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Microstructure characteristics of non-monodisperse quantum dots: On the potential of transmission electron microscopy combined with X-ray diffraction
摘要： Although the concept of quantum confinement was introduced more than thirty years ago, a wide application of the quantum dots is still limited by the fact that monodisperse quantum dots with controlled optoelectronic properties are typically synthesized on a relatively small scale. Larger scale synthesis techniques are usually not able to produce monodisperse nanoparticles yet. In this contribution, we illustrate the capability of the combination of transmission electron microscopy and X-ray diffraction to reveal detailed and scale-bridging information about the complex microstructure of non-monodisperse quantum dots, which is the first step towards a further upscalling of the techniques for production of quantum dots with controlled properties. As a model system, CdSe quantum dots synthesized using an automated robotic hot-injection method at different temperatures were chosen. The combined microstructure analytics revealed the size and shape of the CdSe nanocrystals and the kind, density and arrangement of planar defects. The role of the planar defects in the particle coarsening by oriented attachment and the effect of the planar fault arrangement on the phase constitution, on the crystallographic coherence of the counterparts and on the optoelectronic properties are discussed.
关键词： microstructure,optoelectronic properties,planar defects,transmission electron microscopy,X-ray diffraction,quantum dots,oriented attachment,CdSe
更新于2025-09-23 15:21:01
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Carbon Nanotubes - Recent Progress || Stability and Reliability of an Electrical Device Employing Highly Crystalline Single-Walled Carbon Nanotubes as a Field Emitter
摘要： Carbon nanomaterial is drawing keen interest from researchers as well as materials scientists. Carbon nanotubes (CNTs)—and their nanoscale needle shape—offering chemical stability, thermal conductivity, and mechanical strength exhibit unique properties as a quasi-one-dimensional material. Among the expected applications, field emission electron sources appear the most promising industrially and are approaching practical utilization. However, efforts to construct a field emission (FE) cathode with single-walled carbon nanotubes (SWCNTs) have so far only helped average out a non-homogeneous electron emitter plane with large FE current fluctuations and a short emission life-time because they failed to realize a stable emission current owing to crystal defects of the carbon network in CNTs. The utilization of CNTs to obtain an effective cathode, one with a stable emission and low FE current fluctuation, relies on the ability to disperse CNTs uniformly in liquid media. In particular, highly crystalline SWCNTs hold promise to obtain good stability and reliability. The author successfully manufactured highly crystalline SWCNTs-based FE lighting elements that exhibit stable electron emission, a long emission life-time, and low power consumption for electron emitters. This FE device employing highly crystalline SWCNTs has the potential for conserving energy through low power consumption in our habitats.
关键词： wet coating process,high crystallization,field emission,single-walled carbon nanotube,scratch,thin film,planar light source,cathode luminescence
更新于2025-09-23 15:21:01
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Suppression of radiation loss in high kinetic inductance superconducting co-planar waveguides
摘要： We present a lab-on-chip technique to measure the very low losses in superconducting transmission lines at (sub-) mm wavelengths. The chips consist of a 100 nm-thick NbTiN Co-planar Waveguide (CPW) Fabry–P(cid:2)erot (FP) resonator, coupled, on one side, to an antenna and, on the other side, to a Microwave Kinetic Inductance detector. Using a single frequency radiation source allows us to measure the frequency response of the FP around 350 GHz and deduce its losses. We show that the loss is dominated by radiation loss inside the CPW line that forms the FP and that it decreases with the decreasing linewidth and increasing kinetic inductance as expected. The results can be quantitatively understood using SONNET simulations. The lowest loss is observed for a CPW with a total width of 6 lm and corresponds to a Q-factor of (cid:2)15 000.
