Impact of Multivalent Cations on Interfacial Layering in Water-In-Salt Electrolytes
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Chemistry↗
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Local Viscosity of Interfacial Layers in Polymer Nanocomposites Measured by Magnetic Heating
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99 GENERAL AND MISCELLANEOUS↗
Enhancing interfacial charge transfer in a WO 3 /BiVO 4 photoanode heterojunction through gallium and tungsten co-doping and a sulfur modified Bi 2 O 3 interfacial layer
Photoanodes containing a WO 3 /BiVO 4 heterojunction have demonstrated promising photoelectrochemical water splitting performance, but the ability to effectively passivate the WO 3 /BiVO 4 interface has limited charge transport and collection.
14 SOLAR ENERGY↗
Entanglement density and particle dynamics in rigid interfacial layers of polymer nanocomposites
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99 GENERAL AND MISCELLANEOUS↗
Thermally induced PtOx interfacial layer enhances stability of Pt/β-Ga2O3 vertical Schottky diodes
This study investigates the long-term stability of Pt/β-Ga2O3 field-plated Schottky barrier diodes at high temperatures, with extended thermal cycling and soaking stress. The device characteristics reveal a strong dependence on operating temperature, leading to an ON/OFF current ratio of ∼10× at ±3 V and 600 °C. Extensive thermal cycling (25 cycles over 100 h) between room temperature and 350 °C shows that leakage currents stabilize after the initial ten cycles. This stabilization is likely due to the formation of a thin PtOx layer at the Pt/β-Ga2O3 interface, as confirmed by high-resolution scanning transmission electron microscopy. Further exposure to a constant 350 °C environment for 10 h reveals a slight increase in the leakage current from 10−7 to 10−6 A at −5 V and degradation of the forward current, due to potential thermodynamic instability of the Ohmic contacts. This study provides insights into the changes in the Pt/β-Ga2O3 diode performance with thermal stress, offering a basis for predicting the device’s operational reliability at high temperatures for sensing and power applications.
08 HYDROGEN↗
Optimum Interfacial Layers For Fiber/Metal Composites
Report presents theoretical stress-analysis study of some of factors affecting choice of thin layer of material placed at interface between each fiber and matrix of ceramic-fiber/metal-matrix composite. Effects of thickness, modulus of elasticity, and coefficient of thermal expansion considered.
Lerch, Bradley A.↗
Compliant Interfacial Layers in Thermoelectric Devices
A thermoelectric power generation device is disclosed using one or more mechanically compliant and thermally and electrically conductive layers at the thermoelectric material interfaces to accommodate high temperature differentials and stresses induced thereby. The compliant material may be metal foam or metal graphite composite (e.g. using nickel) and is particularly beneficial in high temperature thermoelectric generators employing Zintl thermoelectric materials. The compliant material may be disposed between the thermoelectric segments of the device or between a thermoelectric segment and the hot or cold side interconnect of the device.
Firdosy, Samad A.↗
Effect of interfacial oxide layers on the current-voltage characteristics of Al-Si contacts
Aluminum-silicon contacts with very thin interfacial oxide layers and various surface impurity concentrations are studied for both n and p-type silicon. To determine the surface impurity concentrations on p(+)-p and n(+)-n structures, a modified C-V technique was utilized. Effects of interfacial oxide layers and surface impurity concentrations on current-voltage characteristics are discussed based on the energy band diagrams from the conductance-voltage plots. The interfacial oxide and aluminum layer causes image contrasts on X-ray topographs.
Porter, W. A.↗
Implications of Electron Transport Layer and Back Metal Contact Variations in Tin–Lead Perovskite Solar Cells Assessed by Spectroscopic Ellipsometry and External Quantum Efficiency
The structural and optical properties of hybrid organic–inorganic metal halide perovskite solar cells are measured by spectroscopic ellipsometry to reveal an optically distinct interfacial layer among the back contact metal, charge transport, and absorber layers. Understanding how this interfacial layer impacts performance is essential for developing higher performing solar cells. Here, this interfacial layer is modeled by Bruggeman effective medium approximations (EMAs) to contain perovskite, C 60 , BCP, and metal. External quantum efficiency (EQE) simulations that consider scattering, electronic losses, and the formation of nonparallel interfaces are created with input derived from ellipsometry structural-optical models and compared with experimental EQE to estimate optical losses. This nonplanar interface causes optical losses in short circuit current density (JSC) of up to 1.2 mA cm –2 . A study of glass/C 60 /SnO 2 /Ag or Cu and glass/C 60 /BCP/Ag film stacks shows that C 60 and BCP mix, but replacing BCP with SnO 2 can prevent mixing between the ETLs to prevent contact between C 60 and back contact metal and enable the formation of a planar interface between ETLs and back contact metals.
