A display panel and a method for manufacturing the same

Abstract

The present application provides a display panel and a preparation method thereof, wherein the display panel includes a base substrate and a composite metal layer disposed on the base substrate, wherein the composite metal layer includes: a first sub-metal layer, a second sub-metal layer and a third sub-metal layer stacked in sequence on the base substrate, wherein the second sub-metal layer includes a first metal structure and a second metal structure, the second metal structure covers the first metal structure, the material of the first metal structure is different from the material of the second metal structure, and the first metal structure contains all the metal elements of the second metal structure. The display panel provided by the present application does not need to be provided with a passivation layer and a protective layer, and a second metal structure with a protective function and covering the first metal structure is formed in the second sub-metal layer, which greatly reduces the oxidation risk of the composite metal layer while simplifying the structure and manufacturing process of the display panel and saving the production and manufacturing cost, thereby ensuring the display quality of the display panel.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a display panel and a method for preparing the same. Background Art

[0002] Compared with liquid crystal display panels, organic light-emitting diode (OLED) display panels have the advantages of being lighter, thinner, having better display effects, higher resolution, wider color gamut, lower power consumption, and being able to achieve flexible display. As a result, they have developed rapidly in recent years and have become the preferred display panel type for mobile terminals.

[0003] However, in the current OLED display panel, in order to avoid the side wall oxidation problem of the source and drain metal layers, it is necessary to sequentially form a passivation layer on the source and drain metal layers. However, the passivation layer is prone to bulging and breaking problems, which greatly increases the requirements for the etching process in the manufacturing process, and thus makes it difficult to improve the product yield. In addition, in order to avoid the bulging and breaking problems of the passivation layer, it is also necessary to strictly control the thickness and number of film layers of the source and drain metal layers, so that the conductive copper layer in the source and drain metal layers under this architecture is often in direct contact with the passivation layer. In order to avoid oxidation of the conductive copper layer, it is also necessary to set an additional protective layer on the passivation layer. The setting of the passivation layer and the protective layer makes the overall film structure of the OLED display panel complex, the process steps are numerous, and the production cost remains high. This problem needs to be solved urgently. Summary of the invention

[0004] The present application provides a display panel and a method for preparing the same, which can avoid the sidewall oxidation problem of the source and drain metal layers without providing the passivation layer, simplify the structure and manufacturing process of the OLED display panel, and effectively reduce the production cost.

[0005] In order to achieve the above-mentioned objectives, the display panel and the manufacturing method thereof described in the present application adopt the following technical solutions.

[0006] On the one hand, the present application provides a display panel, which includes: a base substrate and a composite metal layer arranged on the base substrate, the composite metal layer includes: a first sub-metal layer, a second sub-metal layer and a third sub-metal layer stacked in sequence on the base substrate, wherein the second sub-metal layer includes a first metal structure and a second metal structure, the second metal structure covers the first metal structure, the material of the first metal structure is different from the material of the second metal structure, and the first metal structure contains all the metal elements in the second metal structure.

[0007] Optionally, the material of the first metal structure is a metal alloy containing a first metal element and a second metal element; the material of the second metal structure is a metal single substance containing the second metal element, wherein the metal alloy can precipitate a portion of the second metal element during annealing, and the precipitated portion of the second metal element is converted into the metal single substance.

[0008] Optionally, the metal alloy is a copper-manganese alloy, and the metal element is manganese element.

[0009] Optionally, the thickness of the third sub-metal layer is greater than the thickness of the first sub-metal layer.

[0010] Optionally, the thickness of the third sub-metal layer is greater than or equal to 1000 angstroms.

[0011] Optionally, the third sub-metal layer and the first sub-metal layer are made of the same material, which is molybdenum-titanium alloy.

[0012] Optionally, the display panel further includes: a planar layer, wherein the planar layer is disposed on a side of the composite metal layer facing away from the base substrate, and the planar layer is in direct contact with the composite metal layer.

[0013] Optionally, the material of the planar layer is a silicon oxide-based organic material.

