Molecular interplay at the PMMA dielectric and C₁₃-BTBT semiconductor interface

A growing interest towards all-organic electronics emphasized the importance of interfaces between the functional components of such devices. In particular, the interaction between the dielectric and semiconductor plays a critical role in device functionality, with strong dependency of charge carrier accumulation and mobility on semiconductor molecular arrangement. We report on the beneficial adsorption conformation with a nearly upright standing molecular orientation of a 2-tridecyl-[1]benzothieno[3,2-b][1]benzothiophene (C₁₃-BTBT) semiconductor monolayer deposited on Langmuir-Blodgett-prepared polymethyl methacrylate (PMMA) dielectric films. Such an alignment favors a smooth transfer of charge carriers due to the optimal orbital overlap between π-conjugated BTBT units. Atomistic insights into the C₁₃-BTBT/PMMA system through molecular dynamics revealed an advantageous direct contact of the charge-transporting BTBT unit with PMMA, while the alkyl chain is pointing outwards. Compared to non-alkylated BTBT, we demonstrate a 43% lower stiffness for surface-exposed alkyl chains of a C₁₃-BTBT monolayer, as determined by force-distance analysis, highlighting the advantage for flexible device applications. These insights open new perspectives for further engineering of advanced interfaces, paving the way for innovations in efficient carbon-based electronics.