Patent Publication Number: US-2023141534-A1

Title: Display panel, display device, and preparation method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Chinese Patent Application No. 202210773011.8 filed Jun. 30, 2022, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     Embodiments of the present disclosure relate to the field of display technology and, in particular, to a display panel, a display device, and a preparation method. 
     BACKGROUND 
     For existing micro light-emitting diode (micro-LED) display panels or mini light-emitting diode (mini-LED) display panels, the light-emitting diodes (LEDs) are typically transferred to a display substrate for bonding through mass transfer technology. However, limited by the yield of the mass transfer technology, the display panel after the transfer will have some LEDs which emit light abnormally. Generally, the LEDs which emit light abnormally are not repaired directly, but positions of redundant electrodes are retained in pixels and new LEDs are bonded in the positions of the redundant electrode positions for compensation. 
     However, since the positions of the LEDs which emit light abnormally are uncertain, that is, the positions of the redundant electrodes to which the new LEDs are bonded are uncertain, all of the positions of the redundant electrodes are usually developed during a subsequent photolithography technique, so as to ensure that the repaired LEDs can emit light normally. However, at the same time, most of the positions of the redundant electrode not for repair are also directly exposed on the surface. In addition, since the redundant electrodes are typically metal electrodes with relatively high reflectivity, the exposed redundant electrodes increase the reflectivity of a whole screen body, influencing a display effect. 
     SUMMARY 
     The present disclosure provides a display panel, a display device, and a preparation method, so as to adjust the light extraction of the display panel, solve issues about the reflectivity or the light extraction efficiency of the display panel, and improve a display effect. 
     In a first aspect, embodiments of the present disclosure provide a display panel. 
     The display panel includes a base substrate, electrode units, a first light-emitting unit, bank structures and openings disposed among the bank structures, and a functional structure. 
     The electrode units are disposed on a side of the base substrate, where the electrode units include a main electrode unit and a redundant electrode unit. 
     The first light-emitting unit is electrically connected to the main electrode unit. 
     The openings include a first opening, and the redundant electrode unit is disposed in the first opening. 
     Part of first openings are filled with functional structures, and the functional structure is at least partially disposed on a side of the redundant electrode unit facing away from the base substrate. 
     In a second aspect, embodiments of the present disclosure provide a display device. The display device includes a base substrate, electrode units, a first light-emitting unit, bank structures and openings disposed among the bank structures, and a functional structure. The electrode units are disposed on a side of the base substrate, where the electrode units include a main electrode unit and a redundant electrode unit. The first light-emitting unit is electrically connected to the main electrode unit. The openings include a first opening, and the redundant electrode unit is disposed in the first opening. Part of first openings are filled with functional structures, and the functional structure is at least partially disposed on a side of the redundant electrode unit facing away from the base substrate. 
     In a third aspect, embodiments of the present disclosure further provide a preparation method of a display panel. The method includes the steps described below. 
     A base substrate is provided. 
     Electrode units are formed on a side of the base substrate, where the electrode units include a main electrode unit and a redundant electrode unit. 
     A first light-emitting element is electrically connected to the main electrode unit. 
     Bank structures and openings disposed among the bank structures are formed on the base substrate, where the openings include a first opening, and the redundant electrode unit is disposed in the first opening. 
     A functional structure is formed, where part of first openings are filled with functional structures, and the functional structure is at least partially disposed on a side of the redundant electrode unit facing away from the base substrate. 
     According to technical schemes in the embodiments of the present disclosure, the base substrate, the electrode units, the first light-emitting unit, the bank structures, and the functional structure are disposed in the display panel, where the electrode units are disposed on the side of the base substrate and include the main electrode unit and the redundant electrode unit; the first light-emitting unit is electrically connected to the main electrode unit; the openings are formed among the bank structures and include the first opening, where the redundant electrode unit is disposed in the first opening; and the first opening is filled with part of functional structures, and the functional structure is at least partially disposed on the side of the redundant electrode unit facing away from the base substrate. The bank structure may be used for limiting the functional structure so that the functional structure covers the redundant electrode unit. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a structural diagram of a display panel according to an embodiment of the present disclosure; 
         FIG.  2    is a sectional view of the display panel shown in  FIG.  1    taken along AN; 
         FIG.  3    is a sectional view of the display panel shown in  FIG.  1    taken along BB′; 
         FIG.  4    is a flowchart of a preparation method of a display panel according to an embodiment of the present disclosure; 
         FIG.  5    is a structural flowchart of the preparation method of the display panel shown in  FIG.  4   ; 
         FIG.  6    is a sectional view of another display panel according to an embodiment of the present disclosure; 
         FIG.  7    is a flowchart of another preparation method of a display panel according to an embodiment of the present disclosure; 
         FIG.  8    is a structural flowchart of the preparation method of the display panel shown in  FIG.  7   ; 
         FIG.  9    is a partial enlarged view of dashed box a of the display panel shown in  FIG.  2   ; 
         FIG.  10    is a partial enlarged view of dashed box b of the display panel shown in  FIG.  3   ; 
         FIG.  11    is a sectional view of another display panel according to an embodiment of the present disclosure; 
         FIG.  12    is a sectional view of the display panel shown in  FIG.  1    taken along CC′; 
         FIG.  13    is a sectional view of another display panel according to an embodiment of the present disclosure; 
         FIG.  14    is a structural diagram of another display panel according to an embodiment of the present disclosure; 
         FIG.  15    is a sectional view of the display panel shown in  FIG.  14    taken along DD′; 
         FIG.  16    is a sectional view of the display panel shown in  FIG.  14    taken along EE′; 
         FIG.  17    is a sectional view of another display panel according to an embodiment of the present disclosure; and 
         FIG.  18    is a structural diagram of a display device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter the present disclosure is further described in detail in conjunction with the drawings and embodiments. It is to be understood that the embodiments set forth below are intended to illustrate and not to limit the present disclosure. Additionally, it is to be noted that, for ease of description, only part, not all, of structures related to the present disclosure are illustrated in the drawings. 
       FIG.  1    is a structural diagram of a display panel according to an embodiment of the present disclosure.  FIG.  2    is a sectional view of the display panel shown in  FIG.  1    taken along AN.  FIG.  3    is a sectional view of the display panel shown in  FIG.  1    taken along BB′. Referring to  FIGS.  1  to  3   , the display panel includes a base substrate  10 , electrode units  20 , first light-emitting units  31 , bank structures  40  and openings  400  disposed among the bank structures  40 , and functional structures  50 . The electrode units  20  are disposed on a side of the base substrate  10 , where the electrode units include main electrode units  21  and redundant electrode units  22 . The first light-emitting unit  31  is electrically connected to the main electrode unit  21 . The openings  400  include a first opening  401 , and the redundant electrode unit  22  is disposed in the first opening  401 . Part of first openings  401  are filled with functional structures  50  (white filling for illustration in the figures), and the functional structure  50  is at least partially disposed on a side of the redundant electrode unit  22  facing away from the base substrate  10 . 
     The base substrate  10  may be a rigid substrate such as a glass substrate, or the base substrate  10  may be a flexible substrate such as a substrate made of a flexible organic polymer material, which is not limited here. A pixel circuit is disposed on the base substrate  10  and configured to drive a light-emitting unit to emit light. In an embodiment, the electrode unit  20  is further disposed on the base substrate  10 , and the pixel circuit in the base substrate  10  is electrically connected to the light-emitting unit through the electrode unit  20  so as to drive the light-emitting unit to emit light. 
     In the embodiment of the present disclosure, the electrode units  20  include the main electrode unit  21  and the redundant electrode unit  22 . The main electrode unit  21  is electrically connected to the first light-emitting unit  31 . The redundant electrode unit  22  is used as a substitute for the main electrode unit  21  when the first light-emitting unit  31  emits light abnormally due to a connection failure or its own failure. That is, a new light-emitting unit is electrically connected to the redundant electrode unit  22  so that the compensation for the first light-emitting unit  31  which emits light abnormally is implemented. Here, the first light-emitting unit  31  may be understood as a main light-emitting unit, and the new light-emitting unit may be understood as a repair light-emitting unit. In addition, it is to be understood that to reduce process steps, essentially, during the actual preparation, the redundant electrode unit  22  and the main electrode unit  21  are prepared simultaneously through a photolithography technique in the same process step. The redundant electrode unit  22  and the main electrode unit  2  have the same specific structure, material, and function. A main difference between the redundant electrode unit  22  and the main electrode unit  2  is the design of positions of the electrode units. The electrode unit correspondingly connected to the first light-emitting unit  31  is the main electrode unit  21 , and the remaining electrode unit may be considered as the redundant electrode unit  22 . 
