Improving Optical Efficiency and Luminance of GaN-Based Micro-Light-Emitting Diodes for High-Resolution Displays via NH Plasma Pretreatment.

GaN-based micro-light-emitting diodes (Micro-LEDs) are regarded as promising light sources for near-eye-display applications such as augmented reality/virtual reality (AR/VR) displays due to their high resolution, high brightness, and low power consumption. However, the application of Micro-LEDs in high-pixel-per-inch (PPI) displays is constrained by the drop in efficiency caused by sidewall defects in small-sized devices. In this study, a process method involving NH plasma pretreatment to reduce sidewall defects is proposed and investigated for enhancing the external quantum efficiency (EQE) of small-sized devices.

Color-conversion displays: current status and future outlook.

The growing focus on enhancing color quality in liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) has spurred significant advancements in color-conversion materials. Furthermore, color conversion is also important for the development and commercialization of Micro-LEDs. This article provides a comprehensive review of different types of color conversion methods as well as different types of color conversion materials.

A Photolithography-Free Fabrication Strategy for Perovskite Photodetector Array with High-Security Imaging Application.

Metal halide perovskites have attracted significant attention for high-performance and cost-effective photodetector (PD) arrays in recent years. Traditional perovskite photodetector arrays typically rely on planar structure and photolithography, which limit resolution and involve complex, costly processes. To address these challenges, an innovative, lithography-free fabrication strategy is proposed utilizing direct laser writing ablation and a surface energy-assisted selective growth process.

Identifying the role of carrier overflow and injection current efficiency in a GaN-based micro-LED efficiency droop model.

In this paper, we investigate the efficiency droop phenomenon in green and blue GaN-based micro-LEDs of various sizes. We discuss the distinct carrier overflow performance in green and blue devices by examining the doping profile extracted from capacitance-voltage characterization. By combining the size-dependent external quantum efficiency with the ABC model, we demonstrate the injection current efficiency droop.

Design of a high-speed circular polarization converter with a large field of view and wavelength range.

A high-speed circular polarization converter (CPC) with a wide field of view (FOV) and wavelength range is designed and fabricated in this paper. The multi-waveplate combined structure is applied to constitute the basic configuration of the CPC for broadening the wavelength range. An electrically suppressed helix ferroelectric liquid crystal (ESHFLC) material with fast response is used as a medium for dynamic polarization operation.

Flexible and wide-range tuning of liquid crystal polarization grating period based on single and interference-free exposure.

We propose a period control method of liquid crystal polarization grating (LCPG) based on an nterference-free and single exposure process. By adjusting three parameters of exposure setup, including incident angle of exposure beam, wedge angle of birefringent prism and tilt angle of the sample, polarization distribution of the exposure beam is changed. The spatially variant polarization of the exposure beam is transferred to liquid crystal (LC) molecules by an azo-dye photo-sensitive layer.

Lattice strain modulation toward efficient blue perovskite light-emitting diodes.

The successful implementation of perovskite light-emitting diodes (PeLEDs) in advanced displays and lighting has proven to be challenging because of the inferior performance of blue devices. Here, we point out that a strained system would lead to the quasi-degenerate energy state to enhance the excited-state transition due to the formation of double-polarized transition channel. The tensile strained structure also brings about a synergetic control of the carrier dynamics in virtue of lattice structure deformation and reduced dimensional phase regulation to promote carrier population in large bandgap domains and to realize near-unit energy transfer from the large bandgap phases to the emitter phases.

Compact Integration of Hydrogen-Resistant a-InGaZnO and Poly-Si Thin-Film Transistors.

The low-temperature poly-Si oxide (LTPO) backplane is realized by monolithically integrating low-temperature poly-Si (LTPS) and amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) in the same display backplane. The LTPO-enabled dynamic refreshing rate can significantly reduce the display's power consumption. However, the essential hydrogenation of LTPS would seriously deteriorate AOS TFTs by increasing the population of channel defects and carriers.

