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We have fabricated an In0.52Al0.48As solar cell lattice-matched to InP with efficiency higher than 14% and maximum external quantum efficiency equal to 81%. High quality, dislocation-free InxAl1-xAs alloyed layers were used to fabricate the single junction solar cell. Photoluminescence of InxAl1-xAs showed good material quality and lifetime of over 200 ps. A high band gap In0.35Al0.65As window was used to increase light absorption within the p-n absorber layer and improve cell efficiency, despite strain. The InAlAs top cell reported here is a key building block for an InP-based three junction high efficiency solar cell consisting of InAlAs/InGaAsP/InGaAs lattice-matched to the substrate. [ABSTRACT FROM AUTHOR]

The surface energy and growth kinetics during Ge deposition on Si(001) were modified by growing the films in a phosphine environment. Islands were formed under a H2 flux as well as in a PH3/H2 atmosphere, but the morphologies were different. The presence of PH3 not only affects the island shape and size but also the composition profile. The dramatical inhibition of Ge/Si intermixing during growth leads to islands richer in Ge compared to undoped islands. [ABSTRACT FROM AUTHOR]

Hafnium silicide islanding occurs spontaneously when metallic Hf is deposited on a Si(001) surface and subsequently annealed at 750 °C. Different coverages were investigated by scanning tunneling microscopy (STM) in order to verify distinct stages of island formation. Small islands occurred for 0.26 ML of deposited Hf, coalescing into flat top islands for longer deposition times. Atomic resolution STM and nanobeam electron diffraction allowed the determination of the mature islands top face structure, identified as the (061) surface of the HfSi2 in the C49 phase. Finally, scanning tunneling spectroscopy was carried out over the smallest islands, demonstrating their metallic behavior. [ABSTRACT FROM AUTHOR]

Metal halide perovskites exhibit optimal properties for optoelectronic devices, ranging from photovoltaics to light‐emitting diodes, utilizing simple fabrication routes that produce impressive electrical and optical tunability. As perovskite technologies continue to mature, an understanding of their fundamental properties at length scales relevant to their morphology is critical. In this review, an overview is presented of the key insights into perovskite material properties provided by measurement methods based on the atomic force microscopy (AFM). Specifically, the manner in which AFM‐based techniques supply valuable information regarding electrical and chemical heterogeneity, ferroelectricity and ferroelasticity, surface passivation and chemical modification, ionic migration, and material/device stability is discussed. Continued advances in perovskite materials will require multimodal approaches and machine learning, where the output of these scanning probe measurements is combined with high spatial resolution structural and chemical information to provide a complete nanoscale description of materials behavior and device performance. [ABSTRACT FROM AUTHOR]

An approach for an all lattice-matched multijunction solar cell optimized design is presented with 5.807 Å lattice constant, together with a detailed analysis of its performance by means of full device modeling. The simulations show that a (1.93 eV)In0.37Al0.63As/(1.39 eV)In0.38Ga0.62As0.57P0.43/(0.94 eV)In0.38Ga0.62As 3-junction solar cell can achieve efficiencies >51% under 100-suns illumination (with Voc = 3.34 V). As a key proof of concept, an equivalent 3-junction solar cell lattice-matched to InP was fabricated and tested. The independently connected single junction solar cells were also tested in a spectrum splitting configuration, showing similar performance to a monolithic tandem device, with Voc = 1.8 V. [ABSTRACT FROM AUTHOR]

Structural color filters have recently blossomed as a superior alternative to organic dyes or chemical pigments owing to their remarkable durability and compactness. With appropriate design, nanostructure‐induced photonic or plasmonic resonance modes can give rise to either enhancement in transmission or suppression in the reflection within specific wavelength ranges in the optical regime, generating distinctive colors. However, the static optical properties due to fixed structural geometry and size after fabrication hinder their deployment in many cutting‐edge technologies requiring adaptive complexion changes. Here, a multilayer thin film‐based color filter incorporating Mg and MgO, earth‐abundant and biodegradable materials, is devised. The devices display vivid hues spanning a broad gamut via the control of the film thickness. They also exhibit minimal color changes with varying angle views up to 40°–50°. Moreover, the tones fade away instantly upon immersion in water and then progressively transition to a different hue with the complete removal of the Mg‐containing layers, realizing transient color responses. This approach holds great promise for alternative pixels with irreversible color‐change capability as well as zero‐power consumption and low cost, while making use of biodegradable materials. [ABSTRACT FROM AUTHOR]

