Density-functional-based tight-binding calculation of excitons in conjugated polymers

The fundamental excitations and optical properties of four important conjugated polymers (trans-polyacetylene, polydiacetylene, poly-para-phenylene, and polyphenylenevinylene) are described within a method combining density-functional-based tight-binding and the Bethe-Salpeter equation. This non-self-consistent approach is computationally highly efficient and can potentially be applied to very complex structures. We find that both singlet and triplet excitons generally agree with measurements. Moreover, the calculated UV/visible optical spectra reliably reproduce location and polarization of most experimental resonances.