Light-emitting substrate, manufacturing method therefor, and display device

Abstract

Disclosed are a light-emitting substrate, a manufacturing method therefor, and a display device, for use in improving the light-emitting efficiency of the light-emitting substrate. According to the light-emitting substrate provided by embodiments of the present invention, the light-emitting substrate comprises: a driving backplane; a plurality of light-emitting units, which are located on one side of the driving backplane; and a packaging layer, covering the side surface of each light-emitting unit and a part of the surface of the side of the light-emitting unit facing away from the driving backplane. The packaging layer comprises at least one first modification layer; and the first modification layer is used for passivating a side surface defect of the light-emitting unit.

Description

Luminescent substrate, preparation method thereof, and display device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to Chinese patent application number 202311622106.0 filed with the State Intellectual Property Office of the People's Republic of China on November 30, 2023, entitled "Luminescent substrate, preparation method thereof, and display device," the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of display technology, and in particular to a light-emitting substrate and a preparation method thereof, and a display device. Background Art

[0004] Light-emitting diodes (LEDs) are widely used in lighting and display technologies due to their small size, low power consumption, long life, high brightness, and active illumination. Micro-LEDs, also known as micro-LEDs, mLEDs, or μLEDs, are a new type of flat-panel display technology. Micro-LED displays feature LED arrays with individual pixel elements. Compared to currently used liquid crystal displays, micro-LED displays offer better contrast, faster response times, and lower energy consumption.

[0005] Summary of the Invention

[0006] The embodiments of the present disclosure provide a light-emitting substrate, a preparation method thereof, and a display device, so as to improve the light-emitting efficiency of the light-emitting substrate.

[0007] The present disclosure provides a light-emitting substrate, comprising:

[0008] Driver backplane;

[0009] A plurality of light-emitting units are located on one side of the driving backplane;

[0010] The encapsulation layer covers the side surface of the light-emitting unit and a portion of the surface of the light-emitting unit away from the driving backplane; the encapsulation layer includes at least one first modification layer; the first modification layer is used to passivate side defects of the light-emitting unit.

[0011] In some embodiments, the encapsulation layer further comprises:

[0012] The heat dissipation layer is located between the first modification layer closest to the light-emitting unit and the light-emitting unit; the heat dissipation layer includes a heat insulating material.

[0013] In some embodiments, the material of the heat dissipation layer includes one of the following or a combination thereof: aluminum oxide, aluminum nitride, silicon oxide, and silicon nitride.

[0014] In some embodiments, the material of the first modified layer includes one or a combination of the following: silicon oxide, aluminum oxide, aluminum nitride, and silicon nitride.

[0015] In some embodiments, the heat dissipation layer is made of a different material than the first modification layer adjacent thereto.

[0016] In some embodiments, the encapsulation layer further comprises:

[0017] The light extraction layer is located on a side of the first modified layer away from the light emitting unit.

[0018] In some embodiments, the light extraction layer includes a plurality of stacked light-transmitting sub-layers, and the refractive indices of any two adjacent light-transmitting sub-layers are different.

[0019] In some embodiments, the multi-layer light-transmitting sub-layer includes: a first light-transmitting sub-layer, a second light-transmitting sub-layer, and a third light-transmitting sub-layer stacked in sequence on a side away from the first modified layer;

[0020] The material of the first light-transmitting sub-layer includes silicon oxide, the material of the second light-transmitting sub-layer includes aluminum oxide, and the material of the third light-transmitting sub-layer includes silicon nitride.

[0021] In some embodiments, a side surface of the light-emitting unit includes a second modification layer, and / or a surface of the encapsulation layer facing away from the light-emitting unit includes a second modification layer.

[0022] In some embodiments, the second modification layer includes one of the following: a sulfide, an aluminum compound, or a hydride.

[0023] The present disclosure provides a method for preparing a light-emitting substrate, comprising:

[0024] Manufacturing the film layers of the light-emitting unit and the driving backplane;

[0025] Transferring each film layer of the light-emitting unit to the driving backplane, and performing a patterning process on each film layer of the light-emitting unit to form a plurality of light-emitting units;

[0026] An encapsulation layer including at least one first modification layer is formed; the encapsulation layer covers the side surface of the light emitting unit and a portion of the surface of the light emitting unit away from the driving backplane, and the first modification layer is used to passivate side defects of the light emitting unit.

[0027] In some embodiments, before forming at least one first modification layer, the method further comprises:

[0028] A heat dissipation layer is formed.

[0029] In some embodiments, after forming at least one first modification layer, the method further comprises:

[0030] A light extraction layer is formed; the light extraction layer includes a plurality of light-transmitting sub-layers stacked together, and the refractive indices of any two adjacent light-transmitting sub-layers are different.

[0031] In some embodiments, before forming the encapsulation layer covering the plurality of light-emitting units, the method further includes:

[0032] forming a second modification layer on a side surface of the light emitting unit;

[0033] And / or, after forming the encapsulation layer covering the plurality of light-emitting units, the method further includes:

[0034] A second modification layer is formed on the surface of the encapsulation layer.

[0035] In some embodiments, forming a second modification layer on the side of the light-emitting unit specifically includes:

[0036] Performing vulcanization treatment on the side of the light-emitting unit;

[0037] Alternatively, the side surfaces of the light-emitting unit are surface treated using trimethylaluminum or nitrogen plasma;

[0038] Alternatively, hydrogen ions are used to perform surface treatment on the side surfaces of the light emitting unit.

[0039] In some embodiments, a second modification layer is formed on the surface of the encapsulation layer.

[0040] The surface of the encapsulation layer is treated by using trimethylaluminum and nitrogen plasma;

[0041] Alternatively, the surface of the encapsulation layer is treated with hydrogen ions.

