Auxiliary cathode of organic light-emitting diode and preparation method of auxiliary cathode

Abstract

The invention relates to an organic light-emitting diode auxiliary cathode and a preparation method thereof. The preparation method comprises the following steps: forming a first cathode layer on an organic light-emitting diode functional layer; the method comprises the following steps: mixing nano-silver in a fluorine-containing solvent to form a mixed solvent; spraying a mixed solvent on the first cathode layer to form a second cathode layer; and heating and baking the organic light-emitting diode functional layer, removing the fluorine-containing solvent, and enabling the nano-silver to be attached to the first cathode layer. According to the invention, the first cathode layer is prepared on the organic light-emitting diode functional layer, and then the nano-silver is patterned on the first cathode layer, so that the electrode reflectivity can be increased through the first cathode layer, and the problems of low microcavity effect and light-emitting efficiency of the organic light-emitting diode device caused by the arrangement of only one layer of nano-silver are solved; and the problem of uneven brightness caused by internal resistance voltage drop of the organic light-emitting diode can also be improved.

Description

Technical Field

[0001] The invention relates to a preparation method, in particular to an organic light emitting diode auxiliary cathode and a preparation method thereof. Background Art

[0002] The existing organic light-emitting diode (OLED) usually needs to add an auxiliary electrode, usually a cathode. Since OLED is a current-driven component, when the external line is too long or too thin, it will cause a serious voltage gradient in the external circuit, causing the voltage actually falling on the OLED component to drop, resulting in a reduction in the panel's luminous intensity. And because the ITO resistance is too large (10ohm / square), it is easy to cause unnecessary external power consumption. Adding an auxiliary electrode to reduce the voltage gradient has become a quick way to increase luminous efficiency and reduce driving voltage.

[0003] The cathode material used in the prior art OLED is usually a metal alloy, such as a magnesium-silver alloy, which is attached to the top of the organic functional layer of the OLED by thermal evaporation to form a cathode.

[0004] In the process of implementing the present invention, the inventors found that the prior art has at least the following problems:

[0005] 1. After the cathode is prepared using the materials and preparation methods used in the above-mentioned prior art OLED, the internal resistance drop (IR drop) of the display panel is often serious due to the poor conductivity of the cathode.

[0006] 2. At the same time, in the above-mentioned prior art organic light emitting diode (OLED) cathode process, a common mask is usually used for thermal evaporation, which easily causes a decrease in the transmittance of the display screen, which is not conducive to its application in the transparent display industry. Summary of the invention

[0007] In order to solve the problems existing in the above-mentioned prior art, the embodiment of the present invention provides an organic light-emitting diode auxiliary cathode and a preparation method thereof. The specific technical solution is as follows:

[0008] In a first aspect, a method for preparing an auxiliary cathode of an organic light emitting diode is provided, comprising the following steps:

[0009] forming a first cathode layer on the organic light emitting diode functional layer;

[0010] Mixing nanosilver into a fluorine-containing solvent to form a mixed solvent;

[0011] spraying a mixed solvent on the first cathode layer to form a second cathode layer; and

[0012] The organic light emitting diode functional layer is heated and baked to remove the fluorine-containing solvent and to make the nano silver adhere to the first cathode layer.

[0013] In a first possible implementation manner of the first aspect, before forming the first cathode layer on the organic light emitting diode functional layer, the following steps are further included:

[0014] forming a thin film transistor;

[0015] forming an indium tin oxide layer on the thin film transistor; and

[0016] An organic light emitting diode functional layer is formed on the indium tin oxide layer.

[0017] In a second possible implementation manner of the first aspect, a material of the first cathode layer is magnesium, silver, aluminum, ytterbium, calcium or alloys thereof.

[0018] In a third possible implementation manner of the first aspect, a thickness of the first cathode layer is 20-100 angstroms.

[0019] In a fourth possible implementation manner of the first aspect, the fluorine-containing solvent is a perfluoroethoxy, toluene or xylene solvent.

[0020] In a fifth possible implementation manner of the first aspect, the weight content of the nanosilver in the mixed solvent is 5-50%.

[0021] In a sixth possible implementation manner of the first aspect, the thickness of the nanosilver attached to the first cathode layer is 100-220 angstroms.

[0022] In a seventh possible implementation manner of the first aspect, the shape of the nanosilver attached to the first cathode layer is regular or irregular.

[0023] In an eighth possible implementation manner of the first aspect, when the organic light emitting diode functional layer is heated and baked, the baking temperature is less than 100 degrees Celsius.

[0024] In a second aspect, an organic light emitting diode auxiliary cathode is provided, which is applied to an organic light emitting diode functional layer on an organic light emitting diode, and includes:

[0025] A first cathode layer is disposed on the organic light emitting diode functional layer; and

[0026] The second cathode layer is arranged on the first cathode layer, and the material of the second cathode layer is nano silver.

