  Using density-functional theory with the hybrid functional B3LYP, we
investigate the electronic properties of polymers with diketo-pyrrolo-pyrrole
(DPP) unit. We note that some of the polymers studied have LUCO energy similar
to the C70-PCBM, or even lower, making them promising candidates for electron
transport in organic photovoltaic devices. The homopolymer of DPP is predicted
to have a band gap around 1.2 eV and shows a good dispersion of the conduction
band.