[0042] A display device provided by an embodiment of the present disclosure includes the light-emitting substrate provided by an embodiment of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0044] FIG1 is a schematic structural diagram of a light-emitting substrate provided by an embodiment of the present disclosure;

[0045] FIG2 is a schematic diagram of defect modification according to an embodiment of the present disclosure;

[0046] FIG3 is a schematic structural diagram of another light-emitting substrate provided in an embodiment of the present disclosure;

[0047] FIG4 is a schematic structural diagram of another light-emitting substrate provided by an embodiment of the present disclosure;

[0048] FIG5 is a schematic structural diagram of another light-emitting substrate provided by an embodiment of the present disclosure;

[0049] FIG6 is a schematic diagram of the amplitude of interference of multiple light-transmitting sub-layers provided by an embodiment of the present disclosure;

[0050] FIG7 is a schematic diagram of the transmission coefficient and reflection coefficient of the interference of a multi-layer light-transmitting sub-layer provided by an embodiment of the present disclosure;

[0051] FIG8 is a graph showing transmittances of different multi-layer light-transmitting sub-layers according to an embodiment of the present disclosure;

[0052] FIG9 is a schematic structural diagram of another light-emitting substrate provided in an embodiment of the present disclosure;

[0053] FIG10 is a schematic structural diagram of another light-emitting substrate provided in an embodiment of the present disclosure;

[0054] FIG11 is a schematic structural diagram of another light-emitting substrate provided in an embodiment of the present disclosure;

[0055] FIG12 is a schematic flow chart of a method for preparing a light-emitting substrate according to an embodiment of the present disclosure;

[0056] FIG13 is a schematic flow chart of another method for preparing a light-emitting substrate provided in an embodiment of the present disclosure;

[0057] FIG14 is a SEM image of an I-shaped step provided in an embodiment of the present disclosure;

[0058] FIG15 is a SEM image of an I-shaped step covered with a thin film provided by an embodiment of the present disclosure;

[0059] FIG16 is an SEM image of the side of a light-emitting device covered with silicon nitride and aluminum oxide provided in an embodiment of the present disclosure;

[0060] FIG17 is a schematic diagram of a sulfurization process provided by an embodiment of the present disclosure;

[0061] FIG18 is a schematic structural diagram of a display device provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. And in the absence of conflict, the embodiments in the present disclosure and the features in the embodiments can be combined with each other. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0063] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by persons of ordinary skill in the field to which this disclosure belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0064] It should be noted that the sizes and shapes of the figures in the accompanying drawings do not reflect the actual scale and are only for the purpose of illustrating the present disclosure. The same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions.

[0065] In related technologies, defects in the sidewalls of light-emitting diodes (LEDs) can cause non-radiative recombination. As the size of the LED decreases, the probability of non-radiative recombination due to sidewall defects increases, resulting in a decrease in the LED's luminous efficiency. This phenomenon is known as the "efficiency-size effect." For micro-LEDs (micro-LEDs) smaller than 50 microns, the efficiency-size effect becomes particularly severe, resulting in lower luminous efficiency.

[0066] The present disclosure provides a light-emitting substrate, as shown in FIG1 , comprising:

[0067] Drive backplane 1;

[0068] A plurality of light-emitting units 2 are located on one side of the driving backplane 1;

[0069] The encapsulation layer 3 covers the side surfaces of the light emitting unit 2 and a portion of the surface of the light emitting unit 2 facing away from the driving backplane 1 ; the encapsulation layer 3 includes at least one first modification layer 301 ; the first modification layer 301 is used to passivate side defects of the light emitting unit 2 .

[0070] The light-emitting substrate provided by the embodiment of the present disclosure includes an encapsulation layer covering the side of the light-emitting unit, and the encapsulation layer includes a first modification layer. The first modification layer can passivate the defects on the side of the light-emitting unit, thereby reducing the defect state on the side of the light-emitting unit, reducing the probability of non-radiative recombination, and improving the radiation conformity efficiency, thereby improving the luminous efficiency of the light-emitting device and the luminous efficiency of the light-emitting substrate.

[0071] It should be noted that Figure 1 illustrates an encapsulation layer comprising a first decorative layer, which covers the side of the light-emitting device and a portion of the surface facing away from the driver backplane. In practice, the encapsulation layer may also comprise multiple first decorative layers stacked together. Unrepaired defects in the first decorative layer near the light-emitting device can be passivated again in the first decorative layer farther from the light-emitting device, further reducing defects and the probability of non-radiative recombination, thereby increasing radiative recombination efficiency and, in turn, improving the luminous efficiency of the light-emitting device and the luminous efficiency of the light-emitting substrate.

[0072] In some embodiments, as shown in FIG1 , the light emitting device 2 includes: a P-type semiconductor layer 201, a quantum well layer 202 located on a side of the P-type semiconductor layer 201 facing away from the driving backplane 1, an N-type semiconductor layer 203 located on a side of the quantum well layer 202 facing away from the driving backplane 1, a first electrode layer 204 located between the P-type semiconductor layer 201 and the driving backplane 1, and a second electrode layer 205 located between the first electrode layer 204 and the driving backplane 1;

[0073] The encapsulation layer 3 further includes a plurality of first openings 304 , each of the first openings 304 corresponding to the light emitting device 2 , and the first openings 304 expose a portion of the surface of the light emitting device 2 facing away from the driving backplane 1 ;

[0074] The light emitting substrate further includes a common electrode 6 located on a side of the packaging layer 3 facing away from the driving backplane 1 and electrically connected to the N-type semiconductor layer 203 through the first opening 304 .

[0075] In a specific implementation, the common electrode is provided on the entire surface, that is, the common electrode electrically connected to the plurality of light emitting devices is integrally connected.

[0076] In a specific implementation, the light-emitting device is a micro light-emitting diode (Micro LED), and the P-type semiconductor layer, quantum well layer, and N-type semiconductor layer are all semiconductor layers, including semiconductor materials such as gallium nitride (GaN), indium nitride (InN), and gallium indium phosphide (GaInP). The material of the first electrode layer includes, for example, indium tin oxide (ITO), and the material of the second electrode layer is, for example, a copper alloy. In addition to copper, the copper alloy may also include one or a combination of the following: titanium, gold, platinum, chromium, and tin.

