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 and priority of U.S. Provisional Patent Application No. 63 / 406,937, filed on September 15, 2023, entitled "LIGHT EMITTING DIODE WITH INCREASED LIGHT CONVERSION EFFICIENCY", which is hereby incorporated by reference in its entirety.

[0002] This technology relates to a display having a pixel structure that combines a light - emitting diode (LED) structure and a photoluminescence region containing a photoluminescent material. Exemplary photoluminescent materials include quantum dots.

Background Art

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

[0004] Therefore, there is a need for a pixel design that generates a brighter image for display devices that include excitable light - emitting materials. These and other needs are addressed by the present technology.

[0005] A further understanding of the nature and merits of the present invention can be achieved by reference to the remainder of this specification and the drawings, in which similar reference numbers are used to refer to similar components throughout several drawings. In some examples, a sublabel is associated with the reference number, followed by a hyphen, to indicate one of several similar components. When a reference number is referred to without specifying an existing sublabel, it is intended to refer to all such several similar components. [Brief explanation of the drawing]

[0006] [Figure 1] This flowchart illustrates selected operations of an exemplary method for manufacturing a pixel structure according to an embodiment of this technology. [Figure 2] This is a simplified cross-sectional view of an exemplary single-pixel structure according to an embodiment of this technology. [Figure 3] This is a simplified cross-sectional view of an exemplary RGB pixel structure according to an embodiment of this technology. [Figure 4A] This is a graph of an exemplary first bandpass filter according to an embodiment of this technology. [Figure 4B] This is a graph of an exemplary second band-pass filter according to an embodiment of this technology. [Overview of the project]

[0007] Embodiments of this technology include 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 band-pass filter positioned between the light-emitting diode structure and the photoluminescent region, the first band-pass filter being operable to transmit ultraviolet light. The pixel structure further includes a second band-pass filter positioned on the opposite side of the photoluminescent region from the first band-pass filter, the second band-pass filter being operable to transmit visible light.

[0008] In additional embodiments, the photoluminescent region of the pixel structure may include a first side adjacent to a first band-pass filter and a second side adjacent to a second band-pass 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 band-pass filter, wherein the first sidewall and the first band-pass filter are characterized by an inclination angle greater than 90°. In even further embodiments, the pixel structure may include a microlens structure, and the second band-pass filter is positioned between the microlens structure and the photoluminescent region. In yet another embodiment, the pixel structure may include a protective region positioned between the light-emitting diode structure and the first band-pass filter. In even further embodiments, the photoluminescent material of the photoluminescent region of the pixel structure may include a quantum dot material capable of absorbing light of a first wavelength from the light-emitting diode structure and emitting light of a second wavelength longer than the first wavelength. In yet another embodiment, the photoluminescent region is characterized by a depth of approximately 1 μm or more between the first and second sides. In yet another embodiment, the first side of the photoluminescent region is characterized by a width of approximately 30 μm or less across the photoluminescent region.

[0009] An additional embodiment of the technology includes an additional pixel structure. The pixel structure includes a light-emitting diode structure capable of generating ultraviolet light and a photoluminescent region disposed on the light-emitting diode structure. The photoluminescent region is characterized by the depth between a first side and a second side of the photoluminescent region, where the first side of the photoluminescent region is shorter than the second side.

[0010] In further embodiments, the photoluminescent region of the pixel structure includes a third side surface, which includes a sidewall region between the first and second sides of the photoluminescent region, and the inclination angle between the first and third sides is greater than 90°. In further embodiments, the first side surface of the photoluminescent region is characterized by a width of about 4 μm or less. In additional embodiments, the first side surface of the photoluminescent region is adjacent to a short-pass filter positioned between the light-emitting diode structure and the photoluminescent region, and the short-pass filter is operable to transmit ultraviolet light, and the second side surface of the photoluminescent region is adjacent to a long-pass filter positioned on the opposite side of the photoluminescent region, and the long-pass filter is operable to transmit visible light. In additional embodiments, the photoluminescent region of the pixel structure may include a photoluminescent material comprising 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. The display component has 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 structure further includes 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 structure further includes a second band-pass filter located on the opposite side of the photoluminescent region from the first band-pass filter, the second band-pass filter operable to transmit visible light.

