New benzothiadiazole-based dyes are synthesized, characterized and used for the fabrication of robust and efficient solar cells and mini-modules.

International audienceA series of new bipyrimidine-based chromophores have been prepared presenting alkoxystyryl donor groups carrying aliphatic chains in the 3,4, 3,5 or 3,4,5 positions, connected to electron-accepting 2,2′-bipyrimidine cores. Their linear and nonlinear optical properties were investigated as well as their mesomorphic properties by various techniques (light-transmission measurements, polarized-light optical microscopy, and differential scanning calorimetry measurements). Only two derivatives, BPM-3,4-C12 and BPM-3,4-C16, were found to exhibit liquid-crystalline behavior with the formation of lamella-columnar phases and/or hexagonal columnar phases over large temperature ranges. Small-angle X-ray scattering analysis allowed proposing a stacking model inside the mesophase in which the molecules are interdigitated alternatively along their long axis and their short axis to form columns. Dielectric measurements were performed as a function of the temperature, showing the centrosymmetric nature of the mesophases. Large quadratic hyperpolarizabilities have been measured for the individual mesogens in solution by using hyper-Rayleigh scattering. These chromophores exhibit also cubic nonlinear optical properties, revealing relatively large two-photon absorption cross sections. The nonlinear optical properties in the liquid crystalline state of compounds BPM-3,4-C12 and BPM-3,4-C16 have been studied by wide-field second-harmonic generation and two-photon fluorescence microscopy, confirming centrosymmetry for these achiral mesogens and the excellent third-order nonlinearity for multiphoton imaging

We report on the use of an alkoxyamine (AA) for fabrication of functional micropatterns with complex structures by UV mask lithography. The living character of the polymer surface and the vertical spatial control of the repolymerization reaction from few tens of nanometers to few micrometers were demonstrated. The impact of the main parameters governing the controlled polymerization and the reinitiation process activated by light or heat was investigated. Micropatterning is shown to be a powerful method to investigate the physicochemical molecular phenomena. It is possible to control the polymer microstructure thickness from few tens of nanometers to few micrometers. In the last section, some applications are provided showing the potential of the AA for generating covalently bonded hydrophilic/hydrophobic micropatterns or luminescent surfaces. This demonstrates the high versatility and interest of this route.

Paper published as part of the special topic on Advanced Thermoelectrics Note: This paper is part of the special topic on Advanced Thermoelectrics.

We unraveled the role of alkyl substituents, usually employed as solubilizing groups for organic sensitizers, in the performances and the stability of photovoltaic devices.

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International audienceAmong all n-type metal oxide semiconductors that can be used in solar cells as photoanode, ZnO is one of the most appealing aEternatives to the ubiquitous TiO2. This material offers some potentially favourable characteristics with respect to TiO2, such as higher eEectron mobility in the bulk and a rich variety of nanostructures. However, ZnO has certain drawbacks as photoanode material for example, a poor chemical stability and a slower charge separation process at the ZnO interface that reduces the eEectron injection rate. Therefore, in the case of dye-sensitized solar cells, the search of new dyes with a higher Eight harvesting efficiency and specifically designed to bind to ZnO can be considered as a possible strategy to improve performance in systems characterized by a Low eEectron injection rate. In this work the optical eEectrochemical and photovoltaic properties of a family of purely organic sensitizers with various anchoring groups have been investigated and compared with the most commonly used ruthenium dye N719. In particuar, we have shown that the structurally simple organic dye coded RK1 is an excellent sensitizer for ZnO photoanodes. Thanks to this molecule, the energy conversion efficiency under standard conditions (1 sun AM 1.5 illumination) empEoying ZnO-based photoanodes reached 3.7%, which is more than two times higher than obtained with the N719 dye studied under the same conditions

The functionalization by different coupling agents enabled to modify the properties of the surface of CrSi2 nanocrystallites.