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In Situ Raman Spectroscopy on Silicon Nanowire Anodes Integrated in Lithium Ion Batteries
摘要： Rapid decay of silicon anodes during lithiation poses a significant challenge in application of silicon as an anode material in lithium ion batteries. In situ Raman spectroscopy is a powerful method to study the relationship between structural and electrochemical data during electrode cycling and to allow the observation of amorphous as well as liquid and transient species in a battery cell. Herein, we present in situ Raman spectroscopy on high capacity electrode using uncoated and carbon-coated silicon nanowires during first lithiation and delithiation cycle in an optimized lithium ion battery setup and complement the results with operando X-ray reflection diffraction measurements. During lithiation, we were able to detect a new Raman signal at 1859 cm?1 especially on uncoated silicon nanowires. The detailed in situ Raman measurement of the first lithiation/delithiation cycle allowed to differentiate between morphology changes of the electrode as well as interphase formation from electrolyte components.
关键词： silicon nanowires,lithium ion batteries,in situ Raman spectroscopy,operando XRD,solid electrolyte interphase
更新于2025-09-19 17:15:36
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Structural and Optical Properties of Silicon Nanowire Arrays Fabricated by Metal Assisted Chemical Etching With Ammonium Fluoride
摘要： Here we report on the metal assisted chemical etching method of silicon nanowires (SiNWs) manufacturing, where the commonly used hydrofluoric acid (HF) has been successfully replaced with ammonium fluoride (NH4F). The mechanism of the etching process and the effect of the pH values of H2O2: NH4F solutions on the structural and optical properties of nanowires were studied in detail. By an impedance and Mott-Schottky measurements it was shown that silver-assisted chemical etching of silicon can be attributed to a facilitated charge carriers transport through Si/SiOx/Ag interface. It was shown that the shape of nanowires changes from pyramidal to vertical with pH decreasing. Also it was established that the length of SiNW arrays non-linearly depends on the pH for the etching time of 10 min. A strong decrease of the total reflectance to 5–10% was shown for all the studied samples at the wavelength <800 nm, in comparison with crystalline silicon substrate (c-Si). At the same time, the intensities of the interband photoluminescence and the Raman scattering of SiNWs are increased strongly in compare to c-Si value, and also they were depended on both the length and the shape of SiNW: the biggest values were for the long pyramidal nanowires. That can be explained by a strong light scattering and partial light localization in SiNWs. Hereby, arrays of SiNWs, obtained by using weakly toxic ammonium fluoride, have great potential for usage in photovoltaics, photonics, and sensorics.
关键词： silicon nanowires,Raman scattering,impedance,photoluminescence,total reflectance
更新于2025-09-19 17:15:36
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Broadband Anti-Reflection in Black Silicon Fabricated by Two-Step Silver-Assisted Wet Chemical Etching for Photovoltaics
摘要： This paper reports broadband anti-reflection in black silicon (b-Si) fabricated by two-step metal-assisted chemical etching (MACE) for potential photovoltaic (PV) applications. The method involves deposition of silver nanoparticles (Ag NPs) in aqueous solution of HF:AgNO3, followed by etching in HF:H2O2:DI H2O solution for different duration (10-25 s). Effects of etching time towards surface morphological and optical properties of b-Si nanowires are investigated. Surface morphological characterization confirms presence of b-Si nanowires with heights of 350-570 nm and diameter of 150-300 nm. The b-Si nanowires exhibit outstanding broadband anti-reflection due to refractive index grading effect. This is represented as weighted average reflection (WAR) in the 300-1100 nm wavelength region. After 20 s of etching, b-Si nanowires with height of 570 nm and width of about 200 nm are produced. The nanowires demonstrate WAR of 5.5%, which represents the lowest WAR in this investigation. This results in absorption of 95.6% at wavelength of 600 nm. The enhanced broadband light absorption yields maximum potential short-circuit current density (Jsc(max)) of up to 39.7 mA/cm2, or 51% enhancement compared to c-Si reference. This facile b-Si fabrication method for broadband enhanced anti-reflection could be a promising technique to produce potential PV devices with high photocurrent.
