Synergistic Optimization of Electronic and Thermal Properties in Single-Stage GeTe Thermoelectric Devices

Thermoelectric generators offer a promising route for converting low-grade waste heat into electricity; however, their practical deployment remains limited by their low conversion efficiency (η). Herein, we report a monolithic, single-stage, 7-pair device based on lead-free GeTe alloys that achieves a remarkable η of 14.1% and a power density of 2.19 W cm^-2 at a temperature difference of 460 K. This breakthrough stems from the synergistic integration of ordered-disordered state modulation and multiband engineering. Specifically, multiband evolution suppresses intervalley scattering while promoting valence-band convergence, optimizing the balance between the carrier effective mass and mobility to elevate the weighted mobility and average power factor. The concurrent introduction of abundant lattice defects and localized disorder drives the lattice thermal conductivity toward the amorphous limit. Consequently, achieving a maximum ZT of 2.6 at 703 K with an average ZT of 1.7 across 303-803 K is realized. This study establishes a promising design paradigm for high-performance lead-free thermoelectric technologies.