Chin-Wei Sher’s research while affiliated with Foxconn Electronics and other places

In this paper, the fabrication and the corresponding performance characteristics of resonant cavity micro-light-emitting diodes (RC-µ-LEDs) are examined, with particular emphasis placed on reducing the light emission angle to enhance their application efficiency. A stepped quantum well structure and a multilayer aperture distributed Bragg reflector (DBR) are used to reduce the light emission angle, and two different approaches are investigated: one is by adding a multilayer DBR structure, and the other is by incorporating a microlens (ML) structure. The experimental results show that both adjusting the DBR cycles and adding microlenses can effectively reduce the dispersion angle of light emission, and thus improving the directionality of light, wavelength stability, and the overall device performance. Such highly directional light sources offer great solutions for optical communications, micro-LEDs, and augmented reality (AR) applications.

In this study, we investigated the characteristic difference between the two different configurations of the three-dimensional shell–core nanorod LED. We achieve a degree of polarization of 0.545 for tip-free core–shell nanorod LED and 0.188 for tip core–shell nanorod LED by combining the three-dimensional (3D) structure LED with photonic crystal. The ability of low symmetric modes generated by photonic crystals to enhance degree of polarization has been demonstrated through simulations of photonic crystals. In addition, light confinement in GaN-based nanorod structures is induced by total internal reflection at the GaN/air interface. The combination of 3D core–shell nanorod LED and photonic crystals cannot only produce a light source with a high degree of polarization, but also a narrow divergence angle up to 56°. These 3D LEDs may pave the way for future novel optoelectronic components.

In this study, we demonstrate a new design of white light-emitting diode (WLED) with high stability and luminous efficiency as well as positive aging. Colloidal ternary Zn0.8Cd0.2S (named Zn0.8) white quantum dots (WQDs) were prepared by chemical route and dispersed in xylene, integrating them into an ultraviolet light-emitting diode (UV-LED) to form WQD-white light emitting diode (WQD-WLED). High efficiency, high color quality and excellent reliability of WQD-WLED with neutral white correlated color temperature (CCT) can be obtained. The experimental results indicate that the stability of relative luminous efficiency and color rendering index (CRI) of the WQD-WLED can reach up to 160 and 82%, respectively. Moreover, the WQD-WLED can operate more than 1000 h under 100 mA, and the quantity of WQDs in the glass package can be reduced.

Quantum dots (QDs)‐based color‐conversion micro‐LED displays require simple and cost‐effective technology to remove blue excitation light. We demonstrate a simple process to remove the residual blue light from the color conversion layer by using QDs inkjet printing. It is found that the printed QDs films with the thickness of a few μm can effectively remove the blue excitation light as well as working as the color‐conversion layer.

We study the thermal distribution of a flexible/transparent unpackaged 32×32 micro‐LED array on PET substrate up to a brightness rating of 5,000 nits at room temperature. The temperature variation of single pixel is 3‐4 °C. The average temperatures of the array range from 30°C to 41 °C, showing stable performance.

Temperature‐dependent electrical characteristics and voltages (dVf/dT) of AlGaInP Micro‐LEDs were investigated. The J‐V curves of the Micro‐LEDs indicate the existence of a big resistance. The measured (dVf/dT) was ‐3 mV/K, which is higher than the expected value in Shockley model. This was attributed to a resistance, leading to higher temperature sensitivity.

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.

Micro light-emitting diode (micro-LED) display, mainly based on inorganic GaN-based LED, is an emerging technique with high contrast, low power consumption, long lifetime and fast response time compared to liquid crystal display (LCD) and organic light-emitting diode (OLED) display. Therefore, many research institutes and companies have conducted in-depth research on micro-LED in the full-colour display, gradually realizing the commercialization of micro-LED. And the current research results of micro-LED indicate that it can be widely used in display, visible light communication (VLC), biomedicine and other fields. Although micro-LED has broad commercial prospects, it still faces great challenges, such as the effect of size reduction on performance, the realization of high-density integration on a single wafer for independent addressing of full-colour micro-LED display, the improvement of repair technique and yield, et al. This paper reviews the key solutions to the technical difficulties of the full-colour micro-LED display. Specifically, this review analyzes and discusses a variety of advanced full-colour micro-LED display techniques with a focus on three aspects: growth technique, transfer printing technique and colour conversion technique. This review demonstrates the opportunities, progress and challenges of these techniques, aiming to guide the development of full-colour micro-LED display.

Polarizers play a key role in generating polarized light for display, imaging, and data communication, but adoption often suffers from high optical loss. Recently, due to superior optoelectronic properties, halide perovskites have been widely developed for lighting applications; however, highly polarized emission (polarization degree >0.8) has not yet been realized with perovskites. Herein, by incorporating inkjet printing and an anodic aluminum oxide (AAO) confinement strategy, highly ordered perovskite nanowire (NW) arrays are demonstrated for anisotropic optical applications. The optical device based on perovskite NW arrays reveals a high photoluminescence external quantum efficiency of 21.6% and emits highly polarized light with polarization degree up to 0.84. The highly polarized emission from perovskite NW arrays has potential to considerably reduce the optical loss of polarizers, which may attract great interest in developing polarized light sources for next‐generation optoelectronic applications.