Impact of Fluoroalkylation on the n-Type Charge Transport of Two Naphthodithiophene Diimide Derivatives

In this work, we investigate two recently synthesized naphthodithiophene diimide (NDTI) derivatives featuring promising n-type charge transport properties. We analyze the charge transport pathways and model charge mobility with the non-adiabatic hopping mechanism using the Marcus-Levich-Jortner rate constant formulation, highlighting the role of fluoroalkylated substitution in alpha (alpha-NDTI) and at the imide nitrogen (N-NDTI) position. In contrast with the experimental results, similar charge mobilities are computed for the two derivatives. However, while alpha-NDTI displays remarkably anisotropic mobilities with an almost one-dimensional directionality, N-NDTI sustains a more isotropic charge percolation pattern. We propose that the strong anisotropic charge transport character of alpha-NDTI is responsible for the modest measured charge mobility. In addition, when the role of thermally induced transfer integral fluctuations is investigated, the computed electron-phonon couplings for intermolecular sliding modes indicate that dynamic disorder effects are also more detrimental for the charge transport of alpha-NDTI than N-NDTI. The lower observed mobility of alpha-NDTI is therefore rationalized in terms of a prominent anisotropic character of the charge percolation pathways, with the additional contribution of dynamic disorder effects.

Automated summary

The study investigated the charge transport properties of two NDTI derivatives, revealing that alpha-NDTI exhibits strong anisotropic characteristics while N-NDTI is more isotropic. The computed electron-phonon couplings suggest that dynamic disorder effects have a greater detrimental impact on the charge transport of alpha-NDTI compared to N-NDTI, leading to lower observed mobility for alpha-NDTI.