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X-ray Diffraction Analysis of the Angular Stability of Self-Catalyzed GaAs Nanowires for Future Applications in Solar Light Harvesting and Light Emission Devices
摘要： Semiconductor nanowires are a class of materials that recently have gained increasing interest in solar cell applications and light emitting devices. Finding reproducible processing conditions is fundamental for their future mass production. In this work, the stability of individual epitaxial GaAs nanowires (NWs) under molecular beam epitaxy (MBE) processing conditions is studied by means of a time-resolved in-situ micro X-ray diffraction (XRD) method and scanning electron microscopy. Our proposed micro XRD method is a non-destructive characterization technique where individual nano-objects of different dimensions, crystal orientations, and structures are detectable under MBE processing conditions. NWs were grown by self-catalyzed MBE onto pre-patterned Si(111) substrate. When exposed to MBE processing conditions at 610 °C without supply of source material, or with only arsenic supply, we observe evaporation from the facets with no indication of gallium droplet formation. Furthermore, the NWs, which are initially grown perpendicular to the substrate surface become angularly unstable i.e. the NWs tilt and eventually lie down on the substrate surface. Before falling down, our micro XRD data evidenced vibrations/bending of the NWs. Interestingly, when exposed to the original growth conditions which include gallium and arsenic supply, the vibrations/bending are suppressed and the tilting can be reversed. The findings in this paper can also provide insights towards engineering of self-catalyzed GaAs NW growth by removal of parasitic growth objects which inevitably grow together with NWs.
关键词： time-resolved,in-situ,mechanical stability,micro X-ray diffraction,nanowire,annealing,GaAs
更新于2025-09-23 15:23:52
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Potential Dependence of Mechanical Stability and Electronic Coupling of Single S-Au Bonds
摘要： Providing a mechanically stable and electronically efficient coupling between a molecule and an electrode is critical to the study of charge transfer and conductance of the molecule. A common method is to link the molecule to Au electrodes via a linker (e.g., thiol terminal of the molecule). Here we study the mechanical stability and electronic coupling of S-Au bond in single molecule junctions over a broad range of electrode potential. Our results show that the mechanical and electromechanical properties of molecule-electrode contact undergo a systematic change with the potential involving Au oxidation at positive potentials and S protonation at negative potentials. The study establishes the potential range for a stable S-Au bond and determines the potential dependence of the mechanical and electromechanical properties of the molecule-electrode contact, which is crucial to the interpretation of potential dependent charge transfer in electrochemistry and electrochemical gating of charge transport in molecular electronics.
关键词： molecule-electrode contact,electronic coupling,electrode potential,S-Au bond,mechanical stability
更新于2025-09-23 15:21:21
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Improving the performance of ultra-flexible perovskite photodetectors through cation engineering
摘要： High performance ultra-flexible lightweight perovskite photodetectors hold promising applications on arbitrary substrates include unmanned aerial vehicles. Herein, we report a facile method to improve the performances of perovskite photodetectors on flexible ultrathin (50 μm) polyimide substrates by tuning the composition with different ratios of cations. In the presence of lead thiocyanate, a certain amount of formamidinium introduction could sufficiently enhance the methylammonium lead triiodide perovskite film quality with prolonged carrier lifetime. Perovskite photodetector with response time of ton=89 ms and toff=47 ms is achieved with a very simple device architecture. In addition, our flexible photodetectors maintain good performances after rigorous folding and bending, demonstrating excellent mechanical properties, which can be very useful for a variety of applications.
关键词： compositional engineering,mechanical stability,ultra-flexible detectors,perovskite photodetectors
更新于2025-09-23 15:19:57
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Thermal design management of highly mechanically stable wavelength shifter using photonic crystal waveguide
摘要： A thermally tunable device based on photonic crystal waveguide integrated with the micro-hotplate on its surface is proposed. A design strategy for modelling of temperature and stress in the MHP is investigated for providing robustness and high mechanical stability in the reconfigurable device. The required temperature is obtained under stress elongation fatigue limit for thermal tuning applications in optical devices. The performance parameters like confinement factor, wavelength transfer coefficient and extinction ratio are obtained as 78.2%, 0.086 nm/K and 30.04 dB respectively with an excess loss of only 0.20 dB. The response-time in the optimized device is 12 μs for achieving the switching spectral shift of 26 nm in the transmission spectrum of PCW. The reconfigurable device platform offers a great potential for wide range of tuning in switches and filters applications
关键词： Thermally tunable device,Photonic crystal waveguide,Thermo-optic tuning,Mechanical stability,Micro-hotplate
更新于2025-09-23 15:19:57
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Fully Solution Processed, Stable, and Flexible Bifacial Polymer Solar Cells
摘要： Photon capturing is an essential step for the operation of a solar cell. In this article, we develop a bifacial solar cell with characteristics of double-side photon collection, transparent appearance, mechanical ?exibility, and facile processing. The whole device was fully fabricated by a spin-coating technique. A power conversion ef?ciency (PCE) as high as 2.46% has been achieved using the most prominent photoactive material, poly(3-hexylthiophene):(6, 6)-phenyl C61 butyric acid methyl ester (P3HT:PCBM). The bifacial solar cell can retain 92% of its original PCE after 350 cyclic bending cycles at bending radii of 7.4 mm. In addition to the mechanical instability of the device, photochemical degradation is partially involved in the device operation. We believe that our device with its promising mechanical, physical, and processing features can serve as an essential power element to be integrated with other technologies for the next-generation self-powered technology.
