Ultrafast hot carrier extraction and diffusion at the MoS/Au van der Waals electrode interface.

Metal electrode deposition is universally adopted in the community for optoelectronic device fabrication, inducing hybridization at electrode interfaces, and allows efficient extraction or injection of photocarriers. However, hybridization-induced midgap states increase photocarrier recombination pathways, creating a paradoxical trade-off. Here, we discovered that efficient photocarrier extraction and a long photocarrier lifetime can be achieved simultaneously in MoS/van der Waals Au contact, minimizing photocarrier loss at the interface. Using transient reflection spectroscopy, we quantified an ultrafast hole extraction time of 310 femtoseconds and a photocarrier lifetime of 259 picoseconds. Suppressed exciton formation in diffusion measurement validated ultrafast hole extraction. We further revealed a short photocarrier lifetime of ~8.7 picoseconds in deposited contact and negligible hole extraction in unintimate contact with space gap at the interface. We unraveled the hot electron transfer process from Au to MoS in different contact interfaces. Our results on different metal contact interfaces provide valuable insights into electrode engineering for future optoelectronic devices.