ИСТИНА

Organic semiconductor crystals (OSCs) show the highest charge-carrier mobility, which is a key for high performance organic electronic devices. Non-local electron-phonon interaction in OSCs is suggested to limit the charge transport.1 However, non-local electron-phonon interaction in OSCs is far from being well studied, and one of promising methods for probing it can be Raman spectroscopy.2,3 In this study, we establish a relationship between the non-local electron-phonon interaction in various charge-transport directions and anisotropic low-frequency (LF) Raman scattering in two organic semiconductors with relatively high electron mobility, naphthalene diimides (Fig.1): N,N'-Dicyclo-hexyl-naphthalene-1,8;4:5-dicarboximid (NDI_CHex) and N,N′-bis(hexyl)naphthalene diimide (NDI-Hex). We determine the contributions of various LF vibrational modes to the non-local electron-phonon interaction and show that they correlate with the corresponding Raman intensities, divided by frequency. We reveal computationally the LF vibrational modes that strongly modulate charge transfer integrals in different directions and show that this modulation can be assessed experimentally using low-frequency Raman spectroscopy (Fig.2). Importantly, the anisotropy of the Raman scattering correlates with the anisotropy of the non-local electron-phonon interaction, indicating that Raman spectroscopy can probe the latter in various charge transport directions. Our findings will be used to study the effect of the non-local electron-phonon coupling on the electron mobility in the crystals.