Trion Modulation in Gold‐Tungsten di‐Sulfide Heterojunction

Strong coulombic interaction in monolayer transition metal dichalcogenides (TMDCs) results the formation of quasi‐particles like excitons, biexcitons and trions even at room temperature. Trion's ability to carry an additional charge and spin‐valley information would make 2D TMDCs as a strong candidate in optoelectronic and spin‐valley‐related applications. In this regard, trion enhancement would be regarded as a promising approach. This work reports the first systematic study of the fundamental photophysical mechanism underlying trion enhancement in a designed metal‐semiconductor (Au‐WS 2 ) heterojunction using multi‐technique spectroscopy. The photoluminescence and broadband transient absorption spectroscopy revealed that the plasmonic hot electron transfer from Au to WS 2 enhanced the electron density in the WS 2 system, which further improve the trion formation within the heterojunction. Optical pump terahertz probe spectroscopy illustrated two times higher photoconductivity and sluggish effective mobility decay in the heterojunction due to improved electron density and trion formation, respectively. This study demonstrates an important advancement in trion modulation as well as plasmonic hot carriers’ extraction in metal‐TMDC heterostructures, which will pave the way for their effective utilization in next‐generation solar‐driven and spintronic devices.