Patent Publication Number: US-2023163142-A1

Title: Display substrate, method for preparing display substrate, and display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present disclosure is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/CN2021/094918, filed on May 20, 2021, which claims the priority of Chinese Patent Application No.202010524566.X, filed with the China National Intellectual Property Administration on Jun. 10, 2020 and entitled “DISPLAY PANEL, MANUFACTURING METHOD THEREFOR, AND DISPLAY APPARATUS”, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to the technical field of display, in particular to a display substrate, a manufacturing method therefor, and a display apparatus. 
     BACKGROUND 
     LED has advantages of low power consumption and high brightness, and a photoinduced quantum dot (QD) material has a wide color gamut and pure light color, therefore a QD-LED device structure provides an opportunity to achieve high-quality display with low power consumption, high brightness and wide color gamut. 
     SUMMARY 
     Embodiments of the present disclosure provide a display substrate, including:
     a driving substrate;   a plurality of LEDs, arranged on the driving substrate in an array;   an inorganic insulating layer, located between the driving substrate and the plurality of LEDs; wherein a plurality of first recesses are provided in one side of the inorganic insulating layer facing the plurality of LEDs, and orthographic projections of the first recesses on the driving substrate do not overlap orthographic projections of the LEDs on the driving substrate; and   a first planarization layer, covering the plurality of LEDs, wherein a plurality of bulges filling the first recesses are provided on one side of the first planarization layer facing the driving substrate.   

     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, the inorganic insulating layer includes: a first insulating layer located between the driving substrate and the plurality of LEDs, and a second insulating layer located between the first insulating layer and the plurality of LEDs. The second insulating layer and the first insulating layer are different in material. 
     The plurality of first recesses are formed in one side of the second insulating layer facing the plurality of LEDs. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, a thickness of the first insulating layer is 0.2 µm-1 µm, and a thickness of the second insulating layer is 2 µm-3 µm. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, the inorganic insulating layer is a single inorganic insulating layer, and a thickness of the single inorganic insulating layer is 2 µm-3 µm. 
     Optionally, during implementations, the above display substrate provided by the embodiments of the present disclosure further includes a blocking dam structure located on one side of the first planarization layer facing away from the driving substrate. The blocking dam structure has a plurality of pixel openings, and the pixel openings are in one-to-one correspondence with the LEDs. 
     The pixel openings include a first sub-pixel opening and a second sub-pixel opening. A red quantum dot color film is disposed in the first sub-pixel opening, and a green quantum dot color film is disposed in the second sub-pixel opening. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, the pixel openings further include a third sub-pixel opening, and the third sub-pixel opening is filled with scattered particles. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, the first planarization layer internally has a plurality of scattered particles. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, one side of the first planarization layer facing the blocking dam structure is provided with a plurality of second recesses, and the second recesses are filled with the blocking dam structure. 
     Optionally, during implementations, the above display substrate provided by the embodiments of the present disclosure further includes an encapsulation layer, covering the red quantum dot color film, the green quantum dot color film, and the blocking dam structure. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, in a direction perpendicular to a thickness of a driving substrate, a cross section shape of the first recess is one or a combination of an isosceles trapezoid, a right-angled trapezoid, or a rectangle. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, the driving substrate includes: a base substrate, a drive circuit located on one side of the base substrate facing the LEDs, a second planarization layer located on one side of the drive circuit facing the LEDs, and a first electrode and a second electrode which are located on one side of the second planarization layer facing the LEDs; and the first electrode is electrically connected with the drive circuit through a first via hole penetrating through the second planarization layer, and the second electrode is grounded. 
     One side of the LEDs facing the driving substrate includes a third electrode and a fourth electrode, the third electrode is electrically connected with the first electrode through a second via hole penetrating through the inorganic insulating layer, and the fourth electrode is electrically connected with the second electrode through a third via hole penetrating through the inorganic insulating layer. 
     Optionally, during implementations, in the above display substrate provided by the embodiments of the present disclosure, the LEDs are Micro LEDs. 
     Accordingly, embodiments of the present disclosure provide a display apparatus, including the above display substrate provided by the embodiments of the present disclosure. 
