Speaker
Description
Understanding how molecular organization in solution governs excitonic coupling and structure in conjugated polymer nanostructures remains a central challenge in soft condensed matter physics. Here, we show that controlled solution-state pre-assembly of poly(3-hexylthiophene) (P3HT) prior to nanoparticle (NP) formation enables tuning of intrachain and interchain interactions, with direct consequences for the excitonic landscape. Progressive pre-assembly in chloroform promotes chain planarization and the emergence of intrachain-dominated (J-like) interactions, evidenced by red-shifted absorption, enhanced 0-0 vibronic intensity, a reduced optical bandgap, and increased near-infrared absorption associated with sub-gap electronic states. These signatures are preserved in NPs produced by miniemulsion, indicating that solution-state correlations are imprinted into the solid-state morphology.
By combining optical spectroscopy and structure characterization, we establish a direct relationship between pre-assembly time, π–π stacking and crystalline coherence length, revealing a non-monotonic evolution of electronic order. An optimal pre-assembly regime maximizes backbone planarization and excitonic delocalization while maintaining finite structural disorder at the nanoscale.
These results highlight solution-state pre-organization as an effective route to control excitonic coupling and electronic disorder in conjugated polymer nanostructures, providing general design principles for soft semiconducting systems with tunable optical and electronic properties. These principles are finally illustrated through visible-light photocatalysis, used here as a functional probe of the tuned excitonic landscape.