl benzoate. The comparison between fig. 3 and fig. 4 shows that the ultraviolet-visible absorption spectrum intensity of the organic light-emitting layer is only slightly reduced after the organic light-emitting layer is eluted by the solvent, which indicates that the organic light-emitting layer has certain solvent resistance.
Example 3
Providing components of the organic light-emitting layer ink according to mass fractions; comprises 6.4 percent of cross-linking type organic main material, wherein the mass fraction of the cavity type organic main material is 3.2 percent, and the mass fraction of the electron type organic main material is 3.2 percent; 1.6% of organic doped luminescent material; 5% of a regulator, wherein the mass fraction of the viscosity regulator is 3%, and the mass fraction of the surface tension regulator is 2%; and 87% of solvent.
The hole type organic host material is H6, the electron type organic host material is E5, the organic doped luminescent material is D6, the surface tension regulator is phenol, the viscosity regulator is diphenyl ether, and the main solvent is cyclohexylbenzene.
Dissolving the weighed crosslinking organic main body material and the organic doped luminescent material in a solvent, and heating and stirring for 1 hour at 80 ℃ in the dissolving process to obtain a first mixed solution. Adding the weighed regulator into the first mixed solution, stirring for 0.5 hour, and completely dissolving the surface tension regulator and the viscosity regulator in the mixed solution to obtain a second mixed solution; and filtering the second solution by using a needle filter with the pore diameter of 0.22 micron to obtain the organic light-emitting layer ink, wherein the particle size of the filtered organic light-emitting layer ink is less than 0.2 micron.
The surface tension regulator is added to regulate the surface tension of the organic light-emitting layer ink, and the surface tension of the organic light-emitting layer ink of the embodiment is 43.2 dyne/cm. The viscosity regulator is added to regulate the viscosity of the organic light-emitting layer ink, and the viscosity of the organic light-emitting layer ink of the embodiment is 3.3 cps.
The prepared organic light-emitting layer ink is deposited on a substrate by means of ink-jet printing, is dried in vacuum for 10 minutes under the condition of 0.1Pa, and then is heated and treated for 45 minutes under the condition of 200 ℃ to form an organic light-emitting layer.
Fig. 5 is a uv-vis absorption spectrum measured when the organic light emitting layer finally formed in example 3 is not eluted, and fig. 6 is a uv-vis absorption spectrum measured when the organic light emitting layer finally formed in example 3 is eluted with cyclohexylbenzene. It can be seen from the comparison between fig. 5 and fig. 6 that the ultraviolet-visible absorption spectrum intensity of the organic light-emitting layer after being eluted by the solvent is slightly reduced, but the absorption characteristics of the organic material of the light-emitting layer are still maintained, which indicates that the organic light-emitting layer has a certain solvent resistance.
Example 4
Ultrasonically cleaning the prefabricated ITO glass for 15 minutes by using cleaning fluid, deionized water and isopropanol in sequence, and drying the ITO glass in a 70 ℃ drying oven; treating the dried ITO glass for 15 minutes by using an ultraviolet ozone cleaning machine; then 200 microliter of Pedot is dripped, namely PSS solution is coated on ITO glass in a spin mode at the rotating speed of 2000 rpm/min for 40 seconds, and then the ITO glass is annealed and dried for 15 minutes at the temperature of 150 ℃ to form a hole injection layer with the thickness of 40 nm; selecting PVK (polyvinyl carbazole) as a hole transport layer material, dropwise adding 100 microliters of PVK solution on a hole injection layer, spin-coating at a rotating speed of 1500 rpm/min for 60 seconds, and then annealing and drying at a temperature of 100 ℃ for 1 hour to form a hole transport layer with a thickness of 20 nm; the organic light-emitting layer ink prepared in example 3 was selected, added to an ink cartridge having an inkjet droplet volume of 10 picoliters, and deposited on the hole transport layer by an inkjet printer (Dimatix 2850), and then vacuum-dried for 10 minutes under a condition of 0.1Pa, and then heat-treated for 45 minutes under a condition of 200 ℃ to form a light-emitting layer having a thickness of 40 nm; selecting 1,3, 5-tri (1-phenyl-1H-benzimidazole-2-yl) benzene (TPBi) as an electron transport layer material, dripping 100 microliters of TPBi solution on a luminescent layer, carrying out spin coating for 60 seconds at the rotating speed of 1000 rpm/min, and then carrying out annealing drying for 1 hour at the temperature of 100 ℃ to form an electron transport layer with the thickness of 30 nm; transferring the unfinished device into a cavity of an evaporator, and forming an electron injection layer with the thickness of 2nm at the speed of 0.01 nm/s, wherein the electron injection layer is made of (8-hydroxyquinoline) lithium; and forming a cathode layer at the speed of 0.1 nm/s, wherein the thickness of the cathode layer is 100 nm, and the cathode layer is made of metal aluminum to obtain the OLED device.
The obtained green light organic electroluminescent device is driven by DC voltage, and has a brightness of 1000cd/m2When the organic electroluminescent device is used, the CIE color coordinate of the organic electroluminescent device is stabilized at (0.313, 0.630). The maximum current efficiency of the green organic electroluminescent device is 51.45 cd/A, and the brightness is 1000cd/m2The maximum current efficiency was 43.89 cd/A, and the efficiency roll-off was 14.69%.
Comparative example 1
In this comparative example, compared to example 1, only the hole-type organic host material was changed to NPB, i.e., N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, with a mass fraction of 3.6%, and the electron-type organic host material was changed to C1, with a mass fraction of 0.9%. Other compounds and proportions in the organic light emitting layer ink were the same as in example 1. The ink preparation method, the inkjet printing process, and the like were the same as in example 1.
