Ultrabroadband Photodetectors up to 10.6 µm Based on 2D Fe₃ O₄ Nanosheets

The ultrabroadband spectrum detection from ultraviolet (UV) to long-wavelength infrared (LWIR) is promising for diversified optoelectronic applications of imaging, sensing, and communication. However, the current LWIR-detecting devices suffer from low photoresponsivity, high cost, and cryogenic environment. Herein, a high-performance ultrabroadband photodetector is demonstrated with detecting range from UV to LWIR based on air-stable nonlayered ultrathin Fe₃ O₄ nanosheets synthesized via a space-confined chemical vapor deposition (CVD) method. Ultrahigh photoresponsivity (R) of 561.2 A W^-1 , external quantum efficiency (EQE) of 6.6 × 10³ %, and detectivity (D*) of 7.42 × 10⁸ Jones are achieved at the wavelength of 10.6 µm. The multimechanism synergistic effect of photoconductive effect and bolometric effect demonstrates the high sensitivity for light with any light intensities. The outstanding device performance and complementary mixing photoresponse mechanisms open up new potential applications of nonlayered 2D materials for future infrared optoelectronic devices.