Reverse polarization in charged π-conjugated oligomers by single-optical excitation

A doped electron or hole will exist in a self-trapping state even in a π-conjugated oligomer. It can be excited by absorbing photons. Two possible optical-excitation modes, which are respectively called low-energy excitation and high-energy excitation are demonstrated in this paper. It is found that the high-energy excitation will result in a reverse polarization of the molecule. The polarizability is calculated and it is obtained that the strength of the reverse polarization is dependent upon the conjugation-length of the molecule