Chin Wei Sher

Bio: Chin Wei Sher is an academic researcher from Hong Kong University of Science and Technology. The author has contributed to research in topics: Light-emitting diode & Quantum dot. The author has an hindex of 11, co-authored 19 publications receiving 823 citations. Previous affiliations of Chin Wei Sher include National Chiao Tung University.

Mini-LED and Micro-LED: Promising Candidates for the Next Generation Display Technology

Abstract: Displays based on inorganic light-emitting diodes (LED) are considered as the most promising one among the display technologies for the next-generation The chip for LED display bears similar features to those currently in use for general lighting, but it size is shrunk to below 200 microns Thus, the advantages of high efficiency and long life span of conventional LED chips are inherited by miniaturized ones As the size gets smaller, the resolution enhances, but at the expense of elevating the complexity of fabrication In this review, we introduce two sorts of inorganic LED displays, namely relatively large and small varieties The mini-LEDs with chip sizes ranging from 100 to 200 μm have already been commercialized for backlight sources in consumer electronics applications The realized local diming can greatly improve the contrast ratio at relatively low energy consumptions The micro-LEDs with chip size less than 100 μm, still remain in the laboratory The full-color solution, one of the key technologies along with its three main components, red, green, and blue chips, as well color conversion, and optical lens synthesis, are introduced in detail Moreover, this review provides an account for contemporary technologies as well as a clear view of inorganic and miniaturized LED displays for the display community

Micro-light-emitting diodes with quantum dots in display technology

Abstract: Micro-light-emitting diodes (μ-LEDs) are regarded as the cornerstone of next-generation display technology to meet the personalised demands of advanced applications, such as mobile phones, wearable watches, virtual/augmented reality, micro-projectors and ultrahigh-definition TVs. However, as the LED chip size shrinks to below 20 μm, conventional phosphor colour conversion cannot present sufficient luminance and yield to support high-resolution displays due to the low absorption cross-section. The emergence of quantum dot (QD) materials is expected to fill this gap due to their remarkable photoluminescence, narrow bandwidth emission, colour tuneability, high quantum yield and nanoscale size, providing a powerful full-colour solution for μ-LED displays. Here, we comprehensively review the latest progress concerning the implementation of μ-LEDs and QDs in display technology, including μ-LED design and fabrication, large-scale μ-LED transfer and QD full-colour strategy. Outlooks on QD stability, patterning and deposition and challenges of μ-LED displays are also provided. Finally, we discuss the advanced applications of QD-based μ-LED displays, showing the bright future of this technology. Micrometre-sized light-emitting diodes (LEDs) based on quantum dots (QDs) will propel the next generation of display technologies, a review by leading researchers shows. Conventional LED designs, with phosphor coatings that convert light to different colours, are difficult to make smaller than 20 micrometres. Jr-Hau He at City University of Hong Kong and co-workers explain how this problem can be tackled using QDs, tiny particles whose optical properties can be tuned by varying their size, providing brighter and more precise colours. Ultra-high-resolution displays based on phospholuminescent QD-LEDs are now being released to the market thanks to finely-controlled methods for synthesising QDs and depositing them onto films. Further research should focus on the best ways to stabilise and protect QD films within LEDs, and to continue developing electroluminescent QD-LEDs, which could potentially outperform their phospholuminescent cousins.

Patterned structure of REMOTE PHOSPHOR for phosphor-converted white LEDs

Abstract: High efficiency white light-emitting diodes with superior color-mixing have been investigated. It is suggested that the patterned remote phosphor structure could improve the uniformity of angular-dependent correlated color temperature (CCT) and achieve high chromatic stability in wider operating current range, as compared to the conventional remote phosphor coating structure. In this experiment, we employed a pulse spray coating method to place the patterned phosphor on the package and to leave a window region. The window area, a clear space without coating of the phosphor not only increases the extraction efficiency of blue rays at large angle, but also improves the stability of angular-dependent CCT. Moreover, the CCT deviation could be reduced from 1320 K to 266 K by this patterned remote phosphor method, and the stray blue/yellow light within the package can be effectively reduced and controlled. The design was verified both experimentally and theoretically.

