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Morphology Phase Diagram of Slot‐Die Printed TiO <sub/>2</sub> Films Based on Sol–Gel Synthesis
摘要： Mesoporous titania films with tailored nanostructures are fabricated via slot-die printing, which is a simple and cost-effective thin-film deposition technique with the possibility of a large-scale manufacturing. Based on this technique, which is favorable in industry, TiO2 films possess the similar advantage with polymer semiconducting devices like ease of large-scale production. The titania morphologies, including foam-like nanostructures, nanowire aggregates, collapsed vesicles and nanogranules, are achieved via a so-called block-copolymer-assisted sol–gel synthesis. By adjusting the weight fraction of reactants, the ternary morphology phase diagram of the printed titania films is probed after template removal. The surface and inner morphology evolutions are explored with scanning electron microscopy and grazing incidence small-angle X-ray scattering, respectively. Special focus is set on foam-like titania nanostructures as they are of especial interest for, e.g., solar cell applications. At a low weight fraction of the titania precursor titanium(IV)isopropoxide (TTIP), foam-like titania films are achieved, which exhibit a high uniformity and possess large pore sizes. The anatase phase of the highly crystalline titania films is verified with X-ray diffraction and transmission electron microscopy.
关键词： TiO2 films,crystallinity,morphology phase diagram,printing,GISAXS
更新于2025-11-21 11:20:42
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from magnetospectroscopy
摘要： Pb1-xSnxSe hosts three-dimensional (3D) massive Dirac fermions across the entire composition range for which the crystal structure is cubic. In this paper, we present a comprehensive experimental mapping of the 3D band structure parameters of Pb1-xSnxSe as a function of composition and temperature. We cover a parameter space spanning the band inversion that yields its topological crystalline insulator phase. A nonclosure of the energy gap is evidenced in the vicinity of this phase transition. Using magneto-optical Landau level spectroscopy, we determine the energy gap, Dirac velocity, anisotropy factor, and topological character of Pb1-xSnxSe epilayers grown by molecular beam epitaxy on BaF2 (111). Our results are evidence that Pb1-xSnxSe is a model system to study topological phases and the nature of the phase transition.
关键词： Dirac parameters,Pb1-xSnxSe,topological phase diagram,magnetospectroscopy
更新于2025-09-23 15:23:52
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Binary Colloidal Nanoparticle Concentration Gradients in a Centrifugal Field at High Concentration
摘要： Binary colloidal nanoparticles have been found to form different types of crystalline phases at varied radial positions in a centrifugal field by Chen et al (ACS nano 2015, 9, 6944-50.). The variety of binary phase behaviors resulted from the two different nanoparticle concentration gradients but to date the gradients can only be empirically controlled. For the first time, we are able to measure, fit and simulate binary hard sphere colloidal nanoparticle concentration gradients at high particle concentration up to 30 vol%, which enables tailor-made gradients in a centrifugal field. By this means, a continuous range of binary particle concentration ratios can be accessed in one single experiment to obtain an extended phase diagram. By dispersing two differently sized silica nanoparticles labeled with two different fluorescence dyes in a refractive index matching solvent, we can use a Multi-Wavelength Analytical Ultracentrifuge (MWL-AUC) to measure the individual concentration gradient for each particle size in sedimentation-diffusion equilibrium. The influence of the remaining slight turbidity at high concentration can be corrected using the MWL spectra from the AUC data. We also show that the experimental concentration gradients can be fitted using a non-interacting non-ideal sedimentation model. By using these fitted parameters, we are able to simulate nanoparticle concentration gradients, which agreed with the subsequent experiments at a high concentration of 10 vol% and thus allowed for the simulation of binary concentration gradients of hard sphere nanoparticles in preparative ultracentrifuges (PUC). Finally we demonstrated that by simulating the concentration gradients in PUC, a continuous and extended binary nanoparticle phase diagram can be obtained by simply studying the structure evolution along the centrifugal field for one single sample instead of a large number of experiments with discrete compositions in conventional studies.
关键词： high particle concentration,binary nanoparticle phase diagram.,Binary nanoparticle concentration gradients,sedimentation-diffusion equilibrium
更新于2025-09-23 15:22:29
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High piezoelectricity of BiScO3-PbTiO3 ceramics prepared by two step sintering
摘要： (1-x)BiScO3-xPbTiO3 (BSPT) ferroelectric ceramics were prepared by two-step sintering. Dielectric measurements in combination with diffraction contrast transmission electron microscopy (TEM) were used to confirm the phase diagram of BSPT system. From these results, the low temperature phase diagram for BSPT was achieved. In present study, high piezoelectric properties with piezoelectric coefficients (d33≈545pC/N, d33*≈920pm/V) and planar electromechanical coupling factor (kp ≈57%) are achieved in the ceramcs at the composition x=0.64, indicating a future high-temperature piezoelectric application.
