Thermoelectric generators (TEGs) are an excellent candidate for powering wearable electronics and the “Internet of Things,” due to their capability of directly converting heat to electrical energy. Here, we report a high-performance wearable TEG with superior stretchability, self-healability, recyclability, and Lego-like reconfigurability, by combining modular thermoelectric chips, dynamic covalent polyimine, and flowable liquid-metal electrical wiring in a mechanical architecture design of “soft motherboard-rigid plugin modules.” A record-high open-circuit voltage among flexible TEGs is achieved, reaching 1 V/cm2 at a temperature difference of 95 K. Furthermore, this TEG is integrated with a wavelength-selective metamaterial film on the cold side, leading to greatly improved device performance under solar irradiation, which is critically important for wearable energy harvesting during outdoor activities. The optimal properties and design concepts of TEGs reported here can pave the way for delivering the next-generation high-performance, adaptable, customizable, durable, economical, and eco-friendly energy-harvesting devices with wide applications.

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It is generally believed that filling atoms randomly and uniformly distribute in caged crystals, such as skutterudite compounds. Here, we report first-principles and experimental discovery of a multiscale filling-fraction fluctuation in the RFe_{4}Sb_{12} system. La_{0.8}Ti_{0.1}Ga_{0.1}Fe_{4}Sb_{12} spontaneously separates into La-rich and La-poor skutterudite phases, leading to multiscale strain field fluctuations. As a result, glasslike ultralow lattice thermal conductivity approaching the theoretical minimum is achieved, mainly due to strain field scattering of high-energy phonons. These findings reveal that an uneven distribution of filling atoms is efficient to further reduce the lattice thermal conductivity of caged crystals.