[0027] In a first possible implementation manner of the second aspect, the organic light emitting diode further includes:

[0028] Thin film transistors; and

[0029] The indium tin oxide layer is arranged on the thin film transistor, and the organic light emitting diode functional layer is arranged on the indium tin oxide layer.

[0030] In a second possible implementation manner of the second aspect, a material of the first cathode layer is magnesium, silver, aluminum, ytterbium, calcium or their corresponding alloys.

[0031] In a third possible implementation of the second aspect, the thickness of the first cathode layer is 20-100 angstroms.

[0032] In a fourth possible implementation manner of the second aspect, the thickness of the nanosilver is 100-220 angstroms.

[0033] In a fifth possible implementation manner of the second aspect, the shape of the nanosilver is regular or irregular.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] The present invention first prepares a first cathode layer on the organic light emitting diode functional layer, and then patterns nanosilver on the first cathode layer. The first cathode layer can increase the electrode reflectivity, thereby avoiding the microcavity effect and low luminous efficiency of the organic light emitting diode device caused by only setting one layer of nanosilver.

[0036] At the same time, the nanosilver of the present invention is mixed in a fluorine-containing solvent, and the nanosilver is patterned on the first cathode layer through the mixed solvent. Since the fluorine-containing solvent will not damage the OLED functional layer and the nanosilver has good conductivity, the brightness unevenness problem caused by the internal resistance voltage drop of the organic light emitting diode can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 The figure is a schematic flow chart of the steps of a method for preparing an auxiliary cathode of an organic light emitting diode according to an embodiment of the present invention.

[0039] Figure 2 It is a schematic flow chart of steps included before forming the first cathode layer according to an embodiment of the present invention.

[0040] Figure 3 FIG. 1 is a schematic diagram of a process after forming a first cathode layer in step 101 according to an embodiment of the present invention.

[0041] Figure 4 FIG. 1 is a schematic diagram of forming a second cathode layer in step 103 according to an embodiment of the present invention.

[0042] Figure 5 It is a schematic diagram of heating and baking in step 104 of an embodiment of the present invention.

[0043] Figure 6 It is a schematic diagram of forming a thin film transistor, an indium tin oxide layer and an organic light emitting diode functional layer in steps 105-107 of one embodiment of the present invention.

[0044] Figure 7 FIG. 1 is a schematic diagram of an organic light emitting diode auxiliary cathode disposed on an organic light emitting diode 4 according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0046] In one embodiment of the present invention, please refer to Figure 1 , which shows a schematic flow chart of steps of a method 1 for preparing an auxiliary cathode of an organic light emitting diode according to an embodiment of the present invention. The method 1 for preparing an auxiliary cathode of an organic light emitting diode comprises the following steps 101-104, wherein:

[0047] Step 101 , forming a first cathode layer 31 . The first cathode layer 31 is formed on the organic light emitting diode functional layer 41 .

[0048] For details, please refer to Figure 3 , which shows a schematic diagram after the first cathode layer 31 is formed in step 101 of an embodiment of the present invention. The material of the first cathode layer 31 is placed in a crucible in a vapor deposition chamber (not shown in the figure), and the material of the first cathode layer 31 can be selected from magnesium, silver, aluminum, ytterbium, calcium or their corresponding alloys, but is not limited thereto, and those skilled in the art can also select other suitable materials as the material of the first cathode layer 31 according to actual production requirements.

[0049] At the same time, the organic light emitting diode functional layer 41 is placed above the crucible, and the material of the first cathode layer 31 is heated in a vacuum environment so that it is plated on the organic light emitting diode functional layer 41 to form the first cathode layer 31. The thickness of the first cathode layer 31 is preferably For example, it can be 20 angstroms, 40 angstroms, 60 angstroms, 80 angstroms or 100 angstroms. When making a specific selection, it can be selected according to the application field of the first cathode layer 31. For example, when it is used in the field of transparent display, its transmittance needs to be appropriately improved. Therefore, a first cathode layer 31 with a smaller thickness can be appropriately selected, but it is not limited thereto.

[0050] Step 102 , preparing a mixed solvent 33 . Nanosilver is mixed in a fluorine-containing solvent to form a mixed solvent 33 .

[0051] Specifically, the fluorine-containing solvent may be perfluoroethoxy, toluene or xylene solvent, but is not limited thereto. A person skilled in the art may also select other suitable fluorine-containing solvents that will not damage the OLED functional layer according to the teaching of this embodiment. Nanosilver is mixed in the fluorine-containing solvent to form a mixed solvent 33. The weight content of nanosilver in the mixed solvent 33 is preferably 5-50%, for example, 5%, 15%, 25%, 35%, 45% or 50%, but is not limited thereto.