[0077] It should be noted that in the current Micro LED manufacturing process, the film layers of the light-emitting unit are made on the substrate as an integrally connected film layer. After the film layers of the light-emitting unit are transferred to the driving backplane and bonded to the bonding pattern, the film layers of the light-emitting unit usually need to be divided to form multiple independent light-emitting units. However, in the process of dividing the film layers of the light-emitting unit, the light-emitting unit will be damaged, and the number of defects on the side of the light-emitting unit will increase. The defects on the side of the light-emitting device mainly refer to the defects of the semiconductor layer. The following example uses the P-type semiconductor layer, quantum well layer, and N-type semiconductor layer all including GaN as an example. The defects on the side of the light-emitting device include, for example, Ga dangling bonds and insufficient nitrogen (multiple vacancies). The provision of the first modification layer can form new chemical bonds, that is, passivate the defects on the side of the light-emitting device (also known as curing), reduce the defects on the side, reduce the probability of non-radiative recombination, improve the radiative efficiency, and improve the light output power (LOP) and external quantum efficiency (EQE) of the light-emitting device, thereby improving the luminous efficiency of the light-emitting device and the luminous efficiency of the light-emitting substrate.

[0078] In some embodiments, as shown in Figure 1, the driving backplane 1 includes: a base substrate 101, and a driving circuit layer 102 located between the base substrate 101 and the light-emitting device 2; the driving circuit layer 102 includes a plurality of bonding patterns 1021; the bonding patterns 1021 are electrically connected to the second electrode layer 205 of the light-emitting device 2 one by one.

[0079] In a specific implementation, the encapsulation layer also covers the side surfaces of the bonding patterns and the area between adjacent bonding patterns, that is, the encapsulation layer is disposed on the entire surface of the area outside the first opening.

[0080] In a specific implementation, the driving backplane can be a silicon-based driving backplane, and the driving circuit layer also includes: a transistor located between the substrate and the bonding pattern and multiple signal lines; the multiple signal lines include: a data line, a scan line and a common electrode line; the transistor includes: an active layer, a gate, a source, and a drain, the data line is electrically connected to the source of the transistor, the scan line is electrically connected to the gate of the transistor, the bonding pattern is electrically connected to the drain, and the common electrode is electrically connected to the common electrode line.

[0081] In some embodiments, the material of the first modified layer includes one or a combination of the following: silicon oxide (SiO2), aluminum oxide (Al2O3), aluminum nitride (AlN), and silicon nitride (Si3N4). These materials can passivate the sides of the semiconductor layer to form an interface layer, thereby reducing side defects, lowering the probability of non-radiative recombination, and improving radiative efficiency, thereby increasing the LOP and EQE of the light-emitting device.

[0082] Furthermore, the material of the first modified layer can be selected from materials with a high passivation rate, such as SiO2 or AlN.

[0083] It should be noted that the modification mechanism of defects by Al2O3 and AlN is shown in Figure 2. Assuming that the first modified layer is a crystalline structure, Al2O3 and AlN are bonded to the semiconductor layer of the light-emitting device through Ga-O and Ga-N, respectively. According to the lattice constants of the relevant materials, when the lattice constant of Al2O3 is a = 0.514 nanometers (nm), the lattice constant of AlN is a = 0.311nm, and the lattice constant of GaN is a = 0.319nm, the lattice mismatch between Al2O3 and GaN is significantly greater than that between AlN and GaN. In this case, as shown in Figure 2, compared with the interface between AlN and GaN, more dangling bonds are formed at the interface between Al2O3 and GaN, and the Al2O3 film can become a non-radiative recombination center and a leakage path for the etched sidewalls. There are fewer dangling bonds at the interface between AlN and GaN than at the interface between Al2O3 and GaN, and in AlN films. AlN has a stronger ability to eliminate defects on the side of the semiconductor layer. Passivating the side defects of the light-emitting device with AlN is more conducive to reducing non-radiative recombination centers and leakage paths of etched side walls, reducing the probability of non-radiative recombination, improving radiative efficiency, and improving the LOP and EQE of the light-emitting device.

[0084] It should be noted that SiO2 films are typically produced using a chemical vapor deposition process. SiO2 chemically reacts with defects on the side surfaces of the semiconductor layer, resulting in the formation of Ga-O bonds. Furthermore, the passivation rate of SiO2 is 1.1, while that of Al2O3 and Si3N4 is 1.06 and 0.33, respectively, making SiO2 a higher passivation rate. Based on the above discussion, SiO2 passivation is more effective than Al2O3 and Si3N4 in eliminating defects.

[0085] In some embodiments, as shown in FIG3 , the encapsulation layer 3 further includes:

[0086] The heat dissipation layer 302 is located between the first modification layer 301 closest to the light emitting unit 2 and the light emitting unit 2 ; the heat dissipation layer 302 includes a heat insulating material.

[0087] It should be noted that the junction temperature range of a light-emitting device during operation is 70°C to 100°C. Excessively high junction temperatures can cause thermal failure of the light-emitting device. Thermal failure can lead to the following problems: 1. The dominant wavelength of light emitted by the light-emitting device shifts. The bandgap width of semiconductor materials such as GaN and InN in the light-emitting device changes with temperature, causing the dominant wavelength of the emitted light to redshift. 2. Changes in the forward voltage of the light-emitting device. As the temperature rises, the forward voltage of the light-emitting device decreases. 3. Shortened service life. The characteristics of semiconductor devices are closely related to temperature. As the junction temperature rises, the luminous efficiency of the light-emitting device decreases rapidly, shortening its service life.