关键词： radiation loss,Fabry–P(cid:2)erot resonator,co-planar waveguides,superconducting transmission lines,kinetic inductance
更新于2025-09-23 15:21:01
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Dopant-free hole transporting materials with supramolecular interactions and reverse diffusion for efficient and modular p-i-n perovskite solar cells
摘要： The rational design of dopant-free organic hole-transporting layer (HTL) materials is still a challenge for realizing high-efficient and stable p-i-n planar perovskite solar cells (pero-SCs). Here, we synthesized two π-conjugated small-molecule HTL materials through tailoring the backbone and conjugated side chain to carefully control molecular conformation. The resultant BDT-TPA-sTh containing a planar fused benzo[1,2-b:4,5-b′]dithiophene (BDT) core and a conjugated thiophene side chain showed the planar conformation. X-ray crystallography showed a favorable stacking model in solid states under the parallel-displaced π-π and additional S-π weak-bond supramolecular interactions, thus achieving an obviously increased hole mobility without dopants. As an HTL material in p-i-n planar pero-SCs, the marginal solubility of BDT-TPA-sTh enabled inverse diffusion into the perovskite precursor solution for assisting the subsequent perovskite film growth and passivating the uncoordinated Pb2+ ion defects. As a result, the planar p-i-n pero-SCs exhibited a champion power conversion efficiency (PCE) of 20.5% and enhanced moisture stability. Importantly, the BDT-TPA-sTh HTL material also showed weak thickness-photovoltaic dependence, and the pero-SCs with blade-coated BDT-TPA-sTh as a HTL achieved a 15.30% PCE for the 1-cm2 modularized device. This HTL material design strategy is expected to pave the way toward high-performance, dopant-free and printing large-area planar p-i-n pero-SCs.
关键词： hole-transporting materials,p-i-n planar perovskite solar cells,reverse diffusion,supramolecular interactions
更新于2025-09-23 15:21:01
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Propagation of Electromagnetic Waves in an Open Planar Dielectric Waveguide Filled with a Nonlinear Medium II: TM Waves
摘要： A nonlinear eigenvalue problem on an interval is considered. The nonlinearity in the equation is specified by a nonnegative monotonically increasing function, and the boundary conditions nonlinearly depend both on the sought-for functions and on the spectral parameter. The discrete eigenvalues are defined using an additional (local) condition at one end of the interval. This problem describes the propagation of monochromatic (polarized) electromagnetic TM waves in a planar dielectric waveguide filled with a nonlinear medium. The nonlinearity covers a wide range of laws of nonlinear optics corresponding to self-interaction effects. Results on the solvability of the problem and the properties of the eigenvalues are obtained.
关键词： Maxwell’s equations,nonlinear eigenvalue problem,nonlinear permittivity,nonlinear Sturm–Liouville problem,planar dielectric waveguide,asymptotics of eigenvalues,comparison theorem
更新于2025-09-23 15:21:01
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Edge mode graphene plasmons based all-optical logic gates
摘要： Graphene plasmonic logic gates (GPLGs) with high compaction and simple structure are presented and investigated in this paper. Due to the strong confinement of edge mode graphene surface plasmon polaritons (EGSPPs), it can process optical signal on nanoscale ribbons with both straight and flexible shapes. Three eigen modes of graphene surface plasmon polaritons (GSPPs) are studied from the aspect of their propagation properties, indicating that the symmetric edge-mode (SEM) is an optimal choice for designing the GPLGs. Finally, some basic logic gates, i.e., the XOR and XNOR gates, are demonstrated by employing the SEM. More kind of GPLGs and functional devices are expected to be realized by cascading these basic logic gates.
关键词： Logic-based optical processing,Surface plasmons,All-optical devices,Planar,Waveguides
更新于2025-09-23 15:21:01
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Effects of solvent additives on the morphology and transport property of a perylene diimide dimer film in perovskite solar cells for improved performance
摘要： Perylene diimide derivatives (PDIs) are a kind of very promising non-fullerene electron transport material for organic-inorganic perovskite solar cells (PerSCs), owing to their excellent photoelectric properties and low-cost synthesis. However, their tendency to form aggregates strongly influences the film morphology and transport properties. Herein, we provided a simple way to tune the morphology and transport properties of PDIs by solvent additive engineering. A series of solvent additives (1,8-diiodooctane, 1-chloronaphthalene, 1-phenylnaphthalene, 1-methylnaphthalene) was investigated for their role in the morphology and transport property of PDI dimer (Bis-PDI-T-EG) film as well as on the photovoltaic performance of PerSCs. Among these four solvent additives, 1-methylnaphthalene (MN) was found one of the best additive that possesses good adjusting ability to control both morphological and electrical properties of Bis-PDI-T-EG film. The fabricated PerSCs with optimized Bis-PDI-T-EG + 0.05 v/v% MN electron transport layer (ETL) displayed the best power conversion efficiency (PCE) of 14.96%. The performance of PerSCs was further improved by adding 0.05 wt% graphene together with 0.05 v/v% MN, and the maximum PCE of 15.11% was achieved.
