Ab-initio study of Coulomb-correlated optical properties in conjugated polymers

The spatial extension and binding energy of excitons in semiconducting conj ugated polymers are still the subject of a great debate. We address this pr oblem through first-principles calculations (within DFT-LDA, plane-waves an d ab-initio pseudopotentials), which allow to include electron-hole correla tion effects in a fully three-dimensional approach through the density-matr ix formalism. We show results for the correlated optical spectrum and the e xciton wavefunctions of single-chain poly(para)phenylene-vinylene (PPV), th at support the picture of a strongly bound anisotropic exciton localized ov er similar to 4-5 monomers.