Micro-scale light emitting diode (micro-LED) with a chip size less than 100 μm has improved light... more Micro-scale light emitting diode (micro-LED) with a chip size less than 100 μm has improved light extraction efficiency due to increased sidewall emission. However, it causes mismatched angular distributions between AlGaInP-based red micro-LED and InGaN-based blue/green counterparts because of the epitaxial material difference. As a result, color shift of RGB micro-LED displays may become visually noticeable. To address this issue, the angular distributions of RGB micro-LEDs are analyzed theoretically and experimentally. In addition, a device structure with top black matrix and taper angle in micro-LEDs is proposed, which greatly suppresses the color shift while keeping a reasonably high light extraction efficiency.
We demonstrate a full RGB liquid crystal-tunable reflective surface where the color of the alumin... more We demonstrate a full RGB liquid crystal-tunable reflective surface where the color of the aluminum nanostructure is changed as a function of applied voltage. We then integrate the system with a TFT to depict images.
Journal of The Society for Information Display, Mar 21, 2019
A full-color micro-LED display can be achieved by red, green, and blue (RGB) chips or by a blue/u... more A full-color micro-LED display can be achieved by red, green, and blue (RGB) chips or by a blue/ultraviolet (UV) micro-LED array to pump downconverters. The latter helps relieve the burden of epitaxial growth of tri-color micro-LED chips. However, such a color-converted micro-LED system usually suffers from color crosstalk and low efficiency due to limited optical density of color converters. With funnel-tube array and reflective coating on its inner surface, the crosstalk is eliminated, and the optical efficiency can be improved by more than two times. In addition, the ambient contrast ratio is also improved because of higher light intensity. The color gamut of this device is approximately 92% of DCI-P3 standard.
We demonstrate multi-fold speed enhancement of liquid crystal phase modulators through laser writ... more We demonstrate multi-fold speed enhancement of liquid crystal phase modulators through laser written sub-micron scaffolds. The versatile fabrication process allows devices with arbitrary liquid crystal alignment and, therefore, polarization dependence. We lastly discuss the prospects of the technology for large area (>0.5 in 2) spatial light modulators.
We report two new liquid crystal mixtures with high clearing point, small visco-elastic coefficie... more We report two new liquid crystal mixtures with high clearing point, small visco-elastic coefficient and low activation energy. With overdriving and undershooting approach, the response time is less than 10ms for FFS LCDs at T=0 o C and TN at 20 o C. Therefore, these mixtures greatly improve the performances of vehicle displays at extreme environments.
We propose a novel optical design to tailor the angular distribution of a micro-LED (µLED) displa... more We propose a novel optical design to tailor the angular distribution of a micro-LED (µLED) display system and use vehicle display as an example to illustrate the design principles. The display system consists of a µLED array with a tailored LED structure, a small formfactor compound parabolic concentrator (CPC) system, and a functional engineered diffusor. It provides high efficiency, high peak brightness, and small formfactor. In the design process, a mix-level optical simulation model, including the angular distribution of polarized emission dipole (dipole emission characteristics), Fabry-Perot cavity effect (wave optics), and light propagation process (ray optics), is established to analyze the angular distribution of µLEDs. Such an optical design process from dipole emission to display radiation pattern can be extended to other µLED display systems for different applications.
A deep-dyeing strategy that can convert commercial PET polymers into luminescent perovskite-polym... more A deep-dyeing strategy that can convert commercial PET polymers into luminescent perovskite-polymer composites is demonstrated. Such composites show excellent color tunability, saturated colors, high efficiency and superior environmental stability.
