Switchable topological polar states in epitaxial BaTiO nanoislands on silicon.

A fascinating aspect of nanoscale ferroelectric materials is the emergence of topological polar textures, which include various complex and stable polarization configurations. The manipulation of such topological textures through external stimuli like electric fields holds promise for advanced nanoelectronics applications. There are, however, several challenges to reach potential applications, among which reliably creating and controlling these textures at the nanoscale on silicon, and with lead-free compounds.

Chemical Interaction at the MoO/CHNHPbICl Interface.

The limited long-term stability of metal halide perovskite-based solar cells is a bottleneck in their drive toward widespread commercial adaptation. The organic hole-transport materials (HTMs) have been implicated in the degradation, and metal oxide layers are proposed as alternatives. One of the most prominent metal oxide HTM in organic photovoltaics is MoO.

Waveguide effect enhancement of local photocurrent in hybrid organic/inorganic solar cells.

The local efficiency of hybrid ZnO-nanorods/C/ZnPc:C/MoO/Ag solar cells, with different nanorods length has been investigated by scanning near-field optical microscopy. Simultaneous spatially resolved measurements of topography and photocurrent suggest a waveguide effect enhancement of the local photocurrent. This interpretation is supported by finite element method simulations of the light propagation in the solar cell.

The control of the electronic structure of dinuclear copper complexes of redox-active tetrakisguanidine ligands by the environment.

The electronic structures of dinuclear copper complexes of the general formula [GFA(CuX)], where X = Br or Cl and GFA denotes a redox-active bridging Guanidino-Functionalized Aromatic ligand, were analysed and compared. The diamagnetic complexes [GFA(CuBr)] can all be described as dinuclear Cu complexes with bridging GFA dicationic ligand units exhibiting a [Cu-GFA-Cu] electronic structure. The electronic structure prevails in the solid state and in all applicable organic solvents.

A Valence Tautomeric Dinuclear Copper Tetrakisguanidine Complex.

We report on the first valence tautomeric dinuclear copper complex, featuring 2,3,5,6-tetrakis(tetramethylguanidino)pyridine as a bridging redox-active GFA (guanidino-functionalized aromatic) ligand. The preferred electronic structure of the complex is massively influenced by the environment. In the solid state and in nonpolar solvents a paramagnetic, dinuclear Cu(II) complex with a neutral GFA ligand is present.

Thermochromism of Cu(I) Tetrakisguanidine Complexes: Reversible Activation of Metal-to-Ligand Charge-Transfer Bands.

Tetranuclear, intensely blue-coloured Cu(I) complexes were synthesised in which two Cu2 X3 (-) units (X=Br or I) are bridged by a dicationic GFA (guanidino-functionalised aromatic) ligand. The UV/Vis spectra show a large metal-to-ligand charge-transfer (MLCT) band around 638 nm. The tetranuclear "low-temperature" complexes are in a temperature-dependent equilibrium with dinuclear Cu(I) "high-temperature" complexes, which result from the reversible elimination of two CuX groups.

Redox-controlled hydrogen bonding: turning a superbase into a strong hydrogen-bond donor.

Herein the synthesis, structures and properties of hydrogen-bonded aggregates involving redox-active guanidine superbases are reported. Reversible hydrogen bonding is switched on by oxidation of the hydrogen-donor unit, and leads to formation of aggregates in which the hydrogen-bond donor unit is sandwiched by two hydrogen-bond acceptor units. Further oxidation (of the acceptor units) leads again to deaggregation.