[0088] In the light-emitting substrate provided by the embodiments of the present disclosure, the encapsulation layer further includes a heat dissipation layer, which includes a heat-insulating material. This can avoid thermal failure of the light-emitting device, increase the service life of the light-emitting device, and avoid the problem of drift of the main wavelength of light emitted by the light-emitting device and changes in the forward voltage of the light-emitting device, thereby improving the display effect. In addition, the heat dissipation layer can also modify the side defects of the light-emitting device to reduce the defect state of the side. The first modification layer further modifies the defects. For defects that are not repaired by the heat dissipation layer, the first modification layer can be used to passivate them again, further reducing the defects, reducing the probability of non-radiative recombination, and improving the radiative efficiency, thereby improving the luminous efficiency of the light-emitting device and the luminous efficiency of the light-emitting substrate.

[0089] In a specific implementation, the heat dissipation layer and the first modification layer are stacked and arranged, and the heat dissipation layer covers the side surface of the light emitting device and the surface of the light emitting device facing away from the driving backplane.

[0090] In some embodiments, the material of the heat dissipation layer includes one of the following or a combination thereof: SiO 2 , Al 2 O 3 , AlN, Si 3 N 4 .

[0091] Furthermore, in order to ensure the heat insulation effect, the material of the heat dissipation layer is a heat insulation material with a relatively small thermal expansion coefficient, such as Al2O3 and AlN, wherein the thermal expansion coefficient of AlN is smaller than the thermal expansion coefficient of Al2O3.

[0092] In some embodiments, for the structure shown in FIG1 , that is, the structure in which the encapsulation layer includes the first modification layer but does not include the scattering layer, the material of the first modification layer can be set to meet both the requirements of a small thermal expansion coefficient and a high passivation rate, that is, the material of the first modification layer can simultaneously achieve the scattering effect and the defect modification effect. The scattering layer and the first modification layer can be combined into the same layer. The thickness of the first modification layer that meets the above requirements is greater than or equal to 50 angstroms. and less than or equal to

[0093] In some embodiments, the heat dissipation layer is made of a different material than the first modification layer adjacent thereto.

[0094] In a specific implementation, the total thickness of the heat dissipation layer and the first modification layer is greater than or equal to and less than or equal to

[0095] In some embodiments, the material of the heat dissipation layer includes AlN, and the material of the first modification layer includes SiO 2 .

[0096] In practice, the heat dissipation layer comprises AlN, which not only provides thermal insulation but also passivates side defects in the semiconductor layer of the light-emitting device. SiO2 can further passivate any unrepaired AlN defects, further reducing defects and the probability of non-radiative recombination, thereby increasing radiative recombination efficiency and, in turn, improving the luminous efficiency of the light-emitting device and the substrate.

[0097] It should be noted that for the SiO2 film layer, O atoms can diffuse to the side of the semiconductor layer and react chemically with the defects on the side of the semiconductor layer, resulting in the formation of Ga-O bonds. At the same time, O atoms can exist as interatoms during the passivation process. Moreover, since AlN is formed first and then SiO2, Si-O, Al-O, and Si-ON can form with Ga-O bonds during the annealing process. In the case of SiO2 passivation, the dissociation energy of the Si-O bond is 799.6 kilojoules per mole (kJ / mol), which is higher than the Ga-O formation enthalpy of 545 kJ / mol. Therefore, O atoms tend to diffuse into the interface of the GaN heat dissipation layer rather than react with atoms, resulting in a stronger chemical reaction. The formation of Ga-O bonds is easier than that of Si-O bonds. In addition, the passivation rate of SiO2 is 1.1, while the passivation rates of Al2O3 and Si3N4 are 1.06 and 0.33 respectively, and the passivation rate of SiO2 is higher. According to the above discussion, it can be seen that using SiO2 passivation is more conducive to further eliminating defects than using Al2O3 and Si3N4 passivation.

[0098] In some embodiments, as shown in FIG4 and FIG5 , the encapsulation layer 3 further includes:

[0099] The light extraction layer 303 is located on a side of the first modified layer 301 away from the light emitting unit 2 .

[0100] The light-emitting substrate provided in the disclosed embodiments includes an encapsulation layer further comprising a light extraction layer, thereby increasing the amount of light emitted by the light-emitting device after passing through the encapsulation layer, thereby improving light utilization. Furthermore, the light extraction layer can further passivate any unrepaired defects in the first modified layer, further reducing defects, lowering the probability of non-radiative recombination, and improving radiative recombination efficiency, thereby enhancing the luminous efficiency of both the light-emitting device and the light-emitting substrate.

[0101] In a specific implementation, the heat dissipation layer, the first modification layer, and the light extraction layer are stacked. The heat dissipation layer covers the side surface of the light emitting device and the surface of the light emitting device facing away from the driving backplane.

[0102] In some embodiments, as shown in FIG5 , the light extraction layer 303 includes a plurality of light-transmitting sub-layers 3031 stacked in layers;

[0103] The refractive indices of any two adjacent light-transmitting sub-layers 3031 are different.

[0104] It should be noted that the refractive index of any two adjacent light-transmitting sub-layers in the multi-layer light-transmitting sub-layers is different. According to the thin film interference theory, as shown in Figures 6 and 7, multi-beam interference will occur between the light-transmitting sub-layers. The final amplitude intensity of the light extraction layer should be the amplitude intensity obtained after multi-light interference. In Figures 6 and 7, three light extraction layers are taken as an example. The refractive index distribution of the three light extraction layers is n0, n1, and n2, and the reflection coefficient of interface 1 is r1. + 、r1 - , the transmission coefficient is t1 + , t1 - , the reflection coefficient of interface 2 is r2 + 、r2 - , the transmission coefficient is t2 + , t2 - , then the amplitude intensities of reflection and transmission E1, E2, E3, and E4 are: E1=r1 + ×E0; E2=t1 + ×r2 + ×t1 - ×e -j2α E0; E3 = t1 + ×r2 + ×r1 - ×r2 + ×t1 - ×e -j4α E0; E4 = t1 + ×r2 + ×r1 - ×r2 + ×r1 - ×r2 + ×t1 - ×e -j6α E0;

[0105] It can be seen that the above formula is a geometric progression. After adding up the various terms, the total amplitude Er of the reflected light satisfies:

[0106] For vertical incident light,

[0107] Wherein, E0 is the amplitude of the incident light, α is the phase thickness of the single-layer transparent sub-layer, n is the refractive index of the transparent sub-layer, and d is the thickness of the single-layer transparent sub-layer.

