Micro-led display with reduced motion blur and improved operating lifetime

Abstract

Embodiments of the present disclosure relate to μLED displays. The μLED display includes a backplane and backplane circuitry having pixel circuits for generating a pulse amplitude modulated driving current having a low duty ratio. An array of μLED dies is formed on the backplane and electrically integrated with the backplane circuitry. The μLED dies are controlled by the PAM driving current generated by the pixel circuits. A plurality of structures is coupled to the array of μLED dies and defines wells of a plurality of subpixels. A first color conversion layer is disposed in wells of first color subpixels of the plurality of subpixels, and a second color conversion layer disposed in wells of second color subpixels of the plurality of subpixels. The first and second color conversion layers convert excitation light emitted by μLED dies to emission light of a first and second color, respectively.

Description

MICRO-LED DISPLAY WITH REDUCED MOTION BLUR AND IMPROVED OPERATING LIFETIMEBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to display devices, and more specifically to micro-LED displays for use with near-eye display systems in augmented and virtual reality applications.Description of the Related Art

[0002] In the past few years, organic LED (OLED) displays have gained momentum and have competed fiercely with LCDs in TVs and smartphones because of their superior unprecedented dark state, thin profile, and freeform factor. However, issues such as bum in and device operating lifetimes still need to be improved for OLED displays. Micro-LED (pLED) displays based on lll-V semiconductor technology have been identified as the next-generation display technology to replace traditional thin-film transistor liquid crystal displays (TFT-LCD) and OLED displays.

[0003] Micro-LED displays have attracted increased attention, particularly for emerging applications where a viewer sees the display at very close range (e.g., less than or about three inches) such as in near-eye display systems. Micro-LEDs have the ability to use very low power while providing high performance (e.g., produce infinite contrast and high color gamut with low response times). Further, pLEDs can enable very high resolutions, are not susceptible to bum in, and have very simple process flows in manufacturing, thereby enabling a low cost of production while allowing device manufacturers to incorporate very thin displays in devices where thickness real estate is crucial (as no backlight or polarizer is needed). Micro-LED displays would have a variety of advantages as compared to OLED displays e.g., higher energy efficiency, brightness and operating lifetime, as well as fewer material layers in the display stack, which can simplify manufacturing. As such, pLED displays can be particularly attractive for displays used in virtual reality headsets and augmented reality glasses.

[0004] Unfortunately, challenges remain in the development of optical displays that utilize LEDs in near-eye display systems where a viewer sees the display at very close range (e.g., less than or about three inches). Conventional OLED displays used innear-eye display systems currently still cause motion blur and have limited usage and operating lifetimes.

[0005] Thus, there is a need in the art for improved optical displays for use with near-eye display systems that suppress motion blur without degrading or adversely impacting device lifetime.SUMMARY

[0006] In one embodiment, an optical display is provided. The optical display includes a backplane and backplane circuitry disposed in the backplane. The backplane circuitry includes pixel circuits for generating a pulse amplitude modulated (PAM) driving current having a constant duty ratio of less than 20%. The display also includes an array of pLED dies formed on the backplane and electrically integrated with the backplane circuitry in which the array of pLED dies is controlled by the PAM driving current generated by the pixel circuits, and a plurality of structures coupled to the array of pLED dies. The plurality of structures defines wells of a plurality of subpixels in which a first color conversion layer is disposed in wells of first color subpixels of the plurality of subpixels. The first color conversion layer converts excitation light emitted by first pLED dies of the array of pLED dies to emission light of a first color. The display also includes a second color conversion layer disposed in wells of second color subpixels of the plurality of subpixels. The second color conversion layer converts excitation light emitted by second pLED dies of the array of pLED dies to emission light of a second color.

[0007] In another embodiment, an optical display is provided. The optical display includes a backplane and a backplane circuitry disposed in the backplane. The backplane circuitry includes pixel circuits for generating a pulse amplitude modulated (PAM) driving current having a constant duty ratio of less than 20%, and an array of pLED dies operable to emit blue light in the visible blue portion of the visible spectrum. The array of pLED dies are formed on the backplane and electrically integrated with the backplane circuitry in which the array of pLED dies is controlled by the PAM driving current generated by the pixel circuits. The optical display also includes a plurality of structures coupled to the array of pLED dies. The plurality of structures define wells of a plurality of subpixels in which a green quantum layer is disposed in wells of green subpixels of the plurality of subpixels and a red quantum layer is disposed in wells ofred subpixels of the plurality of subpixels. The green quantum layer converts blue excitation light emitted by first pLED dies of the array of pLED dies to emission light in the visible green portion of the visible spectrum , and the red quantum layer converts blue excitation light emitted by second pLED dies of the array of pLED dies to emission light in the visible red portion of the visible spectrum. The display also includes third pLED dies of the array of pLED dies disposed in wells of blue subpixels of the plurality of subpixels. The third pLED dies are operable to emit blue emission light in the visible blue portion of the visible spectrum.

[0008] In yet another embodiment, a color conversion array for an optical display is provided. The color conversion array includes a plurality of structures, each structure having a base configured to be coupled to a backplane of the optical display, and a plurality of wells, each of the plurality of wells defined within one or more of the plurality of structures. In an embodiment, the plurality of wells includes first wells of the plurality of wells which are larger than second wells of the plurality of wells, and second wells of the plurality of wells which are larger than third wells of the plurality of wells. The color conversion array also includes a first color conversion layer disposed within first wells of the plurality of wells to convert a first excitation light to emission light of a first color, and a second color conversion layer disposed within second wells of the plurality of wells to convert a second excitation light to emission light of a second color. The first excitation light and the second excitation light are emitted by pLED dies in response to pulse amplitude modulated (PAM) driving currents having a constant duty ratio of less than 20%.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0010] FIG. 1 is a schematic top view of a pLED display integrated with a backplane, according to certain embodiments of the present disclosure;

[0011] FIG. 2 is a top view of an arrangement of pixel structures, according to certain embodiments of the present disclosure;

[0012] FIG. 3 is a cross-sectional view of a pixel structure of FIG. 2, according to certain embodiments of the present disclosure;

[0013] FIG. 4 is a schematic view of an exemplary driver circuit that may be used with the pLED display of FIG. 1 , according to certain embodiments of the present disclosure;

[0014] FIGs.5A and 5B are graphs illustrating exemplary pulse-amplitude modulated signals for driving optical displays, according to certain embodiments of the present disclosure;

[0015] FIGs. 6A and 6B are graphs illustrating the degradation in luminance of subpixels over time, according to certain embodiments of the present disclosure; and

[0016] FIG. 7 is a top view of a pixel structure, according to certain embodiments of the present disclosure.