     Accordingly, embodiments of the present disclosure further provide a method for preparing the above display substrate provided by the embodiments of the present disclosure, including:
     providing a driving substrate;   forming an inorganic insulating layer on the driving substrate;   forming a plurality of first recesses in one side of the inorganic insulating layer facing away from the driving substrate;   forming a plurality of LEDs on one side of the inorganic insulating layer facing away from the driving substrate, wherein orthographic projections of the first recesses on the driving substrate do not overlap orthographic projections of the LEDs on the driving substrate; and   forming a first planarization layer covering the plurality of LEDs on one side of the plurality of LEDs facing away from the driving substrate, wherein one side of the first planarization layer facing the driving substrate has a plurality of bulges filling the first recesses.   

     Optionally, during implementations, in the above method provided by the embodiments of the present disclosure, the forming the inorganic insulating layer on the driving substrate, and the forming the plurality of first recesses in one side of the inorganic insulating layer facing away from the driving substrate include:
     forming a first insulating layer on the driving substrate;   forming a second insulating layer on one side of the first insulating layer facing away from the driving substrate; and   etching the second insulating layer to form the plurality of first recesses.   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a sectional structure of a display substrate provided by an embodiment of the present disclosure. 
         FIG.  2    is a schematic diagram of a sectional structure of another display substrate provided by an embodiment of the present disclosure. 
         FIG.  3    is a schematic diagram of a sectional structure of another display substrate provided by an embodiment of the present disclosure. 
         FIG.  4    is a schematic diagram of a sectional structure of another display substrate provided by an embodiment of the present disclosure. 
         FIG.  5    is a schematic diagram of a sectional structure of another display substrate provided by an embodiment of the present disclosure. 
         FIG.  6    is a schematic diagram of a sectional structure of another display substrate provided by an embodiment of the present disclosure. 
         FIG.  7    is a schematic diagram of a sectional structure of another display substrate provided by an embodiment of the present disclosure. 
         FIG.  8    is a schematic structural diagram of a LED provided by an embodiment of the present disclosure. 
         FIG.  9    is a schematic flow diagram of a method for preparing a display substrate provided by an embodiment of the present disclosure. 
         FIG.  10    is another schematic flow diagram of a method for preparing a display substrate provided by an embodiment of the present disclosure. 
         FIG.  11 A - FIG.  11 H  are respectively schematic structural diagrams of a display substrate after each step is executed in the method for preparing the display substrate provided by an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In order to make the objective, technical solutions and advantages of the present disclosure clearer, the implementations of a display substrate, a method for preparing the display substrate, and a display apparatus provided by the embodiments of the present disclosure will be illustrated in detail below with reference to accompanying drawings. 
     Thicknesses and shapes of all layers of films in the accompanying drawings do not reflect the true scale of the display substrate, and only intend to illustrate the content of the present disclosure. 
     At present, for a QD-LED device structure, after a driving substrate is prepared, a planarization layer needs to be formed, and then a transfer electrode is formed for bonding the LED. Because the driving substrate with the transfer electrode prepared is bonded with the LED provided by a manufacturer, a material of the transfer electrode is generally Ag, Au and the like. In order to protect the transfer electrode from being oxidized before bonding, a thin silicon nitride protective layer needs to be prepared on the transfer electrode. During bonding, the transfer electrode needs to be exposed by etching so as to be electrically connected with an electrode of the LED. After bonding is completed, another planarization layer (generally white oil) needs to be formed above the LED, so as to eliminate segment difference when printing a QD material on the LED. However, a binding force of an organic-inorganic contact interface between the planarization layer above the LED and the silicon nitride protective layer below the LED is poor, the planarization layer above the LED has a risk of easy peeling-off, resulting in reduce of stability of the QD-LED device structure. 
     In order to solve the above problem, embodiments of the present disclosure provide a display substrate, as shown in  FIG.  1    to  FIG.  7   , including:
     a driving substrate  1 ;   a plurality of LEDs  2 , arranged on the driving substrate  1  in an array;   an inorganic insulating layer  3 , located between the driving substrate  1  and the plurality of LEDs  2 ; wherein a plurality of first recesses  01  are formed in one side of the inorganic insulating layer  3  facing the plurality of LEDs  2 , and orthographic projections of the first recesses  01  on the driving substrate  1  do not overlap orthographic projections of the LEDs  2  on the driving substrate  1 ; and   a first planarization layer  4 , covering the plurality of LEDs  2 , wherein one side of the first planarization layer  4  facing the driving substrate  1  is provided with a plurality of bulges  02  filling the first recesses  01 .   

