Synthesis of Thin Bi₉O_7.5S₆ Nanosheets for Improved Photodetection in a Wide Wavelength Range

Bismuth-based compounds possess layered structures with a variety of stacking modes, endowing the compounds with diverse properties. As one type of bismuth oxysulfides, Bi₉O_7.5S₆ nanocrystals has great applications in photodetection; however, the responsivity of bulky Bi₉O_7.5S₆ is limited due to the poor charge separation. Herein, single-crystalline Bi₉O_7.5S₆ thin nanosheets are successfully synthesized by using a solvothermal method. The thickness of the obtained Bi₉O_7.5S₆ nanosheets is down to 15 nm and can be easily tuned by varying the reaction period. Moreover, the Bi₉O_7.5S₆ nanosheets show strong light absorption in the visible and near infrared range, making it a promising candidate in optoelectronics. As a demonstration, the thin Bi₉O_7.5S₆ nanosheets are used as active layer in an optoelectronic device, which exhibits sensitive photoelectric response to light in a wide range of 400–800 nm. The responsivity of the device reaches up to 1140 μA W⁻¹, and the performance of the device is stable after long-period illumination. This work demonstrates a great potential of the thin Bi₉O_7.5S₆ nanosheets in optoelectronic devices, and these nanosheets may also be extended to various optoelectronic applications.