Vertically oriented SnS on MoS nanosheets for high-photoresponsivity and fast-response self-powered photoelectrochemical photodetectors.

Van der Waals heterostructures have great potential for the emerging self-powered photoelectrochemical photodetectors due to their outstanding photoelectric conversion capability and efficient interfacial carrier transportation. By considering the band alignment, structural design, and growth optimization, the heterostructures of vertically oriented SnS with different densities on MoS nanosheets are designed and fabricated using a two-step epitaxial growth method. Compared with SnS, MoS, and low density-vertical SnS/MoS heterostructure, the high density-vertical SnS/MoS heterostructure exhibits largely enhanced self-powered photodetection performances, such as a giant photocurrent density (∼932.8 μA cm), an excellent photoresponsivity (4.66 mA W), and an ultrafast response/recovery time (3.6/6.4 ms) in the ultraviolet-visible range. This impressive enhancement of high density-vertical SnS/MoS photodetectors is mainly ascribed to the essentially improved charge transfer and carrier transport of type-II band alignment heterostructures and the efficient light absorption from the unique light-trapping structure. In addition, the photoelectrocatalytic water splitting performance of the high density-vertical SnS/MoS heterostructure also benefits from the type-II band alignment and the light-trapping structure. This work provides valuable inspiration for the design of two-dimensional optoelectronic and photoelectrochemical devices with improved performance by the morphology and heterostructure design.