Light emitting device including quantum dot color conversion material and method for producing same

Abstract

1. A light-emitting device comprising: a first optical cavity bounded by cavity walls; a first light-emitting diode disposed within the first optical cavity and configured to emit first incident photons of blue or ultraviolet radiation; a first color conversion material located over 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 a peak wavelength of the first incident photons; and a first color selector disposed over 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 application claims priority to U.S. Provisional Patent Application No. 63 / 279,964, filed November 16, 2021, the entire contents of which are incorporated herein by reference. FIELD OF THE DISCLOSURE This disclosure relates to light emitting devices, and in particular to light emitting diodes formed with color conversion materials within an optical cavity, and methods for their manufacture. [Background technology]

[0002] Light emitting elements are used in electronic displays, such as backlighting for LCD displays in laptops and televisions. Light emitting elements include light emitting diodes (LEDs) and many other types of electronic devices that are configured to emit light.

[0003] For light-emitting devices such as LEDs, the emission wavelength is determined by the bandgap of the LED's active region, along with size-dependent quantum confinement effects. The active region often contains one or more bulk semiconductor layers and / or quantum wells (QWs). For III-nitride LED devices, such as GaN-based devices, the material of the active region (e.g., bulk semiconductor layers or QW well layers) is InN. x Ga 1-x N, where 0 <x<1である。

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

[0005] In one embodiment, the light-emitting element includes a first optical cavity bounded by at least one first cavity wall, a first light-emitting diode disposed within the first optical cavity and configured to emit first incident photons of blue or ultraviolet radiation, 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 the peak wavelength of the first incident photons, and a first color selector disposed 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 method of forming a light emitting device array 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 material 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 material 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 material layer corresponding to a third color, where the first plurality of quantum dots are disposed over a first light emitting diode, the second plurality of quantum dots are disposed over a second light emitting diode, and the third plurality of quantum dots are disposed over a third light emitting diode. [Brief description of the drawings]

[0007] [Figure 1A] FIG. 1A is a side cross-sectional view of an intermediate structure that may be used in constructing a light-emitting device array, according to various embodiments. [Figure 1B] FIG. 1B is a side cross-sectional view of a further intermediate structure that may be used in constructing a light-emitting device array, according to various embodiments. [Figure 1C] FIG. 1C is a side cross-sectional view of a further intermediate structure that may be used in constructing a light-emitting device array, according to various embodiments. [Figure 1D] FIG. 1D is a side cross-sectional view of a light-emitting element array according to various embodiments. [Figure 1E] FIG. 1E is a side cross-sectional view of a further light emitting element array according to various embodiments. [Figure 2A] FIG. 2A is a top perspective view of a first patterned matrix having a plurality of vias formed therein, according to various embodiments. [Figure 2B] FIG. 2B is a top perspective view of a second patterned matrix, the first patterned matrix having a plurality of vias formed therein, according to various embodiments. [Figure 3A] FIG. 3A is a side cross-sectional view of an intermediate structure that may be used to form a light-emitting device array, according to various embodiments. [Figure 3B] FIG. 3B is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3C] FIG. 3C is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3D] FIG. 3D is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3E] FIG. 3E is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3F] FIG. 3F is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3G] FIG. 3G is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3H] FIG. 3H is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3I]FIG. 3I is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3J] FIG. 3J is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3K] FIG. 3K is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 3L] FIG. 3L is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4A] FIG. 4A is a side cross-sectional view of an intermediate structure that may be used to form a light-emitting device array, according to various embodiments. [Figure 4B] FIG. 4B is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4C] FIG. 4C is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4D] FIG. 4D is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4E] FIG. 4E is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4F] FIG. 4F is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4G] FIG. 4G is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4H] 4H is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4I] FIG. 4I is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4J]FIG. 4J is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4K] FIG. 4K is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4L] FIG. 4L is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4M] 4M is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4N] FIG. 4N is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4O] FIG. 4O is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 4P] FIG. 4P is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 5A] FIG. 5A is a side cross-sectional view of an intermediate structure that may be used to form a light-emitting device array, according to various embodiments. [Figure 5B] FIG. 5B is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 5C] FIG. 5C is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 5D] FIG. 5D is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 5E] FIG. 5E is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 5F] FIG. 5F is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. [Figure 5G]FIG. 5G is a side cross-sectional view of a further intermediate structure that may be used in forming a light-emitting device array, according to various embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A display device, such as a direct-view display, may be formed from an array of pixels. Each pixel may include a collection of subpixels that emit light at a respective peak wavelength. For example, a pixel may include red, green, and blue subpixels. Each subpixel may include one or more light-emitting diodes that emit light at a particular wavelength. A conventional arrangement is to have red, green, and blue (RGB) subpixels within each pixel. Each pixel is driven by a backplane circuit such that any combination of colors within the color gamut may be displayed on the display for each pixel. A display panel may be formed by a process of soldering or otherwise electrically attaching LED subpixels to bond pads on a backplane. The bond pads may be electrically driven by the backplane circuit and other driving electronics.

