Charge transport along phenylenevinylene molecular wires

Abstract

A model to calculate the mobility of charges along molecular wires is presented. The model is based on the tight-binding approximation and combines a quantum mechanical description of the charge with a classical description of the structural degrees of freedom. It is demonstrated that the average mobility of charge carriers along molecular wires can be obtained by time-propagation of states, which are initially localised. The model is used to calculate the mobility of charges along poly-phenylenevinylene (PPV) chains with varying number of alkoxy side chains. Effects of the torsional motion of the phenyl rings on the mobility are taken into account. The results show that derivatives of PPVs can act equally well as electron and hole conductors. Experimental mobility data on di-alkoxy substituted PPV can be reproduced with the present model provided the effects of structural defects along the polymer chains are taken into account. According to the calculations, intra-chain hole and electron mobilities of the order of 100 cm2/Vs can be obtained for defect-free PPV chains.