Module-scale silicon 3D softened nanoarchitectures for eco-friendly thermoelectric energy harvesting

Widespread of internet-of-things with wireless sensing and transmission devices require self-powering module consisting of abundant and environmental-friendly materials. Si thermoelectric material is a promising candidate and sufficient figure of merit ($zT$) has been realized in the form of nanoscale derivatives. However, scaling it up to bulk material while maintaining the $zT$ has been challenging. This difficulty arises from the lack of scalable nanostructures that effectively impede phonon transport without significantly sacrificing electron transport in the bulk process, which is rooted in the intrinsic trade-off between electrical and thermal transport mechanisms. To overcome this limitation, this study introduces a scalable 3D softened nanoarchitecture by a highly non-equilibrium sintering process, featuring narrow-conduction path between nanograins, which facilitates selective electron/phonon interface transmission due to the induced significant strain. This strain engineering results in remarkable $zT$ values for both n- and p-type bulk 3D Si nanoarchitectures (0.11–0.23 at room temperature and 0.44–0.67 about 750 K), which are 5–10 times those of previously reported bulk nanostructured Si materials. The superior $zT$ and scalability enables integrating the Si thermoelectric materials into a flexible module and realized powering wireless sensor devices for 24 h.