Display unit and display device

Abstract

The invention discloses a display unit and a display device. The display unit comprises four light-emitting units which are stacked in sequence; different light-emitting units have different light-emitting wavelengths, and each light-emitting unit comprises a first semiconductor layer, a light-emitting layer and a second semiconductor layer; the type of the first semiconductor layer is different from that of the second semiconductor layer. The display effect of the display unit can be improved.

Description

Technical Field

[0001] The present invention relates to the field of display technologies, and particularly to a display unit and a display device. Background Art

[0002] With the development of display technologies, the application of display units has become increasingly widespread, and correspondingly, the requirements for display units have also become higher and higher.

[0003] However, the display effect of existing display units is poor, which limits the further application of display units. Summary of the Invention

[0004] The present invention provides a display unit and a display device to improve the display effect of the display unit.

[0005] According to one aspect of the present invention, a display unit is provided. The display unit includes four light-emitting units stacked in sequence;

[0006] The light-emitting wavelengths of different light-emitting units are different. Each light-emitting unit includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer; the types of the first semiconductor layer and the second semiconductor layer are different.

[0007] Optionally, the light-emitting wavelength of the light-emitting unit close to the light-emitting surface of the display unit is less than the light-emitting wavelength of the light-emitting unit far from the light-emitting surface of the display unit.

[0008] Optionally, the four light-emitting units include a red light-emitting unit, a yellow light-emitting unit, a green light-emitting unit, and a blue light-emitting unit.

[0009] Optionally, in at least one pair of semiconductor layers, a periodic structure is provided on one side of any semiconductor layer close to the other semiconductor layer; wherein, the at least one pair of semiconductor layers includes two adjacent semiconductor layers belonging to different light-emitting units; the periodic structure includes a first layer and a second layer that are stacked and have different refractive indexes; the periodic structure is used to reflect the emitted light of the light-emitting unit on the side close to the light-emitting surface and transmit the emitted light of the light-emitting unit on the side far from the light-emitting surface.

[0010] Optionally, in two adjacent periodic structures, two epitaxial layers that are adjacent and belong to different periodic structures are bonded together.

[0011] Optionally, the two bonded epitaxial layers are made of the same material.

[0012] Optionally, an adhesive layer is provided between two adjacent periodic structures that belong to different light-emitting units, and the adhesive layer is used to bond the corresponding two periodic structures.

[0013] Optionally, the thickness of the bonding layer is greater than the thickness of any one of the corresponding two periodic structures; the difference between the refractive index of the bonding layer and the refractive index of the epitaxial layer with a lower refractive index in the corresponding periodic structure is less than a preset value.

[0014] According to another aspect of the present invention, a display unit is provided. The display unit includes at least two stacked light-emitting units with different light-emitting wavelengths. The light-emitting unit includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked in sequence. In at least one pair of semiconductor layers, a periodic structure is provided on one side of any semiconductor layer close to the other semiconductor layer. Among them, the at least one pair of semiconductor layers includes two adjacent semiconductor layers belonging to different light-emitting units. The periodic structure includes a first layer and a second layer stacked with different refractive indexes. The periodic structure is configured to reflect the emitted light of the light-emitting unit on the side close to the light-emitting surface and transmit the emitted light of the light-emitting unit on the side far from the light-emitting surface.

[0015] Optionally, in two adjacent periodic structures, two epitaxial layers adjacent and belonging to different periodic structures are bonded together.

[0016] Optionally, the two bonded epitaxial layers are made of the same material.

[0017] Optionally, a bonding layer is provided between two adjacent periodic structures belonging to different light-emitting units, and the bonding layer is used to bond the corresponding two periodic structures.

[0018] Optionally, the thickness of the bonding layer is greater than the thickness of any one of the corresponding two periodic structures; the difference between the refractive index of the bonding layer and the refractive index of the epitaxial layer with a lower refractive index in the corresponding periodic structure is less than a preset value.

