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A wide-beam microstrip patch antenna and antenna array ranging from 77 to 81 GHz are presented in this study for millimeter-wave applications. A substrate-integrated-waveguide probe-fed patch was developed. For beamwidth enhancement, two I-shaped parasitic elements were placed next to the main patch to establish a three-element subarray. The current directions of the parasitic elements were opposite to that of the main patch, leading to beamwidth enhancement in the $E$ -plane radiation pattern. The proposed I-shaped parasitic element has the advantages of coplanar structure, compact size, and easy adjustment of the induced current. An array-factor method was employed to analyze the effect of the parasitic elements on the beamwidth of the main patch. Three amplitude distributions of the subarray were compared. The distribution of −0.1:1:−0.1 was proved to present the most beamwidth, which can be realized easily by the proposed I-shaped parasitic elements. To achieve both wide beamwidth and high gain, a $1\times8$ patch antenna array with the I-shaped parasitic elements was proposed. The measured results showed that the design can offer a gain of 10.74 dBi and a wide beamwidth of 138° at 79 GHz.

Cu2ZnSnS4 (CZTS) is a promising material for cost-effective thin film solar cells since its suitable band gap energy and large absorption coefficient in visible light region. In this study, we develop a multi-stage hot-pressing process to make a CZTS target, and conduct a pulsed laser deposition to prepare the CZTS thin film. The CZTS target and thin films have been studied to evaluate their properties as an absorption material for the thin film solar cells. Images and composition analysis from electron probe X-ray micro analyzer confirm the porosity and atomic composition of the hot-pressed CZTS target. The X-ray diffraction pattern indicates a better crystallinity of CZTS thin film after annealing at a higher temperature. Analysis from UV–vis spectroscopy on the annealed CZTS thin films suggests a large absorption coefficient in the visible light region and a band gap energy of 1.45 eV.

Microglia are the first source of a neuroinflammatory cascade, which seems to be involved in every phase of stroke-related neuronal damage. Two weeks after transient middle cerebral artery occlusion (MCAO), vehicle-treated rats displayed higher numbers of total ionized calcium-binding adaptor molecule 1 (Iba-1)-positive cells, greater cell body areas of Iba-1-positive cells, and higher numbers of hypertrophic Iba-1-positive cells (with a cell body area over 80 μm2) in the ipsilateral ischemic brain regions including the frontal cortex, striatum, and parietal cortex. In addition, MCAO decreased the number of migrating neuroblasts (or DCX- and 5-ethynyl-2′-deoxyuridine-positive cells) in the cortex, subventricular zone, and hippocampus of the ischemic brain, followed by neurological injury (including brain infarct and neurological deficits). Intravenous administration of human umbilical cord–derived mesenchymal stem cells (hUC-MSCs; 1 × 106 or 4 × 106) at 24 h after MCAO reduced neurological injury, decreased the number of hypertrophic microglia/macrophages, and increased the number of newborn neurons in rat brains. Thus, the accumulation of hypertrophic microglia/macrophages seems to be detrimental to neurogenesis after stroke. Treatment with hUC-MSCs preserved adult newborn neurons and reduced functional impairment after transient cerebral ischemia by reducing the number of hypertrophic microglia/macrophages.

Both brain-derived neurotrophic factor (BDNF) and microglia activation are involved in the pathogenesis of ischemic stroke. Herein, we attempt to ascertain whether Calycosin, an isoflavonoid, protects against ischemic stroke by modulating the endogenous production of BDNF and/or the microglia activation. This study was a prospective, randomized, blinded and placebo-controlled preclinical experiment. Sprague-Dawley adult rats, subjected to transient focal cerebral ischemia by middle cerebral artery occlusion (MCAO), were treated randomly with 0 (corn oil and/or saline as placebo), 30 mg/kg of Calycosin and/or 1 mg/kg of a tropomyosin-related kinase B (TrkB) receptor antagonist (ANA12) at 1 h after reperfusion and once daily for a total of 7 consecutive days. BDNF and its functional receptor, full-length TrkB (TrkB-FL) levels, the percentage of hypertrophic microglia, tumor necrosis factor-α (TNF-α)-containing microglia, and degenerative and apoptotic neurons in ischemic brain regions were determined 7 days after cerebral ischemia. A battery of functional sensorimotor test was performed over 7 days. Post-stroke Calycosin therapy increased the cerebral expression of BDNF/TrkB, ameliorated the neurological injury and switched the microglia from the activated amoeboid state to the resting ramified state in ischemic stroke rats. However, the beneficial effects of BDNF/ TrkB-mediated Calycosin could be reversed by ANA12. Our data indicate that BDNF/TrkB-mediated Calycosin ameliorates rat ischemic stroke injury by switching the microglia from the activated amoeboid state to the resting ramified state. Graphical abstract.