Metamaterials, Metadevices, and Metasystems 2016, 2016
In this paper, we report a computational and experimental study using tunable infrared (IR) metam... more In this paper, we report a computational and experimental study using tunable infrared (IR) metamaterial absorbers (MMAs) to demonstrate frequency tunable (7%) and amplitude modulation (61%) designs. The dynamic tuning of each structure was achieved through the addition of an active material—liquid crystals (LC) or vanadium dioxide (VO2)--within the unit cell of the MMA architecture. In both systems, an applied stimulus (electric field or temperature) induced a dielectric change in the active material and subsequent variation in the absorption and reflection properties of the MMA in the mid- to long-wavelength region of the IR (MWIR and LWIR, respectively). These changes were observed to be reversible for both systems and dynamic in the LC-based structure.
Experimental evidence proves that polymer-stabilized blue phase liquid crystal is not perfectly o... more Experimental evidence proves that polymer-stabilized blue phase liquid crystal is not perfectly optically isotropic. The optical rotatory power (ORP) of double twist cylinders causes the polarization axis of the transmitted light to rotate a small angle, and leaks through the crossed polarizers. Rotating the analyzer by ~2 o to correct this ORP can improve the contrast ratio by 3X.
Molecular Crystals and Liquid Crystals, Mar 24, 2015
Since 1981, blue phase liquid crystal (BPLC) was regarded as optical isotropy and high contrast r... more Since 1981, blue phase liquid crystal (BPLC) was regarded as optical isotropy and high contrast ratio (CR) should be achieved easily. However, low CR of BPLC display was reported in all literatures. Here, we show BPLC is non-ideal optical isotropy which leads to poor CR. In our report, BPLC not only revealed primary structure of double-twist cylinder and secondary structure of lattice but also revealed tertiary structure of self-alignment on electrode surface. This finding will be useful to improve CR and inspire researches in display industry and academics.
Plasmonic structural color has recently garnered significant interest as an alternative to the or... more Plasmonic structural color has recently garnered significant interest as an alternative to the organic dyes standard in print media and liquid crystal displays. These nanostructured metallic systems can produce diffraction limited images, be made polarization dependent, and exhibit resistance to color bleaching. Perhaps even more advantageous, their optical characteristics can also be tuned, post-fabrication, by altering the surrounding media's refractive index parallel to the local plasmonic fields. A common material with which to achieve this is liquid crystal. By reorienting the liquid crystal molecules through external electric fields, the optical resonances of the plasmonic filters can be dynamically controlled. Demonstrations of this phenomenon, however, have been limited to modest shifts in plasmon resonance. Here, we report a liquid crystal-plasmonic system with an enhanced tuning range through the use of a shallow array of nano-wells and high birefringent liquid crystal. The continuous metallic nanostructure maximizes the overlap between plasmonic fields and liquid crystal while also allowing full reorientation of the liquid crystal upon an applied electric field. Sweeping over structural dimensions and voltages results in a color palette for these dynamic reflective pixels that can further be exploited to create color tunable images. These advances make plasmonic-liquid crystal systems more attractive candidates for filter, display, and other tunable optical technologies.
In addition to displays, liquid crystals (LCs) have also found widespread applications in photoni... more In addition to displays, liquid crystals (LCs) have also found widespread applications in photonic devices, such as adaptive lens, adaptive optics, and sensors, because of their responses to electric field, temperature, and light. As the fabrication technique advances, more sophisticated devices can be designed and created. In this review, we report recent advances of two-photon polymerization-based direct-laser writing enabled LC devices. Firstly, we describe the basic working principle of two-photon polymerization. With this powerful fabrication technique, we can generate anchoring energy by surface morphology to align LC directors on different form factors. To prove this concept, we demonstrate LC alignment on planar, curvilinear surfaces as well as in three-dimensional volumes. Based on the results, we further propose a novel, ultra-broadband, twisted-nematic diffractive waveplate that can potentially be fulfilled by this technique. Next, we briefly discuss the current status of direct-laser writing on LC reactive mesogens and its potential applications. Finally, we present two design challenges: fabrication yield and polymer relaxation/deformation, remaining to be overcome.
