Ultrafast Plasmonic Hot-Hole Transfer Mediated Efficient Charge Separation in Cu2-xS/CdZnS Heterostructure

Abstract

Heterostructure engineering offers a powerful route for hot-carrier harvesting, where band alignment dictates charge-carrier transfer. Although plasmonic materials are efficient generators of hot carriers, rational design of heterostructures that facilitate their directional extraction and utilization remains insufficiently explored. Here, we report a plasmonic Cu2-xS/CdZnS heterostructure that enables efficient hot-carrier extraction and enhanced interfacial charge separation. Ultrafast transient absorption (TA) spectroscopy under 800 nm excitation reveals plasmon-induced hot-hole transfer from valence band of Cu2-xS to CdZnS, demonstrating the ability to harvest low-energy near-infrared photons. Complementary TA measurements under 400 nm excitation further confirm hot-hole migration from deeper valence-band states of Cu2-xS into CdZnS. In addition, TA studies probed in the visible region indicate electron transfer from conduction band (CB) of CdZnS to the CB of Cu2-xS, resulting in efficient spatial separation of electrons and holes across the interface. Current-Voltage (I-V) measurements of thin-film devices shows significantly enhanced photoconductivity in the heterostructure compared to the individual components, confirming improved carrier extraction and interfacial transport. These findings establish the critical role of band alignment in governing plasmon-induced charge migration and demonstrate that Cu2-xS/CdZnS heterostructures provide an effective platform for hot-carrier harvesting, with promising implications for plasmon-enhanced solar energy conversion and optoelectronic applications.