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Predicting the afterglow duration in persistent phosphors: a validated approach to derive trap depth distributions
摘要： Persistent phosphors are increasingly investigated due to their potential applications in various fields, such as safety signage, dosimetry and in vivo imaging. These materials act as optical batteries that store and gradually release energy supplied during optical charging. As the energy is stored, or ‘trapped’, at specific defect sites in the host lattice, a clear understanding of the defects and trapping mechanisms in these materials is important for systematic improvement of their properties. Here, the thermoluminescence and afterglow properties of the near-infrared (NIR) emitting persistent phosphor LiGa5O8:Cr3+ (LGO:Cr) are studied. This phosphor is used as a model system for illustrating a more general approach to reliably derive trap depth distributions in persistent luminescent and storage materials. The combination of the Tstop–Tmax method with initial rise analysis is used to experimentally determine the presence of a broad distribution of trapping states. Computerized glow curve fitting is subsequently used to extract the relevant trapping parameters of the system in a rigorous, consistent manner, by fitting all the experimentally recorded data simultaneously. The resulting, single set of model parameters is able to describe all measured thermoluminescence and afterglow data and hence can be used to predict afterglow and storage properties of the phosphor under various conditions. The methods to analyze and describe the trap structure of the persistent phosphor LGO:Cr are straightforwardly applicable for other persistent and storage phosphors and result in a reliable determination of the relevant trapping parameters of a given material.
关键词： thermoluminescence,afterglow,persistent phosphors,LiGa5O8:Cr3+,trap depth distributions
更新于2025-09-19 17:15:36
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Alleviation of abnormal NBTI phenomenon in LTPS TFTs on polyimide substrate for flexible AMOLED
摘要： This letter investigates the negative-bias temperature instability (NBTI) behavior of p-channel low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) on plastic substrate. The measurements reveal that the threshold-voltage positive shift is highly correlated to the passivation of grain boundary trap states. By applying the established phenomenon such as NBTI recovery and H diffusion from PI substrate, a new model is introduced to explain the mechanism and verified by the experiment. With the thick buffer and bottom metal layer or newly processed PI substrate, we succeeded in adjusting the NBTI behavior of LTPS TFTs on plastic substrate.
关键词： interface trap state,flexible AMOLED,negative-bias temperature instability (NBTI),grain boundary trap state,LTPS TFTs
更新于2025-09-19 17:13:59
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Vein width measurement of groundwater on Earth's surface using semiconductor laser light and proton precession magnetometer
摘要： Near-surface geophysical methods such as Semiconductor LASER Light Box (SCLLB) and Proton Precession Magnetometer (PPM) coupled with Vertical Electrical Soundings (VES) and water dowsing approach are used to measure the vein width of Groundwater (GW) on the Earth's surface at fifteen locations in the Deccan Trap flood basalt area in Pune region, Maharashtra, India. The main objective is to validate old simple water dowsing way of GW detection in hard rock using the established modern science and technology namely VES, PPM and SCLLB techniques. On the basis of deflection of the L-shaped copper rods, the presence of GW with clues on the edges of GW vein is detected using the old traditional dowsing method. The efficacy of dowsing is verified by VES. It is found that apparent resistivity in the range from 48?m to 117?m over the GW location delineated by the dowser is relatively low, thus confirming the presence of GW in the study area. Variation in the intensity of Earth’s Magnetic Field (EMF) measured by PPM is found in the range from 37,788nT to 43,242nT over GW locations. High magnetic intensity values indicate a high GW potential in weathered vesicular-amygdaloidal basalt and magnetic field gradient changes enabled to calculate GW vein width. It is suggested that water dowsers might get a dowsing reaction as a result of entering into magnetic field gradient changes caused by GW. Digital barometer records the atmospheric pressure (P) and temperature (T) showing that both P and T are higher than the non-GW location which alters refractive index (RI) of medium over GW locations in the study area. A small change in RI alters the intensity of the semiconductor laser beam (≈234μA to 1204μA) indicating the edges of GW vein, thus giving the width of the vein. The results obtained by PPM and SCLLB match with dowsing responses. It is found that GW sources and width of GW vein (≈1m to 6m) in Deccan basaltic terrain can be measured quickly and with ease by using SCLLB in comparison to VES and PPM. It is concluded that the application of proposed modern instrumental measurement survey by PPM and SCLLB coupled with the old simple technology of water dowsing helps to identify the potential of the area to generate a subsurface water resource database at the national level, especially in hard rock.
