Exploring the structural, electronic, elastic, optical and thermoelectric properties of silver-based half-Heusler semiconductors AgYTe (Y = Li, Na, and K)

Abstract

In this research, we explore the properties of AgYTe (where Y = Li, Na, and K) half-Heusler compounds using density functional theory and semi-classical Boltzmann transport theory. The goal is to identify new materials better suited for optoelectronic and thermoelectric applications. Electronic property results implemented by the TB-mBJ potential indicate that AgYTe compounds exhibit direct bandgap semiconductor behavior, with bandgap values of 1.73 eV, 1.71 eV, and 1.59 eV for AgKTe, AgLiTe, and AgNaTe, respectively. The negative values acquired for both formation and cohesive energies underscore the energetic and dynamic stability exhibited by these alloys. Additionally, they demonstrate stability under shape deformation as they fully satisfy the Born elastic stability criteria. Optical calculations suggest that AgYTe half-Heusler alloys are active across a broad range of the electromagnetic spectrum, making them suitable for optoelectronic applications. Both AgLiTe and AgNaTe exhibit high absorption coefficients of approximately 80.104 cm−1 in the visible range and around 142 × 104 cm−1 in the near UV. In contrast, AgKTe shows maximum absorption in the far-UV, reaching 181 × 104 cm−1 at 23 eV. AgNaTe exhibits high reflectivity, exceeding 73 % in the near-infrared region, while AgLiTe shows 68 % reflectivity in the ultraviolet region, making them effective in these areas. The high values found for the Seebeck coefficients, electrical conductivity, and power factor are ideal for thermoelectric power generation applications and thermoelectric coolers.