Light emitting device, method of manufacturing the same, and electronic device including the light emitting device

Abstract

The present disclosure relates to a light-emitting device, a method for manufacturing the same, and an electronic device including the light-emitting device. The light-emitting device includes a first substrate, a plurality of first electrodes on the first substrate, and a stack of functional layers on the plurality of first electrodes, the stack including at least a light-emitting layer including a plurality of units independent of each other, the plurality of units being disposed in correspondence with the respective first electrodes, wherein no isolation structure extending from the first substrate or the first electrode to a height of or above the plurality of units to separate the plurality of units is disposed between the plurality of units.

Description

Technical Field

[0001] This disclosure relates to light-emitting devices and methods for preparing the same, as well as electronic devices including light-emitting devices. Background Technology

[0002] Light-emitting devices such as light-emitting diodes (LEDs) are widely used in lighting and display applications. In display devices, a pixel boundary layer (PDL) is typically provided to define pixels. Usually, the pixel boundary layer is presented in the form of a bank to define pixels (or subpixels), thereby separating them. The pixel boundary layer (bank) is generally fabricated on a substrate containing active devices (such as thin-film transistors, TFTs), which is also called a TFT substrate.

[0003] However, in the prior art, using the same electrode materials, functional stacked materials and film layer thickness design, the performance of light-emitting devices prepared by printing method is far lower than that prepared by planar spin coating method.

[0004] This disclosure provides a novel light-emitting device with improved performance and light emission uniformity. Summary of the Invention

[0005] According to one aspect of this disclosure, a light-emitting device is provided, comprising: a first substrate; a plurality of first electrodes disposed on the first substrate; and a stack of functional layers disposed on the plurality of first electrodes, the stack comprising at least a light-emitting layer, the light-emitting layer comprising a plurality of independent units disposed corresponding to the respective first electrodes, wherein no isolation structure is provided between the plurality of units extending from the first substrate or the first electrodes to the height of the plurality of units to separate the plurality of units.

[0006] In one embodiment, the isolation structure is a pixel delimiting layer used to define pixels.

[0007] In one embodiment, the orthographic projection of each of the plurality of units on the first substrate covers the orthographic projection of the corresponding first electrode on the first substrate, wherein the plurality of units are arranged in a one-to-one correspondence with the plurality of first electrodes.

[0008] In one embodiment, the plurality of units are configured to be separated from each other. In another embodiment, the stack further includes an upper functional layer located above the light-emitting layer, at least a portion of which is located between the units of the plurality of units.

[0009] In one embodiment, between the units, at least a portion of the upper functional layer contacts a portion of the lower functional layer below the light-emitting layer that is not obscured by the light-emitting layer.

[0010] In one embodiment, the light-emitting device further includes a second electrode located on the stack, wherein each of the plurality of units of the light-emitting layer, the corresponding portion of the first electrode and the second electrode is included in the corresponding pixel.

[0011] In one embodiment, the stack further includes a lower functional layer beneath the light-emitting layer, wherein the portion of the lower functional layer that overlaps with the units of the light-emitting layer has the same surface properties as the portion of the lower functional layer that does not overlap with the units of the light-emitting layer.

[0012] In one embodiment, the plurality of units of the light-emitting layer are formed by drying printed ink droplets containing quantum dot material. The plurality of units are configured, in a top view, such that: for any unit, the lateral dimension of the unit is greater than or equal to the sum of the lateral dimension of the first electrode corresponding to the unit and twice the printing precision of the nozzle used for printing; and between two adjacent units, the center-to-center distance between the two first electrodes corresponding to the two adjacent units is greater than or equal to the sum of half the lateral dimension of each of the two adjacent units and twice the printing precision of the nozzle used for printing.

[0013] In one embodiment, the stack further includes one or more functional layers below or above the light-emitting layer, wherein the one or more functional layers include at least one of the following: a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, an electron blocking layer, and a buffer layer.

[0014] In one embodiment, the light-emitting device is a bottom-emitting type, a top-emitting type, or a double-sided-emitting type.

[0015] In one embodiment, each of the plurality of units of the light-emitting layer and a corresponding first electrode are included in a corresponding pixel, a transistor is formed in the first substrate, and the light-emitting device further includes: an opposing second substrate; and a spacer disposed between the first substrate and the second substrate, the spacer being disposed offset from the pixel.

[0016] According to another aspect of this disclosure, a method for fabricating a light-emitting device is also provided, comprising: providing a first substrate having a plurality of first electrodes thereon; and forming a stack of functional layers on the first substrate, the stack comprising at least a light-emitting layer, the light-emitting layer comprising a plurality of independent units, the plurality of units being disposed corresponding to a corresponding first electrode, wherein no isolation structure is provided between the plurality of units extending from the first substrate or the first electrode to the height of the plurality of units or above, thereby separating the plurality of units.

[0017] In one embodiment, forming a stack of functional layers on the first substrate includes: forming liquid printing units corresponding to the plurality of units of the light-emitting layer by means of an ink droplet printing method, wherein the ink droplets contain quantum dot material; drying the liquid printing units to form the plurality of units of the light-emitting layer; wherein the orthographic projection of each of the plurality of units on the first substrate covers the orthographic projection of the corresponding first electrode on the first substrate.

[0018] In one embodiment, the stack of functional layers formed on the first substrate further includes one or more of the following: forming a lower functional layer that at least covers the plurality of first electrodes, wherein the plurality of units of the light-emitting layer are located above the lower functional layer, and the portions of the lower functional layer that overlap with the units of the light-emitting layer have the same properties as the portions of the lower functional layer that do not overlap with the units of the light-emitting layer; and forming an upper functional layer that covers the plurality of units of the light-emitting layer.