Metal halide perovskites (MHP) can be made more stable through the addition of small amounts of cesium. Despite the improvement, these multication absorbers still display strong environmental sensitivity to any combination of factors, including water, oxygen, bias, temperature, and light. Here, the relationship is elucidated between light absorption, charge carrier radiative recombination, and relative humidity (rH) for the Cs0.05FA0.79MA0.16Pb(I0.83Br0.17)3 composition, revealing partially reversible reductions in the extinction coefficient and fully reversible 25× enhancements in absolute light emission registered across the same humidity cycles up to 70% rH. With in situ excitation wavelength‐dependent measurements, irreversible changes are identified in the perovskite after a single cycle of humidity‐dependent photoluminescence (PL) performed with 450 nm excitation. The in situ measurement platform can be extended to test the effect of other stressors on thin films' optical behavior. [ABSTRACT FROM AUTHOR]

Metallic nanostructures and thin films are fundamental building blocks for next‐generation nanophotonics. Yet, the fixed permittivity of pure metals often imposes limitations on the materials employed and/or on device performance. Alternatively, metallic mixtures, or alloys, represent a promising pathway to tailor the optical and electrical properties of devices, enabling further control of the electromagnetic spectrum. In this Review, a survey of recent advances in photonics and plasmonics achieved using metal alloys is presented. An overview of the primary fabrication methods to obtain subwavelength alloyed nanostructures is provided, followed by an in‐depth analysis of experimental and theoretical studies of their optical properties, including their correlation with band structure. The broad landscape of optical devices that can benefit from metallic materials with engineered permittivity is also discussed, spanning from superabsorbers and hydrogen sensors to photovoltaics and hot electron devices. This Review concludes with an outlook of potential research directions that would benefit from the on demand optical properties of metallic mixtures, leading to new optoelectronic materials and device opportunities. [ABSTRACT FROM AUTHOR]

Metal Halide Perovskites: Imaging Metal Halide Perovskites Material and Properties at the Nanoscale (Adv. Keywords: artificial intelligence; atomic force microscopy; functional imaging; halide perovskites; nanoscale properties EN artificial intelligence atomic force microscopy functional imaging halide perovskites nanoscale properties 1 1 1 07/16/20 20200714 NES 200714 As halide perovskite technologies continue to mature, an understanding of their fundamental properties at length scales relevant to their morphology is critical. Artificial intelligence, atomic force microscopy, functional imaging, halide perovskites, nanoscale properties. [Extracted from the article]

Abstract: A tandem ionization chamber was developed for quality control programs of X-ray equipment used in conventional radiography and mammography. A methodology for the use of the tandem chamber in the constancy check of diagnostic X-ray beam qualities was established. The application at a medical X-ray imaging facility of this established methodology is presented. The use of the tandem chamber in the constancy check of diagnostic X-ray beam qualities is a useful method to control the performance of the X-ray equipment. [Copyright &y& Elsevier]

Abstract: Surface plasmon polaritons (SPPs) enable the deep subwavelength confinement of an electromagnetic field, which can be used in optical devices ranging from sensors to nanoscale lasers. However, the limited number of metals that satisfy the required boundary conditions for SPP propagation in a metal/dielectric interface severely limits its occurrence in the visible range of the electromagnetic spectrum. We introduce the strategy of engineering the band structure of metallic materials by alloying. We experimentally and theoretically establish the control of the dispersion relation in Ag–Au alloys by varying the film chemical composition. Through X‐ray photoelectron spectroscopy (XPS) measurements and partial density‐of‐states calculations we deconvolute the d band contribution of the density‐of‐states from the valence band spectrum, showing that the shift in energy of the d band follows the surface plasmon resonance change of the alloy. Our density functional theory calculations of the alloys band structure predict the same variation of the threshold of the interband transition, which is in very good agreement with our optical and XPS experiments. By elucidating the correlation between the optical behavior and band structure of alloys, we anticipate the fine control of the optical properties of metallic materials beyond pure metals. [ABSTRACT FROM AUTHOR]

Abstract: Optoelectronic materials are the backbone of today's high‐tech industry. To customize their response, one can directly modify the atomic arrangement, chemical composition, lattice strain, or doping of the semiconductor. However, these processes frequently cause undesirable effects resulting from induced defects. Here, a novel concept is demonstrated to actively tune the optoelectronic response of a material through tailored photon recycling. Without altering the material's intrinsic structure, doping, or temperature, the reabsorption of emitted photons within GaAs is modulated to control its carrier density. This approach is used to create a diode that can change its emission wavelength, a solar cell with improved open‐circuit voltage, and an actively controlled, gate‐free current modulator. These results represent a new platform to enable materials with tailored optoelectronic response based on photonic manipulation rather than semiconductor engineering. [ABSTRACT FROM AUTHOR]

