Light emitting diode with enhanced light conversion efficiency

Abstract

Embodiments of the present technology include a pixel structure. The pixel structure includes a light emitting diode structure to generate ultraviolet light. The pixel structure further includes a photoluminescent region comprising a photoluminescent material. The pixel structure additionally includes a first bandpass filter located between the light emitting diode structure and the photoluminescent region, wherein the first bandpass filter is operable to transmit more than 50% of light having a wavelength of less than or about 400 nm. The pixel structure further includes a second bandpass filter located on an opposite side of the photoluminescent region from the first bandpass filter, wherein the second bandpass filter is operable to transmit more than 50% of light having a wavelength greater than 400 nm.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] Cross-reference to related applications: This application claims the benefit and priority of U.S. Provisional Application No. 63 / 406,937, filed on September 15, 2023, entitled "Light Emitting Diode with Enhanced Light Conversion Efficiency", the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present technology relates to displays having a pixel structure having a light emitting diode (LED) structure combined with a photoluminescent region containing a photoluminescent material. Exemplary photoluminescent materials include quantum dots. Background Art

[0004] High-resolution light-emitting diode (LED) displays can include millions of micron-sized pixels arranged to form a viewing screen. Conventional LED displays produce color images by filtering white light from an LED light source into red, green, and blue pixels that emit at different intensities across the viewing screen. Other LED displays excite organic or inorganic compounds so that they emit light of a specific color, such as red, green, or blue, depending on the pixel. These LED displays typically require fewer filters to block light of unwanted colors and can produce a more accurate color gamut. However, many photoluminescent materials have relatively low conversion efficiencies between excitation light and target visible light. They can also emit and scatter light in all directions. These characteristics of luminescent compounds can reduce the brightness of displayed images.

[0005] Therefore, there is a need for pixel designs to produce brighter images for display devices including stimulable luminescent materials. These and other needs are addressed by the present technology. Summary of the invention

[0006] Embodiments of the present technology include a pixel structure. The pixel structure includes a light emitting diode structure to generate ultraviolet light. The pixel structure further includes a photoluminescent region containing a photoluminescent material. The pixel structure additionally includes a first bandpass filter located between the light emitting diode structure and the photoluminescent region, wherein the first bandpass filter is operable to transmit ultraviolet light. The pixel structure also additionally includes a second bandpass filter located on a side of the photoluminescent region opposite to the first bandpass filter, wherein the second bandpass filter is operable to transmit visible light.

[0007] In additional embodiments, the photoluminescent region of the pixel structure may include a first side adjacent to the first bandpass filter and a second side adjacent to the second bandpass filter, wherein the second side of the photoluminescent region is wider than the first side. In further embodiments, the photoluminescent region may further include a first sidewall in contact with the first bandpass filter, wherein the first sidewall and the first bandpass filter are characterized by an angle of inclination greater than 90°. In still further embodiments, the pixel structure may include a microlens structure, wherein the second bandpass filter is located between the microlens structure and the photoluminescent region. In other additional embodiments, the pixel structure may include a protective region located between the light-emitting diode structure and the first bandpass filter. In more embodiments, the photoluminescent material in the photoluminescent region of the pixel structure may include a quantum dot material operable to absorb light of a first wavelength from the light-emitting diode structure and emit light of a second wavelength longer than the first wavelength. In still more embodiments, the photoluminescent region is characterized by a depth between the first side and the second side of greater than or about 1 μm. In still further embodiments, the first side of the photoluminescent region is characterized by a width across the photoluminescent region of less than or about 30 μm.

[0008] Additional embodiments of the present technology include additional pixel structures. The pixel structure includes a light emitting diode structure operable to generate ultraviolet light and a photoluminescent region located above the light emitting diode structure. The photoluminescent region is characterized by a depth between a first side and a second side of the photoluminescent region, wherein the first side of the photoluminescent region is shorter than the second side.

[0009] In a further embodiment, the photoluminescent region of the pixel structure includes a third side, the third side including a sidewall region between the first side and the second side of the photoluminescent region, wherein the tilt angle between the first side and the third side is greater than 90 degrees. In an even further embodiment, the first side of the photoluminescent region is characterized by a width of less than or about 4 μm. In an additional embodiment, the first side of the photoluminescent region is adjacent to a short bandpass filter located between the light-emitting diode structure and the photoluminescent region, wherein the short bandpass filter is operable to transmit ultraviolet light, and wherein the second side of the photoluminescent region is adjacent to a long bandpass filter located on an opposite side of the photoluminescent region, wherein the long bandpass filter is operable to transmit visible light. In an additional embodiment, the photoluminescent region of the pixel structure may include a photoluminescent material, the photoluminescent material including a quantum dot material, the quantum dot material being operable to absorb light of a first wavelength from the light-emitting diode structure and emit light of a second wavelength longer than the first wavelength.

