Microscopic Nature of Carrier Transport in Photoconductive Polymers

Abstract

We tried to clarify the mechanism of hopping charge transport in molecularly doped polymers (MDP's) by means of time-of-fight photoconductivity measurements and molecular orbital calculations. It was found that the magnitude of the hole drift mobility in binary solid solution MDP's is closely related to electronic properties of dopant molecules. Diagonal and off-diagonal disorders dominating the general feature of charge transport are mainly caused by the spatially in homogeneous distribution of charge on dopant molecules. With an increase in the drift mobility, the structural change between neutral and cation forms of a doped molecule, the polaron effect, as well as diorder control the hopping rate. The delocalization of charge in both neutral and cation forms determines the degree of disorder and is important for designing molecules having high mobility. Microscopic considerations based on molecular orbital calculations are growing need for the understanding of charge transport in MDP's.