关键词： Dielectrics,Phase diagram,Two step sintering,Ceramics
更新于2025-09-23 15:22:29
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Towards silicon-based metamaterials
摘要： We study periodic lattices of silicon nanorods and introduce the concept of a phase diagram that characterizes a transition between the regimes of photonic crystals and dielectric metamaterials when the lattice spacing and operational wavelength vary. We find the conditions when a hexagonal periodic lattice of silicon nanorods can operate as a metamaterial described by averaged parameters. In general, we reveal that the metamaterial regime can be achieved for dielectric permittivity exceeding the value ε = 14, being commonly available for semiconductors in both visible and near-infrared frequency ranges. Thus, advanced semiconductor technologies can offer a versatile platform for novel designs of all-dielectric Mie-resonant metadevices.
关键词： phase diagram,photonic crystals,dielectric metamaterials,Mie resonances,silicon nanorods
更新于2025-09-23 15:21:21
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Bond versus charge disproportionation in the bismuth perovskites
摘要： We develop a theory describing a parameter-based phase diagram to be associated with materials incorporating skipped-valence ions [Phys. Rev. Lett. 61, 2713 (1988)]. We use a recently developed tight-binding approach for the bismuthates to study the phase diagram exhibiting a crossover from a bond disproportionated (BD) to a charge disproportionated (CD) system in addition to the presence of a new metallic phase. We argue that three parameters determine the underlying physics of the BD-CD crossover when electron correlation effects are small: the hybridization between O-2pσ and Bi-6s orbitals (tspσ ), the charge-transfer energy between Bi-6s and O-a1g molecular orbitals ((cid:2)), and the width of the oxygen sublattice band (W ). In the BD system, we estimate the effective attractive interaction U between the two holes on the same hybrid A1g orbital composed of a linear combination of O-a1g and Bi-6s orbitals. Although we concentrate here on the example of the bismuthates, the basic ideas can be directly transferred to other perovskites with negative charge-transfer energy, like ReNiO3 (Re: rare-earth element), Ca(Sr)FeO3, CsTIF3, and CsTlCl3.
关键词： phase diagram,bismuth perovskites,tight-binding model,bond disproportionation,charge disproportionation
更新于2025-09-23 15:21:21
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Thermodynamic stability, half-metallic and optical nature of graphene-like Mn <sub/>2</sub> Zr <i>Z</i> ( <i>Z</i> = Ge, Si): <i>Ab initio</i> study
摘要： Half-metallic, optical and thermodynamic phase diagrams of two-dimensional Mn2ZrZ (Z = Ge, Si) have been calculated by density functional theory (DFT) framework with full-potential linear augmented plane-wave (FP-LAPW) method. The spin-polarized electronic computations show that these layers have metallic behavior with a spin polarization less than 100%. It is observed that with increasing thickness of the layers, both the thermodynamic and energy stabilities increased, and the graphene-like layers of Mn2ZrGe with a thickness of 7.6955 ?A and Mn2ZrSi with a thickness of 7.551 ?A are completely stable thermodynamically. The optical responses of Mn2ZrZ (Z = Ge, Si) have anisotropy at infrared region versus the optical direction and have high metallic nature in this optical range. The plasmonic frequencies have occurred after the visible edge and the refraction index becomes lower than one after the ultra-violet edge.
