Light emitting devices including a quantum dot color conversion material and method of making thereof

Abstract

The present invention provides a light-emitting device comprising a first optical cavity bounded by a cavity wall; a first light-emitting diode located within the first optical cavity and configured to emit blue or ultraviolet radiation first incident photons; a first color conversion material located on the first light-emitting diode and configured to absorb the first incident photons emitted by the light-emitting diode and generate first converted photons having a peak wavelength longer than that of the first incident photons; and a first color selector located on the first color conversion material and configured to absorb or reflect the first incident photons and transmit the first converted photons.

Description

Technical Field

[0001] This invention relates to a light-emitting device, and specifically to a light-emitting diode formed in an optical cavity using a color-conversion material, and a method for manufacturing the same. Prior Technology

[0002] Light-emitting devices are used in electronic displays (such as the backlight of LCD displays in laptops and televisions). Light-emitting devices include light-emitting diodes (LEDs) and various other types of electronic devices configured to emit light.

[0003] For light-emitting devices (such as LEDs), the emission wavelength is determined by the bandgap of the active region of the LED along with the size-dependent quantum confinement effect. Typically, the active region comprises one or more host semiconductor layers or quantum wells (QWs). For III-nitride-based LED devices (such as GaN-based devices), the active region material (e.g., the host semiconductor layer or QW well layer) can be ternary, having a composition such as In xGa 1-xN, where 0 < x < 1.

[0004] The band gap of these III-nitride materials depends on the amount of In incorporated into the active region. Higher indium incorporation results in a smaller band gap and therefore a longer emission wavelength. As used herein, the term "wavelength" refers to the peak emission wavelength of an LED. It should be understood that the typical emission spectrum of a semiconductor LED is a narrow band centered around the peak wavelength. Summary of the Invention

[0005] One embodiment of the light-emitting device includes a first optical cavity bounded by at least one first cavity wall; a first light-emitting diode located within the first optical cavity and configured to emit blue or ultraviolet radiation first incident photons; a first color conversion material located on the first light-emitting diode and configured to absorb the first incident photons emitted by the first light-emitting diode and generate first converted photons having a peak wavelength longer than that of the first incident photons; and a first color selector located on the first color conversion material and configured to absorb or reflect the first incident photons and transmit the first converted photons.

[0006] An embodiment of a method for forming an array of light-emitting devices includes forming a first via in a matrix material, depositing a first plurality of quantum dots in the first via to form a first portion of a color conversion layer corresponding to a first color; forming a second via in the matrix material, depositing a second plurality of quantum dots in the second via to form a second portion of a color conversion layer corresponding to a second color; forming a third via in the matrix material, and depositing a third plurality of quantum dots in the third via to form a third portion of a color conversion layer corresponding to a third color. The first plurality of quantum dots are located on a first light-emitting diode, the second plurality of quantum dots are located on a second light-emitting diode, and the third plurality of quantum dots are located on a third light-emitting diode. Simple Explanation of the Diagram

[0007] Figure 1A is a vertical cross-sectional view that can be used to form an intermediate structure for an array of light-emitting devices according to various embodiments.

[0008] Figure 1B is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0009] Figure 1C is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0010] Figure 1D is a vertical cross-sectional view of an array of light-emitting devices according to various embodiments.

[0011] Figure 1E is a vertical cross-sectional view of another light-emitting device array according to various embodiments.

[0012] Figure 2A is a top view of a first patterned matrix having a plurality of through holes formed therein, according to various embodiments.

[0013] Figure 2B is a top view of a second patterned matrix having a plurality of through holes formed therein, according to various embodiments.

[0014] Figure 3A is a vertical cross-sectional view that can be used to form an intermediate structure for an array of light-emitting devices according to various embodiments.

[0015] Figure 3B is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0016] Figure 3C is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0017] Figure 3D is a vertical cross-sectional view that can be used to form another intermediate structure for forming an array of light-emitting devices according to various embodiments.

[0018] Figure 3E is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0019] Figure 3F is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0020] Figure 3G is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0021] Figure 3H is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0022] Figure 3I is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0023] Figure 3J is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0024] Figure 3K is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0025] Figure 3L is a vertical cross-sectional view that can be used to form another intermediate structure for forming an array of light-emitting devices according to various embodiments.

[0026] Figure 4A is a vertical cross-sectional view that can be used to form an intermediate structure for an array of light-emitting devices according to various embodiments.

[0027] Figure 4B is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0028] Figure 4C is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0029] Figure 4D is a vertical cross-sectional view that can be used to form another intermediate structure for forming an array of light-emitting devices according to various embodiments.

[0030] Figure 4E is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0031] Figure 4F is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0032] Figure 4G is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0033] Figure 4H is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0034] Figure 4I is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0035] Figure 4J is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0036] Figure 4K is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0037] Figure 4L is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0038] Figure 4M is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0039] Figure 4N is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0040] Figure 4O is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0041] Figure 4P is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0042] Figure 5A is a vertical cross-sectional view that can be used to form an intermediate structure for an array of light-emitting devices according to various embodiments.

[0043] Figure 5B is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0044] Figure 5C is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0045] Figure 5D is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0046] Figure 5E is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0047] Figure 5F is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments.

[0048] Figure 5G is a vertical cross-sectional view of another intermediate structure that can be used to form an array of light-emitting devices according to various embodiments. Implementation

[0049] Display devices (such as direct-view displays) can be formed from an ordered array of pixels. Each pixel may contain a group of subpixels that emit light at their respective peak wavelengths. For example, a pixel may contain red, green, and blue subpixels. Each subpixel may contain one or more light-emitting diodes that emit light at a specific wavelength. Conventional arrangements would have red, green, and blue (RGB) subpixels within each pixel. Each pixel can be driven by backplane circuitry so that any combination of colors within the color gamut can be displayed on the display for each pixel. The display panel can be formed by soldering or otherwise electrically connecting LED subpixels to bonding pads located on a backplane. These bonding pads can be electrically driven by backplane circuitry and other driving electronics.

