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.