Supramolecular Structure Enabled Photo-Responsive Charge Transport in Porphyrin-Based Junctions

Supramolecular electronics offers a valuable opportunity to fabricate functional devices with tunable charge transport (CT) behaviors. Their diverse and non-covalent structures allow for precise modulation of CT with external stimuli. Despite their potential, achieving effective CT modulation in supramolecules through external stimuli remains challenging due to a lack of rigid systems with a predictable response to such stimuli. To address this challenge, we explore the use of porphyrin-based supramolecular structures and their CT responses to light illumination. By incorporating rigid ligands to increase the spatial distance between two porphyrin units, we diminish their interactions, fabricating porphyrin-contained cages that exhibit a higher efficiency of electron-hole pair separation compared to the monomer in solid state. Leveraging this advantage, a more effective photo-responsive CT is achieved for cages in solid-state junctions compared to that of monomers. The current through cage junctions reduces upon illumination. Theoretical calculations indicate that the reduction in conductivity arises from an increased energy offset between the molecule and electrode under light irradiation. Moreover, the photo-responsive CT can be finely tuned by adjusting the metal ion coordinated within the porphyrin and the distance between the cage and the electrode. This research paves a new way for developing supramolecular optoelectronic devices.