Nanolayered BismuthOxyselenide for Field-Effect Transistorsand Photodetectors

Recent advances in the 2D bismuth oxyselenide (Bi<i>_<i>x</i></i>O<i>_<i>y</i></i>Se<i>_<i>z</i></i>) family have attracted significant attention owing to their remarkable stability and high electron mobility. However, achieving low-temperature and stoichiometry-tunable growth of 2D Bi<i>_<i>x</i></i>O<i>_<i>y</i></i>Se<i>_<i>z</i></i> still remains challenging, which further hinders its practical applications. Herein, guided by thermodynamic calculations, two different types of Bi<i>_<i>x</i></i>O<i>_<i>y</i></i>Se<i>_<i>z</i></i> products (Bi₂O₂Se and Bi₃O_2.5Se₂) can be successfully prepared. Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM) were systematically utilized to further confirm the crystal structure, elemental composition, and crystallinity of the as-synthesized Bi<i>_<i>x</i></i>O<i>_<i>y</i></i>Se<i>_<i>z</i></i>. We reveal that both the Bi₂O₂Se- and Bi₃O_2.5Se₂-based field-effect transistors presented an n-type semiconductor behavior with the average field-effect mobilities of 10 and 15 cm² V^–1 s^–1. The Bi₃O_2.5Se₂ photodetector demonstrates outstanding photoresponse performance to the 532 nm light, with a responsivity of 28 A/W, a detectivity of 5.7 × 10⁹ Jones, and a rise/decay time of 3.4 ms/820 μs. Moreover, our Bi₃O_2.5Se₂ device exhibits a wide spectral response from the violet (365 nm) to near-infrared (1064 nm) regions. Our results not only propose an approach for low-temperature and stoichiometry-controlled wafer-scale synthesis of 2D Bi<i>_<i>x</i></i>O<i>_<i>y</i></i>Se<i>_<i>z</i></i> but also showcase their potential for high-performance field-effect transistors and photodetectors.