Toward Accurate Prediction of Ion Mobility in Organic Semiconductors by Atomistic Simulation

초록

A multiscale scheme (MLMS: Multi-Level Multi -Scale) to predict the ion mobility (mu) of amorphous organic semiconductors is proposed, which was successfully applied to the hole mobility predictions of 14 organic systems. An inverse relationship between mu and reorganization energy is observed due to local polaronic distortions. Another moderate inverse correlation between mu and distribution of site energy change exists, representing the effects of geometric flexibility. The former and the latter represent the intramolecular and intermolecular geometric effects, respectively. In addition, a linear correlation between transfer coupling and mu is observed, showing the importance of orbital overlaps between monomers. Especially, the highest hole mobility of C6-2TTN is due to its large transfer coupling. On the other hand, another high hole mobility of CBP turned out to come from the high first neighbor density (rho FND) of its first self-solvation, emphasizing the proper description of amorphous structural configurations with a sufficiently large number of monomers. In general, systems with either unusually high transfer coupling or high first neighbor density can potentially have high mu regardless of geometric effects. Especially, the newly suggested design parameter, rho FND, is pointing to a new direction as opposed to the traditional pi-conjugation strategy.

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