     According to the above display substrate provided by the embodiments of the present disclosure, the plurality of first recesses  01  are formed in one side of the inorganic insulating layer  3  facing the plurality of LEDs  2 ; and orthographic projections of the first recesses  01  on the driving substrate  1  do not overlap orthographic projections of the LEDs  2  on the driving substrate  1 , and thus, when the first planarization layer  4  is formed on one side of the plurality of LEDs  2  facing away from the driving substrate  1 , the first recesses  01  can be filled with the first planarization layer  4 , so that a contact area between the first planarization layer  4  and the inorganic insulating layer  3  can be increased, a binding force between the first planarization layer  4  and the inorganic insulating layer  3  can be increased, and the risk of peeling off the first planarization layer  4  can be reduced, thereby improving the stability of a QD-LED device. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, a size of the LED is generally smaller than 200 µm. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, the LEDs may be Micro LEDs. Due to a small size of the Micro LED, a pixel resolution of the display substrate may be improved. For example, a size of the Micro LED is generally smaller than 100 µm. Of course, the LEDs may also be other LEDs such as Mini LEDs, which is not limited in the present disclosure. For example, when the LEDs are the Mini LEDs, a size of the Mini LED is 100 µm-200 µm. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   , the inorganic insulating layer  3  includes: a first insulating layer  31  located between the driving substrate  1  and the plurality of LEDs  2 , and a second insulating layer  32  located between the first insulating layer  31  and the plurality of LEDs  2 . The material of the second insulating layer  32  is different from the material of the first insulating layer  31 . For example, a material of the first insulating layer  31  is silicon nitride, and a material of the second insulating layer  32  is silicon oxide or silicon oxynitride. Because the silicon nitride, the silicon oxide and the silicon oxynitride have similar lattices, adhesive force between the first insulating layer  31  made of the silicon nitride and the second insulating layer  32  made of the silicon oxide or the silicon oxynitride is good. The plurality of first recesses  01  are formed in one side of the second insulating layer  32  facing the plurality of LEDs  2 . 
     For a QD-Micro LED device structure, after the driving substrate is prepared, the planarization layer needs to be formed, and then a transfer electrode is formed for bonding the Micro LED. Because the driving substrate with the transfer electrode prepared is bonded with the Micro LED provided by a manufacturer, in order to protect the transfer electrode, a thin silicon nitride protective layer (i.e., the first insulating layer  31 ) needs to be prepared on the transfer electrode to cover the transfer electrode. Before bonding, the silicon nitride protective layer is etched through an etching process to expose the transfer electrode, so that the transfer electrode is bonded with an electrode of the LED. In order to prevent the risk of peeling-off of the subsequently formed first planarization layer  4 , it needs to increase the contact area between the first insulating layer  31  and the first planarization layer  4 . However, because a thickness of the first insulating layer  31  is small and is generally 0.2 µm-0.6 µm, the thickness is not enough for digging recesses in the first insulating layer  31  to increase the contact area between the first insulating layer  31  and the first planarization layer  4 , thus in the present disclosure, the second insulating layer  32  with a certain thickness is disposed above the first insulating layer  31 , and the additional second insulating layer  32  may be disposed to be thick, on which the required recess structure may be prepared. Therefore, by disposing the plurality of first recesses  01  in one side of the second insulating layer  32  facing the plurality of LEDs  2 , when the first planarization layer  4  is subsequently formed, the first recesses  01  are filled with the first planarization layer  4 , thereby increasing the contact area between the first planarization layer  4  and the second insulating layer  32 . In addition, the second insulating layer  32  is made of different materials similar to the lattice of the first insulating layer  31 , such as silicon oxide or silicon oxynitride. Because the lattices of the silicon nitride, the silicon oxide and the silicon oxynitride are similar, the adhesive force between the first insulating layer  31  made of the silicon nitride and the second insulating layer  32  made of the silicon oxide or the silicon oxynitride is good. Therefore, the present disclosure can increase the contact area between the first planarization layer  4  and the second insulating layer  32 , avoid the risk of falling-off of the first planarization layer  4 , thereby improving the stability of the device. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   , a thickness of the first insulating layer  31  may be 0.2 µm-1 µm, and a thickness of the second insulating layer may be 2 µm-3 µm. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  2   , the inorganic insulating layer  3  may also be a single layer, and a thickness of the single layer of the inorganic insulating layer  3  is 2 µm-3 µm.That is, when forming the above silicon nitride protective layer for protecting the transfer electrode, the silicon nitride protective layer is directly prepared into a film layer (i.e., the inorganic insulating layer  3 ) with a thickness of 2 µm-3 µm, then the plurality of first recesses  01  are formed by etching the single layer of inorganic insulating layer  3 . In this way, compared with a solution in  FIG.  1   , a step of preparing an insulating layer one time may be saved, and a manufacturing process is simplified. 
