Sn<italic><sub>x</sub></italic>Se<italic><sub>y</sub></italic>: New promising thermoelectric materials

<p indent="0mm">Traditional fossil fuels, which are finite and have high thermal losses, necessitate the development of new energy materials for waste heat recovery. As the world continues to grapple with energy shortages and environmental concerns, finding sustainable and efficient energy solutions has become a priority. Among these solutions, thermoelectric materials have gained significant attention over the past few decades due to their unique properties. These materials stand out because of their modularity and noiseless operation, making them promising candidates for power generation and refrigeration. The efficiency of thermoelectric materials is primarily determined by the dimensionless figure of merit (<italic>ZT</italic>), which is a measure of a material’s ability to convert heat into electricity. <italic>ZT</italic> depends on three key parameters: The Seebeck coefficient, electrical conductivity, and thermal conductivity. Achieving high <italic>ZT</italic> values is essential for the practical application of thermoelectric materials. High <italic>ZT</italic> values require materials that exhibit both low thermal conductivity and high electrical conductivity. However, this is a challenging issue to achieve. Metals, which typically have high electrical conductivity, also have high thermal conductivity, making them less efficient for thermoelectric applications. On the other hand, ceramics, which have low thermal conductivity, generally suffer from poor electrical performance. In the search for ideal thermoelectric materials, researchers have turned their attention to elements that are abundant in the Earth’s crust, such as tin (Sn) and selenium (Se). These elements not only are plentiful but also exhibit properties that are conducive to thermoelectric applications. One compound that has been extensively studied is tin selenide (SnSe). SnSe has garnered interest due to its remarkable thermoelectric performance, particularly in its p-type semiconductor form. It has been reported to have a high <italic>ZT</italic> value of 2.6 at <sc>923 K,</sc> making it one of the most promising thermoelectric materials discovered to date. In addition to SnSe, tin diselenide (SnSe₂) is an n-type semiconductor that has shown potential for thermoelectric applications. Recent research indicates that SnSe₂ has achieved <italic>ZT</italic> values of up to 0.8. Moreover, the combination of SnSe and SnSe₂ in the form of SnSe-SnSe₂ composites has been explored as a way to optimize thermoelectric performance. These composites leverage the advantages of both materials, achieving lower thermal conductivity and enhanced electrical transport properties. Another compound that has emerged as a potential thermoelectric material is Sn₂Se₃, which consists of a 1:1 ratio of SnSe and SnSe₂. Both computational and experimental studies suggest that Sn₂Se₃ is a unique phase distinct from a simple mixture of SnSe and SnSe₂. The band structure and thermoelectric properties of Sn₂Se₃ have been analyzed, revealing potential <italic>ZT</italic> values of around 1.0 for both three-dimensional (3D) and one-dimensional (1D) forms. These findings indicate that Sn₂Se₃ could be a valuable addition to the family of thermoelectric materials. Furthermore, researchers investigated the effects of doping Sn₂Se₃ with elements such as titanium (Ti) and aluminum (Al) to enhance its properties. Doping can improve the stability and electrical resistance of Sn₂Se₃, making it more suitable for practical applications. Relative research has shown that Ti and Al doping can enhance the phase change properties of Sn₂Se₃, potentially leading to higher performance and greater stability. Despite the significant progress made in the development of Sn<italic>_x</italic>Se<italic>_y</italic> compounds for thermoelectric applications, several challenges remain. One of the primary challenges is the synthesis of these materials with consistent properties. Ensuring the stability of the materials is also crucial. Future research should focus on addressing these challenges to unlock the full potential of Sn₂Se₃ and other Sn<italic>_x</italic>Se<italic>_y</italic> compounds as low-cost, high-performance thermoelectric materials.