[0009] Various embodiments provide light emitting devices configured to generate highly efficient red, green, blue, and / or other color pixelated light from shorter wavelength excitation sources using photonically excited quantum dots in a vertical cavity structure. Micro-scale light emitting diodes (micro LEDs) in examples are less than 100 microns in length and width, e.g., 5-20 microns, and can be used in display devices. This new technology allows for the ultimate black level to be achieved by using individual LEDs at each pixel location in a display device. Additionally, each pixel can be configured to generate a single color of light. The backplane on which the individual LEDs are mounted may include a substrate (e.g., plastic, glass, semiconductor, etc.) with thin film transistor (TFT) structures, silicon CMOS, or other driver circuitry configured to apply voltage or current independently to each LED. For example, the backplane may include TFTs on a glass or plastic substrate, or bulk silicon transistors (e.g., transistors in CMOS configuration) on a bulk silicon substrate or on a silicon-on-insulator (SOI) substrate. It should be noted that although micro-LEDs are described in the following embodiments, other types of LEDs (e.g., nanowire or other nanostructured LEDs) or macro-LEDs having sizes (e.g., width and length) greater than 100 microns can be used in place of or in addition to micro-LEDs.

[0010] In some embodiments, the size of each micro LED may be smaller than the pitch of pixels used in a particular display device, such as a direct view display device or other display device. For example, a 300 ppi display may have pixels with a pitch of about 85 microns, while a typical micro LED for such a display may be about 20 microns wide. Micro LEDs that include indium doped GaN material (i.e., LEDs that emit colors that depend on the indium doping of GaN) may suffer from degradation in efficiency and uniformity as LED size decreases (e.g., sizes below 10 microns) due to the difficulties associated with indium doping of the GaN crystal structure. Thus, longer peak wavelength emitting III-nitride micro LEDs (e.g., red LEDs) that utilize higher indium content in the active region may have poor efficiency and uniformity due to degraded indium doping.

[0011] Some of the embodiments of the present disclosure include photonic emitters based on LEDs having an undoped GaN active region (e.g., a micro-LED having a GaN light-emitting active layer) or a low indium-doped InGaN active region (e.g., a micro-LED having a low indium content InGaN light-emitting active layer) coupled with a photonically excited color conversion material. Such LEDs may be ultraviolet (UV)-emitting or blue light-emitting micro-LEDs having a peak emission wavelength in the ultraviolet (UV)-emitting or blue light spectral region (e.g., 370-460 nm, e.g., 390-420 nm, e.g., 400-410 nm). As used herein, the blue light spectral region includes the colors blue and violet as perceived by a human observer.

[0012] In some embodiments, the color conversion material may include quantum dots. The quantum dots may be configured to absorb photons generated by the GaN emitter and generate light of various colors depending on the properties of the quantum dots (e.g., their size and material composition). Such a structure may avoid problems associated with indium doping of small GaN structures.

[0013] In the size range appropriate for augmented reality (AR) displays (e.g., smart glasses) and other applications (i.e., sizes below 10 microns), the use of undoped or low indium-doped GaN LED active regions and photo-pumped quantum dots to produce a variety of colors can provide display devices with better uniformity across an array of micro-LEDs. Such arrays may also exhibit higher efficiency than systems with colored LEDs based on relatively highly indium-doped GaN (e.g., red LEDs with more indium than blue LEDs). Improved efficiency and uniformity can be achieved because quantum dots can be manufactured with a high degree of uniformity in size and material composition. These uniform quantum dots have correspondingly uniform (i.e., narrow spectral linewidth) emission characteristics.

[0014] Extraction of light emitted by micro-LEDs can become increasingly challenging as pixel pitch and micro-LED size become smaller. In the disclosed embodiments, light extraction of quantum dot-generated photons (e.g., along a particular direction) is improved while maintaining high efficiency by avoiding loss of photons to absorbing surfaces. The disclosed system can also prevent or reduce excitation photons from escaping the device, thereby ensuring the purity of the color emitted by a given micro-LED. This can be achieved by forming reflective optical cavity walls that include a light extraction material layer, microlenses, and / or distributed Bragg reflectors (DBRs).

[0015] 1A is a vertical cross-sectional view of an intermediate structure 100a that may be used to form a light-emitting device array, according to various embodiments. The intermediate structure 100a may include a plurality of micro LEDs 102 formed on a substrate 104. As discussed above, the micro LEDs 102 may include micro LEDs having peak emission wavelengths in the UV-emitting or blue light spectral region (e.g., UV or blue-emitting micro LEDs, also referred to as UV or blue LEDs). Such LEDs may include an undoped GaN active region configured to emit ultraviolet (UV) photons and / or photons in the blue spectral region.

[0016] In an embodiment, the micro LED 102 may have at least one electrode 103 located on the top of the LED and facing away from the substrate 104. The electrode 103 may consist of an anode electrode or a cathode electrode. In an embodiment, the micro LED 102 may consist of a vertical LED with a second electrode (not shown for clarity) located between the substrate 104 and the bottom surface of the micro LED 102. In another embodiment, the micro LED may include a horizontal LED with both electrodes located on the same side of the LED (e.g., the top or bottom side of the LED).

[0017] The substrate 104 may be a backplane having electrical circuitry (e.g., TFT circuitry and / or CMOS circuitry) configured to provide voltage and current to the micro-LEDs 102 via electrodes (including the electrodes 103) and thereby control light emission by the micro-LEDs 102. The backplane may be an active matrix or passive matrix backplane substrate for driving LEDs. As used herein, "backplane substrate" refers to any substrate configured to have multiple elements attached thereto. In an embodiment, the backplane may include a substrate including silicon, glass, plastic, and / or other materials that can provide structural support to at least the elements attached thereto. In an embodiment, the backplane substrate may be a passive backplane substrate in which a metal interconnect structure (not shown) including metallization lines is present, for example in a cross-lattice pattern, and there is no dedicated active element (e.g., TFT) for each LED. 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 may further include dedicated active elements (e.g., CMOS transistors or TFTs) for each LED at one or more intersections of the cross-grid of conductive lines.

