Implications of Charge Penetration for Heteroatom-Containing Organic Semiconductors

The noncovalent interactions of neutral π-conjugated cores, pertinent to organic semiconductor materials, are intimately related to their charge transport properties and involve a subtle interplay of dispersion, Pauli repulsion, and electrostatic contributions. Realizing structural arrangements that are both energetically preferred and sufficiently conductive is a challenge. We tackle this problem by means of charge penetration contribution to the interaction energy, boosted in systems containing large heteroatoms (e.g., sulfur, selenium, phosphorus, silicon, and arsenic). We find that in both the model and "realistic" dimers of such heteroatom-containing cores dispersion is balanced out by the exchange and interaction energy is instead governed by substantial charge penetration. These systems also feature stronger electronic couplings compared to the dispersion-driven dimers of oligoacenes and/or the herringbone assemblies. Thus, charge penetration, enhanced in the π-conjugated cores comprising larger heteroatoms, arises as an attractive strategy toward potentially more stable and efficient organic electronic materials.