Insight into NaSiCl₃: a lead-free perovskite for the next generation revealed by DFT and SCAPS-1D

This study theoretically explores the potential of lead-free NaSiCl₃, a chloride-based perovskite, highlighting its potential as an efficient photovoltaic absorber. Using density functional theory (DFT) calculations via WIEN2k and CASTEP, alongside SCAPS-1D simulations, we assess the material's suitability from both atomic and device perspectives. The results confirm that NaSiCl₃ is structurally, thermodynamically, dynamically (via phonon dispersion), and mechanically stable. In-depth electronic, optical, and thermoelectric analyses further reinforce the suitability of these materials for high-performance optoelectronic applications. NaSiCl₃ exhibits an indirect bandgap of 0.869 eV (PBE-GGA + TB-mBJ) and 1.307 eV (HSE06), with the latter aligning well with optimal values for efficient solar energy harvesting. Its potential as a solar absorber is highlighted by its wide absorption range across the visible (VIS) and ultra-visible (UV) spectra as well as its advantageous optical constants. Furthermore, thermoelectric evaluations reveal strong performance at elevated temperatures, expanding its utility in high-temperature optoelectronic devices. Based on these DFT insights, a planar n-i-p perovskite solar cell incorporating NaSiCl₃ was modeled in SCAPS-1D. Among the eight tested architectures, the FTO/SnS/NaSiCl₃/Zn₃P₂/Ni configuration yielded a maximum power conversion efficiency (PCE) of 27.11%. These findings not only establish NaSiCl₃ as a highly promising, lead-free perovskite for next-generation solar cells but also provide a strong theoretical basis to guide future experimental synthesis and device fabrication.