Light-emitting diodes with improved light conversion efficiency

Abstract

An embodiment of the present technology includes a pixel structure. The pixel structure includes a light emitting diode structure that generates ultraviolet light. The pixel structure further includes a photoluminescent region containing a photoluminescent material. The pixel structure further includes a first bandpass filter disposed between the light emitting diode structure and the photoluminescent region, the first bandpass filter operable to transmit more than 50% of light having a wavelength of about 400 nm or less. The pixel structure further includes a second bandpass filter disposed on the opposite side of the photoluminescent region from the first bandpass filter, the second bandpass filter operable to transmit more than 50% of light having a wavelength longer than 400 nm.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 406,937, entitled "LIGHT EMITTING DIODE WITH INCREASED LIGHT CONVERSION EFFICIENCY," filed September 15, 2023, which is incorporated herein by reference in its entirety.

[0002] The present technology relates to displays having pixel structures that combine light-emitting diode (LED) structures with photoluminescent regions containing photoluminescent materials, such as quantum dots. [Background technology]

[0003] High-resolution light-emitting diode (LED) displays can contain millions of micron-sized pixels arranged to form a display screen. Traditional LED displays generate color images by filtering white light from an LED light source into red, green, and blue pixels, which then emit light of varying intensities across the display screen. Other LED displays excite organic or inorganic compounds, which then emit specific colors of light, such as red, green, or blue light, depending on the pixel. These LED displays typically require fewer filters to block unwanted colors of light and can produce a more accurate color gamut. However, many photoluminescent materials have relatively low conversion efficiency between excitation light and the desired visible light. These materials also emit light in all directions and can scatter light. These properties of light-emitting compounds can reduce the brightness of the displayed image.

[0004] Therefore, there is a need for pixel designs that produce brighter images for display devices that include excitable emissive materials. These and other needs are addressed by the present technology.

[0005] A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings, in which like reference numerals are used to refer to like components throughout the several views. In some instances, a sub-label is associated with a reference numeral and follows a hyphen to indicate one of multiple similar components. When referring to a reference numeral without specifying an existing sub-label, it is intended to refer to all of such multiple similar components. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a flowchart illustrating selected operations of an exemplary method for fabricating a pixel structure in accordance with embodiments of the present technology. [Figure 2] 1 is a simplified cross-sectional view of an exemplary single pixel structure in accordance with an embodiment of the present technology; [Figure 3] 1 is a simplified cross-sectional view of an exemplary RGB pixel structure in accordance with an embodiment of the present technology; [Figure 4A] 1 is a graph of an exemplary first bandpass filter in accordance with an embodiment of the present technology; [Figure 4B] 10 is a graph of an exemplary second bandpass filter in accordance with an embodiment of the present technology. Summary of the Invention

[0007] An embodiment of the present technology includes a pixel structure. The pixel structure includes a light emitting diode structure that generates ultraviolet light. The pixel structure further includes a photoluminescent region containing a photoluminescent material. The pixel structure further includes a first bandpass filter disposed between the light emitting diode structure and the photoluminescent region, the first bandpass filter operable to transmit ultraviolet light. The pixel structure further includes a second bandpass filter disposed on an opposite side of the photoluminescent region from the first bandpass filter, the second bandpass filter operable to transmit visible light.

[0008] In additional embodiments, the photoluminescent region of the pixel structure can include a first side adjacent to the first bandpass filter and a second side adjacent to the second bandpass filter, the second side of the photoluminescent region being wider than the first side. In further embodiments, the photoluminescent region can further include a first sidewall in contact with the first bandpass filter, the first sidewall and the first bandpass filter being characterized by a slope angle greater than 90°. In still further embodiments, the pixel structure can include a microlens structure, the second bandpass filter being disposed between the microlens structure and the photoluminescent region. In yet additional embodiments, the pixel structure can include a protection region disposed between the light-emitting diode structure and the first bandpass filter. In further embodiments, the photoluminescent material of the photoluminescent region of the pixel structure can 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 yet other embodiments, the photoluminescent region is characterized by a depth between the first and second sides of about 1 μm or greater, and in yet other embodiments, the first side of the photoluminescent region is characterized by a width across the photoluminescent region of about 30 μm or less.

