Abstract:

GeTe-based materials have attracted significant attention as high-efficiency thermoelectric materials for mid-temperature applications. However, GeTe thin-film materials with thermoelectric performances comparable to that of their bulk counterparts have not yet been reported, because of their unsatisfactory electrical and thermal properties caused by their poor crystal quality and high carrier concentration. Herein, a series of Sb-doped GeTe films and devices with remarkable thermoelectric performances are presented. These films are prepared through magnetron sputtering deposition at 553 K and exhibit a unique microstructure that consists of coarse- and fine-sized grains with high crystallization quality. The fine grains enhance the scattering associated with phonon transport and the coarse grains provide electron transport channels, which can suppress the thermal conductivity without obviously sacrificing the electrical conductivity. Moreover, Sb doping can effectively optimize the carrier concentration and increase the carrier effective mass, while introducing point defects and stacking faults to further scatter the phonon transport and decrease the thermal conductivity. Consequently, a peak power factor of 22.37 μW cm⁻¹ K⁻² is obtained at 703 K and a maximum thermoelectric figure of merit of 1.53 is achieved at 673 K, which are substantially larger than the values reported in the existing literature. A flexible thermoelectric generator is designed and fabricated using Sb-doped GeTe films deposited on polyimide and achieves a maximum output power density of 2.22 × 10³ W m⁻² for a temperature difference of 300 K.

Key words: Thermoelectric thin film, GeTe-based materials, Sb doping, Carrier concentration, Thermoelectric generator