[0018] 1B is a vertical cross-sectional view of a further intermediate structure 100b that may be used to form a light-emitting device array, according to various embodiments. The intermediate structure 100b includes a plurality of optical cavities 106 formed over the micro LEDs 102. Each optical cavity may be bounded by a cavity wall 108. The optical cavities 106 may be formed using a reflective material having mechanical properties suitable for forming a high aspect ratio cavity (e.g., diameter less than 5 microns, such as 1-2 microns, height greater than 10 microns, such as 20-30 microns) with relatively thin sidewalls 108. The cavity walls 108 may have a thickness less than 10 microns, such as 0.5-5 microns, including 1-2 microns. The cavity walls 108 form an insulating matrix.

[0019] The matrix material may be selected to be compatible with both thermal evaporation process steps and solvent-based fluid deposition and evaporation. One such matrix material is alumina, but silica, titania, or other insulating metal oxide materials may also be used. A variety of materials commonly used in the manufacture of microelectromechanical (MEMS) devices can be used to form optical cavities 106 bounded by cavity walls 108 made of an electrically insulating material (e.g., alumina). Such materials have a relatively high refractive index and are suitable for forming structures with high aspect ratios. A layer of such matrix material (not shown in FIG. 1B) can be grown or deposited on an array of micro-LEDs 102 disposed on a substrate 104, and techniques such as etching or other microfabrication approaches can be used to create optical cavities 106 in the material. FIG. 2A is a top perspective view of a matrix 200a having multiple cylindrical optical cavities 106 bounded by cavity walls 108. FIG. 2B is a top perspective view of a matrix 200 b having a plurality of hexagonal optical cavities 106 bounded by cavity walls 108 .

[0020] In an embodiment, a voltage can be applied to the anode or cathode electrodes 103 of the micro-LEDs 102, thereby forming one side of the etching bias. For example, if the matrix 200a or 200b (i.e., the cavity walls 108) comprises alumina, porous alumina may be formed by anodization. In this embodiment, an aluminum metal layer can be deposited on the micro-LEDs 102 and then electrochemically anodized to form a porous anodic alumina matrix having optical cavities (i.e., pores) 106 bounded by the anodized alumina cavity walls 108. The substrate 104 containing the aluminum layer is placed in an acid 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 micro-LEDs 102 to form a porous anodic alumina matrix containing optical cavities (i.e., pores) 106 bounded by the alumina walls 108. The optical cavities 106 may be arranged in a hexagonal array in an anodic alumina matrix.

[0021] FIG. 1C is a vertical cross-sectional view of a further intermediate structure 100c that may be used to form a light-emitting device array, according to various embodiments. The intermediate structure 100c may include a light extraction material layer 110 and a color conversion material (112a, 112b, 112c, 112d) formed in the optical cavity 106 above the array of micro LEDs 102. The light extraction material layer 110 may have a refractive index lower than that of the material forming the cavity wall 108. For example, the light extraction material layer 110 may have a refractive index less than 1.7, such as 1.3-1.5 for an alumina cavity wall 108. A low refractive index of the light extraction material layer 110 may cause excitation photons (i.e., photons generated by the micro LEDs 102) to be reflected from the cavity wall 108 rather than being absorbed by or transmitted through the cavity wall 108. Such reflection prevents loss of photons and increases the quantum efficiency of the device.

[0022] A variety of polymeric 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 can be configured to be as thick as possible to increase the probability that photons that do not reflect from the cavity wall 108 are absorbed (i.e., extinguished) and do not enter an adjacent cavity.

[0023] The light extraction material layer 110 can be deposited using a variety of techniques, including inkjet, vacuum, pressure, and / or gravity deposition. After deposition, the polymer may be crosslinked, for example, by exposure to ultraviolet (UV) radiation. In other embodiments, the solvent in which the polymer is dissolved can be driven off by evaporation, leaving behind residual crosslinked polymer as the light extraction material layer 110 in each cavity. In various embodiments, the light extraction material layer 110 can be formed in a variety of thicknesses and can be formed using a variety of techniques, including TiO 2 or SiO 2 The light extraction material layer 110 may or may not additionally include light scattering material such as nano- or microbeads. The light extraction material layer 110 partially fills the optical cavities 106 such that an empty cavity space remains above the light extraction material layer 110 of each cavity.

[0024] Color conversion materials (112a, 112b, 112c, 112d) may then be formed in the optical cavity 106 (see, e.g., FIG. 1B) and on the light extraction material layer 110 (see, e.g., FIG. 1C). The color conversion materials (112a, 112b, 112c, 112d) may include quantum dots corresponding to a variety of different colors. In this example, the color conversion materials (112a, 112b, 112c, 112d) may include 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, which are configured to convert UV excitation photons into photons having a first, second, third, and fourth color, respectively. The second and third colors may be composed of different peak wavelengths within the green spectral range. Alternatively, only three quantum dot colors may be used. The quantum dots may each comprise nanocrystals of 1-10 nm, e.g., 2-8 nm, of a compound semiconductor material, e.g., a III-V semiconductor material (e.g., indium phosphide, as described in U.S. Pat. No. 9,884,763 B1, which is incorporated herein by reference in its entirety), a II-VI semiconductor material (e.g., ZnSe, ZnS, ZnTe, CdS, CdSe, etc., core-shell quantum dots, as described in U.S. Patent Publication 2017 / 0250322 A1, which is incorporated herein by reference in its entirety), and / or a I-III-VI semiconductor material (e.g., AgInGaS / AgGaS core-shell quantum dots, as described in U.S. Pat. No. 10,927,294 B2, which is incorporated herein by reference in its entirety). The quantum dots can emit different colors of light (e.g., red, green, blue) depending on their diameter. Larger dots emit longer wavelengths of light and smaller dots emit shorter wavelengths of light. The quantum dots may be suspended in a material (e.g., a polymer such as polyimide) that has a different (e.g., higher) refractive index than the refractive index of the light extraction material 110. By way of example, the refractive index of the polyimide material may be between 1.6 and 1.75, e.g., about 1.7.

