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Investigation on plasma characteristics in a laser ablation pulsed plasma thruster by optical emission spectroscopy
摘要： In order to further improve the propulsion performance of pulsed plasma thrusters for space micro propulsion, a novel laser ablation pulsed plasma thruster is proposed, which separated the laser ablation and electromagnetic acceleration. Optical emission spectroscopy is utilized to investigate the plasma characteristics in the thruster. The spectral lines at different times, positions and discharge intensities are experimentally recorded, and the plasma characteristics in the discharge channel are concluded through analyzing the variation of spectral lines. With the discharge energy of 24 J, laser energy of 0.6 J and the use of aluminum propellant, the specific impulse and thrust efficiency reach 6808 s and 70.6%, respectively.
关键词： plasma,optical emission spectroscopy,propulsion performance,laser ablation pulsed plasma thruster
更新于2025-09-11 14:15:04
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Performance analysis of mono and poly-crystalline silicon photovoltaic modules under Agadir climatic conditions in Morocco
摘要： The evaluation of a solar photovoltaic (PV) technology helps to identify its suitability for a specific location. The main objective of the present study is to assess the suitability of mono-crystalline silicon (mc-Si) and poly-crystalline silicon (pc-Si) PV modules with almost similar characteristics under Agadir climatic conditions. Electricity yield of these modules is calculated from the uninterruptible measured current–voltage curves from sunrise to sunset during a year. The influence of weather conditions, global irradiance and temperature, on the performances of the modules is assessed and as a part of considerations in the PV power plant design that the output power from pc-Si PV modules is found greater. Calculated annual average final yield (Yf), and performance ratio (PR) for mc-Si and pc-Si PV systems are (1602.22 kWh/kWp, 0.71), (1691.85 kWh/kWp, 0.75) respectively.
关键词： Performance,Outdoor monitoring,Photovoltaic,Energy yield,I–V curves
更新于2025-09-11 14:15:04
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Aggregation-Induced Delayed Fluorescence Luminogens with Accelerated Reverse Intersystem Crossing for High-Performance OLEDs
摘要： A fast reverse intersystem crossing (RISC) is of high importance for delayed fluorescence emitters in terms of increasing exciton utilization and suppressing efficiency roll-off. Herein, new robust luminogens comprised of carbonyl, phenoxazine and chlorine-substituted carbazole derivatives are synthesized and characterized. They own distinct aggregation-induced delayed fluorescence (AIDF) feature, and exhibit high photoluminescence efficiencies and short delayed fluorescence lifetimes in neat films. The RISC is conspicuously accelerated owing to their tiny singlet-triplet energy splitting and greatly enhanced spin-orbit coupling by heavy atom effect in neat films. They can function efficiently as light-emitting layers in nondoped OLEDs, providing excellent maximum electroluminescence (EL) efficiencies of 20.4–21.7%, and can also perform outstandingly in doped OLEDs in a wide doping concentration range (5–90 wt%), affording impressive EL efficiencies of up to 100.1 cd A–1, 104.8 lm W–1 and 29.1%, with small efficiency roll-off. These findings demonstrate the AIDF luminogens with fast RISC are promising candidates to fulfill various demands of production and application of OLEDs.
关键词： OLEDs,Reverse Intersystem Crossing,Luminogens,Aggregation-Induced Delayed Fluorescence,High-Performance
更新于2025-09-11 14:15:04
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2D Materials in Infrared Detector Family
摘要： The paper compares two-dimensional (2D) material detectors performance with traditionally and commercially available ones operating in high temperature conditions. The most effective single graphene detectors are THz detectors which utilize plasma rectification phenomena in FETs. Most of 2D layered semiconducting material photodetectors operate at the visible and near-infrared regions and generally their high sensitivity does not coincide with a fast response time, which limits real detector functions.