[0019] According to another aspect of the present invention, a display device is provided. The display device includes the display unit as described above.

[0020] The technical solution of the embodiment of the present invention adopts a display unit including four light-emitting units stacked in sequence; the light-emitting wavelengths of different light-emitting units are different; the types of the first semiconductor layer and the second semiconductor layer are different. By stacking four light-emitting units, the workload of mass transfer can be reduced. At the same time, the coverage rate of the visible light band can be improved, thereby improving the display color gamut of the display unit. In addition, since the number of light-emitting units is relatively large, the brightness of the display unit can be increased, and thus the display effect of the display unit can also be improved.

[0021] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0023] Figure 1 Structural schematic diagram of a display unit provided by an embodiment of the present invention;

[0024] Figure 2 Another structural schematic diagram of a display unit provided by an embodiment of the present invention;

[0025] Figure 3 Another structural schematic diagram of a display unit provided by an embodiment of the present invention;

[0026] Figure 4 Another structural schematic diagram of a display unit provided by an embodiment of the present invention;

[0027] Figure 5 Schematic diagram of a product corresponding to the main steps of a preparation method of a display unit provided by an embodiment of the present invention;

[0028] Figure 6 Another structural schematic diagram of a display unit provided by an embodiment of the present invention;

[0029] Figure 7 Structural schematic diagram of a display device provided by an embodiment of the present invention. Detailed implementation manners

[0030] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0032] Figure 1 FIG. is a schematic structural diagram of a display unit provided by an embodiment of the present invention. Refer to Figure 1 , the display unit includes four light-emitting units stacked in sequence; the light-emitting wavelengths of different light-emitting units are different, and each light-emitting unit includes a first semiconductor layer, a light-emitting layer and a second semiconductor layer; the types of the first semiconductor layer and the second semiconductor layer are different.

[0033] Specifically, the light-emitting unit can be a Micro-LED (Micro Light Emitting Diode). Each light-emitting unit includes a first semiconductor layer, a light-emitting layer and a second semiconductor layer, and the semiconductor types of the first semiconductor layer and the second semiconductor layer are different, that is, one of them is an n-type semiconductor layer and the other is a p-type semiconductor layer. The light-emitting layer is, for example, a quantum well layer. When a forward voltage is applied to the light-emitting unit, electrons generated in the n-type semiconductor layer and holes generated in the p-type semiconductor layer recombine in the light-emitting layer to achieve the light-emitting function. By setting different light-emitting layers, the wavelength of the emitted light can be made different, that is, the colors of the emitted light of different light-emitting units can be made different. Exemplarily, the n-type semiconductor layer can be achieved by n-type doping. For example, silicon is doped in a gallium nitride material, and tetravalent silicon replaces trivalent gallium to generate electrons; the p-type semiconductor layer can be achieved by p-type doping. For example, magnesium is doped in a gallium nitride material, and divalent magnesium replaces trivalent gallium to generate holes. The light-emitting layer is, for example, a stacked structure of InGaN and GaN. As Figure 1As shown in the figure, the display unit 20 of this embodiment includes a first light-emitting unit 30, a second light-emitting unit 50, a third light-emitting unit 70, and a fourth light-emitting unit 90 stacked in sequence. The first light-emitting unit 30 includes a first first semiconductor layer 31, a first light-emitting layer 33, and a first second semiconductor layer 35 stacked in sequence. The second light-emitting unit 50 includes a second first semiconductor layer 51, a second light-emitting layer 53, and a second second semiconductor layer 55 stacked in sequence. The third light-emitting unit 70 includes a third first semiconductor layer 71, a third light-emitting layer 73, and a third second semiconductor layer 75 stacked in sequence. The fourth light-emitting unit 90 includes a fourth first semiconductor layer 91, a fourth light-emitting layer 93, and a fourth second semiconductor layer 95 stacked in sequence.