关键词： polymer solar cell (PSCs),Bifacial solar cell,?exibility,mechanical stability,transparent device
更新于2025-09-16 10:30:52
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Efficient and Mechanically Robust Ultraflexible Organic Solar Cells Based on Mixed Acceptors
摘要： A simple strategy to simultaneously improve power conversion efficiency (PCE) and mechanical stability of ultra?exible organic solar cells is reported. By using a fullerene/non-fullerene mixed acceptor, 3-mm-thick ultra?exible organic solar cells achieve a PCE of 13% (a certi?ed value of 12.3%) with 97% PCE retention after 1,000 bending cycles and 89% PCE retention after 1,000 compression-stretching cycles.
关键词： mixed acceptors,fullerene,mechanical stability,non-fullerene,ultra?exible organic solar cells,power conversion efficiency
更新于2025-09-12 10:27:22
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Effect of Composition and Microstructure on the Mechanical Stability of Perovskite Solar Cells
摘要： We report on recent studies characterizing the intrinsic mechanical integrity of perovskite compositions and fully explore the role of various cation combinations, additives, and microstructure on perovskite cohesion. Adding cations to the perovskite decreased mechanical integrity, largely due to smaller grain sizes and increased concentration of PbI2. Microindentation hardness testing was performed to estimate the fracture toughness of single-crystal perovskite, and the results indicated perovskites are inherently fragile, even in the absence of grain boundaries and defects. Introducing plastically deformable cations led to a modest improvement in cohesion, and the most robust architecture was observed by infusing perovskite into a porous TiO2/ZrO2/C layer that provided extrinsic reinforcement to mechanical and environmental stressors.
关键词： fracture,perovskite solar cell,mechanical stability,reliability,module
更新于2025-09-11 14:15:04
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Forming Spacers in Situ by Photolithography to Mechanically Stabilize Electrofluidic-Based Switchable Optical Elements
摘要： Electro-Fluidic Displays (EFD) have been demonstrated to be an attractive technology for incorporation into portable display devices. EFDs have excellent optical ef?ciency and fast switching enabling video content. Ensuring mechanical stability of EFD display cells is a key challenge and essential for developing large area as well as ?exible displays. Although the electro-optic performance of an EFD, unlike a liquid crystal display (LCD), is insensitive to cell-gap, extreme changes in cell-gap can result in irreversible collapse of the cell. Here we use photolithography to develop spacers to prevent cell-gap collapse and provide the required mechanical stability for EFD devices. The spacer is formed directly on the cover plates (ITO/glass) after cell assembly with UV light induced phase separation polymerization in the illuminated area. Phase separation behavior between polar aqueous solution and polymer is closely related to the solubility of acrylate monomers. In this work, polyethylene glycol diacrylate (PEGDA) as cross-linker, 2-hydroxyethyl acrylate (HEA) and acrylic acid or acrylamide as co-monomers are investigated for fabricating the spacers. PEGDA was added to the mixtures in order to increase the mechanical strength of the spacer. The spacers showed excellent performance for cell-gap control in EFD devices.
关键词： mechanical stability,electro?uidic display,phase separation,photopolymerization,electrowetting,spacer
更新于2025-09-10 09:29:36
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Photo- and electro-responsive phase change materials based on highly anisotropic microcrystalline cellulose/graphene nanoplatelet structure
摘要： Phase change materials (PCMs) exhibit great potential applications in many fields, such as energy-saving building, solar energy harvesting, waste heat utilization, constant temperature protection and thermal management of microelectronic devices. In this work, we proposed a facile and novel method to prepare the composite PCMs. Through the combination of pre-refrigeration and freeze-drying techniques using the microcrystalline cellulose (MCC)/graphene nanoplatelets (GNPs) hydrogels, which were firstly prepared through solution compounding, gelling and solvent exchanging successively, the porous MCC/GNP aerogels with highly oriented stacking of MCC/GNP were successfully obtained. The composite PCMs based on the highly anisotropic MCC/GNP aerogel and polyethylene glycol (PEG) exhibited relatively high thermal conductivity (1.03 W/mK) at low GNP content (1.51 wt%), high latent heat (182.6 J/g) which was 99.84% of pure PEG, excellent encapsulation ability and mechanical stability. Further results showed that the composite PCMs exhibited excellent solar energy harvesting/electrical energy transformation, storage and release abilities. In addition, a simple heating device was designed to verify the application of the composite PCMs as the temperature protection element. The measurements showed that the presence of the PCMs prevented the rapidly rising of temperature during the heating process while maintained the temperature at relatively high level in a long time during the cooling process.
关键词： Phase change materials,Mechanical stability,Anisotropic structure,Solar energy/electrical energy comprehensive utilization
更新于2025-09-09 09:28:46