[0014] On the other hand, the present application also provides a method for preparing a display panel, the method for preparing a display panel comprising the following steps:

[0015] Providing a base substrate, on which a first sub-metal layer, a metal alloy layer and a third sub-metal layer are sequentially formed, wherein the material of the metal alloy layer is a metal alloy containing a first metal element and a second metal element;

[0016] The first sub-metal layer, the metal alloy layer and the third sub-metal layer are etched and annealed. During the annealing process, part of the second metal element is precipitated from the metal alloy layer, and the precipitated part of the second metal element is converted into a metal element, the metal element forms a second metal structure, and the remaining metal alloy layer forms a first metal structure. The second metal structure covers the first metal structure, wherein the first metal structure and the second metal structure form a second sub-metal layer located between the first sub-metal layer and the third sub-metal layer, and the first sub-metal layer, the second sub-metal layer and the third sub-metal layer form a composite metal layer arranged on the substrate.

[0017] Optionally, the method for preparing the display panel further comprises the following steps:

[0018] A flat layer is formed on a side of the composite metal layer facing away from the substrate, and the flat layer is in direct contact with the composite metal layer.

[0019] The display panel provided in the present application does not require a passivation layer and a protective layer, and a second metal structure with a protective function and covering the first metal structure is formed in the second sub-metal layer. While simplifying the structure and manufacturing process of the display panel and saving production costs, the oxidation risk of the composite metal layer is greatly reduced, thereby ensuring the display quality of the display panel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is a schematic diagram of the film layer structure of a display panel in the prior art;

[0022] Figure 2 A schematic diagram of the film layer structure of a display panel provided in an embodiment of the present application;

[0023] Figure 3 The composite metal layer provided in the embodiment of the present application is Figure 2 Schematic diagram of the cross section at AA in the middle;

[0024] Figure 4 A schematic diagram of the preparation process of a display panel provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, unless otherwise stated, the directional words such as "upper" and "lower" used generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inside" and "outside" refer to the outline of the device.

[0026] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or settings discussed in itself. In addition, the present application provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials. The following is described in detail respectively, and it should be noted that the description order of the following embodiments is not used as a limitation to the preferred order of the embodiments.

[0027] Figure 1 FIG. 1 is a schematic diagram of a film structure of a display panel in the prior art. Figure 1 As shown, in the prior art, a passivation layer 200' is generally provided on the composite metal layer 80' provided on the substrate 10' to avoid the sidewall oxidation problem of the composite metal layer 80'. The passivation layer 200' is generally a composite inorganic film layer formed by a silicon oxide film layer and a silicon nitride film layer. When the film thickness of the composite metal layer 80' located 100' below the passivation layer is large and / or the number of film layers is large, the etching morphology of the composite metal layer 80' is difficult to control, which will make the edge protruding length of the roof structure (i.e., the tip structure) longer and / or the inclination angle of the film edge (i.e., the taper angle) larger, so that the subsequent film formation of the passivation layer 200' has the risk of bulging and breaking. Therefore, in order to reduce the risk of bulging and breaking of the passivation layer 200', more stringent requirements are needed for the etching process, and the film thickness of the composite metal layer 80' needs to be controlled and the film structure needs to be simplified, so that the conductive layer (such as the conductive copper layer) in the composite metal layer 80' is often in direct contact with the passivation layer 200'. In order to avoid the risk of oxidation of the conductive layer in subsequent processes, an additional protective layer 300' needs to be provided on the passivation layer 200' to protect the conductive layer. The protective layer 300' is further provided with a flattening layer 100' to achieve flattening. The provision of the passivation layer 200' and the protective layer 300' makes the overall film structure of the display panel complex, the process steps are numerous, and the production cost remains high.

[0028] In order to solve the above problems, the present application provides a display panel, and the display panel is, for example, an OLED display panel. Figure 2 A schematic diagram of the film layer structure of a display panel provided in an embodiment of the present application; Figure 3 The composite metal layer provided in the embodiment of the present application is Figure 2 The cross-sectional diagram at AA in the middle, combined with Figure 2 and Figure 3As shown, the display panel includes a base substrate 10. The base substrate 10 is a rigid substrate or a flexible substrate, and its material can be glass, plastic, polyimide or the like.

[0029] In this embodiment, the display panel further includes a composite metal layer 80 and a flat layer 100. The composite metal layer 80 is disposed on the base substrate 10 and includes multiple sub-metal layers. The flat layer 100 is disposed on the side of the composite metal layer 80 away from the base substrate 10, and the flat layer 100 is in direct contact with the composite metal layer 80. That is, the flat layer 100 is a film layer formed directly on the surface of the composite metal layer 80 away from the base substrate 10, thereby eliminating the passivation layer and the protective layer originally disposed between the composite metal layer 80 and the flat layer 100, simplifying the film layer structure and manufacturing process of the display panel, and reducing the production cost.

