Unravelling p–n Conduction Transition in High Thermoelectric Figure of Merit Gallium-Doped Bi₂Te₃ via Phase Diagram Engineering

We revisit the well-established Bi2Te3 via phase diagram engineering. Along with a phase diagram in hand, it is realized that the solubility of Ga in Bi2Te3 is coincident with the p–n transition zone in Ga–Bi2Te3 alloys. The best-performing n-type (Bi2Te3)0.93(Ga2Te5)0.07 possesses a peak zT ∼ 1.5 at 300 K, which is attributed to the reduced κ ∼ 1.8 W m–1 K–1 and the low-lying ρ. The p-type Bi1.99Ga0.01Te3 also exhibits a peak zT of 1.2 at 300 K. In other words, the addition of Ga leads to high-zT p-type or n-type bismuth-tellurides, which simplifies the conventional synthesis route that usually involves different dopants.