关键词： detector performance,infrared and terahertz detectors,2D materials
更新于2025-09-11 14:15:04
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Anomalous Stokes shift of colloidal quantum dots and their influence on solar cell performance
摘要： We report an anomalous Stokes shift effect observed in colloidal solutions containing down-shifting Carbon quantum dots (CQDs) of different sizes that is expected to have a positive in?uence on the power conversion ef?ciency of photovoltaic structures. Speci?cally, with an excitation wavelength of 390 nm, individual colloidal solutions of CQDs whose diameter was determined by the applied current during synthesis, exhibited photoluminescent (PL) emission wavelength peaks centered at 420 nm. However, the colloidal solution comprising the mixture of all the previously synthesized CQDs of different diameters was observed to have an anomalous PL Stokes shift centered at 515 nm. Furthermore, the afore-mentioned anomalous SSE was also observed in CdTe QDs when added to the CQD mixed-solution (CMS). Thus, whereas a mixture of CdTe QDs of different sizes, exhibited a down-shifted photoluminescence centered at 555 nm, the peak was observed to have an anomalous Stokes shift centered at 580 nm when combined with the CMS. Quantum dot characterization included crystal structure analysis as well as photon absorption and photoluminescence wavelengths. Subsequently, the synthesized QDs were dispersed in a polymeric layer of PMMA and incorporated on functional and previously characterized solar cells, to quantify their in?uence in the electrical performance of the photovoltaic devices. The observations indicate an improvement in the PCE of 4.6% when incorporating Carbon QDs, 2.9% with CdTe QDs and 4.8% when employing both C and CdTe QDs.
关键词： solar cell performance,photoluminescence,Carbon quantum dots,Anomalous Stokes shift,colloidal quantum dots,CdTe quantum dots,power conversion efficiency
更新于2025-09-11 14:15:04
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Best practices for measuring emerging light-emitting diode technologies
摘要： The arrival of light-emitting diodes based on new materials is posing challenges for the characterization and comparison of devices in a trusted and consistent manner. Here we provide some advice and guidelines that we hope will benefit the community.
关键词： LED characterization,emerging technologies,performance metrics,standardization,light-emitting diodes
更新于2025-09-11 14:15:04
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Performance evaluation of different photovoltaic technologies in the region of Ifrane, Morocco
摘要： This study aims at analyzing and comparing several indices that evaluate the performance of different grid connected photovoltaic technologies, namely amorphous silicon (a-Si), Polycrystalline silicon (pc-Si), and Monocrystalline silicon (mc-Si) generating around 2 kWp each and set up a forecast studies for future perspectives. These technologies are connected to a low voltage (400 V) three phase electrical grid of Al Akhawayn University (33° North, 5° West) facing south on a flat surface, 32° tilted with zero azimuth, and without including any tracking system. This work is done within the framework of Propre.ma project aiming at establishing a photovoltaic yield maps throughout Morocco. The experimental and theoretical horizontal irradiances of Ifrane's region, simulated with the Davies and Hay model on the MATLAB's software, are compared in the following study. Besides, the evaluation of different technologies is based on the (annual/monthly/daily) AC energy output, the performance ratio, the system efficiency, and the capacity factor that are calculated and measured from data gathered between October 2014 and the end of 2018. An economic analysis was carried out in order to define the levelized cost of electricity of the three technologies. Eventually, the obtained results confirm that the polycrystalline technology is the most cost-effective technology for the region of Ifrane.
