Jean-Paul Parneix

Temperature-dependent electroluminescence spectra of poly(phenylene-vinylene) derivatives-based polymer light-emitting diodes

This study reports on the temperature dependence of electroluminescence spectra of polymer light-emitting diodes based on poly[2,5-bis(3′,7′-dimethyl-octyloxy)1,4-phenylene-vinylene] and poly[2-methoxy-5(2′-ethyl-hexoxy)1,4-phenylene-vinylene]. Temperatures from 80to350K were investigated. A vibronic structure of electroluminescence spectra has been observed. The electroluminescence spectra were then fitted with multiple Gaussian peaks. A blueshift of the zero-phonon line has been reported with increasing temperature, while the full width at half maximum of electroluminescence peaks increased. We propose a model of thermally activated statistic occupation of excited states to fully describe the experimental data. Finally, these electroluminescence changes with temperature only imply a negligible variation of the emitted color.

Solution Processing of Polymer Photovoltaic Solar Cells in Air or Under Inert Atmosphere

Polymer photovoltaic solar cells based on a blend of poly(3-hexylthiophene) (P3HT) blended with [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) have been manufactured in air under ambient conditions and under inert atmosphere in a nitrogen-filled glovebox (O2 and H2O < 0.1 ppm). The solution processing of the active layer, in air or nitrogen, affects the performances of the resulting devices. However, the air processed devices shows reasonable efficiencies implying that somehow large area processing of such materials using machinery in air under ambient conditions is realistic for the high throughput production of polymeric solar modules.

Modeling and measurement of the electromagnetic responses of stacked volumetric gratings

The last few years have seen a growing interest in the analysis of heterogeneous materials. These investigations lead to many applications as for example the development of absorbing materials or frequency selective surfaces. To analyse these structures we developed a method based on the domain integral representation of the fields. In a way to minimize the domain of integration, we considered the case of stacked gratings embedded or not in a slab. Then by using the Floquets theorem, the domain of integration is limited to the reference element of each grating. An interesting application of such gratings is photonic band-gap materials. Indeed, these structures present a high reflection coefficient over a broad frequency bandwidth. Various photonic band-gap materials have been realized with metallic and dielectric gratings. Bistatic free-space measurements, performed from a 4 Ghz to 18 Ghz are compared to the simulations. The results obtained show a good agreement between the reflected field obtained with the model and the measurements. Since the localization of the frequency bandwidth is well evaluated we can use this model to build reflectors to antennas for example. An other important application of such structures is absorbing materials. This aspect will be presented as well.