Multiple Resonance Fluorophores as Potential High-Mobility Organic Semiconductors

Many organic electronic devices, especially organic field-effect transistors─basic elements of logic circuits, require organic semiconductors with high charge-carrier mobility. In this study, we computationally show that such high mobilities can be observed in multiple resonance (MR) organic fluorophores─a novel class of compounds that are widely studied for a very different purpose, namely, as narrow-band (color-pure) emitters in organic light-emitting diodes. Specifically, density functional theory (DFT) calculations reveal small reorganization energies for hole or electron transfer, which are needed for efficient charge transport within the widely used hopping model in many MR compounds. The effect of small changes in the molecular structure on reorganization energy is observed and explained. Finally, we show that crystals of MR compounds can have large transfer integrals, e.g., if the MR cores bear appropriate substituents. For one of such MR fluorophores with a known crystal structure, electron mobility exceeding 1 cm² V^-1 s^-1 is predicted within the hopping model, which typically underestimates the mobility. We anticipate that our findings will stimulate charge transport studies in MR fluorophores and eventually result in the experimental discovery of high-mobility materials based on these compounds.