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Sidewall profile dependent nanostructured ultrathin solar cells with enhanced light trapping capabilities
摘要： Theoretical studies of ultra-thin silicon solar cells with cylindrical, conical and parabolic surface nanostructures inherited from natural self-assembled anodic alumina oxide (NSA-AAO) were performed by finite-difference time-domain (FDTD) method. All nanostructured solar cells obtained an optimized efficiency enhancement as high as more than 33% comparing with that of the anti-reflective (AR) one. Numerical results reveal that the range of efficient structural parameters for the nanostructured (e.g. cylindrical) solar cell can be effectively enlarged as the period of the nanostructure changes from 0.1 μm to 0.5 μm. Moreover, the improvements of absorption photocurrent density (Jph) in conical and parabolic nanostructured solar cells are comparable with the cylindrical nanostructured one but less sensitive to the fill factor and structural height in the whole simulation region of 0.1-0.9 and 0-0.25 μm, respectively. Equivalent refractive index models were used to analysis the antireflection performance of surface nanostructures from the point of view of sidewall profiles. Resonance modes induced through nanostructures have greatly improved the absorptance of solar cells in broadening wavelength bands which consequently raised the Jph. This study serves as a way for the practical design and application of AAO nanostructure based high-efficiency ultra-thin solar cells.
关键词： Solar cell,Nanostructure,Light trapping
更新于2025-09-16 10:30:52
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Structurally colored stainless steel processed by using femtosecond laser pulses
摘要： Structurally colored stainless steel (SS) surfaces were produced by using femtosecond laser at normal incidence at ambient conditions. The influence of laser polarization on the surface properties was investigated. The surface morphologies, roughness and color of the laser-treated surface were characterized by using environmental scanning electron microscope (ESEM), roughmeter and atomic force microscope (AFM). Results indicated that the circular polarization leads to more random structures than the horizontally linear polarization. Specimen with the highest surface roughness shows the brightest color. Different colors are cyclically exhibited by changing view angles due to different orders of diffraction. This investigation developed the technique of using femtosecond laser in situ preparation of periodic structures on 304 SS, and indicating that laser polarization is an important parameter to control surface structures to achieve different colors.
关键词： polarization,micro/nanostructure,coloration,Femtosecond laser,stainless steel
更新于2025-09-16 10:30:52
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Coherent light matter interactions in nanostructure based active semiconductor waveguides operating at room temperature
摘要： Light matter coherent interactions require that the coherent state induced in the matter be maintained for the duration of the observation. The only way to induce and observe such interactions in room temperature semiconductors, where the coherence time is of the order of a few hundred femtoseconds, is to use ultrashort pulse excitations and an ultrafast characterization technique. For media comprising an ensemble of nanostructure semiconductors such as self-assembled quantum dots, the gain broadening inhomogeneity also affects the interaction. Moreover, when gain media in the form of an active waveguide, such as optical amplifiers, are used, the interaction is distributed and includes nonresonant incoherent phenomena that occur simultaneously with the coherent effects. Such a complex system can exhibit, nevertheless, clear coherent interactions even at room temperature. Using InAs/InP quantum dot and wirelike quantum dash amplifiers, Rabi oscillations, self-induced transparency, coherent control using spectral pulse shaping, Ramsey interference, and photon echo have been demonstrated. The characterization employed cross frequency resolved optical gating, and the experiments were accompanied by a comprehensive finite difference time domain model that solves the Maxwell and Lindblad equations. This work has major implications on the understanding of the details of dynamical processes in active semiconductor devices, on short pulse generation from semiconductor lasers, and on various future quantum devices.
关键词： active semiconductor waveguides,coherent control,self-induced transparency,Rabi oscillations,coherent light matter interactions,nanostructure,Ramsey interference,photon echo,room temperature
更新于2025-09-16 10:30:52
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Reduced bacterial adhesion on zirconium-based bulk metallic glasses by femtosecond laser nanostructuring
摘要： As high-performing materials, bulk metallic glasses have attracted widespread attention for biomedical applications. Herein, the bacterial adhesion properties of femtosecond laser-nanostructured surfaces of four types of zirconium-based bulk metallic glasses are assessed. Laser-induced periodical surface structures and nanoparticle structures were fabricated by femtosecond laser irradiation under different energy intensities (0.23 and 2.3 J/mm2). Surface topography, roughness, wettability, and surface energy were investigated after femtosecond laser irradiation and the surface bacterial adhesion properties were explored using Escherichia coli and Staphylococcus aureus as respective representatives of Gram-negative and Gram-positive bacteria. 4#,6-Diamidino-2-phenylindole fluorescence staining was used to characterize and assess the bacterial surface coverage rate. The in vitro cytotoxicity of polished and laser-nanostructured surfaces was investigated using MC3T3-E cells. The obtained results demonstrate that femtosecond laser surface nanostructuring retained the amorphous structure of zirconium-based bulk metallic glasses and led to an obvious decrease in bacterial adhesion compared with polished surfaces. The inhibition of bacterial adhesion on laser-induced periodical surface structures was greater than on nanostructured surfaces after 24 h of bacterial incubation. In addition, femtosecond laser nanostructuring did not have an apparent effect on the cytotoxicity of zirconium-based bulk metallic glasses.