[0010] A further embodiment of the present technology includes a display component. The display component has a plurality of pixel structures, wherein each of the pixel structures includes a light-emitting diode structure operable to generate ultraviolet light and a photoluminescent region containing a photoluminescent material. The pixel structure further includes a first bandpass filter located between the light-emitting diode structure and the photoluminescent region, wherein the first bandpass filter is operable to transmit ultraviolet light. The pixel structure additionally includes a second bandpass filter located on an opposite side of the photoluminescent region from the first bandpass filter, wherein the second bandpass filter is operable to transmit visible light.

[0011] In further embodiments, the pixel structure further comprises a first side of the photoluminescent region adjacent to the first bandpass filter and a second side of the photoluminescent region adjacent to the second bandpass filter, wherein the second side is wider than the first side, and wherein the photoluminescent region further comprises a first sidewall in contact with the first bandpass filter, and the first sidewall and the first bandpass filter are characterized by an inclination angle greater than 90 degrees. In other further embodiments, the photoluminescent material in the photoluminescent region of the pixel structure comprises a quantum dot material, the quantum dot material being operable to absorb light of a first wavelength from the light emitting diode structure and emit light of a second wavelength shorter than the first wavelength, and the light emitting diode structure is a micro light emitting diode structure. In further embodiments, the display component is characterized by a pixel density of greater than or about 3000 pixels per inch (ppi). In still further embodiments, the display component is characterized by an optical density of greater than or about 1. In further embodiments, the display component is operable to be incorporated into an augmented reality display device.

[0012] The present technology provides many advantages over conventional designs for pixel structures and display components including the same. In many conventional designs, the pixel structure lacks a short bandpass filter between the UV-generating light-emitting diode structure and the bottom of the photoluminescent region, and lacks a long bandpass filter at the top of the photoluminescent region. Many conventional designs also have sidewalls formed at right angles (i.e., 90° tilt angles) to the top and bottom sides of the photoluminescent region. These design features result in a reduction in the proportion of visible light generated in the photoluminescent region that contributes to the display image. In an embodiment of the present technology, a short bandpass filter is positioned between the UV-generating light-emitting diode structure and the bottom of the photoluminescent region to reflect more visible light into the photoluminescent region and reflect out the display image. Further embodiments of the present technology include a long bandpass filter at the top of the photoluminescent region to reflect UV light back to the photoluminescent region while allowing visible light to pass through to the display image. Still further embodiments of the present technology widen the top side of the photoluminescent region through which visible light passes to form the display image relative to the bottom side of the photoluminescent region positioned adjacent to the light-emitting diode structure. Relative to a conventional photoluminescent region having the same width on the top and bottom sides, the widened top side of the photoluminescent region relative to the bottom side allows more visible light to pass through to the image. These and other embodiments and their numerous advantages and features are described in more detail in conjunction with the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A further understanding of the nature and advantages of the present invention may be realized by reference to the remainder of the specification and the drawings, wherein the same component symbols are used throughout the various drawings to refer to similar components. In some instances, a sub-symbol is associated with the component symbol and is followed by a dash to indicate one of multiple similar components. When a component symbol is referenced without specifying the existing sub-symbol, it is intended to refer to all such multiple similar components.

[0014] Figure 1 A flow chart showing selected operations of an exemplary method of fabricating a pixel structure in accordance with embodiments of the present technology.

[0015] Figure 2 A simplified cross-sectional view of an exemplary single pixel structure is shown in accordance with an embodiment of the present technology.

[0016] Figure 3 A simplified cross-sectional view of an exemplary RGB pixel structure is shown in accordance with an embodiment of the present technology.

[0017] FIG. 4A to FIG. 4B Graphs showing exemplary first and second bandpass filters according to embodiments of the present technology. DETAILED DESCRIPTION

[0018] Advances in the technology of high-resolution displays include the development of micro-light-emitting diodes (μLEDs) from inorganic semiconductor materials and the use of photoluminescent materials such as quantum dots in displays. μLEDs are made of multiple layers of semiconductor materials, such as indium gallium nitride (InGaN), that are arranged to emit light of a specific peak emission wavelength when excited by an applied electric field. Semiconductor manufacturing processes are used to produce μLEDs that are less than or about 50 μm in their longest dimension and are operable to emit red, green, or blue light. Quantum dots are nanometer-sized particles of inorganic material that are capable of emitting light of a specific color after being excited by higher energy light. The color of the emitted light can depend on one or more characteristics of the particles, including the size, shape, and composition of the particles, among other characteristics. For quantum dots made of inorganic semiconductor materials, the color of the light they emit depends on the energy gap between the conduction band and the valence band of the dot. When a quantum dot is excited, one or more electrons jump from the lower energy conduction band to the higher energy valence band. When the excited electrons fall back to the conduction band, they emit light of a color that depends on the size of the energy gap between the valence band and the conduction band. The narrower the energy gap, the more the emitted light is shifted toward the red, while the wider the energy gap, the more the emitted light is shifted toward the blue. By adjusting one or more properties of the quantum dots that change the energy gap between the conduction band and the valence band, the quantum dots can be made to emit light of almost any color in the visible spectrum.