     During implementations, the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  2   , may further include a blocking dam structure  5  located on one side of the first planarization layer  4  facing away from the driving substrate  1 . The blocking dam structure  5  is provided with a plurality of pixel openings, and the pixel openings are in one-to-one correspondence with the LEDs  2 . The blocking dam structure  5  may prevent crosstalk between adjacent sub pixels during light emission. 
     The pixel openings include a first sub-pixel opening  51  and a second sub-pixel opening  52 . A red quantum dot color film R is disposed in the first sub-pixel opening  51 , and a green quantum dot color film G is disposed in the second sub-pixel opening  52 . 
     It should be noted that the above pixel openings are in one-to-one correspondence with the LEDs  2 , which means that orthographic projections of the pixel openings on the driving substrate  1  and orthographic projections of the LEDs  2  on the driving substrate  1  have an overlapping area. For example, an orthographic projection of the first sub-pixel opening  51  on the driving substrate  1  and the orthographic projection of the LEDs  2  on the driving substrate  1  have an overlapping area, an orthographic projection of the second sub-pixel opening  52  on the driving substrate  1  and the orthographic projection of the LED  2  on the driving substrate  1  have an overlapping area, and an orthographic projection of a third sub-pixel opening  53  introduced later on the driving substrate  1  and the orthographic projection of the LED  2  on the driving substrate  1  also have an overlapping area.  FIG.  1   - FIG.  7    show that the pixel openings cover the LEDs  2 . Of course, it may also be that the LEDs  2  cover the pixel openings, or the LEDs  2  and the pixel openings partially overlap. 
     The LEDs  2  generally emit blue light, so the quantum dot color film only including a red quantum dot color film layer R and a green quantum dot color film layer G is arranged to achieve full color display. 
     During implementations, because a photoluminescent quantum dot material has a wide color gamut and pure light color, a material of the color film layer in the embodiments of the present disclosure is quantum dots. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  3   , the pixel openings further include a third sub-pixel opening  53 , and the third sub-pixel opening  53  is filled with scattered particles  03 . For example, the scattered particles  03  are doped in a resin material, and then the resin material doped with the scattered particles  03  is used to fill a depression of the third sub-pixel opening  53 . The scattered particles can enhance a light-emitting effect and increase a light-emitting angle. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   - FIG.  7   , the first planarization layer  4  may internally have the plurality of scattered particles (not shown). For example, a material of the first planarization layer  4  is generally resin. By doping the scattered particles in the resin, a role of planarize the segment difference is achieved, and the light-emitting effect of the LEDs  2  and the light-emitting angle may further be enhanced. 
     During implementations, since there are a plurality of scattered particles in the first planarization layer, the scattered particles can increase the light-emitting angle. In order to further prevent the crosstalk between the adjacent pixels, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  4   , a plurality of second recesses  04  are disposed in one side of the first planarization layer  4  facing the blocking dam structure  5 , and the second recesses  04  are filled with the blocking dam structure  5 . This is equivalent to increasing a height of the blocking dam structure  5  towards the LEDs  2 , which can block blue light emitted by the LEDs  2  from being shined on the adjacent pixels, thus improving the light-emitting efficiency. 
     During implementations, the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   - FIG.  7   , further includes an encapsulation layer  6  covering the red quantum dot color film R, the green quantum dot color film G and the blocking dam structure  5 . For example, the encapsulation layer  6  may include an inorganic layer, an organic layer and an inorganic layer which are alternatively disposed. The encapsulation layer is used to block external water vapor, protect the quantum dot material from contacting water, oxygen, and the like, so as to improve the stability and service life of the device. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, in a direction perpendicular to a thickness of a base substrate, a cross section shape of the first recess may be one or a combination of an isosceles trapezoid, a right-angled trapezoid and a rectangle. For example, as shown in  FIG.  1   - FIG.  4   , the cross section shape of the first recess  01  is the isosceles trapezoid; as shown in  FIG.  5   , the cross section shape of the first recesse  01  is the rectangle; and as shown in  FIG.  6    and  FIG.  7   , the cross section shape of the first recess  01  is the right-angled trapezoid. 