关键词： femtosecond laser,Bacterial adhesion,nanostructure,bulk metallic glass
更新于2025-09-16 10:30:52
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TiN-contained polymer-metal core-shell structured nanocone array: Engineering of sensor performance by controlling plasmonic properties
摘要： Metal nanostructures have great potential for optical label-free biosensors based on localized surface plasmon resonance (LSPR). The sensitivity of a metal nanostructure-based label-free biosensor (i.e., plasmonic sensor) depends on its plasmonic properties, which su?er a decrease in sensitivity by energy losses in the metal material. Here, we demonstrate an approach to improve the plasmonic properties of metal nanostructures by controlling the carrier density in the base polymer material using titanium nitride (TiN). It is expected that the light energy absorbed by TiN is converted into excitons, and it will assist LSPs in the metal nanostructure; thus, the losses of the metal material are compensated by the excitons excited in TiN. We designed a TiN-contained polymer-metal core-shell structured nanocone array (NCA), comprising TiN nanoparticles (NPs) in a polymer core and metal shell (Au or Ag), and realized improvement of the refractive index (RI) sensitivity of a label-free biosensor by optimizing the TiN-contained polymer composition. As a result, the TiN-contained polymer-metal NCA, with a TiN NP concentration of 10 wt% in the polymer core, had a 1.5-fold higher RI sensitivity than that of the same NCA without TiN NPs. The results of the resistance measurement of the metal surface with the TiN NP-contained polymer (10 wt%) under light exposure suggest the conversion of exposed light into LSPs of metal via TiN. It is suggested that plasmonic properties and sensor performances can be improved by the presented approach. Moreover, in DNA hybridization detection, an extremely low limit of detection of 117.5 fM was achieved.
关键词： Localized surface plasmon resonance (LSPR),Core-shell nanostructure,DNA detection,Carrier engineering,Biosensor,Titanium nitride
更新于2025-09-16 10:30:52
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High-efficiency solar thermophotovoltaic system using a nanostructure-based selective emitter
摘要： In this work, we present the design, fabrication, optimization, and experimental results of a high-efficiency planar solar thermophotovoltaic (STPV) system utilizing a micro-textured absorber and a nanostructure multi-layer metal-dielectric coated selective emitter fabricated on a tungsten (W) substrate. Light absorptance of more than 90% was achieved at visible and near-infrared wavelengths using the microtextured absorbing surface. The nanostructure selective emitter consists of two thin-film optical coatings of silicon nitride (Si3N4) and a layer of W in between to increase the surface emissivity in spectral regimes matching the quantum efficiency of the thermophotovoltaic (TPV) cells. Gallium antimonide (GaSb)-based TPV cells are used in our STPV design. The experiment was conducted at different operating temperatures using a high-power continuous wave laser diode stack as a simulated source of concentrated incident radiation. Our experimental setup measured a maximum electrical output power density of 1.71 W/cm2 at 1676 K STPV temperature, and the overall power conversion efficiency of 8.4% after normalizing the output power density to the emitter area. This is the highest STPV system efficiency reported so far for any experimental STPV device. The incident optical laser power on the absorber side was 131 W. This is equivalent to a solar concentration factor of ~2100, which is within the practical limit and readily achievable with Fresnel lens setup.
关键词： Spectral control,TPV cells,Nanostructure,STPV,Blackbody
更新于2025-09-16 10:30:52
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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) - Photon Management for Silicon Solar Cells featuring Hole-Selective Molybdenum Oxide Rear Contacts: An Optical Simulation Study
摘要： Passivated, hole-selective contacts play important role in reducing surface recombination by lowering the concentration of electrons in the rear side of a solar cell. However, parasitic optical losses in these contacts can still limit the performance of the cell. In this work, the long wavelength optical losses of silicon solar cells featuring hole-selective molybdenum oxide (MoOx) rear contacts are investigated using optical simulations. The potential of these selective contacts for possible enhancement of photogenerated current density was also investigated for their use with nanostructured dielectric layers.
