Cu-Doping-Driven Texture and Transport Anisotropy Engineering in n-type Bi2Te3-Based Thermoelectrics

Abstract

Bi2Te3-based alloys are the only commercially established thermoelectric materials for near-room-temperature applications, yet high-performance texturing of n-type alloys typically requires complex hot deformation, which can cause Te volatilization and performance instability. In this work, we demonstrate a facile Cu-doping strategy to simultaneously regulate carrier transport and enhance texture in Te-rich n-type Bi2Te2.9Se0.3 without post-deformation processing. Cu promotes preferential grain growth along the ab plane and strengthens c-axis orientation, while excess Cu forms Cu-Te secondary phases. Cu doping reverses the electrical conductivity anisotropy, while the enhanced in-plane Seebeck coefficient compensates for the reduced conductivity, yielding an improved power factor. Meanwhile, point defects and interfacial scattering suppress lattice thermal conductivity. Consequently, the optimized Cu0.03Bi2Te2.9Se0.3 achieves a peak in-plane zT of ~1.02 at 350 K and a room-temperature zT of 0.97, representing a ~140% enhancement over the pristine sample. A 7-pair device delivers a conversion efficiency of 5.1% at ΔT = 197 K. This work provides a simple, low-cost route to texture and transport optimization of n-type Bi2Te3-based thermoelectrics.