WO2023134552A1 - Display panel and electronic device - Google Patents

Abstract

Embodiments of the present application relate to the technical field of display, and provide a display panel and an electrode device, capable of improving the light-emitting efficiency of display panels. The display panel comprises a light-emitting unit; the light-emitting unit comprises a bottom reflective layer, a light-emitting device, a middle reflective layer, a color conversion layer, and a reflective packaging layer which are sequentially stacked; the bottom reflective layer, the light-emitting device, and the middle reflective layer form a first micro-cavity; the middle reflective layer, the color conversion layer, and the reflective packaging layer form a second micro-cavity; the color conversion layer is an organic material layer; the color conversion layer comprises a host material for absorbing light and a guest material for emitting light; the range of the concentration of the guest material in the host material is 0.5%-30%; and the range of the thickness of the color conversion layer is 60-600 nm.

Description

Display panels and electronics

This application claims the priority of a Chinese patent application with application number 202210050853.0 and application title “Display Panel and Electronic Device” filed with the China Patent Office on January 17, 2022, the entire contents of which are incorporated herein by reference.

technical field

The present application relates to the field of display technology, in particular to a display panel and electronic equipment.

Background technique

With the development of display technology, the display resolution is getting higher and higher. Micro-inorganic light-emitting diode Micro-LED technology is a technology that miniaturizes LEDs to achieve active image display. For Micro-LED, a single light-emitting device can reach a sub-micron size, so it is suitable for use as an ultra-high-resolution display panel. However, as the resolution of the display panel increases, the size of a single light-emitting device decreases, especially LEDs that emit light at long wavelengths, such as red LEDs, have a sharp drop in luminous efficiency as the size decreases.

Contents of the invention

A display panel and electronic equipment that can improve the luminous efficiency of the display panel.

In a first aspect, a display panel is provided, comprising: a light-emitting unit, the light-emitting unit includes a bottom reflective layer, a light-emitting device, a middle reflective layer, a color conversion layer, and a reflective packaging layer stacked in sequence, and the light-emitting device is an inorganic light-emitting device; the bottom reflector The first microcavity is formed by the layer, the light-emitting device and the middle reflective layer, and the second microcavity is formed by the middle reflective layer, the color conversion layer and the reflective encapsulation layer; the color conversion layer is an organic material layer, and the color conversion layer includes a host material for light absorption and The guest material used for luminescence; the concentration range of the guest material in the host material is 0.5%-30%; the thickness range of the color conversion layer is 60-600nm.

In a possible implementation manner, the color conversion layer has a thickness ranging from 200nm to 400nm.

In a possible implementation, the host material includes two host components.

In a possible implementation manner, the concentration of any host component in the host material ranges from 30% to 70%.

In a possible implementation, the concentration of one of the two host components in the host material ranges from 10% to 30%.

In a possible implementation manner, the concentration of the guest material in the host material is in the range of 0.5% to 5%; the emission wavelength of the host material and the light absorption wavelength of the guest material overlap.

In a possible implementation manner, the concentration of the guest material in the host material ranges from 5% to 30%.

In a possible implementation manner, the host material is a luminescent material.

In a possible implementation, the host material includes coumarin C545T or coumarin 6.

In a possible implementation manner, the display panel further includes: a circuit layer, the circuit layer is located on the side of the bottom reflective layer away from the color conversion layer; the bottom reflective layer includes a first electrode plate, a second electrode plate and a distributed Bragg reflector Structural plate; one of the first electrode plate and the second electrode plate is the anode electrode plate of the light emitting device, and the other of the first electrode plate and the second electrode plate is the cathode electrode plate of the light emitting device.

In a possible implementation manner, the distributed Bragg reflector structure plate extends from the side of the light emitting device away from the color conversion layer to the side of the light emitting device.

In a possible implementation manner, the display panel further includes: a circuit layer, the circuit layer is located on the side of the bottom reflective layer away from the color conversion layer; one of the bottom reflective layer and the middle reflective layer is the anode electrode plate of the light emitting device, and the bottom reflective layer The other of the reflection layer and the middle reflection layer is a cathode electrode plate of the light emitting device.

In a possible implementation, the reflective encapsulation layer extends from the side of the color conversion layer away from the light-emitting device to the surface of the circuit layer to form a groove facing the circuit layer, and the bottom reflection layer, the light-emitting device, the middle reflection layer and the color conversion The layers are located within the grooves.

In a possible implementation manner, the light-emitting unit is a red light-emitting unit, and the color conversion layer is a red color conversion layer; the display panel further includes a blue light-emitting unit, and the blue light-emitting unit includes a bottom reflective layer, a blue light-emitting device and reflective encapsulation layers.

In a possible implementation manner, the display panel further includes a green light-emitting unit, and the green light-emitting unit includes a bottom reflective layer, a light-emitting device, a middle reflective layer, a green color conversion layer, and a reflective encapsulation layer that are sequentially stacked.

In a possible implementation manner, the display panel further includes a green light-emitting unit, and the green light-emitting unit includes a bottom reflective layer, a green light-emitting device, and a reflective encapsulation layer that are sequentially stacked.

In a possible implementation manner, the display panel includes a plurality of light-emitting units; the color conversion layers of the plurality of light-emitting units are an integrated color conversion layer, and the integrated color conversion layer is also located between the light-emitting devices of any two light-emitting units. Between; the reflective encapsulation layers of the plurality of light emitting units are integrated and located on the surface of the color conversion layer of the integrated structure.

In a possible implementation manner, the display panel includes a plurality of light-emitting units; the display panel further includes: a leveling layer, the leveling layer is located between the light-emitting devices of any two light-emitting units; the color conversion layer of the plurality of light-emitting units is an integrated structure The color conversion layer of the integrated structure is also located on the side of the flat layer away from the circuit layer; the reflective packaging layers of the multiple light emitting units are integrated and located on the surface of the color conversion layer of the integrated structure.

