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Optimization of Zn Concentration in Chemically Deposited (Cdx-Zn1-x)S Nanocrystalline Films for Solar Cell Applications
摘要： Optimization of Zn Concentration in Chemically Deposited (Cdx-Zn1-x)S Nanocrystalline Films for Solar Cell Applications. An attempt has been made to optimize the Zn concentration in chemically deposited (Cdx-Zn1-x)S (x = 0.2, 0.4, 0.6, 0.8) films on ITO substrate by varying the Cd/Zn composition ratio to enable them to absorb a sizable fraction of solar photons. The phase purity and nano-crystalline character of as-deposited films are established by XRD. Lattice parameters and band-gap values are found to change almost linearly with Cd/Zn composition ratio. The surface morphology supports the nano-crystalline nature of deposited films. The Eg values for (Cdx-Zn1-x)S nanocrystalline films estimated from absorption spectra and corresponding Tauc’s plots range from 2.63 eV to 2.81 eV. The optical behavior in terms of absorption and PL spectra suggests that these films are suitable for application in photovoltaic devices. The electrical resistivity of different (Cdx-Zn1-x)S films has been measured as a function of Zn concentration. The efficiency of resultant CdTe/(Cdx-Zn1-x)S cell is calculated to be approximately 11%.
关键词： Nanocrystalline films,CBD,(Cdx-Zn1-x)S /ITO,solar cell,wide band-gap,window material
更新于2025-09-19 17:13:59
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[IEEE 2019 Thirteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Rome, Italy (2019.9.16-2019.9.21)] 2019 Thirteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Wide Band Polarization Converter Graphene Metasurface for Mid-Infrared Band
摘要： Wide band, insensitive incidence angle graphene metasurface for polarization conversion is introduced in this work. A high Polarization Conversion Ratio (PCR) is verified in Mid-Infrared band by using a graphene as an upper conductor for metasurface. The metasurface construction is composed of a single layer of graphene, which has a half ring slots with rectangular slot connecting between them while the whole shape is rotated with 45o. Silicon dioxide substrate is used with a metal backed ground. The simulation results of the proposed metasurface indicate that a linearly polarized incident wave is converted to a circular polarized one over more than one THz along the Mid-Infrared frequency band. PCR has a maximum value of approximately 98% at 1.45 THz. The polarization conversion ratio is studied for different angles of incidence, with stable value for a wide range of incident angles.
关键词： Insensitive incidence angle,Graphene metasurface,Wide band,Mid-Infrared band,Polarization Conversion Ratio (PCR)
更新于2025-09-16 10:30:52
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Wide band-gap organic molecules containing benzodithiophene and difluoroquinoxaline derivatives for solar cell applications
摘要： Two new semiconducting organic small molecules, namely BDTQ-BDT(EH) and BDTQ-BDT(OC), were prepared by attaching electron accepting 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (DTQ) unit on 2,6-position of electron donating 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b’]dithiophene (BDT(EH)) and 4,8-bis(octyloxy)-benzo[1,2-b:4,5-b’]dithiophene (BDT(OC)) units. Molecule BDTQ-BDT(EH) showed higher thermal stability (5% weight loss temperature, Td “349 jC), slightly lower band-gap (Eg “2.10 eV) and deeper highest occupied molecular orbital energy level (HOMO “–5.36 eV) level compared to those (Td “336 jC, Eg “2.11 eV, and HOMO “–5.30 eV, respectively.) of the molecule BDTQ-BDT(OC). The organic solar cells (OSCs) made with the synthesized molecules as an electron donor and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) as an electron acceptor gave a maximum power conversion efficiency (PCE) of 1.20% and 0.83%, respectively, for BDTQ-BDT(EH) and BDTQ-BDT(OC). This study confirmed that the substituents attached on the 4,8-position of BDT unit greatly alter the properties of the resulting molecules.
