Sylvain Chambon

Description of the nanostructured morphology of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) by XRD, DSC and solid‐state NMR

PCBM or [6,6]‐phenyl‐C61‐butyric acid methyl ester is nowadays still one of the most successful electron acceptors for plastic bulk heterojunction (BHJ) photovoltaic devices. In this study, a set of complementary techniques, i.e. solid‐state NMR, XRD and DSC, is proposed as a fast and sensitive tool to screen the morphology of PCBM specimens with different preparation histories. Based on proton NMR relaxation decay time values, an interval can be derived that situates the average crystal dimensions and which can further be refined on the basis of XRD patterns and DSC thermograms. Copyright

Synthesis, 1H and 13C NMR assignment and electrochemical properties of novel thiophene–thiazolothiazole oligomers and polymers

Novel hexyl‐substituted bisthiophene compounds containing a thiazolothiazole(5,4‐d) unit have been explored. The molecules are soluble in common organic solvents, which would enhance their chance of possible integration in printable electronics. Synthesis and complete elucidation of the chemical structures by detailed 1D/2D NMR spectroscopy are described. This provides interesting input for chemical shift prediction software, because few experimental data on this type of compounds are available. Furthermore, the potential n‐type character of these derivatives is verified using electrochemical measurements. In addition, the low‐bandgap character of conjugated polymers containing the thiazolothiazole unit is demonstrated by performing an electropolymerization. Copyright

Impact of light on organic solar cells: evolution of the chemical structure, morphology, and photophysical properties of the active layer

Organic photovoltaic represents an emerging technology thanks to its ability to give flexible, light weight and large-area devices, with low production cost by simple solution process or printing technologies. But these devices are known to exhibit low resistance to the combined action of sunlight, oxygen and water. This paper is focused on the behaviour of the active layer of the devices under illumination in the presence and absence of oxygen. The monitoring of the evolution of the chemical structure of MDMO-PPV submitted to accelerated artificial ageing permitted the elucidation of the mechanisms by which the polymer degrades. Extrapolation of the data to natural ageing suggested that, if well protected from oxygen (encapsulation), MDMO-PPV:PCBM based active layer is photochemically stable for several years in use conditions. In addition the charge transfer between the two materials was observed to remain efficient under exposure. The study of P3HT:PCBM blends allowed to point out the Achilles heel of P3HT towards the impact of light. In addition, P3HT:PCBM blends were shown to be much more stable under illumination than MDMO:PCBM blends. Preliminary results devoted to the AFM monitoring of the morphological modifications of P3HT:PCBM blends under the impact of light are also reported.