Labex (Sweden)

“The Alpine community must not forget the refugees”Francesco Pastorelli (alpMedia, 2018) The “point of view” of Francesco Pastorelli, Director of CIPRA Italy, was published on the alpMedia journal on March 2018: “While the Alpine regions are working on a unified Alps via the European Strategy for the Alps (Eusalp), the nation states are fencing themselves off. Where is the spirit of solidarity of the European Union? Can we, within the framework of the Alpine Convention, continue to address is...

The first combined theoretical and photovoltaic characterization of both homoleptic and heteroleptic Fe(ii)-carbene sensitized photoanodes in working dye sensitized solar cells (DSSCs) has been performed. Three new heteroleptic Fe(ii)-NHC dye sensitizers have been synthesized, characterized and tested. Despite an improved interfacial charge separation in comparison to the homoleptic compounds, the heteroleptic complexes did not show boosted photovoltaic performances. The ab initio quantitative analysis of the interfacial electron and hole transfers and the measured photovoltaic data clearly evidenced fast recombination reactions for heteroleptics, even associated with un unfavorable directional electron flow, and hence slower injection rates, in the case of homoleptics. Notably, quantum mechanics calculations revealed that deprotonation of the not anchored carboxylic function in the homoleptic complex can effectively accelerate the electron injection rate and completely suppress the electron recombination to the oxidized dye. This result suggests that introduction of strong electron-donating substituents on the not-anchored carbene ligand in heteroleptic complexes, in such a way of mimicking the electronic effects of the carboxylate functionality, should yield markedly improved interfacial charge generation properties. The present results, providing for the first time a detailed understanding of the interfacial electron transfers and photovoltaic characterization in Fe(ii)-carbene sensitized solar cells, open the way to a rational molecular engineering of efficient iron-based dyes for photoelectrochemical applications.

Shape optimization typically involves geometries characterized by several dozen design variables and a possibly high number of explicit/implicit constraints restricting the design space to admissible shapes. In this work, instead of working with parametrized CAD models, the idea is to interpolate between admissible instances of finite element/CFD meshes. We show that a properly chosen surrogate model can replace the numerous geometry-based design variables with a more compact set permitting a global understanding of the admissible shapes spanning the design domain, thus reducing the size of the optimization problem. To this end, we present a two-level mesh parametrization approach for the design domain geometry based on Diffuse Approximation in a properly chosen locally linearized space, and replace the geometry-based variables with the smallest set of variables needed to represent a manifold of admissible shapes for a chosen precision. We demonstrate this approach in the problem of designing the section of an A/C duct to maximize the permeability evaluated using CFD.