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Comparative Evaluation of Lifetime of Three-Level Inverters in Grid-Connected Photovoltaic Systems
摘要： The cost of the PV energy reduction is still required to increase the penetration level of PV systems in the energy market. The reliability of PV inverters is one of the important aspects to be enhanced in order to reduce the cost of PV energy, since it is closely related to the maintenance cost and the annual energy production. In this paper, the lifetime of NPC and T-type inverters, which are three-level inverter topologies that are widely used for PV systems, are comparatively evaluated with a 30 kW grid-connected PV system. It is performed by focusing on power devices since the power electronic components of both converters are the same except for the power devices. Therefore, this result can represent the comparison of the reliability performance of the NPC and T-type inverters. The power loss and temperature distributions of power devices are analyzed and their e?ciencies are compared at di?erent power levels with di?erent switching frequencies. The lifetimes of the reliability-critical power devices in the NPC and T-type inverters are estimated, respectively with a one-year mission pro?le of the PV system, and the results are compared.
关键词： three-level inverter,IGBT module,PV inverter,reliability,power device,lifetime
更新于2025-09-19 17:13:59
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Molecular engineering of an electron-transport triarylphosphine oxide-triazine conjugate toward high-performance phosphorescent organic light-emitting diodes with remarkable stability
摘要： Organic electron-transport materials are an essential component to boost performances and stability of organic light-emitting diodes. We present a robust organic electron-transport compound 3-(6-(3-(4,6-bis(4-biphenylyl)-1,3,5-triazin-2-yl)phenyl)pyridin-2-yl)phenyldiphenylphosphine oxide by facilely coupling the triphenylphosphine oxide moiety to the 2-phenyl-4,6-bis(4-biphenylyl)-1,3,5-triazine unit via a 2,6-pyridinylene linker. It is well soluble in weakly polar solvents and possesses a high Tg of 123 °C with an exceptional Td≈470 °C at 1% weight loss and deep HOMO/LUMO levels of ca. ?6.45/?3.06 eV. The phosphorescent spectrum measured in solid state at 77 K reveals a notable triplet energy of 2.88 eV. n-Doping with 8-hydroxyquinolatolithium (Liq) produces the electron mobility value of 4.66×10?5–3.21×10?4 cm2 V?1 s?1@(2–5)×105 V cm?1. Moreover, the contrasting solubility of the bromo reaction intermediate and the new compound in alcoholic solvents facilitates separation. The characterizations of bottom- and top-emission green phosphorescent OLEDs involving this single Liq-doped electron-transport layer reveal long stability. In particular, the latter provides outstanding performances with 77.4 cd A–1 (corresponding to an EQE of 18.7%) and 86.8 lm W–1@ca. 1000 cd m?2, based on the green emitter bis(2-phenylpyridine)(2-(4-methyl-3-phenylphenyl)pyridine)iridium(III). Moreover, driven by a constant current for ca. 640 h, the initial luminance of 1000 cd m–2 appears almost no decay.
关键词： halogen impurities,heterocycles,electron-transport materials,lifetime,phosphine oxides
更新于2025-09-19 17:13:59
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Enhancing inertia of solar photovoltaic-based microgrid through notch filter-based PLL in SRF control
摘要： More and more wind turbine manufacturers turn to using the full-scale power electronic converter due to the stricter grid code requirements to thoroughly decouple the generator from the grid connection. However, a commonly used type of this generator is still unclear, where the selections of the low-speed (LS; direct-drive) and medium-speed (MS; one-stage) permanent-magnet synchronous generators (PMSGs) are both promising solutions. This paper will assess and compare the reliability metrics for the machine-side converter (MSC) for those two configurations. First, a translation from the mission profile of the turbine to the current and voltage loading of each power semiconductor is achieved based on synchronous generator modeling. Afterward, a simplified approach to calculate the loss profile and the thermal profile is used to determine the most stressed power semiconductors in the converter. Finally, according to the lifetime power cycles, the lifespan can be calculated when operating in various wind classes. It is concluded that, although the LS PMSG is able to eliminate the gearbox, the lifespan of its MSC is lower than the one-stage MS generator.
