Plasmon-Enhanced Interlayer Transition in WSe₂/MoSe₂ Heterojunctions for Near-Infrared Photodetection

2-D transition metal dichalcogenides (TMDCs) have great potential in ultra-thin photodetectors. However, the atomically thin thickness leads to weak light absorption, thus hindering their applications. Herein, this work demonstrates that the modification of MoSe₂/WSe₂ heterojunction photodetectors with gold (Au) nanorods can dramatically enhance the photoelectric performance of heterojunction photodetectors. The Au nanorods are integrated into TMDCs heterojunctions of WSe₂/MoSe₂ (Au/WSe₂/MoSe₂) by a dry-transfer method. The responsivity of its photodetector is dramatically improved from visible to infrared spectral range, with a maximum enhancement of 97-fold at 750 nm and a large enhancement of 42-fold at 1100 nm. The enhancement is attributed to the broadband surface plasmon resonance supported by the Au nanorods. Combining TMDCs heterojunction with surface plasmon metal nanostructures provides a new strategy for realizing photodetectors with high response in a broad spectral range.