Defect-Driven Thermoelectric Performance in Disordered Cd-Doped AgSbTe₂

With an increasing demand for efficient and environmentally friendly energy conversion technologies, thermoelectric materials play a pivotal role in harnessing waste heat for power generation. In this work, we focus on enhancing the thermoelectric performance of AgSbTe₂, a well-known high-performance material that has garnered significant attention for its exceptional performance in mid-temperature range applications.¹ Previous works showed the high ZT could be further improved by Cd-doping to achieve a maximum ZT of 2.6 at 573 K.² This improvement in performance was attributed to cationic ordering and tuning of the disorder in the material. This study presents a comprehensive experimental and theoretical investigation of the thermoelectric properties of cadmium-doped silver antimony telluride (Cd-doped AST).<br/><br/>Single-phase Cd-doped AST samples were successfully synthesised, exhibiting notably high-power factor values. Remarkably, a peak power factor of ∼ 20 μWcm^-1K^-2 was achieved, demonstrating the material's exceptional electrical conductivity. Furthermore, thermal conductivities as low as 0.5 Wm-1K^-1 were observed at 330 K. This research also investigates the influence of growing under silver and tellurium poor conditions.<br/><br/>Employing first-principles hybrid-density functional theory (DFT) calculations and techniques like cluster expansion, we elucidate the true ground-state structure of the system and investigate the role of disorder in the system. With this ground-state, we are able to systematically analyse the defect landscape within AgSbTe₂. By quantifying the concentration and distribution of defects, we unveil their effect on the crystal lattice structure and electronic band structure. The impact of Cd-doping on the electronic band structure can then be analysed to understand the underlying mechanisms responsible for the observed changes in thermoelectric performance.<br/><br/>By understanding the interplay between disorder-induced defects and thermoelectric performance, we aim to pave the way for the design and optimisation of advanced thermoelectric materials for efficient energy conversion applications. The combined experimental and theoretical approach offers a robust framework for the design and optimisation of thermoelectric materials contributing to the advancement of sustainable energy technologies.<br/><br/><b>References</b><br/><br/>[1] Y. Zhang, Z. Li, S. Singh, A. Nozariasbmarz, W. Li, A. Genç, Y. Xia, L. Zheng, S. H. Lee, S. K. Karan, G. K. Goyal, N. Liu, S. M. Mohan, Z. Mao, A. Cabot, C. Wolverton, B. Poudel and S. Priya, <i>Adv. Mater.</i>, 2023, <b>35</b>, 2208994.<br/>[2] N. Cheng, R. Liu, S. Bai, X. Shi and L. Chen, <i>J. Appl. Phys.</i>, 2014, <b>115</b>, 163705.