Ultrasensitive photoelectric detection with room temperature extremum

Room-temperature photodetection holds pivotal significance in diverse applications such as sensing, imaging, telecommunications, and environmental remote sensing due to its simplicity, versatility, and indispensability. Although different kinds of photon and thermal detectors have been realized, high sensitivity of photodetection with room temperature extremum is not reported until now. Herein, we find evident peaks in the photoelectric response originated from the anomalous excitonic insulator phase transition in tantalum nickel selenide (Ta₂NiSe₅) for room-temperature optimized photodetection from visible light to terahertz ranges. Extreme sensitivity of photoconductive detector with specific detectivity (D*) of 5.3 × 10¹¹ cm·Hz^1/2·W^-¹ and electrical bandwidth of 360 kHz is reached in the terahertz range, which is one to two orders of magnitude improvement compared to that of the state-of-the-art room-temperature terahertz detectors. The van der Waals heterostructure of Ta₂NiSe₅/WS₂ is further constructed to suppress the dark current at room temperature with much improved ambient D* of 4.1 × 10¹² cm·Hz^1/2·W^-1 in the visible wavelength, rivaling that of the typical photodetectors, and superior photoelectric performance in the terahertz range compared to the photoconductor device. Our results open a new avenue for optoelectronics via excitonic insulator phase transition in broad wavelength bands and pave the way for applications in sensitive environmental and remote sensing at room temperature.