  The anisotropic electron transport in the (001) plane of sublimation-grown
Cl$_{2}$-NDI (naphthalene diimide) single crystals is analysed over a
temperature range between 175 K and 300 K. Upon cooling from room temperature
to 175 K the electron mobility along the direction of preferred transport
monotonously increases from 1.5 cm$^{2}$/Vs to 2.8 cm$^{2}$/Vs according to a
distinct temperature relation of $~T^{-1.3}$. At first glance, these
characteristics allude to a coherent, i.e. band-like charge carrier transport
predominantly governed by inelastic scattering with accoustic phonons. However,
as we will demonstrate, the experimental mobility data can be consistently
described within the framework of incoherent, hopping-type transport modeled by
Levich-Jortner rates, explicitly accounting for the inner and outer relaxation
energies related to thermally induced lattice effects and enhanced
electron-phonon interaction at elevated temperatures. Complementary
band-structure calculations yielding temperature dependent effective mass
tensors deviate stronger from experimentally observed spatially anisotropic
transport behavior. Thus, these results hint at the fact that by the particular
interplay of the transport energies the mobility of a given organic
semiconducting material might appear to be band-like in a certain temperature
regime even though the underlying charge carrier transport can be of
incoherent, hopping-type nature. Building on this description, we further
explore the role of the intermolecular electronic coupling and develop a
procedure to distinguish between its dependence on static and dynamic lattice
deformation upon temperature variation.
