The π-π stacking is a well-recognized intermolecular interaction that is responsible for the construction of electron hopping channels in numerous conducting frameworks/aggregates. However, the exact role of π-to-π channels within typical single crystalline organic semiconductors remains unclear as the orientations of these molecules are diverse, and their control usually requires additional side chain groups that misrepresent the intrinsic properties of the original semiconducting molecules. Therefore, the construction of conduction channels with intrinsic π-π stacking in the molecule-based device is crucial for the utilization of their unique transport characteristics and understanding of the transport mechanism. To this end, we present a molecular intercalation strategy that integrates two-dimensional layered materials with functional organic semiconductor molecules for functional molecule-based electronics. Various organic semiconductor molecules can be effectively intercalated into the van der Waals gaps of semi-metallic TaS₂ with π-π stacking configuration and controlled intercalant content. Our results show that the vertical charge transport in the stacking direction shows a tunneling-dominated mechanism that strongly depends on the molecular structures. Furthermore, we demonstrated a new type of molecule-based vertical transistor in which TaS₂ and π-π stacked organic molecules function as the electrical contact and the active channel, respectively. On/off ratios as high as 447 are achieved under electrostatic modulation in ionic liquid, comparable to the current state-of-the-art molecular transistors. Our study provides an ideal platform for probing intrinsic charge transport across π-π stacked conjugated molecules and also a feasible approach for the construction of high-performance molecule-based electronic devices.

Van der Waals heterostructures (vdWHs) are showing considerable potential in both fundamental exploration and practical applications. Built upon the synthetic successes of (two-dimensional) 2D materials, several synthetic strategies of vdWHs have been developed, allowing the convenient fabrication of diverse vdWHs with decent controllability, quality, and scalability. This review first summarizes the current state of the art in synthetic strategies of vdWHs, including physical combination, deposition, solvothermal synthesis, and synchronous evolution. Then three major applications and their representative vdWH devices have been reviewed, including electronics (tunneling field effect transistors and 2D contact), optoelectronics (photodetector), and energy conversion (electrocatalysts and metal ion batteries), to unveil the potentials of vdWHs in practical applications and provide the general design principles of functional vdWHs for different applications. Besides, moiré superlattices based on vdWHs are discussed to showcase the importance of vdWHs as a platform for novel condensed matter physics. Finally, the crucial challenges towards ideal vdWHs with high performance are discussed, and the outlook for future development is presented. By the systematical integration of synthetic strategies and applications, we hope this review can further light up the rational designs of vdWHs for emerging applications.