Designing emissive conjugated polymers with small optical gaps: A step towards organic polymeric infrared lasers

We show that chemical modification of the trans-polyacetylene structure that involves substitution of the backbone hydrogen atoms with conjugated side groups leads to reduction of the backbone bond alternation as well as screening of the effective Coulomb interaction. Consequently, the optical gap of the substituted material is smaller than the parent polyene with the same backbone length, and the excited state ordering is conducive to efficient photoluminescence. In the ideal long chain limit, the design of organic polymeric infrared lasers thereby becomes possible.