Two-dimensional \b{eta}-phase copper iodide: a promising candidate for low-temperature thermoelectric applications

Abstract

Bismuth telluride-based materials is the only commercially viable room-temperature thermoelectric material, despite its limited tellurium and poor mechanical properties. The search for materials with a high figure of merit (zT > 1.00) near room temperature remains a major challenge. In this work, we systematically investigate the structural stability and the thermoelectric capabilities of monolayer \b{eta}-CuI and {\gamma}-CuI through the density functional theory (DFT) combined with Boltzmann transport theory. Based on the thermoelectric transport coefficients of monolayer \b{eta}-CuI and {\gamma}-CuI, we predict their zT values will vary with carrier concentration and increase with temperature. Comparing the zT values, monolayer \b{eta}-CuI demonstrates superior thermoelectric properties compared to {\gamma}-CuI. At room temperature, the optimal zT values of monolayer \b{eta}-CuI exceed 1.50, with particularly high values of 2.98 (p-type) and 4.10 (n-type) along the Zigzag direction, demonstrating significant anisotropy. These results suggest the great potential of the monolayer \b{eta}-CuI is promising candidate materials for low temperature thermoelectric applications.