Display panel and its manufacturing method

Abstract

This application discloses a display panel and its fabrication method. The display panel includes an array substrate with pixel electrodes, an electrochromic layer disposed on the pixel electrodes, and a common cathode electrode. The electrochromic layer includes multiple electrochromic units with different emission colors, each corresponding to a pixel electrode. The common cathode electrode is located between adjacent electrochromic units with different emission colors. By adding a common cathode electrode between electrochromic units with different emission colors, this application allows the pixel electrodes to act as working electrodes and the common cathode electrode to act as counter electrodes during the electrochemical deposition of electrochromic units. This creates a uniform electric field in the horizontal plane, enabling pixelated deposition of electrochromic units using a single substrate without the need for a separate counter electrode substrate. Compared to existing three-electrode deposition structures, this application effectively suppresses short circuits during electrochromic material deposition on high-resolution substrates.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a display panel and its manufacturing method. Background Technology

[0002] Electrochromic technology is a novel display technology with promising applications in the manufacture of electrochromic display devices. Electrochromic materials can be deposited through electrochemical polymerization, significantly reducing costs compared to processes like inkjet printing or vapor deposition. Typical electrochemical polymerization processes use a three-electrode approach for pixelated deposition, with the working electrode substrate and the counter electrode substrate placed horizontally opposite each other to create a uniform vertical electric field between them. However, this method suffers from difficulties in controlling the electrode spacing and the tendency for polymer to adhere to the counter electrode substrate. With the development of high-resolution display devices, the spacing between adjacent pixels needs to be minimized. Using this approach can lead to short circuits caused by polymer contact between adjacent pixels, resulting in display device failure.

[0003] Therefore, existing electrochemical polymerization methods have shortcomings and urgently need improvement. Summary of the Invention

[0004] This invention provides a display panel and its manufacturing method to solve the technical problem that existing display panels use three electrodes to deposit electrochromic materials, which easily leads to adhesion and short circuits between polymers of adjacent pixels, causing display panel failure.

[0005] To solve the above problems, the technical solution provided by the present invention is as follows:

[0006] This invention provides a display panel, comprising:

[0007] An array substrate includes a plurality of thin-film transistors arranged in an array and a plurality of pixel electrodes disposed on the thin-film transistors, wherein the pixel electrodes are electrically connected to the corresponding thin-film transistors;

[0008] An electrochromic layer, disposed on the pixel electrode, includes multiple electrochromic units of different emitting colors arranged in an array, each electrochromic unit corresponding to one of the multiple pixel electrodes; and

[0009] A common cathode electrode is disposed on the thin-film transistor, located between adjacent electrochromic units that emit different colors of light.

[0010] In some embodiments of this application, the common cathode electrode and the pixel electrode are disposed on the same layer.

[0011] In some embodiments of this application, the electrochromic layer includes a first electrochromic unit, a second electrochromic unit, and a third electrochromic unit arranged alternately along a first direction and emitting different colors; the plurality of pixel electrodes include a first pixel electrode corresponding to the first electrochromic unit, a second pixel electrode corresponding to the second electrochromic unit, and a third pixel electrode corresponding to the third electrochromic unit; wherein, the display panel includes:

[0012] The first closed loop line is electrically connected to multiple first pixel electrodes;

[0013] The second closed loop line is electrically connected to multiple second pixel electrodes;

[0014] The third closed loop line is electrically connected to multiple third pixel electrodes;

[0015] The fourth closed loop line is electrically connected to multiple common cathode electrodes.

[0016] In some embodiments of this application, the first closed-loop line, the second closed-loop line, the third closed-loop line, and the fourth closed-loop line are all arranged in a ring around the electrochromic layer.

[0017] In some embodiments of this application, the first closed loop line, the second closed loop line, the third closed loop line, and the fourth closed loop line each include a plurality of spaced input ports for transmitting voltage signals.

[0018] In some embodiments of this application, the display panel includes:

[0019] The first metal layer includes at least multiple scan lines;

[0020] A second metal layer, disposed on the first metal layer, includes at least a plurality of data lines; wherein...

[0021] The first closed-loop line, the second closed-loop line, and the third closed-loop line are electrically connected to the corresponding data lines, and the fourth closed-loop line is electrically connected to all the scan lines.