[0025] As described in more detail below (see, e.g., Figures 3A-4P), quantum dots corresponding to various colors can be selectively deposited in the respective cavities. For example, as described with reference to Figures 3A-3L below, 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 layer of protective material can be formed over the first quantum dot. This process can then be repeated to form a second cavity, a third cavity, etc., and introduce a second quantum dot, a third quantum dot, etc., into each respective cavity.

[0026] In other embodiments (see, for example, Figures 4A to 4P), photoresist may be deposited on all cavities except the first cavities. A first layer of quantum dots configured to generate a first color (e.g., red) may then be deposited in the first cavities corresponding to the subpixels having the first color. The polymer in which the first quantum dots are suspended may then be crosslinked by evaporation or exposure to UV light. The process may then be repeated for the other optical cavities, depositing quantum dots configured to generate other colors of light (e.g., green and blue), respectively.

[0027] An optional organic planarization layer may be formed over the color conversion material. The color conversion material and optional organic planarization layer may partially fill the optical cavity 106.

[0028] 1D is a vertical cross-sectional view of a light-emitting element array 100d, according to various embodiments. As shown, the array 100d may include a color selector 114 formed in and / or on the optical cavity 106. The color selector 114 may include a color filter array and / or a distributed Bragg reflector. In an 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 above material.

[0029] The color conversion materials (112a, 112b, 112c, 112d) may be configured to absorb and convert excitation photons 118 to emitted converted photons (e.g., visible light such as red, green, or blue) 120. In some embodiments, the color conversion materials (112a, 112b, 112c, 112d) may not have a sufficient thickness and / or density to completely convert all excitation photons 118 to converted photons 120. In this manner, the color selector 114 formed on the color conversion materials (112a, 112b, 112c, 112d) absorbs and / or reflects all or a portion of the excitation photons 118 not converted by the color conversion materials (112a, 112b, 112c, 112d) without absorbing and / or reflecting the converted photons 120 emitted by the color conversion materials.

[0030] Each micro LED 102 may be configured to emit excitation photons 118 within a common or target wavelength range. For example, a GaN-based micro LED 102 may emit excitation photons 118 having a wavelength of about 400-410 nm, such as about 405 nm (i.e., in the blue or near ultraviolet portion of the electromagnetic spectrum). The micro LEDs 102 may exhibit high uniformity and exhibit high efficiency. However, slight variations in wavelength of such micro LEDs 102 may not be easily visible. Furthermore, leakage of excitation photons 118 through the color conversion material (112a, 112b, 112c, 112d) may minimize degradation of color purity of the converted photons 120.

[0031] In an embodiment, the color selector 114 includes a color filter array including organic dyes embedded in an organic polymer. The dyes may be configured to absorb the ultraviolet light of the excitation photons 118 but not the blue, green, or red light of the conversion photons. Optionally, different dyes may be provided on each colored subpixel (e.g., red, green, and blue subpixels). For example, a first dye filter material configured to transmit primarily red light may be provided on the red subpixels, a second dye filter material configured to transmit primarily green light may be provided on the green subpixels, and a third dye filter material configured to transmit primarily blue light may be provided on the blue subpixels. The color filters may be formed using further photolithography steps. In various embodiments, a thin film encapsulation (TFE) layer or layer stack may then be applied over the color filter material to provide protection against air or moisture ingress to the quantum dot layer of the color conversion material. In an embodiment, the TFE may include a three-layer stack of two silicon nitride layers separated by a polymer layer.

[0032] In an alternative embodiment, the color selector 114 may include a distributed Bragg reflector (DBR) formed on the color conversion material (112a, 112b, 112c, 112d). The DBR may be configured to reflect excitation photons 118 transmitted through the color conversion material back into the cavity 106 as reflected photons 122 (e.g., ultraviolet or deep blue photons) and transmit converted photons 120 from the cavity 106. The DBR may be formed as an alternating multi-layer stack of materials (not shown) having different refractive indices. For example, the DBR may be formed of TiO 2 (n=2.5) and SiO 2 (n=1.5) and N layers of alternating layers of 1000 nm to 1500 nm, where N is equal to or greater than 2. In other embodiments, a variety of other materials having respective refractive indices may be used to create the DBR.

[0033] DBR is TiO 2 and SiO 2In an embodiment including N=2, the bandwidth may be 164 nm and the maximum reflectance R may be 84% at a central wavelength of 405 nm. In an embodiment where the DBR stack includes a larger number of layers (i.e., N>2), the reflectance may be increased. Therefore, the probability that a UV excitation photon 118 passes through the DBR may be decreased. UV reflected photons 122 that are reflected from the DBR back to the optical cavity 106 may circulate through the color conversion material (112a, 112b, 112c, 112d), thereby also increasing the probability that they are converted to a converted photon 120 having a desired wavelength (e.g., green, blue, or red). In this way, any UV reflected photon 122 that is not initially absorbed by the color conversion material (112a, 112b, 112c, 112d) may eventually be absorbed and converted to a converted photon 120 having a desired emission wavelength. This process, sometimes referred to as "photon recycling," may increase the quantum efficiency of the device.