are self-assembled and no alignment layer is needed. Due to the short coherent length, BPLC achie... more are self-assembled and no alignment layer is needed. Due to the short coherent length, BPLC achieves fast response time in the submillisecond range, [23] making it attractive for many electro-optical applications that require rapid switching. Moreover, BPLC offers quasi-optically isotropic off-state for off-resonant wavelength, [24] and exhibits Kerr constant thousands of times higher than conventional Kerr media. However, blue phases (including BPI, BPII and BPIII) are only stable within a very narrow temperature range between chiral nematic and isotropic phases. [20] Great efforts were devoted to understanding the structures of blue phases, both experimentally and theoretically. [25-32] BPIII is an amorphous structure,while BPI and BPII are both cubic structures made of double twist cylinders (DTCs) but arranged differently as shown in Figure 1a. Inside each DTC, liquid crystal directors are twisted from-45 o to +45 o about any radius of the cylinder. However, as the cylinders are symmetrically arranged in three dimensions, it is impossible to make the directors match everywhere. Thus, defects occur at the points where the DTCs are in contact to relieve the elastic strain energy. As a result, blue phases only exist within a narrow temperature range (0.5-2 °C), [33] which had hindered them from practical applications for decades. Much research work has been carried out in order to broaden the temperature range of blue phases. [34-46] Among them, polymer stabilization [39] is the most commonly used method, which was first proposed by Kikuchi et al. in 2002. By selectively concentrating the cross-linked polymer network in the disclination lines, the DTC structure was stabilized with a wide temperature range over 60 K. In the early years, polymer-stabilized blue phase liquid crystal was mainly employed for display applications. With fast response time, it could enable color sequential display and triple the optical efficiency; [47] with natural self-assembly, it does not require any alignment layer; and with quasi-isotropic dark state, it could achieve high contrast ratio and wide viewing angle. In 2008, Samsung demonstrated the first PS-BPLC display prototype at Society for Information Display exhibition. [48] In 2015, AU Optronics also demonstrated a PS-BPLC display using new wall electrodes, which could be driven by conventional integrated circuit. [49] Extensive work has been done on improving PS-BPLC display performances from both material Polymer-stabilized blue phase liquid crystal (PS-BPLC) is emerging as a promising candidate for next-generation photonic applications due to its attractive features: nano-scale structure that enables sub-millisecond response time, self-assembly that eliminates the need for surface alignment, and threedimensional cubic structure so that it is quasi-isotropic without applied field. Here, we will look into the photonic properties of PS-BPLC microscopically and macroscopically, and will focus on the non-display photonic applications based on these properties. First we will give a general introduction to the polymer stabilization process, general photonic properties, electric field effects and desirable electro-optical properties of PS-BPLC. Next we will present applications based on the microscopic photonic properties in the cubic structures with double twist cylinders: photonic band gap, scattering and unwinding of the double twist structure under electric field. Then, we will cover applications based on the macroscopic refractive index change of PS-BPLC under electric fields, whose mechanisms are further classified into phase retardation, phase modulation, and resonance condition change. Finally we will look into the remaining challenges and future perspectives of PS-BPLC for photonic applications.
A novel method to achieving active refractive and diffractive liquid-crystal microlens arrays is ... more A novel method to achieving active refractive and diffractive liquid-crystal microlens arrays is demonstrated. By two-photon polymerization, liquid-crystal alignment can be directly generated on curved or planar surface and thus active microlens arrays can be created by fulfilling liquid-crystal cells. This method provides a new route toward liquid-crystal microlens arrays.
We reported a fast-response LCD for virtual reality applications. The average gray-to-gray (GTG) ... more We reported a fast-response LCD for virtual reality applications. The average gray-to-gray (GTG) response time is 0.93ms and its GTG motion-picture-response-time (MPRT) is comparable to OLED. By increasing the frame-rate and/or decreasing the backlight duty-ratio, we can achieve MPRT < 1 ms to display fastmoving objects with unnoticeable motion blurs.