[0019] In one embodiment, the orthographic projection of each of the plurality of units on the first substrate overlaps the orthographic projection of the corresponding first electrode on the first substrate.

[0020] In one embodiment, the plurality of units are configured such that they are separated from each other. In another embodiment, at least a portion of the upper functional layer is located between the units of the plurality of units.

[0021] In one embodiment, the plurality of units are configured such that, in a top view: for any unit, the lateral dimension of the unit is greater than or equal to the sum of the lateral dimension of the first electrode corresponding to the unit and twice the printing accuracy of the nozzle used for printing; and between two adjacent units, the center-to-center distance between the two first electrodes corresponding to the two adjacent units is greater than or equal to the sum of half the lateral dimension of each of the two adjacent units and twice the printing accuracy of the nozzle used for printing.

[0022] In one embodiment, the upper functional layer or the lower functional layer includes at least one of the following: a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, an electron blocking layer, and a buffer layer.

[0023] In one embodiment, the method further includes: forming a second electrode on the stack of the functional layers, wherein each of the plurality of units of the light-emitting layer, the corresponding portion of the first electrode and the second electrode is included in the corresponding pixel.

[0024] In one embodiment, the method further includes providing a spacer, wherein the spacer is disposed on the side of the second electrode away from the first electrode and is offset from the pixel.

[0025] According to another aspect of this disclosure, an electronic device is also provided, which includes a light-emitting device as described in any embodiment or implementation of this disclosure.

[0026] Other features and advantages of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0027] The accompanying drawings, which form part of this specification, illustrate embodiments of this disclosure and, together with the specification, serve to explain the principles of this disclosure.

[0028] This disclosure will become clearer with reference to the accompanying drawings and the following detailed description, wherein:

[0029] Figure 1 A schematic diagram of inkjet printing for fabricating light-emitting devices in the prior art is shown;

[0030] Figure 2 A schematic diagram of a light-emitting device according to an embodiment of the present disclosure is shown;

[0031] Figure 3 A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown;

[0032] Figures 4A-4C A schematic diagram showing the relationship between the cells of a printed light-emitting layer and a lower electrode according to an embodiment of the present disclosure is shown;

[0033] Figure 5A and 5B A schematic diagram showing the relationship between the cells of a printed light-emitting layer and a lower electrode according to another embodiment of the present disclosure;

[0034] Figures 6A-6E A schematic diagram of a method for fabricating a light-emitting device according to an embodiment of the present disclosure is shown;

[0035] Figure 7 A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown;

[0036] Figure 8 A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown;

[0037] Figure 9 A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown; and

[0038] Figure 10AA microscope image of a quantum dot (QD) layer printed in a light-emitting device prepared according to an example of this disclosure is shown. Figure 10B It shows the relationship with Figure 10A The area shown is corresponding to the step gauge scan results.

[0039] Note that in the following description, the same reference numerals are sometimes used across different figures to denote the same parts or parts with the same function, omitting repeated descriptions. In this specification, similar reference numerals and letters are used to denote similar items; therefore, once an item is defined in one figure, it need not be discussed further in subsequent figures.

[0040] For ease of understanding, the positions, dimensions, and extents of the structures shown in the accompanying drawings and other references may not represent actual positions, dimensions, and extents. Therefore, the disclosed invention is not limited to the positions, dimensions, and extents disclosed in the accompanying drawings and other references.

[0041] Specific implementation method

[0042] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present disclosure. Furthermore, techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification.

[0043] It should be understood that the following description of at least one exemplary embodiment is merely illustrative and not intended to limit the scope of this disclosure or its application or use. It should also be understood that any implementation described herein does not necessarily represent a preferred or advantageous implementation over others. This disclosure is not limited to any expressed or implied theory given in the foregoing description of the technical field, background, invention, or specific implementations.

[0044] Additionally, certain terms may be used in the following description for reference only, and are therefore not intended to be limiting. For example, unless the context clearly indicates otherwise, the words “first,” “second,” and other such numerical terms relating to structures or elements do not imply order or sequence.

[0045] It should also be understood that when the term “including / contains” is used herein, it indicates the presence of the indicated feature, whole, step, operation, unit and / or component, but does not preclude the presence or addition of one or more other features, wholes, steps, operations, units and / or components and / or combinations thereof.

[0046] In existing light-emitting devices (such as display devices), the height of the isolation structure (bank) used as the pixel defining layer is typically several micrometers (μm). When functional layers, such as the light-emitting layer, are prepared using ink printing, the ink droplets are affected by capillary effects at the isolation structure. After drying, they accumulate at the edges of the isolation structure, causing uneven film layers, such as... Figure 1 As shown.

[0047] Figure 1 A schematic diagram of a light-emitting device fabricated using inkjet printing in the prior art is shown. For example... Figure 1 As shown, a pixel defining layer for defining pixel areas is formed on substrate 1101, which includes multiple isolation structures 1103. Ink droplets 1107 containing material for forming functional layers are sprayed onto substrate 1101 through nozzle 1105, thereby printing functional layers, such as light-emitting layers, in the pixel areas defined by the pixel defining layer. However, as... Figure 1 As shown, the printed ink droplets are affected by capillary effect at the isolation structure. The droplets will wet the surface of the isolation structure, resulting in a film thickness at the edge that is greater than that at the center. This causes the material to accumulate at the edge of the isolation structure after drying, resulting in an uneven film layer.

