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Interfacial Tensions and Viscosities in Multiphase Systems by Surface Light Scattering (SLS)
摘要： Hypothesis Multiphase systems are relevant in many fields of process engineering. For process and product design in connection with multiphase systems, knowledge on the thermophysical properties of the individual phases such as viscosity and on the interfacial tension between these is required but often lacking in literature. Experiments In the present study, the applicability of surface light scattering (SLS) for the simultaneous measurement of interfacial tensions and viscosities in multiphase systems in macroscopic thermodynamic equilibrium is demonstrated. For two model systems consisting of n-decane and methanol as well as n-dodecane and methanol forming a vapor-liquid-liquid equilibrium at atmospheric pressure, surface fluctuations which show an oscillatory behavior at the vapor-liquid and liquid-liquid interface could be associated with hydrodynamic modes. Findings From an exact theoretical description of the dynamics of the surface fluctuations, absolute data for the dynamic viscosities of the two liquid phases as well as the vapor-liquid and liquid-liquid interfacial tensions could be determined at temperatures between (333 and 358) K with total measurement uncertainties (k = 2) down to about 2%. For both systems studied at temperatures close to the upper critical solution temperature, the viscosities of the two liquid phases approach each other and the liquid-liquid interfacial tension tends to zero.
关键词： liquid-liquid systems,interfacial tension,multiphase systems,interfaces,upper critical solution temperature,vapor-liquid systems,viscosity,surface light scattering
更新于2025-09-23 15:21:21
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Formation of Occupied and Unoccupied Hybrid Bands at Interfaces between Metals and Organic Donors/Acceptors
摘要： Efficient charge transport in organic semiconductors and at their interfaces with electrodes is crucial for the performance of organic molecule-based electronic devices. Band formation fosters effective transport properties and can be found in organic single crystals of large π-stacking aromatic molecules. However, at molecule/metal interfaces hybrid band formation and band dispersion is a rarely observed phenomenon. Using angle-resolved two-photon photoemission supported by density functional theory calculations we demonstrate such band formation for two different molecule/metal systems, namely tetrathiafulvalene (TTF)/Au(111) and tetrafluoro-tetracyanoquinodimethane (F4TCNQ)/Au(111), in the energy region of occupied as well as unoccupied electronic states. In both cases strong adsorbate/substrate interactions result in formation of interface states due to hybridization between localized molecular states and delocalized metal bands. These interface states exhibit significant dispersions. Our study reveals that hybridization in combination with an extended well-ordered adsorption structure of the π-conjugated organic molecules is a striking concept to receive and experimentally observe band formation at molecule/metal interfaces.
关键词： band formation,organic semiconductors,molecule/metal interfaces,hybridization,charge transport,density functional theory,angle-resolved two-photon photoemission
更新于2025-09-23 15:21:21
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Surface-nanostructured single silver nanowire: a new one-dimensional microscale SERS interface
摘要： One-dimensional microscale SERS-active interfaces have been intriguing as a newly emerging class of SERS interfaces compared to conventional macroscale SERS substrates. In this work, a stable surface-nanostructured single silver nanowire was fabricated. The nanostructures on the nanowire are formed by nanoscale silver crystal dots with diameters of 20-50 nm. The SERS signals of the crystal violet probe molecules adsorbed on the nanostructures are dramatically enhanced by both electromagnetic and chemical effects. The hot spots generated at the junctions of adjacent nanoscale dots yield highly efficient surface plasmon resonance. Simultaneously, the charge transfer on the atomic-scale silver cluster located at the nanostructured interface causes an enhancement similar to a Raman resonance. The intensity distributions of the SERS peaks on the surface-nanostructured single nanowire are characterized by SERS mapping. It is found that, although the intensities of the SERS peaks are different, their SERS mapping images show uniform SERS enhancement distributions, whereas the noticeable SERS intensity distributions on the single smooth silver nanowire are mainly located on the two ends of the nanowire. The large number of nanoscale crystal dots along with the atomic-scale silver clusters are uniformly and densely distributed on the surface of the single roughened nanowire; these structural attributes induce a uniform and large surface plasmon resonance and charge transfer enhancements on the entire surface of the nanowire. This work indicates that the surface-nanostructured single silver nanowire, synthesized using a quite simple preparation method, performs as an excellent one-dimensional microscale SERS substrate with uniform and high enhancement characteristics, which shows high potential for applications as a new class of SERS-active substrates. Furthermore, the higher enhancement factor of the microscale SERS interfaces can be achieved by introducing other roughened nanowires to assemble a dimer and a trimer as micro SERS substrates, which is consistent with the dark field (DF) measurements.