[0019] Additional advances have combined μLEDs and quantum dots in high-resolution displays. The μLEDs are independently turned on and off by electronic circuitry in a backplane control panel to create a light source that photoexcites the quantum dots. Light from a more energetic μLED source (e.g., blue or ultraviolet) excites the quantum dots and causes them to emit light of a specific, lower energy color, such as blue, green, orange, or red. The excited quantum dots can emit light with improved emission characteristics, such as a narrower full-width at half-maximum wavelength spectrum, than the μLEDs. The ability of quantum dots to emit more distinct colors reduces the number of filters and polarizers required in the display to prevent light of unwanted colors from contaminating the displayed image.

[0020] Unfortunately, quantum dots emit visible light equally in all directions (i.e., they all emit light isotropically). This results in a large portion of the emitted light being directed away from the imaging direction where it is incorporated into the displayed image. As the width of the photoluminescent region decreases faster than its depth to increase the pixel density of a display component, an increasing portion of the light emitted from the quantum dots is directed away from the imaging direction. Thus, there may be a tradeoff between increasing pixel density and reducing the brightness of the displayed image. This tradeoff is addressed by increasing the power to the µLEDs so that they provide more UV light, which reduces the power efficiency of the display component and increases wasted heat. For device components located close to the viewer's eyes (e.g., wearable devices for virtual reality and augmented reality), the increased heat can make the device uncomfortable or impossible to wear.

[0021] The present technology solves these and other problems in conventional stacked LED and light emitting material structure designs that release too much light to emit in inefficient directions. In various embodiments, the present technology includes a pixel structure having a first bandpass filter located between a light emitting diode structure operable to generate UV light and a photoluminescent region containing a photoluminescent material such as an inorganic quantum dot or an organic light emitting compound. The first bandpass filter is operable to transmit ultraviolet light but block visible light. In various embodiments, this first bandpass filter may be referred to as a short bandpass filter. In further embodiments, the first bandpass filter may act as a window to transmit UV light emitted from the light emitting diode structure and a reflector to reflect visible light back into the photoluminescent region, the visible light being emitted in inefficient directions from the photoluminescent material contained in the region. The first bandpass filter assists in exciting the photoluminescent material with UV light from the LED structure and also increases the amount of visible light emitted by the excited photoluminescent material that moves in the direction of image display. In various embodiments, the present technology also includes a pixel structure having a second bandpass filter, the second bandpass filter being located on the side of the photoluminescent region opposite the first bandpass filter. The second bandpass filter is operable to transmit visible light but block ultraviolet light. In additional embodiments, the second bandpass filter can act as a window to transmit visible light emitted from the photoluminescent region to the displayed image and a reflector to reflect UV light that was not absorbed in the previous pass back to the photoluminescent region. In various embodiments, the present technology also still includes a photoluminescent region, the photoluminescent region having a first side adjacent to the first bandpass filter, the first side being wider than the second side adjacent to the second bandpass filter. The first side of the photoluminescent region being wider than the second side creates an oblique angle between the sidewall and the second side that is not a right angle and is greater than 90°. The present structure can also help to have more visible light from the photoluminescent region of the pixel structure in the direction of the displayed image.

[0022] Figure 1A flowchart showing selected operations in a method 100 of manufacturing a pixel according to various embodiments of the present technology. The method 100 may or may not include one or more operations before the method begins, including front-end processing, deposition, etching, grinding, cleaning, or any other operations that may be performed before the described operations. This method may include optional operations that may or may not be specifically associated with some embodiments of the method according to the present technology. The method 100 describes operations of an embodiment of forming a pixel structure, one of which is in Figure 2 A single pixel structure 200 is shown in a simplified schematic form, and the other one is shown as Figure 3 RGB pixel structure 300 in. Figure 2 and Figure 3 The cross-sectional views of the pixel structures 200 and 300 are split cross-sectional views showing a pixel structure that is cut between a first pair of sub-pixels and a second pair of sub-pixels and split to reveal a cross-sectional linear arrangement of red, green, and blue pixels. Figure 2 and Figure 3 Only partial schematic diagrams with limited detail are shown. In further embodiments not shown, the exemplary pixel structure may contain additional layers, regions, and materials, have aspects as shown in the figures, and alternative structural and material aspects that may still benefit from any aspects of the present technology.

[0023] The method 100 includes forming an LED structure 210 on a substrate 202 at operation 105. In various embodiments, the LED structure 210 may be a μLED structure operable to emit blue light or ultraviolet light. In some embodiments, the substrate 202 may be removed to expose a surface having a photoluminescent region formed thereon, and the LED structure 210 may be operable to emit ultraviolet light. In additional embodiments, the substrate 202 may form a backplane in electronic communication with the LED structure 210, and the LED structure may be operable to emit blue light having a peak emission wavelength in the visible blue portion of the visible spectrum. In further embodiments, the LED structure 210 may be operable to emit light characterized by a peak emission wavelength of less than or about 400 nm, less than or about 390 nm, less than or about 380 nm, less than or about 370 nm, less than or about 360 nm, less than or about 350 nm, less than or about 340 nm, less than or about 330 nm, or less. Figure 2 In the illustrated embodiment of the pixel structure 200 , the LED structure 210 formed on the substrate 202 is operable to emit ultraviolet (UV) light.