[0052] Step 103 , forming a second cathode layer. Spraying a mixed solvent 33 on the first cathode layer 31 , forming a second cathode layer 32 .

[0053] For details, please refer to Figure 4 , which shows a schematic diagram of forming the second cathode layer 32 in step 103 of an embodiment of the present invention. The mixed solvent 33 is sprayed on the first cathode layer 31 by inkjet printing or printing to pattern the nanosilver to improve the pass rate of the display screen. The shape of the nanosilver can be a regular shape, such as a sphere, a line, a rod or a hollow structure, etc., and can also be an irregular shape, but is not limited thereto.

[0054] Step 104 , heating and baking. The organic light emitting diode functional layer 41 is heated and baked to remove the fluorine-containing solvent and to make the nanosilver adhere to the first cathode layer 31 .

[0055] For details, please refer to Figure 5 , which shows a schematic diagram of heating and baking in step 104 of an embodiment of the present invention. The organic light emitting diode functional layer 41 is placed above the heating plate 2, and the organic light emitting diode functional layer 41 is heated and baked by the heating plate 2. The low-temperature baking method is used during heating and baking. The baking temperature is preferably less than 100 degrees Celsius, for example, 90 degrees Celsius, 80 degrees Celsius or less than 80 degrees Celsius, and the fluorine-containing solvent is evaporated, so that the nanosilver is attached to the first cathode layer 31. The thickness of the nanosilver is preferably For example, the thickness may be 100 angstroms, 140 angstroms, 180 angstroms, or 220 angstroms, but is not limited thereto.

[0056] In a preferred embodiment, please also refer to Figure 2 and Figure 6 , Figure 2 FIG. 1 is a schematic flow chart showing steps before forming the first cathode layer 31 according to an embodiment of the present invention. Figure 6 The schematic diagram of forming a thin film transistor 42, an indium tin oxide layer 43 and an organic light emitting diode functional layer 41 in steps 105-107 of an embodiment of the present invention is shown. Before forming the first cathode layer 31 on the organic light emitting diode functional layer 41, the following steps 105-107 are also included, wherein:

[0057] Step 105: forming a thin film transistor 42. Forming a thin film transistor 42.

[0058] Specifically, a common manufacturing method is to deposit various thin films, such as a semiconductor active layer, a dielectric layer, and a metal electrode layer, on a substrate to form the thin film transistor 42, but the present invention is not limited thereto.

[0059] Step 106 , forming an indium tin oxide layer 43 . The indium tin oxide layer 43 is formed on the thin film transistor 42 .

[0060] Specifically, physical vapor deposition or some sputtering deposition techniques, such as magnetron sputtering, are used to deposit indium tin oxide on the thin film transistor 42 to form the indium tin oxide layer 43, but the present invention is not limited thereto.

[0061] Step 107 , forming an organic light emitting diode functional layer 41 . The organic light emitting diode functional layer 41 is formed on the indium tin oxide layer 43 .

[0062] Specifically, referring to the evaporation method in step 101 , the materials of each layer of the organic light emitting diode functional layer 41 are sequentially evaporated on the indium tin oxide layer 43 , but the present invention is not limited thereto.

[0063] Please refer again Figure 3 , 4 The preparation method 1 of the auxiliary cathode of the organic light-emitting diode of the present embodiment is to first prepare a first cathode layer 31 on the organic light-emitting diode functional layer 41, and then pattern nanosilver on the first cathode layer 31. The first cathode layer 31 can increase the electrode reflectivity, thereby avoiding the microcavity effect and low luminous efficiency of the organic light-emitting diode device caused by only setting one layer of nanosilver.

[0064] Also, please refer to Figure 4 In this embodiment, the nanosilver is mixed in a fluorine-containing solvent, and the nanosilver is patterned on the first cathode layer 31 through the mixed solvent 33. Since the fluorine-containing solvent will not damage the OLED functional layer and the nanosilver has good conductivity, the brightness unevenness problem caused by the internal resistance voltage drop of the organic light emitting diode can be improved.

[0065] In the second embodiment of the present invention, please refer to Figure 7 , which shows a schematic diagram of an organic light emitting diode auxiliary cathode 3 disposed on an organic light emitting diode 4 according to a second embodiment of the present invention. The organic light emitting diode auxiliary cathode 3 is applied to an organic light emitting diode functional layer 41 on the organic light emitting diode 4, and the organic light emitting diode auxiliary cathode 3 includes a first cathode layer 31 and a second cathode layer 32, wherein:

[0066] The first cathode layer 31 is disposed on the organic light emitting diode functional layer 41 to improve the reflectivity of the organic light emitting diode 4. The material of the first cathode layer 31 can be selected from magnesium, silver, aluminum, ytterbium, calcium or their corresponding alloys, but is not limited thereto. Those skilled in the art can also select other suitable materials as the material of the first cathode layer 31 according to actual production requirements. The thickness of the first cathode layer 31 is preferably For example, it can be 20 angstroms, 40 angstroms, 60 angstroms, 80 angstroms or 100 angstroms, but it is not limited to this. The specific selection can be made according to the application field of the first cathode layer 31. For example, when used in the field of transparent display, it is necessary to appropriately improve its transmittance. Therefore, a first cathode layer 31 with a smaller thickness can be appropriately selected.