Ionic liquid multistate resistive switching characteristics in two terminal soft and flexible discrete channels for neuromorphic computing.

By exploiting ion transport phenomena in a soft and flexible discrete channel, liquid material conductance can be controlled by using an electrical input signal, which results in analog neuromorphic behavior. This paper proposes an ionic liquid (IL) multistate resistive switching device capable of mimicking synapse analog behavior by using IL BMIM FeCL and HO into the two ends of a discrete polydimethylsiloxane (PDMS) channel. The spike rate-dependent plasticity (SRDP) and spike-timing-dependent plasticity (STDP) behavior are highly stable by modulating the input signal.

Stokes Shift in Inorganic Lead Halide Perovskites: Current Status and Perspective.

Inorganic metal halide perovskite system is considered as a promising candidate for applications from display to biomedical industry. Intrinsic inorganic lead halides possess small Stokes shift or self-absorption, providing negative impact for both photo voltaic and biomedical applications. Therefore, the development of an inorganic halide perovskite system with large Stokes shift is a significant venture.

Investigation of Enhanced Ambient Contrast Ratio in Novel Micro/Mini-LED Displays.

In recent years, ambient contrast ratio (ACR) has become very critical for advanced outdoor displays, including transparent displays, portable displays, and so on. In this work, the ACR of typical flat panel displays was introduced, while LED-based displays showed distinctive advantages. Micro-LED displays with a different pitch of 10 μm, 15 μm, 30 μm, and 60 μm were fabricated and characterized.

Ferroelectric liquid crystal Pancharatnam-Berry lens with a fast control of output light's polarization-handedness.

We report the ferroelectric liquid crystal (FLC) Pancharatnam-Berry lenses (PBLs) with rapid transmittance tunability. The FLC PBLs were fabricated using a single-step holographic exposure system based on a spatial light modulator working as numerous polarization retarders, providing a simple way to fabricate FLC continuous aligning structures. A state-selection sector containing a binary FLC switch was utilized for fast changing input light's polarization handedness.

Humidity sensor based on Gallium Nitride for real time monitoring applications.

Gallium Nitride (GaN) remarkably shows high electron mobility, wide energy band gap, biocompatibility, and chemical stability. Wurtzite structure makes topmost Gallium atoms electropositive, hence high ligand binding ability especially to anions, making it usable as humidity sensor due to water self-ionization phenomenon. In this work, thin-film GaN based humidity sensor is fabricated through pulse modulated DC magnetron sputtering.

Fast-switchable, high diffraction-efficiency ferroelectric liquid crystal Fibonacci grating.

Low-voltage fast switchable 1D and 2D Fibonacci grating (FbG), using an electrically suppressed helix ferroelectric liquid crystal (ESHFLC), with high diffraction efficiency for a super-resolution imaging system in far-field are disclosed in this paper. Specifically, the polarization-independent two-domain (0, π) structure is well designed based on photoalignment technology to maximize the total diffraction efficiency that can reach 97.4% (1st order:8.

Tribo-Induced Smart Reflector for Ultrasensitive Self-Powered Wireless Sensing of Air Flow.

Air-flow sensing is essential in broad applications of weather forecasting, ocean monitoring, gas leakage alarming, and health monitoring. However, in severe environments where electrical power supply and cable connection are not available, the sensing of air flow in a self-powered way is a challenging issue. In this work, we reported a tribo-induced smart reflector to achieve the self-powered wireless sensing of the air flow by combining an aerodynamics-driven triboelectric nanogenerator (TENG) and a silver-coated polymer network liquid crystal.

Fast refocusing lens based on ferroelectric liquid crystals.

Optical devices like virtual reality (VR) headsets present challenges in terms of vergence-accommodation conflict that leads to visual fatigue for the user over time. Lenses available to meet these challenges include liquid crystal (LC) lenses, which possess a response time in the millisecond range. This response time is slow, while accessing multiple focal lengths.

