Sb₂S₃/Sb₂Se₃ heterojunction for high-performance photodetection and hydrogen production

Photoelectrochemical (PEC)-type devices provide promising ways for harvesting solar energy and converting it to electric and chemical energy with a low-cost and simple manufacturing process. However, the high light absorption, fast carrier separation, and low carrier recombination are still great challenges in reaching high performance for PEC devices. As emergent two-dimensional (2D) materials, Sb₂Se₃ and Sb₂S₃ exhibit desirable photoelectric properties due to the narrow bandgap, large optical absorption, and high carrier mobility. Herein, Sb₂S₃/Sb₂Se₃ heterojunction is synthesized by a two-step physical vapor deposition method. The type-II Sb₂S₃/Sb₂Se₃ heterojunction displays excellentphotoelectric properties such as a high photocurrent density (I_ph ∼ 162 µA cm^-2), a high photoresponsivity (R_ph ∼ 3700 µA W^-1), and a fast time response speed (rising time ∼ 2 ms and falling time ∼ 4.5 ms) even in harsh environment (H₂SO₄ electrolyte). Especially, the Sb₂S₃/Sb₂Se₃ shows an excellent self-powered photoresponse (I_ph ∼ 40 µA cm^-2, R_ph ∼ 850 µA W^-1). This increment is attributed to the improvement in light absorption, charge separation, and charge transfer efficiency. Taking these advantages, the Sb₂S₃/Sb₂Se₃ heterojunction also exhibits higher PEC water splitting synergically, which is approximately 3 times larger than that of Sb₂Se₃ and Sb₂S₃. These results pave the way for high-performance PEC devices by integrating 2D narrow bandgap semiconductors.