[0048] The uniformity of the film layers in a light-emitting diode (LED) is difficult to achieve due to the influence of the isolation structure (capillary effect). Furthermore, LEDs can include multiple layers of thin films (such as hole injection layers, hole transport layers, light-emitting layers, electron transport layers, and electron injection layers), making it even more difficult to achieve uniform and flat film layers when using printing methods to fabricate multilayer thin films.

[0049] On the other hand, the upper electrode exhibits poor bonding stability at the isolation structure. The upper electrode typically covers the entire functional layer and the top of the isolation structure, and is usually quite thin, with the total thickness of the electrode film typically only a few hundred nanometers (nm). In contrast, the isolation structure is typically several micrometers high. Therefore, the significant height difference between the isolation structure and the total film thickness easily leads to breakage of the upper electrode.

[0050] Therefore, in the prior art, using the same electrode materials, functional stacked materials and film layer thickness design, the performance of light-emitting devices prepared by printing method is far lower than that of light-emitting devices prepared by planar spin coating method.

[0051] This disclosure addresses at least one or more of the above-mentioned problems by providing a novel light-emitting device with improved performance and light emission uniformity.

[0052] The embodiments according to this disclosure will now be described in detail with reference to the accompanying drawings.

[0053] Figure 2 A schematic diagram of a light-emitting device according to an embodiment of the present disclosure is shown. Figure 2As shown, the light-emitting device 200 includes a first substrate 101. A plurality of first electrodes 103 are formed on the first substrate 101. The light-emitting device 200 also includes a stack of functional layers (not indicated by reference numerals) located above the plurality of first electrodes. The stack includes at least a light-emitting layer, which includes a plurality of independent units 107. Figure 2 In the illustrated embodiment, the plurality of units 107 are shown to be separated from each other. The plurality of units 107 are arranged corresponding to a respective first electrode; for example, in some embodiments, the units 107 may be arranged in a one-to-one correspondence with the first electrode 103.

[0054] In the light-emitting device according to this embodiment, there is no isolation structure extending from the first substrate or the first electrode to the height of the unit 107 or above to separate the plurality of units 107. In other words, the light-emitting device of this embodiment does not have a pixel defining layer as in the prior art.

[0055] In this embodiment, the plurality of units 107 are configured such that the orthographic projection of each unit 107 on the first substrate 101 overlaps the orthographic projection of the corresponding first electrode 103 on the first substrate. This improves luminous efficiency. Furthermore, it reduces the influence of adjacent pixels (or sub-pixels) on the current pixel (or sub-pixel). This will be discussed later in conjunction with the appendix. Figures 4A-4C 5A and 5B will be described in more detail. In this document, the luminescent layer may also be indicated by reference numeral 107 when necessary.

[0056] exist Figure 2 The diagram also shows a lower functional layer 105 below the light-emitting layer (which includes unit 107) and an upper functional layer 109 above the light-emitting layer. Those skilled in the art will readily understand that one or more of the lower functional layer 105 or the upper functional layer 109 are optional. Furthermore, although in Figure 2 The lower middle functional layer 105 and the upper functional layer 109 are shown as single layers, but they can be multiple layers. Additionally, although in Figure 2 In the illustrated embodiment, one or more functional layers are shown as a single sheet, meaning that the functional layer can be used for multiple pixels or subpixels. However, in other embodiments, the functional layer may also include multiple units, and a single unit may be used for one or more pixels or subpixels.

[0057] Here, "functional layer" has its general meaning in the art. As an example, a functional layer may refer to a layer disposed between two electrodes of a light-emitting unit. A functional layer may include at least one of the following: a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, an electron blocking layer, a buffer layer, and / or any layer that implements other desired functions, etc. In some implementations, the electrodes or functional layer may be shared by two or more pixels.

[0058] exist Figure 2 In the illustrated implementation, the plurality of units 107 are shown as separate from each other, with at least a portion of the upper functional layer 109 located between the units of the plurality of units 107. In this embodiment, the plurality of units 107 are arranged in the same layer. In other words, the plurality of units 107 are arranged in the same layer, and their thicknesses are substantially the same within a certain range of process precision.

[0059] In some embodiments, between light-emitting layer units 107, at least a portion of the upper functional layer 109 contacts a portion of the lower functional layer 105 below the light-emitting layer that is not covered by the light-emitting layer.

[0060] In some embodiments, the units of the light-emitting layer are formed by drying printed ink droplets containing quantum dot material. This allows the formation of a quantum dot display device. In some embodiments, the quantum dots can be configured to be uniformly dispersed within the ink droplets. In some embodiments, a portion of the lower functional layer 105 (or one or more layers therein) beneath the light-emitting layer 107 can be treated to alter its surface properties compared to other portions, thereby influencing the spread of the ink droplets. For example, a portion of the surface of the lower functional layer (or one or more layers therein) can be treated with ultraviolet light to change its hydrophilicity or other properties. However, since functional layers are typically layers with requirements for photoelectric properties or other attributes and have complex compositions, such treatment may adversely affect photoelectric properties, chemical properties, or surface flatness, thus impacting device performance. Furthermore, in the patterning process using surface hydrophilicity treatment, the materials of each functional layer are required to have the same surface hydrophilicity, making the material selection for the functional layers more stringent while simultaneously considering the photoelectric performance of the light-emitting device. Therefore, in a more preferred embodiment, this process is not performed. Instead, the surface properties of the portions of the lower functional layer that overlap with the units of the light-emitting layer are made consistent with those of the portions of the lower functional layer that do not overlap with the units of the light-emitting layer. This reduces process complexity, improves fabrication efficiency, lowers costs, and minimizes the impact on device performance.