[0009] Additional embodiments of the present technology include additional pixel structures including a light emitting diode structure operable to generate ultraviolet light and a photoluminescent region disposed over the light emitting diode structure, the photoluminescent region being characterized by a depth between a first side and a second side of the photoluminescent region, the first side being shorter than the second side.

[0010] In a further embodiment, the photoluminescent region of the pixel structure includes a third side including a sidewall region between the first side and the second side of the photoluminescent region, and the slope angle between the first side and the third side is greater than 90°. In yet a further embodiment, the first side of the photoluminescent region is characterized by a width of about 4 μm or less. In an additional embodiment, the first side of the photoluminescent region is adjacent to a short bandpass filter disposed between the light emitting diode structure and the photoluminescent region, the short bandpass filter operable to transmit ultraviolet light, and the second side of the photoluminescent region is adjacent to a long bandpass filter disposed opposite the photoluminescent region, the long bandpass filter operable to transmit visible light. In an additional embodiment, the photoluminescent region of the pixel structure includes a photoluminescent material including 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.

[0011] Further embodiments of the present technology include a display component having a plurality of pixel structures, each of which includes a light-emitting diode structure operable to generate ultraviolet light and a photoluminescent region containing a photoluminescent material. The pixel structures further include a first band-pass filter between the light-emitting diode structure and the photoluminescent region, the first band-pass filter operable to transmit ultraviolet light. The pixel structures further include a second band-pass filter disposed on an opposite side of the photoluminescent region from the first band-pass filter, the second band-pass filter operable to transmit visible light.

[0012] In a further embodiment, 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, the second side being wider than the first side, the photoluminescent region further including a first sidewall in contact with the first bandpass filter, the first sidewall and the first bandpass filter being characterized by a slope angle greater than 90°. In yet another embodiment, the photoluminescent material in the photoluminescent region of the pixel structure includes a quantum dot material operable to absorb light of a first wavelength from a light emitting diode structure and emit light of a second wavelength shorter than the first wavelength, the light emitting diode structure being a micro light emitting diode structure. In a further embodiment, the display component is characterized by a pixel density of about 3000 pixels per inch (ppi) or greater. In yet a further embodiment, the display component is characterized by an optical density of about 1 or greater. In an additional embodiment, the display component is operable to be incorporated into an augmented reality display device.

[0013] The present technology offers several advantages over conventional designs for pixel structures and display components incorporating them. 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 above the photoluminescent region. Also, many conventional designs have sidewalls formed at right angles (i.e., at a 90° angle) to the top and bottom surfaces of the photoluminescent region. These design features reduce the percentage of visible light generated in the photoluminescent region that contributes to the displayed image. In embodiments 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, reflecting more visible light into the photoluminescent region and outputting it to the displayed image. Further embodiments of the present technology include a long bandpass filter positioned above the photoluminescent region, which can reflect UV light back into the photoluminescent region while allowing visible light to pass through to the displayed image. Yet another embodiment of the present technology widens the top surface of the photoluminescent region, through which visible light passes to form a displayed image, relative to the bottom surface of the photoluminescent region adjacent to the light-emitting diode structure. By widening the top surface relative to the bottom surface of the photoluminescent region, more visible light can pass through to the image compared to conventional photoluminescent regions with the same top and bottom widths. These and other embodiments, along with many of their advantages and features, will be described in more detail in conjunction with the following description and accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION

[0014] Technological advances in high-resolution displays include developing micro-light-emitting diodes (μLEDs) from inorganic semiconductor materials and using photoluminescent materials such as quantum dots in displays. μLEDs are made from layers of semiconductor materials, such as indium gallium nitride (InGaN), which can be configured to emit light at a specific peak emission wavelength when excited by an applied electric field. Semiconductor fabrication processes are used to create μLEDs with a longest dimension of approximately 50 μm or less and operable to emit red, green, or blue light. Quantum dots are nanometer-sized particles of inorganic materials that can emit light of a specific color after being excited by more energetic light. The color of the emitted light can depend on one or more characteristics of the particle, including its size, shape, and composition, among other properties. For quantum dots made from inorganic semiconductor materials, the color of the emitted light is determined by the energy gap between the dot's conduction and valence bands. 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 return to the conduction band, they emit light whose color depends on the size of the energy gap between the valence band and the conduction band. The narrower the energy gap, the more red-shifted the emitted light is; the wider the energy gap, the more blue-shifted the emitted light is. By tuning one or more properties of the quantum dot that change the energy gap between the conduction and valence bands, quantum dots can be made to emit light of virtually any color in the visible spectrum.

