Synthesis, Characterization, and Photodetector Application of Alkali Metal Bismuth Chalcogenide Nanocrystals

We exploited a facile solution approach to synthesize a series of high-quality, abundant, and nontoxic bismuth ternary chalcogenides with the formula of ABiX₂ (A = Na, K, or Cs, and X = S or Se) nanocrystals (NCs), achieving the first successful synthesis of KBiS₂ nanoparticles and KBiSe₂ and CsBiS₂ nanoplatelets. The as-prepared NCs exhibit narrow size distributions, exceptional air stability, and strong absorption in the range from visible to near-infrared. The photodetector based on the ABiX₂ NCs display good photoresponse and reproducibility in the visible range under monochromatic visible light at different wavelengths. The KBiS₂ nanoparticle-based device demonstrates the best photoresponse property under a 525 nm laser illumination: a detectivity of approximately 5.1 × 10¹⁵ Jones, a high current on/off ratio of approximately 40, and photoresponse times of 120 ms (rise time) and 220 ms (fall time), respectively. These results indicate that ABiX₂ NCs are potential candidates for use in new multifunctional photoelectronic devices.