关键词： loss profile,power electronic converter,thermal profile,Lifetime prediction,permanent-magnet synchronous generator (PMSG)
更新于2025-09-19 17:13:59
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Investigating the influence of the solution-processing method on the morphological properties of organic semiconductor films and their impact on OLED performance and lifetime
摘要： The morphological properties of organic semiconductor films deposited by blade coating and spin coating were investigated. The effect of these solution coating methods in fabricating the hole transport layer (HTL) and emissive layer (EML) of OLEDs was also examined. Transient photoluminescence measurements showed that blade-coated films have longer exciton lifetimes than spin-coated films, indicating that blade coating leads to films with less aggregated and more uniform morphologies. OLEDs with a blade-coated CBP:Ir(ppy)3 EML exhibited an external quantum efficiency (EQE) at 20 mA/cm2 of 8.6 % versus 6.4 % in case of device with the same structure but with a spin-coated EML. Additionally, the blade coated CBP:Ir(ppy)3-based device showed a decrease in electroluminescence emission peak by about 52% from its initial value after 20 min of electrical aging, whereas for the spin-coated device, the decrease was 74%. The higher efficiency and longer lifetime in the blade coated devices is likely a result of a more uniform or less aggregated film morphology. These findings demonstrate that blade coating is a promising solution-based fabrication technique to enable more efficient and longer-lived small molecule, solution-coated OLEDs and organic optoelectronic devices.
关键词： Blade coating,OLEDs,Lifetime,Organic semiconductors,Spin coating,Morphology
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Photoluminescence Excitation Spectroscopy Characterization of Surface and Bulk Quality for Early-Stage Potential of Material Systems
摘要： Photoluminescence Excitation Spectroscopy (PLE) is a contactless characterization technique to quantify Shockley-Reed-Hall (SRH) lifetimes and recombination velocities in direct band gap experimental semiconductor materials and devices. It is also useful as to evaluate surface passivation and intermediate fabrication processes, since it can be implemented without the need for development of effective contact technologies. In this paper, we present a novel experimental PLE system for precision-based quantification of the aforementioned parameters as well as a system for which absolute PLE characterization may occur. Absolute PLE measurements can be used to directly calculate VOC for new photovoltaic (PV) material systems and devices. Key system capabilities include a continuous excitation spectrum from 300 nm –1.1 μm, automated characterization, up to 1 nm wavelength resolution (up to 60x higher than prior work), and a reduced ellipsometry requirement for post-processing of data. We utilize a GaAs double heterostructure (DH) and an InP crystalline wafer as calibration standards in comparison with data from an LED-based PLE to demonstrate the validity of the results obtained from this new system.
关键词： photovoltaic cells,indium phosphide,charge carrier lifetime,gallium arsenide,photoluminescence
更新于2025-09-19 17:13:59
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Degradation prediction of a γ-ray radiation dosimeter using InGaP solar cells in a primary containment vessel of the Fukushima Daiichi Nuclear Power Station
摘要： Indium gallium phosphide (InGaP) solar cell with a superior high-radiation resistance is expected to be a powerful candidate for a dosimeter under a high-radiation dose rate environment. In this study, in order to predict the lifetime as the dosimeter using the InGaP solar cell, we clarify the effect of minority-carrier diffusion length (L) on a radiation-induced current as a dose signal in the InGaP solar cell by irradiation tests and empirical calculations. In the irradiation tests, the short-circuit current density (Jsc) as a function of the γ-ray dose rate is measured to estimate the L for the InGaP solar cell by irradiation tests. The operational lifetime as a detector using the InGaP solar cell under various dose rates is estimated by using the empirical calculations based on the relation between the L and absorbed dose. The results suggest that the dosimeter using InGaP solar cell is able to be used during more than 10 h in the primary containment vessel of the Fukushima Daiichi Nuclear Power Plant and it has a high potential of being a radiation-resistant dosimeter that would contribute to the decommissioning.
关键词： solar cell,operation lifetime,decommissioning,radiation-induced current,minority-carrier diffusion length,Dosimetry,InGaP compound semiconductor,degradation prediction
更新于2025-09-16 10:30:52
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Electrostatic potential dispersing pyrimidine-5-carbonitrile acceptor for high efficiency and long lifetime thermally activated delayed fluorescence organic light-emitting diodes
摘要： Pyrimidine-5-carbonitrile was developed as an electrostatic potential managing and strong acceptor moiety of thermally activated delayed fluorescence (TADF) emitters for high efficiency and long lifetime in devices. Two types of TADF emitters with the donor moiety extended from either the 2 or 4 position of the acceptor moiety were prepared to study the effect of the donor substitution position on the TADF characteristics of the TADF emitters. Comparison of the two types of TADF emitters suggested that the extension of the donor structure from the 4 position of the pyrimidine-5-carbonitrile acceptor is an effective way of enhancing the external quantum efficiency (EQE) and lifetime of the TADF devices. A high EQE of 19.8% and lifetime exceeding that of the state-of-the-art green TADF emitter were demonstrated using one of the pyrimidine-5-carbonitrile derived emitters through the uniformly distributed electrostatic potential.
