Self-Powered broadband photodetection of copper phthalocyanine by enhancing photogating effect with monolayer MoS2 flakes

Highlights: • Demonstrated lithography free device fabrication using monolayer MoS₂ flakes. • Laterally staggered type-II heterojunctions formed by embedding MoS₂ in CuPc film. • Interfacial built-in potential in MoS₂:CuPc results easy exciton dissociation. • MoS₂ as charged puddles enhanced the photogating effect largely by capturing electrons. • Finally, self-powered broadband photodetection of MoS₂:CuPc hybrid demonstrated. Here, we demonstrated a self-powered broadband photodetector using thermal CVD-grown in situ monolayer MoS₂ flakes embedded below a solution-coated copper phthalocyanine (CuPc) layer. Lateral heterojunction with type-II staggered band-alignment between MoS₂ and CuPc produces an interfacial built-in potential, enabling self-powered operation. Interestingly, a distinct phenomenon, which can be termed as spontaneous photogating, is identified that looks different from standard one based on charge trapping at defects and dielectric-interface. Mostly, exciton dissociated electrons were confined in MoS₂ and form charged-puddles below CuPc layer as evidenced with Raman scattering results, which strongly modulates the optoelectronic property of MoS₂/CuPc lateral-heterojunctions device. Eventually, CuPc itself is doped heavily with photo-generated holes under favourable energy-band alignment, which enhances overall photoconductivity. Hence, MoS₂/CuPc photodetectors depict superior UV–Vis-NIR broadband photoresponse with 90% EQE at 1100 nm. We also achieved a responsivity and detectivity of about 0.7 A/W and ~ 10¹¹ Jones, respectively, with a response speed of about 50 ms. This faster device response with self-powered operation is the main advantage compared with usual photogating based devices. Finally, the strategy proposed here will broaden the utilization of various TMDs without using sophisticated tools that significantly reduces the fabrication cost, processing time, and overall environmental hazards.