Engineering silver–BNNS heterostructures: from materials innovation to broadband optoelectronic devices

Abstract We report a thermally robust, self-powered broadband photodetector based on hexagonal boron nitride nanosheets synthesized by pulsed-laser-deposition and decorated with spin-coated silver nanoparticles. The resulting gold/silver nanoparticle-decorated hexagonal boron nitride nanosheet/gold heterostructure exhibits stable operation at low or zero applied bias with reproducible on–off cycling, and maintained high performance up to 200 °C. Under ultraviolet illumination at a wavelength of 254 nm, the devices deliver a responsivity of 354 mA/W at 0.6 V and 1.69 mA/W at zero bias, while at 670 nm, the devices achieve a responsivity of 29.1 mA/W with a detectivity (D*) of 5.20 × 10 11 Jones. The enhanced broadband response is attributed to plasmon-assisted light absorption in silver nanoparticles combined with efficient charge carrier separation at asymmetric Schottky contacts. First-principle density functional theory calculations further reveal that bonding between silver atoms and dangling boron and nitrogen sites introduces mid-gap electronic states and significantly narrows the effective bandgap of hexagonal boron nitride nanosheets, thereby enabling efficient charge transport beyond the intrinsic ultraviolet response. These results show a simple and scalable strategy for electronically activating boron nitride–based heterostructures toward high-performance, thermally robust, self-powered broadband optoelectronic devices.