14 SOLAR ENERGY↗
Influence of the Graft Length on Nanocomposite Structure and Interfacial Dynamics
Both the dispersion state of nanoparticles (NPs) within polymer nanocomposites (PNCs) and the dynamical state of the polymer altered by the presence of the NP/polymer interfaces have a strong impact on the macroscopic properties of PNCs. In particular, mechanical properties are strongly affected by percolation of hard phases, which may be NP networks, dynamically modified polymer regions, or combinations of both. In this article, the impact on dispersion and dynamics of surface modification of the NPs by short monomethoxysilanes with eight carbons in the alkyl part (C 8 ) is studied. As a function of grafting density and particle content, polymer dynamics is followed by broadband dielectric spectroscopy and analyzed by an interfacial layer model, whereas the particle dispersion is investigated by small-angle X-ray scattering and analyzed by reverse Monte Carlo simulations. NP dispersions are found to be destabilized only at the highest grafting. The interfacial layer formalism allows the clear identification of the volume fraction of interfacial polymer, with its characteristic time. The strongest dynamical slow-down in the polymer is found for unmodified NPs, while grafting weakens this effect progressively. The combination of all three techniques enables a unique measurement of the true thickness of the interfacial layer, which is ca. 5 nm. Finally, the comparison between longer (C 18 ) and shorter (C 8 ) grafts provides unprecedented insight into the efficacy and tunability of surface modification. It is shown that C 8 -grafting allows for a more progressive tuning, which goes beyond a pure mass effect.
36 MATERIALS SCIENCE↗
Low cost AMOS solar cell development
Recent developments at JPL have demonstrated that high conversion efficiencies are found with GaAs metal semiconductor solar cells when a particular heat treatment processing step is used to introduce an interfacial layer between the metal and the semiconductor. The new cell, called AMOS (Antireflection-Coated Metal-Oxide-Semiconductor), has open circuit voltages of 0.68-0.72 volts and efficiencies of 15% under terrestrial sunlight, as compared to values of 0.45-0.48 volts and 10%, respectively, for similar cells without an interfacial layer. Potentially higher efficiencies are feasible as further improvements are made in optimizing the interfacial layer effect and in increasing the blue response of the cells. A thin film AMOS cell is proposed that uses a thin recrystallized germanium (Ge) layer between a low cost metal substrate and the vapor phase epitaxially (VPE)-grown GaAs.
Stirn, R. J.↗
Electron/hole selectivity in organic semiconductor contacts for solar energy conversion (Final Report)
Four major and accomplishments for the project "Electron/hole selectivity in organic semiconductor contacts for solar energy conversion.'' are reported. The first is a development of a model describing the contact-determined behavior of a solar cell. The most basic solar cell consists of an intrinsic (pure) semiconductor that acts as an absorber to which contacts are made that provide the asymmetry needed to create a driving force (voltage) for the directional flow of electrons (current), in other words, to convert sunlight into electrical energy. The asymmetry at the contacts comes from the different rate at which electrons and holes, the charge carriers generated by illumination, are collected. We developed a model that describes the ideal current-voltage, and hence energy converting properties, of an ideal photovoltaic that is entirely determined by the kinetics for these charge collection processes. Second, we measured how organic semiconductor interfacial layers impact contact electron and hole transfer rates at semiconductor interfaces and described how these concepts do or do not determine the open-circuit voltage of a solar cell. The work clearly controverts common general misconceptions about the action of contact interfacial layers, such as the idea that improved selectivity for one carrier over the other results from decreased recombination, and quantitatively demonstrates how specific interfacial layer materials act to improve the efficiency of a solar cell. Third, we measured the sub-band gap external quantum efficiency (EQE) of a series of organometal halide perovskite (“perovskite”) solar cells. These measurements quantified band-tailing and revealed defect states, which can cause recombination, that correlate with composition, performance, and hysteresis. Finally, we developed a semiconductor bipolar membrane that uses light to pump ions. This structure is unique among systems that drive ion gradients using light in that it is designed to pump salt rather than one sign of ion; it is a photochemical salt pump.