Full-color monolithic hybrid quantum dot nanoring micro light-emitting diodes with improved efficiency using atomic layer deposition and nonradiative resonant energy transfer

Abstract: Full-color displays based on micro light-emitting diodes (μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring (NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tuned from green to blue through strain relaxation. An Al2O3 layer was deposited on the sidewall of NR-μLEDs, which improved the photoluminescence intensity by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer, red quantum dots were printed to NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.

Efficient and Stable White LEDs with Silica-Coated Inorganic Perovskite Quantum Dots

Abstract: A white light-emitting diode (0.33, 0.33) is fabricated using perovskite quantum dot/silica composites. It is shown to have greatly improved stability.

Mini-LED, Micro-LED and OLED displays: present status and future perspectives

Abstract: Presently, liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays are two dominant flat panel display technologies Recently, inorganic mini-LEDs (mLEDs) and micro-LEDs (μLEDs) have emerged by significantly enhancing the dynamic range of LCDs or as sunlight readable emissive displays "mLED, OLED, or μLED: who wins?" is a heated debatable question In this review, we conduct a comprehensive analysis on the material properties, device structures, and performance of mLED/μLED/OLED emissive displays and mLED backlit LCDs We evaluate the power consumption and ambient contrast ratio of each display in depth and systematically compare the motion picture response time, dynamic range, and adaptability to flexible/transparent displays The pros and cons of mLED, OLED, and μLED displays are analysed, and their future perspectives are discussed

Micro-light-emitting diodes with quantum dots in display technology

Abstract: Micro-light-emitting diodes (μ-LEDs) are regarded as the cornerstone of next-generation display technology to meet the personalised demands of advanced applications, such as mobile phones, wearable watches, virtual/augmented reality, micro-projectors and ultrahigh-definition TVs. However, as the LED chip size shrinks to below 20 μm, conventional phosphor colour conversion cannot present sufficient luminance and yield to support high-resolution displays due to the low absorption cross-section. The emergence of quantum dot (QD) materials is expected to fill this gap due to their remarkable photoluminescence, narrow bandwidth emission, colour tuneability, high quantum yield and nanoscale size, providing a powerful full-colour solution for μ-LED displays. Here, we comprehensively review the latest progress concerning the implementation of μ-LEDs and QDs in display technology, including μ-LED design and fabrication, large-scale μ-LED transfer and QD full-colour strategy. Outlooks on QD stability, patterning and deposition and challenges of μ-LED displays are also provided. Finally, we discuss the advanced applications of QD-based μ-LED displays, showing the bright future of this technology. Micrometre-sized light-emitting diodes (LEDs) based on quantum dots (QDs) will propel the next generation of display technologies, a review by leading researchers shows. Conventional LED designs, with phosphor coatings that convert light to different colours, are difficult to make smaller than 20 micrometres. Jr-Hau He at City University of Hong Kong and co-workers explain how this problem can be tackled using QDs, tiny particles whose optical properties can be tuned by varying their size, providing brighter and more precise colours. Ultra-high-resolution displays based on phospholuminescent QD-LEDs are now being released to the market thanks to finely-controlled methods for synthesising QDs and depositing them onto films. Further research should focus on the best ways to stabilise and protect QD films within LEDs, and to continue developing electroluminescent QD-LEDs, which could potentially outperform their phospholuminescent cousins.

Thermal management of LEDs: Package to system

Abstract: Light emitting diodes, LEDs, historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards general illumination. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the developments of LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 lumens/W, this is approximately 6 times the efficiency of a conventional incandescent tungsten bulb. Thermal management for the solid-state lighting applications is a key design parameter for both package and system level. Package and system level thermal management is discussed in separate sections. Effect of chip packages on junction to board thermal resistance was compared for both SiC and Sapphire chips. The higher thermal conductivity of the SiC chip provided about 2 times better thermal performance than the latter, while the under-filled Sapphire chip package can only catch the SiC chip performance. Later, system level thermal management was studied based on established numerical models for a conceptual solid-state lighting system. A conceptual LED illumination system was chosen and CFD models were created to determine the availability and limitations of passive air-cooling.