Comparative Theoretical Analysis of Structural, Electronic, Optical, and Thermoelectric Properties of Sodium‐Based Zinc Halide Perovskites for Photovoltaic Application

Abstract

Lead‐free halide perovskites have attracted significant attention as next‐generation materials for photovoltaic applications. In this work, Density Functional Theory (DFT) calculations were performed to investigate the structural, electronic, optical, thermoelectric, and photovoltaic performance of NaZnX3 (X = F, Cl, Br, and I) in its bulk and novel layer phases. The structural optimization confirms the formation of the cubic bulk phase and tetragonal layer phase, while phonon calculations indicate dynamical instability in bulk NaZnBr3 and NaZnI3. The GGA‐PBE electronic band structures, density of states, and electron density analyses reveal that all compounds exhibit indirect bandgap semiconducting nature with mixed ionic‐covalent bonding. The optical properties exhibit a large dielectric response, strong absorption, high optical conductivity, enhanced refractive index, and reflectivity in the ultraviolet region (6–10 eV). The thermoelectric results indicate that the layered phase possesses the highest thermoelectric figure of merit zT of 0.354 at 700 K for NaZnI3. SCAPS‐1D device simulations show that the Ni /n‐Si / a‐Si: H / P3HT/ NaZnF3/ Metal contact heterostructure achieves a maximum simulated power conversion efficiency of 32.58%.