MoS₂-capped Cu_:XS nanocrystals: A new heterostructured geometry of transition metal dichalcogenides for broadband optoelectronics

Heterostructuring of different transition metal dichalcogenides (TMDs) leads to interesting band alignment and performance improvement, and thus enables new routes for the development of materials for next-generation semiconductor electronics. Herein, we introduce a new strategy for the design and synthesis of functional TMD heterostructures. The representative product, molybdenum disulfide-capped copper sulfide (Cu_xS@MoS₂, 1.8 < x < 2.0), is typically obtained by chemical vapor deposition of cap-like MoS₂ layers on Cu_xS nanocrystals, yielding the formation of a sharp, clean heterojunction interface. The heterostructures exhibit strong light-matter interactions over a broadband range, with interesting band alignment for separating photocarriers and mediating charge transfer. A phototransistor made from Cu_xS@MoS₂ heterostructures shows particularly high photoresponse for near infrared light, which is enabled by the heterojunction of MoS₂ with a small band gap semiconductor as well as the plasmonic enhancement from the Cu_xS nanocrystals. Our study paves a way for the development of new TMD heterostructures towards achieving functional electronics and optoelectronics.