transitions between those occurring upon heating. The most-studied compound, methylammonium lead trihalide, features an optical bandgap between 1.5 and 2.3 eV depending on the halide content. After combining the perovskite compound as active material with Spiro-MeOTAD as solid-state hole-transporting medium, excellent device performances have been demonstrated with ever increasing efficiencies. [8] Recent work on alternative halide perovskites have shown high photovoltaic conversion efficiencies that indicate the perspective of surmounting 30% of efficiency by a single-junction solar cell. In fact, even approaching the Shockley-Quaisser-limit for a single-junction direct bandgap photo voltaic cell was reported to be within the reach of perovskite solar cells. [9,10] Thus, with the strong absorption of radiation in the solar spectrum, a low nonradiative carrier recombination rate and the intrinsic selforganization potential of perovskite compounds that renders them easy to fabricate by different methods ranging from wet chemistry to vapor deposition, the obvious question seems: why is the perovskite solar cell not yet on the market?Unfortunately, the perovskite material itself faces intrinsic problems concerning its stability against ultraviolet radiation and, specifically, concerning its limited service life time and rapid degradation in environments containing moisture. Additionally, for the prototypical methylammonium lead trihalide, the lead content naturally raises questions concerning environmental issues. Moreover, changing for a new material for producing solar cells or modules presents a high barrier in itself, as seen for the past 30 years of development of materials and approaches for energy harvesting that are alternative to Si-based technologies.Based on the properties of halide perovskite materials, on the environmental and boundary conditions given by the integration into a photovoltaic cell and on the requirements set by the producers of commercial devices, the following issues seem prevalent and shall be addressed in this article: -Thin film deposition is required for cost-efficient furbishing of tandem solar cells that can be combined with Si technologies. -The service life time and stability in natural environments including the presence of moisture need to be enhanced, particularly for thin films. -The production method needs to have scale-up potential.Halide perovskites in general and organometal-halide perovskites in particular have become an intensely researched topic due their excellent optical properties, cheap production costs, and easy fabrication procedures. A high absorption coefficient, paired with a direct bandgap and a wide variety of accessible deposition method, makes these perovskites an excellent materials class for use in a plethora of applications, ranging from solar cells to light-emitting diodes, and image sensors with architectures of varying length scales ranging from simple thin-film solid-state solar cells to highly ordered nanostructured solar cells and sensors. A downs...

Multi-principal-element alloys share a set of thermodynamic and structural parameters that, in their range of adopted values, correlate to the tendency of the alloys to assume a solid solution, whether as a crystalline or an amorphous phase. Based on empirical correlations, this work presents a computational method for the prediction of possible glass-forming compositions for a chosen alloys system as well as the calculation of their critical cooling rates. The obtained results compare well to experimental data for Pd-Ni-P, micro-alloyed Pd-Ni-P, Cu-Mg-Ca, and Cu-Zr-Ti. Furthermore, a random-number-generator-based algorithm is employed to explore glass-forming candidate alloys with a minimum critical cooling rate, reducing the number of datapoints necessary to find suitable glass-forming compositions. A comparison with experimental results for the quaternary Ti-Zr-Cu-Ni system shows a promising overlap of calculation and experiment, implying that it is a reasonable method to find candidates for glass-forming alloys with a sufficiently low critical cooling rate to allow the formation of bulk metallic glasses.