[0030] In this embodiment, the material of the flat layer 100 is a silicon oxide-based organic material with a thickness of 2 to 4 μm. The silicon oxide-based organic material is a polymer compound composed of silicon and oxygen elements, has good leveling properties and a high flattening degree. Compared with the passivation layer composed of a silicon oxide film layer and a silicon nitride film layer, there is no risk of bulging and breakage, and the etching process requirements for the composite metal layer 80 can be reduced, thereby improving the yield of the display panel.

[0031] In this embodiment, in order to solve the side wall oxidation problem caused by the omission of the passivation layer of the display panel, the composite metal layer 80 includes: a first sub-metal layer 810, a second sub-metal layer 820 and a third sub-metal layer 830 stacked in sequence on the base substrate 10, wherein the second sub-metal layer 820 includes a first metal structure 821 and a second metal structure 822, the second metal structure 822 covers the first metal structure 821, the material of the first metal structure 821 is different from the material of the second metal structure 822, and the first metal structure 821 contains all the metal elements in the second metal structure 822.

[0032] In this embodiment, since the second metal structure 822 covers the first metal structure 821, it can protect the first metal structure 821 and prevent the first metal structure 821 from being oxidized during the manufacturing process of the display panel, thereby achieving the elimination of the need to set the passivation layer while effectively ensuring the conductive properties of the composite metal layer 80 and the display quality of the display panel.

[0033] In this embodiment, the material of the first metal structure 821 is a metal alloy containing a first metal element and a second metal element; the material of the second metal structure 822 is a metal single substance containing the second metal element, wherein the metal alloy can precipitate a portion of the second metal element during the annealing process, and the precipitated portion of the second metal element is converted into the metal single substance. The second sub-metal layer 820 can be transformed from a metal alloy layer made of the metal alloy that has been annealed. During the annealing process, part of the second metal element precipitated from the metal alloy layer is converted into the metal element, and the metal element forms the second metal structure 822 in the second sub-metal layer 820, and the remaining metal alloy layer forms the first metal structure 821 in the second sub-metal layer 820. The present application utilizes the property that the metal alloy can precipitate a metal element with antioxidant properties during the annealing process. By annealing a metal alloy layer made of the metal alloy, the metal alloy layer is converted into the second sub-metal layer 820, thereby forming a second metal structure 822 in the composite metal layer 80 that covers and protects the first metal structure 821, thereby solving the side wall oxidation problem of the display panel caused by omitting the passivation layer, and can effectively prevent the flat layer 100 from corroding the composite metal layer 80.

[0034] In this embodiment, the metal alloy is a copper-manganese alloy, and the metal element is a manganese element. Correspondingly, the first metal element is a copper element, and the second metal element is a manganese element. The material of the first metal structure 821 is the copper-manganese alloy, and the material of the second metal structure 822 is the manganese element. The present application utilizes the property that the copper-manganese alloy can precipitate a manganese element with antioxidant properties during the annealing process. A metal alloy layer made of the copper-manganese alloy is annealed to convert it into the second sub-metal layer 820 including the first metal structure 821 and the second metal structure 822, so that the second sub-metal layer 820 has excellent conductive properties and strong antioxidant properties.

[0035] In this embodiment, the thickness of the third sub-metal layer 830 is greater than the thickness of the first sub-metal layer 810. Specifically, in order to improve the surface morphology of the second sub-metal layer 820 and ensure the film quality and conductive performance of the second sub-metal layer 820, the first sub-metal layer 810 is provided on the side of the second sub-metal layer 820 away from the base substrate 10, and the first sub-metal layer 810 has a thinner film thickness; at the same time, in order to further improve the anti-oxidation performance of the second sub-metal layer 820 and further reduce the oxidation risk of the second sub-metal layer 820 during the manufacturing process of the flat layer 100, the third sub-metal layer 830 with a protective effect is provided on the side of the second sub-metal layer 820 away from the base substrate 10, and the third sub-metal layer 830 has a thicker thickness than the first sub-metal layer 810 to enhance the ability of the third sub-metal layer 830 to resist external oxidation invasion. Preferably, the thickness of the third sub-metal layer 830 is greater than or equal to 1000 angstroms.

