Strain Engineering in Ce–Sb Co-Doped Bi ₂ Te ₃ Enabling Ultrahigh Thermoelectric Performance

While bismuth telluride (Bi 2 Te 3 ) demonstrates excellent thermoelectric performance in p-type systems, its n-type variants are limited by the inherent conductivity-thermal conductivity trade-off. Here, we employ a dual-doping strategy that incorporates the rare earth element cerium (Ce) and antimony (Sb) to simultaneously optimize the electrical and thermal transport properties of n-type Bi 2 Te 3 . We demonstrate that Ce and Sb codoping serve as an effective electronic modifier, converting Bi 2 Te 3 to an n-type conductor while suppressing bipolar conduction through dynamic carrier concentration tuning, achieving an enhanced peak figure of merit ( zT ) of ∼0.93 at 473 K in Bi 2– x ( CeSb ) 2 x / 3 Te 3 ( x = 0.05) through improved power factor optimization. Moreover, Sb codoping not only enhances the carrier mobility through strain compensation but also significantly reduces the lattice thermal conductivity to 0.37 W m –1 K –1 at 480 K through synergistic mass fluctuation and strain field phonon scattering. The combined effects yield a 63% enhancement in zT compared to conventional In–Sb-doped systems. Importantly, this performance enhancement is achieved through a scalable synthesis process that maintains phase purity and materials design with structural stability. As a result, the optimized Bi 1.95 (CeSb) 0.033 Te 3 not only exhibits a higher peak zT value but also maintains high performance across both wearable (Δ T < 100 K) and industrial waste-heat recovery (400–500 K) temperature ranges. This work presents an approach for active strain engineering in the development of high-performance thermoelectric materials, surpassing traditional doping methods.