The effect of atomic-layer deposition (ALD) sidewall passivation on the enhancement of the electrical and optical efficiency of micro-light-emitting diode (µ-LED) is investigated. Various blue light ...µ-LED devices (from 5 × 5 µm
2
to 100 × 100 µm
2
) with ALD-Al
2
O
3
sidewall passivation were fabricated and exhibited lower leakage and better external quantum efficiency (EQE) comparing to samples without ALD-Al
2
O
3
sidewall treatment. Furthermore, the EQE values of 5 × 5 and 10 × 10 µm
2
devices yielded an enhancement of 73.47% and 66.72% after ALD-Al
2
O
3
sidewall treatments process, and the output power also boosted up 69.3% and 69.9%. The Shockley-Read-Hall recombination coefficient can be extracted by EQE data fitting, and the recombination reduction in the ALD samples can be observed. The extracted surface recombination velocities are 551.3 and 1026 cm/s for ALD and no-ALD samples, respectively.
We propose and experimentally demonstrate an indoor positioning system which combines identity positioning and the radio frequency carrier allocation technique in order to reduce the signal ...interference from nearby light-emitting diodes (LEDs) and improve the accuracy of positioning. In addition, the solar cell is used as an optical receiver for the visible light positioning system. Due to the benefits of solar cells such as low-cost, high light sensitivity, and ease in integration with wearable devices, the proposed system could be an energy-efficient and environmentally friendly choice for indoor positioning in the future.
The investigation explores the factors that influence the long-term performance of high-power 1
W white light emitting diodes (LEDs). LEDs underwent an aging test in which they were exposed to ...various temperatures and electrical currents, to identify both their degradation mechanisms and the limitations of the LED chip and package materials. The degradation rates of luminous flux increased with electrical and thermal stresses. High electric stress induced surface and bulk defects in the LED chip during short-term aging, which rapidly increased the leakage current. Yellowing and cracking of the encapsulating lens were also important in package degradation at 0.7
A/85
°C and 0.7
A/55
°C. This degradation reduced the light extraction efficiency to an extent that is strongly related to junction temperature and the period of aging. Junction temperatures were measured at various stresses to determine the thermal contribution and the degradation mechanisms. The results provided a complete understanding of the degradation mechanisms of both chip and package, which is useful in designing highly reliable and long-lifetime LEDs.
In this letter, we report on the fabrication and photovoltaic characteristics of p-i-n GaN/InGaN thin-film solar cells. The thin-film solar cells were fabricated by removing sapphire using a laser ...lift-off technique and, then, transferring the remaining p-i-n structure onto a Ti/Ag mirror-coated Si substrate via wafer bonding. The mirror structure is helpful to enhance light absorption for a solar cell with a thin absorption layer. After the thin-film process for a conventional sapphire-based p-i-n solar cell, the device exhibits an enhancement factor of 57.6% in current density and an increment in conversion efficiency from 0.55% to 0.80%. The physical origin for the photocurrent enhancement in the thin-film solar cell is related to multireflection of light by the mirror structure.
The purpose of this study is to investigate the thermal behavior at the die-attached interfaces of flip-chip GaN high-power light emitting diodes (LEDs) using a combination of theoretical and ...experimental analyses. The results indicate that contact thermal resistance increased dramatically at the die-attached interfaces with aging time and stress, degrading the luminous flux. The junction temperature and thermal uniformity of the flip-chip structure both strongly depend on the arrangement of gold bumps. Local hot spots effectively reduce light output under high electric and thermal stress, influencing the long-term performance of the LED device. The results were validated using finite element analysis and in experiments using an infrared and an emission microscope. A two-step thermal transient degradation mode was identified under various aging stresses. A simulation further optimized the bump configuration that was associated to yield a low junction temperature and high temperature uniformity of the LED chip. Accordingly, the results are helpful in enhancing the performance and reliability of high-power LEDs.
In this letter, InGaN-based solar cells with a p-InGaN/i-InGaN/n-GaN double-heterojunction structure were fabricated and characterized. Two kinds of sapphire substrates i.e., a conventional sapphire ...substrate (CSS) and a patterned sapphire substrate (PSS) were used for epitaxial growth. Both the solar cells grown on the CSS and the PSS demonstrated a high open-circuit voltage of 2.05 and 2.08 V, respectively. However, the short-circuit current of the solar cells grown on the PSS showed an improvement of 27.6% compared with that of the cells grown on the CSS. Such observation could be attributed to low edge-dislocation density and the increase in the light-absorption path by the scattering of interface incident light between the substrate and the epitaxial layer for the solar cell grown on the PSS.
We report on improved device performance of flip-chip (FC) GaN-based light-emitting diodes (LEDs) by combining patterned sapphire substrate (PSS) and thin-film techniques. It was found that an FC LED ...grown on a conventional planar sapphire exhibits a power enhancement factor of only 36.3% after the thin-film processes of substrate removal and surface roughening. In contrast, the as-fabricated FC LED grown on a PSS showed a power enhancement factor of up to 62.3% without any postprocess as compared with the light output power of an original conventional FC LED. Further intensity improvement to 74.4% could be achieved for the FC LED/PSS sample with the thin-film processes.
Textured n-GaN/i-InGaN/p-GaN solar cells with interdigitated imbedded electrodes (IIEs) eliminating the electrode-shading loss have been investigated. In the absence of the electrode-shading effect, ...the optimized textured solar cell exhibits a conversion efficiency of 1.03%, which is 78% and 47% higher than those of the conventional structure and the structure with mirror coated on silicon substrate with electrode shading, respectively. The short-circuit current density of this textured HE device is about 0.65 mA/cm 2 , which is 71% and 44% higher than those of the two compared structures, respectively.
AIM To identify whether chitinase 3-like 1(CHI3 L1) serves as a suitable biomarker for the prognosis of esophageal squamous cell carcinoma(ESCC) and to analyze this protein’s cellular source.METHODS ...An ELISA was conducted to detect the concentration of CHI3 L1 in the serum of 150 ESCC patients diagnosed between January 2001 and February 2005. The prognostic relevance of CHI3 L1 was evaluated by a Kaplan-Meier and Cox regression analysis. The immunohistochemistry was reanalyzed,and fluorescent staining was utilized to explore the cellular origins of CHI3 L1. We stimulated monocyte-derived macrophages(MDMs) with either IL-6 or the supernatant of the ESCC cell line Eca-109 and later investigated the level of CHI3 L1 by q PCR and ELISA.RESULTS The level of serum CHI3 L1 was higher in older patients(≥ 60) than in patients under the age of 60(P = 0.001). The patients with higher levels of CHI3 L1 had a significantly shorter overall survival,whereas the traditional markers,carcinoembryonic antigen and squamous cell carcinoma antigen,were less effective(P > 0.05). A multivariate Cox analysis(P = 0.001) indicated that CHI3 L1 was an independent prognostic factor for ESCC patients. Peritumoral macrophages in ESCC exhibited high levels of CHI3 L1. Interleukin-6(IL-6) and the supernatant of Eca-109 containing IL-6 stimulated MDMs to secrete CHI3 L1. The serum concentration of CHI3 L1 in the ESCC patients showed a weak correlation with the laboratory inflammatory parameters neutrophil(NEU,P = 0.045),neutrophil/lymphocyte rate(NLR,P = 0.016),and C-reactive protein(CRP,P < 0.001).CONCLUSION Our study first established a connection between the pretreated CHI3 L1 and patients with ESCC,and the serum CHI3 L1 was primarily secreted by ESCC-surrounded macrophages.
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