[0012] In further embodiments, the pixel structure further includes a first side of a photoluminescent region adjacent to a first band-pass filter and a second side of a photoluminescent region adjacent to a second band-pass filter, wherein the second side is wider than the first side, and the photoluminescent region further includes a first sidewall in contact with the first band-pass filter, wherein the first sidewall and the first band-pass filter are characterized by an inclination angle greater than 90°. In yet another embodiment, the photoluminescent material within the photoluminescent region of the pixel structure includes a quantum dot material capable of absorbing light of a first wavelength from a light-emitting diode structure and emitting light of a second wavelength shorter than the first wavelength, wherein the light-emitting diode structure is a microlight-emitting diode structure. In further embodiments, the display component is characterized by a pixel density of about 3000 pixels / inch (ppi) or more. In yet another embodiment, the display component is characterized by an optical density of about 1 or more. In additional embodiments, the display components are operable to be incorporated into an augmented reality display device.

[0013] This 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-band-pass filter between the UV-generating light-emitting diode structure and the bottom of the photoluminescent region, and a long-band-pass filter above the photoluminescent region. Also, in many conventional designs, the side walls are formed at right angles (i.e., at a 90° inclination angle) to the top and bottom surfaces of the photoluminescent region. These design characteristics reduce the proportion of visible light generated in the photoluminescent region that contributes to the displayed image. In embodiments of this technology, a short-band-pass filter is placed 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 output it to the displayed image. Further embodiments of this technology include a long-band-pass filter placed above the photoluminescent region, which reflects UV light back into the photoluminescent region while simultaneously allowing visible light to pass into the displayed image. Another embodiment of this technology involves widening the top surface of a photoluminescent region that is adjacent to the light-emitting diode structure, relative to the bottom surface of the photoluminescent region, so that visible light passes through to form a display image. By widening the top surface relative to the bottom surface of the photoluminescent region, more visible light can be passed through to the image compared to a conventional photoluminescent region where the top and bottom surfaces have the same width. These and other embodiments, along with many of their advantages and features, will be described in more detail below in conjunction with the accompanying drawings. [Modes for carrying out the invention]

[0014] Technological advancements in 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 from layers of semiconductor materials, such as indium gallium nitride (InGaN), which can be configured to emit light of a specific peak emission wavelength when excited by an applied electric field. Semiconductor manufacturing processes are used to create μLEDs with a maximum dimension of approximately 50 μm or less that can operate to emit red, green, or blue light. Quantum dots are nanometer-sized particles of inorganic material that can emit light of a specific color after being excited by higher-energy light. The color of the emitted light may depend on one or more properties of the particle, including size, shape, and composition, among other properties. In the case of quantum dots made from inorganic semiconductor materials, the color of the emitted light is determined by the energy gap between the conduction band and 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 excited electrons return 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 shifts to red; the wider the energy gap, the more the emitted light shifts to blue. By tuning one or more properties of a quantum dot that vary the energy gap between the conduction band and the valence band, quantum dots that emit virtually all colors of light in the visible spectrum can be fabricated.

[0015] Further advancements have led to the combination of μLEDs and quantum dots in high-resolution displays. μLEDs are individually switched on and off by the electronics of the backplane control panel, generating light to photoexcite quantum dots. Higher-energy μLED light sources, such as blue or ultraviolet light, excite the quantum dots, causing them to emit specific, lower-energy colored light, such as blue, green, orange, or red. Excited quantum dots can emit light with improved emission characteristics, such as a narrower full-width at half maximum wavelength spectrum, compared to μLEDs. Because quantum dots can emit light of sharper colors, the number of color filters and polarizers required in the display to prevent unwanted colored light from polluting the displayed image is reduced.

[0016] Unfortunately, quantum dots emit visible light uniformly in all directions (i.e., they emit light isotropically). As a result, a significant portion of the emitted light deviates from the imaging direction in which the light is captured in the displayed image. If the width of the photoluminescent region decreases faster than its depth to increase the pixel density of the display component, the proportion of light emitted from the quantum dot that deviates from the imaging direction increases. Consequently, a trade-off may exist between increased pixel density and decreased 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 heat dissipation. For device components placed close to the viewer's eyes, such as virtual and augmented reality wearable devices, increased heat can make the device uncomfortable or unwearable.