[0022] In some embodiments of this application, the pixel electrode and the common cathode electrode are disposed on the second metal layer, the pixel electrode is electrically connected to the corresponding data line through a first via, and the common cathode electrode is electrically connected to the corresponding scan line through a second via.

[0023] In some embodiments of this application, the second metal layer further includes a bridging electrode that connects the common cathode electrode and the corresponding scan line.

[0024] In some embodiments of this application, the display panel further includes a counter substrate disposed facing the electrochromic layer, and a transparent electrode is disposed on the side of the counter substrate facing the electrochromic layer.

[0025] This application also provides a method for manufacturing the display panel in the above embodiments, comprising the following steps:

[0026] Provides an array substrate containing pixel electrodes and common cathode electrodes;

[0027] The array substrate and a reference electrode are inserted into an electrolyte containing an electrochromic monomer material;

[0028] A first voltage is applied to the common cathode electrode, and a second voltage is applied to the multiple pixel electrodes corresponding to the sub-pixel regions with the same emission color;

[0029] Wherein, the second voltage is greater than the first voltage, and under the action of the electric field formed by the common cathode electrode and the pixel electrode, the electrochromic monomer material undergoes a polymerization reaction and is deposited on the pixel electrode of the corresponding sub-pixel region to form an electrochromic unit.

[0030] The beneficial effects of this invention are as follows: This application adds a common cathode electrode between electrochromic units with different luminescent colors. When depositing electrochromic units on the array substrate via electrochemical polymerization, the pixel electrode can serve as the working electrode, and the common cathode electrode can serve as the counter electrode. This creates a uniform electric field in the horizontal plane, completing the pixelated deposition of the electrochromic units. On one hand, a single substrate can be used directly for electrochromic material deposition, eliminating the need for a separate counter electrode substrate, reducing the volume of the electrolytic cell, simplifying the deposition apparatus, and thus saving costs. On the other hand, compared to existing three-electrode deposition structures, the common cathode electrode design in this application effectively suppresses short circuits on high-resolution substrates during electrochromic material deposition. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments or prior art, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A plan view of the display panel provided in an embodiment of this application;

[0033] Figure 2 This is a schematic diagram of the film layer stacking structure of the display panel provided in the embodiments of this application;

[0034] Figure 3 This is a schematic diagram of the closed-loop line provided in an embodiment of this application;

[0035] Figure 4 This is a schematic diagram of another film layer stack structure of the display panel provided in the embodiments of this application;

[0036] Figure 5 A schematic flowchart illustrating the method for manufacturing a display panel according to an embodiment of this application;

[0037] Figure 6 A schematic diagram of the structure of the electrolytic cell prepared by the electrochromic unit provided in the embodiments of this application;

[0038] Figure 7 A magnified image of the electrochromic unit provided in the embodiments of this application under an optical microscope;

[0039] Figure 8 A magnified image of an electrochromic unit provided for the prior art under an optical microscope.

[0040] Explanation of reference numerals in the attached figures:

[0041] Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0043] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0044] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In this application, unless otherwise expressly specified and limited, "on" or "under" a second feature can include direct contact between the first and second features, or it can include contact between the first and second features not being in direct contact but through another feature between them.

[0045] like Figure 1 and Figure 2 As shown in the illustration, this application provides a display panel comprising an array of thin-film transistors 20, a plurality of pixel electrodes 50, and an electrochromic layer. The thin-film transistors 20 are disposed on a first substrate 10, and the pixel electrodes 50 are disposed on the thin-film transistors 20, each pixel electrode 50 being electrically connected to a corresponding thin-film transistor 20. The electrochromic layer is disposed on the pixel electrodes 50 and includes an array of electrochromic units 60, each emitting a different color, with each electrochromic unit 60 corresponding one-to-one with a plurality of pixel electrodes 50.

[0046] The display panel also includes a common cathode electrode 70, which is disposed on the thin film transistor and located between adjacent electrochromic units 60 that emit different colors of light.

[0047] This application adds a common cathode electrode 70 between electrochromic units 60 with different emitting colors. When depositing the electrochromic units 60 on the array substrate via electrochemical polymerization, the pixel electrode can serve as the working electrode, and the common cathode electrode 70 can serve as the counter electrode. This creates a uniform electric field in the horizontal plane, completing the pixelated deposition of the electrochromic units. The design of the common cathode electrode 70 in this application has two advantages. First, it allows for the deposition of electrochromic materials using a single substrate without the need for a separate counter electrode substrate, reducing the volume of the electrolytic cell and simplifying the deposition equipment, thus saving costs. Second, compared to the existing three-electrode deposition structure, the common cathode electrode design in this application effectively suppresses short circuits on high-resolution substrates during electrochromic material deposition.

