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

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 similar to 10(11) 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.

Automated summary

In this study, a self-powered broadband photodetector utilizing a lateral heterojunction between MoS2 and CuPc was demonstrated. The interfacial built-in potential and modulation of optoelectronic properties led to superior UV-Vis-NIR broadband photoresponse. Additionally, the device showed a faster response speed and self-powered operation, making it advantageous compared to conventional photogating-based devices.