[0017] This technology addresses the problems associated with the design of conventional stacked LED and luminescent material structures, such as the loss of too much light due to emission in unproductive directions. In embodiments, the technology includes a pixel structure having a first band-pass filter positioned 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 band-pass filter is operable to transmit ultraviolet light but block visible light. In embodiments, this first band-pass filter may be referred to as a short-band-pass filter. In further embodiments, the first band-pass filter can function as both a window for transmitting UV light emitted from the light-emitting diode structure and a reflector for reflecting back visible light emitted in unproductive directions from the photoluminescent material contained in the photoluminescent region to the photoluminescent region. The first band-pass filter facilitates the 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 that travels in the image display direction. In embodiments, the technology also includes a pixel structure having a second band-pass filter positioned opposite a first band-pass filter in a photoluminescent region. The second band-pass filter is operable to transmit visible light but block ultraviolet light. In additional embodiments, the second band-pass filter can function both as a window for transmitting visible light emitted from the photoluminescent region to the display image and as a reflector for reflecting back UV light that was not absorbed in the previous pass back to the photoluminescent region. In embodiments, the technology still includes photoluminescent regions in which a first side adjacent to the first band-pass filter is wider than a second side adjacent to the second band-pass filter. The wider first side of the photoluminescent region than the second side creates an inclination angle greater than 90°, rather than a right angle, between the sidewall and the second side. The structure can also facilitate more visible light from the photoluminescent region of the pixel structure toward the display image.

[0018] Figure 1 shows a flowchart with selected operations in Method 100 for manufacturing pixels according to embodiments of the present art. Method 100 may or may not include one or more pre-initiation operations, 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 the methods according to the present art. Method 100 describes operations for forming embodiments of pixel structures, one of which is shown in a simplified schematic form as a single pixel structure 200 in Figure 2, and the other as an RGB pixel structure 300 in Figure 3. The cross-sectional views of the pixel structures 200 and 300 in Figures 2 and 3 are split-unfolded cross-sectional views showing the pixel structure cut between a pair of first and second subpixels to reveal the linear arrangement of the cross-sections of the red, green, and blue pixels. Figures 2 and 3 show only partial schematic diagrams with limited detail. In further embodiments not shown, the exemplary pixel structure may include additional layers, regions, and materials having the embodiments shown, as well as alternative structural and material embodiments from which benefits can still be obtained from any embodiment of the present technology.

[0019] Method 100 includes the step in operation 105 of forming an LED structure 210 on a substrate 202. In 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 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 that electronically communicates 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 below. In the embodiment of the pixel structure 200 shown in Figure 2, the LED structure 210 formed on the substrate 202 is operable to emit ultraviolet (UV) light.

[0020] In some embodiments, the LED structure 210 may be an LED structure containing gallium and nitrogen. 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 yet 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 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 passing 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 passing through the p-type doped GaN layer. The N-pad contact and the P-pad contact may be connected to a conductive layer within the LED subpixel, or they may be directly connected to a contact of the control circuit on the backplane. In one embodiment, 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 this structure. In an additional embodiment, the MQW region is formed 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 one embodiment, the peak intensity wavelength of the light emitted from the MQW region may be an ultraviolet wavelength (e.g., a wavelength of light of about 400 nm or less).

[0021] Method 100 may further include the step of bringing the LED structure 210 into contact with a backplane (not shown) in operation 115. In an embodiment, the backplane may include contacts formed in a semiconductor layer corresponding to the LED structure 210. In an embodiment, the contacts may be made from a conductive material such as copper, aluminum, gold, tungsten, chromium, or nickel, among other conductive materials. In a further embodiment, the LED structure 210 may be placed between one or more transparent conductive layers that form part of the electrical conduction path between the LED structure and the contacts of the backplane. In an additional embodiment, the transparent conductive layers may be made from indium tin oxide or indium zinc oxide, among other transparent conductive materials. In yet another embodiment, a mirror layer (not shown) may be placed adjacent to one or more transparent electrical layers to reflect the light emitted by the LED structure 210 toward the photoluminescent region 216. In a further embodiment, the mirror layer may be made from one or more reflective metals such as copper, aluminum, chromium, silver, platinum, or molybdenum, among other reflective metals. In further embodiments, a conductive bonding layer (not shown) that bonds the LED substrate 202 to the backplane may be placed between the mirror layer and the backplane. In further embodiments, the conductive bonding layer may be made from one or more conductive materials, among other conductive materials, such as tin, gold, or indium.

