Engineering the p-n switch: Mastering intrinsic point defects in Sb2Te3-dominant alloys

VVI-based alloys have long been established as the sole commercial material system for solid-state cooling. However, the volatility of the Se element in conventional n-type BiTeSe leads to inconsistent reproducibility across production batches. Here, we unveil an innovative, highly reproducible n-type BiSbTe alloy, realized through strategic manipulation of native point defect. The initial BiSbTe is saturated with antisite defects, imbuing it with pronounced p-type conductivity. Our investigation, underpinned by the electronegativity and atomic size model and validated through density functional theory calculation, reveals that the replacement of Sb by In in the BiSbInTe system effectively elevates the formation energy of negatively charged antisite defect, while simultaneously diminishing that of positively charged anion vacancy. This alteration in the dominant point defect type catalyzes a p-n type transition, prominently observed at around x = 0.15. We believe this constitutes the inaugural disclosure of a n-type SbTe-rich bulk material. The observed low zT ∼ 0.16 at 360 K in n-type BiSbInTe, attributed to low electron mobility, is a focal point for ongoing performance enhancement efforts. These results not only enrich the comprehension of intrinsic point defect manipulation in the VVI system, but also pave the way for the systematic evolution and realization of innovative, high-efficiency, and consistently reproducible n-type BiSbTe alloys.