关键词： black silicon,nanowires,silver-assisted etching,refractive index grading,anti-reflection
更新于2025-09-19 17:13:59
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SiNW/C@Pt Arrays for High-Efficiency Counter Electrodes in Dye-Sensitized Solar Cells
摘要： Modern energy needs and the pressing issue of environmental sustainability have driven many research groups to focus on energy-generation devices made from novel nanomaterials. We have prepared platinum nanoparticle-decorated silicon nanowire/carbon core–shell nanomaterials (SiNW/C@Pt). The processing steps are relatively simple, including wet chemical etching to form the silicon nanowires (SiNWs), chemical vapor deposition to form the carbon shell, and drop-casting and thermal treatment to embed platinum nanoparticles (Pt NPs). This nanomaterial was then tested as the counter electrode (CE) in dye-sensitized solar cells (DSSCs). SiNW/C@Pt shows potential as a good electrocatalyst based on material characterization data from Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Raman spectroscopy shows that the surface reactivity of the SiNW/C is increased by the decoration of Pt NPs. These data also show that the carbon shell included both graphitic (sp2 hybridization) and defective (sp3 hybridization) phases of carbon. We achieved the minimum charge-transfer resistance of 0.025 ? · cm2 and the maximum ef?ciency of 9.46% with a symmetric dummy cell and DSSC device fabricated from the SiNW/C@Pt CEs, respectively.
关键词： core–shell,defective carbon,electrocatalytic activity,dye-sensitized solar cells (DSSCs),counter electrodes (CEs),silicon nanowires (SiNWs)
更新于2025-09-16 10:30:52
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Whispering gallery modes enhance the near-infrared photoresponse of hourglass-shaped silicon nanowire photodiodes
摘要： Silicon photodiodes are widely used in applications that require the measurement of the intensity, colour and position of visible light. Silicon is an attractive material for these systems owing to its low cost, low noise, and easy on-chip integration with read-out electronics. However, silicon cannot effectively be used to detect near-infrared (NIR, at wavelengths of 700–1,000 nm) light and short-wave infrared (SWIR, 1,000–1,700 nm) light because of its bandgap of 1.12 eV, which is equivalent to a wavelength of 1,100 nm. Here, we report silicon photodiodes based on hourglass-shaped silicon nanowires that use whispering-gallery-mode resonances to enhance their photoresponse in the NIR–SWIR region of the spectrum. The upper, inverted nanocone of the nanowires increases absorption probability by extending the dwell time of NIR–SWIR photons via the generation of whispering-gallery-mode resonances, whereas the lower nanocone with its low reflectance reabsorbs the light incident from surrounding nanowires. Our devices exhibit a higher responsivity and external quantum efficiency than existing silicon photodiodes at 700–1,100 nm. Furthermore, the responsivity at 1,000 nm is similar to that of commercial InGaAs photodiodes and light at 1,400 nm can also be detected. Using our devices, we demonstrate a heart-rate measurement system that offers performance comparable to commercial setups.
关键词： silicon photodiodes,whispering-gallery-mode resonances,short-wave infrared,near-infrared,hourglass-shaped silicon nanowires
更新于2025-09-12 10:27:22
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Transparent multispectral photodetectors mimicking the human visual system
摘要： Compact and lightweight photodetection elements play a critical role in the newly emerging augmented reality, wearable and sensing technologies. In these technologies, devices are preferred to be transparent to form an optical interface between a viewer and the outside world. For this reason, it is of great value to create detection platforms that are imperceptible to the human eye directly onto transparent substrates. Semiconductor nanowires (NWs) make ideal photodetectors as their optical resonances enable parsing of the multi-dimensional information carried by light. Unfortunately, these optical resonances also give rise to strong, undesired light scattering. In this work, we illustrate how a new optical resonance arising from the radiative coupling between arrayed silicon NWs can be harnessed to remove reflections from dielectric interfaces while affording spectro-polarimetric detection. The demonstrated transparent photodetector concept opens up promising platforms for transparent substrates as the base for opto-electronic devices and in situ optical measurement systems.
关键词： augmented reality,wearable technologies,transparent photodetectors,silicon nanowires,spectro-polarimetric detection
更新于2025-09-12 10:27:22
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Development of Textured Electrode, Index Matching Layer and Nanostructured Materials for Light Trapping inside Photovoltaic devices
摘要： In order to reduce the energy harvesting cost, numerous efforts have been made to replace crystalline silicon solar cells with thin film based solar cells. The device efficiency of thin film photo-voltaic devices needs to be improved. Currently, surface texturing based light trapping technologies have been used to improve the device efficiency of photo-voltaic devices. In this paper, we demonstrate experimentally that surface textured hydrogenated ZnO:Al films as transparent conducting oxide (TCO) electrode and nanostructured materials in solar cells improve the anti-reflection properties of TCO coated glass substrate. These surfaces scatter the incident light inside the active layer of solar cells. Scattering of light on textured and nanostructured surface causes increase in average light path length inside active layer which results in increased absorption coefficient. Amorphous silicon solar cells fabricated on textured TCO layer show increase in device efficiency. Silicon nitride film was used as index matching layer between glass and TCO and increase in transmittance was observed. Silicon nanowires were grown using PECVD for their application in solar cells. Metal (Indium) nanoparticles were used for plasmonic light trapping inside solar cells. It was observed that textured TCO, index matching layer and plasmonic nanoparticles techniques improve the device efficiency while nanowires based devices need more optimization to get higher efficiency.
