Ultrasensitive photodetectors enabled by pressure-induced atomic-level optimization of graphene-based heterojunctions

Photodetectors with high photoresponsivity are crucial in a wide range of emerging fields. Here, we report the realization of photodetectors based on co-assembled composite membranes consisting of copper phthalocyanine (CuPc) molecules and graphene oxide (GO) sheets, showing a photoresponsivity as high as ~ 10⁷ A/W under 3 nW illumination and a moderate external pressure (~1 atm) in the visible range. We attribute the high photoresponsivity to the pressure-induced optimization of the atomic-level heterojunctions between photoactive CuPc molecules and adjacent GO sheets in the photodetector, which enhances the electronic coupling at the heterojunction for charge transport. The photodetectors show good flexibility for electronic skin applications, enabling simultaneous contact sensing and non-contact perception under ambient illumination down to dim moonlight. The developed strategy provides a promising perspective for fabricating next-generation photoelectric conversion devices with potential applications spanning intelligent sensing, aerospace technologies, and defence-related photonic platforms.