Re-excited states of solitons and polarons in conjugated polymers

π-Conjugated polymers have become an important class of materials for electronic devices. It was suggested recently that a charge flipping of spin carrier will take place when a charged polaron is re-excited by a photon. A possible photo-control valve or switch can be designed from this phenomenon. In the framework of the tight-binding approximation we studied the re-exciting process both in degenerate and non-degenerate polymers and checked all the possible re-excited states.