     It is to be noted that the main electrode unit  21  and the redundant electrode unit  22  may be an electrode pair here. The light-emitting unit correspondingly and electrically connected to the electrode pair is a horizontal mini-LED, micro-LED, nano light-emitting diode (nano-LED), or the like. That is, two electrodes of the light-emitting unit are on the same side of the light-emitting unit and correspondingly and electrically connected to two electrodes in the electrode pair respectively, thereby implementing the bonding of the light-emitting unit and the electrode unit. 
     In the embodiment of the present disclosure, the bank structure  40  is further disposed on the base substrate  10 , and one of functions of the bank structure  40  is to limit a region in which the redundant electrode unit  22  is disposed. It is to be understood that the bank structures  40  are composed of multiple cross-connected walls disposed on the base substrate  10 . The multiple cross-connected walls may enclose multiple openings  400 . The opening  400  essentially refers to an accommodation space enclosed by the base substrate  10  as a bottom and the bank structures as sidewalls. A film or a structure may be disposed in the opening  400  enclosed by the bank structure  40  to cover the opening. Here, the openings  400  include a first opening  401  formed by walls around the redundant electrode unit  22 , that is, part of the bank structures  40  are disposed around redundant electrode units  22 , and openings  400  formed by the bank structures, that is, the first openings  401 , may accommodate the redundant electrode units  22 . Referring to  FIG.  1   , from a top view, the redundant electrode unit  22  is essentially disposed in the first opening  401 . 
     In addition, the functional structure  50  is further disposed in the display panel in the embodiment of the present disclosure, and the functional structure  50  refers to a structure which has the function of adjusting external light incident on the display panel or the light emitted from the light-emitting unit in the display panel. In an embodiment, the functional structure  50  may be a structure for reducing the reflection of the external light to prevent the display panel from forming the specular effect. Of course, the functional structure  50  may be a structure which extracts the light emitted from the light-emitting unit to increase the light extraction efficiency, which is used for improving the brightness of the display panel. During the actual preparation, a whole adhesive layer of the functional structure  50  may be coated on the base substrate  10  to cover various structures on the base substrate  10 , and the whole adhesive layer may be thinned through a thinning technique to expose the structures such as the bank structures on the base substrate  10 . In this process, the opening  400  enclosed by the bank structure  40  may be filled with the functional structure  50  by using the limiting function of the bank structure  40 . The first opening  401  is filled with the functional structure  50 . Essentially, the functional structure  50  is used for covering the redundant electrode unit  22 . In a specific form, part of the functional structures  50  in the first openings  401  are disposed on the side of the redundant electrode units  22  facing away from the base substrate  10 , that is, the part of the functional structures  50  are disposed on the redundant electrode units  22 . In addition, when a spacing exists between the redundant electrode unit  22  and the adjacent bank structure  40 , the part of the functional structures  50  filling the first opening  401  may extend to the region of the spacing, that is, the part of the functional structures  50  filling the first opening  401  may directly cover the base substrate  10  in the region of the spacing. In addition, only part of the first openings  401  are filled with the functional structures  50 . The main reason is that it is necessary to electrically connect a new light-emitting unit on a corresponding redundant electrode unit  22  when the first light-emitting unit  31  is abnormal, and in this case, the functional structure  50  does not exist in a first opening  401  in which such redundant electrode unit  22  is disposed. 
     It is to be understood that when the functional structure  50  is made of a light-absorbing material such as a black adhesive, and the functional structure  50  fills the first opening  401  so that the functional structure  50  covers the redundant electrode unit  22 , the functional structure  50  may be used for preventing the external light being incident onto the redundant electrode unit  22  and preventing reflected light formed on the redundant electrode unit  22  from being emitted to the outside, thereby solving the issue that the redundant electrode unit  22  reflects light. When the functional structure  50  is made of a material having relatively high transmittance such as a white adhesive, the functional structure  50  may be used for reflecting light incident laterally into the functional structure  50  so that light emitted laterally from the light-emitting unit can also be reflected by the functional structure to be emitted to the outside, thereby increasing the amount of light emitted from the light-emitting unit and increasing the display brightness of the display panel. Of course, in the embodiment of the present disclosure, the functional structure  50  may be made of a material having a certain light transmission ability and a certain reflection-reducing ability, for example, a gray adhesive. The functional structure  50  can have the functions of reducing the light reflected by the redundant electrode unit and increasing the light emitted from the light-emitting unit, thereby improving the display effect of the display panel on the whole. 
     The black adhesive, the white adhesive, and the gray adhesive involved in the material selection for the preceding functional structure  50  may be silica gel, acrylic acid, or an epoxy-based material. Black or TiO particles are doped in the material and the doping ratio of the black or TiO particles is controlled so that a black, white, or gray effect can be achieved. Here, the adhesive is essentially a film material, which has good fluidity at medium and high temperatures (lower than 100° C.) and is polymerized at high temperatures (higher than 150° C.) to become a solid. Therefore, during the actual preparation, it is necessary to make the film material adhere on the base substrate through an adhering technique for optical adhesives, the film material is heated to the medium and high temperatures and then fills the bank structure  40 , and afterwards the film material is baked at the high temperatures (higher than 150° C.) for 1 to 2 hours so that the film material loses viscosity and is completely polymerized to become the solid so that the curing is achieved. 
     For the display panel provided by the preceding embodiment, the present disclosure further provides a preparation method of the display panel.  FIG.  4    is a flowchart of a preparation method of a display panel according to an embodiment of the present disclosure.  FIG.  5    is a structural flowchart of the preparation method of the display panel shown in  FIG.  4   . Referring to  FIGS.  4  and  5   , the preparation method may include the steps described below. 
     In S 110 , a base substrate is provided. 
     Referring to figure a) in  FIG.  5   , as described above, the base substrate  10  may be the flexible substrate or the rigid substrate, which is not limited here. It is to be understood by those skilled in the art that the base substrate  10  here is not a simple substrate structure, and a pixel circuit structure for driving a light-emitting unit to emit light is also disposed thereon. 
     In S 120 , electrode units are formed on a side of the base substrate, where the electrode unit includes main electrode units and redundant electrode units. 
     Referring to figure b) in  FIG.  5   , the electrode units  20  here may be directly formed with a mask through a deposition technique. Alternatively, a whole electrode layer may be prepared, and then the electrode units  20  may be formed through a patterning technique. In an embodiment, the deposition technique may be thermal evaporation, magnetron sputtering, chemical vapor deposition, or the like, and the patterning technique may be the photolithography technique or the like. The electrode unit is generally made of a silver, aluminum, or alloy material, which is not limited here. 
     In S 130 , a first light-emitting element is electrically connected to a main electrode unit. 
     Referring to figure c) in  FIG.  5   , as described above, the first light-emitting unit  31  may be the mini-LED, the micro-LED, the nano-LED, or the like. Here, the first light-emitting unit  31  is electrically connected to the main electrode unit  21 , which is essentially the process of bonding the LED unit on the main electrode unit  21 . In an embodiment, it may be the process in which an electrode of the LED and an electrode in the main electrode unit  21  are correspondingly soldered to each other with cooled hot-melt solder. 
     In S 140 , bank structures and openings disposed among the bank structures are formed on the base substrate, where the openings include a first opening, and the redundant electrode unit is disposed in the first opening. 
     Referring to figure e) in  FIG.  5   , actually, a whole layer of a bank structure adhesive is coated and etched and then developed through the patterning technique such as the photolithography technique, and a cured region is retained so that the bank structures  40  here are formed. It is to be understood that the openings  400  may be formed synchronously during the etching process, and the redundant electrode units  22  are exposed in part of openings  400 , that is, the first openings  401 . 
     In S 150 , functional structures are formed, where part of the first openings are filled with functional structures, and the functional structures are at least partially disposed on a side of the redundant electrode units facing away from the base substrate. 
     Referring to figure h) in  FIG.  5   , here, the specific preparation process of the functional structures  50  is as described above. The details are not repeated here. It is to be further added that the adhesive may still cover the bank structures  40  after the whole adhesive layer adheres through the adhering technique for optical adhesives and is heated to make the adhesive layer flow and fill the first opening  401 . Therefore, after the adhesive is baked at the high temperatures and cured, it is still necessary to thin the adhesive layer to expose the bank structure  40 , which will be described in detail later. 
