Broadband, Flexible, Skin‐Compatible Carbon Dots/Graphene Photodetectors for Wearable Applications

The development of wearable photodetectors demands a unique combination of broadband optical sensitivity, mechanical flexibility, and skin compatibility, with these requirements rarely met simultaneously by existing technologies. Here, photodetectors combining all of these performances are demonstrated through the integration of carbon dots, engineered for extended ultraviolet-to-near-infrared absorption, with single-layer graphene transferred onto a plastic substrate. Unlike traditional quantum dot systems, these carbon dots achieve a broad ultraviolet-to-near-infrared response without toxic heavy metals. Graphene provides an efficient conducting channel for charge transport, while a biocompatible chitosan–glycerol electrolyte enables efficient, low-voltage carrier modulation, with peak performance at approximately 0.5 V gate bias. The resulting photodetectors exhibit a broadband photoresponse with responsivities of approximately 0.19 A W−1 at 406 nm, 0.32 A W−1 at 642 nm, and 0.18 A W−1 at 785 nm. They maintain consistent performance at a bending radius of 0.8 cm with negligible degradation after repeated cycles. Furthermore, skin compatibility and reactive oxygen species assays confirmed the non-toxic and photo-safe nature of the devices for direct skin contact. The combination of broadband absorption (400–800 nm), flexibility, and skin compatibility, along with low-voltage operation (<1.5 V), positions these photodetectors as promising building blocks for next-generation wearable optoelectronics.