Modeling of negative photoconductance in plasmonic gold nanoparticle networks

Negative photoconductance (NPC) in metal nanoparticle assemblies remains an elusive phenomenon, arising from the complex interplay between charge transport, ligand conformation, and plasmonic excitation. Here, we present a theoretical multiscale framework that captures both positive and negative photoconductance in networks of gold nanoparticles stabilized by organic ligands. By introducing local photoconductance terms into nanoscale electrical junctions and solving the network charge transport equations with a unique discrete dipole approximation–Kirchhoff approach, we quantitatively reproduce macroscopic photoconductance under varying illumination conditions. NPC is shown to originate from charge transfer coupled to conformational rearrangements of molecular bridges. Comparison between simulations and experiments allows the extraction of the bridge barrier energy, Δ G = − 44 meV, demonstrating that the negative photoconductance is approximately 5.4 times stronger than the positive one. This model provides a unified link between nanoscale dynamics, plasmonic excitation, and macroscopic optoelectronic response and establishes a predictive framework for designing plasmo-electronic nanodevices with tunable light-driven properties.