Ultrafast Exciton Migration and Dissociation in π-Conjugated Polymers Driven by Local Nonuniform Electric Fields

Abstract

Experimental verification for ultrafast charge generations is a significant advancement in recent studies of polymer solar cells, but its underlying mechanism still remains unclear. In this paper, a new mechanism of ultrafast charge generation is proposed, where a local nonuniform electric field plays a vital role. We systematically simulate the exciton dissociation dynamics along a polymer chain with electric field linearly distributed. The polymer chain can be divided into two regions according to the exciton dissociation degree, i.e., complete dissociation region and partial dissociation region. In the former, a photogenerated exciton can dissociate directly and completely into free charges. In the latter, however, a photogenerated exciton first experiences an ultrafast migration process toward the complete dissociation region and then partially dissociates with fractional free charge generation. In most of our simulations, the exciton dissociation can take place within a time scale of 1 ps, contributi...