[0034] If the micro-LED 102 includes a short-wavelength blue-emitting LED, the DBR 114 blocks the short-wavelength blue light (i.e., excitation photons 118) of the micro-LED 102 but allows the long-wavelength converted photons 120 emitted from the blue quantum dots of the color conversion material to pass through. Alternatively, the DBR 114 can be omitted on the sub-pixels that emit blue light.

[0035] The DBR can be formed by deposition (e.g., evaporation) of a multi-layer stack (not shown) over every subpixel. In this way, the DBR provides additional protection against moisture and oxygen ingress to the quantum dot layer. Higher values ​​of N further improve the reflectivity of the DBR and its protection from moisture and oxygen, improving the performance and durability of the overall system.

[0036] In additional various embodiments, other materials may be used for various components of the device. For example, the DBR may include a wide range of materials, each with its own refractive index, such as nitrides (TiN, AlN, TiN, etc.), polysilicon, etc. Some embodiments may include multiple layers of quantum dots, multiple DBR structures, etc. The light extraction material layer 110 described above may be omitted in some embodiments, or multiple light extraction material layers 110 may be used. By using a more effective DBR 114, the layer thickness and density of the color conversion material (112a, 112b, 112c, 112d) may be reduced. In further embodiments, the optical cavity 106 may be formed in a variety of ways. For example, as described in more detail below, the optical cavity 106 may be formed in a separate matrix layer that is attached to the array of micro-LEDs 102 after the optical cavity 106 is formed. In further embodiments, a light collimating element may be included to mitigate performance degradation due to lateral photon propagation.

[0037] FIG. 1E is a vertical cross-sectional view of a further light-emitting element array 100e according to various embodiments. As shown therein, the light-emitting element array 100e includes a microlens 124 formed over the optical cavity 106. Each microlens 124 can help improve light extraction from each micro LED structure, thereby improving the efficiency of the array 100e. In general, extraction of light emitted by a micro LED can become increasingly difficult as pixel pitch and micro LED size become smaller. In this regard, the color conversion material (112a, 112b, 112c, 112d) may be selected to be thick enough to convert all of the excitation photons 118 into converted photons 120, each having a particular color. The thickness of the color conversion material (112a, 112b, 112c, 112d) may be very large compared to the lateral dimensions of the subpixels. In such a structure, photons may travel diffusively rather than ballistically from the micro LED subpixels. These diffusively moving photons can spread to adjacent sub-pixels and cause optical crosstalk.

[0038] Embodiments of the present disclosure improve light extraction of photons (e.g., along a particular direction) generated by the quantum dots while maintaining high efficiency by avoiding loss of photons to absorbing surfaces. As described above, this may be achieved by forming a matrix structure that includes reflective cavity walls 108, including a light extraction material layer 110, and / or including a color selector 114, such as a DBR.

[0039] The use of quantum dots as color conversion materials (112a, 112b, 112c, 112d) for micro LED displays may involve deposition and patterning of high density quantum dot layers with very small feature sizes. Subpixels with aspect ratios greater than 1:1 may be used to allow sufficient absorption of excitation photons 118 (see, e.g., FIG. 1D and FIG. 1E) in the quantum dot layer. Such subpixels may also be separated by cavity walls 108 formed of an opaque matrix material to prevent color crosstalk in the display (i.e., photons from one micro LED propagating to an adjacent subpixel).

[0040] High concentrations of quantum dots used as color conversion materials (112a, 112b, 112c, 112d) can pose additional challenges to the fabrication of high-resolution structures. Quantum dots strongly absorb UV light, which can reduce the activity of photoinitiators and photoacid generators commonly used in photoresists. Thus, the presence of quantum dots may require modifications to traditional fabrication materials and methods. Thus, patterning tall and thin structures can become more difficult when using high loadings of quantum dots. In embodiments of the present disclosure, this challenge is addressed by forming cavities as etched vias in the matrix material, as described in more detail below with reference to Figures 3A to 4P.

[0041] Various embodiments include a matrix, such as matrix 200a or 200b, which may allow better light extraction from each subpixel and mitigate photonic color crosstalk. Using the matrix as a template to sequentially open vias corresponding to different color subpixels allows for deposition and curing of quantum dot inks without relying on high-resolution photopatternable resin formulations. Various embodiments described below include opening vias in a matrix layer corresponding to one color, filling with quantum dot ink, curing and sealing, and then repeating the same process for a second color, a third color, and so on.

[0042] 3A-3L are vertical cross-sectional views of intermediate structures that may be used to form a light-emitting device array, according to various embodiments. As shown in FIG. 3A, a continuous matrix layer 304L may be deposited on a support 302. In some embodiments, the continuous matrix layer 304L may have a thickness of about 10-30 microns. The matrix layer 304L may include an insulating material, such as silica, alumina, titania, etc., to form the optical cavity walls 108 described above with respect to FIG. 1B. Alternatively, the matrix layer 304L may include a metal, such as aluminum, that is anodized to form anodic alumina. In another alternative embodiment, the matrix layer 304L may be a reflective metal, such as aluminum, that is not converted to a metal oxide. In this alternative embodiment, the matrix layer 304L is formed over the micro LEDs 102 in a manner that avoids electrical shorting of corresponding electrodes of adjacent micro LEDs 102 to each other.

[0043] 1A, which supports the micro-LEDs 102. In alternative embodiments, the support 302 may comprise a separate substrate, such as a transparent glass or polymer substrate, which is subsequently mounted on the backplane 104 that supports the micro-LEDs 102.

