Emergent Properties of an Organic Semiconductor Driven by its Molecular Chirality

TLDR

Chiral molecules, existing as mirror‑image pairs, represent a largely untapped symmetry property in organic electronics. The study employs crystal structure prediction—a rarely used computational technique for molecular materials—to link bulk packing differences to charge transport variations. OFETs fabricated from the helically chiral 1‑aza[6]helicene exhibit up to an 80‑fold variation in hole mobility, photophysics, and morphology depending on the chiral composition, demonstrating that chirality can serve as a powerful tuning parameter for device performance.

Abstract

Chiral molecules exist as pairs of nonsuperimposable mirror images; a fundamental symmetry property vastly underexplored in organic electronic devices. Here, we show that organic field-effect transistors (OFETs) made from the helically chiral molecule 1-aza[6]helicene can display up to an 80-fold difference in hole mobility, together with differences in thin-film photophysics and morphology, solely depending on whether a single handedness or a 1:1 mixture of left- and right-handed molecules is employed under analogous fabrication conditions. As the molecular properties of either mirror image isomer are identical, these changes must be a result of the different bulk packing induced by chiral composition. Such underlying structures are investigated using crystal structure prediction, a computational methodology rarely applied to molecular materials, and linked to the difference in charge transport. These results illustrate that chirality may be used as a key tuning parameter in future device applications.