[0015] Further advances have combined μLEDs and quantum dots in high-resolution displays. μLEDs, individually switched on and off by electronic circuitry in a backplane control panel, generate source light that optically excites the quantum dots. Higher-energy μLED source light, such as blue or ultraviolet light, excites the quantum dots, causing them to emit light of specific, lower-energy colors, such as blue, green, orange, or red. The excited quantum dots can emit light with improved emission characteristics, such as a narrower full-width half-maximum wavelength spectrum than μLEDs. Because quantum dots can emit light in more vivid colors, fewer color filters and polarizers are required in displays to block unwanted colored light from contaminating the displayed image.

[0016] Unfortunately, quantum dots emit visible light equally in all directions (i.e., they emit light isotropically). This results in a significant portion of the emitted light diverging from the imaging direction, where the light is captured in the displayed image. To increase the pixel density of a display component, if the width of the photoluminescent region is reduced more rapidly than its depth, an increasing proportion of the light emitted from the quantum dots diverges from the imaging direction. As a result, there can be a trade-off between increased pixel density and reduced brightness of the displayed image. Addressing this trade-off by increasing the power to the μLEDs so that they provide more UV light reduces the power efficiency of the display component and increases waste heat. For device components located near the viewer's eyes, such as wearable virtual and augmented reality devices, the increased heat can make the device uncomfortable or unwearable.

[0017] The present technology addresses these and other problems associated with conventional stacked LED and luminescent material structure designs, where too much light is lost to emission in unproductive directions. In embodiments, the present technology includes a pixel structure having a first bandpass filter disposed between a light-emitting diode structure operable to generate UV light and a photoluminescent region containing a photoluminescent material, such as inorganic quantum dots or an organic light-emitting compound. The first bandpass filter is operable to transmit ultraviolet light but block visible light. In embodiments, this first bandpass filter may be referred to as a short-bandpass filter. In further embodiments, the first bandpass filter can function both as a window for transmitting UV light emitted from the light-emitting diode structure and as a reflector for reflecting visible light emitted in unproductive directions from the photoluminescent material contained in the photoluminescent region back to the photoluminescent region. The first bandpass filter promotes excitation of the photoluminescent material by UV light from the LED structure and also increases the amount of visible light emitted by the excited photoluminescent material traveling in an image display direction. In an embodiment, the present technology also includes a pixel structure having a second bandpass filter positioned on the opposite side of the photoluminescent region from the first bandpass filter. The second bandpass filter is operable to transmit visible light but block ultraviolet light. In an additional embodiment, the second bandpass filter can function both as a window for transmitting visible light emitted from the photoluminescent region to a display image and as a reflector for reflecting UV light not absorbed in the previous pass back to the photoluminescent region. In an embodiment, the present technology still includes a photoluminescent region in which a first side adjacent to the first bandpass filter is wider than a second side adjacent to the second bandpass filter. The wider first side of the photoluminescent region than the second side creates a slope angle greater than 90° between the sidewall and the second side, rather than a right angle. The present structure can also promote more visible light from the photoluminescent region of the pixel structure toward the display image.

[0018] FIG. 1 illustrates a flow diagram with selected operations in a method 100 for fabricating pixels according to embodiments of the present technology. Method 100 may or may not include one or more operations prior to the start of the method, including front-end processing, deposition, etching, polishing, cleaning, or any other operations that may be performed before the described operations. The method may include optional operations that may or may not be specifically associated with some embodiments of methods according to the present technology. Method 100 describes operations for forming embodiments of pixel structures, one of which is shown in simplified schematic form in FIG. 2 as a single pixel structure 200 and another of which is shown in FIG. 3 as an RGB pixel structure 300. The cross-sectional views of pixel structures 200 and 300 in FIGS. 2 and 3 are split-and-unfolded cross-sections cut between a first and second subpixel pair and showing the pixel structures split and unfolded to reveal the linear arrangement of the red, green, and blue pixels in cross section. FIGS. 2 and 3 illustrate only partial schematic views with limited detail. In further embodiments not shown, the exemplary pixel structures can include additional layers, regions, and materials having aspects as shown, as well as alternative structural and material aspects that can still benefit from any aspects of the present technology.