[0036] In this embodiment, the third sub-metal layer 830 and the first sub-metal layer 810 are made of the same material, which is a molybdenum-titanium alloy. Since the third sub-metal layer 830 and the first sub-metal layer 810 are made of the same material, the types of materials of the composite metal layer 80 can be reduced, thereby reducing the production cost. Of course, the present application does not limit the materials of the first sub-metal layer 810 and the third sub-metal layer 830. In other embodiments of the present application, the material of the first sub-metal layer 810 is, for example, a single molybdenum substance, and the material of the third sub-metal layer 830 is, for example, a molybdenum-titanium alloy.

[0037] In this embodiment, the taper angle of the composite metal layer 80 is between 40° and 80°.

[0038] In this embodiment, the display panel also includes a shading layer 20, a buffer layer 30, an active layer 40, a gate insulating layer 50, a gate layer 60 and an interlayer dielectric layer 70 located between the base substrate 10 and the composite metal layer 80, and the shading layer 20, the buffer layer 30, the active layer 40, the gate insulating layer 50, the gate layer 60 and the interlayer dielectric layer 70 are stacked in sequence on the base substrate 10.

[0039] In this embodiment, a thin film transistor, a capacitor and a plurality of vias are formed on the base substrate 10, the thin film transistor includes a gate, a source 82 and a drain 83, and the capacitor includes a first capacitor electrode 41 and a second capacitor electrode 81; wherein the light shielding layer 20 is made of an opaque metal material, such as copper, and the light shielding layer 20 includes a first light shielding structure 21, a second light shielding structure 22 and a third light shielding structure 23, and the second light shielding structure 22 forms a signal line (i.e., a data line) in the display panel; the buffer layer 30 is a stacked structure formed by a silicon nitride layer and a silicon oxide layer, for example, a first buffer layer of silicon nitride material and a second buffer layer of silicon oxide material The first buffer layer is arranged between the light shielding layer 20 and the second buffer layer, the thickness of the first buffer layer is 500 to 2000 angstroms, and the thickness of the second buffer layer is 1000 to 3000 angstroms; the active layer 40 is made of indium gallium zinc oxide (IGZO), the thickness of the active layer 40 is 300 to 1000 angstroms, the active layer 40 includes the first capacitor electrode 41, the channel 42 in the thin film transistor, and the source region 43 and the drain region 44 located on both sides of the channel 42, the material of the channel 42 in the thin film transistor is indium gallium zinc oxide semiconductor, the first capacitor electrode 41, the source region 43 and the drain region 44 The polar region 44 is formed by indium gallium zinc oxide semiconductor conductor; the gate insulating layer 50 is a silicon oxide film layer, and the thickness of the gate insulating layer 50 is 1000 to 3000 angstroms; the gate layer 60 includes the gate arranged corresponding to the channel 42, and the gate layer 60 is made of metal material, specifically including at least one of copper element, molybdenum element, and molybdenum-titanium alloy; the interlayer dielectric layer 70 is made of silicon oxide material, and the thickness of the interlayer dielectric layer 70 is 3000 to 5000 angstroms; the composite metal layer 80 includes the second capacitor electrode 81, the source electrode 82, the drain electrode 83 and the signal routing line 84; a plurality of vias include penetrating the interlayer dielectric layer The first via 91 and the second via 92 of 70, and the third via 93, the fourth via 94 and the fifth via 95 that penetrate the interlayer dielectric layer 70 and the buffer layer 30, the source 82 is electrically connected to the source region 43 through the first via 91, the drain 83 is electrically connected to the drain region 44 through the second via 92, the source 82 is also electrically connected to the second shading structure 22 through the third via 93, the second capacitor electrode 81 is electrically connected to the first shading structure 21 through the fourth via 94, and the signal trace 84 is electrically connected to the third shading structure 23 through the fifth via 95.

[0040] Figure 4 A schematic diagram of the manufacturing process of the display panel provided in the embodiment of the present application, combined with Figure 2-Figure 4 As shown, the present application also provides a method for preparing a display panel, and the method for preparing a display panel comprises the following steps:

[0041] S01: providing a base substrate 10, and sequentially forming a first sub-metal layer 810, a metal alloy layer and a third sub-metal layer 830 on the base substrate 10, wherein the material of the metal alloy layer is a metal alloy containing a first metal element and a second metal element;

[0042] S02: Etching and annealing the first sub-metal layer 810, the metal alloy layer and the third sub-metal layer 830. During the annealing process, part of the second metal element is precipitated from the metal alloy layer, and the precipitated part of the second metal element is converted into a metal element. The metal element forms a second metal structure 822, and the remaining metal alloy layer forms a first metal structure 821. The second metal structure 822 covers the first metal structure 821, wherein the first metal structure 821 and the second metal structure 822 form a second sub-metal layer 820 located between the first sub-metal layer 810 and the third sub-metal layer 830, and the first sub-metal layer 810, the second sub-metal layer 820 and the third sub-metal layer 830 form a composite metal layer 80 arranged on the base substrate 10.