[0022] In an embodiment, a protective layer 212 may be formed on the LED structure 210. In an additional embodiment, 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 pass through the first bandpass filter 214 and transmit to the photoluminescence region 216. In a further embodiment, 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 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 between the LED structure 210 and the first bandpass filter 214.

[0023] Method 100 can further include, in operation 120, forming a first bandpass filter 214 within the pixel structure 200. In an embodiment, the first bandpass filter may be disposed between the LED structure 210 and the photoluminescence 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 a wavelength of approximately below the UV wavelength compared to the visible wavelength. 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, about 90% or more of ultraviolet light. In an additional embodiment, 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.

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

[0025] Method 100 can also include, in operation 125, forming a photoluminescence region 216 in pixel structure 200. In an embodiment, photoluminescence region 216 can include one or more photoluminescence materials 218, such as quantum dots, operable to absorb light emitted from LED structure 210 and emit light having specific color characteristics. In an embodiment, photoluminescence region 216 may be partially formed from pixel isolation structures 220a-b. In a further embodiment, pixel isolation structures 220a-b reduce crosstalk generated by light from adjacent pixel structures and nearby pixel structures. In an embodiment, the reduction in the 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 greater.

[0026] In further embodiments, the pixel isolation structures 220a-b may extend above and around the LED structure 210. In yet another embodiment, the sub-pixel isolation structures may extend adjacent to and below the contact region of the LED structure 210, and may further extend to the backplane of the pixel structure. In further embodiments, the sub-pixel isolation structures 220a-b may include a core row of pixel isolation material covered by one or more additional material layers, such as a layer of reflective material such as aluminum or copper. In embodiments, the material of the core row may include metallic or dielectric materials, among other types of materials. In further embodiments, the metallic material may include one or more of silicon, tungsten, copper, and aluminum, among other metals. In yet another embodiment, the dielectric material may include one or more of silicon oxide, silicon nitride, silicon carbide, photoresist materials, or dielectric organic polymer materials, among other dielectric materials. In further embodiments, the pixel separation structures 220a to b may have a height of approximately 2.5 μm or more, approximately 5 μm or more, approximately 7.5 μm or more, approximately 10 μm or more, approximately 12.5 μm or more, approximately 15 μm or more, approximately 17.5 μm or more, approximately 20 μm or more, or greater. In even further embodiments, the pixel separation structures 220a to b may have a width of approximately 5 μm or less, approximately 4.5 μm or less, approximately 4 μm or less, approximately 3.5 μm or less, approximately 3 μm or less, approximately 2.5 μm or less, approximately 2 μm or less, or less. In even further embodiments, the pixel separation structures 220a to b may have a height-to-width aspect ratio of approximately 1.5:1 or more, approximately 2:1 or more, approximately 2.5:1 or more, approximately 3:1 or more, approximately 3.5:1 or more, approximately 4:1 or more, approximately 4.5:1 or more, approximately 5:1 or more, or greater. In the embodiment shown in Figure 2, the pixel structure 200 includes pixel separation structures 220a to 220b.

[0027] In the embodiment, the pixel separation structures 220a and 220b form a sidewall of the photoluminescent region 216, including a first side adjacent to the first band-pass filter 214 and a second side opposite to the first side and adjacent to the second band-pass filter 222. In a further embodiment, the first width of the first side extending between the pixel separation structure 220a and 220b is smaller than the second width of the second side extending between the same pixel separation structures 220a and 220b. In an additional embodiment, 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 surface and the second width of the second side surface of the photoluminescent region 216 creates an inclination angle (α) greater than 90° (i.e., not a right angle) between the pixel separation structure 220b and the first side surface. In embodiments, the inclination angle (α) may be characterized as an inclination angle 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 than these. Because the width of the second side surface of the photoluminescent region 216 adjacent to the second bandpass filter 222 is wide, the area over which visible light leaves the photoluminescent region and is captured in the display image is increased.