[0019] The method 100 includes, in operation 105, forming an LED structure 210 on a substrate 202. In embodiments, the LED structure 210 may be a μLED structure operable to emit blue or ultraviolet light. In some embodiments, the substrate 202 may be removed to expose a surface on which a photoluminescent region is formed, 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 about 400 nm or less, about 390 nm or less, about 380 nm or less, about 370 nm or less, about 360 nm or less, about 350 nm or less, about 340 nm or less, about 330 nm or less, or less. In the embodiment of pixel structure 200 shown in FIG. 2, an LED structure 210 formed on a substrate 202 is operable to emit ultraviolet (UV) light.

[0020] In 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, among other types of substrates. In still further embodiments, the LED structure 210 may further include an n-type doped GaN layer and a p-type doped GaN layer. A multiple quantum well (MQW) region is formed between the n-type doped GaN layer and the p-type doped GaN layer, where the 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 through the n-type doped GaN layer. The LED structure 210 may also include a conductive P-pad contact that forms a path for current through the p-type doped GaN layer. The N-pad contact and the P-pad contact may be connected to conductive layers within the LED subpixel or directly to contacts of the control circuitry on the backplane. In embodiments, an electrical signal from a control circuit generates a current flow through the LED structure 210, causing light to be emitted from the MQW region of the structure. In additional embodiments, the MQW region is configured to emit light characterized by a reproducible peak intensity wavelength and quantum efficiency in response to an applied electrical signal (e.g., current and / or voltage). In embodiments, the peak intensity wavelength of the light emitted from the MQW region may be an ultraviolet light wavelength (e.g., a wavelength of light of about 400 nm or less).

[0021] The method 100 may further include, in operation 115, contacting the LED structure 210 with a backplane (not shown). In embodiments, the backplane may include contacts formed in semiconductor layers corresponding to the LED structure 210. In embodiments, the contacts may be made of a conductive material such as copper, aluminum, gold, tungsten, chromium, or nickel, among other conductive materials. In still further embodiments, the LED structure 210 may be disposed between one or more transparent conductive layers that form part of an electrical conduction path between the LED structure and the contacts of the backplane. In additional embodiments, the transparent conductive layer may be made of indium tin oxide or indium zinc oxide, among other transparent conductive materials. In yet other embodiments, a mirror layer (not shown) may be disposed adjacent to the one or more transparent electrical 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, among other reflective metals. In still further embodiments, a conductive bonding layer (not shown) that bonds the LED substrate 202 to the backplane may be disposed between the mirror layer and the backplane. In further embodiments, the conductive bonding layer may be made from one or more conductive materials such as tin, gold, or indium, among other conductive materials.

[0022] In embodiments, a protective layer 212 may be formed over 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 transmit through the first bandpass filter 214 to the photoluminescent region 216. In further embodiments, the protective layer 212 may include a silicon-containing dielectric material, such as silicon oxide. In still further embodiments, the protective layer may be characterized by a depth between the LED structure 210 and the first bandpass filter 214 of about 2 μm or less, about 1.5 μm or less, about 1 μm or less, about 0.75 μm or less, about 0.5 μm or less, about 0.4 μm or less, about 0.3 μm or less, about 0.2 μm or less, about 0.1 μm or less, or less.

[0023] The method 100 may further include, in operation 120, forming a first bandpass filter 214 in the pixel structure 200. In an embodiment, the first bandpass filter may be disposed between the LED structure 210 and the photoluminescent region 216. In an additional embodiment, the first bandpass filter may be formed on the LED structure 210 or, if present, on the protective layer 212. In a further embodiment, the first bandpass filter 214 may be characterized as a short bandpass filter operable to transmit a higher percentage of light having wavelengths approximately equal to or shorter than the UV wavelengths compared to visible wavelengths. In still other embodiments, the first bandpass filter 214 may be operable to transmit more than 50%, about 60% or more, about 70% or more, about 80% or more, or about 90% or more 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 than that of visible light.