[0050] Various embodiments provide light-emitting devices configured to use photon-pumped quantum dots in a vertical-cavity structure to create highly efficient red, green, blue, and / or other color pixelated light from shorter wavelength excitation sources. Embodiments with lengths and widths less than 100 micrometers (such as 5 to 20 micrometers) include micrometer-scale light-emitting diodes (micro-LEDs) that can be used in display devices. This emerging technology provides the final black level by using individual LEDs at each pixel location in the display device. Additionally, each pixel can be configured to produce monochromatic light. A backplane to which individual LEDs can be attached may include a substrate (e.g., plastic, glass, semiconductor, etc.) having a thin-film transistor (TFT) structure, silicon CMOS, or other driving circuitry configured to independently apply voltage or current to each LED. For example, the backplane may include TFTs on a glass or plastic substrate, or a main silicon substrate or silicon-on-insulator (SOI) substrate with a main silicon transistor (e.g., a CMOS-configured transistor). While microLEDs are described in the following examples, it should be noted that other types of LEDs (e.g., nanowires or other nanostructured LEDs) or large LEDs with dimensions greater than 100 micrometers (e.g., width and length) may be used instead of microLEDs or other types of LEDs.

[0051] In some embodiments, the size of each microLED may be smaller than the pixel pitch in a particular display device (such as a direct-view display or another display device). For example, a 300 ppi display may have pixels with a pitch of about 85 micrometers, and a typical microLED for this display may have a width of about 20 micrometers. MicroLEDs containing indium-doped GaN material (i.e., LEDs whose emission color depends on the indium doping of GaN) may suffer from deterioration in efficiency and uniformity as the LED size decreases (e.g., less than 10 micrometers) due to the difficulties associated with indium doping of the GaN crystal structure. Therefore, III-nitride microLEDs (e.g., red LEDs) that emit longer peak wavelengths using higher indium content in their active regions may have insufficient efficiency and uniformity due to reduced indium doping.

[0052] Some embodiments of the present invention include photonic emitters coupled to photonic pump color conversion materials, based on LEDs having undoped GaN active regions (e.g., microLEDs with GaN luminescent active layers) or LEDs having low-indium-doped InGaN active regions (e.g., microLEDs with low-indium-content InGaN luminescent active layers). These LEDs may be ultraviolet (UV) emitting or blue emitting microLEDs having peak emission wavelengths in the UV or blue light spectral regions (e.g., 370 to 460 nm, such as 390 to 420 nm, such as 400 to 410 nm). As used herein, the blue light spectral region includes blue and violet as perceived by a human observer.

[0053] In one embodiment, the color-converting material may include quantum dots. The quantum dots can be configured to absorb photons generated by a GaN generator and produce light of various colors, depending on the properties of the quantum dots (e.g., quantum dot size and material composition). Such structures avoid the problems associated with indium doping in small GaN structures.

[0054] In size schemes (i.e., sizes less than 10 micrometers) suitable for augmented reality (AR) displays (e.g., smart glasses) and other applications, the use of undoped GaN or lightly indium-doped GaN LED active regions and photon-pumped quantum dots to create various colors can provide display devices with better uniformity across arrays of micro-LEDs. These arrays can also exhibit higher efficiency than systems based on colored LEDs of relatively heavily indium-doped GaN (e.g., red LEDs containing a higher amount of indium than blue LEDs). Increased efficiency and uniformity are achieved because quantum dots can be fabricated with highly uniform size and material composition. These uniform quantum dots possess correspondingly uniform (i.e., narrow linewidth) emission properties.

[0055] Extracting light emitted by microLEDs becomes increasingly challenging as pixel pitch and microLED size decrease. The disclosed embodiments provide improved optical extraction of photons generated by quantum dots (e.g., along a specific direction), while maintaining high efficiency by avoiding photon loss to the absorption surface. The disclosed system also prevents or reduces pump photons escaping the device, thereby ensuring the purity of the color emitted by a given microLED. This can be achieved by forming optical cavity walls that are reflective, including a light extraction material layer, and incorporating other light extraction structures such as microlenses and / or distributed Bragg reflectors (DBRs).

[0056] Figure 1A is a vertical cross-sectional view of an intermediate structure 100a that can be used to form an array of light-emitting devices according to various embodiments. The intermediate structure 100a may include a plurality of microLEDs 102 formed on a substrate 104. As described above, the microLEDs 102 may include microLEDs having peak emission wavelengths in the UV radiation or blue light spectral region (e.g., microLEDs emitting UV or blue light, also referred to as UV or blue LEDs). These LEDs may include undoped GaN active regions configured to emit ultraviolet (UV) photons and / or photons in the blue spectral range.

[0057] In one embodiment, the microLED 102 may have at least one electrode 103 located on top of the LED and facing away from the substrate 104. The electrode 103 may include an anode or cathode electrode. In one embodiment, the microLED 102 may include a vertical LED, wherein a second electrode (not shown for clarity) is located between the substrate 104 and the bottom of the microLED 102. In another embodiment, the microLEDs may include lateral LEDs, wherein two electrodes are located on the same side of the LED (e.g., on the top or bottom side of the LED).

[0058] The substrate 104 may be a backplane having circuitry (e.g., TFT and / or CMOS circuitry) configured to supply voltage and current to the microLED 102 via electrodes (including electrode 103) to control the emission of light by the microLED 102. The backplane may be an active or passive matrix backplane substrate for driving the LEDs. As used herein, "backplane substrate" refers to any substrate configured to attach multiple devices thereto. In one embodiment, the backplane may include a substrate comprising silicon, glass, plastic, and / or at least other materials that provide structural support for the attached devices. In one embodiment, the backplane substrate may be a passive backplane substrate, in which a metal interconnect structure (not shown) containing metallized lines is present (e.g.) in a cross-grid and dedicated active devices (e.g., TFTs) for each LED are absent. In another embodiment, the backplane substrate may be an active backplane substrate, which includes a metal interconnect structure as a cross grid of conductive lines and additionally includes dedicated active devices (e.g., CMOS transistors or TFTs) for each LED at one or more intersections of the cross grid of conductive lines.