关键词： Hard rock terrain,Groundwater vein,Proton Precession Magnetometer,Deccan Trap basalt,Dowsing,Semiconductor LASER Light Box
更新于2025-09-19 17:13:59
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[IEEE 2018 IEEE International RF and Microwave Conference (RFM) - Penang, Malaysia (2018.12.17-2018.12.19)] 2018 IEEE International RF and Microwave Conference (RFM) - Simulation Analysis of EDFA in Optical Fiber with WDM System in the Perspective of Bangladesh
摘要： Harmonic stability problems caused by the resonance of high-order ?lters in power electronic systems are ever increasing. The use of passive damping does provide a robust solution to address these issues, but at the price of reduced ef?ciency due to the presence of additional passive components. Hence, a new method is proposed in this paper to optimally design the passive damping circuit for the LCL ?lters and LCL with multituned LC traps. In short, the optimization problem reduces to the proper choice of the multisplit capacitors or inductors in the high-order ?lter. Compared to existing design procedures, the proposed method simpli?es the iterative design of the overall ?lter while ensuring the minimum resonance peak with a lower damping capacitor and a lower rated resistor. It is shown that there is only one optimal value of the damping resistor or quality factor to achieve a minimum ?lter resonance. The passive ?lters are designed, built, and validated both analytically and experimentally for veri?cation.
关键词： voltage-source converters,trap ?lter,resonance damping,LCL ?lter,Harmonic passive ?lters
更新于2025-09-19 17:13:59
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Ligand-Assisted Reconstruction of Colloidal Quantum Dots Decreases Trap State Density
摘要： Increasing the power conversion efficiency (PCE) of colloidal quantum dot (CQD) solar cells has relied on improving the passivation of CQD surfaces, enhancing CQD coupling and charge transport, and advancing device architecture. The presence of hydroxyl groups on the nanoparticle surface, as well as dimers—fusion between CQDs—has been found to be the major source of trap states, detrimental to optoelectronic properties and device performance. Here, we introduce a CQD reconstruction step that decreases surface hydroxyl groups and dimers simultaneously. We explored the dynamic interaction of charge carriers between band-edge states and trap states in CQDs using time-resolved spectroscopy, showing that trap to ground-state recombination occurs mainly from surface defects in coupled CQD solids passivated using simple metal halides. Using CQD reconstruction, we demonstrate a 60% reduction in trap density and a 25% improvement in charge diffusion length. These translate into a PCE of 12.5% compared to 10.9% for control CQDs.
关键词： trap states,dimers,surface defects,photovoltaics,Quantum dots
更新于2025-09-19 17:13:59
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Impact of intentional photo-oxidation of a donor polymer and PC <sub/>70</sub> BM on solar cell performance
摘要： Impact of intentional photo-oxidation of a donor polymer and PC70BM on solar cell performance. A short lifetime is the main factor hindering the wider implementation of low-cost organic photovoltaics through non-ideal encapsulation layers is a known cause of degradation for polymer/fullerene based solar cells. To better understand the origin of this performance degradation, we study the effect of intentional exposure of the photo-active layer to simulated sunlight (AM1.5) in air both on the solar cell performance and on the molecular semiconductor materials. Cathode-free thin films of a blend of the electron donor polymer poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) and the electron acceptor fullerene derivative [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) were exposed to simulated sunlight in air. Fourier-transform infrared spectra demonstrate the formation of carbonyl photo-oxidation products in the blend films, as well as in the pristine polymer and fullerene films. Solar cells prepared with photo-oxidized active layers show increasingly degraded electrical performance (lower short circuit current, open circuit voltage and fill factor) with increasing exposure time. The increased diode ideality factor indicates that trap-assisted recombination hinders device operation after exposure. The external quantum efficiency decreases drastically with increasing exposure time over the whole photon energy range, while the UV-vis absorption spectra of the blend films only show a mild photo-induced bleaching. This demonstrates that not only the photo-induced degradation of the solar cell performance is not predominantly caused by the loss in light absorption, but charge transport and collection are also hampered. This is explained by the fact that photo-oxidation of PC70BM causes bonds in its conjugated cage to break, as evidenced by the decreased p* intensity in C1s-NEXAFS spectra of PC70BM films. This degradation of unoccupied states of PC70BM will hinder the transport of photo-generated electrons to the electrode. Surface photovoltage spectroscopy gives direct evidence for gap states at the surface of a PC70BM film, formed after 2 hours of exposure and resulting in upward band bending at the PC70BM/air surface. These observations indicate that the photo-oxidation of PC70BM is likely to be the main cause of the performance degradation observed when the photoactive layer of a TQ1:PC70BM solar cell is intentionally exposed to light in air.
