Broadband Photodetectors Enabled by Localized Surface Plasmonic Resonance in Doped Iron Pyrite Nanocrystals

The emerging capability to detect light over a broad spectral range is a key to technological applications in sensing, spectroscopy, imaging and communications. Colloidal semiconductor nanocrystal/graphene van der Waals heterojunctions provide a unique scheme that combines the spectral tunability and strong quantum confinement of the semiconductor nanocrystals sensitizers with superior charge mobility of graphene for extraordinary photoconductive gains. While high responsivity has been demonstrated, the spectral range is typically narrow limited by the cutoff of the semiconductor band gap of the nanocrystals. Here, a broadband photosensitizer is reported, based on doped Iron Pyrite nanocubes (FeS₂ NCs) that exhibit strong localized surface plasmonic resonance (LSPR) spanning across ultraviolet through visible to near-infrared (UV–Vis–NIR). Using the printed LSPR FeS₂ NCs/graphene van der Waals heterostructure, a broadband UV–Vis–NIR photoresponsivity in exceeding 1.08 × 10⁶ A/W has been demonstrated through development of a ligand-exchange process to facilitate efficient charge transfer at the LSPR FeS₂ NCs/graphene interface. This result demonstrates the viability of the LSPR semiconductor nanocrystal/graphene van der Waals heterostructure for high-performance broadband optoelectronics with scalability through direct printing.