Large-scale free-standing Bi₂Te₃/Si heterostructures developed by a modified solvothermal method for a self-powered and efficient imaging photodetector

Topological insulator bismuth telluride (Bi₂Te₃), an exotic state of quantum matter, has broad application prospects in next-generation optoelectronic devices. However, photoexcited carriers in Bi₂Te₃ usually relax rapidly due to the lack of a large band gap. Herein, high-quality Bi₂Te₃/Si heterojunction is successfully synthesized by a low-cost modified two-step solvothermal method to grow large-scale free-standing Bi₂Te₃ nanosheets on a Si substrate. Benefiting from the promotion of photogenerated carrier separation and transport by the built-in electric field at the Bi₂Te₃/Si heterojunction interface, the Bi₂Te₃/Si heterojunction photodetector exhibits a high responsivity of 16.44 mA W⁻¹, a high specific detectivity of 2.44 × 10¹¹ Jones, and fast rise/recovery times of 11/13 ms under 470 nm illumination at zero bias. Additionally, the device has potential applications in high-resolution imaging. In view of its overall photosensitivity performance and low cost, the Bi₂Te₃/Si heterojunction synthesized by the solvothermal method has a promising application in fast broadband photodetectors, and also provide a new route for the growth of Bi₂Te₃ nanosheets on substrates.