A new 5T2C pixel circuit is proposed in this study to compensate TFT Vth variation, power line IR-drop, and OLED degradation in LTPS PMOS process and it also has The Close Loop Negative Feedback Method (CL-NFM) to compensate the gate voltage distortion of the driving TFT during the emission phase. The simulation showed that the emission current error are 4.85%, 9.02% and 39.25% separated for high, middle and low grey level compared between the current value in 1ms and 16ms, which is 12.51%, 38.14% and 97.8% for the conventional pixel structure, respectively.

The issue of potential-induced degradation (PID) has gained more concerns due to causing the catastrophic failures in photovoltaic (PV) modules. One of the approaches to diminish PID is to modify the anti-reflection coating (ARC) layer upon the front surface of crystalline silicon solar cells. Here, we focus on the modification of ARC films to realize PID-free step-by-step through three delicate experiments. Firstly, the ARC films deposited by direct plasma enhanced chemical vapor deposition (PECVD) and by indirect PECVD were investigated. The results showed that the efficiency degradation of solar cells by indirect PECVD method is up to −33.82%, which is out of the IEC 62804 standard and is significantly more severe than by the direct PECVD method (−0.82%). Next, the performance of PID-resist for the solar cell via indirect PECVD was improved significantly (PID reduced from −31.82% to −2.79%) by a pre-oxidation step, which not only meets the standard but also has higher throughput than direct PECVD. Lastly, we applied a novel PECVD technology, called the pulsed-plasma (PP) PECVD method, to deal with the PID issue. The results of the HF-etching rate test and FTIR measurement indicated the films deposited by PP PECVD have higher potential against PID in consideration of less oxygen content in this film. That demonstrated the film properties were changed by applied a new control of freedom, i.e., PP method. In addition, the 96 h PID result of the integrated PP method was only −2.07%, which was comparable to that of the integrated traditional CP method. In summary, we proposed three effective or potential approaches to eliminate the PID issue, and all approaches satisfied the IEC 62804 standard of less than 5% power loss in PV modules.

A method that can have insight into the rear-side passivation performance of passivated emitter and real cells (PERC) is crucial for further improving the cell efficiency. In this paper, we propose a method based on high-resolution laser beam induced current (HR-LBIC) for investigating the rear-side passivation performance of PERC cells. Using this method, the performance of local back surface field (LBSF) regions and rear dielectric passivation regions can be distinguished quantitatively, and it helps easily comparing the cells with different rear-side passivation performance. Most importantly, the potential Voc of the PERC cells under current used aluminum paste can be estimated as well.

The purpose of this study is to reduce textured crystalline silicon (TCS) substrate surface-reflectivity over a wide spectral range (300–1100 nm), to improve the step coverage of the textured structure, and to shift the minimal value of reflection from the unabsorbed region to the absorbed region. The TCS solar-cell interface between air and silicon was added to a SiO x /SiO x N y /SiN x triple-layer anti-reflective coatings (TLARCs) structure using the plasma-enhanced chemical vapor deposition (PECVD) growth method. This paper presents theoretical and practical discussions, as well as the experimental results of fabricating the films and devices. The average reflection of the SiO x /SiO x N y /SiN x TLARs reduced to 2.01% (300–1100 nm). The minimal value of reflection was shifted from 1370 nm (unabsorbed region) to 968 nm (absorbed region). The SEM images show effective step coverage. In comparison to the untreated TCS solar cells, applying the experimental SiO x /SiO x N y /SiN x TLARCs to conventional TCS solar cells improved the short-circuit current density ( J sc ) by 7.78%, and solar-cell efficiency by 10.95%. This study demonstrates that the SiO x /SiO x N y /SiN x TLARCs structure provides antireflective properties over a broad range of visible and near-infrared light wavelengths. An effective step coverage and minimal value of reflection from unabsorbed region shift to the absorbed region is demonstrated.

InGaN/GaN multiple quantum well light emitting diodes with charge asymmetric resonance tunneling structure, which can emit dual color lights of blue/green or blue/yellow, were grown on sapphire by metalorganic chemical vapor deposition. Their optical and structural properties are studied by high-resolution X-ray diffraction, high-resolution transmission electron microscopy, temperature-dependent photoluminescence (PL) and photoluminescence excitation (PLE). PL peak shifts and PLE features are found to vary with the well-growth temperature. The luminescence mechanism is discussed in details, correlating to the In composition fluctuation, carrier localization and the quantum confined Stark effect.

Luminescence properties of blue emission InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs), grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD), were studied by time-resolved photoluminescence (TRPL) spectroscopic technique. Samples involved have similar basic structures of three QWs but different well-composition and barrier/well dimensions. TRPL results show that PL intensity and decay time increase with the number of QWs and the indium composition. Correlation of physical properties with crystalline perfection open the way for optimized designs of InGaN MQW LED, with controlled the indium composition and QW numbers.

