Radiative-cooled hierarchical wearable thermoelectric generator: A nexus of thermal, electrical, and mechanical synergy

<h2>Abstract</h2> Wearable thermoelectric generators (TEGs) offer a promising route toward self-powered, body-integrated electronics. However, conventional sandwich-structured TEGs (s-TEGs) suffer from inherent limitations due to degraded thermal and electrical performance under device-level mechanical flexibilization, making it challenging to simultaneously achieve high voltage, high power output, and stretchability, particularly in outdoor environments with heat-exchange complexities. Here, we present a hierarchical-morphology TEG (h-TEG) that integrates high-aspect-ratio thermoelectric (TE) couples, high-packing-density TE chiplets, and a stretchable architecture embedded in low-thermal conductivity, ultrasoft elastomers. A flexible nanofibrous radiative cooling (RC) metasurface, spectrally engineered for facilitating thermal emission and solar irradiation rejection, is further incorporated to enhance device performance. By decoupling TE and mechanical functionalities, the h-TEG delivers consistently high performance in voltage density (6.67 mV cm⁻² K⁻¹), power density (9.59 μW cm⁻² K⁻¹), and stretchability (up to 120%), effectively overcoming the trade-offs typical of s-TEGs. This hierarchical integration ensures stability across diverse thermal environments, while the h-TEG with RC achieves 3- and 8-fold higher power and voltage, respectively, compared with conventional s-TEGs with RC, even under strong solar irradiation (∼900 W m⁻²) and high ambient temperature (33°C). The hierarchical strategy paves the way toward next-generation TEGs with synergistically high output performance and mechanical adaptability.