[0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0018] The following disclosure generally describes display systems for virtual reality and augmented reality. Certain details are set forth in the following description and in the figures to provide a thorough understanding of various implementations of the disclosure. Other details describing well-known structures and systems often associated with display systems for virtual reality and augmented reality are not set forth in the following disclosure to avoid unnecessarily obscuring the description of the various implementations.

[0019] Many of the details, dimensions, angles and other features shown in the Figures are merely illustrative of particular implementations. Accordingly, other implementations can have other details, components, dimensions, angles andfeatures without departing from the spirit or scope of the present disclosure. In addition, further implementations of the disclosure can be practiced without several of the details described below.

[0020] Technological advances in high-resolutions displays include the development of pLEDs from inorganic semiconductor materials and the use of photoluminescent materials like quantum dots in the displays. pLEDs are made of layers of semiconductor materials, such as indium gallium nitride (InGaN), that can be arranged to emit light of a specific peak emission wavelength when excited by an applied electric field. Semiconductor fabrication processes are used to make pLEDs having a longest dimension of less than or about 50 pm and operable to emit red, green, or blue light.

[0021] Quantum dots are nanometer-sized particles of inorganic materials that can emit light of a particular color after being excited by more energetic light. The color of the emitted light may depend on one or more characteristics of the particles, including their size, shape, and composition, among other characteristics. For quantum dots made of inorganic semiconductor materials, the color of the light they emit depends on an energy gap between the conduction band and the valence band of the dots. When the quantum dots are excited, one or more electrons jump from the lower- energy conduction band to the higher-energy valence band. As the excited electrons fall back down to the conduction band, they emit light having a color that depends on the size of the energy gap between the valence band and the conduction band. The narrower the energy gap, the more the emitted light is shifted to the red, while the wider the energy gap, the more the emitted light is shifted to the blue. By adjusting one or more characteristics of the quantum dots that change the energy gap between the conduction and valence bands, quantum dots can be made that emit light of practically any color in the visible spectrum.

[0022] Additional advances have combined pLEDs and quantum dots in a high- resolution display. The pLEDs are independently switched on and off by electronic circuitry in a backplane control panel to generate source light that photoexcites the quantum dots. The more energetic pLED source light, such as blue or ultraviolet light, excites the quantum dots and causes them to emit light of a specific, less-energetic, color such as blue, green, or red light. The excited quantum dots can emit light withimproved emissions characteristics, such as a narrower band full-width-half-maximum wavelength spectrum, than the pLEDs. The ability of the quantum dots to emit a sharper color of light reduces the number of color filters and polarizers needed in a display to block unwanted colors of light from contaminating the displayed images. In many cases, the quantum-dot-containing displays are brighter, higher-contrast, and more energy-efficient than pLED displays that lack quantum dots. The combination of the pLEDs and the quantum dots produces a more energy-efficient high-resolution display with an increased number of pixels per square inch (ppi), and a sharper, more accurate color gamut, among other enhancements.

[0023] Unfortunately, challenges remain in the development of optical displays that utilize LEDs in near-eye display systems where a viewer sees the display at very close range (e.g., less than or about three inches). One challenge is the quality of the image viewed, such as the perceiving of motion blur by the user. Conventionally, the motion picture response time (MPRT) of a display is used to describe the severity of motion blurs and is proportional to the display duty ratio and frame time. It is believed that motion blur viewed on optical displays is caused by the displacement of an image formed on the retina of the user. The duty ratio and frame time of an optical display can therefore directly affect the motion blur perceived by the user. A low duty ratio is one of the techniques used to reduce motion blurs of optical displays. However, such short duty cycle is difficult to achieve for near-eye display systems using OLED or WOLED displays without sacrificing the operating lifetime of the display. For example, for OLED displays to operate at a low duty ratio, for example, at a duty ratio of about 10%, the trade-off will be decreased luminance or brightness of the OLED display. In order to achieve the same pixel luminance, the peak brightness of the OLED pixels would correspondingly need to be substantially increased (e.g., such as by 10x) to compensate for the decreased brightness from the lowered duty ratio. Under such an increased high driving current due to PAM driving in OLED displays, the lifetime of the OLED display is adversely affected which correspondingly may lead to display degradation and shortening of display life. Accordingly, conventional OLED displays have longer duty ratios that often result in motion blur in near-eye display applications.

[0024] In LED displays, the amount of current flowing through an LED die determines the gray level (or brightness) of the individual emitter. The gray level of each individual LED die that composes a pixel therefore contributes to the overallbrightness of the LED display. Conventionally, OLED displays utilize a pulse amplitude modulation (PAM) driving technique to drive the OLEDs in the display. The PAM voltage applied to the pixel results in a current through each of the OLED, thereby determining the gray level of the OLED die. In this approach, a higher current level results in a higher light emission / gray level from each OLED and thus a brighter pixel. But for inorganic pLEDs, changing the current density to vary the gray level also affects the wavelength of the emitted light from the pLEDs which in turn can lead to an undesirable color shift in the emitted light by the pLED. As such, pLED displays typically implement pulse width modulation (PWM) driving techniques modulates the gray level of the pLED by adjusting the emission time (duty cycle) with a constant operation current density.

[0025] In accordance with various embodiment, the present disclosure addresses the problems discussed above by providing an optical display utilizing pLEDs driven by PAM techniques with a fixed low duty ratio, such as a duty ratio of less than 10%. In an embodiment, the optical display system includes a pLED display having an array of individual pLED structures formed thereon. One or more of the pLED structures can be grouped to form a LED pixel. Each of the plurality of pLED structures may include a pLED die and suitable control circuitry configured to generate and distribute control signals to selectively illuminate certain subpixels or pixels of the display system.

[0026] In some embodiments, the control circuitry may comprise a display driver integrated circuit (DDIC), an array of driving transistors and a plurality of pixel circuitry connected thereto for driving the pLED display. The DDIC may receive image data to program and deliver analog voltages to current drivers that control or are utilized to vary the drive current of the pixel circuits connected thereto to activate and control the pixels within the pLED display. In some embodiments, the pixel circuits drive the pLEDs with PAM driving techniques, and as such, the brightness of each pixel may be proportional to the amount of current flowing through the pLEDs. By using a PAM driving technique, changes may be made to the amplitude of the driving pulse to modulate the intensity of the pLEDs. In an embodiment, the DDIC provides data signals to the pixel circuits to drive the pLEDs based on a PAM signal with a low duty ratio to assist in suppressing motion blur by the pLED display. The data signal provided from the DDIC to the pixel circuits determine the amplitude of the drivingpulse delivered to each of the connected pLEDs. In an embodiment, driving the pLEDs using PAM techniques enables reducing the duty ratio of the pLED display to less than 20%, such as a duty ratio less than 10%. In one embodiment, the duty ratio of the pLED display is about 5%. The low duty ratio of the pLED display provides for improved optical characteristics in applications for near-eye display systems, such as reduced motion blurring.