[0024] In various embodiments, the LED structure 210 may be a gallium and nitrogen containing LED structure. In further embodiments, the LED structure 210 may be a gallium nitride LED structure epitaxially formed on a substrate or a previously formed LED structure. In additional embodiments, the substrate 202 may be a silicon substrate or a sapphire substrate, or other types of substrates. In other additional embodiments, the LED structure 210 may further include an n-doped GaN layer and a p-doped GaN layer. A multi-quantum well (MQW) region is formed between the n-doped and p-doped GaN layers, in which light emitted by the LED structure 210 is generated. The LED structure 210 may further include a conductive N pad contact that forms a path for current to pass through the n-doped GaN layer. The LED structure 210 may also include a conductive P pad contact that forms a path for current to pass through the p-doped GaN layer. The N pad and P pad contacts may be connected to a conductive layer in the LED subpixel or directly to a contact in the control circuit system of the backplane. In various embodiments, an electrical signal from the control circuit system generates a current through the LED structure 210, which causes light to be emitted from the MQW region of the structure. In additional embodiments, the MQW region is formed to emit light having a repeatable peak intensity wavelength and quantum efficiency characterized by an applied electrical signal (e.g., current and / or voltage). In various embodiments, the peak intensity wavelength of light emitted from the MQW region can be an ultraviolet wavelength (e.g., a wavelength of light less than or about 400 nm).

[0025] The method 100 may further include contacting the LED structure 210 with a backplate (not shown) at operation 115. In various embodiments, the backplate may include contacts formed in the semiconductor layer that address the LED structure 210. In various embodiments, the contacts may be made of a conductive material, such as copper, aluminum, gold, tungsten, chromium, or nickel, or other conductive materials. In further embodiments, the LED structure 210 may be positioned between one or more transparent conductive layers that form a portion of a conductive path between the LED structure and the contacts in the backplate. In additional embodiments, the transparent conductive layers may be made of indium tin oxide or indium zinc oxide or other transparent conductive materials. In still further embodiments, a mirror layer (not shown) may be positioned adjacent to the one or more transparent conductive layers to reflect light emitted by the LED structure 210 toward the photoluminescent region 216. In further embodiments, the mirror layer may be made of one or more reflective metals, such as copper, aluminum, chromium, silver, platinum, or molybdenum, or other reflective metals. In further embodiments, a conductive bonding layer (not shown) bonding the LED substrate 202 to the backplane may be located between the mirror layer and the backplane. In further embodiments, the conductive bonding layer may be made of one or more conductive materials, such as tin, gold or indium or other conductive materials.

[0026] In various embodiments, the protective layer 212 can be formed on the LED structure 210. In additional embodiments, the protective layer 212 blocks or prevents moisture and other compounds from contacting the LED structure 210 while allowing light from the LED structure to be transmitted through the first bandpass filter 214 and into the photoluminescent region 216. In further embodiments, the protective layer 212 can include a silicon-containing dielectric material such as silicon oxide. In still further embodiments, the protective layer can be characterized by a depth between the LED structure 210 and the first bandpass filter 214 that is less than or about 2 μm, less than or about 1.5 μm, less than or about 1 μm, less than or about 0.75 μm, less than or about 0.5 μm, less than or about 0.4 μm, less than or about 0.3 μm, less than or about 0.2 μm, less than or about 0.1 μm, or less.

[0027] The method 100 may additionally further include forming a first bandpass filter 214 in the pixel structure 200 at operation 120. In various embodiments, the first bandpass filter may be located between the LED structure 210 and the photoluminescent region 216. In additional embodiments, the first bandpass filter may be formed on the LED structure 210, or on the protective layer 212 (if present). In further embodiments, the first bandpass filter 214 may be characterized as a short bandpass filter operable to transmit a greater percentage of light having a wavelength less than or about UV wavelengths than visible wavelengths. In still further embodiments, the first bandpass filter 214 may be operable to transmit greater than 50%, greater than or about 60%, greater than or about 70%, greater than or about 80%, greater than or about 90% of ultraviolet light. In additional embodiments, the first bandpass filter 214 may be operable to transmit less than 50%, less than 40%, less than 30%, less than 20%, less than 10%, less than 5%, less than 1%, or less of visible light.

[0028] Figure 4AAn exemplary light reflection and transmission profile is shown for an embodiment of the first bandpass filter 214. This profile shows that light having wavelengths significantly shorter than 400 nm is transmitted through the filter to the photoluminescent region 216, while light having wavelengths significantly longer than 400 nm is reflected toward the LED structure 210. In other embodiments, the transmission profile of the first bandpass filter 214 may have a 50% transmission / reflection wavelength shorter than or longer than 400 nm. In these embodiments, light having wavelengths significantly shorter than the 50% transmission / reflection wavelength is transmitted through the filter to the photoluminescent region 216, while light having wavelengths significantly longer than the 50% transmission / reflection wavelength is reflected toward the LED structure 210. In additional embodiments, the first bandpass filter 214 may be characterized by a 50% transmission / reflection wavelength that is less than 400 nm, less than or about 390 nm, less than or about 380 nm, less than or about 370 nm, or less. In further embodiments, the first bandpass filter 214 may be characterized by a 50% transmission / reflection wavelength greater than 400 nm, greater than or about 410 nm, greater than or about 420 nm, greater than or about 430 nm, or greater. From the perspective of the photoluminescent region 216, shorter wavelength UV light moving in the direction of the LED structure 210 is reflected into the photoluminescent region. This allows a greater percentage of UV light emitted by the LED structure 210 to be absorbed by the photoluminescent material 218 in the photoluminescent region 216.

