Powering AI at the edge: A robust, memristor-based binarized neural network with near-memory computing and miniaturized solar cell.

Memristor-based neural networks provide an exceptional energy-efficient platform for artificial intelligence (AI), presenting the possibility of self-powered operation when paired with energy harvesters. However, most memristor-based networks rely on analog in-memory computing, necessitating a stable and precise power supply, which is incompatible with the inherently unstable and unreliable energy harvesters. In this work, we fabricated a robust binarized neural network comprising 32,768 memristors, powered by a miniature wide-bandgap solar cell optimized for edge applications.

Humidity-Induced Degradation Processes of Halide Perovskites Unveiled by Correlative Analytical Electron Microscopy.

Improving the stability of lead halide perovskite solar cells (PSCs) for industrialization is currently a major challenge. It is shown that moisture induces changes in global PSC performance, altering the nature of the absorber through phase transition or segregation. Understanding how the material evolves in a wet environment is crucial for optimizing device performance and stability.

GaAs/GaInP nanowire solar cell on Si with state-of-the-art and quasi-Fermi level splitting.

With their unique structural, optical and electrical properties, III-V nanowires (NWs) are an extremely attractive option for the direct growth of III-Vs on Si for tandem solar cell applications. Here, we introduce a core-shell GaAs/GaInP NW solar cell grown by molecular beam epitaxy on a patterned Si substrate, and we present an in-depth investigation of its optoelectronic properties and limitations. We report a power conversion efficiency of almost 3.

Industrially Compatible Fabrication Process of Perovskite-Based Mini-Modules Coupling Sequential Slot-Die Coating and Chemical Bath Deposition.

To upscale the emerging perovskite photovoltaic technology to larger-size modules, industrially relevant deposition techniques need to be developed. In this work, the deposition of tin oxide used as an electron extraction layer is established using chemical bath deposition (CBD), a low-cost and solution-based fabrication process. Applying this simple low-temperature deposition method, highly homogeneous SnO films are obtained in a reproducible manner.

Cathodoluminescence mapping of electron concentration in MBE-grown GaAs:Te nanowires.

Cathodoluminescence mapping is used as a contactless method to probe the electron concentration gradient of Te-doped GaAs nanowires. The room temperature and low temperature (10 K) cathodoluminescence analysis method previously developed for GaAs:Si is first validated on five GaAs:Te thin film samples, before extending it to the two GaAs:Te NW samples. We evidence an electron concentration gradient ranging from below 1 × 10cmto 3.

Backside light management of 4-terminal bifacial perovskite/silicon tandem PV modules evaluated under realistic conditions.

Perovskite/silicon tandem modules have recently attracted growing interest as a potential candidate for new generations of solar modules. Combined with a bifacial configuration it can lead to considerable energy yield improvement in comparison to conventional monofacial tandem solar modules. Optical modeling is crucial to analyze the optical losses of perovskite/silicon solar modules and achieve efficient light management.

Stable and high yield growth of GaP and InGaAs nanowire arrays using In as a catalyst.

We report the first investigation of indium (In) as the vapor-liquid-solid catalyst of GaP and InGaAs nanowires by molecular beam epitaxy. A strong asymmetry in the Ga distribution between the liquid and solid phases allows one to obtain pure GaP and In0.2Ga0.

Nanoscale electrical analyses of axial-junction GaAsP nanowires for solar cell applications.

Axial p-n and p-i-n junctions in GaAsP nanowires are demonstrated and analyzed using electron beam induced current microscopy. Organized self-catalyzed nanowire arrays are grown by molecular beam epitaxy on nanopatterned Si substrates. The nanowires are doped using Be and Si impurities to obtain p- and n-type conductivity, respectively.

Nanoplasmonics-enhanced label-free imaging of endothelial cell monolayer integrity.

Surface plasmon resonance imaging (SPRI) is a powerful label-free imaging modality for the analysis of morphological dynamics in cell monolayers. However, classical plasmonic imaging systems have relatively poor spatial resolution along one axis due to the plasmon mode attenuation distance (tens of μm, typically), which significantly limits their ability to resolve subcellular structures. We address this limitation by adding an array of nanostructures onto the metal sensing surface (25 nm thick, 200 nm width, 400 nm period grating) to couple localized plasmons with propagating plasmons, thereby reducing attenuation length and commensurately increasing spatial imaging resolution, without significant loss of sensitivity or image contrast.

Evidence and control of unintentional As-rich shells in GaAs P nanowires.

We report on the detailed composition of ternary GaAsP nanowires (NWs) grown using self-catalyzed vapor-liquid-solid (VLS) growth by molecular beam epitaxy. We evidence the formation of an unintentional shell, which enlarges by vapor-solid growth concurrently to the main VLS-grown core. The NW core and unintentional shell have typically different chemical compositions if no effort is made to adjust the growth conditions.