[0044] 3B, a patterned mask material 306 may be formed on the continuous matrix layer 304L. In one embodiment, the patterned mask material 306 may be a photoresist and may be patterned using photolithography techniques.

[0045] A continuous matrix layer 304L (see, e.g., FIG. 3A) may be etched to form an etched matrix layer 304 including a first via 308a. In an exemplary embodiment, the continuous aluminum matrix layer 304L may be etched using a BC13 dry etching process. The first via 308a may correspond to the optical cavity 106 for 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 mask material 306 may be removed.

[0046] As shown in FIG. 3C, the patterned mask material 306 (see, e.g., FIG. 3B) may be removed and replaced with a superhydrophobic (i.e., non-stick) coating 310. The coating 310 may include a fluorinated silane coating, such as inorganic nanoparticles (e.g., silica nanoparticles) functionalized with fluoroalkylsilane groups. As shown in FIG. 3D, a quantum dot ink having a plurality of first quantum dots 112a may then be deposited by spin coating, doctor blading, inkjet printing, or other methods to fill the first vias 308a. The fluorinated coating 310 may prevent a majority of the quantum dots from adhering to the top surface of the structure. The quantum dot ink may then be cured by either UV exposure or heating. The fluorinated coating 310 and excess quantum dots may then be washed away, as shown in FIG. 3E.

[0047] A protective layer 314 may then be formed over the first quantum dots 112a, as shown in FIG. 3F. For example, the protective layer 314 may be a layer of alumina, which may be deposited by atomic layer deposition (ALD). In an exemplary embodiment, the protective layer 314 may have a thickness of about 3-10 nm, such as about 5 nm. Other embodiments may include other thicknesses, other materials, and other deposition methods for the die protective layer 314.

[0048] The above-described process (see, e.g., FIGS. 3A-3F) may then be repeated to deposit and cure quantum dot inks for other colors. For example, a patterned mask material 306 may be formed over the intermediate structure of FIG. 3F, and an etching process may be used to form second vias 308b through the protective layer 314, as shown in FIG. 3G. The patterned mask material 306 may be removed and replaced with the superhydrophobic (i.e., non-sticky) fluorinated coating 310 described above, as shown in FIG. 3H. A quantum dot ink having a plurality of second quantum dots 112b (i.e., dots of a different color than the dots 112a) may then be deposited by spin coating, doctor blading, inkjet printing, or other methods to fill the second vias 308b, as shown in FIG. 3I. The fluorinated coating 310 and excess quantum dots may then be washed away, as shown in FIG. 3I. A second protective layer having a first portion 314a and a second portion 314b may then be formed over the second quantum dots 112b, as shown in Figure 3K. The first portion 314a may be formed over the existing first protective layer 314, while the second portion 314b may be formed over the second vias 308b filled with the second quantum dots 112b.

[0049] Similarly, as shown in Figure 3L, the process may continue to form a third via 308c, which may be filled with a third quantum dot ink including a third quantum dot 112c (not shown in this figure). In various embodiments, the process may continue to form additional vias that may be filled with quantum dots corresponding to additional respective colors.

[0050] If the support 302 comprises a transparent substrate, the support 302 supporting the completed matrix including quantum dots is mounted on top of a backplane 104 supporting the micro LEDs 102. If the support 302 comprises a backplane 104 supporting the micro LEDs 102, the etched matrix layer 304 includes cavity walls 108 that surround an optical cavity 106 filled with quantum dots (112a, 112b, etc.).

[0051] 4A-4P are vertical cross-sectional views of intermediate structures that may be used to form light-emitting device arrays, according to various embodiments. The process of FIG. 4A-4P includes providing a matrix layer on a support, depositing a planar positive photoresist layer, and selectively exposing and removing the photoresist to sequentially open vias. The process of FIG. 4A-4P relies on the removal of the photoresist to form optical cavities. Thus, in certain embodiments, the second process flow (i.e., described below with reference to FIG. 4A-4P) may be more versatile, less expensive, and safer.

[0052] As shown in FIG. 4A, the first intermediate structure may include a continuous matrix layer 108L formed on the support 302 described above. The matrix layer 108L may include an insulating layer, such as alumina, silica, titania, 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 blanket layer of photoresist (not shown) may be formed on the continuous matrix layer 108L to form the patterned photoresist 406 using photolithography techniques.

[0053] 4B, the patterned photoresist 406 may be used as a mask layer to etch the continuous matrix layer 108L to form a cavity (e.g., an optical cavity) 106 bounded by via or cavity walls 108. The patterned photoresist 406 may then be removed by ashing or dissolving with a solvent.

[0054] In an alternative embodiment, the continuous matrix layer 108L may not be etched but may be anodized to form the cavity walls 108. As described above, if the continuous matrix layer 108L comprises aluminum, it may be anodized in acid as described above to form a porous anodic alumina layer that includes the cavity walls 108 surrounding the optical cavities (i.e., pores) 106.

[0055] 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 may then be deposited over the intermediate structure of Figure 4B and within the optical cavity 106. Each photoresist portion fills a respective optical cavity 106.

[0056] As shown in Figure 4D, an optional patterned mask 410 may be used in conjunction with a UV radiation source (e.g., a UV light-emitting lamp) 412 to selectively expose the first photoresist portion 408a of the positive photoresist to UV radiation 414 through the mask 410. Exposure of the first photoresist portion 408a of the positive photoresist makes the first photoresist portion 408a soluble in a photoresist developer, which can be used to remove the first photoresist portion 408a of the positive photoresist. The second and third photoresist portions are not exposed to UV radiation.