[0027] In another embodiment, which may be combined with other embodiments described herein, color conversion quantum dots are used to in turn compensate for color shift by the pLEDs caused by the varying applied current during PAM driving. Since the emission spectrum from quantum dots are constant, shifts in the excitation spectrum from the pLEDs due to varying current densities do not affect the end emitted spectrum from the pixel. In another embodiment, each of the pixels of the pLED display includes a green subpixel, a red subpixel, and a blue subpixel. As the reliability of quantum dots are generally highly sensitive to the flux of the excitation light absorbed the stresses induced by high flux of light from the pLEDs can typically lead to faster performance decay or device failure. As such, in order to decrease power consumption and improve device operating lifetimes, embodiments of the present disclosure also include varying the size of the emission area and or emitters of each of the respective subpixels based on the highest required emission luminance and / or required current to be applied for each subpixel.

[0028] For example, in an embodiment in which higher currents are needed for the green and blue subpixels, each of the pixels may be configured such that the emitters for each of the green and blue subpixels are larger than the emitter of the red subpixel. In another embodiment in which quantum dots are not used for the blue subpixel, the emission area of the blue subpixel may be smaller than the emission area of the green and red subpixel to maximize green and red quantum dot layers. Maximizing green and red quantum dot layers can provide for improved operating lifetime by minimizing the effects of quantum dot degradation in the green and red subpixels.

[0029] FIG. 1 is a schematic top view of a pLED display 100, according to certain embodiments. The pLED display 100 includes a pLED array 110 integrated with a backplane layer 116 having a backplane circuitry 118, according to certain embodiments of the present disclosure. The pLED array 110 includes a plurality ofpLED dies that may function as a light source or an excitation source for illuminating a plurality of pixel 200 of the pLED display 100. In some embodiments, the pLED array 110 can be on its own substrate with each of the pLED dies coupled to a pixel circuit on the backplane layer 116. The backplane layer 116 may be a silicon substrate in which a CMOS circuitry is formed for the backplane circuitry 118. In some embodiments, the backplane layer 116 may be fabricated using conventional CMOS processes. In some embodiments, the CMOS circuitry of the backplane circuitry 118 may be characterized by fast response times to activate subpixels having a largest dimension of less than or about 10 pm.

[0030] FIG. 2 is a schematic top view of a portion of the pLED array 110 in FIG. 1 depicting an arrangement of pixel structures 201 that include a group of pixels 200, according to certain embodiments. The pixel structures 201 may be part of a larger arrangement of pixel structures that make up at least a portion of a high pixel density optical display. The display may be characterized by a pixel density of greater than or about 1 ,000 ppi, greater than or about 1 ,250 ppi, greater than or about 1 ,500 ppi, greater than or about 1 ,750 ppi, greater than or about 2,000 ppi, greater than or about 2,500 ppi, greater than or about 2,750 ppi, greater than or about 3,000 ppi, or more.

[0031] In the embodiment shown in FIG. 2, the arrangement of pixel structures 201 corresponds to the pixels of the pLED display 100 depicted in FIG. 1 , according to certain embodiments of the present disclosure. In an embodiment, the pLED display 100 is a three-color display in which each pixel 200 includes three subpixels, one for each color, e.g., one each for the blue, green, and red color channels. As such, each pixel 200 of the pLED display 100 includes three pLED dies from the pLED die array 110 for illuminating each of the three subpixels of the pixel 200. In an embodiment, the pixels 200 each include a first pLED die 202 for illuminating a red subpixel 208, a second pLED die 204 for illuminating a green subpixel 210, and a third pLED die 206 for illuminating a blue subpixel 212.

[0032] In the embodiment shown in FIG. 2, the pixels 200 are squared shaped and the subpixels 208, 210, 212 that make up each of the pixels 200 are rectangular and square shaped. It will be appreciated that embodiments of subpixels 208, 210, 212 may have additional shapes, such as parallelogram-shaped, trapezoidal-shaped, pentagonal-shaped, hexagonal-shaped, heptagonal-shaped, octagonal-shaped,nonagonal-shaped, circular-shaped, and elliptical-shaped, among other kinds of shapes. The pixels 200 may also be arranged in additional shapes such as rectangular-shaped, parallelogram-shaped, trapezoidal-shaped, circular-shaped, and elliptical-shaped, among other kinds of shapes.

[0033] Each of the subpixels 208, 210, 212 may be characterized by a longest dimension that is less than or about 15 pm, less than or about 14 pm, less than or about 13 pm, less than or about 12 pm, less than or about 11 pm less than or about 10 pm, less than or about 9 pm, less than or about 8 pm, less than or about 7 pm, less than or about 6 pm, less than or about 5 pm, or less.

[0034] Each of the pixels 200 may be characterized by a longest dimension of less than or about 25 pm, less than or about 22, less than or about 20 pm, less than or about 17 pm, less than or about 15 pm, less than or about 12 pm, less than or about 10 pm, or less.

[0035] In an embodiments, the pLED array 110 is integrated with the backplane circuitry 118 so that each of the pLED dies 202, 204, 206 can be individually and independently activated and controlled, which in turn allows for the backplane circuitry 118 to address and control each of the subpixels of the pLED display 100. In an embodiment, the backplane circuitry 118 comprises a pixel circuit for connecting each pLED die of the pLED display 100 to a column driver 118c via a column address line 118a, and a row driver 118d via a row address line 118b. Each pixel circuit is configured to receive data signal from the DDIC and comprises transistors and capacitors for driving each pixel 200 of the pLED display 100 using the received data signal.

[0036] The pixel 200 also includes subpixel isolation structures 214 disposed between neighboring pLED dies. The isolation structures 214 define a plurality of wells with each of the pLED dies 202, 204, 206 in an individual well defined by the isolation structures 214. As shown in FIG. 2, the pixel 200 includes the first pLED die 202 disposed in a first well 216, the second pLED die 204 disposed in a second well 218, and the third pLED die 206 disposed in a third well 220. The isolation structures 214 can be a photoresist or metal, and can be deposited by conventional lithography processes. The optical density of the isolation structures 214 provides for color isolation between each of the pLED dies and can help prevent color bleeding orcontamination during the light-up operation. As such, each of the plurality of wells may also in turn define a corresponding emission region of each of the red, green, and blue subpixels 208, 210, 212 in the pixel 200.