We develop a patterned cholesteric liquid crystal polymer film with reflection and scattering sta... more We develop a patterned cholesteric liquid crystal polymer film with reflection and scattering states. By integrating this film into a color‐converted micro‐LED display, the optical efficiency is increased by 2.14x at 90% Rec.2020 color gamut and the average angular color shift δu'v′ is reduced from 0.03 to 0.018.
Micro-LED (light-emitting diode) is a potentially disruptive display technology, while power cons... more Micro-LED (light-emitting diode) is a potentially disruptive display technology, while power consumption is a critical issue for all display devices. In this paper, we develop a physical model to evaluate the power consumption of micro-LED displays under different ambient lighting conditions. Both power efficiency and ambient reflectance are investigated in two types of full color display structures: red/green/blue (RGB) micro-LEDs, and blue-LED pumped quantum dots color-conversion. For each type of display with uniform RGB chip size, our simulation results indicate that there exists an optimal LED chip size, which leads to 30–40% power saving. We then extend our model to analyze different RGB chip sizes, and find that with optimized chip sizes an additional 12% average power saving can be achieved over that with uniform chip size.
Journal of the Society for Information Display, 2021
We propose a patterned cholesteric liquid crystal (CLC) polymer film as a self‐assembled Bragg re... more We propose a patterned cholesteric liquid crystal (CLC) polymer film as a self‐assembled Bragg reflector to enhance the performance of a color‐converted micro‐light‐emitting diode (LED) display system. In the display system, we firstly optimize the device structure of blue LED chip to maintain a high light extraction efficiency and low optical crosstalk. Next, we fabricate several patterned CLC films with feature sizes ranging from 10 to 80 μm. By integrating the patterned CLC film into a color‐conversion micro‐LED display, the optical efficiency is doubled while keeping a color gamut of about 90% Rec. 2020. Finally, we carry out a proof‐of‐concept experiment to validate the functionality of such a patterned CLC film.
Micro-scale light emitting diode (micro-LED) with a chip size less than 100 μm has improved light... more Micro-scale light emitting diode (micro-LED) with a chip size less than 100 μm has improved light extraction efficiency due to increased sidewall emission. However, it causes mismatched angular distributions between AlGaInP-based red micro-LED and InGaN-based blue/green counterparts because of the epitaxial material difference. As a result, color shift of RGB micro-LED displays may become visually noticeable. To address this issue, the angular distributions of RGB micro-LEDs are analyzed theoretically and experimentally. In addition, a device structure with top black matrix and taper angle in micro-LEDs is proposed, which greatly suppresses the color shift while keeping a reasonably high light extraction efficiency.
We demonstrate a full RGB liquid crystal-tunable reflective surface where the color of the alumin... more We demonstrate a full RGB liquid crystal-tunable reflective surface where the color of the aluminum nanostructure is changed as a function of applied voltage. We then integrate the system with a TFT to depict images.
Journal of The Society for Information Display, Mar 21, 2019
A full-color micro-LED display can be achieved by red, green, and blue (RGB) chips or by a blue/u... more A full-color micro-LED display can be achieved by red, green, and blue (RGB) chips or by a blue/ultraviolet (UV) micro-LED array to pump downconverters. The latter helps relieve the burden of epitaxial growth of tri-color micro-LED chips. However, such a color-converted micro-LED system usually suffers from color crosstalk and low efficiency due to limited optical density of color converters. With funnel-tube array and reflective coating on its inner surface, the crosstalk is eliminated, and the optical efficiency can be improved by more than two times. In addition, the ambient contrast ratio is also improved because of higher light intensity. The color gamut of this device is approximately 92% of DCI-P3 standard.
We demonstrate multi-fold speed enhancement of liquid crystal phase modulators through laser writ... more We demonstrate multi-fold speed enhancement of liquid crystal phase modulators through laser written sub-micron scaffolds. The versatile fabrication process allows devices with arbitrary liquid crystal alignment and, therefore, polarization dependence. We lastly discuss the prospects of the technology for large area (>0.5 in 2) spatial light modulators.