[0057] Alternatively, if the support 302 includes a backplane 104 supporting the UV-emitting micro-LEDs 102, the micro-LEDs 102 located under the first photoresist portion 408a may be activated such that the first photoresist portion 408a is irradiated with UV radiation from underneath and becomes soluble in a developer. In this alternative embodiment, the mask 410 and the radiation source 412 may be omitted. The micro-LEDs 102 located under the second and third photoresist portions 408b, 408c are not activated.

[0058] As shown in FIG. 4E, the first via 416a may be created by removing the first photoresist portion 408a without removing the other photoresist portions 408b, 408c by immersing the structure in a photoresist developer bath or by spraying a developer on a positive photoresist.

[0059] As shown in FIG. 4F, the first quantum dot ink 418a may then be introduced into the first via 416a, so that the first via 416a may be filled with a uniform layer of the first quantum dots 112a. The polymer in which the first quantum dots 112a are suspended may then be cured thermally or by exposure to UV radiation. For example, FIG. 4G shows exposure to UV radiation using a mask 410 patterned on the first quantum dots 112a and a UV radiation source 412. Alternatively, a UV-emitting micro LED 102 beneath the first quantum dots 112a may be activated to irradiate the first quantum dots 112a with UV radiation.

[0060] The above-described process illustrated in FIGS. 4C-4G may then be repeated to form second quantum dots 112b within the second optical cavity 106. In this regard, as illustrated in FIG. 4H, the second photoresist portion 408b of the positive photoresist illustrated in FIG. 4C may be exposed to UV radiation from a UV radiation source 412 or UV radiation from the micro-LED 102. The second photoresist portion 408b of the positive photoresist may then be removed with a photoresist developer to form a second via 416b, as illustrated in FIG. 4I. A second quantum dot ink 418b may then be introduced into the second via 416b to form a uniform layer of second quantum dots 112b, as illustrated in FIG. 4J. The uniform layer of second quantum dots 112b may then be cured by exposure to UV radiation from a UV radiation source 412 or UV radiation from the micro-LED 102, as illustrated in FIG. 4K.

[0061] The above-described process illustrated in FIGS. 4C-4G may then be repeated to form the third quantum dots 112c within the third optical cavity 106. In this regard, as illustrated in FIG. 4L, the third photoresist portion 408c of the positive photoresist may be exposed to UV radiation from the UV radiation source 412 or UV radiation from the micro LED 102. The third photoresist portion 408c of the positive photoresist may then be removed with a photoresist developer to form the third via 416c, as illustrated in FIG. 4M. The third quantum dot ink 418c may then be introduced into the third via 416c to form a uniform layer of the third quantum dots 112c, as illustrated in FIG. 4N. The uniform layer of the third quantum dots 112c may then be cured thermally or by exposure to UV radiation from the UV radiation source 412 or UV radiation from the micro LED 102, as illustrated in FIG. 4O.

[0062] Finally, a protective layer 314 may be formed over the first quantum dot uniform layer 112a, the second quantum dot uniform layer 112b, the third quantum dot uniform layer 112c, and the cavity walls 108, as shown in FIG. 4P. As mentioned above, the protective layer 314 may be an alumina layer deposited by ALD. As mentioned above, other materials and deposition processes may be used to deposit the protective layer 314 and / or the color selector 114 (e.g., DBR).

[0063] In the above-described embodiments, the shape of the subpixels in the light-emitting element array may be determined by the shape of the cavities / vias. In this way, the patterning requirements for the quantum dot inks (418a, 418b, 418c) can be significantly relaxed compared to the requirements for embodiments that do not rely on a matrix template. In some embodiments, a UV-curable quantum dot ink may be used to confine the quantum dots to the target subpixels. In other embodiments, a thermally curable ink may be used. The use of a UV-curable or thermally curable quantum dot ink increases the choice of chemistries that can be used in forming the (quantum dot-based) color conversion material (112a, 112b, 112c, 112d).

[0064] Various embodiments may include solvent-based or solventless quantum dot inks. By using thermal curing for the quantum dot inks of each subpixel, photocurable acrylates / epoxies for ink formulation can be omitted. In further embodiments, quantum dot inks may be formed using inorganic ligand and matrix materials (e.g., metal chalcogenides and metal oxides), which provide alternative advantages such as high temperature stability.

[0065] 5A-5G are vertical cross-sectional views of further intermediate structures that may be used to form a light-emitting device array, according to various embodiments. As shown in FIG. 5A, a plurality of micro LEDs 102 may be formed on a substrate 104. The substrate 104 may be a backplane having electrical circuitry (e.g., CMOS circuitry or TFT circuitry) configured to provide voltage to the micro LEDs 102 and thereby control light emission by the micro LEDs 102. As described above, the micro LEDs 102 may include blue or ultraviolet light-emitting LEDs. The intermediate structure of FIG. 5A may include a common cathode 502 for the plurality of micro LEDs 102 formed of a transparent conductive oxide (e.g., indium tin oxide) and an anode 503 for each micro LED 102 separately electrically connected to a respective backplane circuit (not shown for clarity). Thus, the plurality of micro LEDs 102 are shorted at their cathode (e.g., n-type) sides but are separately activated by the backplane circuitry at their anode (e.g., p-type) sides. The common cathode 502 is also connected to the backplane circuitry outside the area of ​​the micro-LEDs 102.

[0066] In some embodiments, the micro LEDs 102 may include vertical LEDs with cathode and anode electrodes (502, 503) located on opposite sides of the LED. In some embodiments, the micro LEDs 102 may have a reverse taper. In other words, the micro LEDs 102 may be wider on the bottom side facing the anode 503 and backplane 104 than on the top side facing the common cathode 502.