[0028] Method 100 further includes the step in operation 130 of depositing a photoluminescent material 218 onto a photoluminescent region 216 of a pixel structure 200. In embodiments, the as-deposited photoluminescent material may include one or more photoluminescent precursors in a mixture or slurry containing a photocurable fluid and one or more photoluminescent particles or compounds. In further embodiments, one or more photoluminescent compounds may include quantum dot materials capable of emitting light having specific color properties when excited by light from a light source. 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 photocurable fluid may include one or more crosslinkable compounds, photoinitiators, and color converters. In additional embodiments, the crosslinkable 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 may include a negative-type photoresist material such as SU-8 photoresist. In yet another embodiment, the photoinitiator may include phosphine oxide compounds and keto compounds, among other types of photoinitiator compounds, which generate radicals that initiate curing of unsaturated compounds when excited by ultraviolet light. Commercially available photoinitiator compounds include, among other photoinitiators, Irgacure 184, Irgacure 819, Darocur 1173, Darocur 4265, Darocur TPO, Omnicat 250, and Omnicat 550.

[0029] If the deposited photoluminescent material contains one or more photoluminescent precursors, the precursors can be cured to form the photoluminescent material 218. In embodiments, the curing operation may include exposing the photoluminescent precursors in the photoluminescent region 216 to 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 short enough to activate one or more photocurable compounds in the photocurable fluid of the photoluminescent precursor. In yet another embodiment, the curing light may be characterized by a peak emission wavelength of approximately 405 nm or less, approximately 400 nm or less, approximately 395 nm or less, approximately 390 nm or less, approximately 385 nm or less, approximately 380 nm or less, approximately 375 nm or less, approximately 370 nm or less, approximately 365 nm or less, approximately 360 nm or less, approximately 355 nm or less, approximately 350 nm or less, approximately 340 nm or less, approximately 330 nm or less, approximately 320 nm or less, approximately 310 nm or less, approximately 300 nm or less, or below. In yet another embodiment, the curing light may be supplied by an LED structure 210. In these embodiments, supplying the curing light from the LED structure 210 may enable self-alignment between the photoluminescent material 218 in the photoluminescent region 216 and the LED structure 210. Self-alignment between the photoluminescent material and the LED structure becomes increasingly beneficial as the subpixel size decreases and the pixel density increases.

[0030] Method 100 may further include the step of forming a second band-pass filter 222 within the pixel structure 200 in operation 135. In embodiments, the second band-pass filter 222 may be positioned between the photoluminescent region 216 and the microlens 224. In additional embodiments, the second band-pass filter 222 may be formed on the photoluminescent region 216, or on a UV filter (not shown) if present. In further embodiments, the second band-pass filter 222 may be characterized as a long band-pass filter capable of transmitting a larger proportion of light having wavelengths in the visible wavelength region compared to shorter UV wavelengths. In yet another embodiment, the second band-pass filter 222 may be capable of transmitting more than 50%, about 60%, about 70%, about 80%, or about 90% 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 ultraviolet light.

[0031] Figure 4B shows an exemplary optical reflectance and transmittance profile of one embodiment of the second band-pass filter 222. The profile shows that light with wavelengths significantly longer than 400 nm is transmitted through the filter to the microlens 224 and the displayed image, while light with wavelengths significantly shorter than 400 nm is reflected toward the photoluminescent region 216. In additional embodiments, the transmission profile of the second band-pass filter 222 may have 50% transmittance / reflection wavelengths shorter or longer than 400 nm. In these embodiments, light with wavelengths significantly longer than the 50% transmittance / reflection wavelength is transmitted through the filter to the microlens 224, while light with wavelengths significantly shorter than the 50% transmittance / reflection wavelength is reflected toward the photoluminescent region 216. In additional embodiments, the second band-pass filter 222 may be characterized by 50% transmittance / reflection wavelengths less than 400 nm, about 390 nm or less, about 380 nm or less, about 370 nm or less, or below. In further embodiments, the second bandpass filter 222 may be characterized by a 50% transmit / reflect wavelength greater than 400 nm, about 410 nm or greater, about 420 nm or greater, about 430 nm or greater, or higher. From the viewpoint of the photoluminescent region 216, shorter wavelength UV light traveling in the direction of the microlens 224 is reflected back to the photoluminescent region. This causes a greater proportion 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 some embodiments, the second band-pass filter 222 functions as a UV filter that prevents UV light from exiting the photoluminescent region towards the displayed image. In additional embodiments, a UV filter (not shown) can be placed adjacent to the second band-pass filter 222 to attenuate or block further 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 within 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 yet another embodiment, the UV filter may be made from an organic polymer such as polyacrylate, polymethyl methacrylate, and a copolymer of polyacrylate and polymethyl methacrylate. In yet another embodiment, the UV filter may be made from a commercially available material such as Tinuvin CarboProtect from BASF and the Eversorb series from Everlight. In embodiments, the UV filter can reduce the proportion 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 visible light from the pixel structure by 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.