[0061] Figure 3 A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown. Compared to Figure 2 The illustrated light-emitting device 200 and light-emitting device 300 further include a second electrode 301 located on the stack of functional layers. Depending on the requirements, in some implementations, the second electrode 301 may be a monolithic electrode (or a blanket electrode) that can cover the functional layers of multiple pixels. However, this disclosure is not limited thereto. In some implementations, the second electrode 301 may be configured to allow light emitted by the light-emitting layer to be transmitted through it. Exemplarily, the thickness of the second electrode 301 may be several hundred nanometers, for example, 100 nm-200 nm.

[0062] Each unit in the plurality of units 107 of the light-emitting layer, and the corresponding portion of the first electrode 103 and the second electrode 301, can be included in the corresponding pixel. The corresponding first electrode 103, the corresponding portion in the stack of functional layers, and the corresponding portion of the second electrode 301 together constitute a light-emitting unit (or light-emitting device). Generally, a pixel may include one or more light-emitting units. A pixel may also include multiple sub-pixels, each sub-pixel having a light-emitting unit. For example, a pixel may include three light-emitting units (red, green, and blue, which may also be referred to as sub-pixels) for red, green, and blue (RGB).

[0063] In some embodiments, the light-emitting device 300 may further include a cover layer 303 disposed above the second electrode 301. The cover layer is configured to allow light transmitted from the second electrode to pass through, and the cover layer can improve the light extraction efficiency of the device.

[0064] In some embodiments, the capping layer can be composed of a high refractive index (n) material, typically n greater than 1.65, preferably greater than 1.8. The thickness of the capping layer can range from tens of nanometers to thousands of nanometers. In some implementations, the capping layer can be formed from organic small molecule materials via thermal evaporation processes, such as NPB, Alq, CBP, etc.; the thickness of the capping layer can be, for example, 20 nm-400 nm. In some implementations, the capping layer can be made of inorganic materials, fabricated via chemical vapor deposition (CVD) or physical vapor deposition (PVD) processes, such as Al2O3, Si. x N y Si x N y O zThe thickness can be, for example, 20nm-400nm. In some implementations, the coating layer can be made of an organic-inorganic hybrid material, fabricated using a wet film-forming process, such as slot coating, inkjet printing, ultrasonic spraying, screen printing, etc.; the thickness can be, for example, 300nm-3000nm. The organic material can be a polymer resin, such as acrylic resin, epoxy resin, etc., or can be selected from polymethyl methacrylate, polycyclic olefins, etc. The inorganic material can be selected from metal compound particles, such as alumina, titanium dioxide, zirconium oxide, etc. Preferably, the particle size of the inorganic particles generally does not exceed 1000nm.

[0065] In different implementations, the light-emitting device according to this disclosure can be a bottom-emitting type light-emitting device that emits light through a first electrode and a first substrate, a top-emitting type light-emitting device that emits light through a second electrode, or a double-sided light-emitting type light-emitting device that emits light through both.

[0066] Figures 4A-4C A schematic top view illustrating the relationship between the cells of a printed light-emitting layer and a lower electrode (also referred to as the bottom electrode) according to an embodiment of the present disclosure is shown. In this example, the lower electrode 103 is shown as circular. The cells 107 of the light-emitting layer are also shown as circular. In the top view, the cells 107 of the light-emitting layer cover the lower electrode (i.e., the first electrode) 103. That is, the orthographic projection of the cells 107 of the light-emitting layer on the first substrate 101 covers the orthographic projection of the corresponding first electrode 103 on the first substrate. Here, those skilled in the art will readily understand that the actual shape of the dried ink droplet is generally close to a circle, but it is difficult to achieve a perfect circle; a circle is used here as an example for theoretical calculation. In practical applications, those skilled in the art can easily perform calculations according to actual needs based on the principles taught in this application.

[0067] In some embodiments, the light-emitting layer is fabricated by droplet printing, in which case the cells formed by droplet printing preferably cover the lower electrode. For example... Figure 4A As shown, assume the radius of the circular unit 107 formed after the ink droplet dries (which can be considered as half of the lateral dimension (diameter)) is R, the radius of the lower electrode 103 is r, and the printing accuracy (e.g., the deviation of the ink droplet landing point) is a. Assume that, ideally, the center of the circular unit 107 formed after the printed ink droplet dries coincides with (aligns with) the circular lower electrode 103. It should be noted that the nozzle alignment of the printing device with the lower electrode can be achieved through a built-in function of the device (e.g., automatic alignment of the CCD camera), and the landing point accuracy is determined by the printing device.

[0068] Considering the printing accuracy (e.g., the deviation of ink droplet landing point) a, the radius R of the circular unit 107 formed after the ink droplet dries should be greater than or equal to the sum of the radius r of the lower electrode 103 and the printing accuracy (e.g., printing landing point error) a, that is, R ≥ r + a. Thus, it can be ensured that under the condition of printing accuracy a, the unit 107 of the printed light-emitting layer can also completely cover the lower electrode 103.

[0069] In the absence of significant leakage current, generally only the portion of the printed light-emitting layer that overlaps with the lower electrode will emit light.

[0070] Figure 4B The diagram shows two adjacent cells 107 of the light-emitting layer and two corresponding adjacent lower electrodes 103. (See diagram for reference.) Figure 4B As shown, the radii of the two units 107 are R1 and R2, and the printing accuracies are a1 and a2, respectively. The radii of the two lower electrodes 103 are r1 and r2, respectively. They satisfy the conditions mentioned above, namely, R1≥r1+a1 and R2≥r2+a2.

[0071] The center distance d between two adjacent lower electrodes 103 is configured to be greater than or equal to the sum of the radii R1 and R2 of the two units 107 and the printing precision a1 and a2. That is, d ≥ R1 + R2 + a1 + a2. When R1 = R2 = R, r1 = r2 = r and a1 = a2 = a, the spacing d ≥ 2R + 2a ≥ 2r + 4a.

