Interdigital MnO₂/PEDOT Alternating Stacked Microelectrodes for High-Performance On-Chip Microsupercapacitor and Humidity Sensing

For microelectronic devices, the on-chip microsupercapacitors with facile construction and high performance, are attracting researchers' prior consideration due to their high compatibility with modern microsystems. Herein, we proposed interchanging interdigital Au-/MnO2/polyethylene dioxythiophene stacked microsupercapacitor based on a microfabrication process followed by successive electrochemical deposition. The stacked configuration of two pseudocapacitive active microelectrodes meritoriously leads to an enhanced contact area between MnO2 and the conductive and electroactive layer of polyethylene dioxythiophene, hence providing excellent electron transport and diffusion pathways of electrolyte ions, resulting in increased pseudocapacitance of MnO2 and polyethylene dioxythiophene. The stacked quasi-solid-state microsupercapacitors delivered the maximum specific capacitance of 43 mF cm(-2) (211.9 F cm(-3)), an energy density of 3.8 mu Wh cm(-2) (at a voltage window of 0.8 V) and 5.1 mu Wh cm(-2) (at a voltage window of 1.0 V) with excellent rate capability (96.6% at 2 mA cm(-2)) and cycling performance of 85.3% retention of initial capacitance after 10 000 consecutive cycles at a current density of 5 mA cm(-2), higher than those of ever reported polyethylene dioxythiophene and MnO2-based planar microsupercapacitors. Benefiting from the favorable morphology, bilayer microsupercapacitor is utilized as a flexible humidity sensor with a response/ relaxation time superior to those of some commercially available integrated microsensors. This strategy will be of significance in developing highperformance on-chip integrated microsupercapacitors/microsensors at low cost and environment-friendly routes.