[0059] Figure 1B is a vertical cross-sectional view of another intermediate structure 100b that can be used to form an array of light-emitting devices according to various embodiments. The intermediate structure 100b includes a plurality of optical cavities 106 formed on a micro-LED 102. Each optical cavity is bounded by a cavity wall 108. The optical cavities 106 may be constructed using a reflective material having suitable mechanical properties to form cavities with relatively thin sidewalls 108 and a high aspect ratio (e.g., a diameter of 5 micrometers or less, such as 1 to 2 micrometers, and a height of 10 micrometers or more, such as 20 to 30 micrometers). The cavity walls 108 may have a thickness of less than 10 micrometers, such as 0.5 to 5 micrometers (inclusive of 1 to 2 micrometers). The cavity walls 108 form an insulating matrix.

[0060] Matrix materials can be selected to be compatible with both thermal evaporation processes and solvent-based fluid deposition and evaporation. One such matrix material is alumina, although silicon dioxide, titanium dioxide, or other insulating metal oxide materials can be used. Various materials commonly used in the fabrication of microelectromechanical systems (MEMS) devices can be used to form optical cavities 106 bounded by cavity walls 108 made of electrically insulating materials (e.g., alumina). These materials have relatively high refractive indices and are suitable for forming structures with high aspect ratios. Layers of this matrix material (not shown in FIG1B) can be grown or deposited on a micro-LED 102 array located on a substrate 104, and techniques such as etching and other micromachining methods can be used to create the optical cavities 106 in the material. FIG2A is a top view of a matrix 200a having a plurality of cylindrical optical cavities 106 bounded by cavity walls 108. FIG2B is a top view of a matrix 200b having a plurality of hexagonal optical cavities 106 bounded by cavity walls 108.

[0061] In one embodiment, a voltage can be applied to the anode or cathode electrode 103 of the microLED 102 to form one side of the etch deviation. For example, if the matrix 200a or 200b (i.e., cavity wall 108) contains aluminum oxide, the porous aluminum oxide can be formed by anodizing. In this embodiment, an aluminum metal layer can be deposited on the microLED 102 and then electrochemically anodized to form a porous anodic aluminum oxide matrix having optical cavities (i.e., holes) 106 bounded by the anodic aluminum oxide walls 108. A substrate 104 containing an aluminum layer is placed in an acidic electrolyte (e.g., oxalic acid, chromic acid, sulfuric acid, and / or phosphoric acid), and a voltage is applied to the electrodes 103 and / or external electrodes of the microLED 102 to form a porous anodic aluminum oxide matrix containing optical cavities (i.e., holes) 106 bounded by the aluminum oxide cavity walls 108. The optical cavities 106 can be arranged in a hexagonal array within the anodic aluminum oxide matrix.

[0062] Figure 1C is a vertical cross-sectional view of another intermediate structure 100c that can be used to form an array of light-emitting devices according to various embodiments. The intermediate structure 100c may include a light-extracting material layer 110 and color-converting materials (112a, 112b, 112c, 112d) formed in an optical cavity 106 on an array of micro-LEDs 102. The light-extracting material layer 110 may have a refractive index lower than that of the material forming the cavity wall 108. For example, the light-extracting material layer 110 may have a refractive index less than 1.7, such as 1.3 to 1.5, relative to the alumina cavity wall 108. The lower refractive index of the light-extracting material layer 110 causes pump photons (i.e., photons generated by the micro-LEDs 102) to be reflected from the cavity wall 108 rather than absorbed by or transmitted through the cavity wall 108. This reflection prevents photon loss, thereby increasing the quantum efficiency of the device.

[0063] Various polymer materials can be used as the light extraction material layer 110. One such polymer is Jet-144 (i.e., an inkjet-compatible polymer), which has a refractive index of 1.44 and can be deposited into the optical cavity 106 using an inkjet system. The thickness of the cavity wall 108 is configured to be as thick as possible to increase the likelihood that photons not reflected from the cavity wall 108 will be absorbed (extinguished) so that they do not penetrate into adjacent cavities.

[0064] The light extraction material layer 110 can be deposited using various techniques, including inkjet, vacuum, pressure, and / or gravity deposition. After deposition, the polymer can be cross-linked, for example, by exposure to ultraviolet (UV) radiation. In other embodiments, the solvent dissolving the polymer can be evaporated, leaving residual cross-linked polymer as the light extraction material layer 110 in each cavity. In various embodiments, the light extraction material layer 110 can be formed to various thicknesses and may or may not contain additional light scattering materials, such as TiO2 or SiO2 nano or microbeads. The light extraction material layer 110 partially fills the optical cavity 106 such that the cavity space remains on top of the light extraction material layer 110 in each cavity.

[0065] The color conversion materials (112a, 112b, 112c, 112d) can then be formed in the optical cavity 106 (e.g., see FIG. 1B) on the light extraction material layer 110 (e.g., see FIG. 1C). The color conversion materials (112a, 112b, 112c, 112d) can contain quantum dots corresponding to various different colors. In this example, the color conversion materials (112a, 112b, 112c, 112d) can contain a plurality of first quantum dots 112a, a plurality of second quantum dots 112b, a plurality of third quantum dots 112c, and a plurality of fourth quantum dots 112d, configured to convert UV-pumped photons into photons having corresponding first, second, third, and fourth colors. The second and third colors can contain different peak wavelengths within the green spectral range. Alternatively, only three quantum dot colors can be used. Quantum dots can comprise compound semiconductor materials, such as Group III-V semiconductor materials (e.g., indium phosphide, as described in U.S. Patent No. 9,884,763 B1, the entire contents of which are incorporated herein by reference), Group II-VI semiconductor materials (e.g., ZnSe, ZnS, ZnTe, CdS, CdSe, etc., core-shell quantum dots, as described in U.S. Patent Application Publication US 2017 / 0250322 A1, the entire contents of which are incorporated herein by reference), and / or Group I-III-VI semiconductor materials (e.g., AgInGaS / AgGaS core-shell quantum dots, as described in U.S. Patent No. 10,927,294 B2, the entire contents of which are incorporated herein by reference) in the range of 1 to 10 nm, such as 2 to 8 nm nanometer crystals. Quantum dots can emit different colors of light (e.g., red, green, or blue), depending on their diameter. Larger dots emit longer wavelengths of light, while smaller dots emit shorter wavelengths of light. The quantum dots can be suspended in a material (e.g., a polymer, such as polyimide) having a different (e.g., higher) refractive index than the light extraction material 110. For example, the polyimide material can have a refractive index of 1.6 to 1.75, such as about 1.7.

