Ion-Regulated ReversibleSwitching of Photocurrentsin Molecular Junctions

Abstract

Abstract The switching of photoinduced charge transport in large-area carbon-based molecular junctions incorporating tetraphenyl porphyrin (TPP) molecules has been observed by reversibly introducing hydrogen ions into the molecular layer. The TPP layer acts as an ionophoric layer for the hydrogen ions through the protonation of pyrrole rings. Deprotonation can be realized by introducing an organic base solution into the molecular layer. The polarity of photocurrents (PC) obtained from TPP junctions becomes negative relative to the bottom electrode when TPP molecules get protonated and come back to positive upon their deprotonation. This switching behavior of PC in a solid-state junction reveals a strong correlation between protonation dynamics and the PC response, underscoring the utilization of molecular devices as ion chemosensors. Our study elucidates the interplay between structural change due to electronic transitions and charge transport in molecular systems, providing a foundation for designing advanced molecular-electronic devices for next-generation applications.