[0067] The second cathode layer 32 is disposed on the first cathode layer 31. The material of the second cathode layer 32 is nanosilver to improve the conductivity of the organic light emitting diode 4 and improve the brightness unevenness caused by the internal resistance voltage drop of the organic light emitting diode 4. The shape of the nanosilver can be a regular shape, such as a sphere, a line, a rod or a hollow structure, etc., or an irregular shape, but not limited thereto. The thickness of the nanosilver is preferably For example, the thickness may be 100 angstroms, 140 angstroms, 180 angstroms, or 220 angstroms, but is not limited thereto.

[0068] In a preferred embodiment, please refer again to Figure 7 The organic light emitting diode 4 further includes a thin film transistor 42 and an indium tin oxide layer 43 . The indium tin oxide layer 43 is disposed on the thin film transistor 42 , and the organic light emitting diode functional layer 41 is disposed on the indium tin oxide layer 43 , but the present invention is not limited thereto.

[0069] Please refer again Figure 7 The organic light-emitting diode auxiliary cathode 3 of this embodiment has a first cathode layer 31 and a second cathode layer 32. The first cathode layer 31 can increase the electrode reflectivity, avoiding the microcavity effect and low luminous efficiency of the organic light-emitting diode device 4 caused by only setting one layer of nanosilver (the second cathode layer 32). At the same time, nanosilver (the second cathode layer 32) has good conductivity, so it can improve the uneven brightness problem caused by the internal resistance voltage drop of the organic light-emitting diode 4.

[0070] The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not depart from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing an auxiliary cathode of an organic light emitting diode, characterized in that: The following steps are involved: forming a first cathode layer on the organic light emitting diode functional layer; Mixing nanosilver into a fluorine-containing solvent to form a mixed solvent; spraying the mixed solvent on the first cathode layer to form a second cathode layer; and The organic light emitting diode functional layer is heated and baked to remove the fluorine-containing solvent and to make the nano silver adhere to the first cathode layer.

2. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: Before forming the first cathode layer on the organic light emitting diode functional layer, the method further includes the following steps: forming a thin film transistor; forming an indium tin oxide layer on the thin film transistor; and The organic light emitting diode functional layer is formed on the indium tin oxide layer.

3. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: The first cathode layer is made of magnesium, silver, aluminum, ytterbium, calcium or their corresponding alloys.

4. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: The thickness of the first cathode layer is 20-100 angstroms.

5. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: The fluorine-containing solvent is a perfluoroethoxy, toluene or xylene solvent.

6. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: The weight content of the nano silver in the mixed solvent is 5-50%.

7. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: The thickness of the nanosilver attached to the first cathode layer is 100-220 angstroms.

8. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: The shape of the nanosilver attached to the first cathode layer is regular or irregular.

9. The method for preparing an auxiliary cathode of an organic light emitting diode according to claim 1, characterized in that: When the organic light emitting diode functional layer is heated and baked, the baking temperature is less than 100 degrees Celsius.

10. An organic light emitting diode auxiliary cathode, applied to an organic light emitting diode functional layer on an organic light emitting diode, characterized in that: include: A first cathode layer, disposed on the organic light emitting diode functional layer; as well as The second cathode layer is disposed on the first cathode layer, and the material of the second cathode layer is nanosilver.

11. The organic light emitting diode auxiliary cathode according to claim 10, characterized in that: The organic light emitting diode further comprises: Thin film transistors; and The indium tin oxide layer is disposed on the thin film transistor, and the organic light emitting diode functional layer is disposed on the indium tin oxide layer.

12. The organic light emitting diode auxiliary cathode according to claim 10, characterized in that: The first cathode layer is made of magnesium, silver, aluminum, ytterbium, calcium or their corresponding alloys.

13. The organic light emitting diode auxiliary cathode according to claim 10, characterized in that: The thickness of the first cathode layer is 20-100 angstroms.

14. The organic light emitting diode auxiliary cathode according to claim 10, characterized in that: The thickness of the nano silver is 100-220 angstroms.

15. The organic light emitting diode auxiliary cathode according to claim 10, characterized in that: The shape of the nanosilver is regular or irregular.

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