Investigation of the stable and non-toxic halide perovskite-inspired AgBiZ₄ (Z = Cl, Br, I) for photovoltaic applications

In this article, the structural, electronic, optical, and photovoltaic properties of lead-free perovskite-inspired halides AgBiX₂Y₂ (X/Y = Cl, Br, I) were investigated using density functional theory (DFT). The compounds were studied in the orthorhombic crystal structure with space group Imma. With the halogen substitution, the lattice constants increases and bulk moduli decreases. The compounds are found to be direct band gap semiconductors, with band gaps ranging from 1.51 to 2.53 eV using GGA + mBJ. The valence band is mainly influenced by the d-orbital of Ag, while the conduction band is dominated by the p-orbital of the Bi. Strong absorption in the visible spectrum makes AgBiX₂Y₂ promising candidates for optoelectronic applications such as solar cells, light-emitting devices and photodetectors. Compounds containing I and Br are high dielectric materials, confirming the potential of AgBiX₂Y₂ in energy-related technologies. The calculated power conversion efficiency (PCE) of AgBiI₄ in the design solar cell device FTO/WS₂/AgBiI₄/Spiro-MeOTAD/Cu is 19.6%. The quantum efficiency (QE) increases sharply from 300 nm, reaching a peak efficiency of 80–90% in the range of 350 nm to 800 nm, beyond this range the QE of AgBiI₄ rapidly decrease, shows the material absorption limit. The J-V and quantum efficiency spectra reveal that AgBiI₄ exhibits superior photovoltaic performance and higher quantum efficiency.