[0024] 4A shows an exemplary optical reflectance and transmittance profile of one embodiment of first bandpass filter 214. This profile indicates that light with wavelengths significantly shorter than 400 nm is transmitted through the filter to photoluminescent region 216, while light with wavelengths significantly longer than 400 nm is reflected back toward LED structure 210. In other embodiments, the transmission profile of first bandpass filter 214 can have a 50% transmission / reflection wavelength shorter or longer than 400 nm. In these embodiments, light with wavelengths significantly shorter than the 50% transmission / reflection wavelength is transmitted through the filter to photoluminescent region 216, while light with wavelengths significantly longer than the 50% transmission / reflection wavelength is reflected back toward LED structure 210. In additional embodiments, first bandpass filter 214 may be characterized by a 50% transmission / reflection wavelength less than 400 nm, about 390 nm or less, about 380 nm or less, about 370 nm or less, or even lower. In further embodiments, first bandpass filter 214 may be characterized by a 50% transmission / reflection wavelength of greater than 400 nm, about 410 nm or greater, about 420 nm or greater, about 430 nm or greater, or even greater. From the perspective of photoluminescent region 216, shorter wavelength UV light traveling in the direction of LED structure 210 is reflected into the photoluminescent region. This causes a greater percentage of the UV light emitted by LED structure 210 to be absorbed by photoluminescent material 218 in photoluminescent region 216.

[0025] Method 100 may also include, in operation 125, forming a photoluminescent region 216 in pixel structure 200. In embodiments, photoluminescent region 216 may include one or more photoluminescent materials 218, such as quantum dots, operable to absorb light emitted from LED structure 210 and emit light having particular color characteristics. In embodiments, photoluminescent region 216 may be formed in part from pixel isolation structures 220a-b. In further embodiments, pixel isolation structures 220a-b reduce crosstalk generated by light from adjacent and nearby pixel structures. In embodiments, the reduction in intensity of light from adjacent and nearby pixel structures may be about 50% or more, about 60% or more, about 70% or more, about 80% or more, about 90% or more, about 95% or more, about 99% or more, or more.

[0026] In further embodiments, the pixel isolation structures 220a-b may extend above and around the LED structure 210. In yet other embodiments, the subpixel isolation structures may extend adjacent to and below the contact regions of the LED structure 210, or may extend further to the backplane of the pixel structure. In further embodiments, the subpixel isolation structures 220a-b may include a core column of pixel isolation material covered by one or more additional layers of material, such as a layer of a reflective material such as aluminum or copper. In embodiments, the core column material may include a metal or a dielectric material, among other types of materials. In further embodiments, the metal material may include one or more of silicon, tungsten, copper, and aluminum, among other metals. In still other embodiments, the dielectric material may include one or more of silicon oxide, silicon nitride, silicon carbide, a photoresist material, or a dielectric organic polymer material, among other dielectric materials. In still further embodiments, the pixel separating structures 220a-b can have heights of about 2.5 μm or more, about 5 μm or more, about 7.5 μm or more, about 10 μm or more, about 12.5 μm or more, about 15 μm or more, about 17.5 μm or more, about 20 μm or more, or more. In yet additional embodiments, the pixel separating structures 220a-b can have widths of about 5 μm or less, about 4.5 μm or less, about 4 μm or less, about 3.5 μm or less, about 3 μm or less, about 2.5 μm or less, about 2 μm or less, or less. In still further embodiments, the pixel separating structures 220a-b can have height-to-width aspect ratios of about 1.5:1 or more, about 2:1 or more, about 2.5:1 or more, about 3:1 or more, about 3.5:1 or more, about 4:1 or more, about 4.5:1 or more, about 5:1 or more, or more. In the embodiment shown in FIG. 2, pixel structure 200 includes pixel separating structures 220a-b.

[0027] In an embodiment, pixel separating structures 220a-b form sidewalls of photoluminescent region 216, including a first side adjacent first bandpass filter 214 and a second side opposite the first side adjacent second bandpass filter 222. In a further embodiment, a first width of the first side extending between pixel separating structures 220a and 220b is less than a second width of the second side extending between the same pixel separating structures 220a-b. In additional embodiments, the first width may be about 4 μm or less, about 3.5 μm or less, about 3 μm or less, about 2.5 μm or less, about 2 μm or less, about 1.5 μm or less, about 1 μm or less, or less. The difference between the first width of the first side and the second width of the second side of photoluminescent region 216 creates a tilt angle (α) between pixel separating structure 220b and the first side that is greater than 90° (i.e., not a right angle). In 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 wider second side of photoluminescent region 216 adjacent second bandpass filter 222 increases the area over which visible light can exit the photoluminescent region and be captured in the displayed image.

