Bound excitons and optical properties of bulk trans-polyacetylene -: art. no. 193204

Using the GW approximation and solving the Bethe-Salpeter equation, we performed a first-principles study of the electronic configuration and linear optical response of crystalline polyacetylene (-C2H2-), one of the simplest conjugated polymers. The optical spectrum is dominated by a low-energy bound exciton, denoted 1(1)B(u). A "dark" interchain bound exciton is found to be almost degenerate with state 1(1)B(u). Interchain interactions are found to be responsible for a reduction of both the electronic energy gap and the binding energy of bound excitons, compared to previous single-chain calculation. The optical absorption spectrum is compared to measurements performed on thin films of oriented polyacetylene.