“…Epitaxy-free van der Waals (vdW) heterostructures formed by vertically stacking two-dimensional (2D) materials have led to a new era in both fundamental physics and applied research due to high-quality heterogeneous interface and tailored energy band alignment . Specifically, the ultrathin heterostructures with a variety of stacking orders have exhibited promising prospect in electronic and optoelectronic applications including field-effect transistors, , memristor, , light-emitting diodes, photodetectors, and so on . Among them, most reported photodetectors were realized by conjugating 2D pn heterostructure with separate p- and n-type semiconductors, which exhibited atomically abrupt heterojunctions and efficient photogenerated carriers separation owing to the large built-in barrier as seen in GaSe/ReS 2 , WSe 2 /MoS 2 , MoTe 2 /ReS 2 , WS 2 /ReS 2 , and WSe 2 /ReSe 2 heterostructures.…”