Transparent, stretchable and high-performance triboelectric nanogenerator based on dehydration-free ionically conductive solid polymer electrode

Stretchable energy harvesting sources that are comfortable to wear are urgently needed to power next-generation wearable electronics and Internet of Things (IoTs) devices. Herein we present a novel triboelectric nanogenerator (TENG) employing solid polymer electrolyte (SPE) as a stretchable and transparent electrode for the first time. The use of SPE endows the TENG with high stretchability, superb transparency, environmental stability, and enhanced electrical output. By combining phosphoric acid (H3PO4) with biocompatible polyvinyl alcohol (PVA), the resulting SPE achieves a stretchability of 1058% and ionic conductivity of 1.39 S m−1 due to the dual functions of H3PO4 as both the plasticiser and the ion-conductive charge carrier. The formation of an electrical double layer (EDL) between the ion-conducting SPE and the electron-conducting carbon tape dramatically increased the electric output and yielded a high open circuit voltage of 992 V, short circuit current of 44.8 μA and power density of 26 W m−2. Experimental and theoretical investigations reveal that the enhancing effect of EDL on TENG output is proportional to surface area of the double layer and hence the capacitance of SPE-TENG. More importantly, the SPE-TENG shows stable performance under ambient condition for long duration as it is free of the dehydration issue affecting other hydrogels-based ionic conductors. Furthermore, the SPE-TENG has been found to sustain high voltage output under large stretch, demonstrating robust energy harvesting even when the device undergoes large mechanical deformation. The potential of the newly developed SPE-TENG in harvesting biomechanical motion energy of human body is demonstrated for powering wearable electronics without external power supply. The stretchable SPE-TENG shows excellent energy harvesting capability and overcomes the liquid evaporation induced performance degradation in ion conducting hydrogels, suggesting very promising practical applications in stretchable energy harvesters and self-powered stretchable sensors.