Electronic Structure and Optical Response of Cs₂AgSbBr₆: A Lead-Free Double Perovskite for Sustainable Photovoltaics

In photovoltaics applications, lead-free double-halide perovskites are attracting increasing attention as a sustainable replacement for lead-based perovskites. This article investigates the behaviour of photons and electrons by using a computer code called CASTEP. The calculation results show an indirect band gap of 1.361 eV, which places this substance in an energy range suitable for solar-energy conversion. The energy band structure shows that the carrier mobility is asymmetric, meaning that electrons are lighter and holes are heavier. A detailed examination of the band edge energy levels reveals that the valence band is controlled by a mixture of Ag-Br hybridization, and the conduction band is controlled by a combination of Sb-p hybridisation. There were no deficiencies in the middle band. The absorption of visible light begins at the band gap, is followed by moderate absorption, and then low reflectivity with a relatively high static refractive index. These results suggest that Cs₂AgSbBr₆ is a promising lead-free optoelectronic and photovoltaic material.