Electronic structure and energy band gap studies for poly(1,3-thienyl-squaraine) and its dianion

Poly(1,3-thienyl-squaraine) has been studied by means of semi-empirical and ab initio quantum theories. It has been found to have a very large electron affinity (>9 eV) and thus, would be unstable in the environment. The band gap of the polymer was found to be as low as 0.3–0.6 eV. A distinct transition from a zwitterionic to a quinoidal structure was observed in the progression of increasingly longer oligomers.