[0029] The method 100 may also include forming a photoluminescent region 216 in the pixel structure 200 at operation 125. In various embodiments, the photoluminescent region 216 may include one or more photoluminescent materials 218, such as quantum dots, operable to absorb light emitted from the LED structure 210 and emit light having a specific color characteristic. In various embodiments, the photoluminescent region 216 may be formed in part by pixel isolation structures 220a-b. In further embodiments, the pixel isolation structures 220a-b reduce crosstalk generated by light from adjacent and nearby pixel structures. In various embodiments, the reduction in light intensity from adjacent and nearby pixel structures may be greater than or about 50%, greater than or about 60%, greater than or about 70%, greater than or about 80%, greater than or about 90%, greater than or about 95%, greater than or about 99%, or more.

[0030] In further embodiments, the pixel isolation structures 220a-b may extend above and around the LED structure 210. In other further embodiments, the sub-pixel isolation structures may extend near and below the contact area of ​​the LED structure 210, and may extend further downward to the backplane of the pixel structure. In more embodiments, the sub-pixel isolation structures 220a-b may include a core column of pixel isolation material, which is covered by one or more additional layers of material (e.g., a layer of reflective material such as aluminum or copper). In multiple embodiments, the material in the core column may include a metal or a dielectric material, or other types of materials. In further embodiments, the metal material may include one or more of silicon, tungsten, copper and aluminum, as well as other metals. In yet further embodiments, the dielectric material may include one or more of the following: silicon oxide, silicon nitride, silicon carbide, a photoresist material or a dielectric organic polymer material, or other dielectric materials. In further embodiments, the pixel isolation structures 220a-b may have a height of greater than or about 2.5 μm, greater than or about 5 μm, greater than or about 7.5 μm, greater than or about 10 μm, greater than or about 12.5 μm, greater than or about 15 μm, greater than or about 17.5 μm, greater than or about 20 μm, or greater. In other additional embodiments, the pixel isolation structures 220a-b may have a width of less than or about 5 μm, less than or about 4.5 μm, less than or about 4 μm, less than or about 3.5 μm, less than or about 3 μm, less than or about 2.5 μm, less than or about 2 μm, or less. In further embodiments, the pixel isolation structures 220a-b may have a height-to-width aspect ratio of greater than or about 1.5:1, greater than or about 2:1, greater than or about 2.5:1, greater than or about 3:1, greater than or about 3.5:1, greater than or about 4:1, greater than or about 4.5:1, greater than or about 5:1, or more. Figure 2 In the illustrated embodiment, the pixel structure 200 includes pixel isolation structures 220a - b .

[0031] In various embodiments, the pixel isolation structures 220a-b form sidewalls of the photoluminescent region 216, which also includes a first side adjacent to the first bandpass filter 214 and a second side opposite the first side and adjacent to the second bandpass filter 222. In further embodiments, a first width extending between the pixel isolation structures 220a to the first side of the pixel isolation structures 220b is less than a second width extending between the same pixel isolation structures 220a-b. In additional embodiments, the first width may be less than or about 4 μm, less than or about 3.5 μm, less than or about 3 μm, less than or about 2.5 μm, less than or about 2 μm, less than or about 1.5 μm, less than or about 1 μm, or less. The difference between the first and second widths of the first and second sides of the photoluminescent region 216 creates a tilt angle (α) between the pixel isolation structure 220b and the first side that is greater than 90° (i.e., not a right angle). In various embodiments, the tilt angle (α) may be characterized as greater than 90°, greater than 90.5°, greater than 91°, greater than 91.5°, greater than 92°, greater than 92.5°, greater than 93°, or greater. The larger width of the second side of the photoluminescent region 216 adjacent to the second bandpass filter 222 creates a larger area for visible light to exit the photoluminescent region and be incorporated into the displayed image.

[0032] The method 100 further includes depositing a photoluminescent material 218 in the photoluminescent region 216 of the pixel structure 200 at operation 130. In various embodiments, the as-deposited photoluminescent material may include one or more photoluminescent precursors in a mixture or slurry including a photocurable fluid and one or more photoluminescent particles or compounds. In further embodiments, the one or more photoluminescent compounds may include quantum dot materials that are operable to emit light having a specific color characteristic when excited by light from a source. In additional embodiments, these quantum dot materials may include nanoparticles made of one or more inorganic semiconductor materials, such as indium phosphide, zinc selenide, zinc sulfide, silicon, silicates, and graphene, as well as doped inorganic oxides, and other semiconductor materials. In further embodiments, the photocurable fluid may include one or more crosslinkable compounds, photoinitiators, and color converters. In additional embodiments, the crosslinkable compound may include monomers that form polymers when cured. In further embodiments, the monomers may include acrylate monomers, methacrylate monomers, and acrylamide monomers. In other more embodiments, the crosslinkable compound may include a negative photoresist, such as SU-8 photoresist. In further embodiments, the photoinitiator may include phosphine oxide compounds and ketone compounds, as well as other types of photoinitiator compounds, which generate free radicals that initiate the curing of the unsaturated compound when excited by ultraviolet light. Commercially available photoinitiator compounds include Irgacure 184, Irgacure 819, Darocur 1173, Darocur 4265, Darocur TPO, Omnicat 250 and Omnicat 550, as well as other photoinitiators.