[0048] Specifically, the common cathode electrode 70 can be disposed in the same layer as the pixel electrode 50, that is, the common cathode electrode 70 and the pixel electrode 50 can be formed using the same material and the same photomask process. The common cathode electrode 70 includes, but is not limited to, an ITO electrode.

[0049] After the common cathode electrode 70 and pixel electrode 50 are fabricated on the array substrate, the array substrate and reference electrode can be placed in an electrolyte containing electrochromic monomers. The pixel electrode 50 serves as the working electrode, and a constant positive voltage is applied to the corresponding pixel electrode 50. The common cathode electrode 70 serves as the counter electrode, and a constant negative voltage is applied to the common cathode electrode 70. The voltage difference between the pixel electrode 50 and the common cathode electrode 70 is constant, forming a uniform electric field in the horizontal direction. The electrochromic monomers undergo a polymerization reaction to form a polymer, which grows on the corresponding energized pixel electrode 50, forming an electrochromic polymer film, that is, forming an electrochromic unit 60 on the corresponding pixel electrode 50. Compared with the vertical deposition process of three electrodes, the horizontal deposition process of this application can suppress the occurrence of short circuits between adjacent pixels and improve the uniformity of the polymer film.

[0050] In the embodiments of this application, such as Figure 2 As shown, to achieve color display, the electrochromic layer may include a first electrochromic unit 61, a second electrochromic unit 62, and a third electrochromic unit 63, each emitting a different color. The first electrochromic unit 61, the second electrochromic unit 62, and the third electrochromic unit 63 correspond one-to-one with a red electrochromic unit, a green electrochromic unit, and a blue electrochromic unit.

[0051] The first electrochromic unit 61, the second electrochromic unit 62, and the third electrochromic unit 63 can be arranged alternately along the first direction X. The first electrochromic unit 61, the second electrochromic unit 62, and the third electrochromic unit 63 are arranged in multiple rows. In the embodiments of this application, the first direction X can be a row direction, and the direction perpendicular to the first direction X can be a column direction. Each electrochromic unit corresponds to a sub-pixel. In the same row, every three adjacent first electrochromic units 61, second electrochromic units 62, and third electrochromic units 63 constitute a pixel unit. The electrochromic units in the same column emit the same color.

[0052] like Figure 1 and Figure 2 As shown, the plurality of pixel electrodes 50 include a first pixel electrode 51 corresponding to the first electrochromic unit 61, a second pixel electrode 52 corresponding to the second electrochromic unit 62, and a third pixel electrode 53 corresponding to the third electrochromic unit 63.

[0053] Electrochromic units with the same emission color are electrically connected to each other, such as multiple first pixel electrodes 51, multiple second pixel electrodes 52, and multiple third pixel electrodes 53. Multiple common cathode electrodes 70 are also electrically connected to each other. This allows for the deposition of electrochromic units of different colors by selectively applying a working electrode voltage to the corresponding individual pixel electrodes 50.

[0054] Specifically, such as Figure 3 As shown, the display panel includes a first closed-loop line 81, a second closed-loop line 82, a third closed-loop line 83, and a fourth closed-loop line 84. The first closed-loop line 81 is electrically connected to a plurality of first pixel electrodes 51, the second closed-loop line 82 is electrically connected to a plurality of second pixel electrodes 52, the third closed-loop line 83 is electrically connected to a plurality of third pixel electrodes 53, and the fourth closed-loop line 84 is electrically connected to a plurality of common cathode electrodes 70.

[0055] By connecting the pixel electrodes of electrochromic units corresponding to the same emission color through a closed loop, the voltage drop at the far and near ends of the substrate can be reduced, resulting in a more uniform electrochemically deposited polymer film.

[0056] The first closed-loop line 81, the second closed-loop line 82, the third closed-loop line 83, and the fourth closed-loop line 84 all form a ring around the electrochromic layer. That is, the first closed-loop line 81, the second closed-loop line 82, the third closed-loop line 83, and the fourth closed-loop line 84 can be located outside the pixel area of ​​the display panel (non-display area), and the order in which the four closed-loop lines are nested (distance from the pixel area) is not restricted.

