Accelerating the Development of Thin Film Photovoltaic Technologies: An Artificial Intelligence Assisted Methodology Using Spectroscopic and Optoelectronic Techniques.

Thin film photovoltaic (TFPV) materials and devices present a high complexity with multiscale, multilayer, and multielement structures and with complex fabrication procedures. To deal with this complexity, the evaluation of their physicochemical properties is critical for generating a model that proposes strategies for their development and optimization. However, this process is time-consuming and requires high expertise. In this context, the adoption of combinatorial analysis (CA) and artificial intelligence (AI) strategies represents a powerful asset for accelerating the development of these complex materials and devices. This work introduces a methodology to facilitate the adoption of AI and CA for the development of TFPV technologies. The methodology covers all the necessary steps from the synthesis of samples for CA to data acquisition, AI-assisted data analysis, and the extraction of relevant information for research acceleration. Each step provides details on the necessary concepts, requirements, and procedures and are illustrated with examples from the literature. Then, the application of the methodology to a complex set of samples from a TFPV production line highlights its ability to rapidly glean significant insights even in intricate scenarios. The proposed methodology can be applied to other types of materials and devices beyond PV and using different characterization techniques.

Fission of multiply charged alkali clusters in helium droplets - approaching the Rayleigh limit.

Electron ionization of helium droplets doped with sodium, potassium or cesium results in doubly and, for cesium, triply charged cluster ions. The smallest observable doubly charged clusters are Na9(2+), K11(2+), and Cs9(2+); they are a factor two to three smaller than reported previously. The size of sodium and potassium dications approaches the Rayleigh limit nRay for which the fission barrier is calculated to vanish, i.e. their fissilities are close to 1. Cesium dications are even smaller than nRay, implying that their fissilities have been significantly overestimated. Triply charged cesium clusters as small as Cs19(3+) are observed; they are a factor 2.6 smaller than previously reported. Mechanisms that may be responsible for enhanced formation of clusters with high fissilities are discussed.

Extracting cluster distributions from mass spectra: IsotopeFit.

The availability of high resolution mass spectrometry in the study of atomic and molecular clusters opens up challenges for the interpretation of the data. In complex systems each resolved mass peak may contain contributions from multiple species because of the isotope structure of constituent elements and because a multitude of different types of clusters with different compositions are present. A computational procedure which can help to identify a specific cluster from this complex dataset and quantify its relative abundance would be extremely helpful to many who work in this field. Here some new software designed for this purpose, known as IsotopeFit, is described.

Helium Droplets Doped with Sulfur and C60.

Clusters of sulfur are grown by passing superfluid helium nanodroplets through a pickup cell filled with sulfur vapor. In some experiments the droplets are codoped with C60. The doped droplets are collided with energetic electrons and the abundance distributions of positively and negatively charged cluster ions are recorded. We report, specifically, distributions of S m+, S m-, and C60S m- containing up to 41 sulfur atoms. We also observe complexes of sulfur cluster anions with helium; distributions are presented for He n S m- with n ≤ 31 and m ≤ 3. The similarity between anionic and cationic C60S m± spectra is in striking contrast to the large differences between spectra of S m+ and S m-.

Formation of HCN+ in heterogeneous reactions of N2(+) and N+ with surface hydrocarbons.

A significant increase of the ion yield at m/z 27 in collisions of low-energy ions of N2(+) and N(+) with hydrocarbon-covered room-temperature or heated surfaces of tungsten, carbon-fiber composite, and beryllium, not observed in analogous collisions of Ar(+), is ascribed to the formation of HCN(+) in heterogeneous reactions between N2(+) or N(+) and surface hydrocarbons. The formation of HCN(+) in the reaction with N(+) indicated an exothermic reaction with no activation barrier, likely to occur even at very low collision energies. In the reaction with N2(+), the formation of HCN(+) was observed to a different degree on these room-temperature and heated (150 and 300 °C) surfaces at incident energies above about 50 eV. This finding suggested an activation barrier or reaction endothermicity of the heterogeneous reaction of about 3-3.5 eV. The main process in N2(+) or N(+) interaction with the surfaces is ion neutralization; the probability of forming the reaction product HCN(+) was very roughly estimated for both N2(+) and N(+) ions to about one in 10(4) collisions with the surfaces.