High‐Performance Flexible Broadband Photodetectors Based on 2D Hafnium Selenosulfide Nanosheets

2D transition‐metal dichalcogenides have attracted significant interest in recent years due to their multiple degrees of freedom, allowing for tuning their physical properties via band engineering and dimensionality adjustment. The study of ternary 2D hafnium selenosulfide HfSSe (HSS) high‐quality single crystals grown with the chemical vapor transport (CVT) technique is reported. An as‐grown HSS single crystal exhibits excellent phototransistor performance from the visible to the near‐infrared with outstanding stability. A giant photoresponsivity (≈6.4 × 104 A W−1 at 488 nm) and high specific detectivity (≈1014 Jones) are exhibited by a device fabricated by exfoliating single‐crystal HSS of nano‐thickness on a rigid Si/SiO2 substrate. The application of HSS single crystal is extended to yield a sensible flexible photodetector of photoresponsivity up to ≈1.3 A W−1 at 980 nm. The photoresponsivity of CVT‐grown HSS single crystal is significantly larger than those fabricated with other existing Hf‐based chalcogenides. The results suggest that the layered multi‐elemental 2D chalcogenide single crystals hold great promise for future wearable electronics and integrated optoelectronic circuits.