关键词： Plasmonic Light Trapping,Nano-Particles,Thin Film Solar Cell,Surface Texturing,Silicon Nanowires
更新于2025-09-12 10:27:22
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Carbon@Tellurium Nanostructures Anchored to a Si Nanowire Scaffold with an Unprecedented Liquid-Junction Solar Cell Performance
摘要： Silicon nanowire (SiNW) arrays offer a range of exciting opportunities, from maximizing solar spectrum utilization for high-performance liquid-junction solar cells (LJSCs) to functioning as potential micro-supercapacitors in the near future. This work, contrasting strongly with the previously reported studies on SiNW-based LJSCs where electron-conducting nanoparticles of Pt or Au were employed to achieve high efficiencies, aims at tethering relatively inexpensive, hole-conducting, and photoresponsive carbon-coated tellurium nanorods (C@TeNRs) to SiNWs in the quest to achieve an outstanding solar cell performance. A SiNW LJSC (control cell) with a SiNWs/Br?, Br2/carbon-fabric architecture delivers a power conversion efficiency (PCE) of 4.8%. Further, by anchoring C@TeNRs, along the lengths of SiNWs via electrophoresis, a PCE of ～11.6% is attained for a C@TeNRs@SiNWs/Br?, Br2/carbon-fabric-based LJSC. The multifunctionality of C@Te comes to the fore in this cell where (1) the p-type (hole) conducting nature of C@Te ensures efficient charge separation by rapidly collecting holes from SiNWs (and suppresses recombination), (2) the C@TeNRs are also photoresponsive and increase light-harvesting, and (3) the C coating restricts the chemical corrosion and photo-oxidation of SiNWs and the Te core by the acidic electrolyte, thereby improving the cell’s operational lifetime. This LJSC also serves as an effective stand-alone energy-storage device giving an improved areal specific capacitance of 1605 μF cm?2 (at 1 mA cm?2). This study unravels the pivotal role played by C@TeNRs in controlling the performance of SiNW-based LJSCs.
关键词： tellurium nanorods,solar cell,liquid junction,high efficiency,silicon nanowires
更新于2025-09-12 10:27:22
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Light intensity and spectral dependence characteristics of silicon nanowire/PEDOT:PSS heterojunctions solar cells
摘要： Recently, research on Si/conducting organic polymer heterojunction solar cells has gained prominence owing to their low fabrication cost and potential for reasonably good efficiency. Poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated over n-type Si forms such heterojunction which has theoretical capabilities comparable to the conventional p-n Si junction. However these devices still need fabrication parameters optimization in order to compete with conventional p-n junction silicon solar cells. Here, we report the photoresponse of Ag/PEDOT:PSS/n-SiNW/Al solar cell at different light intensities and different wavelengths. The device is fabricated by spin coating the PEDOT:PSS over n-Si NW based Si substrates. It is further noted that the short circuit current is significantly lower in J-V response than that derived from external quantum efficiency measurements. It is observed that the photocurrent density and fill factor deteriorates significantly at higher intensities. This is suggestive of some space charge build up at Si-PEDOT:PSS interface at higher intensities because of difference in hole mobility in Si and PEDOT:PSS. This could also be strongly attributed to structural changes in the PEDOT:PSS layer which might change the charge carrier dynamics and hence the electrical response of the layer. The response of cell with varying intensity can help to optimize the illumination condition for the cell. The wavelength response of the cell can help us better understand the solar cell working and can help in optimizing the fabrication parameters. This opens up new area of intensive research required in order to optimize polymer layer properties and improving the performance of PEDOT:PSS/SiNW-based solar cell.
关键词： PEDOT:PSS,Hetero-junction solar cells,Silicon nanowires,Light trapping
更新于2025-09-12 10:27:22
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The Elastic Property of Bulk Silicon Nanomaterials through an Atomic Simulation Method
摘要： This paper reports a systematic study on the elastic property of bulk silicon nanomaterials using the atomic finite element method. The Tersoff-Brenner potential is used to describe the interaction between silicon atoms, and the atomic finite element method is constructed in a computational scheme similar to the continuum finite element method. Young’s modulus and Poisson ratio are calculated for [100], [110], and [111] silicon nanowires that are treated as three-dimensional structures. It is found that the nanowire possesses the lowest Young’s modulus along the [100] direction, while the [110] nanowire has the highest value with the same radius. The bending deformation of [100] silicon nanowire is also modeled, and the bending stiffness is calculated.
关键词： atomic finite element method,silicon nanowires,Poisson ratio,elastic property,bending stiffness,Young’s modulus
更新于2025-09-10 09:29:36