Investigation on two-dimensional band structures of trans-polyacetylene doped with n-type dopant

摘要

Highly oriented tram-polyacetylene (PA) doped with n-type or p-type dopants showed electrical anisotropy. EHMO/CO (crystalline orbital) quantum chemical methods were used to calculate the two-dimensional (2D) energy band structures of PA undoped and doped by n-type dopants (Li, Na, K). The band gaps (Eg) of undoped PA in directions parallel and perpendicular to the oriented direction were 1.195eV and 3.040eV, respectively, and those of doped PA decreased significantly. Based on the calculation results, we could successfully account for the changes of electrical anisotropy of PA from undoped state to doped form. The conductivity anisotropy ratio #sigma#_(||)/#sigma#_(^) decreased when PA was doped with n-type dopant, because the PA chains and the dopant showed a strong interchain coupling. The theoretical results for undoped and doped PA are in good agreement with the experiment.