Facet-Engineered (100)-Oriented MoO₂ Nanoribbons for Broadband Self-Powered Photodetection

Broadband photodetection plays a vital role in aerospace applications, biomedical imaging, and advanced communication systems. While molybdenum dioxide (MoO₂) exhibits exceptional electrical conductivity, carrier mobility, and environmental stability, its potential for photodetection has remained unrealized, with existing literature reporting negligible optoelectronic responses. Here, we unlock latent photoresponsivity of MoO₂ by facet engineering, demonstrating that exposing the (100) crystallographic plane activates its intrinsic photoelectric conversion. Using atmospheric-pressure chemical vapor deposition, we successfully fabricated large-area arrays of (100)-oriented MoO₂ nanoribbons. The resulting flexible photodetector on polyethylene glycol terephthalate (PET) substrate exhibits unprecedented performance, achieving broadband detection from visible to long-wave infrared (LWIR: 0.5-10.5 µm) range without external bias. The device demonstrates a fivefold enhancement in responsivity compared to rigid substrate configurations, reaching 107.31 mA W^-1 at 10.5 µm wavelength with an exceptionally low noise-equivalent power (NEP) of 6.64 pW Hz^-0.5, surpassing all self-powered photodetectors reported to date. Comprehensive characterization reveals distinct photoresponse mechanisms: photothermoelectric effects dominate on silicon substrates, while photobolometric behavior prevails in flexible configurations. These findings not only resolve the previously observed photoresponse limitations in MoO₂ but also establish facet engineering as a general approach for developing high-performance photodetectors based on metallic oxides, with significant implications for flexible optoelectronic applications.