[0108] According to Fresnel's law, t1 + ×t1 - -r1 + ×r2 + =1, then formula (1) is:

[0109] Then the reflection coefficient r of a single-layer light-transmitting sub-layer can be obtained as:

[0110] The square of the reflection coefficient is not correct. We can use r to be proportional to its conjugate, and then we can get the reflectivity r of the single-layer light-transmitting sub-layer as:

[0111] Similarly, the total amplitude Et of the light transmitted by a single-layer transparent sub-layer can be obtained as:

[0112] The transmission coefficient t of a single light-transmitting sublayer is:

[0113] When calculating the transmittance of a single-layer light-transmitting sub-layer, according to the idea of ​​energy flux density, it should be multiplied by the corresponding cross-sectional area, and the transmittance T can be obtained to satisfy:

[0114] Among them, θ1 and θ2 are the angles of the light.

[0115] According to the above formula, the reflection coefficient and transmission coefficient of the cross section between the transparent sub-layers are related to the refractive index, while the phase shift is related to the thickness of the film layer. Therefore, the overall transmittance of the conditional light extraction layer can be achieved by adjusting the refractive index and thickness of each transparent sub-layer.

[0116] During specific implementation, the number, thickness, and material of the light-transmitting sub-layers in the light extraction layer can be selected according to the above formula so that the transmittance of the light extraction layer meets the requirements.

[0117] In some embodiments, the light extraction layer adopts a SiO2-Al2O3-SiN film structure, that is, the materials of the multi-layer light-transmitting sub-layer include SiO2, Al2O3, and SiN.

[0118] In a specific implementation, the relationship between the thickness, sequence and transmittance of the SiO2-Al2O3-SiN film system was simulated, and the results are shown in FIG8 . Among them, the multilayer transparent sublayer corresponding to curve A1 is: 350nm SiO2, 300nm SiN, and 200nm Al2O3 stacked in sequence on the side away from the first modified layer; the multilayer transparent sublayer corresponding to curve A2 is: 400nm SiO2, 600nm SiN, and 500nm Al2O3 stacked in sequence on the side away from the first modified layer; the multilayer transparent sublayer corresponding to curve A3 is: 500nm SiO2, 550nm Al2O3, and 350nm SiN stacked in sequence on the side away from the first modified layer; the multilayer transparent sublayer corresponding to curve A4 is: 70nm Al2O3, 725nm SiN, 400nm SiO2, 630nm Al2O3, and 250nm SiN stacked in sequence on the side away from the first modified layer.

[0119] In some embodiments, as shown in FIG5 , the multi-layer light-transmitting sub-layer 3031 includes: a first light-transmitting sub-layer 30311 , a second light-transmitting sub-layer 30312 , and a third light-transmitting sub-layer 30313 , which are sequentially stacked on a side away from the first modified layer 301 ;

[0120] The material of the first light-transmitting sub-layer 30311 includes SiO 2 , the material of the second light-transmitting sub-layer 30312 includes Al 2 O 3 , and the material of the third light-transmitting sub-layer 30313 includes SiN.

[0121] In some embodiments, the thickness of SiO 2 is 500 nm, the thickness of Al 2 O 3 is 550 nm, and the thickness of SiN is 350 nm.

[0122] Specifically, as shown in Figure 8, it can be seen that the material of the first light-transmitting sub-layer includes SiO2, the material of the second light-transmitting sub-layer includes Al2O3, and the material of the third light-transmitting sub-layer includes SiN. When the thickness of SiO2 is 500nm, the thickness of Al2O3 is 550nm, and the thickness of SiN is 350nm, the transmittance of the light extraction layer at red, green, and blue wavelengths can reach more than 90%, which can improve the transmittance of light emitted by the light-emitting device and improve the light utilization rate.

[0123] In some embodiments, when the encapsulation layer includes a light extraction layer, the total thickness of the encapsulation layer is greater than 50 nm and less than or equal to 4000 nm.

[0124] In some embodiments, as shown in FIG9 and FIG11 , the side surface of the light emitting unit 2 includes a second modification layer 5 , and / or, as shown in FIG10 and FIG11 , the surface of the encapsulation layer 3 facing away from the light emitting unit 2 includes a second modification layer 5 .

[0125] In the light-emitting substrate provided by the embodiments of the present disclosure, the side surfaces of the light-emitting units include a second modification layer. This layer is formed by treating side defects of the semiconductor layer in the light-emitting units, thereby reducing side defects of the semiconductor layer. The surface of the encapsulation layer facing away from the light-emitting units also includes a second modification layer. This layer is treated to modify unmodified defects in the encapsulation layer, further reducing defects.

[0126] In some embodiments, the second modification layer includes one of the following: a sulfide, an aluminum compound, or a hydride.

[0127] It should be noted that, due to the presence of dangling bond defects on the side of the semiconductor layer of the light-emitting device, these dangling bonds can form surface states with O atoms in the air or solution (such as etching solution, etc.), and due to the effect of the trap, a large number of carriers are captured by these surface states, resulting in non-radiative recombination on the side of the semiconductor layer. In a specific implementation, the side of the light-emitting device can be sulfurized so that the sulfur atoms are combined with the dangling bonds, that is, the side of the semiconductor layer of the light-emitting device forms a second modification layer including sulfide, which prevents the oxygen atoms from recombining with the dangling bonds, thereby reducing surface states and non-radiative recombination, and improving LOP and EQE. Alternatively, the side of the light-emitting device and / or the surface of the encapsulation layer away from the light-emitting device is subjected to trimethylaluminum (TMA) / nitrogen plasma surface treatment to reduce surface states and non-radiative recombination, which can increase forward current and voltage characteristics. Alternatively, hydrogen (H) ions can be used to form a second modification layer including hydride on the side of the light-emitting device and / or the surface of the encapsulation layer away from the light-emitting device, thereby inactivating the side defects of the light-emitting device, reducing reverse leakage current, and suppressing non-radiative recombination.