[0057] like Figure 3 As shown, the first closed-loop line 81, the second closed-loop line 82, the third closed-loop line 83, and the fourth closed-loop line 84 each include multiple spaced input ports for transmitting voltage signals. Each closed-loop line can have 2, 3, or 4 input ports, and the input ports can be distributed at approximately equal intervals to reduce voltage drop at the far end and minimize the impact of voltage drop on the uniformity of the electrochemically deposited polymer thin film. For example, the first closed-loop line 81 includes two first input ports 811, the second closed-loop line 82 includes two second input ports 821, the third closed-loop line 83 includes two third input ports 831, and the fourth closed-loop line 84 includes two fourth input ports.

[0058] Please see Figure 1 and Figure 2As shown, the display panel also includes multiple scan lines 24 and multiple data lines 26. The scan lines 24 are connected to the gates 21 of the corresponding thin-film transistors 20 in the same row, and the data lines 24 are connected to one of the source and drain electrodes 23 of the corresponding thin-film transistors 20 in the same column. The pixel electrode 50 is connected to the other of the source and drain electrodes 23 of the corresponding thin-film transistor 20.

[0059] The first closed-loop line 81 is electrically connected to the corresponding data line 26. During the deposition of the first electrochromic unit 61, the working electrode voltage is transmitted to the corresponding data line 26 through the first input port 811 of the first closed-loop line 81. The data line 26 then transmits the working electrode voltage to the first pixel electrode 51. The second closed-loop line 82 is also electrically connected to the corresponding data line 26. During the deposition of the second electrochromic unit 62, the working electrode voltage is transmitted to the corresponding data line 26 through the second input port 821 of the second closed-loop line 82. The data line 26 then transmits the working electrode voltage to the second pixel electrode 52. Similarly, during the deposition of the third electrochromic unit 63, the working electrode voltage is transmitted to the corresponding data line 26 through the third input port 831 of the third closed-loop line 83. The data line 26 then transmits the working electrode voltage to the third pixel electrode 53.

[0060] The fourth closed-loop line 84 is electrically connected to all the scan lines 24. When depositing the first electrochromic unit 61, the second electrochromic unit 62, or the third electrochromic unit 63, the counter electrode voltage is transmitted to the scan line 24 through the fourth input port 841 of the fourth closed-loop line 84, and the scan line 24 transmits the counter electrode voltage to the common cathode electrode.

[0061] Specifically, such as Figure 2 As shown, the display panel includes a first metal layer M1 disposed on a first substrate 10. The first metal layer M1 includes scan lines 24 and a gate 21. A gate insulating layer 30 is covered on the first metal layer M1, and the active layer 22 of the thin-film transistor 20 is disposed on the gate insulating layer 30. The display panel also includes a second metal layer M2 disposed on the active layer 22, including the source and drain electrodes 23 and data lines 26 of the thin-film transistor 20. A passivation layer 40 is covered on the second metal layer M2, and the pixel electrode 50 and the common cathode electrode 70 are disposed on the passivation layer 40.

[0062] The first closed loop line 81, the second closed loop line 82, the third closed loop line 83 and the fourth closed loop line can be prepared by individual metal layers, or by patterning the first metal layer M1 or the second metal layer M2.

[0063] Please see Figure 1and Figure 2 The pixel electrode 50 is electrically connected to the corresponding data line 26 through a first via 101, which penetrates the passivation layer 40. The common cathode electrode 70 is electrically connected to the corresponding scan line 24 through a second via 102, which penetrates the passivation layer 40 and the gate insulating layer 30.

[0064] Since the second via 102 is a deep hole relative to the first via 101, a bridging electrode 25 can be provided between the common cathode electrode 70 and the scan line 24 to avoid poor contact in the deep hole, thereby providing a connection. Specifically, the bridging electrode 25 can be disposed in the same layer as the data line 26, that is, the second metal layer M2 also includes the bridging electrode 25.

[0065] Please see Figure 4 The display panel further includes a counter substrate 90 disposed facing the electrochromic layer, and a transparent electrode 110 is disposed on the side of the counter substrate 90 facing the electrochromic layer. The transparent electrode 110 includes, but is not limited to, an ITO electrode. In the embodiments of this application, the display panel is a reflective display panel.