[0033] When the as-deposited photoluminescent material includes one or more photoluminescent precursors, the precursors may be cured to form the photoluminescent material 218. In various embodiments, the curing operation may include exposing the photoluminescent precursors in the photoluminescent region 216 to a curing light that converts the photoluminescent precursors into the photoluminescent material 218. In further embodiments, the curing light may be characterized by a peak emission wavelength that is sufficiently short to activate one or more photocurable compounds in the photocurable fluid of the photoluminescent precursor. In yet more embodiments, the curing light can be characterized by a peak emission wavelength of less than or about 405 nm, less than or about 400 nm, less than or about 395 nm, less than or about 390 nm, less than or about 385 nm, less than or about 380 nm, less than or about 375 nm, less than or about 370 nm, less than or about 365 nm, less than or about 360 nm, less than or about 355 nm, less than or about 350 nm, less than or about 340 nm, less than or about 330 nm, less than or about 320 nm, less than or about 310 nm, less than or about 300 nm, or less. In still further embodiments, the curing light can be supplied by the LED structure 210. In these embodiments, supplying the curing light from the LED structure 210 can allow the photoluminescent material 218 in the photoluminescent region 216 to self-align with the LED structure 210. As the sub-pixel size decreases and the pixel density increases, self-alignment of the photoluminescent material with the LED structure becomes increasingly advantageous.

[0034] The method 100 may also further include forming a second bandpass filter 222 in the pixel structure 200 at operation 135. In various embodiments, the second bandpass filter 222 may be located between the photoluminescent region 216 and the microlens 224. In additional embodiments, the second bandpass filter 222 may be formed on the photoluminescent region 216, or on a UV filter (not shown) if the UV filter is present. In further embodiments, the second bandpass filter 222 may be characterized as a long bandpass filter operable to transmit a higher percentage of light having wavelengths in the visible wavelength region than shorter UV wavelengths. In still further embodiments, the second bandpass filter 222 may be operable to transmit greater than 50%, greater than or about 60%, greater than or about 70%, greater than or about 80%, greater than or about 90% of visible light. In additional embodiments, the second bandpass filter 222 is operable to transmit less than 50%, less than 40%, less than 30%, less than 20%, less than 10%, less than 5%, less than 1%, or less of ultraviolet light.

[0035] Figure 4BAn exemplary light reflection and transmission profile is shown for an embodiment of the second bandpass filter 222. This profile shows that light having wavelengths significantly longer than 400 nm is transmitted through the filter to the microlenses 224 and displays an image, while light having wavelengths significantly shorter than 400 nm is reflected toward the photoluminescent region 216. In additional embodiments, the transmission profile of the second bandpass filter 222 can have a 50% transmission / reflection wavelength shorter or longer than 400 nm. In these embodiments, light having wavelengths significantly longer than the 50% transmission / reflection wavelength is transmitted through the filter to the microlenses 224, while light having wavelengths significantly shorter than the 50% transmission / reflection wavelength is reflected toward the photoluminescent region 216. In additional embodiments, the second bandpass filter 222 can be characterized by a 50% transmission / reflection wavelength of less than 400 nm, less than or about 390 nm, less than or about 380 nm, less than or about 370 nm, or less. In further embodiments, the second bandpass filter 222 may be characterized by a 50% transmission / reflection wavelength greater than 400 nm, greater than or about 410 nm, greater than or about 420 nm, greater than or about 430 nm, or greater. From the perspective of the photoluminescent region 216, shorter wavelength UV light that moves in the direction of the microlenses 224 is reflected back toward the photoluminescent region. This allows a greater percentage of UV light emitted by the LED structure 210 to be absorbed by the photoluminescent material 218 in the photoluminescent region 216.

