Non‐Local Electron‐Phonon Interaction in Naphthalene Diimide Derivatives, its Experimental Probe and Impact on Charge‐Carrier Mobility

Abstract

AbstractEfficient operation of organic electronic devices requires high charge‐carrier mobilities in their active layers, but only several organic semiconductors show confirmed charge‐carrier mobilities exceeding that of amorphous silicon (≈1 cm2 V−1 s−1). Charge transport in high‐mobility organic semiconductor crystals is considerably hindered by non‐local electron‐phonon interaction (NLEPI) transforming dynamic disorder induced by low‐frequency (LF) vibrations into fluctuations of charge transfer integrals. In this work, using two crystals of naphthalene diimide derivatives as an example, LF vibrational modes that strongly modulate the charge transfer integrals are computationally revealed. The importance of the discussed LF modes for limiting the charge‐carrier mobility is justified by analyzing the effect of the dynamic disorder on the charge‐carrier dynamics, estimating the charge‐carrier mobility in the two crystals, and observing quite a good agreement of the latter with the experimental values. Finally, it is shown that the contribution of various modes to the NLEPI correlates with their experimental Raman intensities. As a result, it is suggested that LF Raman spectroscopy can be used for experimental study of NLEPI, which can help with screening organic semiconductors showing high charge‐carrier mobility and promote rational design of such materials.