Exploring the Interplay of Lattice Dynamics and Charge Transport in Organic Semiconductors: Progress Toward Rational Phonon Engineering.

Organic semiconductors (OSCs) have garnered significant attention due to their potential use in flexible, lightweight, and cost-effective electronic devices. Despite their promise, the assembly of organic molecules into the condensed phase promotes a diverse set of lattice dynamics that introduce a detrimental modulation in the intermolecular electronic structure-termed dynamic disorder-that results in charge carrier mobilities that are orders of magnitude lower than inorganic semiconductors. This dynamic disorder is generally associated with low-frequency phonons, yet whether a small subset of modes or a broad range of phonons  drives dynamic disorder remains contested. Resolving this debate is critical for defining how targeted phonon engineering could practically improve OSC performance. In this review, we explore progress toward uncovering the interplay between lattice dynamics and charge transport in OSCs, focusing on the critical role of thermally activated phonons. We describe the powerful insight that mode-resolved analyses of electron-phonon interactions lends toward the rational design of new materials. We highlight recent efforts to achieve this, showcasing proposed strategies to mitigate dynamic disorder through molecular and crystal design. This work offers an overview of the insight gained toward understanding the fundamental mechanisms governing charge transport in OSCs and outlines pathways for enhancing performance via targeted manipulation of interatomic/intermolecular interactions and resulting phonon modes.