Anisotropic electron mobility studies on Cl2-NDI single crystals and the role of static and dynamic lattice deformations upon temperature variation

Abstract The anisotropic electron transport in the (001) plane of sublimation-grown Cl 2 -NDI (naphthalene di-imide) single crystals is analysed over a temperature range between 175 K and 300 K. Upon cooling fromroom temperature to 175 K the electron mobility along the direction of preferred transport monotonously in-creases 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 byinelastic scattering with accoustic phonons. However, as we will demonstrate, the experimental mobilitydata can be consistently described within the framework of an incoherent, hopping-type model based onLevich-Jortner rates and explicitly accounting for the impacts of thermally induced lattice effects and en-hanced electron-phonon interaction at elevated temperatures. Thus, in contrast to the general paradigm,the increase of mobility at lower temperatures proves to be a necessary but not sufficient criterion for aband-like motion of charge carriers.