[0043] In this embodiment, the method for preparing the display panel further includes the following steps:

[0044] S03 : forming a planar layer 100 on a side of the composite metal layer 80 facing away from the base substrate 10 , wherein the planar layer 100 is in direct contact with the composite metal layer 80 .

[0045] The planar layer 100 is made of silicon oxide-based organic material and has a thickness of 2-4 μm.

[0046] In this embodiment, step S01 includes the following steps:

[0047] S01-1: providing a substrate 10;

[0048] S01-2: forming a light shielding layer 20 on the base substrate 10, and patterning to form a first light shielding structure 21, a second light shielding structure 22 and a third light shielding structure 23, wherein the light shielding layer 20 is made of a light-impermeable metal material, such as copper;

[0049] S01-3: forming a buffer layer 30 on the light shielding layer 20, wherein the buffer layer 30 comprises a first buffer layer and a second buffer layer sequentially stacked on the light shielding layer 20, wherein the first buffer layer is made of silicon nitride, the second buffer layer is made of silicon oxide, the thickness of the first buffer layer is 500 to 2000 angstroms, and the thickness of the second buffer layer is 1000 to 3000 angstroms;

[0050] S01-4: forming a patterned active layer 40 on the buffer layer 30 , wherein the active layer 40 is made of an indium gallium zinc oxide semiconductor material and includes a channel 42 ;

[0051] S01-5: forming a gate insulating layer 50 and a gate layer 60 on the active layer 40 in sequence and patterning them, wherein the patterned gate layer 60 includes a gate arranged corresponding to the channel 42, and then conducting the exposed active layer 40 to form a conductorized first capacitor electrode 41, a source region 43 and a drain region 44 on the active layer 40, wherein the gate insulating layer 50 is made of a silicon oxide film with a thickness of 1000 to 3000 Å, and the gate layer 60 is made of a metal material, specifically including at least one of copper, molybdenum, and molybdenum-titanium alloy;

[0052] S01-6: forming an interlayer dielectric layer 70 on the gate layer 60, wherein the interlayer dielectric layer 70 is made of silicon oxide and has a thickness of 3000 to 5000 angstroms;

[0053] S01-7: A first sub-metal layer 810, a metal alloy layer and a third sub-metal layer 830 are sequentially formed on the interlayer dielectric layer 70, wherein the material of the metal alloy layer is a metal alloy containing a first metal element and a second metal element, and the thickness of the third sub-metal layer 830 is greater than or equal to 1000 angstroms.

[0054] In this embodiment, step S02 includes the following steps:

[0055] S02-1: performing etching on the first sub-metal layer 810, the metal alloy layer and the third sub-metal layer 830, wherein the etching is performed by wet etching, and after the etching, the taper angles of the first sub-metal layer 810, the metal alloy layer and the third sub-metal layer 830 are all within a range of 40° to 80°;

[0056] S02-2: Annealing the first sub-metal layer 810, the metal alloy layer and the third sub-metal layer 830. During the annealing process, part of the second metal element is precipitated from the metal alloy layer, and the precipitated part of the second metal element is converted into a metal element, and the metal element forms a second metal structure 822. The remaining metal alloy layer forms a first metal structure 821. The second metal structure 822 covers the first metal structure 821, wherein the first metal structure 821 and the second metal structure 822 form a second sub-metal layer 820 located between the first sub-metal layer 810 and the third sub-metal layer 830, and the first sub-metal layer 810, the second sub-metal layer 820 and the third sub-metal layer 830 form a composite metal layer 80 disposed on the base substrate 10, wherein the composite metal layer 80 includes a second capacitor electrode 81, the source electrode 82, the drain electrode 83 and a signal trace 84;

[0057] Among them, the display panel also includes a plurality of vias formed by an etching process, the plurality of vias include a first via 91 and a second via 92 penetrating the interlayer dielectric layer 70, and a third via 93, a fourth via 94 and a fifth via 95 penetrating the interlayer dielectric layer 70 and the buffer layer 30, the source 82 is electrically connected to the source region 43 through the first via 91, the drain 83 is electrically connected to the drain region 44 through the second via 92, the source 82 is also electrically connected to the second shading structure 22 through the third via 93, the second capacitor electrode 81 is electrically connected to the first shading structure 21 through the fourth via 94, and the signal line 84 is electrically connected to the third shading structure 23 through the fifth via 95.

