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.

Charge transfer and transport properties are crucial in the photophysical process of exciton dissociation and recombination at the donor/acceptor (D/A) interface. Herein, machine learning (ML) is applied to predict the charge transfer state energy (E_CT) and identify the relationship between E_CT and intermolecular packing structures sampled from molecular dynamics (MD) simulations on fullerene- and non-fullerene-based systems with different D/A ratios (R_DA), oligomer sizes, and D/A pairs. The gradient boosting regression (GBR) exhibits satisfactory performance (r = 0.96) in predicting E_CT with π-packing related features, aggregation extent, backbone of donor, and energy levels of frontier molecular orbitals. The charge transport property affected by π-packing with different R_DA has also been investigated by space-charge-limited current (SCLC) measurement and MD simulations. The SCLC results indicate an improved hole transport of non-fullerene system PM6/Y6 with R_DA of 1.2:1 in comparison with the 1:1 counterpart, which is mainly attributed to the bridge role of donor unit in Y6. The reduced energetic disorder is correlated with the improved miscibility of polymer with R_DA increased from 1:1 to 1.2:1. The morphology-related features are also applicable to other complicated systems, such as perovskite solar cells, to bridge the gap between device performance and microscopic packing structures.

Rashba spin splitting (RSS) in quantum-spin Hall (QSH) insulators is of special importance for fabricating spintronic devices. By changing the stacking order, a unique bilayered fluorinated arsenene (AsF) system is demonstrated to simultaneously possess RSS and non-trivial topological electronic states. We show by first-principle calculations that tunable RSS can be realized in bilayered AsF. Intrinsic RSS of 25 meV is obtained in the AA-stacked AsF bilayer by considering the spin-orbit coupling effect. The RSS can be tuned in the range of 0 to 50 meV by applying biaxial strains and can be significantly enhanced up to 186 meV in the presence of an external electric field. The AB-stacked AsF bilayer is shown to be a two-dimensional topological insulator with a sizable bulk bandgap of 140 meV (up to 240 meV), which originates from the spin-orbit coupling within the p_{x, y}–p_z band inversion. Surprisingly, RSS up to 295 meV can be induced in the AB-stacked AsF bilayer by applying an external electric field, while the robust topology property without RSS can be retained under the applied strains. The AsF bilayers with tunable RSS and a nontrivial bandgap with AA- and AB-stacking orders can pave the way for designing spin field-effect transistors and new QSH devices.