[0037] In an embodiment, each of the pLED dies 202, 204, 206 are fabricated with the same structure so as to generate the same wavelength range (this can be termed “monochrome” pLEDs). In general, the monochrome pLEDs can generate light in a wavelength range having a peak with a wavelength no greater than the wavelength of the highest-frequency color intended for the display, e.g., purple or blue light. A color conversion layer (e.g., quantum dot layer) is then used to convert this short wavelength light into longer wavelength light, e.g., red or green light for red or green subpixels. If the pLEDs generate UV light, then color conversion layers can be used to convert the UV light into blue light for the blue subpixels. If the pLEDs generate blue light, then no color conversion layer is needed over the pLEDs for the blue subpixel.

[0038] In an embodiment, each of the pLED dies 202, 204, 206 may therefore be a blue pLED die that can generate light in the violet or blue range. For example, in an embodiment, the pLED dies 202, 204, 206 may each be operable to emit blue light having a peak emission wavelength in the visible blue portion of the visible spectrum. In further embodiments, the pLED dies 202, 204, 206 may be operable to emit blue light characterized by a peak emission wavelength of greater than or about 420 nm, greater than or about 430 nm, greater than or about 440 nm, greater than or about 450 nm, greater than or about 460 nm, greater than or about 470 nm, greater than or about 480 nm, greater than or about 490 nm, or more. In another embodiment, each of the pLED dies 202, 204, 206 is a UV pLED die that can generate light in the ultraviolet (UV), e.g., the near ultraviolet, range. For example, the pLED dies 202, 204, 206 can generate light in a range of 365 to 405 nm. Without being bound by theory, it is believed that by using pLED dies that emit blue light as the excitation light source, the third pLED die 206 may be used to directly provide blue light for illuminating the blue subpixel 212 without the need for a color conversion material. This in turn enables the size or emission area for the blue subpixel 212 to be reduced as quantum yield and / or quantum efficiency of a blue quantum dot layer is not a concern.

[0039] In the embodiment of the pixel shown in FIGs. 2 and 3, the pLED dies 202, 204, 206 are operable to emit blue light. Furthermore, it is known that red quantum dots are more stable than green quantum dots and that green quantum dots have lower quantum yield and lower lifetimes than red quantum dot. In some embodiments, due to the lower quantum yield of green quantum dots, the current per subpixel required for achieving white light is about 2x higher for the green subpixel 210 as compared to the red subpixel 208. Accordingly, in some embodiments, the isolation structures 214 for the pixel 200 are formed such that the emission area of the green subpixel 210 is larger than the emission area red and blue subpixels 208, 212, as shown in FIG. 2.

[0040] The emission area of the green subpixel 210 generally corresponds to the size of the green quantum dot layer and the green subpixel as defined by the isolation structures 214 and the corresponding well formed around the pLED die 204. The size of the well corresponds to the size of the green quantum dot layer formed for the respective green subpixel as the green quantum dot layer is supported by the isolation structures 214 when the green quantum dots are printed into each of the wells during fabrication of the green subpixels for the pLED display 100. Without being bound by theory, it is believed that increasing the size of the emission area of the green subpixel 210 (e.g., the size or surface area of the green quantum dot layer) provides for reducing the stress from the second pLED die 204 and the higher current / intensity being applied to the green subpixel, for example to achieve white light, as well as improve the overall efficiency of the green quantum dot layer. Increasing the surface area of the green quantum dot layer may correspondingly increase the amount of LED light injected into the green quantum dot layer resulting in higher power efficiency.

[0041] In some embodiments, a ratio between the emission area of the green subpixel 210 and the ratio of the red subpixel 208 may be about 2. Ox or less, about 2.2x or less, about 2.4x or less, about 2.6x or less, about 2.8x or less, about 3. Ox or less, or more. In an embodiment, the emission area of the green subpixel 210 is about 4.875 pm2and the emission area of the red subpixel 208 is about 2.625 pm2such that the ratio of the emission area of the green subpixel 210 and the red subpixel 208 is about 1 ,86x.

[0042] As mentioned above, in an embodiment in which the pLED die 206 is operable to emit blue light and a color conversion layer is therefore not needed for the blue subpixel 212, the emission area of the blue subpixel 212 may correspondingly also be smaller than the emission area of the red subpixel 208 to provide for increasing the size or surface area of the red quantum layer disposed thereon. In some embodiments, a ratio between the emission area of the red subpixel 208 and the emission area of the blue subpixel 212 may be about 2.2x or less, about 2.1x or less, about 2. Ox or less, about 1.9x or less, about 1.8x or less, about 1.7x or less, about 1.6x or less, about 1.5x or less, about 1.4x or less, about 1.3x or less, or about 1.2x or less. In an embodiment, the emission area of the red subpixel 208 is about 2.625 pm2and the emission area of the blue subpixel 212 is about 1 .875 pm2such that the ratio of the emission area of the red subpixel 208 over the blue subpixel 212 is about 1.4x.

[0043] In some embodiments, as the luminance or light intensity of green and red emission lights emitted from the green and red subpixels 210, 208 required to achieve white light is greater than the intensity of blue light emitted from the blue subpixel, increasing the size or surface areas of the green and red subpixels (and the corresponding green and red quantum layers formed therein) may allow for decreasing the overall stress of the subpixels. For example, the foregoing may advantageously provide for minimizing the degradation of the green and red quantum dot layers which in turn provide for improving the overall operating lifetime of the pLED display 100.

[0044] In some embodiments, each of the pLED dies 202, 204, 206 may be fabricated with varying size or dimensions based on the subpixels the pLED die is intended to illuminate. As discussed above, in some embodiments, each of the red, green, and blue subpixels may have different power and current density requirements in order for the display to reach optimum driving points. In some embodiments, the current required by the pLED dies of the green and blue subpixels may be about 2x the current required for the red subpixel in order to achieve white light. As shown in FIG. 2, in some embodiments, the second and third pLED dies 204, 206 for illuminating the green and blue subpixels 210, 212 may therefore be formed larger than the first pLED die 202 for illuminating the red subpixel 208 to offset the larger currents needed to be applied to the pLED dies of the green and blue subpixels 210,212for white light (e.g., D65). Without being bound by theory, it is believed increasing the size of the pLED dies of the green and blue subpixels 210, 212 in turn provides for decreasing the current density as applied in the context of the 2x currents needing to be provided to achieve white light. In some embodiments, the size of the second and third pLED dies 204, 206 may be increased such that the current densities between each of the first, second, and third pLED dies 202, 204, 206 are substantially the same when white light is achieved. In some embodiments, increasing the size of the second and third pLED dies 204, 206 also increases the external quantum efficiency (EQE) of the pLED dies so as to decrease the overall power consumption by the green and blue subpixels 210, 212.

