Hole and Electron Mobility in Sulfur- and BN-Functionalized Perylene Diimides: A Computational Study

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Systems based on perylene diimide (PDI) have become highly adaptable scaffolds for next-generation organic electronics, with exceptional potential for tunable charge transport characteristics. This study investigates the intricate interplay between molecular packing and internal structural variations that govern carrier transport behavior in two promising semiconducting candidates, tetra-thionated-PDI (S4-PDI) and Boron–Nitrogen-embedded-PDI (BNNB-PDI), benchmarked against the parent PDI molecule. Employing the carrier hopping regime under a tight-binding approximation, we systematically investigate the conformational space defined by longitudinal and transverse shifts at various rotational angles (ϕ). A diagonal shift of 3 Å from the global minimum (ϕ = 30°) and the orthogonal (ϕ = 90°) stacked conformations show significantly high hole mobility (>1⁡cm2V−1s−1) in PDI and S4-PDI, overcoming the absence of coupling observed along the vertically stacked molecular axis of rotation. Many rotational conformers are found to exhibit highly selective behavior toward either hole or electron mobility. While the ambipolar nature of charge transport is preserved across all three PDI-based systems, distinct trends emerge: S4-PDI (>100X BNNB-PDI) displays a strong preference for hole mobility, particularly at ϕ = 0 and ϕ = 90°. In contrast, BNNB-PDI consistently maintains substantial electron mobility (>10X PDI) across most conformations, leveraging its reduced electron reorganization energy. The study reveals how subtle structural adjustments influence transport properties providing a pathway for the rational design of high-performance organic semiconductors.