In a possible implementation manner, the display panel includes a plurality of light emitting units, and the central reflective layers in each light emitting unit are electrically connected to each other.

In a second aspect, an electronic device is provided, including the above-mentioned display panel.

In the display panel and the electronic device in the embodiment of the present application, in the color conversion layer, the light-absorbing host material cooperates with the light-emitting guest material to realize rapid energy transfer, thereby reducing the probability of quenching and improving the luminous efficiency; in addition, The energy transfer mode that the color conversion layer depends on, the color conversion layer can be set to a thickness range of 0-600nm, so as to cooperate with the first microcavity and the second microcavity to realize the modulation of the color output light and improve the light output efficiency; in addition, due to the The color conversion layer realized by organic materials has low luminous purity, and the light modulation of the first microcavity and the second microcavity can improve the purity of the light; in addition, the thinner color conversion layer can also improve the poor light shape, The problem of blurred pixels.

Description of drawings

FIG. 1 is a schematic cross-sectional structure diagram of a partial area of a display panel in an embodiment of the present application;

Fig. 2 is a schematic diagram of material distribution of a color conversion layer in the embodiment of the present application;

Fig. 3 is a schematic diagram of the energy relationship of a color conversion layer in the embodiment of the present application;

Fig. 4 is a schematic diagram of the energy relationship of another color conversion layer in the embodiment of the present application;

Fig. 5 is a schematic diagram of the energy relationship of another color conversion layer in the embodiment of the present application;

FIG. 6 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 7 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

Fig. 8 is a schematic diagram of the preparation process of a light-emitting device in the embodiment of the present application;

FIG. 9 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 10 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

Fig. 11 is a schematic diagram of the preparation process of another light-emitting device in the embodiment of the present application;

FIG. 12 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 13 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 14 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 15 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 16 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 17 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 18 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application;

FIG. 19 is a schematic cross-sectional structure diagram of another partial area of a display panel in an embodiment of the present application.

Detailed ways

The terms used in the embodiments of the present application are only used to explain specific embodiments of the present application, and are not intended to limit the present application.

Before introducing the embodiments of the present application, the technical problems of related technologies are described first. In related technologies, the size of a single light-emitting device decreases, especially for long-wavelength LEDs. As the size decreases, the luminous efficiency drops sharply. Related technologies include the use of a color conversion layer to cooperate with light-emitting devices to achieve color display. If the concentration of the color conversion material in the color conversion layer is high, it is easy to cause poor luminous efficiency due to quenching; if the color conversion layer in the color conversion layer A lower concentration of the conversion material will lead to a decrease in the light-absorbing ability of the color conversion layer. Therefore, a thicker color conversion layer is required, and a thicker color conversion layer will adversely affect the light shape of the light emission and cause pixel blurring. In order to solve the above problems, the present application provides the following embodiments, and the following embodiments of the present application will be described below.

As shown in FIG. 1 , the embodiment of the present application provides a display panel, including: a light emitting unit 10, the light emitting unit 10 includes a bottom reflective layer 11, a light emitting device 12, a middle reflective layer 13, a color conversion layer 14 and Reflective encapsulation layer 15 . The light emitting device 12 is an inorganic light emitting device, namely an inorganic light emitting diode LED. The bottom reflective layer 11, the light emitting device 12 and the middle reflective layer 13 form the first microcavity 101, the light emitting device 12 is used to emit light, and the first microcavity 101 is a short-wave light emitting cavity, which can improve the luminous efficiency of the light emitting device 12 and improve the shape of light emitting light. , Reduce the half-peak width of luminescence. The middle reflective layer 13 , the color conversion layer 14 and the reflective encapsulation layer 15 form a second microcavity 102 . The middle reflective layer 13 has both functions in the first microcavity 101 and the second microcavity 102, and it can be a single layer of reflective film, or a stack of two or more reflective films. Since the middle reflective layer 13 belongs to two microcavities at the same time and functions in the two microcavities respectively, it is beneficial to reduce the thickness of the light emitting unit 10 .

The color conversion layer 14 is an organic material layer. As shown in FIGS. 2 and 3 , the color conversion layer 14 includes a host material 141 for light absorption and a guest material 142 for light emission; 0.5% to 30%, the content of the host material 141 relative to the guest material 142 is relatively large, and forms a relationship of energy transfer downward with the guest material 142, and the host material 141 has an absorption wavelength that matches the emission wavelength of the first microcavity 101, The light emitted by the first microcavity 101 can be effectively absorbed, and the energy absorbed by the host material 141 is quickly transferred to the guest material through the energy transfer mechanism. Since the energy stays on the host material 141 for a short time, the probability of quenching is reduced ; The thickness range of the color conversion layer 14 is 60-600nm. It should be noted that the concentration in the examples of the present application refers to the mass concentration. The embodiment of the present application may have two ways of selecting the guest material, and the two ways of selecting the guest material will be described below.

In the first method of selecting the guest material, the absorption wavelength of the guest material 142 matches the emission wavelength of the host material 141. The matching here means that the two have a certain degree of overlap in the spectrum, that is, the emission wavelength of the host material 141 and the emission wavelength of the host material 141 match. The light absorption wavelengths of the guest materials 142 overlap. At this time, since the light absorption wavelength of the guest material 142 does not need to match the light emitting wavelength of the light emitting device 12, it only needs to match the light emitting wavelength of the host material 141, so the guest material 142 can have a lower concentration in the host material 141, and a For effective energy transfer, for example, the concentration range of the guest material 142 in the host material 141 is 0.5%-5%.

In the second guest material selection method, the concentration range of the guest material 142 in the host material 141 is 5% to 30%, and the energy transfer method that the second guest material selection method depends on is the direct transfer of energy received by the host material 141 to the object material 142 within a very close range, so wavelength matching is not required, and there are more types of object materials 142 to choose from.