[0034] After the Micro-LEDs are fabricated, they need to be transferred to a substrate through a mass transfer method. Among them, a pixel driving circuit corresponding to the Micro-LEDs is provided on the substrate. The display of each light-emitting unit in the display unit is realized through the pixel driving circuit. In the related art, if each display unit only includes one light-emitting unit, in order to achieve full-color display, light-emitting units of various emission colors need to be transferred to the substrate through multiple mass transfer methods. In this embodiment, the display unit is provided to include four light-emitting units, and the emission wavelengths of the four light-emitting units are different. During mass transfer, light-emitting units of multiple colors can be transferred to the substrate simultaneously through a smaller number of mass transfer times, thereby greatly reducing the workload of mass transfer and further improving the yield.

[0035] In addition, in traditional display units, at most three colors of light-emitting units are stacked. Since the wavelength band of visible light is relatively long, the wavelength band of visible light covered by the three-color light-emitting units is also relatively narrow, resulting in a problem of poor display color gamut in traditional display units. In this embodiment, the display unit is provided to include four light-emitting units with different wavelengths, which can improve the coverage rate of the visible light wavelength band, and further greatly improve the display color gamut of the display unit, and further improve the display effect. In addition, stacking four light-emitting units, compared with traditional display units, the number of light-emitting units is larger, which is also beneficial to improving the brightness of the display unit.

[0036] The technical solution of this embodiment adopts a display unit including four light-emitting units stacked in sequence; the emission wavelengths of different light-emitting units are different. By stacking four light-emitting units, the workload of mass transfer can be reduced. At the same time, it can also improve the coverage rate of the visible light wavelength band, and further improve the display color gamut of the display unit. In addition, the larger number of light-emitting units can also improve the brightness of the display unit, and further improve the display effect of the display unit.

[0037] Optionally, in some embodiments, such as Figure 1As shown, the wavelength of the light-emitting unit near the light-emitting surface of the display unit is smaller than the light-emitting wavelength of the light-emitting unit far from the light-emitting surface of the display unit. In other words, along the light-emitting direction X of the display unit, the wavelength of the light-emitting unit closer to the light-emitting surface of the display unit is smaller. When the wavelength is shorter, the energy is greater. In this embodiment, the light-emitting unit with greater energy is arranged closer to the light-emitting surface of the display unit, so that the light with greater energy can pass through a smaller number of light-emitting units, thereby avoiding the influence of the light with greater energy on the performance of other light-emitting units, which may lead to a reduction in the service life of the light-emitting unit. That is, the setting of this embodiment can improve the service life of the display unit.

[0038] Exemplarily, as Figure 1 shown, the four light-emitting units include a red light-emitting unit, a yellow light-emitting unit, a green light-emitting unit, and a blue light-emitting unit. Preferably, the first light-emitting unit 30 is a red light-emitting unit, that is, the emitted light is red; the second light-emitting unit 50 is a yellow light-emitting unit, that is, the emitted light is yellow; the third light-emitting unit 70 is a green light-emitting unit, that is, the emitted light is green; the fourth light-emitting unit 90 is a blue light-emitting unit, that is, the emitted light is blue. The wavelengths of the emitted light of the four light-emitting units in this embodiment are evenly distributed in the visible light band, which can achieve a better display color gamut. And the manufacturing process is relatively mature and the cost is low, so it can further improve the yield of the display unit and reduce the cost of the display unit.

[0039] Optionally, Figure 2 is a schematic structural diagram of another display unit provided by an embodiment of the present invention, refer to Figure 2 . In at least one pair of semiconductor layers, a periodic structure is provided on one side of any semiconductor layer close to the other semiconductor layer; wherein, at least one pair of semiconductor layers includes two adjacent semiconductor layers belonging to different light-emitting units; the periodic structure includes a first layer and a second layer that are stacked and have different refractive indexes; the periodic structure is used to reflect the emitted light of the light-emitting unit on the side close to the light-emitting surface and transmit the emitted light of the light-emitting unit on the side far from the light-emitting surface.