关键词： polymer/fullerene solar cells,photo-oxidation,organic photovoltaics,PC70BM,degradation,trap-assisted recombination,charge transport,TQ1
更新于2025-09-19 17:13:59
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High-Efficiency Nonfullerene Organic Solar Cells Enabled by 1000 nm Thick Active Layers with a Low Trap-State Density
摘要： The high-efficient organic solar cells (OSCs) with thicker active layers are potential candidates for large-area solar panels fabrication. The low charge carrier mobility of the photoactive materials has been identified as the major problem hindering photovoltaic performance of the thick-film OSCs. In this study, high performance of ultra-thick film organic solar cells employing a non-fullerene acceptor BTP-4Cl and a polymer donor PBDB-TF is demonstrated. Two blends (PBDB-TF:BTP-4Cl and PBDB-TF:IT-4F) show comparable mobilities and excellent photovoltaic characteristics in thin-film devices; while in the 1000-nm-thick devices, although they both exhibit desirable and balanced mobilities, the PBDB-TF:BTP-4Cl-based blend possesses lower trap-state density than the IT-4F-based counterpart, leading to lower trap-assist recombination, longer carrier lifetime, and thus a much higher short circuit current density in the device. As a result, the BTP-4Cl-based 1000-nm-thick OSC achieves a remarkable PCE of 12.1%, which greatly outperforms the IT-4F-based devices (4.72%). What is more, for a 1000-nm thick device with active area of 4 cm2, a promising efficiency of 10.1% was obtained, showing its great potential in future large-scale production.
关键词： trap-state density,ultra-thick active layers,high efficiency,non-fullerene organic solar cells,charge carrier mobility
更新于2025-09-19 17:13:59
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A Greenhouse Test to Explore and Evaluate Light-Emitting Diode (LED) Insect Traps in the Monitoring and Control of Trialeurodes vaporariorum
摘要： Population control of small sucking insects has been challenging, and alternative control methods are constantly being sought. Visual traps have long been used to monitor and control pests. Colored sticky cards are widely used for diurnal pests, but their effects are influenced by environmental light conditions. Artificial light traps are mostly used for nocturnal pests. Here, we explored and evaluated light-emitting diode (LED) traps for the monitoring and control of small diurnal sucking insects using greenhouse tests targeting the greenhouse whitefly Trialeurodes vaporariorum. We tested the trapping efficacy of the LED water pan trap, assessed the most attractive LED light and analyzed its efficacy under different weather conditions. The results showed that the LED water pan trap was too inefficient to be useful. Green LEDs were more attractive than yellow LEDs, UV LEDs and green-UV combinations. Regardless of sunny or cloudy conditions, the green LED trap caught more than twice the number of whiteflies than the yellow sticky card alone under summer shading conditions. Our study suggests that LED traps have a significant field application value in whitefly mass trapping and may also be efficient for other diurnal insects. The design of LED traps specific for diurnal insects is discussed.
关键词： phototaxis,attractive light,field evaluation,light trap,environment light intensity
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) - Effect of a-Si on CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> Films and Applications in Perovskite Solar Cells
摘要： In order to reduce size and cost, high-order passive ?lters are generally preferred in power converters to cancel out high-frequency harmonics caused by pulsewidth modulation. However, the ?lter resonance peaks may require the use of passive dampers to stabilize the interactions between the load and source impedances. Furthermore, the stabilizing effect is more dif?cult to be guaranteed for cost-optimized ?lters, which are characterized by low-inductance and high-capacitance passive components. In this paper, several passive ?lter topologies used to interface voltage-source converters with the utility grid are reviewed and evaluated in terms of damping capability, stored energy in the passive components, and power loss in the damping circuit. In addition, the in?uences of different switching frequencies of power converters on the passive ?lter design are discussed in the range 1–15 kHz. Illustrative design examples of the passive ?lters and experimental data are also provided.
关键词： voltage-source converters (VSCs),LC L ?lter,trap ?lter,resonance damping,passive ?lters
更新于2025-09-19 17:13:59
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Cations Functionalized Carbon Nano‐Dots Enabling Interfacial Passivation and Crystallization Control for Inverted Perovskite Solar Cells
摘要： Realizing the full potential of perovskite photovoltaic requires stringent control over nonradiative losses in the devices. Herein, the interfacial carrier recombination of inverted planar perovskite solar cells (PSCs) is suppressed using rationally designed natriumion-functionalized carbon nano-dots (CNDs@Na). The binding effect of carbon dots on Na+ inhibits the interstitial occupancy of alkali cations and reduces the microstrain of the polycrystalline film. Furthermore, modified surface wettability improves the ordering and crystal size of perovskite, which restrains ion diffusion and improves interfacial contact, leading to reduced interfacial charge recombination. Consequently, the effective interfacial passivation and crystallization control enhance the photovoltaic performance and long-term stability of PSCs, resulting in an efficiency of over 20% with negligible hysteresis.
关键词： natriumion-functionalized carbon nano-dots,perovskite solar cells,ion diffusion,trap densities,interface modifications
更新于2025-09-19 17:13:59