Probing Femtosecond Charge Transfer Dynamics in P3HT-WS₂ Nanocomposites via Resonant Core Hole Clock Spectroscopy

We investigate the ultrafast charge transfer (CT) dynamics in a nanocomposite of poly-(3-hexylthiophene-2,5-diyl) (P3HT) and tungsten disulfide (WS₂) using the core-hole clock (CHC) spectroscopy method, complemented by atomic force microscopy (AFM), near-edge X-ray absorption fine structure (NEXAFS), and X-ray photoelectron spectroscopy (XPS). AFM and NEXAFS reveal that the incorporation of WS₂ modifies the nanoscale morphology and reduces the molecular ordering of P3HT, while XPS evidence the formation of a donor-acceptor interface. CHC analysis demonstrates orbital-specific enhancement of interfacial CT: the transfer time decreases from 8.1 ± 0.5 fs in pure P3HT polymer film to 4.8 ± 0.5 fs in the nanocomposite for π* orbitals and from 2.7 ± 0.5 fs to 1.4 ± 0.5 fs for σ* orbitals. The dependence of τ_CT on excitation energy indicates a tunneling-mediated mechanism with enhanced electronic delocalization across the interface. These findings provide direct insight into how WS₂ incorporation promotes CT at the molecular level, highlighting P3HT-WS₂ nanocomposites as promising candidates for ultrafast optoelectronic applications.