Photoinduced polarization inversion of excitons in conjugated polymer films

The study shows that, in a conjugated polymer, there exists a novel photo-induced phenomenon: A photo-induced polarization inversion, when a single-exciton is photoexcited and becomes a bi-exciton. The reason is that, in a conjugated polymer, a single-exciton displays normal polarization, whereas a bi-exciton exhibits negative polarization. The physical significance of negative polarization is explored. Photo-induced polarization inversion is an ultrafast switching process, which could be used to make photo-induced ultrafast switch devices.