Structural, mechanical and optical properties of conjugated polymers under mechanical load and temperature annealing

International audienc

Structural, mechanical and optical properties of conjugated polymers under mechanical load and temperature annealing

International audienc

Structural, mechanical and optical properties of conjugated polymers on a stretchable substrate under mechanical load

International audienc

Photodegradation study of ITIC derivatives acceptors and the correlation with stability in organic solar cells.

International audienc

NFA molecules with an extended pi-conjugated core: synthesis, characterization, photovoltaic performances and stability analysis.

International audienc

A Complex Interrelationship between Temperature-Dependent Polyquaterthiophene (PQT) Structural and Electrical Properties

International audienceThe influence of annealing temperature on the structural and electrical properties of conjugated poly(dodecyl-quaterthiophene) (PQT-12) polymer films is exploited. The temperature induced changes of structural parameters are monitored by in situ grazing incident X-ray diffraction (GIXD) and the conductivity. They are complemented by studies of the dielectric properties using variable angle spectroscopic ellipsometry (VASE). An increase of the scattered intensity, the size of the crystalline domains, and the current response is observed for a first thermal cycle with stepwise heating up to 90 degrees C, which revealed two polymorphs with different degrees of interdigitation in PQT-12. Irreversible changes are observed for the second cycle with a higher thermal budget up to 140 degrees C and are connected with a transition from the highly ordered to powder-like disordered phase for the main PQT-12 form whereas the second polymorph with stronger interdigitation completely vanished. In agreement with these observations high-temperature VASE studies demonstrated a blue shift of the transitions with a reduction in the conjugation length caused by an increase in the twist and torsion of the backbone. Combined GIRD, VASE, and electrical characterizations show that PQT-12 exhibits a complex interplay between two polymorphs with a strong influence on the charge carrier transport depending on the thermal budget employed

A detailed stability study of non-fullerene acceptors and their use in high efficiency polymer solar cells.

International audienc

Synthesis, characterization, photovoltaic performances and stability analysis of new NFA molecules with an extended pi-conjugated core.

International audienc

A kinetic and thermodynamic understanding of O2 tolerance in [NiFe]-hydrogenases

In biology, rapid oxidation and evolution of H2 is catalyzed by metalloenzymes known as hydrogenases. These enzymes have unusual active sites, consisting of iron complexed by carbonyl, cyanide, and thiolate ligands, often together with nickel, and are typically inhibited or irreversibly damaged by O2. The Knallgas bacterium Ralstonia eutropha H16 (Re) uses H2 as an energy source with O2 as a terminal electron acceptor, and its membrane-bound uptake [NiFe]-hydrogenase (MBH) is an important example of an “O2-tolerant” hydrogenase. The mechanism of O2 tolerance of Re MBH has been probed by measuring H2 oxidation activity in the presence of O2 over a range of potential, pH and temperature, and comparing with the same dependencies for individual processes involved in the attack by O2 and subsequent reactivation of the active site. Most significantly, O2 tolerance increases with increasing temperature and decreasing potentials. These trends correlate with the trends observed for reactivation kinetics but not for H2 affinity or the kinetics of O2 attack. Clearly, the rate of recovery is a crucial factor. We present a kinetic and thermodynamic model to account for O2 tolerance in Re MBH that may be more widely applied to other [NiFe]-hydrogenases