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The open-circuit voltage (V $_\text{oc}$ ) of CdTe-based photovoltaics may be limited by carrier recombination at interfaces (front or back) or in the absorber layer. Reduction in recombination of a given dominant mechanisms can lead to improved device performance if the remaining mechanisms turn on in a narrow bias range just below the open circuit voltage. In this article, we demonstrate enhanced performance by incorporating solution-processed Cu $_\text{x}$ AlO $_\text{y}$ to form a back-buffer layer in CdSe/CdTe devices. Outstanding minority carrier lifetimes of 656 and 4.2 ns were measured with glass side and film side illumination for device stacks processed with Cu $_\text{x}$ AlO $_\text{y}$ . Devices demonstrated efficiencies of up to 17.4% with V $_\text{oc}$ of 859 mV, FF of 75.6% and J $_\text{sc}$ of 26.9 mAcm−2 while the efficiency of the reference device without the back-buffer layer was 16.5% with V $_\text{oc}$ of 839 mV, FF of 70.6%, and J $_\text{sc}$ of 27.9 mAcm−2.

Several studies have focused on the antimicrobial effects of cerium oxide nanoparticles (CeO(2)-NP) but few have focused on their effects on bacteria under initial biofilm formation conditions. Streptococcus mutans is a prolific biofilm former contributing to dental caries in the presence of fermentable carbohydrates and is a recognized target for therapeutic intervention. CeO(2)-NP derived solely from Ce(IV) salt hydrolysis were found to reduce adherent bacteria by approximately 40% while commercial dispersions of “bare” CeO(2)-NP (e.g., 3 nm, 10–20 nm, 30 nm diameter) and Ce(NO(3))(3)•6H(2)O were either inactive or observed to slightly increase biofilm formation under similar in vitro conditions. Planktonic growth and dispersal assays support a non-bactericidal mode of biofilm inhibition active in the initial phases of S. mutans biofilm production. Human cell proliferation assays suggest only minor effects of hydrolyzed Ce(IV) salts on cellular metabolism at concentrations up to 1 mM Ce, with less observed toxicity compared to equimolar concentrations of AgNO(3). The results presented herein have implications in clinical dentistry.

Materials for studying biological interactions and for alternative energy applications are continuously under development. Semiconductor quantum dots are a major part of this landscape due to their tunable optoelectronic properties. Size-dependent quantum confinement effects have been utilized to create materials with tunable bandgaps and Auger recombination rates. Other mechanisms of electronic structural control are under investigation as not all of a material's characteristics are affected by quantum confinement. Demonstrated here is a new structure-property concept that imparts the ability to spatially localize electrons or holes within a core/shell heterostructure by tuning the charge carrier's kinetic energy on a parabolic potential energy surface. This charge carrier separation results in extended radiative lifetimes and in continuous emission at the single-nanoparticle level. These properties enable new applications for optics, facilitate novel approaches such as time-gated single-particle imaging, and create inroads for the development of other new advanced materials.

Magnesium batteries have attracted great attention as an alternative to Li-ion batteries but still suffer from limited choice of positive electrode materials. V2O5 exhibits high theoretical capacities, but previous studies have been mostly limited to α-V2O5. Herein, we report on the β-V2O5 polymorph as a Mg intercalation electrode. The structural changes associated with the Mg2+ (de-) intercalation were analyzed by a combination of several characterization techniques: in situ high resolution X-ray diffraction, scanning transmission electron microscopy, electron energy-loss spectroscopy, and X-ray absorption spectroscopy. The reversible capacity reached 361 mAh g-1, the highest value found at room temperature for V2O5 polymorphs., The authors are grateful to the ALBA synchrotron for beamtime (proposal 2021024935). The Spanish Agencia Estatal de Investigación Severo Ochoa FUNFUTURE (CEX2019-000917-S) Excellence Centre distinction, the European Union’s Horizon 2020 research and innovation programme under grant agreement 824066 (E-MAGIC), and Junta de Andalucía (EMERGIA programme, grant 00153) are gratefully acknowledged. G.C.B.A., P.P., R.F.K., and J.C. were solely supported by the Joint Center for Energy Storage Research (JCESR) and Energy Innovation Hub funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences. I.R. acknowledges support from the National Science Foundation via grant DMR-2118020. This research used resources of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract DE-SC0012704. The authors acknowledge the free distribution of VESTA software, With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Magnesium batteries have attracted great attention as an alternative to Li-ion batteries but still suffer from limited choice of positive electrode materials. V

Self-organization is a phenomenon that occurs under certain circumstances with different types of materials – liquids, bulk, and thin films, organic, inorganic or hybrid solids. This unique effect ...