[0066] As described in more detail below (for example, referring to Figures 3A to 4P), quantum dots corresponding to various colors can be selectively deposited in their respective cavities. For example, as described below with reference to Figures 3A to 3L, a first cavity can be formed by etching a first via in a matrix material. A first quantum dot corresponding to a first color can then be introduced into the first cavity, and a protective material layer can then be formed on the first quantum dot. This process can then be repeated to form a second cavity, a third cavity, etc., and to introduce second quantum dots, third quantum dots, etc., into their respective cavities.

[0067] In other embodiments (e.g., see Figures 4A to 4P), photoresist can be deposited on all cavities except for the plurality of first cavities. A first quantum dot layer configured to produce a first color (e.g., red) can then be deposited into the plurality of first cavities corresponding to sub-pixels having the first color. The polymer in which the first quantum dots are suspended can then be crosslinked by evaporation or by exposure to UV light. This process can then be repeated for other optical cavities to deposit quantum dots configured to produce other colors of light (e.g., green and blue) respectively.

[0068] An optical organic planarization layer can be formed on the color conversion material. The color conversion material and the optical organic planarization layer can partially fill the optical cavity 106.

[0069] Figure 1D is a vertical cross-sectional view of a light-emitting device array 100d according to various embodiments. As shown, array 100d may include a color selector 114 formed in and / or thereon within an optical cavity 106. The color selector 114 may include a color filter array and / or a distributed Bragg reflector. In one embodiment, the color selector 114 may be formed in the optical cavity and may extend to the top of the cavity wall 108 such that the optical cavity 106 is completely filled with the aforementioned material.

[0070] Color conversion materials (112a, 112b, 112c, 112d) may be configured to absorb pump photons 118 and convert them into emitted converted photons (e.g., visible light, such as red, green, or blue light) 120. In some embodiments, the color conversion materials (112a, 112b, 112c, 112d) may not be thick enough and / or dense enough to completely convert all pump photons 118 into converted photons 120. Therefore, a color selector 114 formed on the color conversion materials (112a, 112b, 112c, 112d) absorbs and / or reflects all or part of the pump photons 118 that are not converted by the color conversion materials (112a, 112b, 112c, 112d), but does not absorb and / or reflect the converted photons 120 emitted by the color conversion materials.

[0071] Each of the microLEDs 102 can be configured to emit pump photons 118 within a range of common or target wavelengths. For example, a GaN-based microLED 102 can emit pump photons 118 with wavelengths of 400 to 410 nm, such as about 405 nm (i.e., in the blue or near-UV portion of the electromagnetic spectrum). The microLEDs 102 can exhibit high uniformity and high efficiency. However, slight variations in the wavelength of these microLEDs 102 are not easily visible to the eye. In addition, any leakage of pump photons 118 through the color conversion materials (112a, 112b, 112c, 112d) can cause minimal degradation in the color purity of the converted photons 120.

[0072] In one embodiment, the color selector 114 includes a color filter array comprising an organic dye embedded in an organic polymer. The dye may be configured to absorb UV radiation from pump photons 118, but not to absorb blue, green, or red light from converted photons. Depending on the application, different dyes may be applied to each of the color sub-pixels (e.g., red, green, and blue sub-pixels). For example, a first dye filter material configured to primarily transmit red light may be applied to the red sub-pixel, a second dye filter material configured to primarily transmit green light may be applied to the green sub-pixel, and a third dye filter material configured to primarily transmit blue light may be applied to the blue sub-pixel. The color filters may be formed using additional photolithography processes. In various embodiments, a thin-film encapsulation (TFE) layer or layer stack may then be applied to the color filter material to provide protection against air or moisture ingress into the quantum dot layer of the color conversion material. In one embodiment, the TFE may comprise a three-layer stack of two silicon nitride layers separated by a polymer layer.

[0073] In an alternative embodiment, the color selector 114 includes a distributed Bragg reflector (DBR) formed on a color conversion material (112a, 112b, 112c, 112d). The DBR can be configured to reflect pump photons 118 transmitted through the color conversion material as reflected photons 122 (e.g., UV or deep blue photons) back to cavity 106 and to allow converted photons 120 to propagate from cavity 106. The DBR can be formed as an alternating stack of multiple layers (not shown) of materials with different refractive indices. For example, the DBR can be formed as an N-layer stack alternating between TiO2 (n=2.5) and SiO2 (n=1.5), where N is 2 or greater. In other embodiments, various other materials having their own refractive indices can be used to construct the DBR.

[0074] Embodiments of the DBR comprising TiO2 and SiO2 (where N = 2) can have a bandwidth of 164 nm at a center wavelength of 405 nm and a maximum reflectivity R of 84%. Embodiments of the DBR stack comprising more layers (i.e., N > 2) can have increased reflectivity. Thus, the likelihood of UV pump photons 118 passing through the DBR can be reduced. UV reflected photons 122 reflected from the DBR back to cavity 106 can be circulated through the color conversion materials (112a, 112b, 112c, 112d) and thus have an increased likelihood of being converted into converted photons 120 with the target wavelength (e.g., green, blue, or red). In this way, any UV reflected photons 122 that were not initially absorbed by the color conversion materials (112a, 112b, 112c, 112d) can eventually be absorbed and converted into converted photons 120 with the target emission wavelength. This process (sometimes called "photon recycling") can increase the quantum efficiency of a device.

[0075] If the micro-LED 102 includes an LED that emits shorter wavelength blue light, then the DRB 114 can block the shorter wavelength blue light of the micro-LED 102 (i.e., pump photons 118), but transmit the longer wavelength conversion photons 120 emitted from the blue quantum dots of the color conversion material. Alternatively, the DBR 114 can be omitted from the blue photon-emitting sub-pixel.

[0076] This DBR can be formed by deposition (e.g., by evaporation) of multiple stacks (not shown) on all subpixels. Therefore, the DBR provides additional protection against moisture and oxygen ingress into the quantum dot layer. Higher values ​​of N can further increase the DBR reflectivity and protect against moisture and oxygen, resulting in improved overall system performance and durability.