     According to the technical schemes in the embodiments of the present disclosure, the base substrate, the electrode units, the first light-emitting units, the bank structures, and the functional structures are disposed in the display panel, where the electrode units are disposed on the side of the base substrate and include the main electrode units and the redundant electrode units; the first light-emitting unit is electrically connected to the main electrode unit; the openings are formed among the bank structures and include the first opening, where the redundant electrode unit is disposed in the first opening; and the first opening is filled with part of the functional structures, and the functional structures are at least partially disposed on the side of the redundant electrode units facing away from the base substrate. The bank structure may be used for limiting the functional structure so that the functional structure covers the redundant electrode unit. According to the embodiments of the present disclosure, the issue that the redundant electrode exposed in the existing display panel has relatively high reflectivity so as to influence the display effect can be solved. The reflection of the redundant electrode unit can be reduced with the functional structure, thereby preventing the redundant electrode unit from reflecting the excessive light to form the specular effect, and thus a display quality can be improved. Alternatively, the light extraction efficiency of the light-emitting unit can be increased with the functional structure, thereby improving the display brightness of the display panel and also helping reduce the power consumption of the display panel. 
     With continued reference to  FIGS.  1  to  3   , the display panel further includes a second light-emitting unit  32  and a first encapsulation structure  61 , where the openings  400  further include a second opening  402 , the second light-emitting unit  32  is disposed in the second opening  402 , and the first encapsulation structure  61  fills the second opening  402  and is at least partially disposed on a side of the second light-emitting unit  32  facing away from the base substrate  10 . 
     When part of first light-emitting units  31  emit light abnormally, second light-emitting units  32  are essentially repair light-emitting units provided for the abnormal first light-emitting units  31 . From a simple point of view, the two types of light-emitting units essentially have the same structure and function. Main differences between the two types of light-emitting units are that their positions designed in the display panel are different and the second light-emitting unit  32  is a substitute for the first light-emitting unit  31 . Similarly, the second light-emitting unit  32  may be the mini-LED, the micro-LED, the nano-LED, or the like, which is not limited here. In addition, a pixel circuit is also disposed on the base substrate  10  for the redundant electrode unit  22 . The pixel circuit is electrically connected to the second light-emitting unit  32  through the redundant electrode unit  22  so that the pixel circuit can drive the second light-emitting unit  32  to emit light. 
     In the embodiment of the present disclosure, the first encapsulation structure  61  is further disposed in the display panel. The first encapsulation structure  61  is a structure which separately encapsulates the second light-emitting unit  32  after the second light-emitting unit  32  is formed. It is to be emphasized that the bank structure  40  in the embodiment of the present disclosure limits a region in which the redundant electrode unit  22  is disposed and at the same time, the bank structure  40  also limits a region in which the second light-emitting unit  32  electrically connected to the redundant electrode unit  22  is disposed. Another important function of the bank structure  40  is to assist, with the limiting function, in the formation of the first encapsulation structure  61  when the second light-emitting unit  32  is encapsulated. Thus, it can be seen that the first encapsulation structure  61  actually is a structure filling the opening  400  enclosed by the bank structure  400  where the second light-emitting element  32  is disposed, that is, the second opening  402 , so as to protect the second light-emitting unit  32  in the second opening  402 . Further, in detail, part of the first encapsulation structure  61  is essentially disposed on the side of the second light-emitting unit  32  facing away from the base substrate  10 , that is, the part of the first encapsulation structure  61  is on the second light-emitting unit  32 . In addition, when a spacing exists between the second light-emitting unit  32  and the adjacent bank structure  40 , the part of the first encapsulation structure  61  filling the second opening  402  extends to the region of the spacing, that is, the part of the first encapsulation structure  61  in the second opening  402  directly covers the base substrate  10  in the region of the spacing. 
     In addition, it is to be further noted that since the functional structure  50  fills the first opening  401  and the first encapsulation structure  61  fills the second opening  402 , it is necessary to define at least the position of the first opening  401  or the position of the second opening  402  when the functional structure  50  and the first encapsulation structure  61  are prepared. During the actual preparation, optionally, the position of the second opening  402  is determined according to the second light-emitting unit  32  in the embodiment of the present disclosure, and the first encapsulation structure  61  precisely fills the second opening  402  through a printing technique. 
     Thus, it can be seen that the preparation method of the display panel provided by the present disclosure may further include the steps of forming the second light-emitting unit and the first encapsulation structure. In an embodiment, with continued reference to  FIGS.  4  and  5   , after step S 130  and before step S 150 , the preceding preparation method may further include the steps described below. 
     In S 141 , second light-emitting units are electrically connected to part of the redundant electrode units, where the openings further include the second openings, and the second light-emitting units are respectively disposed in the second openings. 
     Referring to figure f) in  FIG.  5   , as described above, the second light-emitting unit  32  may also be the mini-LED, the micro-LED, the nano-LED, or the like. Here, the second light-emitting units  32  are electrically connected to the part of the redundant electrode units  22 , which may also be understood as the process of bonding the LED units on the redundant electrode units  22 . In an embodiment, it may also be the process in which the electrode of the LED and the electrode in the redundant electrode unit  21  are correspondingly soldered with the cooled hot-melt solder. 
     Further, based on the preceding preparation method, the following step needs to be provided before step S 141 . 
     In S 1401 , a failed first light-emitting unit is detected and a position of a main electrode unit of the failed first light-emitting unit is determined. 
     It is to be understood that the second light-emitting unit  32  is essentially the substitute for the failed first light-emitting unit  31 . Therefore, before the second light-emitting units  32  are electrically connected to the part of the redundant electrode units  22 , it is necessary to determine positions of the part of the redundant electrode units  22  first, that is, it is necessary to detect positions of the failed first light-emitting units  31  and then to determine, according to the positions of the failed first light-emitting units  31 , the positions of the redundant electrode units  22  which need to be electrically connected to the second light-emitting units  32 . 
     Thus, in this case, step S 141  may be refined as: in S 1411 , the second light-emitting element  32  is electrically connected to the redundant electrode unit  22  corresponding to and adjacent to the main electrode unit  21  of the failed first light-emitting unit  31 . 
     Further, the following step may be included after the preceding step S 141 . 
     In S 142 , the second opening is filled with the first encapsulation structure, where the first encapsulation structure is at least partially disposed on a side of the second light-emitting unit facing away from the base substrate. 
     Referring to figure g) in  FIG.  5   , in this step, the process of forming the first encapsulation structure  61  is essentially the process of precisely filling the second opening  402  with the first encapsulation structure  61  on the basis that the second opening  402  has been known. During the actual preparation, for the first encapsulation structure  61 , a transparent resin material may be used for filling the second opening  402  enclosed by the bank structure  40 , and then the transparent resin material is cured with ultraviolet light, thereby implementing the encapsulation of the second light-emitting unit  32  in the second opening  402 . 
     Thus, this step S 142  may also be refined so that two sub-steps described below are obtained. 
     In S 1421 , it is determined that the opening enclosed by the bank structure corresponding to the redundant electrode unit electrically connected to the second light-emitting unit is the second opening. 
     In S 1422 , the second opening is filled with the first encapsulation structure through printing technique. 
     Here, the printing technique refers to that the position of the redundant electrode unit  22  to which the second light-emitting unit  32  is bonded is scanned with a high-precision printing device, that is, the position of the second opening  402  where the second light-emitting unit  32  is disposed is determined first through the scan, then the transparent resin is printed in the second opening  402 , and finally the transparent resin in the second opening  402  is cured through the ultraviolet light so that the stable first encapsulation structure  61  is formed. 
     It is to be understood that the failure of the first light-emitting unit  31  may occur at a certain probability after a batch transfer of the first light-emitting units  31  is completed and the first light-emitting units  31  are electrically connected to main electrode units  21 . In addition, since the failed first light-emitting unit  31  is random, the position of the redundant electrode unit  22  which needs to be electrically connected to the second light-emitting unit  32 , that is, the position of the redundant electrode unit which needs to perform a repair, is unfixed. After the electrical connection to the second light-emitting unit  32 , that is, the repair, is completed, though the position of the repair second light-emitting unit  32  has been determined, a preparation technique which needs the mask, for example, nanoimprint, is also not applicable when the functional structure  50  covers a redundant electrode unit  22  which is not connected to a second light-emitting unit  32 . The reason is that the second light-emitting unit  32  has different positions on different panels, an opening is disposed in the mask according to the position of a redundant electrode unit  22  which is on a certain panel and not connected to a second light-emitting unit  32 , and the mask is only applicable to this single panel but not applicable to another panel when the functional structure  50  covering the redundant unit  22  is manufactured. Therefore, the process step of forming the functional structure  50  through the preparation technique which needs the mask is not applicable to industrial batch production. 
     However, according to the preparation method provided by the embodiment of the present disclosure, the determined second light-emitting unit  32  on each display panel is precisely printed through the printing technique so that the encapsulation structure is formed. During the actual preparation, the display panel is scanned to determine the position of the second light-emitting unit  32 , and then the second light-emitting unit  32  is printed and encapsulated. After the encapsulation of the second light-emitting unit  32  is completed, the whole base substrate  10  is coated with a functional structure adhesive layer so that the functional structure adhesive layer fills the opening  400  corresponding to the redundant electrode unit  22  which is not connected to the second light-emitting unit  32 . With this technical process, not only can the second light-emitting unit  32  be effectively encapsulated to avoid external damage to the second light-emitting unit  32  and the service life of the second light-emitting unit  32  be ensured, but also the second light-emitting 32 having the random position can be precisely encapsulated and the functional structure  50  covers the redundant electrode unit  22  which is not connected to the second light-emitting unit  32 . The whole technical process is more free and flexible and can meet the requirement of industrial batch production. 
