Understanding Carrier Transport in Organic Semiconductors: Computation of Charge Mobility Considering Quantum Nuclear Tunneling and Delocalization Effects.

Despite great attention to the charge transport in organic semiconductors (OSC) over the last decades, the underlying mechanism is still controversial. After our theoretical position in 2009, the quantum nuclear tunneling effect has been proven by more and more experiments to play an essential role for charge transport in organic and polymeric materials. On the other hand, back in the 1970s, it was proposed that the nature of charge transport could be analyzed by the isotope effect, which, however, has not been confirmed either experimentally or theoretically. In this Perspective, we review the understanding of microscopic mechanisms on charge transport by using different transport mechanisms from hopping to band transport. Particularly, we point out that the isotope effect, which is absent in the semiclassical Marcus theory, should be negative for the localized charge transport with quantum nuclear tunneling. We conclude that the quantum nuclear tunneling effect dominates the charge transport in OSCs.