[0077] In various other embodiments, other materials can be used for various components of the device. For example, the DBR can comprise a wide range of materials, each with its own refractive index, such as nitrides (TiN, AlN, TiN, etc.), polycrystalline silicon, etc. Some embodiments may include multiple quantum dot layers, multiple DBR structures, etc. In some embodiments, the light extraction material layer 110 described above may be omitted or multiple light extraction material layers 110 may be used. By using a more efficient DBR 114, the layer thickness and density of the color conversion materials (112a, 112b, 112c, 112d) can be reduced. In other embodiments, the optical cavity 106 can be formed in various ways. For example, the optical cavity 106 can be formed in a separate matrix layer, which can then be attached to an array of micro-LEDs 102 after the optical cavity 106 is formed, as described in more detail below. Other embodiments may also include a light collimating element to mitigate performance degradation that could otherwise occur due to lateral photon propagation.

[0078] Figure 1E is a vertical cross-sectional view of another array 100e of a light-emitting device according to various embodiments. As shown, the light-emitting device array 100e includes microlenses 124 formed on an optical cavity 106. Each microlens 124 helps improve light extraction from each microLED structure and thus improves the efficiency of the array 100e. Generally, light extraction from microLEDs becomes increasingly challenging as pixel pitch and microLED size decrease. In this regard, sufficiently thick color conversion materials (112a, 112b, 112c, 112d) can be selected to convert all pump photons 118 into converted photons 120 each having a specific color. The thickness of the color conversion materials (112a, 112b, 112c, 112d) can be very large compared to the side dimension of the sub-pixel. In this structure, photons can diffuse away from the microLED sub-pixels instead of being emitted. This diffused photons can diffuse to adjacent sub-pixels, potentially causing optical crosstalk.

[0079] The disclosed embodiments provide improved optical extraction of photons generated by quantum dots (e.g., along a specific direction) while maintaining high efficiency by avoiding photon loss to the absorption surface. As described above, this can be achieved by forming a matrix structure comprising cavity walls 108, which are reflective, comprising a light extraction material layer 110, and / or comprising a color selector 114, such as a DBR.

[0080] Quantum dots used as color conversion materials in microLED displays (112a, 112b, 112c, 112d) can comprise the deposition and patterning of dense quantum dot layers with extremely small feature sizes. To achieve sufficient absorption of pump photons 118 (e.g., see Figures 1D and 1E) in the quantum dot layer, sub-pixels with an aspect ratio greater than 1:1 can be used. These sub-pixels can also be separated by cavity walls 108 formed from an opaque matrix material to prevent color crosstalk in the display (i.e., photons from one microLED propagating to adjacent sub-pixels).

[0081] The high concentration of quantum dots used as color conversion materials (112a, 112b, 112c, 112d) presents another challenge for fabricating high-resolution structures. Because quantum dots strongly absorb UV light, they can reduce the activity of photoinitiators or photoacid generators commonly used in photoresists. Therefore, the presence of quantum dots may necessitate modifications to conventional manufacturing materials and methods. Consequently, patterning tall and thin structures can be more difficult when using high-concentration quantum dots. The disclosed embodiments address this issue by forming cavities, such as through-holes etched in a matrix material, as described in more detail below with reference to Figures 3A to 4P.

[0082] Various embodiments include matrices, such as matrix 200a or 200b, which allow for better light extraction from each sub-pixel and reduce photon color crosstalk. Using a matrix as a template and sequentially opening vias corresponding to different color sub-pixels allows for the deposition and curing of quantum dot inks without relying on high-resolution photopatternable resin formulations. The various embodiments described below involve opening vias corresponding to one color in the matrix layer, filling with quantum dot ink, curing and encapsulating, and then repeating the same process with a second color, a third color, and so on.

[0083] Figures 3A to 3L are vertical cross-sectional views that can be used to form intermediate structures for light-emitting device arrays according to various embodiments. As shown in Figure 3A, a continuous matrix layer 304L can be deposited on the support 302. In one embodiment, the continuous matrix layer 304L can have a thickness of about 10 to 30 micrometers. The matrix layer 304L can contain an insulating material (such as silicon dioxide, aluminum oxide, titanium dioxide, etc.) to form the optical cavity wall 108 described above with respect to Figure 1B. Alternatively, the matrix layer 304L can contain a metal, such as aluminum, and then anodize it to form anodized aluminum oxide. In another alternative embodiment, the matrix layer 304L can be a reflective metal that has not been converted into a metal oxide, such as aluminum. In this alternative embodiment, the matrix layer 304L is formed on the microLED 102 in a manner that avoids short-circuiting the corresponding electrodes of adjacent microLEDs 102.

[0084] The support 302 may include the backplate 104 that supports the micro-LED 102 as described above with respect to FIG. 1A. In an alternative embodiment, the support 302 may include a separate substrate, such as a transparent glass or polymer substrate, which is subsequently attached to the backplate 104 that supports the micro-LED 102.

[0085] As shown in Figure 3B, the patterned masking material 306 can be formed on the continuous matrix layer 304L. In one embodiment, the patterned masking material 306 can be a photoresist and can be patterned using photolithography.

[0086] The continuous matrix layer 304L (e.g., see FIG. 3A) can be etched to form an etched matrix layer 304 including a first via 308a. In an exemplary embodiment, the continuous aluminum matrix layer 304L can be etched using a BCl3 dry etching process. The first via 308a may correspond to the optical cavity 106 of a first plurality of sub-pixels. For example, the first plurality of sub-pixels may correspond to a first color (e.g., red, green, or blue). After etching, the patterned masking material 306 can be removed.

[0087] As shown in Figure 3C, the patterned masking material 306 (e.g., see Figure 3B) and the superhydrophobic (i.e., non-stick) coating 310 can be replaced. Coating 310 may include a fluorinated silane coating, such as inorganic nanoparticles functionalized with fluoroalkyl silane groups (e.g., silicon dioxide nanoparticles). Quantum dot ink having a plurality of first quantum dots 112a can then be deposited to fill the first vias 308a by spin coating, doctor-blading, inkjet printing, or other methods, as shown in Figure 3D. The fluorinated coating 310 ensures that most quantum dots do not stick to the upper surface of the structure. The quantum dot ink can then be cured by UV radiation or by heat. The fluorinated coating 310 and excess quantum dots can then be washed away, as shown in Figure 3E.