14 SOLAR ENERGY↗
Ion-conductive organic networks for battery applications
An anode includes: (1) a current collector; and (2) an interfacial layer disposed over the current collector. The interfacial layer includes an ion-conductive organic network including anionic coordination units, organic linkers bonded through the anionic coordination units, and counterions dispersed in the ion-conductive organic network.
Bao, Zhenan↗
Stitching two-dimensional atomic crystals by atomic layer deposition as stable interfaces for batteries
An anode includes: (1) a current collector; and (2) an interfacial layer disposed over the current collector. The interfacial layer includes a film of a layered material and a reinforcing material selectively disposed over certain regions of the film, while other regions of the film remain exposed from the reinforcing material.
Cui, Yi↗
Turning Rubber into a Glass: Mechanical Reinforcement by Microphase Separation
Supramolecular associations provide a promising route to functional materials with properties such as self-healing, easy recyclability or extraordinary mechanical strength and toughness. The latter benefit especially from the transient character of the formed network, which enables dissipation of energy as well as regeneration of the internal structures. However, recent investigations revealed intrinsic limitations in the achievable mechanical enhancement. Here we present studies of a set of telechelic polymers with hydrogen-bonding chain ends exhibiting an extraordinarily high, almost glass-like, rubbery plateau. This is ascribed to the segregation of the associative ends into clusters and formation of an interfacial layer surrounding these clusters. An approach adopted from the field of polymer nanocomposites provides a quantitative description of the data and reveals the strongly altered mechanical properties of the polymer in the interfacial layer. These results demonstrate how employing phase separating dynamic bonds can lead to the creation of high-performance materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Interfacial electronic states of misfit heterostructure between hexagonal ZnO and cubic NiO
The combination of materials with dissimilar symmetries can induce a large amount of stress at the interfacial layer of films, thereby promoting the appearance of novel properties in related devices. The study of the interfacial state is critical for determining the inner mechanism. In this work, the misfit heterostructure between cubic NiO films and wurtzite ZnO is investigated. A NiO film grown using molecular beam epitaxy on a ZnO substrate shows a highly (100)-oriented texture featuring three domains with a rotation angle of 30°, which is in agreement with first principles calculations. Misfit-induced dislocations and lattice distortions within the interfacial layers of the NiO film give rise to interfacial electronic states, which are different from those in bulk; these electronic states are analyzed by in situ synchrotron-based x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, x-ray absorption spectroscopy, and ex situ electron energy loss spectroscopy. Additionally, the origin of these interfacial states is discussed. This work aims to provide insights for the integration of semiconducting hexagonal ZnO with other functional materials that have a cubic symmetry. Additionally, we investigate the integration of photon and electron-based techniques to explore the interfacial states of complex interfaces, which is an important aspect of material science.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Exact Solution to Stationary Onset of Convection Due to Surface Tension Variation in a Multicomponent Fluid Layer With Interfacial Deformation
Stationary onset of convection due to surface tension variation in an unbounded multicomponent fluid layer is considered. Surface deformation is included and general flux boundary conditions are imposed on the stratifying agencies (temperature/composition) disturbance equations. Exact solutions are obtained to the general N-component problem for both finite and infinitesimal wavenumbers. Long wavelength instability may coexist with a finite wavelength instability for certain sets of parameter values, often referred to as frontier points. For an impermeable/insulated upper boundary and a permeable/conductive lower boundary, frontier boundaries are computed in the space of Bond number, Bo, versus Crispation number, Cr, over the range 5 x 10(exp -7) less than or equal to Bo less than or equal to 1. The loci of frontier points in (Bo, Cr) space for different values of N, diffusivity ratios, and, Marangoni numbers, collapsed to a single curve in (Bo, D(dimensional variable)Cr) space, where D(dimensional variable) is a Marangoni number weighted diffusivity ratio.
Skarda, J. Raymond Lee↗