Pentacene hopping mobility

The regime of intermolecular interaction energies shown in Figure 2.10 most probably spans the value of 7 relevant for pentacene crystals [19]. The low-field mobility can be directly deduced fi om the calculated polaron velocity. These results set an upper limit on the mobility since the simulations are performed for a defect fi-ee system. Possibly, the mobility could change sKghtly if we would go from a ID to 2D system. The fact that the polaron is rather delocalized even in the case of /= 50 meV indicates that the pure nonadiabatic (or hopping) treatment, such as that given by the Marcus theory [16] or the... 

Before a proper evaluation of the matrix elements was available and before the new experimental results on ultrapure pentacene and rubrene were realized, Kenkre et al. [130] were able to fit the classical results of Karl [131] on the temperature dependence of the anisotropic mobility of pentacene with a three dimensional Holstein model. It now seems clear that the fitted parameters are not compatible with the computations (the hopping integral is about two orders of magnitude smaller than the typical value) and that the Holstein Hamiltonian is insufficient to capture the physics of organic semiconductors. 

---