Thermoelectric generator using nanoporous silicon formed by metal-assisted chemical etching method

Abstract

Thermoelectric generators (TEGs) offer a promising solution for converting waste heat into electrical energy, addressing global energy challenges with their ability to operate without moving parts and under diverse environmental conditions. However, the adoption of TEGs is limited by the drawbacks of traditional materials like bismuth telluride, which are expensive and environmentally hazardous. Silicon-based TEGs, while abundant and compatible with semiconductor manufacturing, are characterized by low thermoelectric efficiency due to high thermal conductivity and complex fabrication. In this study, we explore the possibility to use nanoporous silicon, fabricated through a metal-assisted chemical etching (MACE) method, as a novel material for TEGs. Our hypothesis was that nanoporous structures would reduce thermal conductivity and enhance the Seebeck coefficient, thereby improving the figure of merit (ZT). Additionally, a spin-on dopant (SOD) technique was used to improve the contact resistance, and further enhance the device’s performance. This research presents the synthesis and detailed characterization of nanoporous silicon, with a focus on optimizing porosity and layer thickness. The effects of SOD treatment on the electrical properties are also evaluated. The fabricated nanoporous silicon-based micro-TEGs exhibited ZT values that were 4.2 times higher for n-type and 12.4 times larger for p-type compared to bulk silicon, achieving a maximum power density of 1.12 μW/cm². This performance significantly surpassed that of bulk silicon devices. These findings demonstrated the potential of nanoporous silicon as a viable material for next-generation thermoelectric applications, offering a scalable and more environmentally friendly alternative to traditional thermoelectric materials.