[0058] In summary, the present application provides a display panel and a preparation method thereof, wherein the display panel includes a base substrate and a composite metal layer disposed on the base substrate, wherein the composite metal layer includes: a first sub-metal layer, a second sub-metal layer and a third sub-metal layer stacked in sequence on the base substrate, wherein the second sub-metal layer includes a first metal structure and a second metal structure, the second metal structure covers the first metal structure, the material of the first metal structure is different from the material of the second metal structure, and the first metal structure contains all the metal elements in the second metal structure. The display panel provided by the present application does not need to be provided with a passivation layer and a protective layer, and a second metal structure having a protective function and covering the first metal structure is formed in the second sub-metal layer, which greatly reduces the oxidation risk of the composite metal layer while simplifying the structure and manufacturing process of the display panel and saving the production and manufacturing cost, thereby ensuring the display quality of the display panel.

[0059] The above is a detailed introduction to a display panel and a preparation method thereof provided in an embodiment of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A display panel, characterized in that: include: A base substrate and a composite metal layer disposed on the base substrate, the composite metal layer comprising: a first sub-metal layer, a second sub-metal layer and a third sub-metal layer stacked in sequence on the base substrate, wherein the second sub-metal layer comprises a first metal structure and a second metal structure, the second metal structure covers the first metal structure, the material of the first metal structure is different from that of the second metal structure, and the first metal structure contains all the metal elements in the second metal structure, and the composite metal layer comprises a source electrode and a drain electrode; The display panel further includes a gate layer, and the gate layer is located between the composite metal layer and the base substrate.

2. The display panel according to claim 1, characterized in that: The material of the first metal structure is a metal alloy containing a first metal element and a second metal element; the material of the second metal structure is a metal single substance containing the second metal element, wherein the metal alloy can precipitate part of the second metal element during annealing, and the precipitated part of the second metal element is converted into the metal single substance.

3. The display panel according to claim 2, characterized in that: The metal alloy is a copper-manganese alloy, and the metal element is a manganese element.

4. The display panel according to claim 1, characterized in that: The thickness of the third sub-metal layer is greater than the thickness of the first sub-metal layer.

5. The display panel according to claim 4, characterized in that: The thickness of the third sub-metal layer is greater than or equal to 1000 angstroms.

6. The display panel according to claim 4, characterized in that: The third sub-metal layer and the first sub-metal layer are made of the same material, which is molybdenum-titanium alloy.

7. The display panel according to claim 1, characterized in that: The display panel further includes: a planar layer, which is disposed on a side of the composite metal layer away from the base substrate, and the planar layer is in direct contact with the composite metal layer.

8. The display panel according to claim 7, characterized in that: The material of the planar layer is a silicon oxide-based organic material.

9. A method for preparing a display panel, characterized in that: The following steps are involved: Providing a substrate, on which a gate layer, an interlayer dielectric layer, a first sub-metal layer, a metal alloy layer and a third sub-metal layer are sequentially formed, wherein the material of the metal alloy layer is a metal alloy containing a first metal element and a second metal element; The first sub-metal layer, the metal alloy layer and the third sub-metal layer are etched and annealed. During the annealing process, part of the second metal element is precipitated from the metal alloy layer, and the precipitated part of the second metal element is converted into a metal element. The metal element forms a second metal structure, and the remaining metal alloy layer forms a first metal structure. The second metal structure covers the first metal structure, wherein the first metal structure and the second metal structure form a second sub-metal layer located between the first sub-metal layer and the third sub-metal layer, and the first sub-metal layer, the second sub-metal layer and the third sub-metal layer form a composite metal layer arranged on the substrate, the composite metal layer includes a source and a drain, and the gate layer is located between the composite metal layer and the substrate.

10. The method for preparing a display panel according to claim 9, characterized in that: The method for preparing the display panel further comprises the following steps: A flat layer is formed on a side of the composite metal layer facing away from the substrate, and the flat layer is in direct contact with the composite metal layer.

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