Compared with the second guest material selection mode, the first guest material selection mode has a lower concentration of the guest material 142 , so the probability of quenching of the color conversion layer 14 is lower. It can be seen that the energy transfer methods corresponding to the above two guest material selection methods have their own advantages and disadvantages. Specifically, they should be selected according to the common reference of the host material 141, the guest material 142, and the light emission spectrum of the first microcavity 101 and the light emission spectrum of the second microcavity 102. .

In the color conversion layer 14, the light emitted by the first microcavity 101 is absorbed by the host material 141 accounting for the main proportion, so the thickness requirement for the color conversion layer 14 is relatively low. By controlling the thickness of the color conversion layer 14, the second The optical path of the two microcavities 102 is controlled, so as to selectively enhance specific emission wavelengths.

The calculation method of the optical path is shown in the formula: s(λ)=∑l _i ×n _i (λ).

Wherein s(λ) is the optical length corresponding to the wavelength λ, l _i is the length corresponding to the i-th layer medium in the second microcavity 102, and n _i (λ) is the refractive index of the i-th layer medium corresponding to the wavelength λ. When the optical length s(λ) is equal to an integer multiple of the half-wavelength λ/2, it can enhance the intensity of light of the corresponding wavelength. In the design of the second microcavity 102, the middle reflective layer 13 and the reflective encapsulation layer 15 on both sides thereof have a certain reflective ability for a specific wavelength, so that they can be used to enhance the generated light of the target wavelength. Calculated according to the wavelength corresponding to the color of the light used by the display panel, when the thickness of the color conversion layer 14 is in the range of 60-600 nm, the light emitted by the second microcavity 102 can be modulated and enhanced.

In addition, the reflective film layers such as the bottom reflective layer 11, the middle reflective layer 13, and the reflective encapsulation layer 15 can realize reflection through materials with intrinsic reflective ability, or by controlling the difference in refractive index of the media on both sides of the reflective film layer. reflection. When light travels from a medium with a high refractive index to a medium with a low refractive index, the greater the difference in refractive index between the two, the stronger the reflected light. Of course, these reflective film layers themselves can also be formed by selecting one or more pairs of materials with a certain difference in refractive index, so as to increase the reflectivity.

In the display panel in the embodiment of the present application, in the color conversion layer, the light-absorbing host material cooperates with the light-emitting guest material to realize rapid energy transfer, thereby reducing the probability of quenching and improving the luminous efficiency; in addition, the color conversion layer Depending on the energy transfer method, the color conversion layer can be set to a thickness range of 0-600nm, so as to cooperate with the first microcavity and the second microcavity to realize the modulation of the color output light and improve the light output efficiency; in addition, due to the realization of The light emission purity of the color conversion layer is low, and the light modulation of the first microcavity and the second microcavity can improve the purity of the light; in addition, the thinner color conversion layer can also improve the poor light shape and pixel blur The problem.

In some embodiments, the host material 141 includes two host components. That is to say, in the embodiment of the present application, the host material 141 does not necessarily consist of a single material. The concept of the host mainly comes from its role in the energy conversion mechanism For example, two different organic materials can be mixed, and the two materials respectively contribute to the effective energy level of the host (different from the real energy level of a single material).

In some embodiments, as shown in FIG. 4 , for example, the host material 141 includes a host component m1 and a host component m2, wherein the host component m1 contributes a deeper energy level, and the host component m2 contributes a deeper energy level. Shallow energy levels, the combination of the two forms the effective energy level of the host material 141 . In this case, the concentration range of any one of the host components in the host material 141 is 30% to 70%, that is, the concentrations of m1 and m2 are roughly equivalent in magnitude. In this way, the combination of host materials 141 can be effectively used to modulate the host the absorption spectrum.

In some embodiments, as shown in FIG. 5 , the host material 141 includes the host component m1 and the host component m2, which is different from the above-mentioned mixing method of the host material 141, wherein the host component m1 directly absorbs the emitted energy from the first microcavity 101. The light of , transfers energy to the main component m2. This method utilizes the different characteristics of m1 and m2 to avoid the energy loss caused by spin prohibition during the energy conversion process, thereby improving the energy conversion efficiency; in addition, using m2 as an intermediate material to match the emission wavelength of m1 and the object The absorption wavelength of the material 142 is beneficial to transfer energy by using the aforementioned first guest material selection method. In such a mixing method of the host material 141 , the ratio of the two host components may vary considerably, and the concentration of one of the two host components in the host material 141 ranges from 10% to 30%.

It should be noted that, besides being a single material or being formed by mixing two kinds of main components, the main material 141 can further increase the types of components, but generally the main material 141 is composed of one or two kinds of materials mixed.

In some embodiments, the host material 141 is a luminescent material. In the prior art, some light-emitting devices use host materials and guest materials to cooperate to achieve light emission, but the host materials generally choose non-luminescent materials, such as 1,3-bis(N-carbazolyl)benzene mCP, etc., these The material is characterized by a large band gap, so the absorption peak is generally at the position of 300nm or even shorter wavelength, and the light absorption ability is low. Therefore, in the embodiment of the present application, the host material 141 can be selected from common light-emitting materials, such as coumarin C545T and coumarin 6 (Coumarin6), which have higher absorption efficiency when absorbing light from the light-emitting device 12, and have tropism The ability of other guest materials to transfer energy. In addition, since the main body material 141 occupies a large proportion, it has a strong light absorption ability, which can improve the light leakage problem.

