Localized Trions as Metastable Charged States in Conjugated Polymers

Abstract

We have shown that a charged trion consisting of two on-chain polarons of the same sign and a trapped polaron of the opposite sign can be metastable with respect to both dissociation and recombination. A trion can be created upon fusion of a free polaron with a neutral pair, which eliminates a high Coulomb potential barrier for fusion of two charge carriers into a bipolaron. We argue that trions can be created by photoexcitation of a conjugated polymer, in which illumination creates a high density of geminate pairs. Since the metastable trion is anchored by a deep-trapped charge, it is immobile and can be considered as a coulombically trapped bipolaron, although the last may not exist as a free particle. We employ the concept of localized trions in order to explain the reversible photoinduced fatigue of thermally stimulated luminescence in films of poly[methyl(phenyl)silylene].

Keywords:

• bias-stress effect in organic FET
• charge trapping
• metastability
• thermally stimulated luminescence

Acknowledgments

The work was supported by the European Commission through the NAIMO Integrated Project (FP6-NMP IP 500355), by the National Academy of Science of Ukraine under the program of fundamental research “Nanostructured systems, nanomaterials, nanotechnology” and by the Ministry of Education, Youth and Sports of the Czech Republic through the COST Project No. 1041/2006-32.

Notes

†Deceased.