Ultrafast Plasmonic Hot Hole Transfer and Plasmon Dynamics in a Dual Plasmonic Au@p‐Cu2−xSe Heterostructure

Metal‐semiconductor heterostructures have significant potential in harvesting plasmon induced hot charge carriers for photocatalytic and photovoltaic devices. Despite numerous studies, the field of hot hole transfer in heterostructures remains unexplored. In this work, the plasmon dynamics of a dual plasmonic core–shell Au@p‐Cu2−xSe heterostructure are investigated with the aid of femtosecond broadband pump probe spectroscopy. Ultrafast studies reveal that hot holes generated within the d and sp band after 400 and 800 nm excitations are injected from Au to copper selenide. Hot hole transfer substantially reduces the transient signal intensity and electron phonon relaxation time for Au plasmon. Increment in the transient signal intensity and slower kinetics for the semiconducting plasmon of Au@Cu2−xSe validate the hot hole transfer in the valence band of copper selenide. Fluence dependent studies reveal that d band hot holes extraction is more efficient than that of sp band hot holes. Favorable distribution of high energetic hot holes is created in Gold (Au) upon 400 and 800 nm photoexcitation, which are subsequently transferred to the valence band of copper selenide, altering the hole–phonon relaxation dynamics for the copper selenide probed in the near infra‐red region and electron–phonon relaxation time for Au.