In some embodiments, the host material 141 can be selected from coumarin-based materials, such as coumarin C545T, coumarin 6 (Coumarin6), etc.; triphenylamine (Triphenylamine, TPA)-based materials, such as 9,1-bis[ N,N-di(p-tolyl)amino]anthracene TTPA, etc.; and dichloromethane (Dichloromethane, DCM), NAI-DMAC, PTZ-DCPP, N,N'-dimethylquinacridone (N,N '-Dimethylquinacridone, DMQA) and other materials. These materials have greater advantages in absorbing short-wave luminescence, and have the ability to transfer energy to other guest materials, so they are suitable as the host material 141 of the embodiment of the present application; similarly, thermally activated delayed fluorescence (Thermally Activated Delayed Fluorescence, Materials with TADF characteristics such as tetrabromophenolphthalein ethyl ester potassium salt (Tetrabromophenolphthalein ethyl ester, TBPe), ACRSA, t-DABNA, v-DABNA, etc. may also be used as the host material 141 . At the same time, as mentioned above, in addition to acting as the host material 141 alone, the above materials can also form mixed host materials with other host materials or with each other, and use the aforementioned energy mechanism to absorb light and transmit energy. In addition to the above small molecules, poly(9,9-dioctylfluorene-co-dithiophene) alternating copolymer F8T2, 9,9-dioctylfluorene-benzothiadiazole copolymer F8BT, and polyparaphenylene Ethylene PPV-based materials can also be used as the host material, such as BEHP-CO-MEH-PPV, poly[2-methoxy-5-(3`,7`-dimethyloctyloxy)-1,4 -Phenylenevinylene]MDMO-PPV, poly(2,5-dioctyl-1,4-phenylenevinyl)POPPV and poly[2,5-bis(triethoxymethoxy)-1,4 -Phenylacetylene] BTEM-PPV and other polymers.

In some embodiments, the guest material 142 may include fluorescent materials such as coumarin C545T and DCJTB; TADF materials such as TmCzTrz, TBRb, and APDC-DTPA. In addition, phosphorescent materials such as Ir-based and Pt-based materials may be used as the guest material 142 of the color conversion layer 14 . The guest material 142 can effectively utilize the energy absorbed by the host material as long as it satisfies the aforementioned energy transfer relationship. For example, when the host material 141 is C545T, the guest material 142 can be a material other than C545T.

In some embodiments, as shown in FIG. 6 , the display panel further includes: a circuit layer 2, the circuit layer 2 is located on the side of the bottom reflective layer 11 away from the color conversion layer 14, and the circuit layer 2 has a driving circuit for realizing the control. Control of the light emitting device 12; the bottom reflection layer 11 includes a first electrode plate 111, a second electrode plate 112 and a distributed Bragg reflector (distributed Bragg reflector, DBR) structure plate 113; the first electrode plate 111 and the second electrode plate 112 One of them is an anode electrode plate of the light emitting device 12 , and the other of the first electrode plate 111 and the second electrode plate 112 is a cathode electrode plate of the light emitting device 12 . Wherein, the light-emitting device 12 can be realized by using flip-chip technology Flip Chip, that is, the anode electrode plate and the cathode electrode plate of the light-emitting device 12 are located on the same side of the light-emitting device 12, wherein the first electrode plate 111 and the second electrode plate 112 can be The metal electrode plate is used to connect the light emitting device 12 to the circuit in the circuit layer 2 , and the metal electrode plate and the DBR structure plate 113 can jointly form the bottom reflective layer 11 . The central reflective layer 13 may also be composed of a DBR structure formed by SiN _x /SiO _x stacks, and the reflective encapsulation layer 15 may also be formed by a DBR structure formed by SiN _x /SiO _x stacks.

In some embodiments, the distributed Bragg reflector structure plate 113 extends from the side of the light-emitting device away from the color conversion layer 14 to the side of the light-emitting device 12. This structure can provide converging light emission while passivating the light-emitting device 12. role.

In some embodiments, the reflective encapsulation layer 15 extends from the side of the color conversion layer 14 away from the light-emitting device 12 to the surface of the circuit layer 2 to form a groove facing the circuit layer 2. The bottom reflective layer 11, the light-emitting device 12, and the middle reflector Layer 13 and color converting layer 14 are located in the groove. That is, the reflective encapsulation layer 15 can cover the color conversion layer 14 from the side. Therefore, the process for preparing the reflective encapsulation layer 15 should have certain conformal characteristics, so as to prevent water vapor from radiating the organic material in the color conversion layer 14 from the side. At this time, the reflective encapsulation layer 15 can be prepared by an atomic layer deposition (Atomic layer deposition, ALD) process or a chemical vapor deposition (chemical vapor deposition, CVD) process, especially an ALD process with better shape retention.

In some embodiments, as shown in FIG. 7, when the conformality of the process for preparing the reflective encapsulation layer 15 is not enough to protect the color conversion layer 14, a certain gap can be reserved around the color conversion layer 14 for reflection. The encapsulation layer 15 only covers the color conversion layer 14 . In this case, there is a higher requirement on the patterning precision of each film layer, but there are more process options for the reflective encapsulation layer 15 .

The main component of the color conversion layer 14 is an organic photoelectric material, so its preparation method can use physical deposition processes such as evaporation, so that the film thickness can be better controlled. In addition, in some possible embodiments, a wet process, such as spin coating, coating, inkjet printing and other processes, can also be used to prepare the color conversion layer 14 . Thin films prepared by wet process are easier to be patterned by photolithography and other schemes.

In some embodiments, as shown in FIG. 8 , the fabrication process of a flip-chip Flip Chip light-emitting diode (light-emitting diode, LED) as the light-emitting device 12 is illustrated below:

Step S11 , growing inorganic light-emitting diode LED epitaxy, such as an epitaxial structure based on GaN-based materials, on a temporary substrate. This process can be realized by metal-organic chemical vapor deposition (Metal-organic Chemical Vapor Deposition, MOCVD) process or physical vapor deposition (Physical Vapor Deposition, PVD) and other processes. A complete epitaxial structure may include multiple layers with similar or different components, as well as possible microstructures, etc., which will not be described in detail here;

Step S12: Etching the epitaxial structure on the temporary substrate into one/multiple independent mesas to form the light-emitting device 12. During the etching process, the sidewalls of the mesas can be etched to have a certain angle according to requirements. appearance;

Step S13 , preparing a passivation layer 16 on the mesa formed by etching. The passivation layer 16 may use a stack of SiN _x /SiO _x material pairs to form a DBR. The DBR can passivate and protect the mesas of the light emitting device 12 and at the same time provide the function of concentrating light. At the same time, the passivation layer 16 is also one of the components of the bottom reflective layer 11;

Step S14, patterning and etching the passivation layer 16 to form openings on the surface of the passivation layer 16;

Step S15 , preparing the metal first electrode plate 111 and the second electrode plate 112 to realize the electrical connection of the mesas of the light emitting device 12 and also provide part of the reflective function of the bottom reflective layer 11 .