[0088] A protective layer 314 can then be formed on the first quantum dot 112a, as shown in FIG3F. For example, the protective layer 314 can be an alumina layer, which can be deposited by atomic layer deposition (ALD). In an exemplary embodiment, the protective layer 314 can have a thickness of 3 to 10 nm, such as about 5 nm. Other embodiments may include other thicknesses of the protective layer 314, other materials, and other deposition methods.

[0089] The above process can then be repeated (e.g., see Figures 3A to 3F) to deposit and cure quantum dot inks of other colors. For example, a patterned masking material 306 can be formed on the intermediate structure of Figure 3F, and an etching process can be performed to form a second via 308b through the protective layer 314, as shown in Figure 3G. The patterned masking material 306 and the superhydrophobic (i.e., non-stick) fluorinated coating 310 can be removed and replaced, as shown in Figure 3H. The quantum dot ink having a plurality of second quantum dots 112b (i.e., different colored dots from dot 112a) can then be deposited by spin coating, blade coating, inkjet printing or other methods to fill the second via 308b, as shown in Figure 3I. The fluorinated coating 310 and excess quantum dots can then be washed away, as shown in Figure 3J. A second protective layer having a first portion 314a and a second portion 314b can then be formed on the second quantum dots 112b, as shown in Figure 3K. The first portion 314a can be formed on the existing first protective layer 314, while the second portion 314b can be formed on the second through-hole 308b filled with the second quantum dot 112b.

[0090] Similarly, the process can continue to form a third via 308c, as shown in FIG3L. The third via 308c can be filled with a third quantum dot ink containing a third quantum dot 112c (not shown in the figure). In various embodiments, the process can continue to form additional vias that can be filled with quantum dots corresponding to other respective colors.

[0091] If the support 302 includes a transparent substrate, then the support 302 supporting the completed matrix containing quantum dots can then be attached to the backplate 104 supporting the micro LED 102. If the support 302 includes the backplate 104 supporting the micro LED 102, then the etched matrix layer 304 includes cavity walls 108 surrounding the optical cavity 106 filled with quantum dots (112a, 112b, etc.).

[0092] Figures 4A to 4P are vertical cross-sectional views of additional intermediate structures that can be used to form arrays of light-emitting devices according to various embodiments. The processes in Figures 4A to 4P include providing a matrix layer on a support, depositing a planar positive photoresist layer, and selectively exposing and removing this photoresist to sequentially open vias. The processes in Figures 4A to 4P rely on the removal of the photoresist to form an optical cavity. Therefore, in some embodiments, the second process flow (i.e., hereinafter described with reference to Figures 4A to 4P) can be more functional, cheaper, and safer.

[0093] As shown in Figure 4A, the first intermediate structure may be comprised of a continuous matrix layer 108L formed on the aforementioned support 302. The matrix layer 108L may include an insulating layer, such as aluminum oxide, silicon dioxide, titanium dioxide, etc., or a conductive layer, such as a metal layer, for example, aluminum. A patterned photoresist 406 may be formed on the continuous matrix layer 108L. In this regard, a cover layer (not shown) for the photoresist may be formed on the continuous matrix layer 108L and may be patterned using photolithography to form the patterned photoresist 406.

[0094] As shown in Figure 4B, using a patterned photoresist 406 as a mask layer, the continuous matrix layer 108L can be etched to form vias or cavities (e.g., optical cavities) 106 bounded by cavity walls 108, as shown in Figure 4B. The patterned photoresist 406 can then be removed by ashing or by solvent dissolution.

[0095] In an alternative embodiment, instead of etching the continuous matrix layer 108L, the cavity wall 108 can be formed by anodizing. As described above, if the continuous matrix layer 108L contains aluminum, it can be anodized in acid as described above to form a porous anodic aluminum oxide layer containing the cavity wall 108 surrounding the optical cavity (i.e., the hole) 106.

[0096] As shown in Figure 4C, a positive photoresist having a first photoresist portion 408a, a second photoresist portion 408b, and a third photoresist portion 408c can then be deposited onto the intermediate structure of Figure 4B into the optical cavity 106. Each photoresist portion fills its respective optical cavity 106.

[0097] As shown in Figure 4D, a patterned mask 410 and a UV radiation source (e.g., a UV-emitting lamp) 412, optionally selected as needed, can be used to selectively expose the first photoresist portion 408a of the positive photoresist passing through the mask 410 to UV radiation 414. Exposure of the first photoresist portion 408a makes it soluble in a photoresist developer, which can be used to remove the first photoresist portion 408a. The second and third photoresist portions are not exposed to UV radiation.

[0098] Alternatively, if the support 302 includes a backplate 104 supporting the micro-LED 102 emitting UV radiation, the micro-LED 102 located under the first photoresist portion 408a can be activated to irradiate the first photoresist portion 408a with UV radiation from the bottom, making the portion 408a soluble in the developer. In this alternative embodiment, the mask 410 and the radiation source 412 can be omitted. The micro-LED 102 located under the second and third photoresist portions 408b and 408c is not activated.

[0099] As shown in Figure 4E, the first through-hole 416a can be generated by immersing the structure in a photoresist developer bath or by spraying positive photoresist with a developer solution to remove the first photoresist portion 408a without removing the other photoresist portions 408b and 408c.

[0100] As shown in Figure 4F, the first quantum dot ink 418a can then be introduced into the first via 416a. The first via 416a can then be filled with a uniform layer of the first quantum dots 112a. The polymer in which the first quantum dots 112a are suspended can then be thermocured or cured by exposure to UV radiation. For example, Figure 4G illustrates that the first quantum dots 112a are selectively exposed to UV radiation using a patterned mask 410 and a UV radiation source 412. Alternatively, a micro-LED 102 emitting UV radiation under the first quantum dots 112a can be activated to irradiate the first quantum dots 112a with UV radiation.