[0040] Specifically, the periodic structure is used to reflect the emitted light of its operating wavelength and transmit the light of other wavelengths. In this embodiment, the periodic structure is arranged to reflect the emitted light of the light-emitting units on the side close to the light-emitting surface and transmit the emitted light of the light-emitting units on the side far from the light-emitting surface. The periodic structure can reflect the emitted light of the light-emitting units on the side close to the light-emitting surface and transmit the emitted light of the light-emitting units on the side far from the light-emitting surface. One side of the periodic structure is the side close to the light-emitting surface of the display unit, and the other side is the side far from the light-emitting surface of the display unit. In other words, for the light-emitting units located on the side of the periodic structure close to the light-emitting surface, the light emitted by the light-emitting units along the direction away from the light-emitting surface of the display panel will be reflected by the periodic structure and then emitted through the light-emitting surface of the display unit, which can improve the light-emitting efficiency of the light-emitting units. In addition, the periodic structure can transmit the emitted light of the light-emitting units on the side far from the light-emitting surface of the display unit, so it will not reduce the light-emitting efficiency of other light-emitting units. The periodic structure includes a first layer and a second layer arranged in a stacked manner. The periodic structure can include multiple first layers and multiple second layers, and a Bragg reflection layer is formed by alternating arrangements. The Bragg reflection layer can reflect the light of its operating wavelength and transmit the light of other wavelengths. Typically, the operating wavelength of the Bragg reflection layer can be adjusted by adjusting at least one of the thickness of the first layer, the refractive index of the first layer, the thickness of the second layer, and the refractive index of the second layer.

[0041] In addition, in this embodiment, the periodic structure is composed of a first layer and a second layer and is in contact with the semiconductor layer. The first layer, the second layer, and the corresponding semiconductor layer can be formed by epitaxial growth, that is, the periodic structure can be fabricated by the process of manufacturing the light-emitting units, so the manufacturing process can be simplified. At this time, the first layer and the second layer can be epitaxial layers. Of course, in some other embodiments, the first layer and the second layer can also be film layers with an adhesive function.

[0042] Certainly, when the reflection band of the periodic structure is short, or when a periodic structure is arranged between any two light-emitting units, the periodic structure can be arranged to only reflect the emitted light of the light-emitting unit adjacent to it and located on the side close to the light-emitting surface of the display unit, and transmit the emitted light of the light-emitting unit on the side far from the light-emitting surface of the display unit, so as to improve the reflection efficiency and further improve the light-emitting efficiency of the display unit.

[0043] It should be noted that Figure 2In the middle, a first periodic structure 34 is provided on the first second semiconductor layer 34, and a second periodic structure 54 is correspondingly provided on the second first semiconductor layer 51; a third periodic structure 56 is correspondingly provided on the second second semiconductor layer 55; a fourth periodic structure 74 is correspondingly provided on the third first semiconductor layer 71; a fifth periodic structure 76 is correspondingly provided on the third second semiconductor layer 75; and a sixth periodic structure 94 is correspondingly provided on the fourth first semiconductor layer 94 as an example. The first periodic structure 34 and the second periodic structure 54 are provided in pairs; the third periodic structure 56 and the fourth periodic structure 74 are provided in pairs; the fifth periodic structure 76 and the sixth periodic structure 94 are provided in pairs. At least one pair of the three pairs of periodic structures is provided. The first periodic structure 34 includes a first first layer 341 and a first second layer 342 stacked; the second periodic structure 54 includes a first first layer 541 and a first second layer 542 stacked; the third periodic structure 56 includes a third first layer 561 and a first third epitaxial layer 562 stacked; the fourth periodic structure 74 includes a fourth first layer 741 and a fourth second layer 742 stacked; the fifth periodic structure 76 includes a fifth first layer 761 and a fifth second layer 762 stacked; the sixth periodic structure 94 includes a sixth first layer 941 and a sixth second layer 942 stacked.

