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Small‐size pixels and high efficiency under low injection levels are required for high‐resolution microdisplay. Efficient blue InGaN micro‐light‐emitting diodes (μLEDs) with 5 μm diameter are fabricated using AuSn flip‐chip bonding, high reflection electrodes, and large‐area N electrodes surrounding the mesas. The peak external quantum efficiency (EQE) measured in an integrating sphere is as high as 13.67% at a current density of 5.4 A cm−2. Moreover, at a current density of 0.1 A cm−2, EQE can still reach 11.69%. The electrical efficiency approaches 1, and the differential slope of log L versus log I is close to 1 at low current density. These results suggest significant progress in exploring high‐efficiency 5 μm InGaN blue μLEDs. [ABSTRACT FROM AUTHOR]

Trench defects in multi‐quantum wells (MQWs) have been considered as flawed structures that severely degraded the internal quantum efficiency (IQE) of light‐emitting diodes (LEDs) in the past. In this research, trench defects are innovatively utilized to enhance the efficiency of red InGaN LEDs. Specifically, dual‐color MQWs structures are applied to modulate trench defects. The upper red MQWs, grown on top of green MQWs with a high density of trench defects, exhibit a significant wavelength redshift of 68 nm and ≈ 6‐fold luminescence enhancement compared to those without intentionally introduced trench defects. Red InGaN LEDs with an IQE of 16.4% are achieved with this epitaxy growth strategy. Such wavelength redshift is attributed to the more indium incorporation due to the strain relaxation effect of trench defects. Moreover, the luminescence enhancement originates from the strong emission of the red MQWs inside trench defects, mainly attributed to strain relaxation and defect shielding by the wide and deep trenches. Achieving red emission by modulating trench defects is simple and reproducible without requiring additional substrate designs, which provides a novel way toward high‐efficiency red InGaN LEDs. [ABSTRACT FROM AUTHOR]

Combined simulation and test to investigate the collapse failure mode and energy absorption characteristics of wingding carbon fiber reinforced composite（CFRP[± 45°/90°]）/Al hybrid thin-walled circular tube under quasi-static axial compression load. Failure mode,Load-displacement curves and energy absorption characteristics were obtained under quasi-static axial crushing tests. A finite element model of hybrid tube was established according to samples. The simulation results with good agreement with the test were obtained by ABAQUS/Explicit,and the crushing failure behavior of the hybrid tube under quasistatic load was reproduced. Based on the simulation results,it was found that the initial crushing load,average crushing load,specific energy absorption and load efficiency of the mixing tube were increased by 97. 6%,93. 3%,57. 8% and 5. 9%,respectively. compared with the aluminum tube. The staged peaks and valleys of the crushing load were selected to analyze the shape of hybrid tube and the failure state of the fiber damage. The results show that when the hybrid tube is complete the fiber plays the main bearing role. In the crushing failure stage,the fiber damage failure mode changes with fiber winding angle,the crushing morphology of aluminum tube and the bonding interface state of CFRP/Al. Subsequently,the energy absorption characteristics of CFRP/Al hybrid circular tubes with three different structure forms were compared. It was found that hybrid circular tube with CFRP[90°/± 45°] wrapped the outside of the aluminum has the best energy absorption.

We fabricated amorphous photonic structures (APSs) with different periods and hole diameters. The GaN-based white light emitting diodes (LEDs) at nominal correlated color temperatures (CCTs) of 5000 and 6000 K were surface mounted by these APSs. The electroluminescence (EL) measurements showed less luminous efficiency (LE) and higher CCT than the ones of the virginal white LEDs. However, the LEs of many APS-mounted white LEDs increased compared to white the LEDs without APSs at the same CCTs. A finite-difference time-domain (FDTD) simulation was carried out on the ASPs surface-mounted white LEDs and bidirectional scattering distribution functions (BSDFs) of different emissions were transferred to a Monte Carlo ray tracing simulation. The simulated LEs and CCTs conformed well to the experimental ones. The effects of the blue emission transmission and phosphor concentration were simulated to predict the absolute LE enhancement methods for white LEDs. At last, the hopeful APSs for high Les' general lighting were discussed. [ABSTRACT FROM AUTHOR]

To improve the crashworthiness and reduce vehicle weight, a crash box made of carbon fiber reinforced plastics (CFRP)/aluminum (Al) hybrid materials was introduced in the paper. Quasistatic axial compression tests and numerical simulations were conducted for pure Al tubes and CFRP/Al hybrid tubes. The simulation models were validated and were further employed to investigate the effects of geometry, aluminum tube thickness, fiber wrapping angle and CFRP layers on the crashworthiness of the hybrid crash box under axial loading and 30° oblique collision. The multiobjectives were taken to obtain the optimal geometrical dimensions, aluminum tube thickness, wrapping angle, and the number of layers. The crashworthiness of the optimal CFRP/Al hybrid crash box was compared with that of original aluminum crash box. It was found that the mass of the crash box was reduced by 35.21%, while the specific energy absorption (SEA) and mean crushing force (Fmean) were increased by more than 18% and 46%, respectively. The paper was aimed to provide some references for the design and optimization of composite crash box. [ABSTRACT FROM AUTHOR]