[0072] It should be understood that the size of the film layer after ink droplet drying and the size and spacing of the lower electrode can be set according to different display resolutions, different pixel designs (e.g., different geometries and sizes), whether partial overlap is allowed, and device precision.

[0073] As an example, consider the following scenario. Initial conditions: 150ppi resolution, forming four equally sized circular lower electrodes (1 red, 1 green, 2 blue), and a printing device with a resolution of 10 micrometers. Figure 4C As shown, the corresponding square pixel side length is 169 micrometers (25400 micrometers / 150), and the lower electrode spacing is half the side length, 169 / 2 = 84.5 micrometers. Since 2R+2a≤d, i.e., R≤(d-2a) / 2=(84.5-2*10) / 2=32.25 micrometers, the maximum radius of the unit formed after the ink droplet dries is 32.25 micrometers. Simultaneously, r≤Ra=22.25 micrometers, meaning the maximum radius of the lower electrode is 22.25 micrometers, corresponding to a maximum aperture ratio of 21.7%.

[0074] Therefore, the substrate resolution and pixel design determine the lower electrode spacing, the lower electrode spacing and the printing equipment precision determine the upper limit of the diameter of the unit formed by the ink droplet, and the diameter of the unit formed by the ink droplet (experimental value) determines the upper limit of the lower electrode radius.

[0075] The circular lower electrode described here is merely exemplary; its aperture ratio is relatively low as previously shown, but it conforms to the natural drying shape of the printed ink droplets and facilitates discussion of the lower electrode spacing. The same principle can be applied in actual products to configure units and electrodes with the desired geometry. For example, a rectangular electrode is used in the embodiment described later.

[0076] Furthermore, the radius R of the dried unit formed by ink droplet printing may be affected by the following factors: ink formulation, size and shape of the lower electrode. Adjusting the ink formulation can change its spreading radius. Generally, the higher the surface tension of the ink, the smaller the spreading radius; the lower the surface tension, the larger the spreading radius. The surface tension of the ink is mainly adjusted by the proportions of various solvents in the formulation (different solvents have different surface tensions). Therefore, it is possible to adjust the ink droplet formulation to ensure that the printed droplets just cover the lower electrode area without flowing into the lower electrode area of ​​adjacent sub-pixels, according to actual needs. Depending on the formulation, the ratio of the diameter of the unit formed by ink droplets containing quantum dot materials before and after drying can be approximately 1.5:1 to approximately 1.1:1.

[0077] Adjusting the solid content of the ink can change the film thickness. Since there is no pixel isolation structure (no pixel defining components, such as isolation structures (banks)) in the embodiments of this disclosure, the film thickness cannot be changed by increasing or decreasing the number of printed ink droplets; however, the film thickness can be satisfied by precisely controlling the solid content of the ink formulation itself, while also meeting the requirements for the spreading radius.

[0078] Additionally, the spreading radius can be adjusted by regulating the ink's evaporation rate. Controlling the overall evaporation rate ensures that the solute within the ink droplet spreads to the required radius just as the highly volatile solvent is about to completely evaporate. If it hasn't reached the required radius, the solute may become too viscous in the remaining solvent to move, potentially resulting in incomplete coverage of the lower electrode area. If the highly volatile solvent spreads to the required radius but hasn't completely evaporated, it may exceed the spreading radius, interfering with adjacent sub-pixels and potentially causing color mixing. However, it should be understood that these are not limiting factors and can be utilized in certain situations.

[0079] Figure 5A and 5B A schematic diagram illustrating the relationship between the cells of a printed light-emitting layer and a lower electrode according to another embodiment of this disclosure is shown. Figure 5A and 5BIn the illustrated embodiment, an elongated pixel is used as an example for explanation.

[0080] like Figure 5A As shown, the unit 107 formed by printing ink droplets (multiple times) is elongated and L wide; the lower electrode is also elongated and l wide. Those skilled in the art will readily understand that units of the light-emitting layer in a basic elongated shape or any other shape can be formed by printing multiple ink droplets and drying them.

[0081] Assuming that, ideally, the center line of the cell 107 formed by the ink droplet printing is aligned with the center line of the lower electrode, then, similarly, to ensure coverage, the cell 107 is configured such that its half-width (half of the lateral dimension, L / 2) is greater than or equal to the sum of the half-width (l / 2) of the corresponding lower electrode 103 and the printing precision (a), that is, L / 2 ≥ l / 2 + a.

[0082] Figure 5B The diagram illustrates the arrangement of adjacent cells 1071 and 1072 and their corresponding adjacent lower electrodes 1031 and 1032. Each cell 1071 and 1072 is elongated and parallel in its extending direction. The corresponding lower electrodes 1031 and 1032 are also elongated and parallel in their extending directions. The cells 1071 and 1072 and their corresponding lower electrodes 1031 and 1032 satisfy the aforementioned configuration, i.e., the half-width (L / 2) of the cell is greater than or equal to the sum of the half-width (l / 2) of the corresponding lower electrode and the printing precision (a).

[0083] Similarly, the center distance d between two adjacent lower electrodes 1031 and 1032 is configured to be greater than or equal to the sum of the half-widths L1 / 2 and L2 / 2 of the two units 1071 and 1072 and the printing precisions a1 and a2. That is, d ≥ L1 / 2 + L2 / 2 + a1 + a2. When L1 = L2 = L, l1 = l2 = l and a1 = a2 = a, the spacing d ≥ L + 2a ≥ l + 4a.

