Electronic state reconstruction enabling high thermoelectric performance in Ti doped Sb2Te3 flexible thin films

Abstract

Sb₂Te₃-based thermoelectric (TE) thin-film generators are an attractive option for wearable electronics. Band engineering can effectively modulate TE performance. However, modulating the band structure of Sb₂Te₃ thin film remains a challenging task. In this work, titanium (Ti) doping effectively modifies the electronic band structure in Sb₂Te₃, optimizing both carrier transport and phonon transport performance. Ti-doping optimizes carrier concentration and resulting in an increase in electrical conductivity from 1420.0 S/cm to 1694.8 S/cm at 300 K. Additionally, Ti doping modulates the balance between the effective mass of charge carriers and carrier concentration, increasing Seebeck coefficient from 106.0 μV/K to 114.8 μV/K. Both enhancements lead to a peak power factor of 20.9 μW·cm^–1·K^–2. Moreover, Ti-induced vibrational modes have reduced the lattice thermal conductivity from 0.62 W·m^–1·K^–1 to 0.22 W·m^–1·K^–1, improving zT from 0.33 to 0.52 at 300 K. The films exhibit excellent flexibility, with an ultralow resistance change ratio (ΔR/R₀) of less than 7% after 1000 cycles at a 6 mm bending radius. The device achieves a maximum output power of 178.8 nW with a temperature gradient of 30 K in agreement with the finite element analysis, indicating significant potential for wearable electronics.