3D-Printed functionally graded thermoelectric materials for enhanced power generation

Functionally graded materials (FGMs) are heterogeneous, with compositions that vary spatially with respect to their dopant concentrations and structures. FGMs are designed to exhibit the desired properties and functionalities for various target applications. Recently, 3D printing has emerged as a promising method for fabricating FGMs with complex customized geometries and precise distributions of materials. However, the use of 3D printing to fabricate FGMs is generally limited to producing structural materials, and their application to energy and electronic materials remains relatively rare. Thermoelectric power generation is regarded as a unique solution to recover waste heat; however, the strong temperature dependence of suitably efficient materials restricts their widespread application. Herein, we report a sequential 3D printing method for fabricating n-type Bi2Te2.7Se0.3 thermoelectric materials with electronic dopant and structural void gradients. The formulation of Na-doped Bi2Te2.7Se0.3 particle colloid inks with the desired viscoelasiticity for 3D printing enabled the fabrication of materials with complex architectures and a precision of 150 mu m. These materials incorporated atomic doping and macroscopic void gradients. The thermoelectric peak temperatures of the printed materials varied from room temperature to 450 K, depending on the doping concentration. The graded thermoelectric materials were designed to have a wide operable temperature window and was fabricated by 3D printing, thereby enabling the fabricated devices to deliver enhanced power-generating performance compared with that of devices based on the homogeneous material. The proposed method enables rapid and cost-effective production of functionally graded thermoelectric materials with applications in energy and electronic devices.