Ion-Assisted Resonant Injection and Charge Storage in Carbon-Based Molecular Junctions

Resonant injection and resulting charge storage were examined in a large-area carbon/tetraphenylporphyrin(TPP)/LiF/carbon junction, where the LiF layer provides mobile ions in acetonitrile (ACN) vapor. Resonant electron transfer into TPP molecules occurs at <+1 V in the presence of mobile ions, enabled by ionic screening of the carbon electrode. Injection of holes, i.e. formation of the TPP radical cation, inside the junction was monitored by in situ photocurrent measurements. Following the injection, despite the lack of a redox counter-reaction or conventional electrolyte, persistent faradaic current peaks dominate the IV cycle of the junction (±2 V) in ACN vapor, enhancing the reversible charge storage by a factor of 78 compared to that in vacuum.