Perovskite oxides are an important class of oxygen evolution reaction (OER) catalysts in alkaline media, despite the elusive nature of their active sites. Here, we demonstrate that the origin of the OER activity in a La1-xSrxCoO3 model perovskite arises from a thin surface layer of Co hydr(oxy)oxide (CoOxHy) that interacts with trace-level Fe species present in the electrolyte, creating dynamically stable active sites. Generation of the hydr(oxy)oxide layer is a consequence of a surface evolution process driven by the A-site dissolution and O-vacancy creation. In turn, this imparts a 10-fold improvement in stability against Co dissolution and a 3-fold increase in the activity-stability factor for CoOxHy/LSCO when compared to nanoscale Co-hydr(oxy)oxides clusters. Our results suggest new design rules for active and stable perovskite oxide-based OER materials.

α-V2O5 has been extensively explored as a Mg2+ intercalation host with potential as a battery cathode, offering high theoretical capacities and potentials vs. Mg2+/Mg. However, large voltage hysteresis is observed with Mg insertion and extraction, introducing significant and unacceptable round-trip energy losses with cycling. Conventional interpretations suggest that bulk ion transport of Mg2+ within the cathode particles is the major source of this hysteresis. Herein, we demonstrate that nanosizing α-V2O5 gives a measurable reduction to voltage hysteresis on the first cycle that substantially raises energy efficiency, indicating that mechanical formatting of the α-V2O5 particles contributes to hysteresis. However, no measurable improvement in hysteresis is found in the nanosized α-V2O5 in latter cycles despite the much shorter diffusion lengths, suggesting that other factors aside from Mg transport, such as Mg transfer between the electrolyte and electrode, contribute to this hysteresis. This observation is in sharp contrast to the conventional interpretation of Mg electrochemistry. Therefore, this study uncovers critical fundamental underpinning limiting factors in Mg battery electrochemistry, and constitutes a pivotal step towards a high-voltage, high-capacity electrode material suitable for Mg batteries with high energy density.

The development and implementation of high-stability monochromators in state-of-the-art aberration-corrected scanning transmission electron microscopes has enabled materials characterization with an energy resolution as good as 3 meV. This allows the vibrational modes, which would otherwise be obscured by the energy spread of the electron beam, to be probed with very high precision in molecular materials. Since the vibrational energies depend on the weight of the atomic nuclei, vibrational spectroscopy can distinguish isotopes whose only difference lies in their neutron content. This opens up isotopic analysis and mapping in transmission electron microscopy as two important new research areas. Here, we review the monochromated electron energy loss spectroscopy (EELS) instrumentation, discuss optimal methods for probing beam-sensitive materials without destroying them, and review key nanoscale isotope-resolved results.

Irreversible structural transformation in intercalation-type cathode materials, which has been frequently observed, has been perceived as a principal cause of capacity fading and voltage decay in (...

Calcium-ion batteries (CIBs) are under investigation as next-generation energy storage devices due to their theoretically high operating potentials and lower costs tied to the high natural abundanc...

Liquid cell transmission electron microscopy (TEM) has become an essential tool for studying the structure and properties of both hard and soft condensed-matter samples, as well as liquids themselves. Liquid cell sample holders, often consisting of two thin window layers separating the liquid sample from the high vacuum of the microscope column, have been designed to control in situ conditions, including temperature, voltage/current, or flow through the window region. While high-resolution and time-resolved TEM imaging probes the structure, shape, and dynamics of liquid cell samples, information about the chemical composition and spatially resolved bonding is often difficult to obtain due to the liquid thickness, the window layers, the holder configuration, or beam-induced radiolysis. In this article, we review different approaches to quantitative liquid cell electron microscopy, including recent developments to perform energy-dispersive x-ray and electron energy-loss spectroscopy experiments on samples in a liquid environment or the liquid itself. We also cover graphene liquid cells and other ultrathin window layer holders.

