Plasmonic Ag nanoparticle–engineered Bi₂Te₃ nanosheet interfaces for broadband UV–Vis–NIR photoelectrochemical photodetection

High-performance broadband photodetectors covering ultraviolet to near-infrared wavelengths are critical for next-generation optoelectronic applications, yet achieving high responsivity across such a broad range remains a substantial challenge for conventional semiconductor platforms. Here, we demonstrate a strategy for enhancing the performance of photoelectrochemical (PEC) photodetectors by integrating plasmonic silver nanoparticles (Ag NPs) with annealed bismuth telluride (Bi₂Te₃) nanosheet films. The composite films were fabricated by spin-coating Ag NPs onto solvothermally synthesized Bi₂Te₃ nanosheets subjected to a controlled thermal oxidation. The optimized device, modified with 10 spin-coating cycles of Ag NPs, achieved notable responsivities of 10.84, 8.32, 9.36, and 8.63 mA/W under 365, 470, 530, and 625 nm illumination, respectively. Notably, a fourfold enhancement in responsivity (3.76 mA/W) was attained at 850 nm compared to the unmodified device, effectively enhancing the near-infrared (NIR) sensitivity. This improvement is driven by the synergistic effects of localized surface plasmon resonance (LSPR) and enhanced light scattering. This work demonstrated an effective and scalable material modification strategy for developing high-sensitivity, broadband photodetectors through rational surface plasmon engineering.