[0045] In some embodiments, the second pLED die 204 for illuminating the green subpixel 210 may also be further larger than the third pLED die 206 for the blue subpixel 212 due to the larger emission area and to improve the power efficiency of the green quantum dot layer formed therein. Without being bound by theory, it is believed that increasing the size of the pLED dies 204, 206 for the green and blue subpixels 210, 212 may improve the quantum efficiency of and / or lower the power consumption by the pLED dies 204, 206 of the green and blue subpixels 210, 212.

[0046] FIG. 3 is a schematic split-open cross sectional view of a pLED structure 300, according to certain embodiments of the present disclosure. In the embodiment shown, the pLED structure 300 comprises the pLED pixel 200 depicted in FIG. 2 being cut between the red and blue subpixels 208, 212 and split open to reveal a cross- sectional linear arrangement of the blue, green, and red subpixels 212, 210, 208. As depicted, the pLED structure 300 includes a color conversion layer 304 disposed on a pLED layer 306 coupled to a backplane layer 308. In some embodiments, the pLED layer 306 coupled with the backplane layer 308 may correspond with the pLED display 100 depicted in FIG. 1. The color conversion layer 304 may then be formed on the pLED layer 306, or formed on a separate transparent substrate and subsequently coupled to the pLED layer 306 after fabrication of the color conversion layer 304 is complete.

[0047] In some embodiments, a connecting layer 313 is disposed across the pLED dies 202, 204, 206 between the pLED layer 306 and the color conversion layer 304. For example, the connecting layer 313 can extend across the entirety of the pLEDarray 110 in the pLED layer 306. In some embodiments, the connecting layer 313 may fabricated as part of the pLED dies of the pLED layer 306. For example, the connecting layer 313 can be a doped semiconductor layer, e.g., the n-doped semiconductor layer, such as an n-doped gallium nitride (n-GaN) layer, in each of the pLED dies.

[0048] The color conversion layer 304 includes a plurality of isolation structures 310 defining a plurality of wells 312. Each of the wells 312 may be formed to isolate a corresponding pLED die of the pLED array 110. In some embodiments, each of the plurality of wells 312 may be formed to define the emission area of each of the subpixels. In some embodiments, a laser induced direct etching process is used to form the plurality of wells 312 and plurality of isolation structures 310. Assuming the pLED structure 300 is for a three-color display as discussed above with respect to the pixel 200, the well 312 for the red subpixel 208 includes a red quantum dot layer 314 disposed over the first pLED die 202. The red quantum dot layer 314 is operable as a color conversion layer to convert the blue excitation light emitted by the first pLED die 202 so that the red subpixel 208 is operable to emit peak intensity wavelengths of visible red light.

[0049] As with the red quantum dot layer 314 deposited for the red subpixel 208, a green quantum dot layer 316 is similarly disposed over the second pLED die 204 for the green subpixel 210. Similar to the red quantum dot layer 314, the green quantum dot layer 316 converts blue excitation light emitted by the second pLED die 204 to visible green light. For the blue subpixel 212, the well 312 for defining the emission area may include a matrix layer 318 that is transparent and quantum dot layer free such that blue light emitted by the third pLED die 206 may be used for illuminating the blue subpixel 212. In an embodiment, the matrix layer 318 comprises of a polymer material with TiOx.

[0050] In some embodiments, during fabrication of multi-color displays, the plurality of isolation structures 310 for defining the plurality of wells 312 may be formed over the pLED layer 306 such that the red and green quantum dot layers 314, 316 are deposited directly on the pLED layer 306. In other embodiments, the red and green quantum dot layers 314, 316 may be separately deposited in wells of a color conversion array formed on a second substrate. In such embodiments, the colorconversion array having the red and green quantum dot layers 314, 316 deposited and cured thereon may subsequently be coupled with the pLED layer 306 to form a multi-color display.

[0051] In some embodiments, after the quantum dot layers are deposited and cured, additional layers such as protective layers, passivation layers, and other layers can be deposited over the cured quantum dot layers. In some embodiments, the pLED structure 300 may further include a color filter layer 320 disposed over each of the red and green quantum dot layers 314, 316 of the red and green subpixel 208, 210 and the matrix layer 318 of the blue subpixel 212. In an embodiment, the color filter layer 320 may filter or reduce the amount of residual excitation blue light (e.g., blue light having an emission wavelength between about 400 nm and about 430 nm) emitted by the pLED dies that is otherwise not absorbed by the quantum dot layers. In an embodiment, the color filter layer 320 may be configured to allow certain wavelengths of light to pass through, such as wavelengths corresponding to the respective subpixel color the color filter layer 320 is formed therein. In an embodiment, the color filter layer 320 for the red subpixel 208 is a red color filter configured to only allow light in the visible red portion of the visible spectrum to pass through toward a viewer. In another embodiment, the color filter layer 320 for the green subpixel 210 is a green color filter configured to allow light in the visible green portion of the visible spectrum to pass through toward a viewer. Likewise, in an embodiment, a blue color filter may be formed for the blue subpixel 212 so as to allow only light in the visible blue portion of the visible spectrum to pass through. In other embodiments, when the pLED die is configured to emit blue light, no color filters may be used for the blue subpixel 212.

[0052] In some embodiments, a microlens 322 may be further disposed over the color filter layer 320 in each of the wells of the subpixels such that the emission light passing through the color filter layer 320 may be focused to further improve the quality of an image displayed by the pLED display. In some embodiments, the microlens 322 can improve the luminance of the visible light emitted from each of the subpixels. As such, the microlens 322 in turn may be used to decrease the power consumption of each subpixel.

[0053] In some embodiments in which the pLED dies are operable to emit UV excitation light, a UV blocking layer (not shown) may be disposed over the quantum dot layers of each subpixel to filter out and reduce any UV light generated by the pLED dies and not absorbed by the quantum dot layers. In some embodiments, the UV blocking layers may be formed from materials such as SiO2, Si3N4, optically transparent organic and inorganic thin films, and the like. Although not depicted, other processes are also contemplated such as planarization or leveling of layers or fillers.

