Enhanced Plasmonic Hot-Carrier Transfer in Au/WS2 Heterojunctions under Nonequilibrium Condition

The plasmonic hot-carrier is of great importance in applications of photon harvesting, photocatalysis, and photodetectors. However, the plasmonic hot-carrier harvesting efficiency is limited by their ultrafast thermalization in plasmonic nanostructures. Here, we revealed that the hot-carrier of the gold nanostructure could be captured by monolayer-WS2 before thermalization to enhance the harvesting efficiency. We found that the thermalization time of electrons within intraband transition was as long as 600 fs under pump fluence of 21 μJ/cm2, which was much longer than the charge transfer time of 160 fs, and thus nonthermal electrons could be transferred prior to thermalization. We further demonstrated that the contribution of nonthermal electrons increased with decreasing pump fluence or increasing lattice temperature. Finally, the decay process of plasmonic hot-carrier transferred into WS2 was strikingly different from that of intrinsic carriers in WS2 via direct photoexcitation, which is attributed to their different recombination channels. Our results provide insights for microscopic understanding of the nonequilibrium carrier-transfer physics and will facilitate performance optimization of plasmonic hot-carrier-based optoelectronic devices.