Hierarchical Nanosheet-Based NaBiS₂ Flowers for High-Performance and Self-Powered Broadband Photodetectors

Alkali bismuth ternary sulfides have been increasingly studied in optoelectronic devices, owing to their unique properties. Here, sodium bismuth sulfide (NaBiS2) flowers are successfully fabricated for the first time via a facile hydrothermal method. The obtained NaBiS2 flowers with a mean diameter of approximately 6 μm, assembled from nanosheets (NSs), have a three-dimensional hierarchical structure. The NaBiS2 NSs, with a thickness of approximately 60-90 nm, are formed by many regularly crossed and interlaced ultrathin flakelets. The detection performance of the photodetector based on the NS-based NaBiS2 flowers is further investigated without an external power source. The obtained results suggest that the NaBiS2 flower photodetector achieves a broadband response ranging from ultraviolet (365 nm) to infrared (850 nm) at a zero bias voltage. The NaBiS2 flower photodetector exhibits excellent photodetection performance, including a fast response speed (rising time of ∼26.50 ms and decay time of ∼66.72 ms), high responsivity (∼10.36 mA/W), and specific detectivity (∼3.04 × 1010 Jones), as well as outstanding stability and reproducibility. Moreover, the possible detection mechanism of the NaBiS2 flower photodetector is also proposed.