[0066] like Figure 5 and Figure 6 As shown in the embodiment of this application, a method for fabricating the above-mentioned display panel is also provided. The method includes: S10, providing an array substrate comprising a pixel electrode 50 and a common cathode electrode 70; S20, inserting the array substrate and a reference electrode substrate 200 into an electrolyte 300 containing an electrochromic monomer material; applying a first voltage to the common cathode electrode 70, and applying a second voltage to a plurality of pixel electrodes 50 corresponding to sub-pixel areas with the same emission color; wherein the second voltage is greater than the first voltage, and under the action of the electric field formed by the common cathode electrode 70 and the pixel electrode 50, the electrochromic monomer material undergoes a polymerization reaction and is deposited on the corresponding pixel electrode 50 to form an electrochromic unit 60.

[0067] In step S10, the fabrication of the array substrate can be referenced from existing technologies, and will not be described in detail here.

[0068] Electrochromic units 60 with different emission colors need to be electrochemically deposited in steps. Specifically, when the electrochromic unit 60 is divided into a first electrochromic unit 61, a second electrochromic unit 62, and a third electrochromic unit 63 with different emission colors, the electrochromic layer needs to be prepared by electrochemical deposition in three steps.

[0069] In this embodiment of the application, when the first electrochromic unit 61 is a blue electrochromic unit, the second electrochromic unit 62 is a green electrochromic unit, and the third electrochromic unit is a red electrochromic unit, the electrochromic layer includes the preparation of the first electrochromic unit 61, the preparation of the second electrochromic unit 62, and the preparation of the third electrochromic unit 63.

[0070] Specifically, the preparation of the first electrochromic unit 61 involves dissolving an electrochromic monomer material (such as EDOT(3,4-ethylenedioxythiophene)) in an electrolyte, which can be a 1 mol / L PC / LiClO4 solution, and the concentration of the blue electrochromic monomer material is 0.1 mol / L. The array substrate having a common cathode electrode 70 and a pixel electrode 50 is immersed in the electrolyte, and deposition is performed using a constant voltage method. A first voltage (working electrode voltage) is input to the first input port 811 of the first closed loop line 81, and a second voltage (counter electrode voltage) is input to the fourth input port of the fourth closed loop line. The first voltage is a positive voltage, the second voltage is a negative voltage, the voltage difference between the first and second voltages is 1.05V, and the deposition time is 120s.

[0071] After the first electrochromic unit 61 is fabricated, the second electrochromic unit 62 and the third electrochromic unit 63 are fabricated using a similar method described above. The difference is that when fabricating the second electrochromic unit 62, a working electrode voltage is input to the second input port 821 of the second closed-loop line 82; and when fabricating the third electrochromic unit 63, a working electrode voltage is input to the third input port 831 of the third closed-loop line 83. The array substrate is then removed and dried.

[0072] In this embodiment, the resistance values ​​between pairs of sub-pixels (between adjacent electrochromic units of different colors) on the array substrate prepared above were recorded, as shown in Table 1 below. Here, "B" represents the first electrochromic unit, "G" represents the second electrochromic unit, and "R" represents the third electrochromic unit. The spacing between pairs of sub-pixels is 5 micrometers.

[0073]

[0074] BG GR BR initial resistance Disconnection Disconnection Disconnection Deposition B 7.5kΩ 12kΩ 3.3kΩ Deposition G 7.7kΩ 10kΩ 2.4kΩ Deposition R 3.9kΩ 9.3kΩ 2.6kΩ After rinsing with alcohol 4kΩ 6kΩ 2kΩ

[0075] This application also conducted comparative experiments on the three-electrode deposition process used in the prior art. The prior art array substrate does not have a common cathode electrode; instead, a separate electrode plate is used as the counter electrode. The counter electrode, reference electrode, and array substrate containing pixel electrodes are placed in an electrolyte to prepare electrochromic units. Other experimental conditions are the same as in this application. The resistance values ​​between pairs of sub-pixels (between adjacent electrochromic units of different colors) on the array substrate of the prior art were recorded, as shown in Table 2 below.

