Characterization and modulation of the thermoelectric properties of 2D materials: Bi2O2Se and PdPS

• Main Author: Yip, Weng Hou
• Other Authors: Tay Beng Kang
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Engineering; Thermoelectric
• Online Access: https://hdl.handle.net/10356/181939
• Institution: Nanyang Technological University

The conversion of waste heat into useful energy has become increasingly critical in addressing global energy efficiency and environmental challenges. Over 60% of industrial energy consumption is lost as waste heat, necessitating the development of efficient thermoelectric (TE) materials that can reclaim this energy. This thesis investigates the enhancement of TE properties in intercalated two-dimensional (2D) materials, with a particular focus on bismuth oxyselenide (Bi₂O₂Se) and palladium phosphorus-sulfur (PdPS). Bi₂O₂Se, a layered material with promising TE properties, is studied extensively. A non-corrosive polystyrene-assisted transfer method is developed to handle Bi₂O₂Se, avoiding the detrimental effects of hydrofluoric acid used in traditional methods. The fabrication process includes precise steps such as electron-beam lithography and wire bonding, essential for creating high-quality TE devices. The TE performance of few-layer Bi₂O₂Se is demonstrated near room temperature, showing significant potential for practical applications. The thesis further explores the thickness-dependent TE properties of PdPS, a novel 2D material. Systematic studies reveal the effects of layer thickness on electrical and TE performance over a wide temperature range (20 - 380 K). Additionally, the intercalation of lithium ions (Li⁺) into PdPS is examined, highlighting how intercalation improves the material's TE properties. Experimental results indicate that both Bi₂O₂Se and PdPS exhibit enhanced TE performance, making them strong candidates for next-generation TE applications. The findings contribute to the broader field of energy conversion, providing insights into the development of efficient materials for harvesting waste heat.