Li metal is the preferred anode material for all-solid-state Li batteries. However, a stable plating and stripping of Li metal at the anode–solid electrolyte interface remains a significant challenge particularly at practically feasible current densities. This problem usually relates to high and/or inhomogeneous Li-electrode–electrolyte interfacial impedance and formation and growth of high-aspect-ratio dendritic Li deposits at the electrode–electrolyte interface, which eventually shunt the battery. To better understand details of Li metal plating, we use operando electron microscopy and Auger spectroscopy to probe nucleation, growth, and stripping of Li metal during cycling of a model solid-state Li battery as a function of current density and oxygen pressure. We find a linear correlation between the nucleation density of Li clusters and the charging rate in an ultrahigh vacuum, which agrees with a classical nucleation and growth model. Moreover, the trace amount of oxidizing gas (≈10–6 Pa of O2) promotes the Li growth in a form of nanowires due to a fine balance between the ion current density and a growth rate of a thin lithium-oxide shell on the surface of the metallic Li. Interestingly, increasing the partial pressure of O2 to 10–5 Pa resumes Li plating in a form of 3D particles. Our results demonstrate the importance of trace amounts of preexisting or ambient oxidizing species on lithiation processes in solid-state batteries. [ABSTRACT FROM AUTHOR]

Hybrid organic-inorganic perovskites based on methylammonium lead (MAPbI3) are an emerging material with great potential for high-performance and low-cost photovoltaics. However, for perovskites to become a competitive and reliable solar cell technology their instability and spatial variation must be understood and controlled. While the macroscopic characterization of the devices as a function of time is very informative, a nanoscale identification of their real-time local optoelectronic response is still missing. Here, we implement a four-dimensional imaging method through illuminated heterodyne Kelvin probe force microscopy to spatially (<50 nm) and temporally (16 s/scan) resolve the voltage of perovskite solar cells in a low relative humidity environment. Local open-circuit voltage (Voc) images show nanoscale sites with voltage variation >300 mV under 1-sun illumination. Surprisingly, regions of voltage that relax in seconds and after several minutes consistently coexist. Time-dependent changes of the local Voc are likely due to intragrain ion migration and are reversible at low injection level. These results show for the first time the real-time transient behavior of the Voc in perovskite solar cells at the nanoscale. Understanding and controlling the light-induced electrical changes that affect device performance are critical to the further development of stable perovskite-based solar technologies. [ABSTRACT FROM AUTHOR]

Keywords: color filters; earth-abundant materials; magnesium; structural colors; transient photonics EN color filters earth-abundant materials magnesium structural colors transient photonics 1 1 1 07/06/22 20220704 NES 220704 Marina S. Leite and co-workers (article number 2200159) demonstrate thin-film-based color filters using Mg and MgO, both biodegradable materials. Color filters, earth-abundant materials, magnesium, structural colors, transient photonics A transient color response is attained by etching the Mg-containing layers with water, which reveals the hue of a bottom Fabry-Pérot cavity structure. [Extracted from the article]

A novel imaging platform to determine the open‐circuit voltage of solar cells with nanoscale spatial resolution is presented. Here, a variant of illuminated Kelvin probe force microscopy can be implemented to quantify local variations in the voltage of different solar cells. The new metrology can be applied to any optoelectronic device, and works in ambient environments. [ABSTRACT FROM AUTHOR]

Abstract: We investigate local electronic properties of cadmium telluride solar cells using electron beam induced current (EBIC) measurements with patterned contacts. EBIC measurements are performed with a spatial resolution as high as ≈20nm both on the top surface and throughout the cross-section of the device, revealing a remarkable degree of electrical inhomogeneity near the p–n junction and enhanced carrier collection in the vicinity of grain boundaries (GB). Simulation results of low energy EBIC suggest that the band bending near a GB is downward, with a magnitude of at least 0.2eV for the most effective current-collecting GBs. Furthermore, we demonstrate a new approach to investigate local open-circuit voltage by applying an external bias across electrical contact with a point electron-beam injection. The length scale of the nanocontacts is on the length scale of a single or a few grains, confining current path with highly localized photo-generated carriers. [Copyright &y& Elsevier]

Light absorption, metal halide perovskites, photoluminescence, environmentally-dependent measurements Keywords: environmentally-dependent measurements; light absorption; metal halide perovskites; photoluminescence EN environmentally-dependent measurements light absorption metal halide perovskites photoluminescence 1 1 1 09/22/21 20210920 NES 210920 Marina S. Leite and co-workers (article number 2100710) unveil the relationship between light absorption, charge carrier radiative recombination, and relative humidity (rH) for the Cs SB 0.05 sb FA SB 0.79 sb MA SB 0.16 sb Pb(I SB 0.83 sb Br SB 0.17 sb ) SB 3 sb halide perovskite. Water-Induced and Wavelength-Dependent Light Absorption and Emission Dynamics in Triple-Cation Halide Perovskites (Advanced Optical Materials 18/2021). [Extracted from the article]