After completing the preparation of the light-emitting diode through steps S11-S15, the device needs to be inverted and bonded to the actual carrying substrate (circuit layer 2). The carrier substrate may be a substrate with a strip-shaped cathode and anode, or a substrate with (Thin Film Transistor, TFT) or complementary metal-oxide-semiconductor (Complementary Metal-Oxide-Semiconductor, CMOS). After bonding, it can be etched and other methods to remove the temporary base. During the LED growth process, in order to balance the stress and control the growth orientation, a sacrificial epitaxial layer may be included in the epitaxial structure. After bonding, these redundant epitaxial parts can be etched away as required.

It should be noted that in the LED, the two metal electrode plates as the cathode electrode plate and the anode electrode plate should be deposited in different subdivision layers of the LED epitaxial structure, as shown in FIG. 9, specifically, for example, the first electrode plate 111 is deposited On the P-type semiconductor layer or the P-type conductive layer in the light-emitting device 12 ; and the second electrode plate 112 is deposited on the N-type semiconductor layer or the N-conductive layer in the light-emitting device 12 . In order to avoid LED short circuit, the surrounding of the second electrode plate 112 can be filled with insulating material, and finally the side surface of the second electrode plate 112 is covered with a passivation layer to avoid short circuit between the first electrode plate 111 and the second electrode plate 112 . In some cases, the passivation layer itself may also function as an insulation.

For example, for a blue LED, the light-emitting device 12 is used to emit blue light, and the passivation layer 16, the first electrode plate 111 and the second electrode plate 112 can gather the light generated by the light-emitting device 12 to exit toward the direction of the color conversion layer 14, Light of the target color is formed after passing through the color conversion layer. The strong blue light absorption ability of the color conversion layer 14 and the light adjustment ability of each reflection layer help to further reduce residual blue light and improve color purity and conversion efficiency. And because the thinner color conversion layer 14 is used, the microcavity effect can be used in the color conversion layer 14 to further increase the absorption ratio of short-wavelength light (such as blue light) and adjust the final light color and light shape. In a display panel with higher resolution, when the width of the light-emitting device 12 is smaller, for example, less than 5 μm, the thickness of the color conversion layer 14 is more feasible in process, and the side light leakage is improved.

In some embodiments, as shown in FIG. 10 , the display panel further includes: a circuit layer 2 located on the side of the bottom reflective layer 11 away from the color conversion layer 14; one of the bottom reflective layer 11 and the middle reflective layer 13 It is the anode electrode plate of the light-emitting device 12, and the other of the bottom reflective layer 11 and the middle reflector layer 13 is the cathode electrode plate of the light-emitting device 12, that is, a vertical light-emitting diode Vertical LED can be used as the light-emitting device 12.

Specifically, when a Vertical LED is used as the light-emitting device 12, the anode electrode plate and the cathode electrode plate of the light-emitting device 12 can have a larger area, and in extreme cases, the bottom reflective layer 11 can have the same size as the lower surface of the entire LED. Sometimes the bottom reflective layer 11 itself can be used as the bottom electrode of the LED; the middle reflective layer 13 can directly use a top electrode with a certain reflective ability, for example, a metal material or indium tin oxide ITO material can be used.

As shown in Figure 11, the preparation process of Vertical LED and Flip Chip LED is similar, and the preparation process of Vertical LED includes:

Step S21, growing inorganic light-emitting diode LED epitaxy on the temporary substrate;

Step S22, etching the epitaxial structure on the temporary substrate into one/multiple independent mesas by etching, so as to form the light emitting device 12;

Step S23 , preparing a passivation layer 16 on the mesa formed by etching. The passivation layer 16 may use a stack of SiN _x /SiO _x material pairs to form a DBR. The DBR can passivate and protect the mesas of the light emitting device 12, and at the same time provide the function of converging light emission;

Step S24, patterning and etching the passivation layer 16 to form an opening on the surface of the passivation layer 16;

Step S25, preparing a metal bottom reflective layer 11 to realize the electrical connection of the LED mesa and also provide a reflective function. The bottom reflective layer 11 can cover the entire bottom surface of the light emitting device 12, or only cover a part of the bottom surface of the light emitting device 12.

After completing the preparation of the Vertical LED through steps S21-S25, the device needs to be inverted and bonded to the actual carrier substrate (circuit layer 2). After bonding, the temporary substrate is removed by etching or other methods, and then the middle reflective layer 13 can be prepared. In addition, it is also possible to epitaxially bond the LED to the carrier substrate first, and then etch to form the mesa, that is, first perform step S22 and then perform step S21. In addition, the middle reflective layer 13 can be electrically connected to the circuit layer 2 at the bottom by climbing; the middle reflective layer 13 can also form the electrode structure of the entire middle reflective layer 13, and connect the circuit at the bottom through a via hole at a local position. The circuits of layer 2 are electrically connected; the middle reflective layer 13 can also be directly drawn out from the edge of the display panel.

It should be noted that although the figure shows that the middle reflective layer 13 is in contact with the color conversion layer 14, this is only a functional illustration. In an actual structure, the surface of the middle reflective layer 13 may also have a transparent passivation layer and other functional materials. At this time, the central reflective layer 13 is a composite structure composed of multiple film layers. Similarly, the same situation may also exist for the reflective encapsulation layer 15 and the bottom reflective layer 11 .

The Vertical LED structure can increase the arrangement density of LEDs and improve the resolution under phase process precision. At the same time, the electrodes of the Vertical LED itself act as a reflective layer, which helps to simplify the device structure, reduce process difficulty and device thickness.

