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Temperature Dependence Model of the Laser Diode Bar Current-Voltage Characteristic
摘要： Based on an analysis of di?erences between the experimentally measured temperature dependence of the current-voltage characteristic (I–V curve) of a laser diode bar (LDB) with AlGaAs/GaAs heterostructure and the dependence obtained in accordance with the well-known model of light-emitting diodes, assumptions were made about the sources of these di?erences. The agreement between the experimental and modeled dependences is signi?cantly improved by taking into consideration the change in the resistance of LDB layers caused by temperature change. It is shown that when the injection current is known, the measured voltage drop across the LDB can be used to estimate the temperature of the diode active region in order to implement thermal stabilization for solid-state laser pumping systems based on high-power laser diodes.
关键词： temperature,electrical potential di?erence,laser diode bar,current-voltage characteristic
更新于2025-09-23 15:21:01
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Electrical response in poled (Bi <sub/>0.5</sub> Na <sub/>0.5</sub> ) <sub/>0.935</sub> Ba <sub/>0.065</sub> TiO <sub/>3</sub> ceramics
摘要： A ferroelectric material (Bi0.5Na0.5)0.935Ba0.065TiO3 (BNBT) with a perovskite structure was poled and characterized by electrical impedance spectroscopy as a function of temperature, X-ray diffraction, and Rietveld refinement. The ac conductivity showed a low-frequency dispersion, supporting the idea of heterogeneous potential wells favored by Bi3+, Na+, and Ba2+ on the A site of the perovskite type of structure. The activation energies for ac conduction depend on the studied frequency. The permittivity and electrical modulus showed a distribution of the relaxation time associated with the delay in the orientation of the dipoles and an important contribution to the short-range conductivity.
关键词： electrical behavior,Rietveld refinement,Phase change,dielectric permittivity,BNBT
更新于2025-09-23 15:21:01
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Coupled thermoa??electrical analysis of highly scaled GaN micro-LEDs with meshed hybrid conductors
摘要： Display technology with ultrafine pixels for near-eye application is a rapidly growing field due to the recent emergence of augmented/mixed reality. With the constant demand for high energy efficiency, long lifetime, and high luminosity, micro-LED displays based on compound semiconductors are promising candidates for such applications. However, miniaturizing LEDs results in significant drawbacks in terms of their quantum efficiency, current injection efficiency, and heat extraction. With relatively low device resistance compared to that of liquid crystals or organic LEDs, micro-LEDs are also more susceptible to the effects of parasitic resistance. In this study, gallium nitride based micro-LED displays with very small pixels (5 μm pixel, 10 μm pitch) are fabricated to study the thermal–electrical effect of meshed hybrid conductors on the optical emission efficiency. In situ thermographic imaging with I–V measurement confirms a significant trade-off among heat transfer, electrical conductivity, and light extraction efficiency. An increase of 37.9 % in the emission efficiency (2,540 PPI, 5 μm pixels, 1 mm2 display, at 49.2 ℃) is achieved by optimizing the thermal and electrical conduction paths. This study experimentally confirms the importance of thermal management and multi-physics analysis in designing ultra-small-pixel micro-LEDs with high energy efficiency.
关键词： hybrid transparent conductor,Thermo–electrical analysis,gallium nitride,micro-LED
更新于2025-09-23 15:21:01
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Structural and Electrical Investigation of Cobalt-Doped NiOx/Perovskite Interface for Efficient Inverted Solar Cells
摘要： Inorganic hole-transporting materials (HTMs) for stable and cheap inverted perovskite-based solar cells are highly desired. In this context, NiOx, with low synthesis temperature, has been employed. However, the low conductivity and the large number of defects limit the boost of the e?ciency. An approach to improve the conductivity is metal doping. In this work, we have synthesized cobalt-doped NiOx nanoparticles containing 0.75, 1, 1.25, 2.5, and 5 mol% cobalt (Co) ions to be used for the inverted planar perovskite solar cells. The best e?ciency of the devices utilizing the low temperature-deposited Co-doped NiOx HTM obtained a champion photoconversion e?ciency of 16.42%, with 0.75 mol% of doping. Interestingly, we demonstrated that the improvement is not from an increase of the conductivity of the NiOx ?lm, but due to the improvement of the perovskite layer morphology. We observe that the Co-doping raises the interfacial recombination of the device but more importantly improves the perovskite morphology, enlarging grain size and reducing the density of bulk defects and the bulk recombination. In the case of 0.75 mol% of doping, the bene?cial e?ects do not just compensate for the deleterious one but increase performance further. Therefore, 0.75 mol% Co doping results in a signi?cant improvement in the performance of NiOx-based inverted planar perovskite solar cells, and represents a good compromise to synthesize, and deposit, the inorganic material at low temperature, without losing the performance, due to the strong impact on the structural properties of the perovskite. This work highlights the importance of the interface from two di?erent points of view, electrical and structural, recognizing the role of a low doping Co concentration, as a key to improve the inverted perovskite-based solar cells’ performance.