     Of course, during implementations, the cross section shape of the first recess is not limited to the above listed regular shapes, but also may be other irregular shapes. As long as a recess is disposed on one side of the inorganic insulating layer facing away from the driving substrate, so that the recess is filled with the first planarization layer so as to increase the contact area between the first planarization layer and the inorganic insulating layer, all of which belong to the scope of the protection of the present disclosure, and will not be listed one by one here. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, a top view of the inorganic insulating layer may be rectangular or circular or other shapes. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   - FIG.  7   , a depth of the first recess  01  may be 0.1 µm-0.6 µm. 
     It should be noted that the above first recesses in the embodiments of the present disclosure are illustrated by taking an example of the first recesses not penetrating through the inorganic insulating layer. Of course, during implementations, the first recesses may also completely penetrate through the inorganic insulating layer. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   - FIG.  7   , a thickness of the first planarization layer  4   may be 8 µm-10 µm. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   - FIG.  7   , the driving substrate  1  includes: a base substrate  7 ; a drive circuit  8  located on one side of the base substrate  7  facing the LEDs  2 , wherein the drive circuit  8  includes an active layer  81 , a first gate layer  82 , a second gate layer  83 , a source electrode  84  and a drain electrode  85 ; a second planarization layer  9  located on one side of the drive circuit  8  facing the LEDs  2 , and a first electrode  11  and a second electrode  12  which are located on one side of the second planarization layer  9  facing the Micro LEDs  2 . The first electrode  11  is electrically connected with the drive circuit  8  through a first via hole  91  penetrating through the second planarization layer  9 , that is, the first electrode  11  is electrically connected with the drain electrode  85  through the first via hole  91  penetrating through the second planarization layer  9 . The second electrode  12  is grounded. For example, the first electrode  11  and the second electrode  12  are the transfer electrodes (pins) for outsourcing and transfer printing of the LEDs  2 , and materials of the first electrode  11  and the second electrode  12  are Ag, Au and the like. 
     One side of the LEDs  2  facing the driving substrate  1  includes a third electrode  21  and a fourth electrode  22 , the third electrode  21  is electrically connected with the first electrode  11  through a second via hole  33  penetrating through the inorganic insulating layer  3 , and the fourth electrode  22  is electrically connected with the second electrode  12  through a third via hole  34  penetrating through the inorganic insulating layer  3 . For example, when the LEDs  2  emit light, a drive current is input to the LEDs  2  through the drive circuit  8 . The specific light-emitting principle is the same as that of related art, and will not be detailed here. 
     During implementations, as shown in  FIG.  1   - FIG.  7   , the driving substrate  1  may further include a buffer layer  10  located between the base substrate  7  and the drive circuit  8 , a first gate insulating layer  13  located between the active layer  81  and the first gate layer  82 , a second gate insulating layer  14  located between the first gate layer  82  and the second gate layer  83 , and an interlayer insulating layer  15  located between the second gate layer  83  and the source electrode  84  as well as the drain electrode  85 . 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  1   - FIG.  7   , in a direction of the driving substrate  1  pointing to the LEDs  2 , a thickness of the third electrode  21  is the same as a thickness of the fourth electrode  22 , and the thickness of the third electrode  21  is greater than a depth of the second via hole  33 . By setting the thickness of the third electrode  21  to be greater than the depth of the second via hole  33 , when the third electrode  21  of the LEDs  2  is electrically connected with the first electrode  11  through the second via hole  33  and the fourth electrode  22  of the LEDs  2  is electrically connected with the second electrode  12  through the third via hole  34 , it can be ensured that both the third electrode  21  and the fourth electrode  22  can go deep into the bottom of the corresponding via hole to be electrically connect with the corresponding electrode, that is, good contact between a P/N pad (the third electrode  21  and the fourth electrode  22 ) and the pins of the driving substrate (the first electrode  11  and the second electrode  12 ) in the transfer printing process of the LEDs  2  is ensured. 
