Charge Transport in Aromatic Hydrocarbon Crystals

Abstract

Abstract The calculation of two-center transfer integrals (TIs) has been critically examined and closed form analytical expressions have been obtained for them. It has been found that the TI between similar molecules (0,0,0) and (l,m,n) [molecular center located at la+mb+nc] is not the same as that between (0,0,0) and (l,m,n). This necessitates a reformulation of the band theory of charge transport in organic semiconductors. The revised theory has been applied to a number of aromatic hydrocarbon crystals belonging to the space group P21/a (Z=2). In view of the Munn-Siebrand theory of charge transport in anthracene, an attempt has been made to predict the likely mechanism of charge transport (coherent or hopping) in various directions in these crystals. Effect of the molecular size on semiconduction has also been discussed.