Van der Waals heterojunctions of two-dimensional atomic crystals are widely used to build functional devices due to their excellent optoelectronic properties, which are attracting more and more attention, and various methods have been developed to study their structure and properties. Here, density functional theory combined with the nonequilibrium Green’s function technique has been used to calculate the transport properties of graphene/WS₂ heterojunctions. It is observed that the formation of heterojunctions does not lead to the opening of the Dirac point of graphene. Instead, the respective band structures of both graphene and WS₂ are preserved. Therefore, the heterojunction follows a unique Ohm’s law at low bias voltages, despite the presence of a certain rotation angle between the two surfaces within the heterojunction. The transmission spectra, the density of states, and the transmission eigenstate are used to investigate the origin and mechanism of unique linear I–V characteristics. This study provides a theoretical framework for designing mixed-dimensional heterojunction nanoelectronic devices.

C₂N-ring-based molecular chains were designed at the molecular level and theoretically demonstrated to show distinctive and valuable electron transport properties that were superior to the parent carbonaceous system and other similar nanoribbon-based molecular chains. This new -type molecular chain presented an exponential attenuation of the conductance and electron transmission with the length. Essentially, the molecular chain retained the electron-resonant tunneling within 7 nm and the dominant transport orbital was the LUMO. Shorter molecular chains with stronger conductance anomalously possessed a larger tunnel barrier energy, attributing to the compensation of a much smaller HOMO–LUMO gap, and these two internal factors codetermined the transport capacity. Some influencing factors were also studied. In contrast to the common O impurity with a tiny effect on electron transmission of the C₂N rings chain, the common H impurity clearly improved it. When the temperature was less than 400 K, the electron transmission varied with temperature within a narrow range, and the structural disorder deriving from proper heating did not greatly modify the transmission possibility and the exponentially decreasing tendency with the length. In a non-equilibrium condition, the current increased overall with the bias but the growth rate varied with size. A valuable negative differential resistance (NDR) effect appeared in longer molecular chains with an even number of big carbon–nitrogen rings and strengthened with size. The emergence of such an effect originated from the reduction in transmission peaks. The conductance of longer molecular chains was enhanced with the voltage but the two shortest ones presented completely different trends. Applying the bias was demonstrated to be an effective way for C₂N-ring-based molecular chains to slow down the conductance decay constant and affect the transport regime. C₂N-ring-based molecular chains show a perfect application in tunneling diodes and controllable molecular devices.

Molecular rectifiers, as prototypical components of molecular electronics, present unique opportunities for pushing device miniaturization to its ultimate limits. Nevertheless, challenges including limited rectification ratios, insufficient robustness, and poor reproducibility impede their practical deployment. To make molecular rectifiers competitive with silicon‐based devices, it is important to understand the design principles and fabrication methods from both mechanistic and experimental perspectives. By considering the transport mechanisms, modulation strategies, fabrication and characterization techniques, and theoretical simulations, this review provides a comprehensive overview of molecular rectifiers. Representative examples of conceptually significant and high‐performance molecular rectifier systems are highlighted to illustrate the relationships between rectification mechanisms, molecular design strategies, and device realization. Building on these discussions, we present an outlook for current bottlenecks and future directions to guide the development of molecular rectifiers. This review aims to serve as both a conceptual framework and a technical reference for researchers working at the intersection of molecular electronics and nanoscale device engineering in the post‐CMOS era.

Molybdenum disulfide is more attractive and valuable at the molecular level due to its unique structure and exceptional properties. Here, new-type MoS₂-ring chains are constructed and theoretically investigated for relevant electronic properties influenced by the length of the chain and the bias. Different from traditional wires, our findings demonstrate that the conductance of such a new-type chain presents unusually non-exponential decay with the length of the chain, with a particularly anomalous length of seven rings, which shows stronger equilibrium conductance than a shorter four-ring chain. Multi-peaks of electron transmission and delocalized electronic states contribute such uniqueness. Mo atoms play a vital role in electron transport. Essentially, a narrower “HOMO-LUMO” (the two closest energy levels to the Fermi level of MoS₂-ring chain) gap compensates for the lower device density of states of new-type molybdenum disulfide-ring chains. The usual electronic structure of a seven-ring chain is derived from its slightly arched structure and mainly originates from interference, which is the resonance occurring between the electrodes. Noticeably, the bias could greatly enhance conductance, which could reach 1000 times more than the equilibrium conductance. At a certain bias, the conductance of a seven-ring chain even exceeds the shortest one- or two-ring chain. Furthermore, the threshold voltage (at which the maximum conductance appears) gradually decreases with the length of the chain and eventually remains at 0.7 V. The valuable negative differential resistance (NDR) effect could be found in such a molecular chain, which becomes more obvious as the length rises until the seven-ring chain reaches the peak. Our findings shed light on the relations between electronic properties and the length of a new-type molybdenum disulfide-ring chain, and provide support for such new-type chains in applications of innovative low-power and controllable electronics.