关键词： Hot spots,Raman,Micro SERS interfaces,Charge transfer,Silver nanowire
更新于2025-09-23 15:21:21
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Photovoltaic organic interface for neuronal stimulation in the near-infrared
摘要： Organic materials, such as conjugated polymers, are attractive building blocks for bioelectronic interfaces. In particular, organic semiconductors show excellent performance in light-mediated excitation and silencing of neuronal cells and tissues. However, the main challenges of these organic photovoltaic interfaces compared to inorganic prostheses are the limited adhesion of conjugated polymers in aqueous environments and the exploitation of materials responsive in the visible spectrum. Here, we show a photovoltaic organic interface optimized for neuronal stimulation in the near-infrared spectrum. We adjusted the organic materials by chemical modification in order to improve the adhesion in an aqueous environment and to modulate the photoelectrical stimulation efficiency. As proof-of-principle, we tested this interface on explanted degenerated mice retinas, thus providing results on the efficiency and reliability of the device as an implant for neural stimulation.
关键词： organic semiconductors,bioelectronic interfaces,neuronal stimulation,near-infrared spectrum,photovoltaic interfaces
更新于2025-09-23 15:21:01
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New Impressions in Interaction Design: A Task Taxonomy for Elastic Displays
摘要： Novel shape-changing interfaces promise to provide a rich haptic experience for human-computer interaction. As a specific instance of shape-changing interfaces, Elastic Displays provide large interaction surfaces that can be temporally deformed using force-touch. The unique property of these displays is that they automatically return to their initial flat state. Recently, several review and position papers have stimulated a discussion towards consolidating the knowledge about shape-changing interfaces. The knowledge about Elastic Displays is similarly scattered across multiple publications from recent years. This paper contributes a task taxonomy based on productive uses of Elastic Displays found in literature, on the web, and in our interaction lab. This taxonomy emphasizes tasks, but also encompasses general aspects regarding content types, visualization technology, and interaction styles. All aspects of the taxonomy are illustrated using case studies from literature.
关键词： Task Taxonomy,Organic User Interfaces,Human-computer Interaction,Physics-based Interaction,Shape-changing Interfaces,Interaction Design,Tangible Interaction,Elastic Displays
更新于2025-09-23 15:21:01
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Hidden Isolated OH at the Charged Hydrophobic Interface Revealed by Two-Dimensional Heterodyne-Detected VSFG Spectroscopy
摘要： Water around hydrophobic groups mediates hydrophobic interactions that play key roles in many chemical and biological processes. Thus, the molecular-level elucidation of the properties of water in the vicinity of hydrophobic groups is important. We report on the structure and dynamics of water at two oppositely charged hydrophobic ion/water interfaces, the tetraphenylborate-ion (TPB?)/water and tetraphenylarsonium-ion (TPA+)/water interfaces, which are clarified by two-dimensional heterodyne-detected vibrational sum-frequency generation (2D HD-VSFG) spectroscopy. The obtained 2D HD-VSFG spectra of the anionic TPB? interface reveal the existence of distinct π-hydrogen bonded OH groups in addition to the usual hydrogen-bonded OH groups, which are hidden in the steady-state spectrum. In contrast, 2D HD-VSFG spectra of the cationic TPA+ interface only show the presence of usual hydrogen-bonded OH groups. The present study demonstrates that the sign of the interfacial charge governs the structure and dynamics of water molecules that face the hydrophobic region.
关键词： hydrophobic interfaces,sum-frequency generation,ultrafast spectroscopy,interfacial water,vibrational dynamics
更新于2025-09-23 15:21:01
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Interfacial and Bulk Properties of Hole Transporting Materials in Perovskite Solar Cells: Spiro-MeTAD versus Spiro-OMeTAD
摘要： Two spiro-MeTAD compounds (1 and 2) were synthesized, characterized by experimental and quantum mechanical methods, and used as hole transporting materials (HTMs) in perovskite solar cells (PSC). The new compounds differ from spiro-OMeTAD only by the presence of methyl substituents as compared to methoxy groups. This modification results in absorption-band blue shift by ~20 nm as compared to spiro-OMeTAD, increased glass transition temperature for 2, and reduced ionization potentials by 0.02-0.12 eV. Hole mobilities larger by five times were obtained for spiro-MeTAD /spiro-MeTAD, which is maintained in the presence of additives. Despite this improvement, J-V measurements in PSCs resulted in power conversion efficiency (PCE) of 17.2% and 17.05% for 1 and 2 HTMs, respectively, as compared to 19.24?% for spiro‐OMeTAD. Photoluminescence measurements of perovskite:HTM layers indicate much stronger quenching in the case of spiro-OMeTAD/spiro-MeTAD. These results point to the dominant importance of the perovskite/HTM interfacial properties as compared to HTM hole-transport properties in the bulk. Given that improved hole-mobility and energy-level alignment are the main targets of the current research efforts in this domain, our results alert on the necessity to give priority to improving perovskite-HTM interaction properties.
