Interfacial electronic structure modulation in ultrathin polymer graphene heterostructures

Official URL: https://dx.doi.org/10.1016/j.apsusc.2026.168081

Ultrathin graphene polymer heterostructures provide a model platform for investigating interface-induced charge redistribution at organic–inorganic contacts. Here, using density functional theory, we examine the interaction between graphene and poly(3-hexylthiophene) (P3HT) as a function of chain length, termination, periodicity, and structural order. For isolated P3HT, the band gap decreases with increasing chain length and layer thickness, while structural disorder slightly increases the gap due to reduced intermolecular coupling. After formation of the graphene/P3HT interface, all configurations exhibit spontaneous charge redistribution governed by energy-level alignment, resulting in electron accumulation on graphene and hole localization within the polymer. The magnitude of charge transfer is significantly enhanced in ordered and periodic structures due to stronger electronic coupling and wavefunction delocalization, whereas disorder suppresses interfacial charge transfer by reducing orbital overlap. Additionally, graphene/P3HT/graphene heterostructures display capacitor-like behavior under an external electric field. These results demonstrate how polymer structural order governs interfacial charge transfer at graphene-based surfaces.