Interfacial engineering in WS2/CdSe heterostructures for high-performance broadband photodetection.

The optoelectronic performance of two-dimensional transition metal dichalcogenides is fundamentally limited by their weak light absorption at atomic-scale thicknesses. To overcome this challenge, we introduced gold nanoparticles at the van der Waals interface of WS₂/CdSe with optimized type-II band alignment. The integrated Au nanoparticles served dual functions. Firstly, the nanoparticles created plasmonic hotspots that amplified localized electric fields via surface plasmon resonance, significantly boosting light absorption and photocurrent generation. Secondly, the nanoparticles formed Schottky contacts that established electron depletion zones and then suppressed dark current. This synergistic approach yielded excellent performance enhancements, including a 339.9× improvement in light-to-dark current ratio and 119.9× higher responsivity (550 nm, 11.57 mW/cm²) compared to the WS₂/CdSe control. Comprehensive characterization through scanning Kelvin probe force microscopy and finite-element simulations verified both the band alignment and plasmonic enhancement mechanisms, establishing interfacial engineering as a universal strategy for developing high-performance two-dimensional optoelectronic devices.