We report two new liquid crystal mixtures with high clearing point, small visco-elastic coefficie... more We report two new liquid crystal mixtures with high clearing point, small visco-elastic coefficient and low activation energy. With overdriving and undershooting approach, the response time is less than 10ms for FFS LCDs at T=0 o C and TN at 20 o C. Therefore, these mixtures greatly improve the performances of vehicle displays at extreme environments.
We propose a novel optical design to tailor the angular distribution of a micro-LED (µLED) displa... more We propose a novel optical design to tailor the angular distribution of a micro-LED (µLED) display system and use vehicle display as an example to illustrate the design principles. The display system consists of a µLED array with a tailored LED structure, a small formfactor compound parabolic concentrator (CPC) system, and a functional engineered diffusor. It provides high efficiency, high peak brightness, and small formfactor. In the design process, a mix-level optical simulation model, including the angular distribution of polarized emission dipole (dipole emission characteristics), Fabry-Perot cavity effect (wave optics), and light propagation process (ray optics), is established to analyze the angular distribution of µLEDs. Such an optical design process from dipole emission to display radiation pattern can be extended to other µLED display systems for different applications.
A deep-dyeing strategy that can convert commercial PET polymers into luminescent perovskite-polym... more A deep-dyeing strategy that can convert commercial PET polymers into luminescent perovskite-polymer composites is demonstrated. Such composites show excellent color tunability, saturated colors, high efficiency and superior environmental stability.
Metamaterials, Metadevices, and Metasystems 2016, 2016
In this paper, we report a computational and experimental study using tunable infrared (IR) metam... more In this paper, we report a computational and experimental study using tunable infrared (IR) metamaterial absorbers (MMAs) to demonstrate frequency tunable (7%) and amplitude modulation (61%) designs. The dynamic tuning of each structure was achieved through the addition of an active material—liquid crystals (LC) or vanadium dioxide (VO2)--within the unit cell of the MMA architecture. In both systems, an applied stimulus (electric field or temperature) induced a dielectric change in the active material and subsequent variation in the absorption and reflection properties of the MMA in the mid- to long-wavelength region of the IR (MWIR and LWIR, respectively). These changes were observed to be reversible for both systems and dynamic in the LC-based structure.
Experimental evidence proves that polymer-stabilized blue phase liquid crystal is not perfectly o... more Experimental evidence proves that polymer-stabilized blue phase liquid crystal is not perfectly optically isotropic. The optical rotatory power (ORP) of double twist cylinders causes the polarization axis of the transmitted light to rotate a small angle, and leaks through the crossed polarizers. Rotating the analyzer by ~2 o to correct this ORP can improve the contrast ratio by 3X.
Molecular Crystals and Liquid Crystals, Mar 24, 2015
Since 1981, blue phase liquid crystal (BPLC) was regarded as optical isotropy and high contrast r... more Since 1981, blue phase liquid crystal (BPLC) was regarded as optical isotropy and high contrast ratio (CR) should be achieved easily. However, low CR of BPLC display was reported in all literatures. Here, we show BPLC is non-ideal optical isotropy which leads to poor CR. In our report, BPLC not only revealed primary structure of double-twist cylinder and secondary structure of lattice but also revealed tertiary structure of self-alignment on electrode surface. This finding will be useful to improve CR and inspire researches in display industry and academics.
