Ternary Ta₂ PdS₆ Atomic Layers for an Ultrahigh Broadband Photoresponsive Phototransistor

2D noble-transition-metal chalcogenides (NTMCs) are emerging as a promising class of optoelectronic materials due to ultrahigh air stability, large bandgap tunability, and high photoresponse. Here, a new set of 2D NTMC: Ta₂ PdS₆ atomic layers is developed, displaying the excellent comprehensive optoelectronic performance with an ultrahigh photoresponsivity of 1.42 × 10⁶ A W^-1 , detectivity of 7.1 × 10¹⁰ Jones and a high photoconductive gain of 2.7 × 10⁶ under laser illumination at a wavelength of 633 nm with a power of 0.025 W m^-2 , which is ascribed to a photogating effect via study of the device band profiles. Especially, few-layer Ta₂ PdS₆ exhibits a good broadband photoresponse, ranging from 450 nm in the ultraviolet region to 1450 nm in the shortwave infrared (SIR) region. Moreover, this material also delivers an impressive electronic performance with electron mobility of ≈25 cm² V^-1 s^-1 , I_on /I_off ratio of 10⁶ , and a one-year air stability, which is better than those of most reported 2D materials. Our studies underscore Ta₂ PdS₆ as a promising 2D material for nano-electronic and nano-optoelectronic applications.