关键词： organic light-emitting diodes,Pyrimidine-5-carbonitrile,thermally activated delayed fluorescence,electrostatic potential,high efficiency,long lifetime
更新于2025-09-16 10:30:52
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Fluorescence Lifetime Imaging Ophthalmoscopy of the Retinal Pigment Epithelium During Wound Healing After Laser Irradiation
摘要： Purpose: To investigate the change in fluorescence lifetime of retinal pigment epithelium (RPE) after laser irradiation by using an organ culture model. Methods: Porcine RPE-choroid-sclera explants were irradiated with selective retina treatment laser (wavelength: 527 nm, beam diameter: 200 lm, energy: 80–150 lJ). At 24 and 72 hours after irradiation, the mean fluorescence lifetime (sm) was measured with fluorescence lifetime imaging ophthalmoscopy (FLIO) (excitation wavelength: 473 nm, emission: short spectral channel: 498-560 nm, long spectral channel: 560–720 nm). For every laser spot, central damaged zone (zone 1: 120 3 120 lm), area including wound rim (280 3 280 lm except zone 1), and environmental zone (440 3 440 lm except zone 1 and 2) were analyzed. Peripheral zone at a distance from laser spots longer than 2000 lm was examined for comparison. Cell viability was evaluated with calcein-acetoxymethyl ester and morphology with fluorescence microscopy for filamentous-actin. Results: The RPE defect after selective retina treatment was mostly closed within 72 hours. FLIO clearly demarcated the irradiated region, with prolonged sm at the center of the defect decreasing with eccentricity. In short spectral channel, but not in long spectral channel, sm in the environmental zone after 72 hours was still significantly longer than in the peripheral zone. Conclusions: FLIO may clearly demarcate the RPE defect, demonstrate its closure, and, moreover, indicate the induced metabolic changes of surrounding cells during wound healing. Translational Relevance: This ex vivo study showed that FLIO may be used to evaluate the extent and quality of restoration of the damaged RPE and to detect its metabolic change in human fundus noninvasively.
关键词： selective retina therapy,retinal pigment epithelium,fluorescence lifetime,energy metabolism,wound healing
更新于2025-09-16 10:30:52
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The use of surfactant-filled mesoporous silica as an immobilising medium for a fluorescence lifetime pH indicator, providing long-term calibration stability
摘要： Surfactant filled mesoporous silica is applied as a matrix for immobilizing the fluorescence lifetime pH-indicator acridine. We demonstrate that this type of encapsulation provides a stable and uniform chemical environment for the indicator and has good proton transport properties leading to rapid pH response times. Furthermore, the immobilising medium effectively prevents leaching of the indicator, facilitates high long-term stability and does not influence the pH sensing-range of the indicator.
关键词： acridine,surfactant-filled mesoporous silica,fluorescence lifetime pH indicator,proton transport properties,long-term calibration stability
更新于2025-09-16 10:30:52
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Self-modulated laser-plasma acceleration in a H2 gas target, simulated in a spectral particle-in-cell algorithm: wakefield and electron bunch properties
摘要： Consider a mobile sensor network that is used to monitor a moving target in a field with obstacles. In this paper, an efficient relocation technique that simultaneously maximizes the network lifetime is proposed. The main sources of energy consumption in the network are sensing, communication, and movement of the sensors. To account for this energy consumption, a graph is constructed with edges that are weighted based on the remaining energy of each sensor. This graph is subsequently employed to address the lifetime maximization problem by solving a sequence of shortest path problems. The proposed technique determines a near-optimal relocation strategy for the sensors as well as an energy-efficient route to transfer information from the target to destination. This near-optimal solution is calculated in every time instant using the information obtained through the previous time step. It is shown that by choosing appropriate parameters, sensors’ locations and the communication route from target to destination can be arbitrarily close to their corresponding optimal choices at each time instant. Simulation results confirm the effectiveness of the proposed technique.
关键词： target monitoring,mobile sensor network,Energy,lifetime
更新于2025-09-16 10:30:52