Ultrasensitive Photodetector Enabled by Atomic-Level Optimization of Graphene-based Heterojunctions

Ultrahigh photoresponsivity is crucial in a wide range of emerging fields. ^{Here, we report a photodetector with ultrahigh photoresponsivity that outperforms all the current state-of-the-art photodetectors under illumination powers from 3 nW to 10 mW. Remarkably, photoresponsivity as high as ~ 10⁷ A/W is achieved under 3 nW illumination, surpassing the previously reported values by more than one order of magnitude. The key to the high photoresponsivity lies in the optimization on the atomic-level heterojunctions between photoactive copper phthalocyanine molecules and adjacent graphene oxide sheets in the photodetector, which greatly enhances the electronic coupling at the heterojunction for charge transport. This photodetector has good flexibility, enabling simultaneous contact sensing and non-contact perception serving as a novel electronic skin under ambient illumination down to dim moonlight. The developed strategy provides a new perspective for fabricating next-generation photoelectric conversion devices with potential applications spanning intelligent sensing, aerospace technologies, and defense-related photonic platforms.}