In some embodiments, as shown in FIG. 12 , the above light emitting unit 10 is a red light emitting unit R, and the color conversion layer in the red light emitting unit R is a red color conversion layer 14R; the display panel also includes a blue light emitting unit B, a blue light emitting unit B The light emitting unit B includes a bottom reflective layer 11 , a blue light emitting device 12B and a reflective encapsulation layer 15 which are sequentially stacked. The display panel also includes a green light-emitting unit G. The green light-emitting unit G includes a bottom reflective layer 11, a light-emitting device 12, a middle reflective layer 13, a green color conversion layer 14G, and a reflective encapsulation layer 15 that are sequentially stacked. The light-emitting units of different colors form a display Array of light-emitting cells in the panel to achieve color display.

Among them, for the blue light-emitting unit B, directly use the blue light-emitting device 12B to emit light natively; The blue light emitting device 12 cooperates with the red color conversion layer 14R to realize red light emission. In the red light emitting unit R, the blue light emitting unit B and the green light emitting unit G, the LEDs have the same structure, for example, they all include a bottom reflective layer 11, a light emitting device 12 and a middle reflective layer 13, so these layers can be passed through the same Process flow preparation, wherein the light-emitting device 12 can be the same blue light-emitting device, and then, fabricate the patterned color conversion layer in the light-emitting unit of the corresponding color, such as the green color conversion layer 14G and the red color conversion layer 14R, after that, can The entire light emitting unit array is packaged, and a reflective packaging layer 15 is formed on the surface of each light emitting unit. At this time, the reflective encapsulation layer 15 and the middle reflective layer 13 have the same effect on the blue light-emitting unit B, therefore, when preparing the overall middle reflective layer 13, you can choose not to prepare the middle reflective layer 13 in the blue light-emitting unit B . Since the luminous efficiency of the red light-emitting unit decreases significantly after miniaturization, the problem of low luminous efficiency can be improved by providing a color conversion layer only for the light-emitting unit of a specific color and cooperating with a double microcavity structure.

In some embodiments, as shown in FIG. 13 , the display panel further includes a green light-emitting unit G, and the green light-emitting unit G includes a bottom reflective layer 11 , a green light-emitting device 12G and a reflective encapsulation layer 15 stacked in sequence. That is to say, for the blue light-emitting unit B, directly use the blue light-emitting device 12B to emit light natively; for the green light-emitting unit G, directly use the green light-emitting device 12G to emit light natively; The color conversion layer 14R realizes red light emission.

In some embodiments, the thickness of the color conversion layer 14 is in the range of 200-400 nm. For the wavelengths corresponding to green and red, based on the calculation formula of the optical path, the corresponding thickness of the color conversion layer 14 can be calculated in the range of 200-400 nm.

In the structures shown in FIG. 12 and FIG. 13 , the LED is a Flip Chip structure. In some embodiments, as shown in FIG. 14 , the Vertical LED structure can also be applied in a color display structure. For example, for the blue light-emitting unit B, directly use the blue light-emitting device 12B to emit light natively, for the red light-emitting unit R, use the red color conversion layer 14R to realize red light emission, and for the green light-emitting unit G, use the green color conversion layer 14G to realize green light. glow.

In some embodiments, as shown in FIG. 15 , the display panel includes a plurality of light emitting units 10, the color conversion layer 14 in each light emitting unit 10 is a color conversion layer of the same color, for example, the color conversion layer 14 in each light emitting unit 10 The conversion layer 14 is a red color conversion layer, that is, the plurality of light emitting units 10 on the display panel are all red light emitting units, so as to realize a monochromatic light emitting unit array. When preparing a monochromatic light emitting unit array, due to the use of the same material Therefore, it is not necessary to pattern the color conversion layer 14. In some cases, the color conversion layer 14 can be prepared by evaporation and other processes. Starting from the circuit layer 2, therefore, after the color conversion layer 4 is evaporated, a corresponding break will be formed at the position of the LED mesa, that is, the part of the color conversion layer 14 will be formed on the LED mesa, and the part of the color conversion layer 14 will be formed on the LED mesa. Between the LED mesas, at this time, the reflective encapsulation layer 15 can be selected to be packaged in a better shape-retaining encapsulation method for overall encapsulation, so as to achieve effective encapsulation and protection for the color conversion layer 14 corresponding to each light emitting unit 10 . Of course, it can be understood that the color conversion layer 14 corresponding to each light emitting unit 10 can also be manufactured in a patterned manner, so that the color conversion layer 14 can be partially encapsulated.

In other embodiments, when the color conversion layer 14 is prepared by a wet process, due to the self-leveling properties of the liquid, a structure as shown in FIG. 16 may be formed. At this time, the display panel includes a plurality of light-emitting units 10; The color conversion layer 14 of each light emitting unit 10 is a color conversion layer 14 of an integral structure, and the color conversion layer 14 of an integral structure is also located between the light emitting devices 12 of any two light emitting units 10; the reflective encapsulation layer 15 of a plurality of light emitting units 10 It has an integral structure and is located on the surface of the color conversion layer 14 of the integral structure. During the process, due to its self-leveling effect, the color conversion layer 14 can be filled between different light emitting devices 12 and cover the LEDs in the light emitting unit 10 to protect the LEDs and flatten the surface. , since the upper surface of the color conversion layer 14 is flat, the process requirements for the reflective encapsulation layer 15 are relatively low. Effective encapsulation protection of the conversion layer 14.