关键词： optical property,half-metal,thermodynamic phase diagram,DFT,Graphene-like Mn2ZrZ (Z = Ge, Si)
更新于2025-09-23 15:21:21
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Significance of Dopant/Component Miscibility to Efficient N-Doping in Polymer Solar Cells
摘要： The uncertain dopant location in the bulk heterojunction (BHJ) film hinders the wide application of molecular doping in polymer solar cells (PSCs) as is in other organic devices. It is known that the interaction between dopant and component governs the dopant distribution in the BHJ film, and thus largely controls the effectiveness of molecular doping. After excluding the strong dopant/component interaction by forming the charge-transfer complex in solution, we estimate the dopant/component miscibility by calculating the difference of Hansen’s total solubility parameters (δi-Hansen) and prove its correctness by contact angle measurements, and two model systems of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophe-2-yl)-benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1’,3’-di-2-thienyl -5’,7’-bis(2-ethylhexyl)benzo[1’,2’-c:4’,5’-c’]dithiophene-4,8-dione))] (PBDB)/poly{[N,N’-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5’-(2,2’-bithiophene)} (N2200) and poly[4,8-bis(5-(2-ethylhexyl)-thiophene-2-yl)benzo[1,2-b;4,5-b’]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]] (PCE10)/N2200 are selected to reveal the miscibility-photovoltaic performance relations. Only the material combination with large δi-Hansen between n-dopant (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl) phenyl) dimethylamine (N-DMBI) and the donor polymer achieves enhanced photovoltaic performance. After that, we examine the doped morphology of polymer blends. Since the polymers’ crystallizations are negatively affected by N-DMBI addition, we ensure the significance of n-doping on the enhanced device performance. Besides the dopant/polymer interaction, the solvent/polymer and solvent/dopant interactions are also considered to evaluate the kinetic effect on N-DMBI distribution by drawing the ternary phase diagram. We conclude that the kinetic morphological evolution doesn’t change the miscibility governed N-DMBI distribution in the BHJ film. Finally, we provide a direct relationship between the N-DMBI position and the device property by fabricating the bi-layer devices. The enhancement of photovoltaic performances is observed in both of material systems only if the N-DMBI distributes in N2200. Our work outlines a basis for using the dopant/component interaction and ternary phase diagram to predict the dopant distribution before extensive experiments. It significantly reduces the trial-to-error work and increases the reliability of molecularly doped PSCs.
关键词： n-doping,polymer solar cell,doped morphology,ternary phase diagram,Molecular doping
更新于2025-09-23 15:19:57
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Improved optoelectronic properties in CdSexTe1?x through controlled composition and short-range order
摘要： We employ ?rst principles methods based on density functional theory and beyond to study CdSexTe1?x alloys in the zincblende and wurtzite structures. From the cluster expansion formalism, we provide a detailed phase diagram showing a consolute temperature of 325 K, above which miscibility may be achieved. In the random solid solution, a zincblende-to-wurtzite phase boundary is found to range from Se concentrations of x = 0.5–0.6, in agreement with experiment, owing to increasing ionic character of the Cd-anion bonds. Disordered CdSexTe1?x con?gurations are modeled using special quasirandom structures, for which optoelectronic properties are computed with the hybrid HSE06 functional. Alloying is shown to cause strong bowing e?ects in the band gap and e?ective electron/hole masses, which we attribute to local structural distortions as illustrated by analysis of bond length distributions. Downward bowing in the band gap and e?ective hole mass of the zincblende structure is highlighted for its potential bene?ts in photovoltaics through increased net photocurrent. Absorption coe?cients and re?ectivity are also reported, showing promising results in zincblende CdSexTe1?x as indicated by substantial optical absorption throughout all Se concentrations. Lastly, we identify the presence of short-range order in CdSexTe1?x characterized by clustering among like atoms in order to minimize strain. The degree of clustering, which may be tuned by temperature, also controls the magnitude of the band gap. Therefore, we propose both composition and short-range order as e?ective tools to be utilized in the design and synthesis of improved solar cell absorber layer materials.
关键词： Phase diagram,Optical properties,Bandgap-bowing,Short range order,CdSexTe1?x alloys
更新于2025-09-16 10:30:52
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Phase diagram of colloidal crystals of poly(methyl methacrylate) spheres in the exhaustively deionized dispersion
摘要： Phase diagram of colloidal crystals of poly(methyl methacrylate) (PMMA) spheres (100 to 300 nm in diameter) was measured precisely for the exhaustively deionized aqueous dispersion. Strong iridescent colors changed from bluish to reddish and metallic as sphere size increased at high sphere concentrations around 0.1 in volume fraction. Large single crystals, on the other hand, were recognized with the naked eyes at low sphere concentrations around 0.0005 to 0.001 especially for PMMA spheres smaller than 200 nm. The critical concentrations of melting (or crystallization), ?c of all the PMMA spheres examined were quite low between 0.00025 and 0.00060 in volume fraction. The ?c values were insensitive to kind (polystyrene, silica, and fluorine-containing spheres) and also to size (90~300 nm) of colloidal spheres. The ?c value of the deionized dispersion with the coexistence of the ion-exchange resins was lowest, and that without resins was tenfold large. Addition of sodium chloride increased the ?c values sharply. Extension of the electrical double layers forming around the colloidal spheres is most important to determine the ?c values.
关键词： Critical concentration of melting,Phase diagram,Colloidal crystal,Deionized dispersion,Poly(methyl methacrylate) spheres
更新于2025-09-10 09:29:36