     It is to be noted that according to the example in the preceding embodiment, the second light-emitting unit is electrically connected to the redundant electrode unit  22  in the second opening  402  after a second encapsulation structure is formed, that is, the repair is performed with the second light-emitting unit  32  after the encapsulation of the first light-emitting unit  31  is completed. However, since the second encapsulation structure  62  and the bank structure  40  are formed synchronously during the actual preparation, bonding the second light-emitting unit  32  on the redundant electrode unit  22  provided with the bank structure  40  may be limited by the bank structure  40 , thereby influencing a bonding effect. Based on this, in the embodiment of the present disclosure, it may be considered that the repair after the encapsulation is performed in the manner of a laser transfer, thereby avoiding the influence of the bank structure  40  on bonding the second light-emitting unit  32 . 
     In other embodiments of the present disclosure, optionally, the failed first light-emitting unit is determined before the first light-emitting unit is encapsulated, the repair is performed with the second light-emitting unit  32 , and finally the first light-emitting unit  31  is encapsulated and the second light-emitting unit  32  is encapsulated. In conclusion, the sequence of the step of encapsulating the first light-emitting unit  31  and the step of performing the repair with the second light-emitting unit  32  is not limited in the embodiment of the present disclosure, and those skilled in the art may perform selection and design according to actual requirements. 
     Based on the actual preparation technique of the first encapsulation structure, the first encapsulation structure may be designed to have a special shape in the embodiment of the present disclosure, which is described below. With continued reference to  FIG.  2   , the first encapsulation structure  61  includes a top surface  610 , where the top surface  610  is disposed, along a direction perpendicular to a plane in which the base substrate  10  is located, on a side of the first encapsulation structure  61  facing away from the base substrate  10 ; and the top surface  610  is an arc surface and protrudes toward a direction away from the base substrate  10 . 
     During the actual preparation, for the first encapsulation structure  61 , a flexible adhesive is first used for filling the second opening  402  to cover the second light-emitting unit  32 , and then the flexible adhesive is cured so that the first encapsulation structure  61  is formed to protect the second light-emitting unit  32 . In the embodiment of the present disclosure, to ensure the encapsulation effect of the first encapsulation structure  61 , the second opening  402  is generally completely filled with the flexible adhesive. In addition, since light emitted from the second light-emitting unit  32  needs to be emitted out through the first encapsulation structure  61 , in an embodiment, the first encapsulation structure  61  is optionally provided with the top surface  610  which is a protruding arc surface. During the preparation, the cured first encapsulation structure  61  has a relatively hard material, and when the functional structure is thinned, the thinning technique thereof has less action on the cured first encapsulation structure  61  so that the protruding arc surface formed by curing the first encapsulation structure  61  can be retained. In a specific form, the top surface  610  is disposed on the side of the first encapsulation structure  61  facing away from the base substrate  10 , that is, the upper surface of the first encapsulation structure  61 . The top surface  610  is the arc surface, and the arc surface  610  protrudes towards the direction away from the base substrate  10 , that is, the arc surface  610  protrudes upward. Based on this design, optionally, the flexible adhesive fills relatively in excess the second opening  402  during the actual preparation to form the preceding protruding arc surface. The protruding arc surface on the first encapsulation structure  61  can function like a convex lens, and the light emitted from the second light-emitting unit  32  inside the first encapsulation structure  61  can be focused and emitted upward, thereby ensuring the light extraction efficiency of the second light-emitting unit  32 . 
     With continued reference to  FIG.  2   , in a direction perpendicular to the base substrate  10 , a height difference between the top surface  610  and the surface of a side of the bank structure  40  facing away from the base substrate  10  is less than or equal to 6 μm. The surface of the side of the bank structure  40  facing away from the base substrate  10  refers to the upper surface of the bank structure  40 . The height of the upper surface of the bank structure  40  with respect to the base substrate  10  is H1 as shown in  FIG.  2   , and the height of the top surface  610  on the base substrate  10  is H2 as shown in  FIG.  2   , where H2−H1&lt;6 μm, which can ensure that the first encapsulation structure  61  has the protruding arc surface with a certain height, that is, the protruding arc surface has a certain radian. The protruding arc surface is used for implementing the function of effectively focusing the light so that the light emitted from the second light-emitting unit  32  in the first encapsulation structure  61  is emitted to the outside as much as possible. 
     Considering that light-emitting units of different colors may have inconsistent light emission efficiencies, in the embodiment of the present disclosure, light emission effects of second light-emitting units of different colors are optionally balanced when the second light-emitting units are encapsulated. With continued reference to  FIG.  2   , optionally, the second light-emitting unit  32  includes a first-color light-emitting unit  321  and a second-color light-emitting unit  322 ; and the first encapsulation structure  61  includes a first encapsulation sub-structure  611  and a second encapsulation sub-structure  612 . The first encapsulation sub-structure  611  corresponds to the first-color light-emitting unit  321 , and the second encapsulation sub-structure  612  corresponds to the second-color light-emitting unit  322 ; and the area of an orthographic projection of the top surface of the first encapsulation sub-structure  611  on the base substrate  10  is smaller than the area of an orthographic projection of the top surface of the second encapsulation sub-structure  612  on the base substrate  10 . A wavelength of light emitted from the first-color light-emitting unit  321  is greater than a wavelength of light emitted from the second-color light-emitting unit  322 . 
     Here, the first-color light-emitting unit  321  and the second-color light-emitting unit  322  may be understood as a red light-emitting unit and a green light-emitting unit, respectively. In comparison, the red light-emitting unit has a relatively low light emission efficiency. Of course, this embodiment is also applicable to other light-emitting units of any two colors having different light emission efficiencies such as a green light-emitting unit and a blue light-emitting unit. 
     Based on this, in the embodiment of the present disclosure, the first encapsulation structure  61  of the first-color light-emitting unit  321  and the first encapsulation structure  61  of the second-color light-emitting unit  322  are set different from each other, the object of which is to use the different first encapsulation structures  61  for balancing the light emitted from the light-emitting units of the two colors. In an embodiment, the first-color light-emitting unit  321  corresponds to the first encapsulation sub-structure  611 , which refers to that the first encapsulation sub-structure  611  fills the second opening  402  in which the first-color light-emitting unit  321  is disposed, and the first encapsulation sub-structure  611  is at least partially disposed on a side of the first-color light-emitting unit  321  facing away from the base substrate  10 . Similarly, the second-color light-emitting unit  322  corresponds to the second encapsulation sub-structure  612 , which refers to that the second encapsulation sub-structure  612  fills the second opening  402  in which the second-color light-emitting unit  322  is disposed, and the second encapsulation sub-structure  612  is at least partially disposed on a side of the second-color light-emitting unit  322  facing away from the base substrate  10 . In this embodiment, the area of the orthographic projection of the top surface of the first encapsulation sub-structure  611  on the base substrate  10  is smaller than the area of the orthographic projection of the top surface of the second encapsulation sub-structure  612  on the base substrate  10 . Essentially, the area of the orthographic projection of the top surface of the first encapsulation sub-structure  611  is reduced so that the top surface of the first encapsulation sub-structure  611  protrudes at a more apparent radian among the two encapsulation sub-structures with the same height. The first-color light-emitting unit  321  can implement, through the top surface protruding more apparently, the function of focusing the light more efficiently so that the light emitted from the first-color light-emitting unit  321  in the first encapsulation sub-structure  611  is more emitted to the outside. Thus, the relatively low light emission efficiency of the first-color light-emitting unit  321  is compensated, the amount of light emitted from the light-emitting units of the two colors is balanced, and the brightness of the light-emitting units having the different light emission efficiencies is equalized, thereby ensuring the display effect. 
       FIG.  6    is a sectional view of another display panel according to an embodiment of the present disclosure. Referring to  FIG.  6   , in another embodiment of the present disclosure, optionally, the second light-emitting unit  32  includes the first-color light-emitting unit  321  and the second-color light-emitting unit  322 ; the first encapsulation structure  61  includes the first encapsulation sub-structure  611  and the second encapsulation sub-structure  612 . The first encapsulation sub-structure  611  corresponds to the first-color light-emitting unit  321 , and the second encapsulation sub-structure  612  corresponds to the second-color light-emitting unit  322 ; and a sectional shape of the top surface of the first encapsulation sub-structure  611  on a first plane is a first arc, and a sectional shape of the top surface of the second encapsulation sub-structure  612  on the first plane is a second arc, where a radius of curvature r1 corresponding to the first arc is smaller than a radius of curvature r2 corresponding to the second arc, and the first plane is perpendicular to the base substrate  10 . 