[0067] As shown in FIG. 5B, a first color conversion material (e.g., first color quantum dots) 504a may be formed on the first plurality of micro LEDs 102. The first color conversion material 504a may be formed by an inkjet process that may be used to directly print only the first quantum dot ink on the first portion of the common cathode 502 on each micro LED 102 of the first color subpixel. Alternatively, a continuous quantum dot layer may be deposited directly on the common cathode, and then photolithography and patterning may be performed to leave the first color quantum dots 504a only on each micro LED 102 of the first color subpixel.

[0068] As shown in FIG. 5C, a second color conversion material 504b may be formed on a second plurality of micro LEDs 102. The second color conversion material 504b may be formed by an inkjet process that may be used to directly print a second quantum dot ink on the second portion of the common cathode 502 on each micro LED 102, or by depositing a continuous quantum dot layer and then photolithographic patterning. The color conversion material may be omitted on the blue-emitting micro LEDs 102. Alternatively, a blue color conversion material may be formed on the ultraviolet-emitting micro LEDs 102. Finally, a respective color selector 114 may be formed on the first color conversion material 504a and the second color conversion material 504b. For example, the color selector 114 may be a DBR as described above. If desired, an encapsulation layer, such as an alumina layer, may be formed on the color selector 114.

[0069] Alternatively, the intermediate structures of Figures 5B and 5C can be formed using processes similar to those described above with reference to Figures 4A-4P. In this regard, a patterned photoresist (not shown) may be formed on the common cathode 502 and used as a mask material for the deposition of the first color conversion material 504a. In this regard, the mask material may include openings corresponding to where the first color conversion material 504a is to be deposited. After the first color conversion material 504a is deposited and cured, the photoresist may be patterned to form openings corresponding to where the second color conversion material 504b is to be deposited.

[0070] In further embodiments, the intermediate structure of Figures 5D and 5E may 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 may then be deposited as shown in Figures 5D and 5E. The etch stop layer 508 may include silicon oxide or other similar etch stop material. The presence of the etch stop layer 508 may protect the transparent conductive oxide that forms the common cathode 502 during the process in which the die photoresist is etched.

[0071] The process of forming the additional alternative intermediate structures of Figures 5F and 5G may be similar to the process used to form the intermediate structures of Figures 5D and 5E from the die intermediate structure of Figure 5A. In this regard, each of the intermediate structures of Figures 5F and 5G may 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 may further include an optical cavity 106 bounded by a cavity wall 108. If the micro LED 102 comprises a blue LED, the optical cavity 106 above the blue subpixel may be left unfilled. In this manner, the intermediate structures of Figures 5F and 5G may be similar to the embodiments of Figures 1B-1E, 3L, and 4B-4P.

[0072] The foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the disclosed embodiments. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

Claims

1. 1. A method of forming a light emitting device array, comprising: 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 material layer corresponding to a first color; forming a second via in the matrix material; depositing a second plurality of quantum dots in the second vias to form a second portion of the color conversion material 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 the color conversion material layer corresponding to a third color; Including, the first plurality of quantum dots is disposed on a first light emitting diode, the second plurality of quantum dots is disposed on a second light emitting diode, and the third plurality of quantum dots is disposed on a third light emitting diode. A method for forming a light emitting device array.

2. forming a first protective layer over the first plurality of quantum dots before forming the second vias in the matrix material; and forming a second protective layer over the second plurality of quantum dots before forming the third via in the matrix material. The method of claim 1.

3. forming a first positive photoresist portion in the first via, a second positive photoresist portion in the second via, and a third positive photoresist portion in the third via during a same positive photoresist deposition step, wherein forming the first, second, and third vias in the matrix material occurs during the same via formation process. selectively exposing and removing the first positive photoresist portion covering the first via before depositing the first plurality of quantum dots in the first via; selectively exposing and removing the second positive photoresist portion covering the second via 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; and selectively exposing and removing the third positive photoresist portion covering the third via 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; further comprising: The method of claim 1.

4. the first, second, and third light emitting diodes are disposed on a backplane; the matrix material is formed over the first, second, and third light emitting diodes before forming the first, second, and third vias 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; selectively exposing the third positive photoresist portion includes activating the third light emitting diode to expose the third positive photoresist portion; The method of claim 3.

5. the first, second, and third light emitting diodes are disposed on a backplane; the matrix material is formed over the first, second, and third light emitting diodes before forming the first, second, and third vias in the matrix material; the matrix material comprises a metal or metal oxide layer; The method according to claim 1 or 2.

6. the matrix material is formed as an aluminum layer over the first, second, and third light emitting diodes; forming the first, second, and third vias in the matrix material includes anodizing the aluminum layer by applying a voltage to electrodes of the first, second, and third light emitting diodes in an acid bath to form an alumina matrix material; The method of claim 5.

7. forming a first color selector on the first plurality of quantum dots within the first via; forming a second color selector on the second plurality of quantum dots in the second via; and forming a third color selector on the third plurality of quantum dots in the third via; further comprising: The method according to claim 1 or 2.

8. the first, second, and third color selectors comprise organic dye color filters embedded in an organic polymer; The method of claim 7.

9. the first, second, and third color selectors include distributed Bragg reflectors; The method of claim 7.

10. further comprising forming a light extraction material over the first, second, and third light emitting diodes before forming the first, second, and third color selectors; the light extraction material has a first refractive index that is less than a second refractive index of the matrix material; The method according to claim 1 or 2.

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