Multiphase Coherent Nanointerface Network Enhances Thermoelectric Performance for Efficient Energy Conversion and Contactless Thermosensation Applications in GeTe

Abstract Counter doping is a prevalent strategy to optimize the excessively high carrier concentration in GeTe, while it may impair carrier transport and reduce mobility, thereby limiting the potential to improve ZT . Herein, a novel approach to overcome this challenge is proposed. A multiphase coherent nanointerface network, formed between pseudo‐cubic GeTe, Cu 2 Te, and PbTe phases, with effective Cu ions delocalization, has been realized in Cu 2 Te alloyed Ge 0.84 Cd 0.06 Pb 0.10 Te. This design selectively modulates both charge carrier and phonon transport, resulting in increased mobility and optimized carrier concentration that contribute to enhanced power factor, with an ultra‐low lattice thermal conductivity of ≈0.33 W m −1 K −1 at 653 K. Consequently, the peak ZT of ≈2.22 at 803 K and average ZT of ≈1.40 from 303 to 803 K is achieved in (Ge 0.84 Cd 0.06 Pb 0.10 Te) 0.99 (Cu 2 Te) 0.01 . Furthermore, the novel structural modulation results in robust mechanical properties. Utilizing these optimized materials, achieving a high power density of ≈1.47 W cm −2 at a temperature difference of 400 K in the fabricated 7‐pair thermoelectric module. Moreover, a thermoelectric energy harvesting array device is assembled, exhibiting potential for applications in non‐radiative energy harvesting from lasers and touchless thermosensation, further advancing the applications of thermoelectric materials and devices.