[0028] The method 100 further includes, in operation 130, depositing a photoluminescent material 218 in the photoluminescent region 216 of the pixel structure 200. In embodiments, the as-deposited photoluminescent material may include one or more photoluminescent precursors in a mixture or slurry including a light-curable fluid and one or more photoluminescent particles or compounds. In further embodiments, the one or more photoluminescent compounds may include quantum dot materials operable to emit light having specific color characteristics when excited by source light. In additional embodiments, these quantum dot materials may include nanoparticles made from one or more types of inorganic semiconductor materials, such as indium phosphide, zinc selenide, zinc sulfide, silicon, silicates, and graphene, as well as doped inorganic oxides, among other semiconductor materials. In further embodiments, the light-curable fluid may include one or more crosslinking compounds, a photoinitiator, and a color conversion agent. In additional embodiments, the crosslinking compounds may include monomers that form polymers when cured. In further embodiments, the monomers may include acrylate monomers, methacrylate monomers, and acrylamide monomers. In yet another embodiment, the crosslinkable compound can include a negative photoresist material, such as SU-8 photoresist. In a further embodiment, the photoinitiator can include phosphine oxide compounds and keto compounds, among other types of photoinitiator compounds, that generate radicals that initiate the curing of unsaturated compounds 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, among other photoinitiators.

[0029] If the as-deposited photoluminescent material includes one or more photoluminescent precursors, the precursors may be cured to form the photoluminescent material 218. In embodiments, the curing operation may include exposing the photoluminescent precursors of the photoluminescent region 216 to a curing light that converts the photoluminescent precursors to the photoluminescent material 218. In still further embodiments, the curing light may be characterized by a peak emission wavelength that is sufficiently short to activate one or more of the photocurable compounds in the photocurable fluid of the photoluminescent precursor. In yet other embodiments, the curing light may be characterized by a peak emission wavelength of about 405 nm or less, about 400 nm or less, about 395 nm or less, about 390 nm or less, about 385 nm or less, about 380 nm or less, about 375 nm or less, about 370 nm or less, about 365 nm or less, about 360 nm or less, about 355 nm or less, about 350 nm or less, about 340 nm or less, about 330 nm or less, about 320 nm or less, about 310 nm or less, about 300 nm or less, or less. In still further embodiments, the curing light may be provided by the LED structure 210. In these embodiments, providing the curing light from the LED structure 210 may enable self-alignment of the photoluminescent material 218 in the photoluminescent region 216 with the LED structure 210. Self-alignment of the photoluminescent material with the LED structure becomes increasingly beneficial as the size of the subpixel decreases and pixel density increases.

[0030] Method 100 may further include, in operation 135, forming a second bandpass filter 222 in pixel structure 200. In an embodiment, second bandpass filter 222 may be disposed between photoluminescent region 216 and microlens 224. In additional embodiments, second bandpass filter 222 may be formed on photoluminescent region 216 or on a UV filter (not shown), if present. In further embodiments, second bandpass filter 222 may be characterized as a long bandpass filter operable to transmit a greater percentage of light having wavelengths in the visible wavelength range compared to shorter UV wavelengths. In yet other embodiments, second bandpass filter 222 may be operable to transmit more than 50%, about 60% or more, about 70% or more, about 80% or more, or about 90% or more of visible light. In additional embodiments, the second bandpass filter 222 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 than ultraviolet light.

[0031] 4B shows an exemplary optical reflectance and transmittance profile of one embodiment of second bandpass filter 222. The profile indicates that light with wavelengths significantly longer than 400 nm is transmitted through the filter to microlens 224 and the displayed image, while light with wavelengths significantly shorter than 400 nm is reflected toward photoluminescent region 216. In additional embodiments, the transmission profile of second bandpass filter 222 can have a 50% transmission / reflection wavelength shorter or longer than 400 nm. In these embodiments, light with wavelengths significantly longer than the 50% transmission / reflection wavelength is transmitted through the filter to microlens 224, while light with wavelengths significantly shorter than the 50% transmission / reflection wavelength is reflected toward photoluminescent region 216. In additional embodiments, second bandpass filter 222 may be characterized by a 50% transmission / reflection wavelength less than 400 nm, about 390 nm or less, about 380 nm or less, about 370 nm or less, or even lower. In further embodiments, the second bandpass filter 222 may be characterized by a 50% transmission / reflection wavelength of greater than 400 nm, greater than or equal to about 410 nm, greater than or equal to about 420 nm, greater than or equal to about 430 nm, or even greater. From the perspective of the photoluminescent region 216, shorter wavelength UV light traveling in the direction of the microlenses 224 is reflected back into the photoluminescent region. This causes a greater percentage of the UV light emitted by the LED structure 210 to be absorbed by the photoluminescent material 218 in the photoluminescent region 216.