[0084] As an example, let's set the initial conditions: 100ppi resolution, red, green, and blue pixels of equal width and spacing, and a printing device accuracy of 10 micrometers. The corresponding square pixel side length is 254 micrometers (25400 micrometers / 100), and the lower electrode spacing d = 254 / 3 = 84.7 micrometers. The width of the unit formed by the ink L ≤ d - 2a = 64.7 micrometers, and the lower electrode width l ≤ L - 2a = 64.7 - 20 = 44.7 micrometers.

[0085] The following describes a method for preparing a light-emitting device according to an embodiment of the present disclosure. Figures 6A-6E A schematic diagram of a method for fabricating a light-emitting device according to an embodiment of the present disclosure is shown.

[0086] like Figure 6A As shown, a first substrate 101 is provided, having a plurality of first electrodes 103 thereon. The first substrate 101 may be a TFT substrate (which may also be referred to as a pixel substrate). Optionally, the first substrate may be cleaned. For example, the substrate may be solvent-cleaned with a cleaning agent, washed with water, then spin-dried, and then subjected to surface plasma treatment for later use.

[0087] Next, as Figure 6B and 6C As shown, a stack of functional layers is formed on a first substrate 101, the stack including at least a light-emitting layer, the light-emitting layer including a plurality of units 107. The plurality of units 107 are disposed corresponding to a corresponding first electrode. There is no isolation structure between the plurality of units 107 extending from the first substrate or the first electrode to the height of the plurality of units or above, thereby separating the plurality of units. This isolation structure is also referred to in the prior art as a pixel defining layer (PDL).

[0088] In some implementations, forming a stack of functional layers on the first substrate 101 may include the following steps: forming liquid printing units corresponding to the plurality of units of the light-emitting layer by means of an ink droplet printing method, wherein the ink droplets contain quantum dot material; and drying the liquid printing units to form the plurality of units of the light-emitting layer. In some implementations, the orthographic projection of each of the plurality of units on the first substrate overlaps the orthographic projection of the corresponding first electrode on the first substrate.

[0089] In some implementations, the fabrication method of the light-emitting device does not include hydrophilic or hydrophobic treatment of any electrode or functional layer.

[0090] In some implementations, optionally, such as Figure 6B As shown, a lower functional layer 105 is formed, which at least covers the plurality of first electrodes 103; then, the plurality of units 107 of the light-emitting layer are formed on the lower functional layer in the same manner as described above.

[0091] In some embodiments, the lower functional layer 105 may include a hole injection layer and a hole transport layer (not shown in the figures). In some implementations, the hole injection layer can be prepared as follows: a hole injection material is formulated into a suitable ink formulation for coating, appropriate coating parameters are selected, coating is performed, and after coating, the substrate is placed on a hot plate for drying. Subsequently, the hole transport layer can be prepared as follows: a hole transport layer material is formulated into a printable formulation, printed, and printed on top of the aforementioned hole injection layer material; then the substrate is transferred to a vacuum hot plate for drying. It should be understood that the methods for preparing the lower functional layer described herein are exemplary and not limiting; those skilled in the art will understand that various methods can be used to prepare the functional layer. In some implementations, the thickness of the hole injection layer (HIL) can range from tens to hundreds of nanometers, for example, 20 nm–300 nm, preferably 30 nm–150 nm; the thickness of the hole transport layer (HTL) can range from tens to hundreds of nanometers, for example, 10 nm–200 nm, preferably 15 nm–100 nm.

[0092] After preparing the optional lower functional layer, a light-emitting layer can be formed on the lower functional layer. In some implementations, the quantum dot (QD) light-emitting layer can be prepared as follows: the QD stock solution is centrifuged and precipitated, then redispersed in a printing solvent formulation to prepare a printable ink, which is then loaded into a printing device; according to the set printing parameters, the QD ink is precisely printed on the independent electrode regions of the pixel substrate, completely covering the corresponding lower electrode regions; the substrate is then transferred to a vacuum hot plate for drying. In some implementations, the thickness of the QD light-emitting layer can be in the range of tens to hundreds of nanometers, for example, 10nm–100nm, preferably 15nm–60nm.

[0093] After that, as Figure 6C As shown, alternatively, a similar or any suitable method can be used to form the upper functional layer 109, which covers the plurality of units 107 of the light-emitting layer. As an example, the above-mentioned functional layer may include an electron transport layer and / or an electron injection layer, each with a thickness ranging from tens to hundreds of nanometers, for example, 10 nm–400 nm, preferably 20 nm–100 nm.

[0094] After that, as Figure 6D As shown, a second electrode 301 is formed on the stack of the functional layers. In some implementations, the second electrode 301 can be configured to be formed integrally, covering the display area of ​​one or more pixels (or sub-pixels). Optionally, as... Figure 6E As shown, a light-transmitting cover layer 303 is formed on the second electrode.

[0095] Figure 7A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown. Figure 7 As shown, the light-emitting device 700 also includes a spacer 701. The spacer 701 is disposed on the side of the second electrode 301 away from the first electrode. The spacer 701 can be used to reduce the impact of pressure or stress on the pixel during packaging, thereby protecting the pixel or light-emitting unit.

[0096] Here, as previously stated, each unit in the plurality of units 107 of the light-emitting layer, and the corresponding portions of the first electrode 103 and the second electrode 301, can be included in the corresponding pixel. It should also be noted that, unless otherwise stated, the term "pixel" in this application can include sub-pixels.

[0097] When the light-emitting device 700 also includes an optional cover layer 303, the spacer 701 is disposed on the side of the second electrode 301 away from the first electrode, and is opposite to the second electrode 301 through the cover layer 303. The spacer 701 is disposed offset from the pixel, thereby avoiding blocking the light emitted by the light-emitting unit and preventing pressure or stress from being transmitted to the light-emitting unit of the pixel.

