Broad Temperature Plateau for High Thermoelectric Properties of n-Type Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub> by 3D Printing-Driven Defect Engineering
Qiujun Hu, Ding Luo, Junbiao Guo, Wenbin Qiu, Xiaoyong Wu, Lei Yang, Zhengshang Wang, Xudong Cui, Jun Tang
Abstract
High-energy-conversion Bi2Te3-based thermoelectric generators (TEGs) are needed to ensure that the assembled material has a high value of average figure of merit (ZTave). However, the inferior ZTave of the n-type leg severely restricts the large-scale applications of Bi2Te3-based TEGs. In this study, we achieved and reported a high peak ZT (1.33) of three-dimensional (3D)-printing n-type Bi2Te2.7Se0.3. In addition, a superior ZTave of 1.23 at a temperature ranging from 300 to 500 K was achieved. The high value of ZTave was obtained by synergistically optimizing the electronic- and phonon-transport properties using the 3D-printing-driven defect engineering. The nonequilibrium solidification mechanism facilitated the multiscale defects formed during the 3D-printed process. Among the defects formed, the nanotwins triggered the energy-filtering effect, thus enhancing the Seebeck coefficient at a temperature range of 300–500 K. The effective scattering of wide-frequency phonons by multiscale defects reduced the lattice thermal conductivity close to the theoretical minimum of ∼0.35 W m–1 k–1. Given the advantages of 3D printing in freeform device shapes, we assembled and measured bionic honeycomb-shaped single-leg TEGs, exhibiting a record-high energy conversion efficiency (10.2%). This work demonstrates the great potential of defect engineering driven by selective laser melting 3D-printing technology for the rational design of advanced n-type Bi2Te2.7Se0.3 thermoelectric material.