关键词： photon management,FDTD simulation,grating nanostructure,silicon solar cell,hole selective contact
更新于2025-09-16 10:30:52
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Plasmon-Emitter Hybrid Nanostructures of Gold Nanorod-Quantum Dots with Regulated Energy Transfer as a Universal Nano-Sensor for One-step Biomarker Detection
摘要： Recently, biosensing based on weak coupling in plasmon-emitter hybrid nanostructures exhibits the merits of simplicity and high sensitivity, and attracts increasing attention as an emerging nano-sensor. In this study, we propose an innovative plasmon-regulated fluorescence resonance energy transfer (plasmon-regulated FRET) sensing strategy based on a plasmon-emitter hybrid nanostructure of gold nanorod-quantum dots (Au NR-QDs) by partially modifying QDs onto the surfaces of Au NRs. The Au NR-QDs showed good sensitivity and reversibility against refractive index change. We successfully employed the Au NR-QDs to fabricate nano-sensors for detecting a cancer biomarker of alpha fetoprotein with a limit of detection of 0.30 ng/mL, which displays that the sensitivity of the Au NR-QDs nano-sensor was effectively improved compared with the Au NRs based plasmonic sensing. Additionally, to demonstrate the universality of the plasmon-regulated FRET sensing strategy, another plasmon-emitter hybrid nano-sensor of Au nano-prism-quantum dots (Au NP-QDs) were constructed and applied for detecting a myocardial infarction biomarker of cardiac troponin I. It was first reported that the change of absorption spectra of plasmonic structure in a plasmon-emitter hybrid nanostructure was employed for analytes detection. The plasmon-regulated FRET sensing strategy described herein has potential utility to develop general sensing platforms for chemical and biological analysis.
关键词： localized surface plasmon resonance,quantum dot,gold nanorod,biomarker,fluorescence resonance energy transfer,plasmonic-emitter hybrid nanostructure
更新于2025-09-16 10:30:52
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Interfacial Capillarya??Forcea??Driven Selfa??Assembly of Monolayer Colloidal Crystals for Supersensitive Plasmonic Sensors
摘要： Colloidal lithography technology based on monolayer colloidal crystals (MCCs) is considered as an outstanding candidate for fabricating large-area patterned functional nanostructures and devices. Although many efforts have been devoted to achieve various novel applicatons, the quality of MCCs, a key factor for the controllability and reproducibility of the patterned nanostructures, is often overlooked. In this work, an interfacial capillary-force-driven self-assembly strategy (ICFDS) is designed to realize a high-quality and highly-ordered hexagonal monolayer MCCs array by resorting the capillary effect of the interfacial water film at substrate surface as well as controlling the zeta potential of the polystyrene particles. Compared with the conventional self-assembly method, this approach can realize the reself-assembly process on the substrate surface with few colloidal aggregates, vacancy, and crystal boundary defects. Furthermore, various typical large-scale nanostructure arrays are achieved by combining reactive ion etching, metal-assisted chemical etching, and so forth. Specifically, benefiting from the as-fabricated high-quality 2D hexagonal colloidal crystals, the surface plasmon resonance (SPR) sensors achieve an excellent refractive index sensitivity value of 3497 nm RIU?1, which is competent for detecting bovine serum albumin with an ultralow concentration of 10?8 m. This work opens a window to prepare high-quality MCCs for more potential applications.
关键词： colloidal lithography,plasmonic sensors,monoloidal colloidal self-assembly,nanostructure arrays,interfacial capillary force
更新于2025-09-16 10:30:52
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Nonlinear Spectroscopy on the Plasmonic Analog of Electromagnetically Induced Absorption: Revealing Minute Structural Asymmetries
摘要： Tailoring not only the linear but also the nonlinear properties of plasmonic structures has been a longstanding idea. The plasmonic dolmen structure with its many degrees of freedom in design has been of particular interest. We are investigating this system in detail in the retarded weak-coupling regime, the so-called plasmonic analog of electromagnetically induced absorption. While it is generally expected that the enhanced absorbance leads to an increased nonlinear generation, we find that the details are more complex. A thorough wavelength and polarization resolved study reveals two distinct nonlinear contributions. Our nonlinear spectroscopy method exhibits a surprisingly high sensitivity to minute structural asymmetries. Our experimental results are corroborated by finite-element simulation. We envision that our findings will stimulate further research into phase tuning, structural symmetries, and manipulation in nonlinear plasmonic systems in order to fully exploit the ability to tailor the linear and specifically the nonlinear optical properties of nanostructured matter.
关键词： spectroscopy,structural asymmetry,Nonlinear plasmonics,3D nanostructure,electromagnetically induced absorption,nonlinear spectroscopy
更新于2025-09-16 10:30:52