     As described above, since the top surface  610  of the first encapsulation structure  61  is the protruding arc surface, an arc is formed in a section of the top surface of the first encapsulation sub-structure  611  on the plane perpendicular to the base substrate  10 , that is, the first plane. In the embodiment of the present disclosure, the object of setting the top surface of the encapsulation structure to be the protruding arc surface is to cause the encapsulation structure to function like the convex lens. In addition, it is to be known by those skilled in the art that the higher curvature the surface of the convex lens has, the shorter the focal length thereof is, and the higher the focusing ability thereof is. Therefore, the curvature of the top surface of the first encapsulation sub-structure  611  corresponding to the first-color light-emitting unit  321  and the curvature of the top surface of the second encapsulation sub-structure  612  respectively corresponding to the second-color light-emitting unit  322  are distinguished so that the focusing abilities of the two encapsulation sub-structures are changed. Thus, the light extraction efficiencies of the first-color light-emitting unit  321  and the second-color light-emitting unit  322  can be further balanced. In an embodiment, the radius of curvature r1 of the first arc corresponding to the top surface of the first encapsulation sub-structure  611  is set smaller than the radius of curvature r2 of the second arc corresponding to the top surface of the second encapsulation sub-structure  612 . Essentially, the curvature of the top surface of the first encapsulation sub-structure  611  is relatively increased so that the focusing ability of the first encapsulation sub-structure  611  is relatively increased. Thus, for the light emitted from the first-color light-emitting unit  321  having the relatively low light emission efficiency in the first encapsulation sub-structure  611 , the brightness of the light-emitting units having the different light emission efficiencies is further equalized, thereby ensuring the display effect. 
     With continued reference to  FIGS.  1  and  3   , the display panel further includes the second encapsulation structure  62  at least partially disposed on a side of the first light-emitting unit  31  facing away from the base substrate  10 , where an orthographic projection of the second encapsulation structure  62  on the base substrate  10  covers an orthographic projection of the first light-emitting unit  31  on the base substrate  10 , and a distance from the surface of a side of the second encapsulation structure  62  facing away from the base substrate  10  to the base substrate  10  is equal to a distance from the surface of the side of the bank structure  40  facing away from the base substrate  10  to the base substrate  10 . 
     Here, second encapsulation structures  62  are encapsulation structures formed through the batch encapsulation of the first light-emitting units  31  after the first light-emitting units  31  are transferred in batch and bonded on the corresponding main electrode units  21 . In an embodiment, after the first light-emitting units  31  are transferred in batch and bonded on the corresponding main electrode units  21 , a whole encapsulation adhesive layer may be coated on the base substrate  10 , and the encapsulation adhesive layer is patterned through the photolithography technique, thereby forming an independent second encapsulation structure  62  for each of the first light-emitting units  31 . 
     To ensure a good encapsulation effect, the second encapsulation structure  62  needs to cover the first light-emitting unit  31  completely, and from the perspective of projection, the orthographic projection of the second encapsulation structure  62  on the base substrate  10  covers the orthographic projection of the first light-emitting unit  31  on the base substrate  10 . In addition, part of the second encapsulation structure  62  may be disposed on the first light-emitting unit  31 , that is, the part of the second encapsulation structure  62  may be disposed on the side of the first light-emitting unit  31  facing away from the base substrate  10 . In addition, part of the second encapsulation structure  62  may extend to a peripheral region of the first light-emitting unit  31  and directly cover the base substrate  10  in the peripheral region of the first light-emitting unit  31 . 
     Based on this, the preparation method provided by the preceding embodiment may further include the process of preparing the second encapsulation structure. In an embodiment, with continued reference to  FIGS.  4  and  5   , after step S 130 , the following steps may further be included. 
     In S 131 , the second encapsulation structure is formed, where the second encapsulation structure is at least partially disposed on the side of the first light-emitting unit facing away from the base substrate, and the orthographic projection of the second encapsulation structure on the base substrate covers the orthographic projection of the first light-emitting unit on the base substrate. 
     Referring to figure d) in  FIG.  5   , the preparation technique of the second encapsulation structure  62  is as described above. The details are not repeated here. 
     However, the present disclosure further provides a simpler manner to prepare the bank structure and the second encapsulation structure.  FIG.  7    is a flowchart of another preparation method of a display panel according to the embodiment of the present disclosure.  FIG.  8    is a structural flowchart of the preparation method of the display panel shown in  FIG.  7   . Based on the preparation method provided by the preceding embodiment, comparing  FIGS.  4  and  5    with  FIGS.  7  and  8   , step S 131  and step S 140  may be simultaneously performed for the preparation and formation in the same process step, that is, the preceding step S 131  and step S 140  may be replaced with the two sub-steps described below. 
     In S 1310 , an encapsulation layer is formed on the base substrate, where the encapsulation layer is at least partially disposed on the side of the first light-emitting unit facing away from the base substrate and a side of the electrode unit facing away from the base substrate, and an orthographic projection of the encapsulation layer on the base substrate covers the orthographic projection of the first light-emitting unit on the base substrate and an orthographic projection of the electrode unit on the base substrate. 
     In S 1400 , the encapsulation layer is patterned through the photolithography technique so that the second encapsulation structure and the bank structure are formed. 
     Based on this, referring to  FIG.  7   , figure d) in  FIG.  7    shows the process of forming the encapsulation layer  60  on the base substrate and shows the process of coating the whole adhesive layer. Figure e) in  FIG.  7    shows the process in which the encapsulation layer  60  is patterned through the photolithography technique according to the positions of the main electrode units  21  and the positions of the redundant electrode units  22  to synchronously form the second encapsulation structures  62  and the bank structures  40 . That is, the second encapsulation structures  62  and the bank structures  40  are synchronously formed in the same step, and there is no sequence for forming the second encapsulation structures  62  and the bank structures  40 . 
     It is to be noted that the second encapsulation structures  62  and the bank structures  40  are essentially formed in two steps during the preparation process as shown in  FIGS.  4  and  5   , and the implementation may be performed through the adhesive layer coating technique and the photolithography patterning technique. Apparently, for the process steps of separately forming the second encapsulation structure  62  and the bank structure  40 , it is possible to independently design the shapes, materials, and the like of the second encapsulation structure  62  and the bank structure  40  so as to use the second encapsulation structure  62  and the bank structure  40  for separately performing an independent adjustment in properties such as light emission of the first light-emitting unit  31  and the second light-emitting unit  32  so as to avoid mutual influence. During the preparation process shown in  FIGS.  7  and  8   , the second encapsulation structures  62  and the bank structures  40  are formed synchronously by the same process step, which can save the steps and masks and reduce time and material costs. 
     It is to be emphasized that the bank structures  40  and the second encapsulation structures  62  need to be exposed by thinning since the functional structures  50  is prepared through the technique of coating and thinning the whole layer in the embodiment of the present disclosure. Since the thinning technique has an action on the whole panel, the bank structures  40  and the second encapsulation structures  62  made of a relatively soft material are simultaneously thinned. Therefore, in an actual display panel, the upper surface of the bank structure  40  and the upper surface of the second encapsulation structure  62  remain at the same height on the base substrate  10 , that is, the distance from the surface of the side of the second encapsulation structure  62  facing away from the base substrate  10  to the base substrate  10  is equal to the distance from the surface of the side of the bank structure  40  facing away from the base substrate  10  to the base substrate  10 . 
     Thus, in the preparation method provided by the embodiment of the present disclosure, step S 150  may include the steps described below. 
     In S 151 , the functional structure adhesive layer is attached, in a heated vacuum environment, to a side of the base substrate on which the bank structure is disposed, where an orthographic projection of the functional structure adhesive layer on the base substrate covers orthographic projections of the bank structures, the opening between bank structures, and the first encapsulation structures on the base substrate. 
     Here, for the step of making the adhesive layer adhere, reference may be made to the preceding description. The details are not repeated here. 
     In S 152 , the functional structure adhesive layer is thinned through an ash technique or a wet etching technique so that the functional structure is formed. 
     In an embodiment, step S 152  may be the process in which the ash is performed on the whole surface or the whole is immersed in a solution for performing the wet etching. An excessive functional structure adhesive material layer covering the bank structure  40  may be removed through the ash and the wet etching and the first encapsulation structure  61  and the second encapsulation structure  62  may be exposed at the same time, thereby ensuring the light emission of the light-emitting units inside the first encapsulation structure  61  and the second encapsulation structure  62 . 