关键词： hole transport material,inverted planar perovskite solar cell,perovskite morphology,Co-doped NiOx,electrical conductivity
更新于2025-09-23 15:21:01
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Proposal of Photonic Analog-to-digital Conversion Using Weighted Multiwavelength Pulses and Balanced Photodetector
摘要： Nowadays, enhanced knowledge of the nature of the electricity demand is achieved through the progressively increasing deployment of smart meters and advanced data analysis techniques. One of the major challenges is to exploit this knowledge to support the introduction of strategies to modify the demand according to relevant objectives to be achieved, like users’ participation in demand response programmes. A key point for facing this challenge is to characterize the demand flexibility. In spite of many discussions about the concept of flexibility, the few mathematical definitions of flexibility available do not address the variation in time of the overall demand aggregation. This paper starts from the analysis of time-variable patterns of aggregate residential customers, ending up with suitable definitions of expected flexibility for aggregate demand. These definitions are based on assessing positive and negative pattern variations and are identified from the analysis of the collective behavior of the aggregate users. A set of results is shown for different numbers of aggregate customers, by considering different values of the averaging time step for load pattern representation.
关键词： binomial probability,customers,demand flexibility,Aggregate demand,electrical load,demand response,load variation pattern,maximum likelihood estimation
更新于2025-09-23 15:21:01
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[IEEE 2019 International Workshop on Fiber Optics in Access Networks (FOAN) - Sarajevo, Bosnia and Herzegovina (2019.9.2-2019.9.4)] 2019 International Workshop on Fiber Optics in Access Networks (FOAN) - Single-Loop Opto-electronic Oscillator at 10.4 GHz with a cascaded Microstrip Bandpass Filter Configuration
摘要： The opto-electronic oscillator is a well-known microwave photonic device that produces high-frequency signals in the microwave range. One of the main advantages of the opto-electronic oscillator is that it produces high-frequency signals with low phase noise thanks to the resonator’s properties. In most cases the opto-electronic oscillator faces the problem of generating side modes besides the oscillation signal due to non-ideal filtering. In this paper we propose a solution for the additional suppression of these undesired harmonics using a combination of two slightly detuned bandpass microstrip filters. We report an improvement for the side-mode suppression ratio about 8.3 dB with a single-loop 90-m-long opto-electronic oscillator at 10.4 GHz.
关键词： electrical bandpass filter,side-mode suppression ratio,cascaded filter connection,side modes,opto-electronic oscillator
更新于2025-09-23 15:21:01
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Vital role of Ar ambient pressure in controlled properties of nanocrystalline CdS thin films
摘要： A report on the manipulation of structural, optical, and electrical properties of nanocrystalline CdS (ncCdS) thin films in the framework of varying Ar ambient pressure in pulsed laser deposition (PLD) is presented here. Increase in Ar ambient pressure results in reduction of crystallite size which in turns increases the structural imperfections and structural phase transformation of ncCdS thin films. The most significant observation here is the bleaching of multiphonon Raman modes (MRMs) particularly LO + 2E2, 2LO + 2E2, etc. in ncCdS thin films. An acute investigation on the reason of bleaching of LO + 2E2, 2LO + 2E2, etc. modes is carried out here and concluded that it is due to the fading of E2 mode with increasing Ar pressure as confirmed by low-frequency micro-Raman measurements. UV–visible absorption and photoluminescence spectroscopies are used to examine the optical properties like bandgap and possible electronic transitions in ncCdS thin films. Further, transport properties of ncCdS thin films are investigated using Hall measurement and I–V characteristics.