     During implementations, in the above display substrate provided by the embodiments of the present disclosure, as shown in  FIG.  8   , a structure of the LEDs  2  includes: a P-type semiconductor layer  001 , an N-type semiconductor layer  002 , an active layer  003  located between the P-type semiconductor layer  001  and the N-type semiconductor layer  002 , the third electrode  21  (P-type pad), and the fourth electrode  22  (N-type pad). The LEDs are transfer printed to the driving substrate  1  through the transfer electrode (the first electrode  11  and the second electrode  12 ). The LEDs are of an inorganic material with good stability compared with an organic material. 
     During implementations, the above display substrate provided by the embodiments of the present disclosure may further include other functional film layers well known to those skilled in the art, which is not described in detail here. 
     It should be noted that in the above display substrates of  FIG.  1   - FIG.  7    provided by the embodiments of the present disclosure, a material of the blocking dam structure  5  is generally hydrophobic. When the quantum dot color film is prepared by adopting a solution method (printing or ink-jet printing), a shape of the quantum dot color film far from a surface of the driving substrate  1  is curved, that is, in the direction perpendicular to the thickness of the driving substrate  1 , cross sections of the red quantum dot color film R and the green quantum dot color film R are curved surfaces. 
     Based on the same inventive concept, embodiments of the present disclosure further provide a method for preparing a display substrate, referring to  FIG.  9   , including the following steps. 
     S 901 , a driving substrate is provided. 
     S 902 , an inorganic insulating layer is formed on the driving substrate. 
     S 903 , a plurality of first recesses are formed in one side of the inorganic insulating layer facing away from the driving substrate. 
     S 904 , a plurality of LEDs are formed on one side of the inorganic insulating layer facing away from the driving substrate. Orthographic projections of the first recesses on the driving substrate do not overlap orthographic projections of the LEDs on the driving substrate. 
     S 905 , a first planarization layer covering the plurality of LEDs is formed on one side of the plurality of LEDs facing away from the driving substrate. One side of the first planarization layer facing the driving substrate is provided with a plurality of bulges filling the first recesses. 
     According to the above method for preparing the display substrate provided by the embodiments of the present disclosure, the plurality of first recesses are formed in one side of the inorganic insulating layer facing away from the driving substrate; and the orthographic projections of the first recesses on the driving substrate do not overlap orthographic projections of the LEDs on the driving substrate, and thus, when the first planarization layer is formed on one side of the plurality of LEDs facing away from the driving substrate, the first recesses can be filled with the first planarization layer, so that a contact area between the first planarization layer and the inorganic insulating layer can be increased, a binding force between the first planarization layer and the inorganic insulating layer can be increased, and the risk of peeling off the first planarization layer can be reduced, thereby improving the stability of a QD-Micro LED device. 
     During implementations, in the above method provided by the embodiments of the present disclosure, the forming the inorganic insulating layer on the driving substrate, and the forming the plurality of first recesses in one side of the inorganic insulating layer facing away from the driving substrate, as shown in  FIG.  10   , include:
     S 1001 , a first insulating layer is formed on the driving substrate;   S 1002 , a second insulating layer is formed on one side of the first insulating layer facing away from the driving substrate; and   S 1003 , the second insulating layer is etched to form the plurality of first recesses.   

     The method for preparing the display substrate shown in  FIG.  1    is illustrated in detail below. 