关键词： Photovoltaic,Polycrystalline,Performance evaluation,Economic analysis,Amorphous,Monocrystalline
更新于2025-09-11 14:15:04
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Ultra‐High Fidelity Laser‐Induced Air Shock from Energetic Materials
摘要： Recent interest in the implementation of the Laser-induced Air Shock from Energetic Materials (LASEM) technique prompted an investigation using ultra-high-speed imaging diagnostics to provide early-time (sub-μs) shock-wave-radius-versus-time data necessary to accurately determine the characteristic laser-induced-shock velocity (y-intercept) for high explosives (HE) of interest. Ultra-high-speed focused-shadowgraphy images were collected from nanosecond-pulsed laser-ablated samples of HE similar to those in the published literature. Shadowgraphy images were collected using interframe times ranging from 50–750 ns, with exposure times of 5 ns. Acquired shock-wave-radius-versus-time data permitted a high-fidelity assessment of the shock wave velocity produced at the characteristic radius of the generated laser-plasma pulse. The resulting data from eight different HE indicated that early-time energy contributions and the resulting laser-induced shock velocity profiles produced from ablation of the HE material were indistinguishable amongst the explosives tested for the majority of the time domain characterized (0–12 μs).
关键词： laser-induced shock wave,shock physics,energetic-material characterization,detonation performance,laser-induced plasma
更新于2025-09-11 14:15:04
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Improving Photovoltaic Performance by Using Perovskite/Surface Modified Graphitic Carbon Nitride Heterojunction
摘要： Passivation strategies were considered as one of the most efficient methods to suppress non-radiative recombination of organic-inorganic lead halide perovskite solar cells (PSCs), then, as well as, were widely employed as passivation agents, according to the previous reports. Anchoring g-leading to tremendous photovoltaic performance. An innovative 2D polymer, graphitic carbon nitride (g-C3N4), as well as various organic groups (amino, sulfonic, nitrato and hydroxy group) leading to tremendous photovoltaic performance. C3N4 and the aforementioned organic groups as additives in perovskite could both heal charged defects around the grain boundaries by passivating the charge recombination center. Besides, the crystalline quality could also be enhanced by the incorporation of g-C3N4, leading to improved conductivity of perovskite light absorber films that is beneficial for benign charge extraction efficiency. Inspiring of the underlining mechanisms, we designed a series of novel passivation molecules, functionalized g-C3N4 (F-C3N4) with assorted organic groups, yielding to champion power conversion efficiency (PCE) of 20.08% for NO3-C3N4 based p-i-n structure PSC, in comparison with that of PSC without passivation (17.85%). These findings presented an efficient strategy to understand and design multiple facets of applications of novel passivation molecules to further improve the PCE of PSCs.
关键词： passivation,graphitic carbon nitride,perovskite solar cells,organic groups,photovoltaic performance
更新于2025-09-11 14:15:04
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Designing High Performance Nonfullerene Electron Acceptors with Rylene Imides for Efficient Organic Photovoltaics
摘要： Improving carrier mobility, redox stability, blend morphology, and photovoltaic performance while elucidating structure-property relationships remain important design goals for nonfullerene electron acceptors (NFAs) for organic solar cells. Although numerous NFAs have been created from rylene diimide electron-deficient building blocks, they have showed far inferior photovoltaic properties compared to benchmark fused-ring electron acceptors (FREAs) such as ITIC. Herein we show that new bis(naphthalene-imide)arylenelidenes (BNIAs), incorporating rylene-imide end-capping groups via methine bridges in donor-acceptor architectures, are endowed with enhanced electrochemical redox stability, high carrier mobilities, and high photovoltaic performance. Pairing of those BNIAs that are also FREAs, NIDT and NIBT, respectively with donor polymer PBDB-T produced 10.0-10.8% efficient photovoltaic devices, which are comparable to benchmark ITIC devices. Blends of FREAs NIDT and NIBT and those of non-FREA NITV were found to have similar electron mobility, demonstrating that the much higher photovoltaic efficiency of NIDT and NIBT devices does not originate from enhanced charge transport but from differences in blend morphology and blend photophysics. The results demonstrate that incorporating rylene imides into molecular architectures through methine-bridged donor-acceptor coupling motif is a promising design strategy towards more efficient and electrochemically rugged materials for organic solar cells.
关键词： organic photovoltaics,carrier mobility,redox stability,photovoltaic performance,nonfullerene electron acceptors,rylene imides
更新于2025-09-11 14:15:04