[0036] In various embodiments, the second bandpass filter 222 is used as a UV filter to block UV light from leaving the photoluminescent region in the direction of the displayed image. In additional embodiments, a UV filter (not shown) may be positioned adjacent to the second bandpass filter 222 to attenuate or block additional UV light from reaching the displayed image. In further embodiments, the UV filter may be a dielectric layer that absorbs UV light generated by the stacked LED structure 210 in the pixel structure 200 while transmitting visible light emitted by the photoluminescent material 218 in the photoluminescent region 216. In further embodiments, the dielectric layer may be a silicon oxide layer deposited by chemical vapor deposition or physical vapor deposition. In other additional embodiments, the UV filter may be made of an organic polymer, such as polyacrylate, polymethyl methacrylate, and copolymers of polyacrylate and polymethyl methacrylate. In still further embodiments, the UV filter may be made of commercially available materials, such as BASF's Tinuvin CarboProtect and Everlight's Eversorb series. In various embodiments, the UV filter can reduce the percentage of UV light in the total light emitted from the pixel structure to less than or about 5%, less than or about 2.5%, less than or about 1%, less than or about 0.5%, less than or about 0.1%, less than or about 0.05%, less than or about 0.01%, or less. In additional embodiments, the UV filter can transmit visible light from the pixel structure at a percentage of greater than or about 50%, greater than or about 75%, greater than or about 85%, greater than or about 90%, greater than or about 95%, greater than or about 99%, or more.

[0037] The method 100 also still includes forming a microlens 224 in the pixel structure 200 at operation 140. In various embodiments, the microlens 224 may be positioned adjacent to the second bandpass filter 222 and the UV filter (if present). In additional embodiments, the microlens 224 may be a convex lens, a concave lens, a Fresnel lens, or other lens shapes. In further embodiments, the microlens 224 may be made of an inorganic or organic material capable of transmitting visible light emitted from the pixel structure 200. In additional embodiments, the microlens 224 may be made of a polymer such as polydimethylsiloxane, polyacrylate, polymethyl methacrylate, polybutyl methacrylate, polystyrene, and poly(benzene methacrylate), among other polymers. In further embodiments, the microlens 224 may be made of an inorganic material such as silicon dioxide, zinc oxide, and aluminum oxide, among other inorganic materials. The microlens 224 bends and focuses the light emitted by the pixel structure to increase the image quality from the display component for a device such as a VR headset and AR glasses, among other devices. Figure 2 In the illustrated embodiment, the pixel structure 200 includes a microlens 224 .

[0038] Reference now Figure 3 , showing another pixel structure 300 according to an embodiment of the present invention. The pixel structure 300 includes three sub-pixel structures 302a-c, having photoluminescent materials 318a-c operable to emit light at red, green, and blue wavelengths, respectively. In various embodiments, forming the photoluminescent materials 318a-c in the photoluminescent regions 316a-c may include sequentially operating to form photoluminescent materials operable to emit light characterized by a specific peak intensity wavelength in one of the sub-pixels 302a-c of the pixel structure 300. In further embodiments, the sequentially operating may include: forming a first photoluminescent material 318a including red light emitting quantum dots in a first photoluminescent region 316a of the pixel structure 300; forming a second photoluminescent material 318b including green light emitting quantum dots in a second photoluminescent region 316b of the pixel structure; and forming a third photoluminescent material 318c including blue light emitting quantum dots in a third photoluminescent region 316c of the pixel structure. In yet further embodiments, a fourth sub-pixel structure (not shown) may be included in the pixel structure 300. The fourth sub-pixel may not include a photoluminescent material unless one of the remaining sub-pixel structures 302a-c is unable to properly emit light.

[0039] In various embodiments, the pixel structures 200 and 300 may be combined with additional pixel structures to form a display component. In further embodiments, the display component may be incorporated into a display device such as headphones, glasses, a screen, or a monitor, or other display device. In further embodiments, a display component containing the pixel structure of the present invention may be incorporated into a display device for virtual reality and / or augmented reality services.

[0040] In further embodiments, a display component incorporating the pixel structure of the present invention may be characterized by a pixel density of greater than or about 500 pixels per inch (ppi), greater than or about 1000 ppi, greater than or about 1500 ppi, greater than or about 2000 ppi, greater than or about 2500 ppi, greater than or about 3000 ppi, greater than or about 3500 ppi, greater than or about 4000 ppi, greater than or about 4500 ppi, greater than or about 5000 ppi, or greater. In further embodiments, the increased pixel density of the display component does not result in a decrease in the brightness of a displayed image produced by the display component. In multiple embodiments, the image brightness may be characterized by greater than or about 100 nits, greater than or about 250 nits, greater than or about 500 nits, greater than or about 750 nits, greater than or about 1000 nits, greater than or about 2500 nits, or greater. In further embodiments, pixel structures of the present technology may be characterized by an optical density of greater than or about 0.5, greater than or about 0.75, greater than or about 0.8, greater than or about 0.9, greater than or about 0.95, greater than or about 0.99, or greater.

[0041] Several embodiments have been described, and those skilled in the art will recognize that various modifications, alternative configurations, and equivalents may be used without departing from the spirit of the present invention. In addition, many known processes and components have not been described in order to avoid unnecessary confusion of the present invention. Therefore, the above description should not be considered as limiting the scope of the present invention.

[0042] When providing a numerical range, it is understood that, unless the context clearly dictates otherwise, each intervening value (to 1 / 10 of the unit of the lower limit) between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in the stated range and any other stated value or intervening value in the stated range is also encompassed. The upper and lower limits of these smaller ranges may be independently included in the stated range or excluded in the stated range, and each range in which any, none, or both limits are included in the smaller range is also encompassed in the invention, subject to any specifically excluded limits in the stated range. When the stated range includes one or both of the stated limits, ranges excluding either or both of the included limits are also included.