关键词： electrical properties,optical properties,Ar ambient pressure,structural properties,pulsed laser deposition,nanocrystalline CdS thin films
更新于2025-09-23 15:21:01
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Percolation dependent conducting behavior of poly (3,4-ethylenedioxythiophene): Poly (styrenesulfonate) in the presence of cationic polyelectrolyte
摘要： Conductivity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films is highly modified in the presence of cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDADMAC). In-plane electrical conductivity of the thin films of PEDOT:PSS and PDADMAC complex (designated as PED*PDA) are measured for one to five layers, i.e., (PED*PDA)1 to (PED*PDA)5 films prepared by spin-coating method and compared with the pristine PEDOT:PSS films. In addition, PDADMAC and PEDOT:PSS is spin coated on each other to form a bilayer unit (designated as PDA/PED) and one to five layers of such PDA/PED unit, i.e., (PDA/PED)1 to (PDA/PED)5 films are formed by alternate deposition and the conductivity is compared with the complex films. In-plane conductivity of PED*PDA is drastically higher than the pristine PEDOT:PSS and is nearly independent of the layer number, i.e., thickness of the film. However, for PDA/PED films, behavior of conductivity is different in comparison with that of the complex films as the conductivity is found to increase for (PDA/PED)1 to (PDA/PED)2 and then decreases from (PDA/PED)3 to (PDA/PED)5 respectively. With the increase of the applying voltage, the linear nature of I-V curves remain unchanged. The structure, morphology and mechanism of conductivity enhancement are investigated through various characterization techniques. The strong electrostatic attachment between anionic PSS part of PEDOT:PSS and cationic PDADMAC is responsible for the drastic enhancement of conductivity as the percolation pathway enhances.
关键词： PEDOT:PSS,Thin films,Polyelectrolyte,FTIR,Electrical behavior,XRD
更新于2025-09-23 15:21:01
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Thermal management of concentrator photovoltaic systems using nanoa??enhanced phase change materialsa??based heat sink
摘要： Temperature regulation of concentrator photovoltaic systems is essential in reducing operating temperatures with higher system performance. A new nano-enhanced phase change material, with multi-cavity heat sinks, integrated with a concentrator photovoltaic (CPV) system is developed. The multi-cavity heat sink includes a single-, triple-, and quintuple-cavity configuration in both parallel and series pattern filled with n-octadecane PCM and graphene nanoparticle additives with 2% and 5 wt%. Numerical simulations are performed using the developed two-dimensional model for photovoltaic layers integrated with the nano-enhanced phase change material-based heat sink. The predicted results are compared with the available numerical results and measurements. Results indicate that increasing the number of parallel cavities, along with weight fraction of nanoparticles, significantly improves the thermal conductivity, and consequently attains better performance for the CPV system. Using a parallel quintuple-cavity configuration, with 5 wt% NPCM, achieves maximum reduction in the solar cell mean temperature along with the best temperature uniformity compared to other configurations. At a concentration ratio of 20, the thermal efficiency is 65%, the electrical efficiency is about 10%, and the output electrical power of the system is 235 W per m width of the cell. On the contrary, using a series pattern of the heat sink has an unfavorable effect on the mean solar cell temperature, as well as on electrical efficiency and thermal performance of the CPV system. The obtained result can assist in identifying the best possible design of the heat sink in addition to the most appropriate selection of PCM and nanoparticle additives.
关键词： electrical efficiency,graphene nanoparticles,concentrator photovoltaic system,multi-cavity heat sink,nano-enhanced phase change materials
更新于2025-09-23 15:21:01
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Electrical properties of thin films deposited from TMS/O <sub/>2</sub> in Microwave Multipolar Plasma reactor
摘要： Thin films have been deposited from pure Tetramethylsilane and a mixture of Tetramethylsilane and oxygen (TMS/O2). The addition of oxygen proportion to Tetramethylsilane vapors leads to the change in film structure which varies from organic to inorganic character close to SiOx-like film [1]. The electrical characterisation using Metal-Insulating-Metal structure permits the study of current-voltage (I (V)) curves behaviours. The results suggest that the carrier transport in the deposited films is limited by a space charge conduction mechanism.
关键词： Thin films,Oxygen,Space charge conduction,Electrical properties,Tetramethylsilane
更新于2025-09-23 15:21:01