Polarized emission from stretched PPV films viewed at the molecular level.
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2015
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We present a study on the photoluminescence (PL) of thin films of poly-(p-phenylene vinylene) (PPV),
non-stretched and uniaxially stretched. The experimental study was carried out using linear polarized
light as the excitation beam, oriented either parallel or perpendicular to the stretch axis (S). The results
showed that when the excitation light source has polarization perpendicularly oriented to the stretch
direction, the emitted PL presents maximum intensity in the orientation S, and a minimum in the
direction orthogonal to S. In order to understand this interesting phenomenon, we employ theoretical
simulations at the atomistic level. We use classical molecular dynamics to simulate amorphous PPV
films, non-stretched and stretched, from which we find a tendency of overall alignment of PV units to S,
and of local clustering in herring-bone and p-stacking partial symmetries. Our study of optical activity of
these kinds of clusters, performed through a quantum semi-empirical method, allows us to explain this
polarization conversion behavior, and indicates the possibility of using underivatized PPV as the active
layer for polarized electroluminescent devices.
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RAMOS, R. et al. Polarized emission from stretched PPV films viewed at the molecular level. Physical Chemistry Chemical Physics, v. 17, p. 20530-20536, 2015. Disponível em: <http://pubs.rsc.org/En/content/articlepdf/2015/cp/c5cp02513c>. Acesso em: 23 jan. 2017.