Wearable thermoelectric generators provide a reliable power generation method for self-powered wearable electronic devices. However, there has been a lack of research regarding the comfort of wearable thermoelectric generators. Here we propose a design for a comfortable wearable thermoelectric generators system with high output power based on sandwiched thermoelectric model. This model paves the way for simultaneously optimizing comfort (skin temperature and pressure perception) and output power by systematically considering a variety of thermal resistive environments and bending states, the properties of the thermoelectric and encapsulation materials, and the device structure. To verify this strategy, we fabricate wearable thermoelectric generators using Mg-based thermoelectric materials. These materials have great potential for replacing traditional Bi₂Te₃-based materials and enable our wearable thermoelectric generators with a power density of 18.4 μWcm⁻² under a wearing pressure of 0.8 kPa and with a skin temperature of 33 °C, ensuring the wearer’s comfort.

By the fine manipulation of the exceptional long-range germanium-telluride (Ge─Te) bonding through charge transfer engineering, we have achieved exceptional thermoelectric (TE) and mechanical properties in lead-free GeTe. This chemical bonding mechanism along with a semiordered zigzag nanostructure generates a notable increase of the average zT to a record value of ~1.73 in the temperature range of 323 to 773 K with ultrahigh maximum zT ~ 2.7. In addition, we significantly enhanced the Vickers microhardness numbers ( H _v ) to an extraordinarily high value of 247 H _v and effectively eliminated the thermal expansion fluctuation at the phase transition, which was problematic for application, by the present charge transfer engineering process and concomitant formation of microstructures. We further fabricated a single-leg TE generator and obtained a conversion efficiency of ~13.4% at the temperature difference of 463 K on a commercial instrument, which is located at the pinnacle of TE conversion.

Eco-friendly SnTe based thermoelectric materials are intensively studied recently as candidates to replace PbTe; yet the thermoelectric performance of SnTe is suppressed by its intrinsically high carrier concentration and high thermal conductivity. In this work, we confirm that the Ag and La co-doping can be applied to simultaneously enhance the power factor and reduce the thermal conductivity, contributing to a final promotion of figure of merit. On one hand, the carrier concentration and band offset between valence bands are concurrently reduced, promoting the power factor to a highest value of ∼2436 µW·m⁻¹·K⁻² at 873 K. On the other hand, lots of dislocations (∼3.16×10⁷ mm⁻²) associated with impurity precipitates are generated, resulting in the decline of thermal conductivity to a minimum value of 1.87 W·m⁻¹·K⁻¹ at 873 K. As a result, a substantial thermoelectric performance enhancement up to zT ≈ 1.0 at 873 K is obtained for the sample Sn_0.94Ag_0.09La_0.05Te, which is twice that of the pristine SnTe (zT ≈ 0.49 at 873 K). This strategy of synergistic manipulation of electronic band and microstructures via introducing rare earth elements could be applied to other systems to improve thermoelectric performance.

Introducing additional Sn into polycrystalline Ag₈SnSe₆ could manipulate self-defects and improve the crystallinity, and the peak ZT value is significantly improved.