[0043] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to "a process" includes a plurality of such processes, and reference to "the pixel structure" includes reference to one or more pixel structures and equivalents thereof known to those skilled in the art, and the like.

[0044] Likewise, when used in this specification and the claims that follow, the terms "comprises," "comprising," and "containing" are intended to specify the presence of stated features, integers, components or steps, but they do not exclude the presence or addition of one or more other features, integers, components, steps, actions or groups.

Claims

1. A pixel structure, comprising: a light emitting diode structure operable to generate ultraviolet light; a photoluminescent region containing a photoluminescent material; a first bandpass filter disposed between the LED structure and the photoluminescent region, wherein the first bandpass filter is operable to transmit ultraviolet light; and A second band pass filter is located on an opposite side of the photoluminescent region from the first band pass filter, wherein the second band pass filter is operable to transmit visible light. 2 . The pixel structure according to claim 1 , wherein the photoluminescent region comprises a first side adjacent to the first bandpass filter and a second side adjacent to the second bandpass filter, wherein the second side of the photoluminescent region is wider than the first side.

3. The pixel structure of claim 2, wherein the photoluminescent region further comprises a first sidewall in contact with the first bandpass filter, and wherein the first sidewall and the first bandpass filter are characterized by an inclination angle greater than 90 degrees. 4 . The pixel structure according to claim 1 , wherein the pixel structure further comprises a microlens structure, and wherein the second bandpass filter is located between the microlens structure and the photoluminescent region. 5 . The pixel structure according to claim 1 , wherein the pixel structure further comprises a protection region, wherein the protection region is located between the light-emitting diode structure and the first bandpass filter.

6. The pixel structure of claim 1 , wherein the photoluminescent material in the photoluminescent region comprises a quantum dot material operable to absorb a first wavelength of light from the light emitting diode structure and emit a second wavelength of light longer than the first wavelength.

7. The pixel structure of claim 2, wherein the photoluminescent region is characterized by a depth between the first side and the second side, the depth being greater than or approximately 1 micron.

8. The pixel structure of claim 7, wherein the first side is further characterized by a width across the photoluminescent region, the width being less than or approximately 30 microns.

9. A pixel structure comprising: a light emitting diode structure operable to generate ultraviolet light; as well as A photoluminescent region is located above the light emitting diode structure, wherein the photoluminescent region is characterized by a depth between a first side and a second side of the photoluminescent region, and wherein the first side of the photoluminescent region is shorter than the second side.

10. The pixel structure according to claim 9, wherein the photoluminescent region comprises a third side, the third side comprises a sidewall region between the first side and the second side of the photoluminescent region, and wherein the inclination angle between the first side and the third side is greater than 90 degrees.

11. The pixel structure of claim 9, wherein the first side is characterized by a width of less than or about 4 microns.

12. The pixel structure of claim 9, wherein the first side is characterized by a width greater than 4 microns.

13. The pixel structure of claim 9, wherein the first side is adjacent to a short bandpass filter between the light emitting diode structure and the photoluminescent region, and wherein the short bandpass filter is operable to transmit ultraviolet light, and Wherein the second side is adjacent to a long bandpass filter, the long bandpass filter being located on an opposite side of the photoluminescent region from the short bandpass filter, and wherein the long bandpass filter is operable to transmit visible light.

14. The pixel structure of claim 9, wherein the photoluminescent region comprises a photoluminescent material comprising a quantum dot material operable to absorb a first wavelength of light from the light emitting diode structure and emit a second wavelength of light longer than the first wavelength.

15. A display component, comprising: A plurality of pixel structures, wherein each of the pixel structures comprises: a light emitting diode structure operable to generate ultraviolet light; a photoluminescent region containing a photoluminescent material; a first bandpass filter disposed between the light-emitting diode structure and the photoluminescent region, wherein the first bandpass filter is operable to transmit ultraviolet light; and A second band pass filter is located on an opposite side of the photoluminescent region from the first band pass filter, wherein the second band pass filter is operable to transmit visible light.

16. A display component according to claim 15, wherein the pixel structure further includes a first side of the photoluminescent region adjacent to the first bandpass filter and a second side of the photoluminescent region adjacent to the second bandpass filter, wherein the second side is wider than the first side, and wherein the photoluminescent region further includes a first sidewall in contact with the first bandpass filter, and the first sidewall and the first bandpass filter are characterized by an inclination angle greater than 90 degrees.

17. A display component according to claim 15, wherein in each of the pixel structures, the photoluminescent material in the photoluminescent region includes a quantum dot material, which is operable to absorb a first wavelength of light from the light-emitting diode structure and emit a second wavelength of light shorter than the first wavelength, and the light-emitting diode structure is a micro light-emitting diode structure.

18. The display component of claim 15, wherein the display component is characterized by a pixel density greater than or about 3000 pixels per inch (ppi).

19. The display component of claim 15, wherein the display component is characterized by an optical density greater than or about 1.

20. The display component of claim 15, wherein the display component is operable to be incorporated into an augmented reality display device.

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