[0128] A method for preparing a light-emitting substrate provided in an embodiment of the present disclosure, as shown in FIG12 , includes:

[0129] S101, manufacturing each film layer of the light-emitting unit and the driving backplane;

[0130] S102, transferring each film layer of the light-emitting unit to a driving backplane, and performing a patterning process on each film layer of the light-emitting unit to form a plurality of light-emitting units;

[0131] S103, forming an encapsulation layer including at least one first modification layer; the encapsulation layer covers the side surface of the light-emitting unit and a portion of the surface of the light-emitting unit facing away from the driving backplane, and the first modification layer is used to passivate side defects of the light-emitting unit.

[0132] The embodiment of the present disclosure provides a method for preparing a light-emitting substrate, forming an encapsulation layer covering the side of the light-emitting unit, and the encapsulation layer includes a first modification layer. The first modification layer can passivate the defects on the side of the light-emitting unit, thereby reducing the defect state on the side of the light-emitting unit, reducing the probability of non-radiative recombination, and improving the radiation conformity efficiency, thereby improving the luminous efficiency of the light-emitting device and the luminous efficiency of the light-emitting substrate.

[0133] In some embodiments, manufacturing each film layer of the light-emitting unit specifically includes:

[0134] forming a buffer layer on the substrate;

[0135] An N-type semiconductor layer, a quantum well layer, and a P-type semiconductor layer are sequentially formed on a side of the buffer layer facing away from the substrate;

[0136] A first electrode layer and a second electrode layer are sequentially formed on a side of the P-type semiconductor layer facing away from the substrate.

[0137] In a specific implementation, the substrate is, for example, a sapphire substrate, and the buffer layer, the N-type semiconductor layer, the quantum well layer, and the P-type semiconductor layer include gallium nitride.

[0138] In some embodiments, manufacturing a driver backplane specifically includes:

[0139] A driving circuit layer is formed on the base substrate 101 .

[0140] Among them, the driving circuit layer includes: multiple bonding patterns, multiple transistors and multiple signal lines; the multiple signal lines include: data lines, scan lines and common electrode lines; the transistor includes: an active layer, a gate, a source and a drain, the data line is electrically connected to the source of the transistor, the scan line is electrically connected to the gate of the transistor, the bonding pattern is electrically connected to the drain, and the common electrode is electrically connected to the common electrode line.

[0141] In some embodiments, the film layers of the light-emitting units are transferred to a driving backplane, and the film layers of the light-emitting units are subjected to a non-uniform process to form a plurality of light-emitting units, as shown in FIG13 , specifically including:

[0142] S1021, transferring each film layer of the light-emitting unit 2 to the driving backplane 1, so that the second electrode layer 205 is bonded to the plurality of bonding patterns 102;

[0143] S1022, peeling off the substrate 7;

[0144] S1023, removing the buffer layer 8;

[0145] S1024, performing patterning processing on the N-type semiconductor layer 203, the quantum well layer 202, and the P-type semiconductor layer 201;

[0146] S1025 , performing patterning processing on the first electrode layer 204 and the second electrode layer 205 .

[0147] In some embodiments, before forming at least one first modification layer, the method further comprises:

[0148] A heat dissipation layer is formed.

[0149] In some embodiments, the heat dissipation layer is formed using an atomic deposition process.

[0150] It should be noted that the atomic deposition process deposits materials at the nanoscale, coating the substrate surface layer by layer in the form of a single atomic film. During the coating process, two or more chemical vapor precursors react sequentially on the substrate surface to produce a solid thin film. Experimental verification demonstrated that the I-shaped step shown in Figure 14 was covered using both the atomic deposition process and the chemical vapor deposition process. The morphology of a portion of the area is shown in Figure 15. The film layer coverage of the step was b / a. Al2O3 deposited to a thickness of 500 angstroms using the atomic deposition process had a step coverage of 89%, while Al2O3 deposited to a thickness of 1000 angstroms using the atomic deposition process had a step coverage of 99%. SiN deposited to a thickness of 6000 angstroms using the chemical vapor deposition process had a step coverage of 44%, and SiN deposited to a thickness of 12000 angstroms using the chemical vapor deposition process had a step coverage of 37%. The step coverage of the film layer formed by the atomic deposition process was greater than that of the film layer formed by the chemical vapor deposition process. The atomic deposition process can precisely control the thickness of the film layer. Compared with other deposition methods such as chemical vapor deposition, the film layer formed by the atomic deposition process has better morphology and structure, better film density, continuity, and conformality, and is free of void defects. The film layer formed by the atomic deposition process has a high coverage rate on the I-shaped steps. Therefore, the heat dissipation layer formed by the atomic deposition process has an excellent insulation effect on water and oxygen in the air. The good step coverage can achieve conformal coverage on various substrates, which can improve the packaging capability of the packaging layer.

[0151] In a specific implementation, when the material of the heat dissipation layer is Al2O3 or AlN, the heat dissipation layer can be formed by an atomic deposition process.

[0152] In some embodiments, the first modified layer is formed using an atomic deposition process or a chemical vapor deposition process. For example, when the material of the first modified layer is AlN, the first modified layer can be formed using an atomic deposition process; when the material of the first modified layer is SiO2, the first modified layer can be formed using a chemical vapor deposition process.