[0054] As discussed above, low duty ratio is one of the techniques used to reduce motion blurs of optical displays. Without being bound by theory, it is believed that reducing the display emission duty ratio to less than 20% would be beneficial for minimizing or suppressing motion blur. In some embodiments, a pulse amplitude modulation (PAM) driving scheme is utilized in the pLED display 100 to drive the pLED array 110 with a low duty ratio, such as a duty ratio of less than 20%. In some embodiments, the pLED display 100 includes driving the pLED array with a low duty ratio of less than about 15%, less than about 10%, less than about 5%, or about 5%.

[0055] Referring back to the FIG. 1 , the pLED array 110 may be driven by the column drivers 118c and the row drivers 118d of the backplane circuitry 118. The backplane circuitry 118, including the column drivers 118c and the row drivers 118d may comprise a plurality of pixel circuits in which each pLED is electrically connected to a pixel circuit configured to receive a signal, for example, a data voltage from the DDIC. In an embodiment, each pixel circuit includes pixel logic circuitry connected to at least one transistor and a pLED die. In an embodiment, the transistor may be a field effect transistor (FET) and the pixel logic may include logic elements (e.g., one or more logic gates or combinatorial logic circuits) that can generate a digital output or value (e.g., an on or off value, or one or zero value) to be outputted to one end of the transistor connected thereto. The pixel circuit in turn acts as a transmitter for generating a PAM driving current proportional to the level of the incoming data voltage from the DDIC. The width of the data voltage pulse from the DDIC may be a function of the integrated driving current density needed by the pLED to achieve a desired gray level. The pLED die connected thereto are in turn configured to emit light based on the PAM driving signal provided from the connected pixel circuit.

[0056] FIG. 4 illustrates an exemplary pixel circuit that may be implemented with the DDIC described above, according to certain embodiments. In some embodiments, the pixel circuit for implementing the PAM driving scheme of the pLED array 110 may comprise a circuit 400 consisting of four p-channel MOSFETs (T 1 , T2, T3, and TD), and two capacitors (C1 , C2), as shown in FIG. 4. In other embodiments, other conventional circuits with different numbers of transistors and capacitors (e.g., 3T1 C, 6T1 C, etc.) suitable for implementing PAM driving techniques may alternatively be used. The circuit 400 may be utilized in the backplane circuitry 118 for generating a PAM driving signal for controlling the pLED array 110. In an embodiment, the DDIC and the pixel circuit may drive the pLEDs utilizing active driving (e.g., active matrix) in which pixels remain in the on state throughout the frame period until their values are updated. Active driving provides for the on / off state and gray value of each pixel to be controlled independently which in turn may also assist in providing the pLED display with a faster refresh rate, higher brightness and less power consumption. In other embodiments, the DDICs may drive the pLEDs utilizing passive driving (e.g., passive matrix).

[0057] In an embodiment, the circuit 400 may be a 4 transistor and 2 capacitor pixel driving circuit utilized for generating a PAM signal. T1 and T2 are switching transistors, T3 is a mirror transistor, and TD is a driving transistor. C1 and C2 are storage capacitors connected in series between Node G and VDD. When the voltage at node S meets the threshold voltage (Vth) requirements of T2 and TD, T2 and TD are turned on. The two capacitors can be used to adjust the Vth of T2 and TD. According to the current mirror principle, the current flowing through the pLED is proportional to Idata.

[0058] FIGs. 5A and 5B are graphs showing exemplary PAM signals for controlling a driving current, according to certain embodiments. As PAM driving techniques modulate the amplitude of the driving pulse to control the current supplied the pLEDs and set the desired intensity or brightness (as opposed to PWM driving techniques which modulate the frequency and the duty ratio of the signal to control the current delivered), utilizing a PAM driving technique enables driving the pLEDs with a constant and low duty ratio. In some embodiments and as shown in FIG. 5A, driving the pLED array 110 with the PAM driving scheme and a low duty ratio (5% in the example depicted in FIG. 5A) advantageously enables each of the pLEDs to emithigher peak luminance as compared to traditional OLEDs with larger duty ratios (20% as depicted in FIG. 5B). The foregoing in turn can assist in improving display performance by reducing motion blur. As shown in FIGs. 5A and 5B, the shorter duty ratio provides for higher peak luminance.

[0059] FIGs. 6A and 6B are graphs showing the luminance or light intensity of a pLED pixel over time, according to certain embodiments. Specifically, FIG. 6A depicts a graph 600A showing the change in luminance over time of each of the red, green, and blue visible light emitted by the pixel 200 in which the size of the subpixels and pLED dies are varies as described above with respect to FIG. 2. The graph corresponds to applying the necessary current to each of the pLEDs dies of each subpixel in order for the LED pixel to achieve D65 white light. By taking into consideration the varying characteristics, efficiencies, yields, and / or lifetimes of the red and green quantum dot layers formed for each of the red and green subpixels of the pixel 200, varying the sizes of the emission area of the subpixels and pLED dies therein provide for minimizing stress on and power consumption by the display which in turn may translate into improved display operating lifetime.

[0060] In contrast, FIG. 6B depicts a graph 600B showing the change in luminance when the size and emission area of each of the red, green, and blue subpixels are the same, as a reference. In FIG. 6B, the luminance of the green light decreases more rapidly over time as compared to the luminance of the green light in FIG. 6A. As discussed above, green quantum dots are less stable than red quantum dots with a lower quantum yield and lifetime. As the green subpixel generally requires twice the current intensity than the red subpixel in order for the pixel to deliver D65 white light, the increased stress from the higher current combined with the characteristics of green quantum dots mentioned above naturally causes the green quantum dot layers to degrade faster as compared to the red quantum dot layer. However, by varying the subpixel sizes as shown in the pixel 200 of the present disclosure and providing for a larger green quantum dot layer with a larger corresponding pLED die, the rate of degradation of the green quantum dot layer can be lessened, as shown in FIG. 6A, so as to improve the overall operating life of the display.

[0061] FIG. 6A also shows that the variations made to the red and blue subpixels as described above (i.e., decrease in the size of the red and blue subpixels andincreasing the size of the pLED die for the blue subpixel) in order to improve the operation of the green subpixels is sufficient to enable the red and blue subpixels to continue to function as expected and provide the same luminance as if the subpixels were all the same size, as shown in FIG. 6B.

[0062] FIG. 7 is a schematic top view of a pixel 700, according to certain embodiments. The pixel 700 may be part of a larger arrangement of pixel structures that make up at least a portion of a high pixel density optical display similar to the pixel 200 depicted in FIG. 2. In the embodiment shown, the pixel 700 may similarly also be for a three-color display in which each pixel 700 includes three hexagonal-shaped subpixels, one for each color, e.g., one each for the blue, green, and red color channels. As such, each pixel 700 includes three pLED dies for illuminating each of the three subpixels of the pixel 700. In an embodiment, the pixel 700 includes a first pLED die 702 for illuminating a red subpixel 708, a second pLED die 704 for illuminating a green subpixel 710, and a third pLED die 706 for illuminating a blue subpixel 712.