关键词： dft,perovskites,energy disorder,solar cells,interaction energy,interfaces
更新于2025-09-23 15:21:01
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25.1% Higha??Efficient Monolithic Perovskite Silicon Tandem Solar Cell with a High Band Gap Perovskite Absorber
摘要： Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum band gap, high quantum efficiency, and high stability of the perovskite. Here, we combine a silicon heterojunction bottom cell with a perovskite top cell with an optimum band gap of 1.68 eV in planar p-i-n tandem configuration. Methylammonium-free FA0.75Cs0.25Pb(I0.8Br0.2)3 perovskite with high Cs-content is investigated for improved stability. A 10% molarity increase to 1.1 M of the perovskite precursor solution resulted in ~75 nm thicker absorber layers and 0.7 mA/cm2 higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of ~80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over five months showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved anti-reflection measures, the high band gap perovskite absorber has the potential for 30% tandem efficiency in the near future.
关键词： interfaces,heterojunction silicon solar cells,perovskite solar cells,thin films,tandem solar cells
更新于2025-09-23 15:21:01
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Sputtered p-type Cu <sub/>x</sub> Zn <sub/>1-x</sub> S back contact to CdTe solar cells
摘要： As thin film cadmium telluride (CdTe) solar cells gain prominence, one particular challenge is optimizing contacts and their interfaces to transfer charge without losses in efficiency. Back contact recombination is still significant and will prevent CdTe solar technology from reaching its full potential in device efficiency, and transparent back contacts have not been developed for bifacial solar technology or multijunction solar cells. To address these challenges, this study investigates sputtered CuxZn1-xS as a p-type semi-transparent back contact material to thin film polycrystalline CdTe solar cells, at Cu concentrations x = 0.30, 0.45 and 0.60. This material is selected for its high hole conductivity (160 to 2,120 S cm-1), wide optical band gap (2.25 to 2.75 eV), and variable ionization potential (approximately 6 to 7 eV) that can be aligned to that of CdTe. We report that without device optimization, CdTe solar cells with these CuxZn1-xS back contacts perform as well as control cells with standard ZnTe:Cu back contacts. We observe no reduction in external quantum efficiency, low contact barrier heights of approximately 0.3 eV, and carrier lifetimes on par with those of baseline CdTe. These cells are relatively stable over one year in air, with VOC and efficiency of the x = 0.30 cell decreasing by only 1% and 3%, respectively. Using SEM and STEM to investigate the CuxZn1-xS?CdTe interface, we demonstrate that the CuxZn1-xS layer segregates into a bilayer of Cu-Te-S and Zn-Cd-S, and thermodynamic reaction calculations support these findings. Despite its bilayer formation, the back contact still functions well. This investigation explains some of the physical mechanisms governing the device stack, inspires future work to understand interfacial chemistry and charge transfer, and elicits optimization to achieve higher efficiency CdTe cells.
关键词： solar cell back contact design,transparent semiconductors,copper zinc sulfide,solar cell interfaces,CdTe photovoltaics
更新于2025-09-23 15:21:01
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2PPE spectroscopy of unoccupied electronic states at CuPc/PTCDA/Ag(111) interfaces
摘要： The unoccupied electronic structure of stacked layers of copper(II)phthalocyanine (CuPc) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on Ag(111) has been investigated by means of two-photon photoemission (2PPE). We find a rich electronic structure comprising at least five unoccupied electronic states which we identify based on their energetic position and their dispersion in momentum space. More specifically, we observe the first and the second image-potential states of the modified Ag(111) surface, as well as the metal–organic interface state (IS) inherent to the PTCDA/Ag(111) interface. Moreover, two additional molecular features are observed for the CuPc/PTCDA/Ag(111) system which we attribute to an unoccupied molecular orbital (LUMO+2) of CuPc. The 2PPE intensity of the IS exhibits a pronounced dependence on the pump photon energy, which closely follows the optical absorption of the outer molecular layer. This strongly points to charge transfer from the optically excited molecules to the interface state.
关键词： charge transfer,PTCDA,metal–organic interfaces,CuPc,organic heterosystems,two-photon photoemission
更新于2025-09-23 15:21:01