Electronic and thermal transport properties of two-dimensional penta-Pd2As4from first-principles calculations for thermoelectric and thermophotovoltaic applications.

Two-dimensional thermoelectric materials have gained considerable attention because of their potential for high energy-conversion efficiency and miniaturized device applications. In this work, the structural, thermal stability, and thermoelectric properties of a novel pentagonal Pd2As4monolayer are investigated using density functional theory. The optimized structure is found to be thermally stable and exhibits a direct band gap of 0.80 eV located in the infrared region. The lattice thermal conductivity (κl) is calculated to be 2.26 W/mK at room temperature 300 K and decreases to 1.0 W/mK at high temperature 700 K, indicating strong phonon scattering. Carrier relaxation times are estimated using the deformation potential theory of Bardeen and Shockley and subsequently employed within the Boltzmann transport framework to evaluate thermoelectric coefficients. A bipolar effect is identified at elevated temperatures due to the relatively small band gap. The combination of high power factor and low lattice thermal conductivity results in an enhanced thermoelectric figure of merit, with a maximum ZT of 3.0 for n-type doping and 1.2 for p-type doping. These findings demonstrate that penta-Pd2As4is a promising candidate for high-performance thermoelectric applications. Furthermore, the potential applicability of the investigated material for future thermophotovoltaic devices is also discussed.