关键词： Solvent additives,Graphene,p-i-n,Planar perovskite,Perylene diimide,Solar cells
更新于2025-09-23 15:21:01
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Feasibility Analysis of Nanostructured Planar Focusing Collectors for Concentrating Solar Power Applications
摘要： Concentrating solar power (CSP) technology is an attractive approach to harvesting solar energy. Unlike photovoltaic (PV) technology, thermal storage is used in lieu of batteries for electricity generation. However, the cost of current collection optics in a CSP plant hampers commercial competitiveness with PVs and natural gas. The use of a planar focusing collector (PFC) could help reduce cost of materials, installation, and maintenance. We present two candidate PFC designs, one based on metasurfaces and the other a Fresnel-like model. We feed each design through the entire system process—design, fabrication, scalability, and techno-economic feasibility—and discuss the challenges met at each stage. Two-photon and nanoimprint lithography are used to make PFC molds and replicas, respectively. We find that the annual optical efficiency for the Fresnel-based PFC is ~40%--higher than the current 30% target for natural gas, thereby suggesting potential economic advantages in the market of industrial process heat.
关键词： Metasurface,Two-Photon Lithography,Concentrating Solar Power (CSP),Planar Focusing Collector (PFC),Nanoimprint Lithography
更新于2025-09-23 15:21:01
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Planar Chiral [2.2]Paracyclophanes: Optical Resolution and Transformation to Optically Active π-Stacked Molecules
摘要： In this article, recent our results on practical optical resolution methods of disubstituted and tetrasubstituted [2.2]paracyclophane compounds and their transformations are described. The obtained enantiopure [2.2]paracyclophane compounds have been used as chiral building blocks to prepare optically active π-stacked molecules. π-Stacked molecules construct optically active second-ordered structures, such as V-, N-, M-, X-, triangle-shaped, and one-handed double helical structures, due to the orientation of stacked π-electron systems. They emit circularly polarized luminescence (CPL) by photo-excitation. [2.2]Paracyclophane-based chiral π-stacked molecules in this article emit brightly owing to good photoluminescence (PL) quantum efficiencies as well as large molar extinction coefficients. In particular, emission is of course CPL with the large disymmetry factor (glum value). It is basically difficult to achieve CPL with high brightness, high PL efficiency, and large glum value by using other chiral scaffolds; therefore, planar chiral [2.2]paracyclophane is the ideal scaffold to be an excellent CPL emitters.
关键词： [2.2]Paracyclophane,Planar chirality,Circularly polarized luminescence
更新于2025-09-23 15:21:01
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[IEEE 2017 5th RSI International Conference on Robotics and Mechatronics (ICRoM) - Tehran, Iran (2017.10.25-2017.10.27)] 2017 5th RSI International Conference on Robotics and Mechatronics (ICRoM) - Robustness Enhancement of optical flow sensors accuracy to surface texture variations using point tracking algorithm
摘要： Novel architecture of high precision localization using optical flow sensor (OFS) combined with Iterative Point Tracking Algorithm (IPTA) is proposed. This work focuses on attenuation of OFS' sensitivity dependency on texture of surface over which sensor is moving. The aim for the design of experimental setup is to verify how much a robustness of OFS’s sensitivity on various surfaces improves. In this regard, four different surfaces' texture including iron, paper, textile and granite stone is opted. Experimental results indicate that sensor's resolution via IPTA on surfaces of iron, paper, textile and granite stone respectively equal to 382, 460, 528 and 448 CPI. Optimal value of the algorithm parameters is calculated via Genetic Algorithm (GA). We show that IPTA is one of the effective algorithms that can enhance the robustness of OFS' resolution to surface's texture variations.
关键词： Optical flow sensor,point tracking algorithm,Surface Texture,high accuracy planar localization,Genetic algorithm
更新于2025-09-23 15:21:01