MoS2-capped CuxS 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 (CuxS@MoS2, 1.8 < x < 2.0), is typically obtained by chemical vapor deposition of cap-like MoS2 layers on CuxS 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 CuxS@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 CuxS nanocrystals. Our study paves a way for the development of new TMD heterostructures towards achieving functional electronics and optoelectronics.