Dehydrogenation-induced polarity flipping of charge carriers and conductance enhancement in nitrogen-containing heterocyclic molecule-anchored single-molecule junctions

Achieving high conductance and dual charge carriers in molecular junctions is essential for developing logical building blocks in molecular electronics. In this study, we investigated the electrical transport properties of nitrogen-containing heterocyclic molecule (N3C)-anchored single-molecule junctions using the nonequilibrium Green’s function based on density functional theory. Our findings reveal that dehydrogenation is an effective strategy for achieving two charge-carrier polarities and improving conductance. In particular, dehydrogenation changed the N3C anchor from an electron-rich to an electron-deficient state, reversing the direction of charge transfer and that of the associated interfacial dipole. Consequently, electrons were replaced by holes as the primary charge carriers. Additionally, the number of removed hydrogen atoms critically governs the charge-transport behavior of molecular junctions. When the anchor groups were connected by conjugated molecular bridges, p-type and n-type molecular junctions were produced by removing three and four hydrogen atoms, respectively, significantly increasing junction conductance in both cases. These findings demonstrate that nitrogen-containing heterocyclic molecules are promising anchor groups for achieving two charge-carrier polarities and enhancing conductance through dehydrogenation.