[0063] The pLED dies 702, 704, 706 may be similarly controlled and integrated with a backplane circuitry, in the same manner as the pLED dies 202, 204, 206 discussed above. The pLED dies 702, 704, 706 may be formed in the same manner as pLED dies 202, 204, 206 such that each of the dies can be individually and independently activated and controlled by the circuitry to address and control the subpixels of each of the pixel 700 in the final display. In an embodiment, a pulse amplitude modulation (PAM) driving scheme is utilized to drive the pLED dies 702, 704, 706 of the pixel 700 with a low duty ratio, such as a duty ratio of less than 20%. In some embodiments, the pLED dies 702, 704, 706 of pixel 700 may be driven with a low duty ratio of less than about 15%, less than about 10%, less than about 5%, or about 5%.

[0064] The pixel 700 also includes isolation structures 714 disposed between neighboring pLED dies. The isolation structures 714 define a plurality of hexagonalshaped wells with each of the pLED dies 702, 704, 706 in an individual well defined by the isolation structures 714. As shown in FIG. 7, the pixel 700 includes the first pLED die 702 disposed in a first well 716, the second pLED die 704 disposed in a second well 718, and the third pLED die 706 disposed in a third well 720. The isolationstructures 714 can be similar to the isolation structures 214 discussed above. The isolation structures 714 may be a photoresist or metal, and can be deposited by conventional lithography processes. The optical density of the isolation structures 714 similar provides for color isolation between each of the subpixels and can help prevent color bleeding or contamination during the light-up operation. As such, each of the plurality of wells may therefore in turn define a corresponding emission region of each of the red, green, and blue subpixels 708, 710, 712 in the pixel 700.

[0065] In an embodiment, the isolation structures 714 for the pixel 700 are formed such that the second well 718 corresponding to the emission area of the green subpixel 710 is larger than the first and third wells 716, 720 corresponding to the emission area of the red and blue subpixels 708, 712, respectively. As mentioned above, it is believed that increasing the size of the emission area of the green subpixel 710 (e.g., the size or surface area of the green quantum dot layer) provides for reducing the stress from the second pLED die 704 and the higher current / intensity being applied to the green subpixel 710, for example to achieve white light, as well as improve the overall efficiency of the green quantum dot layer. Increasing the surface area of the green quantum dot layer may correspondingly increase the amount of LED light injected into the green quantum dot layer resulting in higher power efficiency.

[0066] In some embodiments, the pLED die 706 is similar to the pLED die 206 in being operable to emit blue light and a color conversion layer is therefore not needed for the blue subpixel 712. In such an embodiment, the third well 720 or the emission area of the blue subpixel 712 may correspondingly also be smaller than the first well 716 or the emission area of the red subpixel 208 to provide for increasing the size of the first and second wells 716, 718. Increasing the size of the first and second wells 716, 718 in turn allows for increasing the surface area of the red and green quantum layers disposed therein. Increasing the size or surface areas of the green and red subpixels (and the corresponding green and red quantum layers formed therein) may allow for decreasing the overall stress on the subpixels. For example, the foregoing may advantageously provide for minimizing the degradation of the green and red quantum dot layers which in turn provide for improving the overall operating lifetime of the pLED display 100.

[0067] In an embodiment, each of the pLED dies 702, 704, 706 may be fabricated with the same structure so as to generate the same wavelength range (this can be termed “monochrome” pLEDs). In an embodiment, each of the pLED dies 702, 704, 706 may be a blue pLED die that can generate light in the violet or blue range. For example, in an embodiment, the pLED dies 702, 704, 706 may each be operable to emit blue light having a peak emission wavelength in the visible blue portion of the visible spectrum. In further embodiments, the pLED dies 702, 704, 706 may be operable to emit blue light characterized by a peak emission wavelength of greater than or about 420 nm, greater than or about 430 nm, greater than or about 440 nm, greater than or about 450 nm, greater than or about 460 nm, greater than or about 470 nm, greater than or about 480 nm, greater than or about 490 nm, or more. In another embodiment, each of the pLED dies 702, 704, 706 is a UV pLED die that can generate light in the ultraviolet (UV), e.g., the near ultraviolet, range. For example, the pLED dies 702, 704, 706 can generate light in a range of 365 to 405 nm. Without being bound by theory, it is believed that by using pLED dies that emit blue light as the excitation light source, the third pLED die 706 may be used to directly provide blue light for illuminating the blue subpixel 712 without the need for a color conversion material. This in turn enables the size or emission area for the blue subpixel 712 to be reduced as quantum yield and / or quantum efficiency of a blue quantum dot layer is not a concern.

[0068] In some embodiments, similar to the sizing of the pLED dies 202, 204, 206 discussed above in the pixel 200, each of the pLED dies 702, 704, 706 may be fabricated with varying size or dimensions based on the color of the subpixel the pLED die is intended to illuminate. As shown in FIG. 7, in some embodiments, the second and third pLED dies 704, 706 for illuminating the green and blue subpixels 710, 712 may therefore be formed larger than the first pLED die 702 for illuminating the red subpixel 708. In some embodiments, the size of the second and third pLED dies 704, 706 may be increased such that the current densities between each of the first, second, and third pLED dies 702, 704, 706 are substantially the same when white light is achieved. In some embodiments, increasing the size of the second and third pLED dies 704, 706 also increases the external quantum efficiency (EQE) of the pLED dies so as to decrease the overall power consumption by the green and blue subpixels 710, 712. In some embodiments, the second pLED die 704 for illuminating the greensubpixel 710 may also be formed larger than the third pLED die 706 for the blue subpixel 712 due to the larger emission area and to improve the power efficiency of the green quantum dot layer formed therein.

[0069] In some embodiments, similar to the pLED structure 300 discussed above, each of the wells of the pixel 700 may further comprise a color filter and / or a microlens disposed over the color conversion agent layer in each well. In some embodiments, as shown in FIG. 7, each of the microlens 722 comprises a microlens 722 having a circular shape disposed within each of hexagonal-shaped first, second, and third wells 716, 718, 720 of the pixel 700. The microlens 722 are fitted in each of the first, second, and third wells 716, 718, 720 such that the emission light emitted by the pLED dies 702, 704, 706 within each well, respectively, may be focused by the microlens 722 to further improve the quality of an image displayed by the pLED display. In some embodiments, the microlens 722 can improve the luminance of the visible light emitted from each of the red, green, and blue subpixels 708, 710, 712. In some embodiments, the microlens 722 may better refract the emitted light towards the viewer. For example, emission light that would otherwise escape from the viewing angle of the viewer may be bent back towards the viewer by the microlens 722. As such, the microlens 722 may in turn provide for improved brightness and efficiency by the pLED display. Without being bound by theory, it is believed that the hexagonal-shaped wells 716, 718, 720 of pixel 700 provide a better and more efficient fit for each of the microlens 722, as compared to quadrilateral shaped subpixels, so as to benefit from the microlens 722.

