Plexcitonic interactions in spherical and bi-pyramidical Au nanoparticles with monolayer WSe2

Plasmons associated with zero-dimensional (0D) metal nanoparticles and their synergistic interactions with excitons in two-dimensional (2D) semiconductors offer opportunities for remarkable spectral tunability not otherwise evident in the pristine parent materials. As a result, an in-depth study elucidating the nature of the plasmonic and excitonic interactions, jointly referred to as plexcitons, is critical to understanding the foundational aspects of the light–matter interactions in hybrid 0D–2D systems. In this work, our focal point is to examine the plexcitonic interactions of van der Waals (vdWs) hybrid structures composed of 2D WSe2 and 0D Au nanoparticles (Au-NPs) in their spherical (Au-Sp) and bi-pyramidical (Au-BP) architectures. The geometry-dependent surface plasmon resonance (SPR) peaks in Au-Sp and Au-BP nanoparticles were deciphered using ultraviolet-visible (UV-Vis) optical absorption spectroscopy, while photoluminescence spectroscopy revealed the excitonic behavior in the vapor synthesized monolayer (1L) WSe2 as well as the Au-Sp/WSe2 and Au-BP/WSe2 hybrids. Furthermore, our temperature-dependent and wavelength-dependent optoelectronic transport measurements showed a shift in the spectral response of 1L WSe2 toward the SPR peak locations of Au-Sp and Au-BP, mediated via the plexciton interactions. Models for the plexcitonic interactions are proposed, which provide a framework to explain the photoexcited hot charge carrier injection from AuNPs to WSe2 and their influence on carrier dynamics. Our findings demonstrate that geometry-mediated response of the AuNPs provides another degree of freedom to modulate the carrier photodynamics in WSe2, which can also be useful for tailoring the optoelectronic performance of the broader class of semiconducting 2D materials.