[0044] Optionally, as Figure 2 shown, in two adjacent periodic structures, two epitaxial layers that are adjacent and belong to different periodic structures are bonded together.

[0045] Specifically, in this embodiment, the first layer can be, for example, titanium dioxide, and the second layer can be, for example, silicon dioxide. By bonding the epitaxial layers that are adjacent and belong to different periodic structures respectively, the periodic structures can be closely connected, thereby fixedly connecting different light-emitting units and improving the stability of the display unit structure. In addition, the two closely connected periodic structures are equivalent to an integral periodic structure. Compared with two independent periodic structures, the reflectivity of the working wavelength is higher, thereby further improving the light extraction efficiency of the display unit. It can be understood that the two can be bonded in a bonding device.

[0046] In some embodiments, the bonding can be hetero-bonding, that is, the materials of the two epitaxial layers to be bonded are different.

[0047] In other embodiments, the materials of the two epitaxial layers to be bonded are the same, and at this time, homo-bonding can be achieved, and the bonding effect is better. More preferably, the two epitaxial layers to be bonded are both silicon dioxide, which has a better bonding effect than titanium dioxide. Based on this, the layer of each periodic structure that is farthest from the corresponding light-emitting layer is a silicon dioxide layer. As Figure 2As shown, in this embodiment, when the first layer and the second layer appear in pairs, in the corresponding two periodic structures, along the direction of approaching each other, the arrangement order of the epitaxial layers is the first layer, the second layer, the first layer, the second layer... or it can also be the opposite arrangement. Or in some other embodiments, if the outermost layer of the epitaxial layers arranged in pairs is not a silicon dioxide layer, a silicon dioxide layer can be additionally provided.

[0048] Optionally, Figure 3 is a schematic structural diagram of another display unit provided by an embodiment of the present invention. Refer to Figure 3 , an adhesive layer is provided between two adjacent periodic structures belonging to different light-emitting units, and the adhesive layer is used to bond the corresponding two periodic structures.

[0049] Specifically, in this embodiment, the periodic structures are not connected by bonding two epitaxial layers, but by using an adhesive layer, and the adhesive layer bonds two adjacent periodic structures respectively. With such a setting, the periodic structures do not need to be bonded, so the material selection range is wider. And there is no need to use bonding equipment for bonding, which is also beneficial to cost reduction.

[0050] Exemplarily, as Figure 3 shown, the first periodic structure 34 and the second periodic structure 54 are bonded by the first adhesive layer 40. The third periodic structure 56 and the fourth periodic structure 74 are bonded by the second adhesive layer 60. The fifth periodic structure 76 and the sixth periodic structure 94 are bonded by the third adhesive layer 80.

[0051] The material of the adhesive layer is, for example, epoxy resin, polyimide, SU8 photoresist, spin-on glass, and benzocyclobutene BCB.

[0052] Optionally, in some embodiments, the thickness of the adhesive layer is greater than the thickness of any one of the corresponding two periodic structures, so as to achieve a better bonding effect.

[0053] Optionally, the difference between the refractive index of the adhesive layer and the refractive index of the epitaxial layer with a lower refractive index in the corresponding periodic structure is less than a preset value. The refractive index of the adhesive layer can be the same as or close to the refractive index of the adhesive layer with a lower refractive index in the two adjacent periodic structures (the difference is within 5% of the refractive index of the corresponding epitaxial layer). With such a setting, the influence of the adhesive layer on the light reflection effect and light transmission effect of the periodic structure can be further reduced.

[0054] It should be noted that an electrode structure may be provided between different light-emitting units. The manufacturing method of the electrode structure may be to etch part of the periodic structure to expose the corresponding semiconductor layer, and then fabricate an electrode on the semiconductor layer. Additionally, although in the figure, the lateral dimension of each light-emitting unit (the width from left to right in the figure) is taken as an example to be the same, it is not limited thereto. For example, the lateral dimension of the first light-emitting unit may be greater than that of the second light-emitting unit, the lateral dimension of the second light-emitting unit may be greater than that of the third light-emitting unit, and the lateral dimension of the third light-emitting unit may be greater than that of the fourth light-emitting unit. Moreover, in two adjacent light-emitting units, the two opposite semiconductor layers may be semiconductor layers of the same type or different types, and this embodiment does not make specific limitations in this regard. In some other embodiments, the materials of the first layer in different periodic structures may be the same or different; the materials of the second layer in different periodic structures may be the same or different. And the total number of epitaxial layers in different periodic structures may be the same or different.