[0070] Overall, the present disclosure provides for a pLED display utilizing PAM driving techniques with a low duty ratio, which can provide for reduced and / or eliminated motion blur without sacrificing device operating lifetimes. Moreover, the present disclosure provides for utilizing red and green quantum dot layers with blue light emitting pLED dies so as to compensate for any color shifts caused by the varying current densities associated with PAM driving. In some embodiments, the size of each of the red, green, and blue subpixels may also be varied in the pixel so as to minimize quantum dot degradation so as to improve device operating lifetimes. In some embodiments, the size of the corresponding blue light emitting pLED dies may also be varied for each of the red, green, and blue subpixels so as to lower power consumption to improve device reliability and performance.

[0071] While the foregoing is directed to implementations of the present disclosure, other and further implementations of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:

1. An optical display, comprising: a backplane; a backplane circuitry disposed in the backplane, the backplane circuitry comprising pixel circuits for generating a pulse amplitude modulated (PAM) driving current having a constant duty ratio of less than 20%; an array of pLED dies formed on the backplane and electrically integrated with the backplane circuitry in which the array of pLED dies is controlled by the PAM driving current generated by the pixel circuits; a plurality of structures coupled to the array of pLED dies, the plurality of structures for defining wells of a plurality of subpixels; a first color conversion layer disposed in wells of first color subpixels of the plurality of subpixels, the first color conversion layer to convert excitation light emitted by first pLED dies of the array of pLED dies to emission light of a first color; and a second color conversion layer disposed in wells of second color subpixels of the plurality of subpixels, the second color conversion layer to convert excitation light emitted by second pLED dies of the array of pLED dies to emission light of a second color.

2. The optical display of claim 1 , wherein the constant duty ratio of the PAM driving current is about 10% or less.

3. The optical display of claim 1 , wherein the constant duty ratio of the PAM driving current is about 5%.

4. The optical display of claim 1 , wherein first pLED dies and second pLED dies of the array of pLED dies are operable to emit visible blue excitation light.

5. The optical display of claim 1 , wherein third pLED dies of the array of pLED dies disposed in wells of third color subpixels of the plurality of subpixels are operable to emit visible blue emission light from wells of third color subpixels of the plurality of subpixels.

6. The optical display of claim 1 , further comprising color filters disposed over the first color conversion layer and the second color conversion layer.

7. The optical display of claim 1 , further comprising microlens disposed in wells of the plurality of subpixels for focusing emission light emitted from each of the plurality of subpixels.

8. The optical display of claim 1 , wherein first color subpixels of the plurality of subpixels correspond to red subpixels, second color subpixels of the plurality of subpixels correspond to green subpixels, and third color subpixels of the plurality of subpixels correspond to blue subpixels.

9. The optical display of claim 8, wherein the first color conversion layer comprises a red quantum dot layer and the second color conversion layer comprises a green quantum dot layer.

10. The optical display of claim 8, wherein an emission area of green subpixels is larger than an emission area of red subpixels.11 . The optical display of claim 8, wherein an emission area of red subpixels is larger than an emission area of blue subpixels.

12. The optical display of claim 8, wherein first pLED dies of the array of pLED dies for green subpixels and third pLED dies of the array of pLED dies for blue subpixels are larger than second pLED dies of the array of pLED dies for red subpixels.

13. The optical display of claim 8, wherein first pLED dies of the array of pLED dies for green subpixels are larger than third pLED dies of the array of pLED dies for blue subpixels.

14. The optical display of claim 1 , further comprising color filter layers disposed over the first and second color conversion layers, the color filter layer disposed over the first color conversion layer configured to only allow emission light of the first color to pass through, and the color filter layer disposed over the second color conversion layer configured to only allow emission light of the second color to pass through.

15. An optical display, comprising: a backplane;a backplane circuitry disposed in the backplane, the backplane circuitry comprising pixel circuits for generating a pulse amplitude modulated (PAM) driving current having a constant duty ratio of less than 20%; an array of pLED dies operable to emit blue light and formed on the backplane and electrically integrated with the backplane circuitry in which the array of pLED dies is controlled by the PAM driving current generated by the pixel circuits ; a plurality of structures coupled to the array of pLED dies, the plurality of structures for defining wells of a plurality of subpixels; a green quantum layer disposed in wells of green subpixels of the plurality of subpixels, the green quantum layer to convert blue excitation light emitted by first pLED dies of the array of pLED dies to visible green emission light; and a red quantum layer disposed in wells of red subpixels of the plurality of subpixels, the red quantum layer to convert blue excitation light emitted by second pLED dies of the array of pLED dies to visible red emission light, wherein third pLED dies of the array of pLED dies disposed in wells of blue subpixels of the plurality of subpixels are operable to emit visible blue emission light.

16. The optical display of claim 15, wherein the constant duty ratio of the PAM driving current is about 10% or less.

17. The optical display of claim 15, wherein a ratio between an emission area of green subpixels and an emission area of red subpixels is about 2. Ox or less.

18. The optical display of claim 15, wherein a ratio between an emission area of red subpixels and an emission area of blue subpixels is about 2. Ox or less.

19. A color conversion array for an optical display, comprising: a plurality of structures, each structure having a base configured to be coupled to a backplane of the optical display; a plurality of wells, each of the plurality of wells defined within one or more of the plurality of structures, and first wells of the plurality of wells are larger than second wells of the plurality of wells, and second wells of the plurality of wells are larger than third wells of the plurality of wells; a first color conversion layer disposed within first wells of the plurality of wells to convert a first excitation light to emission light of a first color; anda second color conversion layer disposed within second wells of the plurality of wells to convert a second excitation light to emission light of a second color, wherein the first excitation light and the second excitation light are emitted by pLED dies in response to pulse amplitude modulated (PAM) driving currents having a constant duty ratio of less than 20%.

20. The color conversion array of claim 19, wherein each of the plurality of wells comprise a hexagonal shape configured to fit a microlens for focusing emission light emitted from each of the plurality of wells.

Images