Phase dependence of hole mobilities in dibenzo-tetrathiafulvalene crystal: A first-principles study

The organic semiconductor dibenzo-tetrathiafulvalene (DBTTF) has presented different polymorphs in solid packing, but the structure-property relationship is little clarified in the literature which is important for the design of high-performance organic semiconductors. In this study, the charge transport in DBTTF crystals for the alpha phase and beta phase is investigated from the first-principles calculations and the Marcus charge transfer theory. The one-, two-and three-dimensional mobilities are obtained simultaneously from a set of identical trajectories with an improved random walk technique. It is found that the alpha-phase crystal presents a smaller three-dimensional mobility than that in the beta-phase crystal although the mobility is much large along the c axis in the alpha-phase crystal. This is attributed to that the electronic couplings are mainly confined within the c axis for the alpha-DBTTF while the electronic couplings are more uniform in the three-dimensional space for the beta-DBTTF which thus provides more transport pathways for the charge transport. As a result, the beta-DBTTF may have a larger potential for practical applications in organic electronics. (C) 2012 Elsevier B. V. All rights reserved.