[0033] Method 100 also includes the step in operation 140 of forming a microlens 224 on the pixel structure 200. In embodiments, the microlens 224 may be positioned adjacent to a second band-pass filter 222 and, if present, a 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 microlens 224 bends and focuses the light emitted by the pixel structure, improving the image quality from display components for devices such as VR headsets and AR glasses, among other devices. In the embodiment shown in Figure 2, the pixel structure 200 includes the microlens 224.

[0034] Referring now to Figure 3, another pixel structure 300 according to an embodiment of the present technology is shown. The pixel structure 300 includes three sub-pixel structures 302a-c having photoluminescent materials 318a-c that are operable to emit light of red, green, and blue wavelengths, respectively. In the embodiment, the formation of the photoluminescent materials 318a-c in the photoluminescent regions 316a-c may include sequential operations to form a photoluminescent material 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 sequential operation may include the steps of forming a first photoluminescent material 318a containing a red-emitting quantum dot in a first photoluminescent region 316a of the pixel structure 300, forming a second photoluminescent material 318b containing a green-emitting quantum dot in a second photoluminescent region 316b of the pixel structure, and forming a third photoluminescent material 318c containing a blue-emitting quantum dot in a third photoluminescent region 316c of the pixel structure. In further embodiments, a fourth sub-pixel structure (not shown) may be included in the pixel structure 300. The fourth sub-pixel may not contain a photoluminescent material unless one of the other sub-pixel structures 302a to c cannot be adequately illuminated.

[0035] In some embodiments, the 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 other display devices, such as a headset, glasses, screen, or monitor. In even further embodiments, the display component including the pixel structure may be incorporated into a display device for virtual reality and / or augmented reality services.

[0036] In further embodiments, the display component incorporating the pixel structure may be characterized by a pixel density of approximately 500 pixels / inch (ppi) or more, approximately 1000 ppi or more, approximately 1500 ppi or more, approximately 2000 ppi or more, approximately 2500 ppi or more, approximately 3000 ppi or more, approximately 3500 ppi or more, approximately 4000 ppi or more, approximately 4500 ppi or more, approximately 5000 ppi or more, or higher. In further embodiments, an increase in 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 approximately 100 nits or more, approximately 250 nits or more, approximately 500 nits or more, approximately 750 nits or more, approximately 1000 nits or more, approximately 2500 nits or more, or higher. In further embodiments, the pixel structure of the present technology may be characterized by an optical density of approximately 0.5 or more, approximately 0.75 or more, approximately 0.8 or more, approximately 0.9 or more, approximately 0.95 or more, approximately 0.99 or more, or higher.

[0037] While several embodiments have been described, those skilled in the art will recognize that various modifications, alternative configurations, and equivalents can be used without departing from the spirit of the invention. Furthermore, some well-known processes and elements have not been described in order 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, it should be understood that, unless the context explicitly indicates otherwise, each intermediate value between the upper and lower limits of that range is also specifically disclosed to the tenth of a unit of the lower limit. Any smaller range between any stated value or intermediate value within the stated range and any other stated value or intermediate value within that stated range is included. The upper and lower limits of these smaller ranges may independently be included in or excluded from that range, and each range that includes either limit, does not include either limit, or includes both limits is included in the invention, subject to any specifically excluded limits within the stated range. Where a stated range includes one or both limits, ranges that exclude either or both of the limits they include are also included.