[0032] In an embodiment, the second bandpass filter 222 functions as a UV filter that blocks UV light from exiting the photoluminescent region toward the displayed image. In additional embodiments, a UV filter (not shown) can 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 structures 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 still further embodiments, the UV filter may be made from organic polymers such as polyacrylate, polymethyl methacrylate, and copolymers of polyacrylate and polymethyl methacrylate. In still other embodiments, the UV filter may be made from commercially available materials such as Tinuvin CarboProtect from BASF and the Eversorb series from Everlight. In embodiments, the UV filter can reduce the percentage of UV light in the total light emitted from the pixel structure to about 5% or less, about 2.5% or less, about 1% or less, about 0.5% or less, about 0.1% or less, about 0.05% or less, about 0.01% or less, or less. In additional embodiments, the UV filter can transmit about 50% or more, about 75% or more, about 85% or more, about 90% or more, about 95% or more, about 99% or more, or more, of the visible light from the pixel structure.

[0033] The method 100 also includes, in operation 140, forming a microlens 224 in the pixel structure 200. In an embodiment, the microlens 224 may be disposed adjacent to the second bandpass filter 222 and, if present, the UV filter. In additional embodiments, the microlens 224 may be a convex lens, a concave lens, or a Fresnel lens, among other lens shapes. In further embodiments, the microlens 224 may be made from an inorganic or organic material that can transmit visible light emitted from the pixel structure 200. In additional embodiments, the microlens 224 may be made from a polymer such as polydimethylsiloxane, polyacrylate, polymethyl methacrylate, polybutyl methacrylate, polystyrene, and poly(benzyl methacrylate), among other polymers. In further embodiments, the microlens 224 may be made from an inorganic material such as silica, zinc oxide, and aluminum oxide, among other inorganic materials. The microlenses 224 bend and focus the light emitted by the pixel structure to improve the quality of images from display components for devices such as VR headsets and AR glasses, among other devices. In the embodiment shown in FIG. 2, the pixel structure 200 includes microlenses 224.

[0034] 3, another pixel structure 300 is shown in accordance with an embodiment of the present technology. 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 an embodiment, forming the photoluminescent materials 318a-c in the photoluminescent regions 316a-c may include sequential operations to form photoluminescent materials operable to emit light characterized by a particular peak intensity wavelength in one of the sub-pixels 302a-c of the pixel structure 300. In a further embodiment, the sequential operation may include forming a first photoluminescent material 318a including red-emitting quantum dots in a first photoluminescent region 316a of the pixel structure 300, a second photoluminescent material 318b including green-emitting quantum dots in a second photoluminescent region 316b of the pixel structure, and a third photoluminescent material 318c including blue-emitting quantum dots in a third photoluminescent region 316c of the pixel structure. In a further embodiment, a fourth subpixel structure (not shown) may be included in the pixel structure 300. The fourth subpixel may not include a photoluminescent material unless one of the other subpixel structures 302a-c is unable to properly illuminate.

[0035] In embodiments, pixel structures 200 and 300 can 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 a headset, glasses, a screen, or a monitor, among other display devices. In still further embodiments, a display component including the present pixel structures may be incorporated into a display device for virtual reality and / or augmented reality services.

[0036] In further embodiments, display components incorporating the present pixel structures may be characterized by pixel densities of about 500 pixels per inch (ppi) or greater, about 1000 ppi or greater, about 1500 ppi or greater, about 2000 ppi or greater, about 2500 ppi or greater, about 3000 ppi or greater, about 3500 ppi or greater, about 4000 ppi or greater, about 4500 ppi or greater, about 5000 ppi or greater, or greater. In further embodiments, increasing the pixel density of the display component does not result in a decrease in the brightness of the displayed image produced by the display component. In embodiments, the brightness of the image may be characterized as about 100 nits or greater, about 250 nits or greater, about 500 nits or greater, about 750 nits or greater, about 1000 nits or greater, about 2500 nits or greater, or greater. In still further embodiments, the pixel structure of the present technology may be characterized by an optical density of about 0.5 or greater, about 0.75 or greater, about 0.8 or greater, about 0.9 or greater, about 0.95 or greater, about 0.99 or greater, or greater.

