An Interdigital Planar Energy Harvesting/Storage Device Based On an Ionic Solid–Gel Polymer

The generation of efficient self-powered energy harvesting/storage technologies is a milestone demand to the field of the Internet of Things. In this work, an interdigital planar all-in-one thermally chargeable supercapacitor (IPTS) was successfully produced by merging energy harvesting and storage technologies. The smart device was produced through a photolithography process, combining carbon nanotubes as an electrode material with polyvinyl alcohol (PVA) doped with H3PO4 as a solid–gel polyelectrolyte. The ionic conductivity of PVA doped with H3PO4 was tuned by changing the amount of H3PO4 within the PVA matrix, unveiling an optimum ratio of PVA/H3PO4 of 1:1 (m/m). The power generation performance of the IPTS was evaluated. The device reached a Soret coefficient of 2.35 mV K–1, which is one order of magnitude higher than those of thermoelectric materials (few hundreds of μV K–1). Moreover, it reached a voltage generation output of up to 45 mV for ΔT = 20 K. Concerning energy storage features, the device worked as an electric double-layer capacitor, affording an energy density of 1.05 mW h cm–3 at a power density of 1.21 W cm–3. The tailored interdigital configuration, high flexibility, and energy efficiency of the IPTS, combined with a cost-effective production process that offers the possibility of scale-up, open unique horizons in the field of flexible electronics.