     Of course, considering an error in the thinning technique and a rough surface formed in the thinning technique, there may be certain errors in the height of the upper surface of the second encapsulation structure  62  and the height of the upper surface of the bank structure  40 , or there may be certain errors in the height of a local region on the upper surface of the second encapsulation structure  62  and the height of a local region on the upper surface of the bank structure  40 . It is defined here that the upper surface of the bank structure  40  and the upper surface of the second encapsulation structure  62  may be considered to remain at the same height on the base substrate  10  if the range of errors is within 30%. 
     It is also to be noted that the second encapsulation structure  62  needs to transmit the light emitted from the first light-emitting unit  31  inside the second encapsulation structure  62  to the outside, and the first encapsulation structure  61  needs to transmit the light emitted from the second light-emitting unit  32  inside the first encapsulation structure  61  to the outside. To avoid differences in the light emission between the two light-emitting units due to different encapsulation structures, optionally, the first encapsulation structure  61  and the second encapsulation structure  62  may be made of materials having the same or similar refractive index, thereby eliminating differences in light types between the two light-emitting units. 
     Further,  FIG.  9    is a partial enlarged view of dashed box a of the display panel shown in  FIG.  2   , and  FIG.  10    is a partial enlarged view of dashed box b of the display panel shown in  FIG.  3   . Referring to  FIGS.  9  and  10   , based on the preceding thinning technique, in a display panel actually formed, at least part of the surface of the side of the bank structure  40  facing away from the base substrate  10  is a rough concave-convex surface and at least part of the surface of a side of the second encapsulation structure  62  facing away from the base substrate  10  is a rough concave-convex surface. 
     The bank structures  40 , the second encapsulation layers  62 , and the first encapsulation structures  61  are exposed while the functional structure adhesive layer is thinned through the thinning technique. In addition, the upper surfaces of the bank structures  40 , the second encapsulation structures  62 , and the first encapsulation structures  61  which are exposed, that is, the surfaces of the sides facing away from the base substrate  10 , are roughened, thereby implementing diffuse reflection, helping avoid specular reflection after the external light is incident on the display panel, and further reducing the reflectivity of the display panel. For the first encapsulation structure  61 , the roughened surface also helps reduce the probability of the total reflection of the light in the first encapsulation structure  61  at an interface, thereby increasing the light emitted from the internal light-emitting unit to the outside and improving the light extraction efficiency of the internal light-emitting unit. 
     Further, as described in the preceding steps S 1310  and S 1400 , in the embodiment of the present disclosure, the bank structures  40  and the second encapsulation structures  62  described above may optionally be made of the same material in the same technique, that is, the bank structures  40  and the second encapsulation structures  62  are the same material. During the preparation of the second encapsulation structures  62  as described above, the bank structures  40  may be formed. In an embodiment, the whole encapsulation adhesive layer is coated on the base substrate  10 , and the encapsulation adhesive layer is patterned through the etching technique, and an opening pattern of the second encapsulation structures  62  and an opening pattern of the bank structures  40  are designed in the mask used for the patterning, the whole encapsulation adhesive layer may be etched with the mask to form the second encapsulation structures  62  covering the first light-emitting units  31  and the bank structures  40  enclosing the redundant electrode units  22 . 
     Further, with continued reference to  FIG.  3   , in this display panel, the second encapsulation structure  62  includes a third side surface  623  and a first surface  621 , the third side surface  623  is disposed on a side of the second encapsulation structure  62  along a first direction  1 , and the first direction  1  is parallel to a plane in which the base substrate  10  is located; in a direction perpendicular to the plane in which the base substrate  10  is located, the first surface  621  is disposed on a side of the second encapsulation structure  62  facing away from the base substrate  10 ; and an included angle α3 between the third side surface  623  and the first surface  621  is a third included angle, where the third included angle α3 is an acute angle. 
     In the embodiment of the present disclosure, the encapsulation adhesive layer may be patterned through the photolithography technique when the second encapsulation structure is prepared, where negative photoresist is optionally used. It is to be known by those skilled in the art that the property of photoresist in an exposed region is changed and the photoresist is cured when the negative photoresist is used, the encapsulation adhesive layer in the cured region is retained during development, and the bottom of the cured region is etched more seriously than the top of the cured region due to the over-etching effect of a developer so that the retained encapsulation adhesive layer, that is, the second encapsulation structure  62 , has an inverted platform-like structure. Here, the third side surface  623  is essentially an inclined sidewall of the second encapsulation structure  62  as an inverted platform-like structure. The first surface  623  is essentially a relatively large-area bottom surface of the second encapsulation structure  62  as the inverted platform-like structure, which may also be understood as the upper surface of the inverted platform-like structure. Based on the actual preparation technique, the included angle between the third side surface  623  and the first surface  621  of the second encapsulation structure  62  in the embodiment of the present disclosure, that is, the third included angle α3, is essentially a top vertex angle of the inverted platform-like structure. The third included angle α3 is the acute angle, which indicates that the sidewall of the second encapsulation structure  62  inclines outward in the upward direction perpendicular to the base substrate  10 . That is, the upper surface of the second encapsulation structure  62  has a larger area than the lower surface of the second encapsulation structure  62 , which indicates that the second encapsulation structure  62  is the inverted platform-like structure. 
     Referring to a light path as shown in  FIG.  3   , it can be seen that the light emitted from the first light-emitting unit  31  is reflected upward by the third side surface  623  when incident on the sidewall, that is, the third side surface  623 , since the inverted platform-like second encapsulation structure  62  has the sidewall inclining outward. That is, the second encapsulation structure  62  is properly designed to make the second encapsulation structure  62  form the inverted platform-like structure so that the light emitted from the light-emitting unit encapsulated in the second encapsulation structure  62  can be emitted to the front of the display panel as much as possible by the inclined sidewall of the second encapsulation structure  62 , thereby improving the light extraction efficiency of the first light-emitting unit. 
     Similarly, considering that the light-emitting units of the different colors may have the inconsistent light emission efficiencies, the second encapsulation structure may optionally be designed differently in the embodiment of the present disclosure so that the first light-emitting units of the different colors have the relatively balanced light extraction efficiencies.  FIG.  11    is a sectional view of another display panel according to an embodiment of the present disclosure. Referring to  FIG.  11   , in another embodiment of the present disclosure, the first light-emitting unit  31  includes a third-color light-emitting unit  313  and a fourth-color light-emitting unit  314 ; and a wavelength of light emitted from the third-color light-emitting unit  313  is greater than a wavelength of light emitted from the fourth-color light-emitting unit  314 . A third included angle α3′ of the second encapsulation structure  62  on a side of the third-color light-emitting unit  313  facing away from the base substrate  10  is smaller than a third included angle α3″ of the second encapsulation structure  62  on a side of the fourth-color light-emitting unit  314  facing away from the base substrate  10 . 
     It can be seen from the preceding description that the third-color light-emitting unit  313  and the fourth-color light-emitting unit  314  here may be similarly understood as the red light-emitting unit and the green light-emitting unit, respectively. In comparison, the red light-emitting unit has the relatively low light emission efficiency. In this embodiment, the third included angle α3′ of the second encapsulation structure  62  covering the red light-emitting unit is set relatively small. Actually, the sidewall of the second encapsulation structure  62  is set more inclined, and the inclination angle is closer to 45 degrees. Referring to a light path shown in  FIG.  11   , it is to be understood that when the inclination degree of the sidewall is closer to 45 degrees, light emitted from the red light-emitting unit horizontally may be emitted to the upward direction perpendicular to the base substrate  10  through the sidewall. The sidewalls of the second encapsulation structures corresponding to the light-emitting units of the different colors are set to have the different inclination angles so that the light-emitting unit having the relatively low light emission efficiency can emit more light to the front of the display panel, thereby achieving the effects of equalizing the amount of light emitted from the light-emitting units of the different colors and reducing the brightness difference between the light-emitting units of the different colors. 
     Since the bank structure and the second encapsulation structure are actually made through the same technique, that is, the photolithography technique during the preparation, the bank structure may also have an inverted platform-like structure based on the same principle. In an embodiment,  FIG.  12    is a sectional view of the display panel shown in  FIG.  1    taken along CC′. Referring to  FIGS.  1  and  12   , the bank structure  40  includes a fourth side surface  414  and a second surface  422 , the fourth side surface  414  is disposed on a side of the bank structure  40  along the first direction  1 , and in the direction perpendicular to the plane in which the base substrate  10  is located, the second surface  422  is disposed on the side of the bank structure  40  facing away from the base substrate  10 ; and an included angle between the fourth side surface  414  and the second surface  422  is a fourth included angle α4, where the third included angle α3 is smaller than the fourth included angle α4, and the fourth angle α4 is the acute angle. The fourth side surface  414  is essentially an inclined sidewall of the bank structure  40  as the inverted platform-like structure. The second surface  422  is essentially a relatively large-area bottom surface of the bank structure  40  as the inverted platform-like structure, which may also be understood as the upper surface of the inverted platform-like structure. Similarly, the included angle between the fourth side surface  414  and the second surface  422  of the bank structure  40  here, that is, the fourth included angle α4, is essentially a top vertex angle of the inverted platform-like structure. The fourth included angle α4 is the acute angle, which indicates that the sidewall of the bank structure  40  inclines outward in the upward direction perpendicular to the base substrate  10 . That is, the upper surface of the bank structure  40  has a larger area than the lower surface of the bank structure  40 , which indicates that the bank structure  40  is the inverted platform-like structure. 