Plasmonic structural color has recently garnered significant interest as an alternative to the or... more Plasmonic structural color has recently garnered significant interest as an alternative to the organic dyes standard in print media and liquid crystal displays. These nanostructured metallic systems can produce diffraction limited images, be made polarization dependent, and exhibit resistance to color bleaching. Perhaps even more advantageous, their optical characteristics can also be tuned, post-fabrication, by altering the surrounding media's refractive index parallel to the local plasmonic fields. A common material with which to achieve this is liquid crystal. By reorienting the liquid crystal molecules through external electric fields, the optical resonances of the plasmonic filters can be dynamically controlled. Demonstrations of this phenomenon, however, have been limited to modest shifts in plasmon resonance. Here, we report a liquid crystal-plasmonic system with an enhanced tuning range through the use of a shallow array of nano-wells and high birefringent liquid crystal. The continuous metallic nanostructure maximizes the overlap between plasmonic fields and liquid crystal while also allowing full reorientation of the liquid crystal upon an applied electric field. Sweeping over structural dimensions and voltages results in a color palette for these dynamic reflective pixels that can further be exploited to create color tunable images. These advances make plasmonic-liquid crystal systems more attractive candidates for filter, display, and other tunable optical technologies.
In addition to displays, liquid crystals (LCs) have also found widespread applications in photoni... more In addition to displays, liquid crystals (LCs) have also found widespread applications in photonic devices, such as adaptive lens, adaptive optics, and sensors, because of their responses to electric field, temperature, and light. As the fabrication technique advances, more sophisticated devices can be designed and created. In this review, we report recent advances of two-photon polymerization-based direct-laser writing enabled LC devices. Firstly, we describe the basic working principle of two-photon polymerization. With this powerful fabrication technique, we can generate anchoring energy by surface morphology to align LC directors on different form factors. To prove this concept, we demonstrate LC alignment on planar, curvilinear surfaces as well as in three-dimensional volumes. Based on the results, we further propose a novel, ultra-broadband, twisted-nematic diffractive waveplate that can potentially be fulfilled by this technique. Next, we briefly discuss the current status of direct-laser writing on LC reactive mesogens and its potential applications. Finally, we present two design challenges: fabrication yield and polymer relaxation/deformation, remaining to be overcome.
are self-assembled and no alignment layer is needed. Due to the short coherent length, BPLC achie... more are self-assembled and no alignment layer is needed. Due to the short coherent length, BPLC achieves fast response time in the submillisecond range, [23] making it attractive for many electro-optical applications that require rapid switching. Moreover, BPLC offers quasi-optically isotropic off-state for off-resonant wavelength, [24] and exhibits Kerr constant thousands of times higher than conventional Kerr media. However, blue phases (including BPI, BPII and BPIII) are only stable within a very narrow temperature range between chiral nematic and isotropic phases. [20] Great efforts were devoted to understanding the structures of blue phases, both experimentally and theoretically. [25-32] BPIII is an amorphous structure,while BPI and BPII are both cubic structures made of double twist cylinders (DTCs) but arranged differently as shown in Figure 1a. Inside each DTC, liquid crystal directors are twisted from-45 o to +45 o about any radius of the cylinder. However, as the cylinders are symmetrically arranged in three dimensions, it is impossible to make the directors match everywhere. Thus, defects occur at the points where the DTCs are in contact to relieve the elastic strain energy. As a result, blue phases only exist within a narrow temperature range (0.5-2 °C), [33] which had hindered them from practical applications for decades. Much research work has been carried out in order to broaden the temperature range of blue phases. [34-46] Among them, polymer stabilization [39] is the most commonly used method, which was first proposed by Kikuchi et al. in 2002. By selectively concentrating the cross-linked polymer network in the disclination lines, the DTC structure was stabilized with a wide temperature range over 60 K. In the early years, polymer-stabilized blue phase liquid crystal was mainly employed for display applications. With fast response time, it could enable color sequential display and triple the optical efficiency; [47] with natural self-assembly, it does not require any alignment layer; and with quasi-isotropic dark state, it could achieve high contrast ratio and wide viewing angle. In 2008, Samsung demonstrated the first PS-BPLC display prototype at Society for Information Display exhibition. [48] In 2015, AU Optronics also demonstrated a PS-BPLC display using new wall electrodes, which could be driven by conventional integrated circuit. [49] Extensive work has been done on improving PS-BPLC display performances from both material Polymer-stabilized blue phase liquid crystal (PS-BPLC) is emerging as a promising candidate for next-generation photonic applications due to its attractive features: nano-scale structure that enables sub-millisecond response time, self-assembly that eliminates the need for surface alignment, and threedimensional cubic structure so that it is quasi-isotropic without applied field. Here, we will look into the photonic properties of PS-BPLC microscopically and macroscopically, and will focus on the non-display photonic applications based on these properties. First we will give a general introduction to the polymer stabilization process, general photonic properties, electric field effects and desirable electro-optical properties of PS-BPLC. Next we will present applications based on the microscopic photonic properties in the cubic structures with double twist cylinders: photonic band gap, scattering and unwinding of the double twist structure under electric field. Then, we will cover applications based on the macroscopic refractive index change of PS-BPLC under electric fields, whose mechanisms are further classified into phase retardation, phase modulation, and resonance condition change. Finally we will look into the remaining challenges and future perspectives of PS-BPLC for photonic applications.