[0153] In a specific implementation, the heat dissipation layer is an AlN layer formed using an atomic deposition process, and the first modification layer is a SiO2 layer formed using a chemical vapor deposition process. A scanning electron microscope (SEM) image of the side coverage of the light-emitting device is shown in Figure 16. The thickness of the AlN layer in Figure 16 is 30 nm, and the thickness of the SiO2 layer is 200 nm.

[0154] In some embodiments, after forming at least one first modification layer, the method further comprises:

[0155] A light extraction layer is formed; the light extraction layer includes a plurality of light-transmitting sub-layers stacked together, and the refractive indices of any two adjacent light-transmitting sub-layers are different.

[0156] In some embodiments, forming a light extraction layer specifically includes:

[0157] A first light-transmitting sublayer, a second light-transmitting sublayer, and a third light-transmitting sublayer are sequentially formed on the side away from the first modified layer; wherein the material of the first light-transmitting sublayer includes SiO2, the material of the second light-transmitting sublayer includes Al2O3, and the material of the third light-transmitting sublayer includes SiN.

[0158] In some embodiments, before forming the encapsulation layer covering the plurality of light-emitting units, the method further includes:

[0159] forming a second modification layer on a side surface of the light emitting unit;

[0160] And / or, after forming the encapsulation layer covering the plurality of light-emitting units, the method further includes:

[0161] A second modification layer is formed on the surface of the encapsulation layer.

[0162] In some embodiments, forming a second modification layer on the side of the light-emitting unit specifically includes:

[0163] Performing vulcanization treatment on the side of the light-emitting unit;

[0164] Alternatively, the side surfaces of the light-emitting unit are surface treated using trimethylaluminum or nitrogen plasma;

[0165] Alternatively, hydrogen ions are used to perform surface treatment on the side surfaces of the light emitting unit.

[0166] In some embodiments, the side surfaces of the light-emitting unit are subjected to a sulfurization treatment, specifically comprising:

[0167] Clean the sides of the light-emitting unit with hydrochloric acid;

[0168] The structure including the light-emitting unit is placed on the polysulfide ammonium ((NH4)2S x ) solution for soaking.

[0169] In specific implementation, as shown in FIG17 , there are dangling bond defects on the side of the semiconductor layer of the light-emitting device. These dangling bonds can form surface states with O atoms in the air or solution (such as etching solution). When washed with hydrochloric acid, the H in the hydrochloric acid reacts with O to destroy the Ga-O bond, that is, the primary oxide layer on the side of the light-emitting unit can be removed. Then, (NH4)2S xThe solution is sulfurized. The sulfurization process provides sulfur atoms to bind to these dangling bonds, forming S-Ga bonds, which prevent the recombination of oxygen atoms. This can reduce surface states and non-radiative recombination, thereby improving electron injection efficiency and EQE. Compared with the case without sulfurization treatment, the EQE of the light-emitting device can be improved by 20%.

[0170] In some embodiments, a second modification layer is formed on the surface of the encapsulation layer.

[0171] The surface of the encapsulation layer is treated by using trimethylaluminum and nitrogen plasma;

[0172] Alternatively, the surface of the encapsulation layer is treated with hydrogen ions.

[0173] In practice, trimethylaluminum (TMA) and nitrogen plasma are used to surface treat the light-emitting device or encapsulation layer. TMA reacts with surface oxides to form Al2O3, while nitrogen removes carriers that damage surface trapped states. Because the light-emitting device is a Micro LED, which has a high perimeter-to-area ratio, the resulting surface-treated material exhibits a high surface recombination velocity, suppressing the Fermi level pinning effect and significantly reducing leakage current. For example, using GaInP as a semiconductor material, the AlGaInP material obtained by surface-treating the light-emitting device or encapsulation layer with TMA and nitrogen plasma exhibits a high surface recombination velocity.

[0174] In a specific implementation, hydrogen ions are used to perform surface treatment of the light-emitting device or the packaging layer for hydrogen passivation, which inactivates the surface of the P-type semiconductor layer. For smaller light-emitting devices, the reverse leakage current can be reduced by more than ten times, and due to the suppression of non-radiative recombination, the quantum efficiency of the light-emitting device can be increased by 1.4 times.

[0175] In some embodiments, after forming the encapsulation layer including at least one first finishing layer, the method further includes:

[0176] The packaging layer is patterned to form a plurality of first openings, wherein the first openings correspond to the light-emitting devices one by one, and the first openings expose a partial area of ​​the surface of the light-emitting device on a side away from the driving backplane.

[0177] It should be noted that, if the encapsulation layer is subjected to surface treatment to form the second modification layer, the encapsulation layer is subjected to a patterning process to form the plurality of first openings after the second modification layer is formed.

[0178] In some embodiments, after patterning the packaging layer to form a plurality of first openings, the method further includes:

[0179] A common electrode is formed.

[0180] A display device provided by an embodiment of the present disclosure, as shown in FIG18 , includes a light-emitting substrate 9 provided by an embodiment of the present disclosure.

[0181] The embodiment of the present disclosure provides a display device including the above-mentioned light-emitting substrate provided by the embodiment of the present disclosure, the light-emitting substrate includes an encapsulation layer covering the side of the light-emitting unit, and the encapsulation layer includes a first modification layer. The first modification layer can passivate the defects on the side of the light-emitting unit, thereby reducing the defect state on the side of the light-emitting unit, reducing the probability of non-radiative recombination, and improving the radiation conformity efficiency, thereby improving the luminous efficiency of the light-emitting device and the luminous efficiency of the light-emitting substrate.

[0182] In some embodiments, as shown in FIG18 , the display device further includes a display panel 10 located on the light emitting side of the light emitting substrate 9 .

[0183] In a specific implementation, the display panel is a liquid crystal display panel, that is, the light-emitting substrate serves as a backlight source of the liquid crystal display panel.

[0184] In some embodiments, as shown in FIG. 18 , the display panel 10 includes an array substrate 11 and an opposite substrate 12 that are oppositely disposed, and a liquid crystal layer 13 located between the array substrate 11 and the opposite substrate 12 .