[0098] Despite Figure 7 In the illustrated embodiment, spacer 701 is shown formed at the cover layer and has an elliptical cross-sectional shape; however, this is merely exemplary and is not limited thereto. Spacer 701 may also be disposed on an opposing substrate (such as...). Figure 8 As shown in 801, it can also take any desired shape.

[0099] Here, as an example, spacer 701 can be prepared by printing, for example, by printing ink droplets multiple times at desired locations and drying them to form spacer 701. Alternatively, spacer 701 can also be obtained by depositing spacer material (e.g., organic or inorganic insulating material) and patterning it (e.g., by etching using a mask).

[0100] As an example, the thickness of the spacer can be 0.5 micrometers to 5 micrometers; the cross-sectional shape can be a positive trapezoid (formed by photolithography using positive photoresist) or an inverted trapezoid (formed by photolithography using negative photoresist); the material can be one or more of the following: polymethyl methacrylate (PMMA), polystyrene (PS), polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyurethane (PU), and polyvinyl chloride (PVC).

[0101] The density and arrangement of spacers are related to pixel design and arrangement, and can be lower than the pixel resolution (PPI).

[0102] Figure 8A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown. Figure 8 As shown, compared to Figure 7 The light-emitting device 800 shown also includes a second substrate 801 facing each other. The second substrate 801 and the first substrate 101 can be facing each other and encapsulated. The light-emitting unit (the stack of functional layers) is disposed between the first substrate and the second substrate. A filler material 803 can be filled between the second substrate 801 and the first substrate 101.

[0103] Figure 9 A schematic diagram of a light-emitting device according to another embodiment of the present disclosure is shown. Figure 9 As shown, the light-emitting device 900 may include a first substrate 901 and an opposing second substrate 905. A plurality of pixels 903 may be formed on the first substrate 901. Each pixel 903, or at least its light-emitting unit, may be a pixel or light-emitting unit prepared according to the foregoing embodiments of this disclosure. A plurality of spacers 907 are formed on the second substrate 905. The first substrate 901 and the second substrate 905 are encapsulated by an encapsulant 911, and a filler 909 may be filled between the first substrate 901 and the second substrate 905. Although the spacers 907 are shown here as having a trapezoidal cross-section, this is merely exemplary, and this disclosure is not limited thereto; any suitable shape may be used.

[0104] The following describes an example of a method for preparing a display device according to the present disclosure.

[0105] First, a first substrate is provided. The first substrate may be a pixel substrate for forming pixels, and sometimes it may also be referred to as a TFT substrate. Here, the first substrate may be a substrate without an isolation structure according to any of the foregoing embodiments or implementations.

[0106] Optionally, the first substrate can be cleaned, for example, by solvent cleaning with a cleaning agent, rinsing with water, and then spin-drying. Next, the first substrate can undergo surface plasma treatment for later use.

[0107] Then, a hole injection layer is formed on the first substrate. For example, the hole injection material can be formulated into a suitable coating solution, appropriate coating parameters can be selected, and coating can be performed. After coating, the substrate is placed on a hot plate to allow the coating solution to dry. Thus, the hole injection layer is formed.

[0108] Next, a hole transport layer is formed. For example, the hole transport layer material can be formulated into a printable ink formula, and a first substrate clip with the hole injection layer formed on it is positioned. The material is then printed onto the hole injection layer using a printing device (e.g., a nanomaterial printing device DMP2831). The first substrate can then be dried using a vacuum hot plate. Thus, the hole transport layer is formed.

[0109] Next, a quantum dot (QD) layer is formed. For example, the QD stock solution can be centrifuged and precipitated, then redispersed in a printing solvent formulation to create a printable ink, which is then loaded into a printing device. According to the set printing parameters, the ink containing QD material is precisely printed onto the independent electrode regions of the pixel substrate, completely covering the electrode regions. After printing, the substrate can be transferred to a vacuum hot plate for vacuum drying. This process forms the quantum dot layer.

[0110] Figure 10A A microscope image of the QD layer printed on the first substrate (here, the pixel substrate) in the light-emitting device prepared according to this example is shown, while Figure 10B for Figure 10A The area shown corresponds to the protractor scan results. For example... Figure 10B As shown, the formed QD film layer is basically uniform from the edge to the middle.

[0111] According to one aspect of this disclosure, an electronic device is also provided, which may include a light-emitting device as described in any embodiment or implementation of this disclosure.

[0112] Those skilled in the art will recognize that the boundaries between operations (or steps) described in the above embodiments are merely illustrative. Multiple operations may be combined into a single operation, a single operation may be distributed among additional operations, and operations may be performed with at least partial overlap in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be changed in various other embodiments. However, other modifications, variations, and substitutions are equally possible. Therefore, this specification and the accompanying drawings should be considered illustrative rather than restrictive.

