Ultrafast Insights into the Dual-Plasmonic Interaction and Interfacial Charge Separation in the Janus-Type Au-Cu x In y S Heterostructure

Efficient extraction of hot carriers remains a major challenge in plasmonic systems due to their ultrafast relaxation and recombination dynamics. Here, we report the synthesis of Au-CuxInyS (Au-CIS) dual-plasmonic heterostructure nanocrystals (NCs) through a hot-injection method and investigate their ultrafast charge transfer dynamics using femtosecond transient absorption spectroscopy. The heterostructure offers a promising platform for extending light absorption in the entire solar spectrum. Transient absorption measurements reveal the coexistence of hot electron transfer from Au to CIS and hot hole transfer from CIS to Au. The heterostructure exhibits accelerated electron relaxation in Au along with prolonged near infrared (NIR) bleach recovery in CIS, confirming efficient bidirectional charge transfer and the existence of long-lived charge separated states across the interface. Compared to the pristine components, the Au-CIS heterostructure demonstrates enhanced photocurrent generation under visible-light illumination, highlighting improved carrier extraction and reduced recombination losses. Importantly, this work demonstrates that dual-plasmonic heterostructures can effectively mitigate the intrinsic limitation of ultrafast hot carrier decay in conventional plasmonic materials by enabling rapid interfacial carrier separation. These findings provide new insight into the design of dual-plasmonic heterostructures for efficient hot carrier utilization and open new opportunities for applications in photocatalysis, photodetection, and solar energy conversion.