Future atmospheric conditions must be taken into account in evaluating the long-term effectiveness of energy supply from renewable sources. Now, Sonia Jerez and collaborators have explored the ...potential effects of climate change on the electricity produced by photovoltaic installations in Europe. They considered a set of scenarios describing the future evolution of greenhouse gas concentrations in the atmosphere,solar irradiance, surface air temperatureand surface wind velocity. Variations ofsolar power production were calculated based on the impact that these atmospheric parameters have on the operating temperature of the photovoltaic panels.
Methylammonium cations play a key role in determining the crystal structure and the photovoltaic behaviour of organicinorganic perovskite films. The orientation and the dynamics of their permanent ...dipole moment affect the dielectric response of these materials and may contribute to the hysteretic response observed in perovskite solar cells. Using ultrafast polarization-resolved 2D infrared vibrational spectroscopy, Artem Bakulinand colleagues now study the motion ofthese organic cations within the inorganic sublattice of methylammonium lead triiodide perovskites synthesized with three different approaches. In all samples, the time-dependent anisotropy of the measured signal reveals two distinct cationic motions on 300-fs and 3-ps timescales. Molecular dynamics simulations are used to assign such contributions to, respectively, wobbling-in-a-cone motion and 90 reorientations of the organic molecules aligned to the main axes of the inorganic lattice. The researchers suggest that such insight may shed light on the contribution of the dielectric behaviour to the photophysical properties of these materials. LM
Conversion of thermal or electrical stimuli into mechanical motion can be controlledat the molecular scale; this has been previously demonstrated, among others,by Gianaurelio Cuniberti and ...colleagues, who synthesized windmill-shaped supramolecular nanostructures that move on a gold surface when stimulated by a voltage pulse applied through the tip of a scanning tunnelling microscope. Now, this group shows that such nanostructures can also act as molecular electromechanical systems; guided by controlled electrical pulses, they can pick up and transport single gold atoms, gold dimers and small molecules adsorbed on the surface. The researchers verified that the motion is neither due to a mechanical interactionof the tip with the nanostructures nor to direct electrical driving of the transported particles. Depending on the sign of the applied voltage, the loads can be rotated by a small angle or translated by a few ngstrms, demonstrating a fine control that may be useful for the realization of more complex molecular machines. LM
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