[0076] Table 2

[0077] BG BR GR initial resistance Disconnection Disconnection Disconnection Deposition B 4kΩ 95kΩ 92kΩ Deposition G 310Ω 8kΩ 9kΩ Deposition R 210Ω 130Ω 200Ω After rinsing with alcohol 114Ω 97Ω 101Ω

[0078] A comparison of Tables 1 and 2 shows that, in the prior art, after alcohol rinsing, the resistance between any two sub-pixels of the array substrate is between 97-114Ω, indicating a short circuit. In contrast, the array substrate improved by this application exhibits a resistance exceeding 2kΩ between any two sub-pixels after alcohol rinsing, indicating an open circuit. Therefore, the design of adding a common cathode electrode to the array substrate provided in this application can effectively improve the occurrence of short circuits between pixels.

[0079] Please see Figure 7 and Figure 8 , Figure 7 This is a magnified optical microscope image of the electrochromic layer provided in the embodiments of this application. Figure 8 A magnified optical microscope image of an electrochromic layer provided for the prior art. From Figure 7 and Figure 8 As can be seen from the comparison, Figure 7 The film uniformity is better than Figure 8 The uniformity of the film layer. It is evident that the common cathode electrode design provided in this application, employing a horizontal deposition process, can improve the uniformity of pixel film thickness compared to a vertical deposition process.

[0080] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0081] The above provides a detailed description of a display panel and its manufacturing method provided by the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of the present invention. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A display panel, characterized by, The display panel comprises: an array substrate comprising a plurality of thin film transistors arranged in an array, a plurality of pixel electrodes arranged on the thin film transistors, the pixel electrodes being electrically connected to the corresponding thin film transistors; an electrochromic layer arranged on the pixel electrodes, comprising a plurality of electrochromic units with different light-emitting colors and arranged in an array, the plurality of electrochromic units corresponding to the plurality of pixel electrodes one by one; and a common cathode electrode arranged on the thin film transistors and located between adjacent electrochromic units with different light-emitting colors; wherein the electrochromic layer comprises first, second and third electrochromic units with different light-emitting colors arranged alternately along a first direction, the plurality of pixel electrodes comprise first, second and third pixel electrodes corresponding to the first, second and third electrochromic units respectively, and the display panel comprises: a first closed loop line electrically connected to the plurality of first pixel electrodes; a second closed loop line electrically connected to the plurality of second pixel electrodes; a third closed loop line electrically connected to the plurality of third pixel electrodes; and a fourth closed loop line electrically connected to the plurality of common cathode electrodes. The common cathode electrode and the pixel electrode are arranged in the same layer.

2. The display panel of claim 1, wherein, The first, second, third and fourth closed loop lines are annular and surround the electrochromic layer.

3. The display panel of claim 1, wherein, The first, second, third and fourth closed loop lines each comprise a plurality of spaced input ports for transmitting voltage signals.

4. The display panel of claim 1, wherein, The display panel comprises:

5. The display panel of claim 1, wherein, a first metal layer comprising at least a plurality of scan lines; a second metal layer arranged on the first metal layer and comprising at least a plurality of data lines; wherein the first, second and third closed loop lines are electrically connected to the corresponding data lines respectively, and the fourth closed loop line is electrically connected to all the scan lines. The pixel electrode and the common cathode electrode are arranged on the second metal layer, the pixel electrode is electrically connected to the corresponding data line through a first via, and the common cathode electrode is electrically connected to the corresponding scan line through a second via.

6. The display panel of claim 5, wherein, The second metal layer further comprises a bridge electrode connecting the common cathode electrode and the corresponding scan line.

7. The display panel of claim 6, wherein, The display panel further comprises a counter substrate arranged facing the electrochromic layer, and the counter substrate is provided with a transparent electrode on the side facing the electrochromic layer.

8. The display panel of claim 1, wherein, The display panel comprises the following steps:

9. A method of producing a display panel as claimed in any one of claims 1 to 8, characterized in that providing an array substrate comprising pixel electrodes and a common cathode electrode; inserting the array substrate and a reference electrode into an electrolyte containing electrochromic monomer material; applying a first voltage to the common cathode electrode and a second voltage to a plurality of pixel electrodes corresponding to a sub-pixel region with the same light-emitting color; wherein the second voltage is greater than the first voltage, and under the action of the electric field formed by the common cathode electrode and the pixel electrode, the electrochromic monomer material undergoes a polymerization reaction and is deposited on the corresponding pixel electrode to form an electrochromic unit. ​

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