Enormous enhancement of thermoelectric properties via piezo-gating effect

The thermoelectric effect is one of the most promising techniques to generate electricity from waste heat energy. The commonly adopted approaches to enhance the thermoelectric performance limit the power factor because of the contradictory behavior between the Seebeck coefficient and electrical conductivity. This hurdle can be overcome via piezo-gating effect, which can modify the electronic band structure of active materials through strain. In this study, we developed piezo-gated flexible transistor (PGFT) comprised of ZnO thin-film (TFPGFT) and ZnO nanowires (NWPGFT) on polyethylene terephthalate (PET) as a flexible substrate and demonstrate the simultaneous enhancement of the Seebeck coefficient and conductivity by incorporating piezo-gating effect. The TFPGFT shows a gauge factor of ∼115, much higher than NWPGFTs. Further, the TFPGFT shows a higher Seebeck coefficient enhancement ∼12 times (∼0.13 to ∼1.76 µV/K) under strain resulting from the dominating piezo-gating effect. Therefore, the synergistic piezo-gating and thermoelectric effect dramatically boosts the power factor of TFPGFT by approximately 400 times (from ∼0.36 mW/K2 to ∼140.3 mW/K2), which can improve the performance of thermoelectric devices to a new dimension. Finally, we propose a self-powered single-dimension strain sensor based on thermoelectric power, reaching a gauge factor of ∼16.