关键词： small molecule solar cells,wide band-gap molecules,quinoxaline-based molecules,benzodithiophene-based molecules,organic solar cells
更新于2025-09-16 10:30:52
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TaS <sub/>2</sub> Back Contact Improving Oxide-Converted Cu <sub/>2</sub> BaSnS <sub/>4</sub> Solar Cells
摘要： Solar cells based on the wide band-gap Cu2BaSnS4 (CBTS) photoabsorber have achieved open circuit voltages up to 1.1 V over a short development period, making CBTS an attractive material for tandem photovoltaic and photoelectrochemical cells. In this work, we explore an alternative CBTS growth route based on oxide precursors, and we propose TaS2 as an alternative back contact material to the commonly used Mo/MoS2. The oxide precursor route does not require higher sulfurization temperatures than other more common fabrication routes, and it yields CBTS films with negligible Stokes shift between photoluminescence maximum and band gap energy, while at the same time avoiding sulfur contamination of vacuum systems. The high work-function metallic TaS2 compound is selected as a prospective hole-selective contact, which could also prevent the losses associated with carrier transport across the semiconducting MoS2 layer. By comparing CBTS solar cells with Mo and TaS2 back contacts, the latter shows a significantly lower series resistance, resulting in a 10% relative efficiency improvement. Finally, we fabricate a proof-of-concept monolithic CBTS/Si tandem cell using a thin Ti(O,N) interlayer intended both as a diffusion barrier and as a recombination layer between the two subcells.
关键词： wide band gap absorber,back contact,kesterite,cation substitution,tandem solar cell,silicon,TaS2,sputtering
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - X-Band Waveguide Coupler with Low Ripple and Losses
摘要： A novel wideband coupler operating in the frequency bandwidth from 10.7 GHz to 12.8 GHz is presented. The coupler consists of two crossed rectangular waveguides coupled through four circular apertures with different diameters. In order to improve the operating bandwidth and reduce the coupling ripple across the frequency bandwidth, a Chebyshev distribution is used to determine the radius and distance between the apertures. The coupling coefficient in the operating bandwidth is below -30 dB with less than 0.6 dB ripple. The return loss of all the ports is under -15 dB, and the maximum isolation between ports is below -60 dB. The proposed coupler has the advantage of having small size and low losses, which make it appropriate for high-power applications. The whole structure is simulated and optimized using CST microwave studio software and then fabricated and measured. Excellent agreement between measured and simulated results was achieved.
关键词： directional couplers,wide band couplers,X-band waveguide couplers
更新于2025-09-11 14:15:04
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Wide band-gap Cu <sub/>2</sub> SrSnS <sub/>4</sub> solar cells from oxide precursors
摘要： Recent progress in the efficiency of Cu2ZnSnS4 (CZTS) solar cells has been relatively slow due to severe bulk band tailing issues that have proven difficult to resolve. Band tails in CZTS are caused by defect-related potential fluctuations, as diagnosed by the large shift between the CZTS band gap and its photoluminescence (PL) peak. In this work, we demonstrate that the PL-band gap shift can be decreased roughly by a factor of 5 when Zn is replaced by the heavier cation Sr. The resulting Cu2SrSnS4 compound is of considerable interest for photovoltaics due to its sharp band edges and suitable band gap (1.95-1.98 eV) for a top absorber in tandem cells. Trigonal CSTS thin films are synthesized in this work by sulfurization of strongly Cu-poor co-sputtered Cu2SrSnO4 precursors. The first functioning CSTS solar cells are demonstrated, even though the very high conduction band of CSTS implies that the typical CdS/ZnO electron contact of CZTS solar cells must be redesigned to avoid large voltage losses.
关键词： tail states,tandem solar cell,sputtering,wide band-gap absorber,Kesterite,cation substitution,potential fluctuations
更新于2025-09-11 14:15:04
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An Experimental Demonstration of Short Circuit Protection of SiC Devices
摘要： An experimental demonstration of an effective short circuit protection scheme for SiC MOSFETs is presented in this paper. Measurements of the static characteristics of the SiC device before and after the short circuit events were obtained to evince that the device remained in good health. An ultra-fast short circuit protection scheme is implemented given the observed lower short-circuit withstand of present SiC devices. It is shown that the integrity of the SiC device was protected after one-hundred short circuit events.