[0055] An embodiment of the present invention further provides a display unit. As Figure 4 shown, Figure 4 is a schematic structural diagram of another display unit provided by an embodiment of the present invention. The display unit 20 includes at least two stacked light-emitting units. In this embodiment, the first light-emitting unit 30 and the second light-emitting unit 50 are taken as examples. The light-emitting wavelengths of different light-emitting units are different; the light-emitting unit includes a first semiconductor layer and a second semiconductor layer stacked in sequence; in at least one pair of semiconductor layers, a periodic structure is provided on one side of any semiconductor layer close to the other semiconductor layer; wherein, at least one pair of semiconductor layers includes two adjacent semiconductor layers belonging to different light-emitting units; the periodic structure includes a first layer and a second layer that are stacked and have different refractive indexes; the periodic structure is configured to reflect the emitted light of the light-emitting unit close to the light-emitting surface side and transmit the emitted light of the light-emitting unit far from the light-emitting surface side.

[0056] Specifically, the periodic structure is used to reflect the outgoing light of its operating wavelength. In this embodiment, the periodic structure is arranged to reflect the outgoing light of the light-emitting units on the side close to the light-emitting surface and transmit the outgoing light of the light-emitting units on the side far from the light-emitting surface. The periodic structure can reflect the outgoing light of the light-emitting units on the side close to the light-emitting surface and transmit the outgoing light of the light-emitting units on the side far from the light-emitting surface. One side of the periodic structure is the side close to the light-emitting surface of the display unit, and the other side is the side far from the light-emitting surface of the display unit. In other words, for the light-emitting units located on the side of the periodic structure close to the light-emitting surface, the light emitted by the light-emitting unit along the direction away from the light-emitting surface of the display panel will be reflected by the periodic structure and then emitted through the light-emitting surface of the display unit, which can improve the light-emitting efficiency of the light-emitting unit. In addition, the periodic structure can transmit the outgoing light of the light-emitting units on the side far from the light-emitting surface of the display unit, so it will not reduce the light-emitting efficiency of other light-emitting units. The periodic structure includes a first layer and a second layer arranged in a stacked manner. The periodic structure can include multiple first layers and multiple second layers, and a Bragg reflection layer is formed by alternating settings. The Bragg reflection layer can reflect the light of its operating wavelength and transmit the light of other wavelengths. Typically, the operating wavelength of the Bragg reflection layer can be adjusted by adjusting at least one of the thickness of the first layer, the refractive index of the first layer, the thickness of the second layer, and the refractive index of the second layer.

[0057] Of course, when the reflection band of the periodic structure is short, or when a periodic structure is arranged between any two light-emitting units, the periodic structure can be arranged to only reflect the outgoing light of the light-emitting unit adjacent to it and on the side close to the light-emitting surface of the display unit and transmit the outgoing light of the light-emitting unit on the side far from the light-emitting surface of the display unit, so as to improve the reflection efficiency and further improve the light-emitting efficiency of the display unit.

[0058] In addition, in this embodiment, the periodic structure is composed of a first layer and a second layer and is in contact with the semiconductor layer. The first layer, the second layer, and the corresponding semiconductor layer can be formed by epitaxial growth, that is, the periodic structure can be fabricated through the process of fabricating the light-emitting units, so the fabrication process can be simplified.

[0059] Optionally, as Figure 4 shown, in two adjacent periodic structures, two epitaxial layers that are adjacent and belong to different periodic structures are bonded together.