In some embodiments, as shown in FIG. 17 , the display panel includes a plurality of light emitting units 10; the display panel further includes: a smoothing layer 17, and the smoothing layer 17 is located between the light emitting devices 12 of any two light emitting units 10; a plurality of light emitting units The color conversion layer 14 of the unit 10 is an integrated color conversion layer 14, and the integrated color conversion layer 14 is also located on the side of the flattening layer 17 away from the circuit layer 2; the reflection encapsulation layer 15 of the plurality of light emitting units 10 is an integrated structure, And it is located on the surface of the color conversion layer 14 of the integrated structure. That is to say, after the bottom reflective layer 11, the light-emitting device 12 and the middle reflective layer 13 are fabricated, before preparing the color conversion layer 14, a smoothing layer 17 is added between the LEDs to form the smoothing layer 17 and the middle reflective layer 13. The color conversion layer 14 is then fabricated on a relatively flat plane, so that the color conversion layer 14 can be continuously deposited on the surface of the LED array on a relatively flat plane. In addition, the leveling layer 17 itself can be set to have a strong reflective ability. In this way, there is no need to add an additional reflective structure on the side of the LED, and better side reflection can also be formed to reduce energy waste caused by light emitted from the side of the light emitting device 12 .

In some embodiments, as shown in FIG. 18 , the display panel includes a plurality of light-emitting units 10. After the bottom reflective layer 11 and the light-emitting devices 12 are manufactured, before preparing the middle reflective layer 13, add Flattening layer 17, so that flattening layer 17 and light-emitting device 12 form a relatively flat plane, and form a via hole on the flattening layer 17, and then make the middle reflective layer 13, and the middle reflective layer 13 in each light-emitting unit 10 is electrically connected to each other , the central reflective layer 13 connected together is electrically connected to the circuit layer 2 at the bottom through the via hole on the planarization layer 17, wherein the central reflective layer 13, the color conversion layer 14 and the reflective encapsulation layer 15 can be deposited continuously and flatly Preparation, the process requirements for these three layers are relatively low. The central reflective layer 13 can be used as a common electrode of LEDs in each light emitting unit 10 .

It should be noted that the display panels in some of the above embodiments are monochrome display panels, but this does not mean that the final product can only achieve monochrome display. For example, multiple monochrome display panels of different colors can be used. With some optical configurations, color display can also be realized. For example, by using blue display panels, green display panels and red display panels, together with components such as light combining prisms, the light rays of corresponding pixels in different color display panels can be combined, thereby Realize color display.

In some embodiments, as shown in FIG. 19 , for a display panel including light emitting units of different colors, the leveling layer 17 can also be provided to reduce the difficulty of subsequent processes. The display panel includes a blue light emitting unit B, a green light emitting unit G and a red light emitting unit R, wherein each light emitting unit includes a bottom reflective layer 11, a light emitting device 12, a middle reflective layer 13 and a reflective encapsulation layer 15 stacked in sequence. The green light-emitting unit G further includes a green color conversion layer 14G located between the middle reflective layer 13 and the reflective encapsulation layer 15 , and the red light-emitting unit R further includes a red color conversion layer 14R located between the middle reflective layer 13 and the reflective encapsulation layer 15 . The light-emitting device 12 is a blue light-emitting device. For the blue light-emitting unit B, directly use the blue light-emitting device 12 to emit light natively. For the green light-emitting unit G, the blue light-emitting device 12 and the green color conversion layer 14G cooperate to realize green light emission. For The red light emitting unit R realizes red light emission through cooperation of the blue light emitting device 12 and the red color conversion layer 14R. The central reflective layers 13 in each light emitting unit are electrically connected to each other. The leveling layer 17 is located between the central reflective layer 13 and the circuit layer 2 , and is also located between any adjacent light emitting devices 12 . After preparing the bottom reflective layer 11 and the light-emitting device 12, before preparing the middle reflective layer 13, add a smoothing layer 17, so that the smoothing layer 17 and the light-emitting device 12 form a relatively smooth plane, and then prepare the middle reflective layer 13, the middle reflective layer 13 is electrically connected to the circuit on the circuit layer 2 through the process on the leveling layer 17 . The leveling layer 17 provides a relatively smooth surface for the patterned color conversion layer, thereby facilitating the preparation of the color conversion layer. Moreover, since the thickness of the color conversion layer is relatively thin, it is beneficial to the subsequent manufacturing of the reflective encapsulation layer 15 , and the climbing height of the reflective encapsulation layer 15 is relatively low.

In some embodiments, the bottom reflective layer 11 and the middle reflective layer 13 can be conductive materials with reflective ability, such as aluminum, silver, copper, gold, magnesium, nickel, titanium, and other metals and their alloys; Highly conductive metal oxides. In addition, the bottom reflective layer 11 and the middle reflective layer 13 may also be a combination of a transparent electrode and a DBR. In addition, if parts of the bottom reflective layer 11 and the middle reflective layer 13 do not need to provide electrical conductivity, they may only be DBR or a material pair with a large difference in refractive index.

In some embodiments, the reflective encapsulation layer 15 is a composite laminate with a relatively large refractive index difference, such as a laminate composed of a SiNx/SiOx material pair, a laminated layer composed of a TiO2/Al2O3 material pair, or it may be Si, Ti, Oxygen/nitride combination of Al, Zr, Zn and other elements.

In some embodiments, the light emitting device 12 is a GaN-based blue light emitting device, and the light emitting device 12 may also be a semiconductor light emitting device formed of other inorganic materials. For the display panel in the embodiment of the present application, for the long-wavelength light-emitting device, the host material for light absorption and the guest material for light emission are provided to realize the color conversion layer, and the quenching problem is improved by energy transfer to improve the light emission. efficiency, and the color conversion layer has a smaller thickness through the combination of the host material and the guest material. The color conversion layer with a smaller thickness can cooperate with the double microcavity structure to achieve light modulation. On the one hand, it can improve the color conversion layer due to the organic material. The resulting problem of poor luminous purity, on the other hand, can further improve luminous efficiency.

In some embodiments, sputtering, electron beam evaporation, CVD, ALD and other processes can be selected for the processes involved in the production of oxides and nitrides in the embodiments of the present application, and sputtering is preferred when high conformality is required and ALD process. The light emitting device 12 can be fabricated by epitaxial process such as MOCVD, PVD, molecular beam epitaxy (MBE). The color conversion layer 14 can adopt vacuum coating processes such as thermal evaporation and electron beam evaporation, and can be prepared by wet processes such as coating, spin coating, scraping coating, and inkjet printing; its patterning can be based on its specific suitability, and can be This is accomplished using dry or wet etching. The metal thin film can be prepared by sputtering, evaporation and other processes.

