MoSe 2 -Cu 2 S 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 vertical p-n junction having plasmonic characteristics. These MoSe2-Cu2S nanoheterostructures have been used to fabricate photodetectors with superior photo response characteristics. The fabricated device exhibits a broadband spectral photo response over the visible to near infrared range with a peak responsivity of 410 mAW-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 p-n junction, pronounced light-mater interaction and passivation of surface defects. This study would pave the way for designing a new class of nanoheterostructured materials for their potential applications in the next generation photonic devices.