[0185] In a specific implementation, the array substrate includes multiple thin film transistors and pixel electrodes electrically connected to the thin film transistors in a one-to-one correspondence, and may also include a common electrode. The opposite substrate includes a black matrix and a color filter. The black matrix has multiple opening areas, and the color filter is located at least in the opening area.

[0186] The display device provided in the embodiments of the present disclosure is any product or component with a display function, such as a mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, or navigation system. Other essential components of the display device are readily understood by those skilled in the art and are not described here in detail, nor should they be construed as limitations of the present disclosure. The implementation of the display device can be referenced to the aforementioned embodiments of the light-emitting substrate, and any repetitive details will be omitted.

[0187] In summary, the embodiments of the present disclosure provide a light-emitting substrate, a preparation method thereof, and a display device. The light-emitting substrate includes an encapsulation layer covering the side of the light-emitting unit, and the encapsulation layer includes a first modification layer. The first modification layer can passivate the defects on the side of the light-emitting unit, thereby reducing the defect state on the side of the light-emitting unit, reducing the probability of non-radiative recombination, and improving the radiation conformity efficiency, thereby improving the luminous efficiency of the light-emitting device and the luminous efficiency of the light-emitting substrate.

[0188] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0189] Obviously, those skilled in the art may make various changes and modifications to the present disclosure without departing from the spirit and scope of the present disclosure. Thus, if these modifications and variations of the present disclosure fall within the scope of the claims of the present disclosure and their equivalents, the present disclosure is intended to include these modifications and variations.

Claims

1. A light-emitting substrate, wherein: The light-emitting substrate comprises: Driver backplane; A plurality of light-emitting units are located on one side of the driving backplane; The encapsulation layer covers the side surface of the light-emitting unit and a part of the surface of the light-emitting unit away from the driving backplane; the encapsulation layer includes at least one first modification layer; the first modification layer is used to passivate the side defects of the light-emitting unit.

2. The light-emitting substrate according to claim 1, wherein: The encapsulation layer further comprises: The heat dissipation layer is located between the first modification layer closest to the light-emitting unit and the light-emitting unit; the heat dissipation layer includes a heat insulating material.

3. The light-emitting substrate according to claim 2, wherein: The material of the heat dissipation layer includes one of the following or a combination thereof: aluminum oxide, aluminum nitride, silicon oxide, and silicon nitride.

4. The light-emitting substrate according to any one of claims 1 to 3, wherein The material of the first modification layer includes one of the following or a combination thereof: silicon oxide, aluminum oxide, aluminum nitride, and silicon nitride.

5. The light-emitting substrate according to claim 4, wherein: The material of the heat dissipation layer is different from the material of the first modification layer adjacent thereto.

6. The light emitting substrate according to any one of claims 1 to 3 and 5, wherein: The encapsulation layer further comprises: The light extraction layer is located on a side of the first modification layer away from the light emitting unit.

7. The light-emitting substrate according to claim 6, wherein: The light extraction layer includes a plurality of light-transmitting sub-layers stacked in layers, and the refractive indices of any two adjacent light-transmitting sub-layers are different.

8. The light-emitting substrate according to claim 7, wherein: The multi-layer light-transmitting sub-layer comprises: a first light-transmitting sub-layer, a second light-transmitting sub-layer, and a third light-transmitting sub-layer which are sequentially stacked on a side away from the first modified layer; The material of the first light-transmitting sub-layer includes silicon oxide, the material of the second light-transmitting sub-layer includes aluminum oxide, and the material of the third light-transmitting sub-layer includes silicon nitride.

9. The light-emitting substrate according to any one of claims 1 to 3, 5, 7 and 8, wherein: The side surface of the light-emitting unit includes a second modification layer, and / or the surface of the encapsulation layer facing away from the light-emitting unit includes a second modification layer.

10. The light emitting substrate according to claim 9, wherein: The second modification layer includes one of the following: sulfide, aluminum compound, or hydride.

11. A method for preparing a light-emitting substrate, wherein: The method comprises: Manufacturing each film layer of the light-emitting unit and the driving backplane; Transferring each film layer of the light-emitting unit to the driving backplane, and performing a patterning process on each film layer of the light-emitting unit to form a plurality of light-emitting units; An encapsulation layer including at least one first modification layer is formed; the encapsulation layer covers the side surface of the light-emitting unit and a portion of the surface of the light-emitting unit away from the driving backplane, and the first modification layer is used to passivate side defects of the light-emitting unit.

12. The method according to claim 11, wherein: Before forming at least one first modification layer, the method further comprises: A heat dissipation layer is formed.

13. The method according to claim 11 or 12, wherein: After forming at least one first modification layer, the method further comprises: A light extraction layer is formed; the light extraction layer comprises a plurality of light-transmitting sub-layers stacked in layers, and the refractive indexes of any two adjacent light-transmitting sub-layers are different.

14. The method according to claim 11, wherein: Before forming the encapsulation layer covering the plurality of light-emitting units, the method further includes: forming a second modification layer on the side of the light-emitting unit; And / or, after forming the encapsulation layer covering the plurality of light-emitting units, the method further includes: A second modification layer is formed on the surface of the encapsulation layer.

15. The method according to claim 14, wherein: Forming a second modification layer on the side of the light-emitting unit specifically includes: Performing vulcanization treatment on the side surface of the light emitting unit; Alternatively, the side of the light-emitting unit is surface treated by using trimethylaluminum or nitrogen plasma; Alternatively, hydrogen ions are used to perform surface treatment on the side surfaces of the light emitting unit.

16. The method according to claim 14, wherein: Forming a second modification layer on the surface of the encapsulation layer The surface of the encapsulation layer is treated by using trimethylaluminum and nitrogen plasma; Alternatively, the surface of the encapsulation layer is treated with hydrogen ions.

17. A display device, wherein: The invention comprises the light emitting substrate according to any one of claims 1 to 10.

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