Determinants of Electron Transport at Asymmetric Metal/Organic/Metal Contacts

Molecular diodes, based on a metal/molecule/metal architecture, offer an effective route to suppress short-channel effects and tunneling leakage in conventional electronic devices. Enhancing their performance critically relies on engineering asymmetric contacts to induce substantial interfacial barrier differences, yet identifying optimal metal/molecule combinations across vast chemical and structural spaces remains a major challenge. Here we perform a comprehensive computational screening of 126 molecular junctions, combining density functional theory with non-equilibrium Green’s function calculations, encompassing six electrode materials, six organic molecules, and dozens of asymmetric contact geometries. We introduced a predictive descriptor that captures the combined influence of Schottky barrier height and tunneling width on both current and rectification ratio, integrating thermal excitation and interfacial tunneling effects. Our model achieves an accuracy of up to 94%, outperforming conventional Schottky theory and the Fermi golden rule. Notably, the optimal configuration identified by our descriptor delivers a rectification ratio three times higher than the experimental benchmark. This framework is robust across systems with asymmetric electrodes, offering a generalizable approach for the rational design of high-performance molecular diodes.