Fig. 7 is a uv-vis absorption spectrum measured when the finally-formed organic light emitting layer in comparative example 1 is not eluted, and fig. 8 is a uv-vis absorption spectrum measured after the finally-formed organic light emitting layer in comparative example 1 is eluted with o-dichlorobenzene. It can be seen from the comparison between fig. 7 and fig. 8 that the intensity of the ultraviolet-visible absorption spectrum of the organic light-emitting layer is greatly reduced after the organic light-emitting layer is eluted by the solvent, which indicates that the organic light-emitting layer is dissolved and damaged by the solvent during the elution process.
Comparative example 2
Compared with example 2, the mass fraction of the hole-type organic host material is 1.8% and the mass fraction of the electron-type organic host material is 1.2% by changing the hole-type organic host material to CBP, i.e., 4' -bis (9-carbazole) biphenyl. Other compounds and proportions in the organic light emitting layer ink were the same as those in example 2. The ink preparation method, the inkjet printing process, and the like were the same as in example 2.
Fig. 9 is a uv-vis absorption spectrum measured when the organic light emitting layer finally formed in comparative example 2 is not eluted, and fig. 10 is a uv-vis absorption spectrum measured when the organic light emitting layer finally formed in comparative example 2 is eluted with methyl benzoate. It can be seen from the comparison between fig. 9 and fig. 10 that the intensity of the ultraviolet-visible absorption spectrum of the organic light-emitting layer is greatly reduced after the organic light-emitting layer is eluted by the solvent, which indicates that the organic light-emitting layer is dissolved and damaged by the solvent during the elution process.
Comparative example 3
Preparing an ink-jet printing OLED device: this comparative example was conducted in the same manner as in example 4 except that the organic light-emitting layer ink used contained no electron-type host material E5 and the host material included only the crosslinked hole-type organic host material H6 in a mass fraction of 6.4%.
The green organic electroluminescent device obtained in the comparative example was driven by DC voltage with a luminance of 1000cd/m2When the organic electroluminescent device is used, the color coordinate of the organic electroluminescent device is stabilized at (0.308, 0.632). The green organic electroluminescent device obtained in this comparative example had a maximum current efficiency of 48.30 cd/A and a luminance of 1000cd/m2The maximum current efficiency was 27.61 cd/A and the efficiency roll-off was 42.84%.
By comparing comparative example 3 with example 4, it can be seen that the collocation of the crosslinked hole type organic host material and the crosslinked electron type organic host material can effectively reduce the efficiency roll-off.
In order to realize that the luminescent layer has both solvent resistance and bipolar carrier transmission performance so as to optimize the OLED luminescent effect, the invention selects the organic main material containing vinyl and the specific organic doped luminescent material with better solubility, and the materials are blended into the organic luminescent layer ink with specific properties in a breakthrough manner through reasonable material collocation and selection, wherein the viscosity of the organic luminescent layer ink is 1cps-20 cps; the surface tension is 20 dyne/cm-60 dyne/cm, the particle size is less than 0.2 micron, and the ink can be suitable for an ink-jet printing process and meet the requirement of an ink-jet printer nozzle on electronic ink.
In the description of the present specification, reference to the description of the terms "one embodiment," "certain embodiments," "illustrative embodiments," "example," "specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (10)
1. An organic light-emitting layer ink is characterized by comprising the following components in percentage by mass: 3% -30% of organic main material, 0.1% -6% of organic doped luminescent material, 0% -10% of regulator and 54% -96.9% of solvent, wherein the organic main material comprises a hole type organic main material containing a crosslinking group and an electronic type organic main material containing the crosslinking group, and the thermal crosslinking temperature range of the crosslinking group is 100-200 ℃.
2. The organic light-emitting layer ink according to claim 1, wherein the hole-type organic host material containing a crosslinking group is selected from one of the following H1 to H6:
3. the organic light-emitting layer ink according to claim 1, wherein the electron-type organic host material containing a crosslinking group is selected from one of the following E1 to E6:
4. the organic light-emitting layer ink according to claim 1, wherein a mixing ratio of the hole-type organic host material containing a crosslinking group to the electron-type organic host material containing a crosslinking group ranges by mass from 1: 0.1 to 1: 5.
5. the organic light-emitting layer ink according to claim 1, wherein the organic doped light-emitting material is a phosphorescent material.
6. The organic light-emitting layer ink as claimed in claim 5, wherein the organic doped light-emitting material is selected from one of the following D1-D8:
7. the organic light-emitting layer ink according to claim 1, wherein the modifier comprises a viscosity modifier and a surface tension modifier, the viscosity modifier is one or more selected from alcohols, ethers and esters, and the surface tension modifier is one or more selected from imidazole, imidazole derivatives, phenol, hydroquinone and isopropyl toluene.
8. The organic light-emitting layer ink according to claim 1, wherein the solvent is one or more selected from a liquid organic compound containing a benzene ring structure and a liquid naphthalene compound.
9. A preparation method of organic light-emitting layer ink is characterized by comprising the following steps: weighing the components according to the components and the component content of any one of claims 1 to 8; dissolving the organic main body material and the organic doped luminescent material in the solvent, and heating and stirring at 30-80 ℃ for 30 minutes to 12 hours in the dissolving process to obtain a first mixed solution; adding the regulator into the first mixed solution, and stirring until the regulator and the first mixed solution are uniformly mixed to obtain a second mixed solution; and filtering the second mixed solution to obtain the organic light-emitting layer ink.
10. A method for forming a light-emitting layer, wherein the organic light-emitting layer ink according to any one of claims 1 to 8 is deposited on a substrate or a prepared hole transport layer by means of ink-jet printing, dried under vacuum, and then heat-treated at 100 to 200 ℃ for 15 minutes to 2 hours to form a light-emitting layer.
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