     In addition, since a spacing between adjacent second encapsulation structures  62  is larger than a spacing between adjacent bank structures  40 , an adhesive in a gap between the second encapsulation structures  62  with the relatively large spacing is over-etched more seriously during the development and the etching when the second encapsulation structures  62  and the bank structures  40  are prepared. That is, an etching solution etches more the bottom of the second encapsulation structure  62  so that the bottom surface of the second encapsulation structure  62  formed after the development finally has a smaller area than the bottom surface of the bank structure  40 . The sidewall of the second encapsulation structure  62  is relatively more inclined. As shown in  FIG.  9   , the third included angle α3 of the second encapsulation structure  62  is smaller than the fourth included angle α4 of the bank structure  40 . 
       FIG.  13    is a sectional view of another display panel according to an embodiment of the present disclosure. Referring to  FIGS.  1  and  13   , in another embodiment of the present disclosure, the first opening  401  may be set to include a first sub-opening  4011  and a second sub-opening  4012 , and a bank structure  40  includes a first side surface  411  facing away from the first sub-opening  4011  and another bank structure  40  includes a second side surface  412  facing away from the second sub-opening  4012 ; and an included angle between the first side surface  411  and the surface of the side of the bank structure  40  facing away from the base substrate  10  is a first included angle α1, and an included angle between the second side surface  412  and the surface of the side of the bank structure  40  facing away from the base substrate  10  is a second included angle α2, where one of the first included angle α1 and the second included angle α2 is greater than the other. 
     Here, the first opening  401  is set to include two types of sub-openings, which sets the bank structures  40  enclosing the two types of sun-opening different. In an embodiment, the side surface of the bank structure  40  facing away from the first sub-opening  4011 , that is, the first side surface  411 , refers to the side surface of the bank structure  40  facing away from the first sub-opening  4011  in a direction parallel to the base substrate  10 . Similarly, the side surface of the bank structure  40  facing away from the second sub-opening  4012 , that is, the second side surface  412 , refers to the side surface of the bank structure  40  facing away from the second sub-opening  4012  in the direction parallel to the base substrate  10 . Here, the included angle between the first side surface  411  and the surface of the side of the bank structure  40  facing away from the base substrate  10 , that is, the upper surface, is set to be the first included angle α1, and the included angle between the second side surface  412  and the surface of the side of the bank structure  40  facing away from the base substrate  10 , that is, the upper surface, is set to the second included angle α2, and one of the first included angle α1 and the second included angle α2 is set to be greater than the other. Essentially, the two side surfaces of the bank structures  40  are set to have the different inclination angles so that the light extraction efficiencies of the adjacent light-emitting units are adjusted through the reflection by the side surfaces, thereby meeting the requirement of the display panel for the light emission of the light-emitting units. 
     With continued reference to  FIGS.  1  and  13   , further, the redundant electrode units  22  includes a first redundant electrode unit  221  and a second redundant electrode unit  222 . The first redundant electrode unit  221  is disposed in the first sub-opening  4011 , and the second redundant electrode unit  222  is disposed in the second sub-opening  4012 ; the first light-emitting unit  31  includes the third-color light-emitting unit  313  and the fourth-color light-emitting unit  314 ; and the first redundant electrode unit  221  corresponds to a first pixel circuit (not shown in the figure), the second redundant electrode unit  222  corresponds to a second pixel circuit (not shown in the figure), the first pixel circuit drives the third-color light-emitting unit  313 , and the second pixel circuit drives the fourth-color light-emitting unit  314 . The first included angle α1 is smaller than the second included angle α2, and a wavelength of the light emitted from the third-color light-emitting unit  313  is greater than a wavelength of the light emitted from the fourth-color light-emitting unit  314 . 
     First, it is to be understood that the main electrode unit  21  is responsible for electrically connecting the pixel circuit to the main light-emitting unit and driving the first light-emitting unit to be bright through the pixel circuit. When the first light-emitting unit emits light abnormally, the redundant electrode unit  22 , as a standby electrode for the main electrode unit  21 , is bonded to a new light-emitting unit so that the pixel circuit is electrically connected to the main light-emitting unit, and the new pixel circuit is used for driving the new light-emitting unit to be bright. Thus, it is to be understood that one main electrode unit  21  and one redundant electrode unit  22  share the same pixel circuit, that is, correspond to the same pixel circuit. 
     In this embodiment, according to the light-emitting units of the two colors included in the first light-emitting unit, that is, the third-color light-emitting unit  313  and the fourth-color light-emitting unit  314 , the two pixel circuits corresponding to the third-color light-emitting unit  313  and the fourth-color light-emitting unit  314  are defined as the first pixel circuit and the second pixel circuit, respectively. Further, according to the first pixel circuit and the second pixel circuit, the two redundant electrode units  22  corresponding to the first pixel circuit and the second pixel circuit are defined as the first redundant electrode unit  221  and the second redundant electrode unit  222 , respectively. In this embodiment, the first sub-opening  4011  and the second sub-opening  4012  differ mainly in the redundant electrode units  22  therein. The first redundant electrode unit  221  is in the first sub-opening  4011 , and the second redundant electrode unit  222  is in the second sub-opening  4012 . The first redundant electrode unit  221  differs from the second redundant electrode unit  222  mainly in that the first light-emitting unit  31  corresponding to the first redundant electrode unit  221  as a standby electrode is different from the first light-emitting unit  31  corresponding to the second redundant electrode unit  222  as a standby electrode. 
     Based on the preceding logic, it can be seen that the first sub-opening  4011  actually corresponds to the third-color light-emitting unit  313  and the second sub-opening  4012  corresponds to the fourth-color light-emitting unit  314 . As described in the preceding embodiment, the third-color light-emitting unit  313  and the fourth-color light-emitting unit  314  may be understood as the red light-emitting unit and the green light-emitting unit, respectively. In comparison, the red light-emitting unit has the relatively low light emission efficiency. In this embodiment, the included angle between the first side surface  411  and the upper surface of the bank structure  40 , that is, the first included angle α1, is set relatively small for the red light-emitting unit while the included angle between the second side surface  412  and the upper surface of the bank structure  40 , that is, the second included angle α2, is set relatively large for the green light-emitting unit. Actually, the first side surface  411  is set to have a smaller inclination angle than the second side surface  412  such that the inclination angle of the first side surface  411  is closer to 45 degrees. Thus, the light emitted from the red light-emitting unit, that is, the third-color light-emitting unit  313 , is reflected by the first side surface  411  and more emitted in the upward direction perpendicular to the base substrate  10  so that the light-emitting unit having the relatively low light emission efficiency emits more light to the front of the display panel, thereby achieving the effects of equalizing the amount of light emitted from the light-emitting units of the different colors and reducing the brightness difference between the light-emitting units of the different colors. 
     It is to be noted that the second light-emitting units  32  may be disposed in the bank structures  40  corresponding to the first sub-opening  4011  and the second sub-opening  4012  here, or no second light-emitting units  32  may be disposed in the bank structures  40  corresponding to the first sub-opening  4011  and the second sub-opening  4012 . It is to be understood that a magnitude relationship between the first included angle α1 and the second included angle α2 is preset when the bank structures  40  are prepared so that when the second light-emitting unit  32  is disposed in the first sub-opening  4011  or the second sub-opening  4012  if the first light-emitting unit  31  fails, the inclined sidewall of the bank structure  40  can be used for reflecting the light emitted from the second light-emitting unit  32 . Thus, the light emitted from the second light-emitting unit  32  is more emitted to the front of the display panel, thereby improving the light extraction efficiency of the second light-emitting unit  32 . 
     With continued reference to  FIGS.  1  and  2   , optionally, at least two bank structures  40  are provided between adjacent redundant electrode units  22 , the opening  400  between the adjacent bank structures  40  includes a third opening  403 , and part of the functional structures  50  fill the third opening  403 . 