[0060] Specifically, in this embodiment, the first layer can be, for example, titanium dioxide, and the second layer can be, for example, silicon dioxide. By setting adjacent epitaxial layers belonging to different periodic structures to be bonded, the periodic structures can be tightly connected, thereby fixedly connecting different light-emitting units and improving the stability of the display unit structure. Additionally, the two tightly connected periodic structures are equivalent to an integral periodic structure, which has a higher reflectivity for the working wavelength compared to two independent periodic structures, thus further improving the light extraction efficiency of the display unit. It can be understood that the two can be bonded in a bonding device.

[0061] In some embodiments, the bonding can be hetero-bonding, that is, the materials of the two epitaxial layers to be bonded are different.

[0062] In other embodiments, the materials of the two epitaxial layers to be bonded are the same, and in this case, homo-bonding can be achieved with a better bonding effect. More preferably, both of the two epitaxial layers to be bonded are silicon dioxide, which has a better bonding effect compared to titanium dioxide. Based on this, the outermost layer of each periodic structure that is farthest from the corresponding light-emitting layer is a silicon dioxide layer. As Figure 4 shown, in this embodiment, when the first layer and the second layer appear in pairs, in the two corresponding periodic structures, along the direction of approaching each other, the arrangement order of the epitaxial layers is the first layer, the second layer, the first layer, the second layer... or it can also be the opposite arrangement. Or in some other embodiments, if the outermost layer of the epitaxial layers arranged in pairs is not a silicon dioxide layer, an additional silicon dioxide layer can be provided.

[0063] Optionally, Figure 5 is a schematic diagram of the product corresponding to the main steps of a preparation method of a display unit provided by an embodiment of the present invention. Refer to Figure 5. The manufacturing method of the display unit includes: First, a semiconductor layer, a light-emitting layer, a semiconductor layer, and a periodic structure may be sequentially grown on a corresponding substrate 100. It should be noted that at this time, one semiconductor layer of the light-emitting unit is adjacent to the substrate, and no periodic structure is provided between the two. Only a periodic structure is formed on the semiconductor layer of the light-emitting unit away from the substrate. Based on this, the growth effect of the semiconductor layer can be better, and thus the yield can be further improved. This step forms various light-emitting units with substrate structures, such as forming a first light-emitting unit and a second light-emitting unit respectively. Subsequently, bond two periodic structures that need to be bonded. Subsequently, remove the substrate 100 of the light-emitting unit close to the light-emitting surface of the display unit, and retain the substrate of the light-emitting unit farthest from the light-emitting surface of the display unit. That is, retain the substrate corresponding to the first light-emitting unit and remove the substrate of the second light-emitting unit, so as to ensure that the display unit has substrate support during the manufacturing process. Subsequently, grow a periodic structure on the semiconductor layer exposed by the light-emitting unit after removing the substrate, that is, grow a corresponding periodic structure on the second semiconductor layer 55 of the second light-emitting unit 50. And so on, finally bond the four light-emitting units together. Finally, remove the substrate corresponding to the first light-emitting unit.

[0064] Optionally, Figure 6 is a schematic structural diagram of another display unit provided by an embodiment of the present invention. Refer to Figure 6 , there is an adhesive layer between two periodic structures that are adjacent and belong to different light-emitting units, and the adhesive layer is used to bond the corresponding two periodic structures.

[0065] Specifically, in this embodiment, the periodic structures are not connected by bonding two epitaxial layers, but by using an adhesive layer, and the adhesive layer bonds two adjacent periodic structures respectively. With this setting, the periodic structures do not need to be bonded, so the material selection range is wider. And there is no need to use bonding equipment for bonding, which is also beneficial to reducing costs.

[0066] Of course, Figure 6 The manufacturing method of the display unit shown can refer to Figure 5 , the difference is only that the bonding process is replaced by forming an adhesive layer and bonding, and the remaining steps will not be described in detail here.

