Optoelectronic and thermoelectric properties of novel double halide perovskites Na2AgAsX6 (X = Cl, Br) for efficient green solar cells

Abstract

Inorganic lead-free double halide perovskites have emerged as promising materials in photovoltaic and renewable energy applications. This study investigates the optoelectronic and thermoelectric properties of novel inorganic lead-free double halide perovskite Na2AgAsX6 (X = Cl, Br) materials using accurate PBEsol and nKTB-mBJ schemes within the powerful full potential linear augmented plane wave (FP-LAPW) method. Structural ground state parameters were optimized, and the structural stability of these materials was assessed by evaluating their formation energy, phonon frequencies, and tolerance factor. Analysis of the electronic structure reveals that Na2AgAsX6 exhibit an indirect gap character, with energy values of 2.0 (for Cl) and 1.29 eV (for Br). Additionally, we computed various optical properties including dielectric functions (ε1, ε2), absorption coefficient (α), refractive index (n), extinction coefficient (k), and reflectivity (R), demonstrating a broad absorption spectrum spanning from visible to ultraviolet wavelengths. Furthermore, the investigation extends to determine the electronic transport properties—Seebeck coefficient (S), electrical conductivity (σ/τ), power factor (PF), thermal conductivity (κe/τ), and figure of merit (ZT) for Na2AgAsX6 (X = Cl, Br), using BoltzTraP code. These findings underscore the substantial potential of Na2AgAsX6 (X = Cl, Br) halide perovskites as efficient light absorption layers in the development of high-performance perovskite solar cells (PCSs) and also hold promise for future eco-friendly thermoelectric generator applications.