Voltage-controlled liquid crystal Pancharatnam-Berry phase lens with broadband operation and high photo-stability.

Pancharatnam-Berry phase optical elements (PBOEs) have received much attention due to their ability to generate complex structured light or to manipulate the shape of a light beam. This work demonstrates a tunable liquid crystal (LC) Pancharatnam-Berry (LCPB) lens using a simple and cost-effective PB phase hologram optical setup and thermal polymerization to form an irreversible photo-patterning alignment layer. The LCPB lens with high photo-stability supports ultra-broadband operation and provides a diffraction efficiency of ∼90 throughout the visible spectral range, achieved by applying the appropriate voltages.

Introducing Ion Migration and Light-Induced Secondary Ion Redistribution for Phase-Stable and High-Efficiency Inorganic Perovskite Solar Cells.

Inorganic halide perovskites have been demonstrated as a promising alternative for light absorption because of their improved thermal stability compared with organic-inorganic halide perovskites. However, low power conversion efficiency and phase instability are major hindrances to their application. Here, a straightforward approach, by adding a layer of CsBr on the top of CsPbI, is reported for high-efficiency and phase-stable CsPbI-based solar cells.

Low-driving-voltage, polarizer-free, scattering-controllable liquid crystal device based on randomly patterned photo-alignment.

In this work, a polarizer-free, electrically tunable liquid crystal device is presented. This device is based on randomly patterned photo-aligned boundaries generating light scattering in an adjacent liquid crystal film. Its transparent on state requires only 7.

Investigation of Electrical Properties and Reliability of GaN-Based Micro-LEDs.

In this paper, we report high-performance Micro-LEDs on sapphire substrates, with pixel size scaling to 20 µm and an ultra-high current density of 9902 A/cm. The forward voltages (V) of the devices ranged from 2.32 V to 2.

Normally Transparent Tribo-Induced Smart Window.

Self-powered smart windows are desirable with the expectations of their energy-saving, weather-independent, user-controllable, and miniature performance. Recently developed solar- or thermal-powered smart windows largely depend on the weather conditions and have an extremely slow response, and only a certain portion of the saved energy can be utilized by the external circuit for mode conversion. In this work, a self-powered normally transparent smart window was developed by the conjunction of a rotary freestanding sliding triboelectric nanogenerator (RFS-TENG) and a polymer network liquid crystal (PNLC) cell.

Interference-free and single exposure to generate continuous cycloidal alignment for large-area liquid crystal devices.

An approach for generating cycloidal pattern of liquid crystal (LC) molecules based on interference-free and single exposure is illustrated. The spatial manipulation of polarization state is achieved using birefringent prism and wave plates. And then, the spatially variant polarization of exposure beam is transferred to LC molecules by azo-dye photo-sensitive layer.

Two-dimensional liquid crystal polarization grating via linearly polarized light modified multi-beam polarization interferometry.

Holographic lithography is widely used as an effective approach for two-dimensional (2D) photonic crystal fabrication. However, for the fabrication of 2D polarization structures based on photoaligned liquid crystals (LCs), holographic lithography method is limited. The fabrication requires full coverage of light intensity, 2D chiral distribution and continuously varying polarization direction, which could be hardly guaranteed by multi-beam interference of circularly polarized light (CPL).

Polarization-independent nematic liquid crystal phase modulator based on optical compensation with sub-millisecond response.

In this paper, we propose a design utilizing two identically parallel-aligned nematic liquid crystal (LC) plates for fast-response and polarization-independent phase modulator. Driven by synchronized voltage signals, such a polarizer-free variable phase modulator shows a wide tunable range from zero to more than 3π, back and forth at 532nm. Due to the optical compensation of the two plates, the rise and fall time of the phase retardation corresponds to the switching-on time of the two plates.