Tip-enhanced photoluminescence imaging of porphyrin tapes: exploring the nonlocality of molecular orbitals

Abstract We have developed a theoretical framework for evaluating tip-enhanced photoluminescence (TEPL) of single molecules based on the nonlocal response theory. This framework self-consistently solves molecular polarization and electric field using a Green’s function accounting for arbitrary nanostructure geometries. Focusing on porphyrin tape molecules (two, four, and six units), our study reveals two-lobe TEPL images, where lobe separation increases with molecular size, deviating from point dipole approximations. Furthermore, TEPL images of optically forbidden transitions reflect the spatial structure of wavefunction and polarization. These calculations, clarifying mechanisms underlying experimental observations, advance understanding of nanoscale light–matter interactions and guide molecule-based photonic device design.