Large area van der Waals MoS2–WS2 heterostructures for visible-light energy conversion†

In recent years, high-quality transition metal dichalcogenide layers and their van der Waals heterostructures, based on either mechanical exfoliation or chemical vapor deposition, have been successfully employed for the fabrication of electronic and optoelectronic devices, demonstrating their potential towards the integration or replacement of traditional semiconductor technologies. However, these fabrication techniques rely on single flakes with limited size on the scale of tens of micrometers. Here, we propose a large-scale growth process based on physical deposition that enables uniform coverage over cm² areas. This method allows us to fabricate a large area prototype van der Waals heterostructure by vertically stacking in sequence few-layer WS₂–MoS₂ films, forming a type-II heterojunction which shows enhanced photocatalytic dissociation efficiency compared to a reference MoS₂ film. Upon addition of a bottom graphene transparent electrode and a top Au contact, under illumination conditions we find evidence of photovoltage and photocurrent generation, thus demonstrating the potential of our large-scale 2D-TMD growth process in view of scalable, self-powered photoconversion applications.