MoSe₂-Cu₂S Vertical p-n Nanoheterostructures for High-Performance Photodetectors

Heterostructures based on atomically thin two-dimensional layered transition metal dichalcogenides are highly promising for optoelectronic device applications owing to their tunable optical and electronic properties. However, the synthesis of heterostructures with desired materials having proper interfacial contacts has been a challenging task. Here, we develop a colloidal synthetic route for the design of MoSe₂-Cu₂S nanoheterostructures, where the Cu₂S islands grow vertically on top of the defect sites present on the MoSe₂ surface, thereby forming a vertical p-n junction having plasmonic characteristics. These MoSe₂-Cu₂S nanoheterostructures are used to fabricate photodetectors with superior photoresponse characteristics. The fabricated device exhibits a broad-band spectral photoresponse over the visible to near-infrared range with a peak responsivity of 410 mA W^-1 at -2.0 V and over 3000-fold photo-to-dark current ratio. The superior device performance of MoSe₂-Cu₂S over only MoSe₂ devices is due to the combined effect of the formation of the p-n junction, pronounced light-matter interactions, and passivation of surface defects. This study would pave the way for designing a new class of nanoheterostructured materials for their potential applications in next-generation photonic devices.