2D ultrathin graphene heterostructures for printable high-energy micro-supercapacitors integrated into coplanar flexible all-in-one microelectronics

Printable micro-supercapacitors (MSCs) with remarkable versatility, customizability, high power density and long cycling lifespan, are regarded as a promising class of miniaturized power source for wearable and portable microelectronics. Herein, we demonstrate a novel Fe-based zeolitic imidazolate framework (Fe-ZIF)/graphene (FZG) heterostructure with high specific surface area and outstanding electrical conductivity for planar MSCs (FZG-MSCs) worked in a high-voltage ionic liquid gel electrolyte via a spray-printed strategy. The fully printed FZG-MSCs deliver a high areal energy density of 9.5 μWh/cm2, extraordinary cyclability, and tailored voltage/capacitance output. Furthermore, using a fully printed FZG-MSC, we seamlessly integrate a monolithically planar all-flexible self-sustained sensor system with a mounted solar cell and a printable NH3 gas sensor on the same side of single flexible substrate. The self-sustained sensor system exhibits high-sensitivity NH3 detection with a good response of 18.3% at 20 ppm and linear sensibility exposed to 2–20 ppm. Such a fully integrated system can utilize the converted solar energy stored in the MSC, and offer efficient electricity to power microelectronics whenever needed. Therefore, this contribution of printable planar device and integrated system paves a new avenue for constructing flexible microelectronics.