[0039] As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include multiple referents unless otherwise explicitly indicated by the context. For example, a reference to “a process” includes multiple such processes, and a reference to “the pixel structure” includes one or more pixel structures and their equivalents known to those skilled in the art.

[0040] Furthermore, the words “comprise,” “comprising,” “include,” “including,” and “includes,” as used herein and in the following claims, are intended to specify the presence of the described feature, integer, component, or step, but do not preclude the presence or addition of one or more other features, integers, components, steps, actions, or groups.

Claims

1. A light-emitting diode structure capable of operating to generate ultraviolet light, A photoluminescent region containing photoluminescent material, A first band-pass filter disposed between the light-emitting diode structure and the photoluminescence region, the first band-pass filter being operable to transmit ultraviolet light, A second band-pass filter positioned on the opposite side of the first band-pass filter in the photoluminescence region, the second band-pass filter being capable of transmitting visible light, Microlens structure, Equipped with, The second band-pass filter is positioned between the microlens structure and the photoluminescent region. The photoluminescent region includes a first side adjacent to the first band-pass filter and a second side adjacent to the second band-pass filter, wherein the second side of the photoluminescent region is wider than the first side. The photoluminescent region further includes a first sidewall in contact with the first band-pass filter, and the first sidewall and the first band-pass filter are characterized by an inclination angle greater than 90°. The photoluminescent region is characterized by a depth of approximately 1 μm or more between the first side surface and the second side surface. A pixel structure in which the first side is further characterized by a width of approximately 30 μm or less that crosses the photoluminescent region.

2. The pixel structure according to claim 1, further comprising a protective region disposed between the light-emitting diode structure and the first band-pass filter.

3. The pixel structure according to claim 1, wherein the photoluminescent material in the photoluminescent region includes a quantum dot material that is 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.

4. A light-emitting diode structure capable of operating to generate ultraviolet light, A photoluminescent region disposed on the light-emitting diode structure, wherein the photoluminescent region is characterized by the depth between a first side surface and a second side surface of the photoluminescent region, and the first side surface of the photoluminescent region is shorter than the second side surface, Equipped with, The photoluminescent region includes a third side surface between the first side surface and the second side surface of the photoluminescent region, and the inclination angle between the first side surface and the third side surface exceeds 90°. The first side surface is characterized by a width of approximately 4 μm or less. The first side is adjacent to a short-band-pass filter disposed between the light-emitting diode structure and the photoluminescence region, and the short-band-pass filter is operable to transmit ultraviolet light. A pixel structure in which the second side is adjacent to a long-band-pass filter located on the opposite side of the photoluminescence region from the short-band-pass filter, and the long-band-pass filter is operable to transmit visible light.

5. The pixel structure according to claim 4, wherein the photoluminescent region comprises a photoluminescent material including a quantum dot material capable of absorbing light of a first wavelength from the light-emitting diode structure and emitting light of a second wavelength longer than the first wavelength.

6. A display component comprising multiple pixel structures, wherein each of the pixel structures is A light-emitting diode structure capable of operating to generate ultraviolet light, A photoluminescent region containing photoluminescent material, A first band-pass filter disposed between the light-emitting diode structure and the photoluminescence region, the first band-pass filter being operable to transmit ultraviolet light, A second band-pass filter positioned on the opposite side of the first band-pass filter in the photoluminescence region, the second band-pass filter being capable of transmitting visible light, Equipped with, Each of the pixel structures further includes a first side surface of the photoluminescence region adjacent to the first band-pass filter and a second side surface of the photoluminescence region adjacent to the second band-pass filter, wherein the second side surface is wider than the first side surface, and the photoluminescence region further includes a first side wall in contact with the first band-pass filter, and the first side wall and the first band-pass filter are characterized by an inclination angle greater than 90°. In each of the pixel structures, the photoluminescent material in the photoluminescent region includes a quantum dot material capable of absorbing light of a first wavelength from the light-emitting diode structure and emitting light of a second wavelength longer than the first wavelength, wherein the light-emitting diode structure is a microlight-emitting diode structure. The aforementioned display component is characterized by a pixel density of approximately 3,000 pixels / inch or more.

7. The display component according to claim 6, characterized by an optical density of approximately 1 or more.

8. The display component according to claim 6, which is operable to be incorporated into an augmented reality display device.

Images