In this letter, the AlGaInP light-emitting diodes (LEDs) between the air and GaP layer are added to the textured ZnO:Al (AZO) films in order to improve light extraction of the device. At 20 mA, the relative luminous intensity of textured AZO LEDs is increased by 129.9% when compared with the conventional sample. Furthermore, the far-field radiation pattern was improved with intensity not only at 0° , but also from 60° to 300° . Due to loss of internal Fresnel efficiency and critical angle efficiency, textured AZO LEDs are significantly improved by the wet-etching technique. The surface treatment of AZO films generates surface texturing that is characterized as random crater. It presents a better far-field radiation pattern when compared with nontextured AZO films. This letter has demonstrated the far-field radiation pattern and the theory for enhancing light emission efficiency of LEDs.

This paper considers the intrinsic layer of hydrogenated amorphous silicon (a-Si:H) solar cells. The deposition temperature and electrode distance (between cathode and anode) are important factors for a-Si:H solar cells. Thus, this study examines the effects of deposition temperatures and electrode distances in the intrinsic layer of a-Si:H solar cells with regard to enhanced the short-circuit current density (J sc ) and thereby conversion efficiency. It is shown that the J sc of a-Si:H solar cells can be increased by proper choice of deposition temperature and electrode distance of the i-a-Si:H layers. Results show that the optimized parameters improves the J sc of a-Si:H solar cells to 16.52 mA/cm2, yielding an excellent conversion efficiency of 10.86%.

In this paper, the superstrate-type silicon-based tandem cells between air and glass are added to a porous SiO 2 /MgF 2 double-layer anti-reflective (DLAR) thin film structure in order to improve the glass substrate low reflectivity in a wide spectral range (400–1200nm), without high reflectivity in the near-infrared region. Practical discussion is presented, as well as experimental results of fabricated films and devices. Application of the experimental porous SiO 2 /MgF 2 DLAR thin film to conventional silicon-based tandem solar cells results in improvement of the short-circuit current density by 6.82%. Solar cell efficiency is improved by 7.14%. The presented experimental porous SiO 2 /MgF 2 DLAR thin film structure provides anti-reflective results in a broad range of visible light, without high reflectivity at near-infrared wavelengths.

The optical and structural properties of Charge Asymmetric Resonance Tunneling (CART) structure InGaN/GaN multiquantum wells (MQWs) grown on sapphire by metalorganic chemical vapor deposition (MOCVD) have been investigated by optical measurements of temperature-dependent photoluminescence (PL), photoluminescence excitation (PLE) and time-resolved photoluminescence (TRPL), and high-resolution transmission electron microscopy (HRTEM). Two typical samples are studied, both consisting of six periods of CART InGaN wells with 3.3 nm thickness and with 8.5 nm thickness of GaN barrier, respectively, and two periods of InGaN wells with 2 nm thickness of 7 nm GaN barrier with different well growth-temperature of 797 0 C and 782 0 C, respectively. According to the PL measurement results, large values of activation energy are obtained. The decrease of well growth-temperature results higher In composition and also in the increase of composition fluctuation in the InGaN MQW region, showing the stronger carrier localization effect and large values of activation energy and Stokes’ shift are obtained. The lifetime at the low-energy side of the InGaN peaks is longer for higher indium composition.

The purpose of this study is to reduce the glass substrate reflectivity over a wide spectral range (400-1200nm) without having high reflectivity in the near-infrared region. After making porous SiO2/MgF2 double-layer antireflection (DLAR) thin film structure, the superstrate-type silicon-based tandem cells are added. In comparison to having only silicon-based tandem solar cells, the short-circuit current density has improved by 6.82% when porous SiO2/MgF2 DLAR thin film is applied to silicon-based tandem solar cells. This study has demonstrated that porous SiO2/MgF2 DLAR thin film structure provides antireflection properties over a broad spectral range (400-1200nm) without having high reflectivity at near-infrared wavelengths.

By inductively coupled plasma (ICP) etching, a selective high barrier region (SHBR) was fabricated below the p-pad metal electrode for modifying the injection current distribution on p-type GaN of GaN-based light-emitting diodes (LEDs). Through the analysis of current noise power spectra, the samples with ICP etching treatment have excess nitrogen vacancies at the selectively etched surface of p-type GaN; thus, they have a lower hole concentration than the as-grown sample, resulting in a larger barrier height for carrier transport. With this SHBR, the light-output power for the LED chip measured at 20 mA was significantly increased by 12% as compared with that for the conventional LED chip. The light-output power increase could be attributed to a relative reduction in optical power absorption under the p-pad electrode and a higher density of current effectively injected into the active layer of the LED by the SHBR structure.