A novel method to achieving active refractive and diffractive liquid-crystal microlens arrays is ... more A novel method to achieving active refractive and diffractive liquid-crystal microlens arrays is demonstrated. By two-photon polymerization, liquid-crystal alignment can be directly generated on curved or planar surface and thus active microlens arrays can be created by fulfilling liquid-crystal cells. This method provides a new route toward liquid-crystal microlens arrays.
We reported a fast-response LCD for virtual reality applications. The average gray-to-gray (GTG) ... more We reported a fast-response LCD for virtual reality applications. The average gray-to-gray (GTG) response time is 0.93ms and its GTG motion-picture-response-time (MPRT) is comparable to OLED. By increasing the frame-rate and/or decreasing the backlight duty-ratio, we can achieve MPRT < 1 ms to display fastmoving objects with unnoticeable motion blurs.
We develop a patterned cholesteric liquid crystal polymer film with reflection and scattering sta... more We develop a patterned cholesteric liquid crystal polymer film with reflection and scattering states. By integrating this film into a color‐converted micro‐LED display, the optical efficiency is increased by 2.14x at 90% Rec.2020 color gamut and the average angular color shift δu'v′ is reduced from 0.03 to 0.018.
Micro-LED (light-emitting diode) is a potentially disruptive display technology, while power cons... more Micro-LED (light-emitting diode) is a potentially disruptive display technology, while power consumption is a critical issue for all display devices. In this paper, we develop a physical model to evaluate the power consumption of micro-LED displays under different ambient lighting conditions. Both power efficiency and ambient reflectance are investigated in two types of full color display structures: red/green/blue (RGB) micro-LEDs, and blue-LED pumped quantum dots color-conversion. For each type of display with uniform RGB chip size, our simulation results indicate that there exists an optimal LED chip size, which leads to 30–40% power saving. We then extend our model to analyze different RGB chip sizes, and find that with optimized chip sizes an additional 12% average power saving can be achieved over that with uniform chip size.
Journal of the Society for Information Display, 2021
We propose a patterned cholesteric liquid crystal (CLC) polymer film as a self‐assembled Bragg re... more We propose a patterned cholesteric liquid crystal (CLC) polymer film as a self‐assembled Bragg reflector to enhance the performance of a color‐converted micro‐light‐emitting diode (LED) display system. In the display system, we firstly optimize the device structure of blue LED chip to maintain a high light extraction efficiency and low optical crosstalk. Next, we fabricate several patterned CLC films with feature sizes ranging from 10 to 80 μm. By integrating the patterned CLC film into a color‐conversion micro‐LED display, the optical efficiency is doubled while keeping a color gamut of about 90% Rec. 2020. Finally, we carry out a proof‐of‐concept experiment to validate the functionality of such a patterned CLC film.
Uploads
Papers by Shin-Tson Wu