  In this work, we study the light absorption properties of a novel molecule
(BTTzR) and its more extended derivatives, which hold promise as electron-donor
material in organic solar cells. By employing density functional theory, we
observe that the addition of two and three oligothiophene chains to the central
benzene ring of the benzo[1,2-b:4,5-b']dithiophene (BDT-T) leads to both a
red-shift of the existing peaks and, interestingly, to the development of new
blue-shifted features, an effect that can certainly increase the
panchromaticity of the molecule in the visible spectral range.
