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Comunicação em painel apresentada no E-MRS 2013 - Symposium B, To improve the efficiency of organic solar cells is necessary, for instance, to increase the open-circuit voltage or increase sun-light absorption by covering complementary regions of the solar spectrum. This can be achieved by using a donor-acceptor system composed of two polymers. The versatility of these materials has the advantage of enabling the control of morphology at nanoscale, and thus the design of an adequate interface to improve the device efficiency, using for instance nanoimprint lithography. However, proper control of the molecular organization of both polymers at polymer-polymer interface is difficult and strongly depends on the experimental conditions used. Polymer chains can present different conformations relative to the interface, creating different conjugated strand arrangements whose disorder degree can affect energy and charge transfer. Thus, understanding this effect is of utmost importance to improve the efficiency of excitonic solar cells. In this work we present a Monte Carlo model that uses a proper description of polymer-polymer interface nanomorpholy and considers the main physical processes that mediate excitons and charges dynamics. Our results show that the amount of charge extracted from the interface is sensible to polymer strand orientation and to the presence of the diffusive layer formed by the mixture of both polymers., Fundação para a Ciência e a Tecnologia (FCT)

Using a finite element approach the authors model the influence of enamel's microstructure and water distribution on the temperature and stress at the centre of the laser spot, for a CO2 laser working at 10.6 μm, with 0.35 μs pulse duration and subablative intensity. The authors found that the distribution of water in enamel significantly influences the stress generated at the end of one laser pulse: much lower (two orders of magnitude) stress values occur in models with homogeneously distributed water than in models with 0.27 vol.% water located in pores or 4 vol.% in layers. The amount of water in enamel has a strong influence on the stress distribution, but not on the maximum stress values reached. However, different water contents do not influence the temperature distribution in enamel. These results suggest that adequate modelling of the ablation mechanisms in enamel, as in other highly inhomogeneous materials, must include their structure at the mesoscopic scale., Comunidade Europeia (CE). Fundo Europeu de Desenvolvimento Regional (FEDER) - Programa Operacional "Ciência, Tecnologia, Inovação (POCTI) - POCTI/ESP/37944/2001., Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/4725/2001.

We have deposited semiconductor thin films by means of a home-made magnetron sputtering apparatus. Some physical parameters of the films have been determined, namely the thickness, the optical properties, the electrical resistivity and the crystalline structure.