Nonaqueous Mg batteries can theoretically reach high energy density with cost-effective materials, yet no such device to date has performance competitive with Li-ion technologies. A major barrier i...

Lattice Mg2+ in a tailored solid solution spinel, MgCrMnO4, is electrochemically utilized at high Mn-redox potentials in a nonaqueous electrolyte. Complementary evidence from experimental and theor...

The use of oxide cathodes in Mg batteries would unlock a potential energy storage system that delivers high energy density. However, poor kinetics of Mg diffusion in known solid oxide lattices stro...

Transition metal dichalcogenides (TMDCs) have garnered much attention recently due to their remarkable performance for different electrochemical systems. In this study, we report on the synthesis a...

Measuring the current induced by the electron beam in an electron microscope is an approach that is used to map the generation and collection of charge carriers in the presence of an internal electric field in semiconductor devices. Here, we demonstrate that EBIC measurements can be conducted simultaneously with atomic-resolution high-angle annular dark field imaging in an aberration-corrected scanning transmission electron microscopy using a GaAs p-i-n nanowire diode. We explore the effects of the significantly smaller profile of the 200 kV electron probe within the sample compared to the SEM configuration. We further demonstrate that the effects of electron beam induced point defects and surface passivation layers can be directly determined using the STEM-EBIC approach.

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) are a large family of materials actively studied for various applications, especially in the field of energy storage. To date, MXenes are commonly synthesized by etching the layered ternary compounds, MAX phases. Here we demonstrate a direct synthetic route for scalable and atom-economic synthesis of MXenes, including phases that have not been synthesized from MAX phases, by the reactions of metals and metal halides with graphite, methane or nitrogen. These directly synthesized MXenes showed excellent energy storage capacity for Li-ion intercalation. The direct synthesis enables chemical vapor deposition (CVD) growth of MXene carpets and complex spherulite-like morphologies. The latter form in a process resembling the evolution of cellular membranes during endocytosis., Comment: 7 pages, 3 figures

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Thin titanium carbide films were prepared by ion beam sputtering of titanium and graphite targets followed by thermal annealing at 600 °C in vacuum and irradiation by Ar+ ions up to a fluence of 1015 ions/cm2. The stoichiometry of the films was analyzed by RBS and NRA methods, it was found to be Ti2.2C. The crystalline structure of the films was analyzed by STEM and EELS microscopic methods: before irradiation it was mostly amorphous with crystalline parts and visible network of micro-voids, crystallization and formation of laminar structure was observed after irradiation. The irradiated part showed corrugated surface morphology and a dense network of nano-openings. The thickness of the films increased from ca 67 nm to ca 83 nm. Obviously, the effect of the ion irradiation promoted the recrystallization and self-organization of the structure, resulting in the nano-laminar phase of Ti2C.

V2O5 is of interest as a Mg intercalation electrode material for Mg batteries, both in its thermodynamically stable layered polymorph (α-V2O5) and in its metastable tunnel structure (ζ-V2O5). However, such oxide cathodes typically display poor Mg insertion/removal kinetics, with large voltage hysteresis. Herein, we report the synthesis and evaluation of nanosized (ca. 100 nm) ζ-V2O5 in Mg-ion cells, which displays significantly enhanced electrochemical kinetics compared to microsized ζ-V2O5. This effect results in a significant boost in stable discharge capacity (130 mA h g-1) compared to bulk ζ-V2O5 (70 mA h g-1), with reduced voltage hysteresis (1.0 V compared to 1.4 V). This study reveals significant advancements in the use of ζ-V2O5 for Mg-based energy storage and yields a better understanding of the kinetic limiting factors for reversible magnesiation reactions into such phases.