     (1) the driving substrate  1  is provided, a method for preparing the driving substrate  1  is the same as that of the related art, which will not be detailed here, as shown in  FIG.  11 A .   (2) the first insulating layer  31  is formed on the driving substrate  1 , as shown in  FIG.  11 B . A material of the first insulating layer  31  is silicon nitride.   (3) the second insulating layer  32  is formed on one side of the first insulating layer  31  facing away from the driving substrate  1 , as shown in  FIG.  11 C . A material of the second insulating layer  32  is silicon oxide or silicon oxynitride.   (4) the second insulating layer  32  is etched to form the plurality of first recesses  01 , a plurality of second via holes  33 , and a plurality of third via holes  34 . The second via hole  33  and the third via hole  34  correspondingly expose a first electrode  11  and a second electrode  12  on the driving substrate  1 , as shown in  FIG.  11 D .   (5) the LEDs  2  are bonded to the driving substrate  1  by means of bonding, that is, a third electrode  21  of the LEDs  2  is electrically connected with the first electrode  11  on the driving substrate  1 , and a fourth electrode  22  of the LEDs  2  is electrically connected with the second electrode  12  on the driving substrate  1 , as shown in  FIG.  11 E .   (6) the first planarization layer  4  covering the plurality of LEDs  2  is formed on one side of the plurality of LEDs  2  facing away from the driving substrate  1 , and the first recesses  01  are filled with the first planarization layer  4 , as shown in  FIG.  11 F .   (7) a blocking dam structure  5  with a plurality of pixel openings is formed on one side of the first planarization layer  4  facing away from the driving substrate  1 , as shown in  FIG.  11 G .   (8) color film layers of different colors (a red quantum dot color film layer R and a green quantum dot color film layer G) are formed in the pixel openings by printing or ink-jet printing, as shown in  FIG.  11 H .   (9) an encapsulation layer  6  covering the color film layers and the blocking dam structure  5  is formed, as shown in  FIG.  1   .   

     It should be noted that the method of the embodiments of the present disclosure is illustrated by taking the inorganic insulating layer shown in  FIG.  1    including the first insulating layer and the second insulating layer as an example. The method for preparing the display substrate in  FIG.  2    is different from that for preparing the display substrate in  FIG.  1    only in that when the inorganic insulating layer  3  is formed, the inorganic insulating layer with the thickness of 2 µm-3 µm is directly formed one time. The method for preparing the display substrate in  FIG.  3    is different from that for preparing the display substrate in  FIG.  1    only in that a third sub-pixel opening is filled with scattered particles when the color film layer is formed. The method for preparing the display substrate in  FIG.  4    is different from that for preparing the display substrate in  FIG.  1    only in that after the first planarization layer  4  is formed, the first planarization layer  4  is etched to form the plurality of second recesses  04 , so that the second recesses  04  are filled with the blocking dam structure. The method for preparing the display substrate in  FIG.  5   - FIG.  7    is different from that for preparing the display substrate in  FIG.  1    only in that a shape of the first recess  01  formed by etching is different, which can be achieved by controlling the exposure amount at different positions of photoresist. 
     During implementations, the above touch display substrate provided by the embodiments of the present disclosure may be: any product or component with a display function, such as a mobile phone, a tablet computer, a television, a displayer, a notebook computer, a digital photo frame, and a navigator. It should be understood by a person of ordinary skill in the art that the touch display substrate should have other essential constituent parts, which is not repeated here and should not be regarded as limitation to the present disclosure. Implementation of the display apparatus may refer to embodiments of the above display substrate, and repetitions are omitted. 
     Embodiments of the present disclosure provide the display substrate, the method for preparing the display substrate, and the display apparatus. The display substrate includes: the driving substrate; the plurality of LEDs, wherein the plurality of LEDs are arranged on the driving substrate in an array; the inorganic insulating layer, located between the driving substrate and the plurality of LEDs; one side of the inorganic insulating layer facing the plurality of LEDs is provided with the plurality of first recesses, and the orthographic projections of the first recesses on the driving substrate do not overlap the orthographic projections of the LEDs on the driving substrate; and the first planarization layer, located on one side of the plurality of LEDs facing away from the driving substrate, wherein one side of the first planarization layer facing the driving substrate has a plurality of bulges filling the first recesses. According to the present disclosure, the plurality of first recesses are formed in one side of the inorganic insulating layer facing the plurality of LEDs; and the orthographic projections of the first recesses on the driving substrate do not overlap the orthographic projections of the LEDs on the driving substrate, and thus, when the first planarization layer is formed on one side of the plurality of LEDs facing away from the driving substrate, the first recesses can be filled with the first planarization layer, so that a contact area between the first planarization layer and the inorganic insulating layer can be increased, a binding force between the first planarization layer and the inorganic insulating layer can be increased, and the risk of peeling off the first planarization layer can be reduced, thereby improving the stability of a QD-LED device. 
     Obviously, those skilled in the art can make various modifications and variations to the present disclosure without departing from the spirit and scope of the present disclosure. In this way, if these modifications and variations of the present disclosure fall within the scope of the claims of the present disclosure and their equivalent art, the present disclosure also intends to include these modifications and variations.