[0101] The above-described process shown in Figures 4C to 4G can then be repeated to form the second quantum dot 112b in the second optical cavity 106. In this regard, the second photoresist portion 408b of the positive photoresist shown in Figure 4C can be exposed to UV radiation from the UV radiation source 412 or the micro-LED 102, as shown in Figure 4H. The second photoresist portion 408b of the positive photoresist can then be removed using a photoresist developer to create a second via 416b, as shown in Figure 4I. The second quantum dot ink 418b can then be introduced into the second via 416b to form a uniform layer of the second quantum dot 112b, as shown in Figure 4J. The uniform layer of the second quantum dot 112b can then be cured by exposure to UV radiation from the UV radiation source 412 or the micro-LED 102, as shown in Figure 4K.

[0102] The above-described process shown in Figures 4C to 4G can then be repeated to form the third quantum dot 112c in the third optical cavity 106. In this regard, the third photoresist portion 408c of the positive photoresist can be exposed to UV radiation from the UV radiation source 412 or the micro-LED 102, as shown in Figure 4L. The third photoresist portion 408c of the positive photoresist can then be removed using a photoresist developer to create a third via 416c, as shown in Figure 4M. The third quantum dot ink 418c can then be introduced into the third via 416c to form a uniform layer of the third quantum dot 112c, as shown in Figure 4N. The uniform layer of the third quantum dot 112c can then be thermally cured or cured by exposure to UV radiation from the UV radiation source 412 or the micro-LED 102, as shown in Figure 4O.

[0103] Finally, a protective layer 314 can be formed on the uniform layers of the first quantum dot 112a, the second quantum dot 112b, the third quantum dot 112c, and the cavity wall 108, as shown in FIG4P. As described above, the protective layer 314 can be an alumina layer deposited by ALD. Other materials and deposition processes can be used to deposit the protective layer 314 and / or the color selector 114 (e.g., DBR), as described above.

[0104] In the above embodiments, the shape of the sub-pixels in the light-emitting device array can be defined by the geometry of the cavities / vias. Therefore, the patternability requirements for the quantum dot inks (418a, 418b, 418c) are significantly less stringent than those for embodiments not dependent on a matrix template. In some embodiments, UV-curable quantum dot inks can be used to confine quantum dots to target sub-pixels. In other embodiments, thermosetting inks can also be used. The use of UV-curable or thermosetting quantum dot inks enhances the selection of chemicals that can be used to form (quantum dot-based) color conversion materials (112a, 112b, 112c, 112d).

[0105] Various embodiments may include solvent-based or solvent-free quantum dot inks. The use of thermosetting quantum dot inks in each sub-pixel allows the omission of photocurable acrylates / epoxides for ink formulations. In other embodiments, quantum dot inks may be formed using inorganic ligands and matrix materials (e.g., metal chalcogenides and metal oxides), which may provide alternative benefits such as high-temperature stability.

[0106] Figures 5A to 5G are vertical cross-sectional views of additional intermediate structures that can be used to form arrays of light-emitting devices according to various embodiments. As shown in Figure 5A, a plurality of microLEDs 102 can be formed on a substrate 104. The substrate 104 may be a backplane having circuitry (e.g., CMOS or TFT circuitry) configured to supply voltage to the microLEDs 102 to control the light emission by the microLEDs 102. As described above, the microLEDs 102 may comprise LEDs emitting blue or UV light. The intermediate structure of Figure 5A may include a common cathode 502 of a plurality of microLEDs 102 formed from a transparent conductive oxide (e.g., indium tin oxide) and individual anodes 503 of each microLED 102 electrically connected to its respective backplane circuitry (not shown for clarity). Thus, the plurality of microLEDs 102 are short-circuited on their cathode (e.g., n-type) side, but are individually activated by the backplane circuitry on their anode (e.g., p-type) side. The common cathode 502 is also connected to the backplane circuitry outside the region of the microLEDs 102.

[0107] In one embodiment, the micro-LED 102 may comprise a vertical LED having cathode and anode electrodes (502, 503) located on opposite sides of the LED. In one embodiment, the micro-LED 102 may have an inverted cone shape. In other words, the micro-LED 102 may be wider on its bottom side facing the anode 503 and the backplate 104 than on its top side facing the common cathode 502.

[0108] As shown in Figure 5B, a first color conversion material (e.g., a first color quantum dot) 504a can be formed on a first plurality of microLEDs 102. The first color conversion material 504a can be formed by an inkjet process, which can be used to directly print only first quantum dot ink onto a first portion of the common cathode 502 on each microLED 102 in the first color sub-pixel. Alternatively, a continuous quantum dot layer can be deposited directly on the common cathode, followed by photolithography and patterning to leave only the first color quantum dots 504a on each microLED 102 in the first color sub-pixel.

[0109] As shown in Figure 5C, the second color conversion material 504b can be formed on the second plurality of microLEDs 102. The second color conversion material 504b can be formed by an inkjet process that allows direct printing of the second quantum dot ink onto the second portion of the common cathode 502 on each microLED 102, or by depositing a continuous quantum dot layer followed by photolithography patterning. The color conversion material can be omitted on the blue-emitting microLED 102. Alternatively, the blue conversion material can be formed on the UV-emitting microLED 102. Finally, a color selector 114 can be formed on the first color conversion material 504a and the second color conversion material 504b. For example, the color selector 114 can be a DBR, as described above. If desired, an encapsulation layer (such as an aluminum oxide layer) can be formed on the color selector 114.

[0110] Alternatively, the intermediate structures of Figures 5B and 5C can be formed using a process similar to that described above with reference to Figures 4A to 4P. In this regard, a patterned photoresist (not shown) can be formed on the common cathode 502 and can be used as a mask material for depositing the first color conversion material 504a. In this regard, the mask material may include openings corresponding to the locations on which the first color conversion material 504a is to be deposited. After the first color conversion material 504a has been deposited and cured, the photoresist can be patterned to form openings, etc., corresponding to the locations on which the second color conversion material 504b is to be deposited.

[0111] In another embodiment, the intermediate structure of Figures 5D and 5E can be formed by forming an etch stop layer 508 on the common cathode 502 of the structure of Figure 5A. A first color conversion material 504a and a second color conversion material 504b can then be deposited, as shown in Figures 5D and 5E. The etch stop layer 508 may comprise silicon oxide or other similar etch stop materials. The presence of the etch stop layer 508 protects the transparent conductive oxide formed on the common cathode 502 during the photoresist etching process.