Optoelectrical modeling of solar cells based on c-Si/a-Si:H nanowire array: focus on the electrical transport in between the nanowires.

By coupling optical and electrical modeling, we have investigated the photovoltaic performances of p-i-n radial nanowires array based on crystalline p-type silicon (c-Si) core/hydrogenated amorphous silicon (a-Si:H) shell. By varying either the doping concentration of the c-Si core, or back contact work function we can separate and highlight the contribution to the cell's performance of the nanowires themselves (the radial cell) from the interspace between the nanowires (the planar cell). We show that the build-in potential (V ) in the radial and planar cells strongly depends on the doping of c-Si core and the work function of the back contact respectively.

Ultrathin Epitaxial Silicon Solar Cells with Inverted Nanopyramid Arrays for Efficient Light Trapping.

Ultrathin c-Si solar cells have the potential to drastically reduce costs by saving raw material while maintaining good efficiencies thanks to the excellent quality of monocrystalline silicon. However, efficient light trapping strategies must be implemented to achieve high short-circuit currents. We report on the fabrication of both planar and patterned ultrathin c-Si solar cells on glass using low temperature (T < 275 °C), low-cost, and scalable techniques.

Influence of a Boron Precursor on the Growth and Optoelectronic Properties of Electrodeposited Zinc Oxide Thin Film.

Highly transparent and conductive materials are required for many industrial applications. One of the interesting features of ZnO is the possibility to dope it using different elements, hence improving its conductivity. Results concerning the zinc oxide thin films electrodeposited in a zinc perchlorate medium containing a boron precursor are presented in this study.

Infrared spectroscopy of molecules with nanorod arrays: a numerical study.

Nanorod arrays with diameters much smaller than the wavelength exhibit sharp resonances with strong electric-field enhancement and angular dependence. They are investigated for enhanced infrared spectroscopy of molecular bonds. The molecule 3-cyanopropyldimethylchlorosilane (CS) is taken as a reference, and its complex permittivity is determined experimentally in the 3-5 μm wavelength range.

Ultrasensitive Characterization of Mechanical Oscillations and Plasmon Energy Shift in Gold Nanorods.

Mechanical vibrational resonances in metal nanoparticles are intensively studied because they provide insight into nanoscale elasticity and for their potential application to ultrasensitive mass detection. In this paper, we use broadband femtosecond pump-probe spectroscopy to study the longitudinal acoustic phonons of arrays of gold nanorods with different aspect ratios, fabricated by electron beam lithography with very high size uniformity. We follow in real time the impulsively excited extensional oscillations of the nanorods by measuring the transient shift of the localized surface plasmon band.

Electrodeposition of ZnO window layer for an all-atmospheric fabrication process of chalcogenide solar cell.

This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution.

Extraordinary optical extinctions through dual metallic gratings.

We report on multiple extraordinary optical extinction (EOE) phenomena achieved through encapsulated dual metallic gratings. They are evidenced in TM polarization by angularly and spectrally resolved transmission measurements in the mid-infrared wavelength range. We show that EOE can be achieved on both sides of the extraordinary optical transmission (EOT) resonance, leading to pass-band filters with an improved rejection rate.

Nanostructure arrays in free-space: optical properties and applications.

Dielectric and metallic gratings have been studied for more than a century. Nevertheless, novel optical phenomena and fabrication techniques have emerged recently and have opened new perspectives for applications in the visible and infrared domains. Here, we review the design rules and the resonant mechanisms that can lead to very efficient light-matter interactions in sub-wavelength nanostructure arrays.

Multi-resonant absorption in ultra-thin silicon solar cells with metallic nanowires.

We propose a design to confine light absorption in flat and ultra-thin amorphous silicon solar cells with a one-dimensional silver grating embedded in the front window of the cell. We show numerically that multi-resonant light trapping is achieved in both TE and TM polarizations. Each resonance is analyzed in detail and modeled by Fabry-Perot resonances or guided modes via grating coupling.

Metal-dielectric bi-atomic structure for angular-tolerant spectral filtering.

We theoretically study metal-dielectric structures made of bi-atomic metallic gratings coupled to a guided-mode dielectric resonator. The bi-atomic pattern grating allows tailoring of the Fourier spectrum of the inverse grating permittivity in order to adapt the frequency gap and obtain a flat dispersion band over a wide angular range. A significant enhancement (two-fold) of the angular tolerance as compared to a simply periodic structure is obtained.

Optical extinction in a single layer of nanorods.

We demonstrate that almost 100% of incident photons can interact with a monolayer of scatterers in a symmetrical environment. Nearly perfect optical extinction through free-standing transparent nanorod arrays has been measured. The sharp spectral opacity window, in the form of a characteristic Fano resonance, arises from the coherent multiple scattering in the array.