关键词： Short-Circuit,MOSFET,Silicon Carbide,Protection,SiC,Wide band-gap
更新于2025-09-10 09:29:36
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[ACM Press the 7th International Workshop - Shenzhen, China (2018.11.04-2018.11.04)] Proceedings of the 7th International Workshop on Real-World Embedded Wireless Systems and Networks - RealWSN'18 - Contactless Breathing Rate Monitoring in Vehicle Using UWB Radar
摘要： Monitoring human vital signs is fundamental to assess a person’s general health and detect events such as respiratory distress or heart attacks. As vehicle driving occupies a considerable part of daily lives, monitoring vital signs of a driver is necessary for early detecting potential health issues during driving. However, it is also important to ensure that the driver is neither distracted nor uncomfortable while monitoring. It is thus a challenge to develop contactless and ubiquitous vital sign monitoring. This paper presents contactless breathing rate monitoring for drivers using an impulse ultra-wide band (UWB) radar. We demonstrate that UWB frequency reflects signals from human body and validate a UWB radar for detecting the minute chest movement. Two signal processing methods are designed and evaluated for on-line and off-line analysis. We investigate 16 different radar positions in a vehicle for robust breathing rate monitoring under the circumstance of body motions during driving. We also perform on-road experiments at a local city and achieve a mean of 1.06 breathing rate estimation error per minute.
关键词： Smart driving,Ultra-wide band,Breathing rate,Healthcare
更新于2025-09-10 09:29:36
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Physical properties of Cd-doped ZnS thin films
摘要： In this research, un- and Cd-doped ZnS nanostructures were synthesized using an electrodeposition method. The electrolyte contained 20 mM ZnCl2, 20 mM Na2S2O3 and the various amounts of CdCl2 solution. The X-ray diffraction (XRD) patterns of the as-deposited samples exhibited that Cd doping lead to decrease the crystallite size (D) of ZnS meanwhile the lattice strain, lattice stress, dislocation density (γ), and stacking fault energy (SF) were increased. Field emission scanning electron microscopy (FESEM) images depicted very fine equiaxed grains (20 to 50 nm), in addition to big grains (200 to 400 nm) with the preferential orientation. The reflectance spectra of ZnS thin films indicated a decrease in the reflectance peaks and refractive index (n), after Cd doping. Based on the transmission spectra, the un- and Cd-doped ZnS samples showed an absorption edge between 328 – 357 nm. The band gap energy for undoped ZnS sample was estimated as 3.95 eV, which it was reduced to 3.63 eV for the Cd-doped ZnS samples owing to the presence of imperfections and crystalline disorder in the Cd-doped samples. Furthermore, the obtained dielectric constant of the Cd-doped ZnS thin films was smaller than undoped ZnS sample, which means that the Cd-doped ZnS samples were more appropriate than the undoped ZnS sample for application in the fast photodetectors. The photoluminescence (PL) spectra of the undoped ZnS thin film was presented six emission peaks at 340, 413, 536, 574, 748, and 878 nm as an outcome of near band emission (NBE) and crystalline defects such as zinc interstitials (IZn), zinc vacancies (VZn), sulfur interstitials (IS), ZnS self-defect, and the defect states between the valence band (VB) and the conduction band (CB) of ZnS. Moreover, the PL emission of the Cd-doped ZnS samples demonstrated a red-shift relative to the undoped sample, which verified the UV-vis spectroscopy results.
关键词： nanostructures,electrodeposition,wide band gap,dielectric constant,Cd-doped ZnS
更新于2025-09-10 09:29:36
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Wide band fractal-based perfect energy absorber and power harvester
摘要： In this article, a novel wide band polarization and incident angle independent meta-material absorber (MA) and energy harvesting applications which operates at C (4GHz-8 GHz) and X (8GHz-12 GHz) is proposed. The unit-cell of the proposed structure based on fractal circle loop. Four lumped resistors are mounted the structure to obtain a broad band absorption characteristics. Resistors increase the absorption characteristic of proposed MA significantly at mentioned frequency ranges. In addition, under favor of the resistors proposed MA can convert absorbed energy from incident wave to appearing power.
关键词： metamaterial,wide band absorber,energy harvesting,fractal metamaterial absorber
更新于2025-09-09 09:28:46