Enhanced Band-Crystal Engineering Drives Superior Power Generation in GeTe

Optimizing both electrical and thermal performance in thermoelectric (TE) materials is challenging due to the inherent coupling between carrier and phonon transport. To address this, targeted modulation of band structure and crystal lattice is achieved in the optimized Ge_0.885Zr_0.02Pb_0.08Te_0.985(Cu₂Te)_0.015 sample. Zr/Pb incorporation optimizes the band structure and significantly enhances the Seebeck coefficient, while Pb-substituted Ge sites occupy a more symmetric geometric center, reducing Ge vacancies, increasing crystal symmetry, and facilitating delocalized carrier transport. This leads to optimized carrier-weighted mobility (µ_w) ≈210 cm² V^-1 S^-1 (average power factor ≈30.3 µW cm^-1 K^-2). Moreover, the alteration of this geometric center enhances phonon anharmonicity, and multi-scale defect structures induced by multi-element doping provide abundant phonon scattering sources. Consequently, the sample exhibits significantly improved µ_w/κ_L values over pristine GeTe across the entire temperature range, with an improvement of ≈238% at 650 K. A peak zT of ≈2.2 at 650 K translates to a maximum heat-to-electricity conversion efficiency of up to 8.5% for a 7-pair device at ΔT = 366 K. This work further reveals the potential of synergistic band and crystal control engineering in decoupling carrier and phonon transport in GeTe-based materials, paving the way for broader applications of GeTe-based TE devices.