[0112] The process for forming alternative intermediate structures of Figures 5F and 5G can be similar to the process for forming intermediate structures of Figures 5D and 5E from the intermediate structure of Figure 5A. In this regard, each of the intermediate structures of Figures 5F and 5G can include the etch stop layer 508 of Figures 5D and 5E formed on the common cathode 502 of Figure 5A. The intermediate structures of Figures 5F and 5G can also include an optical cavity 106 bounded by cavity walls 108. If the micro-LED 102 includes a blue LED, the optical cavity 106 on the blue sub-pixel can remain unfilled. Therefore, the intermediate structures of Figures 5F and 5G can be similar to the embodiments of Figures 1B to 1E, Figure 3L, and Figures 4B to 4P.

[0113] The prior description of the disclosed embodiments is provided to enable those skilled in the art to make or use the disclosed embodiments. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not intended to be limited to the embodiments shown herein, but is accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

[0114] 100a: Intermediate structure 100b: Intermediate structure 100c: Intermediate structure 100d: Light-emitting device array 100e: Light-emitting device array 102: Miniature LED 103: Electrode 104:Substrate 106: Optical cavity 108: Cavity wall 108L: Continuous Matrix Layer 110: Light extraction material layer 112a: Color conversion material / First quantum dot 112b: Color conversion material / second quantum dot 112c: Color conversion material / Third quantum dot 112d: Color conversion material / fourth quantum dot 114: Color Picker 118: Pump Photon 120: Converted photons 122:Reflected photon 124: Microlenses 200a: Matrix 200b: Matrix 302: Support 304: Etched matrix layer 304L: Continuous Matrix Layer 306: Patterned masking material 308a: First through hole 308b: Second through hole 308c: Third through hole 310: Fluorinated coating 314: Protective layer 314a: Part 1 314b: Part Two 406: Patterned photoresist 408a: First photoresist section 408b: Second photoresist section 408c: Third photoresist section 410: Patterned mask 412: UV radiation source 414: UV radiation 416a: First through hole 416b: Second through hole 416c: Third through hole 418a: First Quantum Dot Ink 418b: Second Quantum Dot Ink 418c: Third Quantum Dot Ink 502: Common Cathode 503: Anode 504a: First color conversion material / First color quantum dot 504b: Second color conversion material 508: Etching Stop Layer

Claims

1. A method for forming an array of light-emitting devices, comprising: A first through-hole is formed in the matrix material; a first complex number of quantum dots corresponding to a first color are deposited in the first through-hole; A second through-hole is formed in the matrix material; a second plurality of quantum dots corresponding to a second color are deposited in the second through-hole; a third through-hole is formed in the matrix material; and a third plurality of quantum dots corresponding to a third color are deposited in the third through-hole; wherein the first plurality of quantum dots are located on a first light-emitting diode, the second plurality of quantum dots are located on a second light-emitting diode, and the third plurality of quantum dots are located on a third light-emitting diode.

2. The method of request item 1, further comprising: Before forming the second through-hole in the matrix material, a first protective layer is formed on the first plurality of quantum dots; Before forming the third through-hole in the matrix material, a second protective layer is formed on the second plurality of quantum dots.

3. The method of request item 1, further comprising: During the same positive photoresist deposition step, a first positive photoresist portion is formed in the first via, a second positive photoresist portion is formed in the second via, and a third positive photoresist portion is formed in the third via, wherein the formation of the first via, the second via, and the third via in the matrix material occurs during the same via formation step; before depositing the first plurality of quantum dots in the first via, the first positive photoresist portion covering the first via is selectively exposed and removed; after depositing the first plurality of quantum dots in the first via and before depositing the second plurality of quantum dots in the second via, the second positive photoresist portion covering the second via is selectively exposed and removed; and after depositing the second plurality of quantum dots in the second via and before depositing the third plurality of quantum dots in the third via, the third positive photoresist portion covering the third via is selectively exposed and removed.

4. As in request item 3, where: The first light-emitting diode, the second light-emitting diode, and the third light-emitting diode are located on the backplate; the matrix material is formed on the first light-emitting diode, the second light-emitting diode, and the third light-emitting diode before the first through-hole, the second through-hole, and the third through-hole are formed in the matrix material; selectively exposing the first positive photoresist portion includes activating the first light-emitting diode to expose the first positive photoresist portion; selectively exposing the second positive photoresist portion includes activating the second light-emitting diode to expose the second positive photoresist portion; and selectively exposing the third positive photoresist portion includes activating the third light-emitting diode to expose the third positive photoresist portion.

5. As in request item 1, where: The first light-emitting diode, the second light-emitting diode, and the third light-emitting diode are located on the back plate; the matrix material is formed on the first light-emitting diode, the second light-emitting diode, and the third light-emitting diode before the first through-hole, the second through-hole, and the third through-hole are formed in the matrix material; and the matrix material comprises a metal or metal oxide layer.

6. As in request item 5, wherein: The matrix material is formed as an aluminum layer on the first light-emitting diode, the second light-emitting diode, and the third light-emitting diode; and forming the first through hole, the second through hole, and the third through hole in the matrix material includes anodic oxidation of the aluminum layer by applying a voltage to the electrodes of the first light-emitting diode, the second light-emitting diode, and the third light-emitting diode in an acid bath to form an aluminum oxide matrix material.

7. The method of claim 1, further comprising: A first color selector is formed on the first plurality of quantum dots in the first through-hole; A second color selector is formed on the second plurality of quantum dots in the second through-hole; and a third color selector is formed on the third plurality of quantum dots in the third through-hole.

8. The method of claim 7, wherein the first color selector, the second color selector and the third color selector include an organic dye filter embedded in an organic polymer.

9. The method of claim 7, wherein the first color selector, the second color selector, and the third color selector include a distributed Bragg reflector.

10. The method of claim 7, further comprising forming a light extraction material on the first light-emitting diode, the second light-emitting diode, and the third light-emitting diode prior to forming the first color selector, the second color selector, and the third color selector, wherein the light extraction material has a first refractive index that is less than the second refractive index of the matrix material.

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