[0113] While specific embodiments of this disclosure have been described in detail by way of example, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. The various embodiments disclosed herein can be combined in any way without departing from the spirit and scope of this disclosure. Those skilled in the art should also understand that various modifications can be made to the embodiments without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A light-emitting device, characterized in that, include: First substrate; Multiple first electrodes are located on the first substrate; as well as A stack of functional layers is located above the plurality of first electrodes, the stack comprising at least: A lower functional layer above the first substrate and the plurality of first electrodes; A light-emitting layer above the lower functional layer, the light-emitting layer comprising a plurality of mutually separated units, the plurality of units being disposed corresponding to a respective first electrode, wherein the plurality of units of the light-emitting layer are formed by drying printed ink droplets; and An upper functional layer is located above the lower functional layer and the light-emitting layer, the upper functional layer covering the plurality of cells of the light-emitting layer, and at least a portion of the upper functional layer is located between the cells of the plurality of cells. Wherein, no isolation structure is provided between the plurality of units, extending from the first substrate or the first electrode to the height of the plurality of units or above, thereby separating the plurality of units. The surface properties of the portions of the lower functional layer that overlap with the units of the light-emitting layer are the same as those of the portions of the lower functional layer that do not overlap with the units of the light-emitting layer. Wherein, between the units, at least a portion of the upper functional layer contacts the portion of the lower functional layer below the light-emitting layer that is not shielded by the light-emitting layer, and Wherein, for any given unit, the lateral dimension of the unit is greater than or equal to the sum of the lateral dimension of the first electrode corresponding to the unit and twice the printing accuracy of the nozzle used for printing.

2. The light-emitting device as described in claim 1, characterized in that, The isolation structure mentioned above is a pixel delimiting layer used to define pixels.

3. The light-emitting device as described in claim 1, characterized in that, The orthographic projection of each of the plurality of units on the first substrate overlaps the orthographic projection of the corresponding first electrode on the first substrate. The plurality of units are arranged in a one-to-one correspondence with the plurality of first electrodes.

4. The light-emitting device as described in claim 1, characterized in that, The at least portion of the upper functional layer and the unit adjacent to the at least portion of the plurality of units are in contact.

5. The light-emitting device as claimed in claim 1, characterized in that, The ink droplets contained quantum dot materials. The plurality of units are configured, in the top view: Between two adjacent units, the center-to-center distance between the two first electrodes corresponding to the two adjacent units is greater than or equal to the sum of half the lateral dimension of each of the two adjacent units and twice the printing accuracy of the nozzle used for printing.

6. The light-emitting device as claimed in claim 1, characterized in that, The functional layers below or above the light-emitting layer include at least one of the following: hole injection layer, hole transport layer, electron injection layer, electron transport layer, electron blocking layer, and buffer layer.

7. The light-emitting device as claimed in claim 1, characterized in that: The light-emitting device is a bottom-emitting type, a top-emitting type, or a double-sided emitting type.

8. The light-emitting device as claimed in claim 1, characterized in that, Each of the plurality of units in the light-emitting layer and its corresponding first electrode are included in the corresponding pixel. Transistors are formed in the first substrate. The light-emitting device further includes: Opposite second substrate; and A spacer is disposed between the first substrate and the second substrate, and the spacer is disposed offset from the pixel.

9. A method for preparing a light-emitting device, characterized in that, include: A first substrate having a plurality of first electrodes thereon is provided; as well as A stack of functional layers is formed on the first substrate. The stack includes at least a light-emitting layer, which comprises a plurality of units separated from each other. The plurality of units are disposed corresponding to a respective first electrode. The stack that forms the functional layers includes: A lower functional layer is formed on the first substrate and the plurality of first electrodes, the lower functional layer at least covering the plurality of first electrodes; A light-emitting layer is formed on top of the lower functional layer. The light-emitting layer includes a plurality of separately separated units, each unit corresponding to a first electrode. The surface properties of the portions of the lower functional layer that overlap with the units of the light-emitting layer are identical to those of the portions of the lower functional layer that do not overlap with the units of the light-emitting layer. An upper functional layer is located above the lower functional layer and the light-emitting layer, covering the plurality of cells of the light-emitting layer, and at least a portion of the upper functional layer is located between the cells of the plurality of cells, wherein between the cells, the at least portion of the upper functional layer contacts the portion of the lower functional layer below the light-emitting layer that is not shielded by the light-emitting layer. Wherein, no isolation structure extending from the first substrate or the first electrode to the height of the plurality of units is provided between the plurality of units to separate them. The formation of the light-emitting layer above the lower functional layer includes: forming liquid printing units corresponding to the plurality of units of the light-emitting layer by means of an ink droplet printing method; and drying the liquid printing units to form the plurality of units of the light-emitting layer. Wherein, for any given unit, the lateral dimension of the unit is greater than or equal to the sum of the lateral dimension of the first electrode corresponding to the unit and twice the printing accuracy of the nozzle used for printing.

10. The method as described in claim 9, characterized in that, The ink droplets contained quantum dot materials; The orthographic projection of each of the plurality of units on the first substrate covers the orthographic projection of the corresponding first electrode on the first substrate.

11. The method as described in claim 9, characterized in that, The orthographic projection of each of the plurality of units on the first substrate covers the orthographic projection of the corresponding first electrode on the first substrate.

12. The method as described in claim 9, characterized in that, The plurality of units are configured, in the top view: Between two adjacent units, the center-to-center distance between the two first electrodes corresponding to the two adjacent units is greater than or equal to the sum of half the lateral dimension of each of the two adjacent units and twice the printing accuracy of the nozzle used for printing.

13. The method as described in claim 9, characterized in that, The upper functional layer or the lower functional layer includes at least one of the following: a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, an electron blocking layer, and a buffer layer.

14. The method as described in claim 9, characterized in that, Also includes: A second electrode is formed on the stack of the functional layers. Each of the plurality of units of the light-emitting layer, the corresponding portion of the corresponding first electrode and the corresponding portion of the second electrode are included in the corresponding pixel.

15. The method as described in claim 14, characterized in that, Also includes: A spacer is provided, wherein the spacer is disposed on the side of the second electrode away from the first electrode and is offset from the pixel.

16. An electronic device, characterized in that, Includes the light-emitting device as described in any one of claims 1-8.

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