[0067] An embodiment of the present invention also provides a display device, as Figure 7 shown, Figure 7Schematic structural diagram of a display device provided by an embodiment of the present invention. The display device includes a substrate 10 and a plurality of display units provided by any embodiment of the present invention. The display device is formed by transferring a large number of display units 20 onto the substrate 10. The substrate 10 includes a plurality of pixel driving circuits for driving corresponding light-emitting units. The display units 20 are arranged in an array on the substrate 10. The display device may be a mobile phone, a tablet computer, an MP3, an MP4, a smart watch, a smart helmet, a video phone, or a personal digital assistant, etc. The manufacturing method of the display unit in this embodiment is relatively simple, and the workload and difficulty of the large-scale transfer are relatively low. Therefore, the manufacturing difficulty and workload of the display device are also relatively low. In addition, the display unit is a Micro-LED, which has the characteristics of small size, high integration, and self-luminescence, and has greater advantages in terms of brightness, resolution, contrast, energy consumption, service life, response speed, and thermal stability compared with LCD (Liquid Crystal Display) and OLED (Organic Light Emitting Diode) in terms of display.

[0068] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0069] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A display unit, characterized in that, The display unit includes four light-emitting units stacked in sequence; The light emitted by different light-emitting units has different wavelengths. Each light-emitting unit includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer; the types of the first semiconductor layer and the second semiconductor layer are different.

2. The display unit according to claim 1, characterized in that, The light-emitting wavelength of the light-emitting unit close to the light-emitting surface of the display unit is less than that of the light-emitting unit far from the light-emitting surface of the display unit.

3. The display unit according to claim 1, wherein The four light-emitting units include a red light-emitting unit, a yellow light-emitting unit, a green light-emitting unit, and a blue light-emitting unit.

4. The display unit according to claim 1, wherein In at least one pair of semiconductor layers, a periodic structure is provided on one side of any semiconductor layer close to the other semiconductor layer; wherein, the at least one pair of semiconductor layers includes two adjacent semiconductor layers belonging to different light-emitting units; the periodic structure includes a first layer and a second layer that are stacked and have different refractive indexes; the periodic structure is used to reflect the outgoing light of the light-emitting unit on the side close to the light-emitting surface and transmit the outgoing light of the light-emitting unit on the side far from the light-emitting surface.

5. The display unit according to claim 4, wherein An adhesive layer is provided between two periodic structures that are adjacent and belong to different light-emitting units, and the adhesive layer is used to bond the corresponding two periodic structures.

6. The display unit according to claim 5, wherein The thickness of the adhesive layer is greater than the thickness of any one of the corresponding two periodic structures; the difference in refractive index between the adhesive layer and the epitaxial layer with a lower refractive index in the corresponding periodic structure is less than a preset value.

7. A display unit, characterized in that, The display unit includes at least two light-emitting units stacked, and the light-emitting wavelengths of different light-emitting units are different; the light-emitting unit includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked in sequence; in at least one pair of semiconductor layers, a periodic structure is provided on one side of any semiconductor layer close to the other semiconductor layer; wherein, the at least one pair of semiconductor layers includes two adjacent semiconductor layers belonging to different light-emitting units; the periodic structure includes a first layer and a second layer that are stacked and have different refractive indexes; the periodic structure is used to reflect the outgoing light of the light-emitting unit on the side close to the light-emitting surface and transmit the outgoing light of the light-emitting unit on the side far from the light-emitting surface.

8. The display unit according to claim 7, characterized in that An adhesive layer is provided between two periodic structures that are adjacent and belong to different light-emitting units, and the adhesive layer is used to bond the corresponding two periodic structures.

9. The display unit according to claim 8, wherein The thickness of the adhesive layer is greater than the thickness of any one of the corresponding two periodic structures; the difference in refractive index between the adhesive layer and the epitaxial layer with a lower refractive index in the corresponding periodic structure is less than a preset value.

10. A display device, characterized in that, The display device includes the display unit according to any one of claims 1-9.

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