In some embodiments, on the basis of LEDs, other devices with optical functions may be added to the display panel as a supplement to light modulation.

An embodiment of the present application further provides an electronic device, including the display panel in any of the foregoing embodiments. The specific structure and principle of the display panel are the same as those of the above-mentioned embodiments, and will not be repeated here. Specifically, the electronic device may be a mobile phone, a computer, an AR/VR electronic product, and the like.

In the embodiments of the present application, "at least one" means one or more, and "multiple" means two or more. "And/or" describes the association relationship of associated objects, indicating that there may be three types of relationships, for example, A and/or B, which may indicate the existence of A alone, the existence of A and B at the same time, or the existence of B alone. Among them, A and B can be singular or plural. The character "/" generally indicates that the contextual objects are an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, and c may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, and c may be single or multiple.

The above are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims (20)

1. A display panel, characterized in that it comprises:

   A light-emitting unit, the light-emitting unit comprising a bottom reflective layer, a light-emitting device, a middle reflective layer, a color conversion layer, and a reflective encapsulation layer stacked in sequence, and the light-emitting device is an inorganic light-emitting device;

   The bottom reflective layer, the light emitting device and the middle reflective layer form a first microcavity, and the middle reflective layer, the color conversion layer and the reflective encapsulation layer form a second microcavity;

   The color conversion layer is an organic material layer, and the color conversion layer includes a host material for light absorption and a guest material for light emission;

   The concentration of the guest material in the host material ranges from 0.5% to 30%;

   The thickness range of the color conversion layer is 60-600nm.
2. The display panel according to claim 1, characterized in that,

   The thickness range of the color conversion layer is 200-400nm.
3. The display panel according to claim 1, characterized in that,

   The host material includes two host components.
4. The display panel according to claim 3, characterized in that,

   The concentration of any one of the host components in the host material ranges from 30% to 70%.
5. The display panel according to claim 3, characterized in that,

   The concentration of one of the two host components in the host material ranges from 10% to 30%.
6. The display panel according to claim 1, characterized in that,

   The concentration of the guest material in the host material ranges from 0.5% to 5%;

   The emission wavelength of the host material and the absorption wavelength of the guest material overlap.
7. The display panel according to claim 1, characterized in that,

   The concentration of the guest material in the host material ranges from 5% to 30%.
8. The display panel according to claim 1, characterized in that,

   The host material is a luminescent material.
9. The display panel according to claim 8, wherein,

   The host material includes coumarin C545T or coumarin 6.
10. The display panel according to claim 1, further comprising:

    a circuit layer, the circuit layer is located on the side of the bottom reflection layer away from the color conversion layer;

    The bottom reflection layer includes a first electrode plate, a second electrode plate and a distributed Bragg reflector structure plate;

    One of the first electrode plate and the second electrode plate is an anode electrode plate of the light emitting device, and the other of the first electrode plate and the second electrode plate is the light emitting device the cathode electrode plate.
11. The display panel according to claim 10, wherein,

    The distributed Bragg reflector structure plate extends from a side of the light emitting device away from the color conversion layer to a side of the light emitting device.
12. The display panel according to claim 1, further comprising:

    a circuit layer, the circuit layer is located on the side of the bottom reflection layer away from the color conversion layer;

    One of the bottom reflective layer and the middle reflective layer is an anode electrode plate of the light emitting device, and the other of the bottom reflective layer and the middle reflective layer is a cathode electrode plate of the light emitting device.
13. The display panel according to any one of claims 10 to 12, characterized in that,

    The reflective encapsulation layer extends from the side of the color conversion layer away from the light-emitting device to the surface of the circuit layer, forming a groove facing the circuit layer, the bottom reflective layer, the light-emitting device, the The middle reflective layer and the color conversion layer are located in the groove.
14. The display panel according to any one of claims 10 to 13, characterized in that,

    The light emitting unit is a red light emitting unit, and the color conversion layer is a red color conversion layer;

    The display panel further includes a blue light emitting unit, and the blue light emitting unit includes a bottom reflective layer, a blue light emitting device, and a reflective encapsulation layer that are sequentially stacked.
15. The display panel according to claim 14, wherein,

    The display panel further includes a green light-emitting unit, which includes a bottom reflective layer, a light-emitting device, a middle reflective layer, a green color conversion layer, and a reflective encapsulation layer that are sequentially stacked.
16. The display panel according to claim 14, wherein,

    The display panel further includes a green light-emitting unit, which includes a bottom reflective layer, a green light-emitting device, and a reflective encapsulation layer that are sequentially stacked.
17. The display panel according to any one of claims 10 to 12, characterized in that,

    The display panel includes a plurality of the light emitting units;

    The color conversion layer of the plurality of light-emitting units is a color conversion layer with an integrated structure, and the color conversion layer with an integrated structure is also located between the light-emitting devices of any two light-emitting units;

    The reflective encapsulation layers of the plurality of light emitting units are integrated and located on the surface of the color conversion layer of the integrated structure.
18. The display panel according to any one of claims 10 to 12, characterized in that,

    The display panel includes a plurality of the light emitting units;

    The display panel also includes:

    a leveling layer, the leveling layer is located between any two light-emitting devices of the light-emitting unit;

    The color conversion layer of the plurality of light-emitting units is a color conversion layer of an integral structure, and the color conversion layer of an integral structure is also located on the side of the smoothing layer away from the circuit layer;

    The reflective encapsulation layers of the plurality of light emitting units are integrated and located on the surface of the color conversion layer of the integrated structure.
19. The display panel according to claim 12, characterized in that,

    The display panel includes a plurality of light-emitting units, and the middle reflection layers in each light-emitting unit are electrically connected to each other.
20. An electronic device, characterized by comprising the display panel according to any one of claims 1-19.

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