     Here, the at least two bank structures  40  are disposed between the adjacent redundant electrode units  22 . Thus, on the one hand, each redundant electrode unit  22  has an independent bank structure  40  around it, and on the other hand, the at least two bank structures  40  between the two adjacent redundant electrode units  22  may be filled to form the functional structure  50 . Here, the functional structure  50  in the third opening  403  is essentially disposed on the surface of the side of the base substrate  10  on which the electrode units are disposed, and the functional structure  50  directly covers the base substrate  10 . With this functional structure  50 , the light emitted from the second light-emitting unit  32  can be extracted when the second light-emitting unit  32  is bonded on the redundant electrode unit  22 . Thus, the light emitted from the second light-emitting unit  32  at a large angle is emitted to the outside to a certain extent, thereby improving the light extraction efficiency of the second light-emitting unit  32  and helping increase the brightness of the display panel. 
     With continued reference to  FIGS.  1  and  12   , optionally, the display panel further includes a fourth opening  404 , where at least one sidewall of the fourth opening  404  is the sidewall of the second encapsulation structure  62 , and the fourth opening  404  is filled with part of the functional structures  50 . 
     The at least one sidewall of the fourth opening  404  is the sidewall of the second encapsulation structure  62 , which actually refers to that a gap exists between the bank structure  40  and the second encapsulation structure  62  to form the fourth opening  404 . The functional structure  50  fills the gap between the bank structure  40  and the second encapsulation structure  62 , that is, the fourth opening  404 . Thus, the light emitted from the first light-emitting unit  31  at the large angle in the second encapsulation structure  62  can be extracted through the functional structure  50  so that the amount of light emitted from the first light-emitting unit  31  at the large angle can be increased and the light extraction efficiency of the first light-emitting unit  31  is improved to some extent, thereby helping increase the brightness of the display panel. 
       FIG.  14    is a structural diagram of another display panel according to an embodiment of the present disclosure.  FIG.  15    is a sectional view of the display panel shown in  FIG.  14    taken along DD′. Referring to  FIGS.  14  and  15   , in another embodiment of the present disclosure, optionally, one bank structure  40  is provided between the adjacent redundant electrode units  22 . In this case, the adjacent redundant electrode units  22  share one bank structure  40  and are separated by the bank structure  40 , and regions in which the redundant electrode units  22  are disposed are defined. According to this implementation, the number of bank structures  40  can be reduced, and a spacing between the bank structures  40  is relatively large. During the actual preparation, the mask used for the photolithography has a relatively few openings and the requirement for the accuracy of the opening is low, which is more convenient for the preparation. On the contrary, this embodiment is more applicable to a display panel with a height resolution, and a spacing between redundant electrode units in the display panel with the height resolution is relatively small. Therefore, it is more applicable to dispose one bank structure directly between adjacent redundant electrode units. 
       FIG.  16    is a sectional view of the display panel shown in  FIG.  14    taken along EE′. Referring to  FIGS.  14  and  16   , the display panel further includes a fifth opening  405 , where at least one sidewall of the fifth opening  405  is the sidewall of the second encapsulation structure  62 , at least one sidewall of the fifth opening  405  is the sidewall of the bank structure  40 , and part of the redundant electrode units  22  are disposed in the fifth opening  405 . 
     Here, the at least one sidewall of the fifth opening  405  is the sidewall of the second encapsulation structure  62 , and the at least one sidewall of the fifth opening  405  is the side wall of the bank structure  40 . Essentially, the second encapsulation structure  62  is also used as the bank structure  40  of the redundant electrode units  22  adjacent to the second encapsulation structure  62 . The second encapsulation structure  62 , in conjunction with another bank structure  40 , can limit a region in which the adjacent redundant electrode units  22  are disposed, which is convenient for filling with the functional structure or filling with the first encapsulation structure after the second light-emitting unit  32  is bonded on the redundant electrode unit  22 . 
     As described above, a material may be selected for the functional structure in the embodiment of the present disclosure according to the actually required function. In an embodiment, the functional structure  50  in the embodiment of the present disclosure may be made of a light-shielding material. In an embodiment, the light-shielding material may be a black adhesive having a thickness within 10 μm and transmittance of less than 6%. Alternatively, the functional structure  50  may be made of a light-reflecting material. In an embodiment, the light-reflecting material may be the white adhesive, and its reflectivity should be greater than 80%. In addition, the functional structure  50  may be made of the gray adhesive which implements the functions of reducing the reflection and increasing the light emission. The gray adhesive should have transmittance less than 30% and reflectivity greater than 50%. 
     When the functional structure  50  is made of the black adhesive, the transmittance is less than 6%, which indicates that the functional structure  50  has a great light absorption ability and can absorb light incident from the outside, thereby preventing the external light from being incident on the redundant electrode unit  22  to form the reflection and achieving the effect of reducing the reflection. When the functional structure  50  is made of the white adhesive, the functional structure  50  has the reflectivity greater than 80% and can reflect the light emitted from the light-emitting unit to the inside of the functional structure  50  to the outside, thereby improving the light extraction efficiency of the light-emitting unit. Of course, the functional structure  50  may be made of the gray adhesive. In this case, the functional structure  50  has the transmittance less than 30% and the reflectivity greater than 50% so that the external incident light can be absorbed and the light which is emitted from the light-emitting unit and incident into the functional structure  50  can be emitted to the outside. Thus, the functional structure  50  has the functions of reducing the reflection of the external light and improving the light extraction efficiency of the light-emitting unit. 
       FIG.  17    is a sectional view of another display panel according to an embodiment of the present disclosure. Referring to  FIG.  17   , in other embodiments of the present disclosure, the functional structure  50  may also be set to include a first functional layer  51  and a second functional layer  52 , where the first functional layer  51  is disposed on a side of the second functional layer  52  facing away from the base substrate  10 . The first functional layer  51  satisfies T1&lt;6%, and the second functional layer  52  satisfies R2&gt;80%, where T1 is the transmittance of the first functional layer  51  and R2 is the reflectivity of the second functional layer  52 . 
     The first functional layer  51  is disposed on the side of the second functional layer  52  facing away from the base substrate  10 , that is, the first functional layer  51  is disposed on the second functional layer  52 . The first functional layer  51  in the upper layer has the transmittance less than 6%, which indicates that the first functional layer  51  has good light absorption performance and can effectively block the external light so as to prevent the external light from continuing to be incident on the redundant electrode unit  22 . If the second functional layer  52  in the lower layer has the reflectivity greater than 80%, the light emitted from the light-emitting unit adjacent to the second functional layer  52  can be transmitted inside the second functional layer  52 , which is helpful for the light to be emitted from the bank structure to the outside, thereby increasing the light extraction efficiency of the light-emitting unit. Apparently, according to this setting manner, the two functional layers are used for respectively achieving the effects of reducing the reflection and increasing the light emission, thereby improving the display effect of the display panel as a whole. 
     In an embodiment, the thickness h1 of the preceding first functional layer  51  may be set to 3 μm to 5 μm, and the thickness h2 of the second functional layer  52  may be set to 5 μm to 7 μm. Considering that the bank structure has the limited height, the thickness of the functional structure filling the opening of the bank structure is also limited. In this embodiment, the first functional layer  51  of 3 μm to 5 μm is disposed, which can ensure that the light incident from the outside is sufficiently absorbed and effectively prevents the external light from being incident on the redundant electrode unit to avoid the reflection. The second functional layer  52  of 5 μm to 7 μm is disposed, and a relatively wide horizontal light transmission channel can be formed so that large-angle light of the light-emitting unit is transmitted through the channel and then is emitted from the bank structure to the outside, thereby improving the light extraction efficiency of the light-emitting unit. 
     Based on the same inventive concept, the embodiments of the present disclosure further provide a display device.  FIG.  18    is a structural diagram of a display device according to an embodiment of the present disclosure. Referring to  FIG.  18   , the display device may include the display panel  100  in any one of the embodiments. Since the display panel  100  in the preceding embodiment is used for preparing the display device provided in the embodiment of the present disclosure, the display device has the same or similar technical effects as the display panel provided in the embodiment of the present disclosure. The details are not repeated here. For example, the display device may be an electronic device such as a mobile phone, a computer, a smart wearable device (such as a smart watch), or an onboard display device, which is not limited in the embodiment of the present disclosure. 
     It is to be noted that the preceding are only preferred embodiments of the present disclosure and the technical principles used therein. It is to be understood by those skilled in the art that the present disclosure is not limited to the embodiments described herein. For those skilled in the art, various apparent modifications, adaptations, combinations, and substitutions can be made without departing from the scope of the present disclosure. Therefore, while the present disclosure has been described in detail via the preceding embodiments, the present disclosure is not limited to the preceding embodiments and may include more equivalent embodiments without departing from the inventive concept of the present disclosure. The scope of the present disclosure is determined by the scope of the appended claims.