[0037] While several embodiments have been described, those skilled in the art will recognize that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Moreover, certain well-known processes and elements have not been described to avoid unnecessarily obscuring the invention. Therefore, the above description should not be construed as limiting the scope of the invention.

[0038] Where a range of values ​​is provided, unless the context clearly dictates otherwise, it is understood that each intervening value between the upper and lower limits of that range is also specifically disclosed, to the tenth of the unit of the lower limit. Each smaller range between any stated or intervening value within a stated range and any other stated or intervening value within that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded within the range, and each range including either limit, neither limit, or both limits is also encompassed within the invention, subject to any specifically excluded limits within the stated range. When a stated range includes one or both limits, ranges excluding either or both of those included limits are also included.

[0039] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to "a process" includes a plurality of such processes, a reference to "the pixel structure" includes a reference to one or more pixel structures and equivalents thereof known to those skilled in the art, and so on.

[0040] Additionally, the words "comprise," "comprising," "include," "including," and "includes," when used in this specification and the claims that follow, are intended to specify the presence of stated features, integers, components, or steps, but do not exclude the presence or addition of one or more other features, integers, components, steps, operations, or groups.

Claims

1. 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, the first bandpass filter operable to transmit ultraviolet light; a second bandpass filter positioned on an opposite side of the photoluminescent region from the first bandpass filter, the second bandpass filter operable to transmit visible light; and A pixel structure comprising:

2. 2. The pixel structure of claim 1, wherein the photoluminescent region includes a first side adjacent to the first bandpass filter and a second side adjacent to the second bandpass filter, the second side of the photoluminescent region being wider than the first side.

3. 3. The pixel structure of claim 2, wherein the photoluminescent region further comprises a first sidewall in contact with the first bandpass filter, the first sidewall and the first bandpass filter being characterized by a slope angle greater than 90 degrees.

4. The pixel structure of claim 1 , further comprising a microlens structure, wherein the second bandpass filter is disposed between the microlens structure and the photoluminescent region.

5. The pixel structure of claim 1 , further comprising a protection region disposed between the light emitting diode structure and the first bandpass filter.

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

7. 3. The pixel structure of claim 2, wherein the photoluminescent region is characterized by a depth between the first side and the second side of about 1 [mu]m or greater.

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

9. a light emitting diode structure operable to generate ultraviolet light; a photoluminescent region disposed over the light emitting diode structure, the photoluminescent region characterized by a depth between a first side and a second side of the photoluminescent region, the first side of the photoluminescent region being shorter than the second side; A pixel structure comprising:

10. 10. The pixel structure of claim 9, wherein the photoluminescent region includes a third side including a sidewall region between the first side and the second side of the photoluminescent region, and wherein a slope angle between the first side and the third side is greater than 90°.

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

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

13. the first side is adjacent to a short bandpass filter disposed between the light emitting diode structure and the photoluminescent region, the short bandpass filter operable to transmit ultraviolet light; 10. The pixel structure of claim 9, wherein the second side is adjacent to a long bandpass filter positioned on an opposite side of the photoluminescent region from the short bandpass filter, the long bandpass filter operable to transmit visible light.

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

15. A plurality of pixel structures, each of the pixel structures 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 light emitting diode structure and the photoluminescent region, the first bandpass filter operable to transmit ultraviolet light; a second bandpass filter positioned on an opposite side of the photoluminescent region from the first bandpass filter, the second bandpass filter operable to transmit visible light; and 1. A display component comprising a plurality of pixel structures comprising:

16. 16. The display component of claim 15, wherein the pixel structure further comprises a first side of the photoluminescent region adjacent the first bandpass filter and a second side of the photoluminescent region adjacent the second bandpass filter, the second side being wider than the first side, the photoluminescent region further comprising a first sidewall in contact with the first bandpass filter, and wherein the first sidewall and the first bandpass filter are characterized by a slope angle greater than 90°.

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

18. 16. The display component of claim 15 characterized by a pixel density of greater than or equal to about 3000 pixels per inch.

19. 16. The display component of claim 15 characterized by an optical density of about 1 or greater.

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

Images