Pressure-induced band gap engineering and optoelectronic transition in lead-free perovskites AGeF ₃ (A = Cs, Rb): toward visible-light driven photocatalysis and optoelectronic applications

Lead-free metal halide perovskites have attracted significant interest for solar energy conversion and other optoelectronic applications. This study uses hydrostatic pressure-based investigations based on density function theory (DFT) to analyse the optoelectronic properties of AGeF 3 (A = Cs, Rb). DFT was utilised to investigate the structural, electronic, optical, thermodynamic, and mechanical characteristics of AGeF 3 . As seen by the pressure impact on the band structure, the valence band and conduction band overlap, making it simple for photoelectrons to move from the valence band to the conduction band. This effect leads to improved absorption, conductivity, and other optical properties. The examined optical characteristics demonstrate increased absorbance under pressure, exceeding ambient conditions, throughout the visible and ultraviolet ranges. Particularly, the conductivity, dielectric constant, and decreased reflectivity have high-intensity peak values in the visible zones. AGeF 3 exhibits a decreasing band gap and improved characteristics at low hydrostatic pressure, according to the thorough examination of its structural, optical, and electronic properties. Both materials are mechanically and thermodynamically stable under hydrostatic pressure and ductile in nature. AGeF 3 possesses favourable band edge positions, which are essential for photocatalytic dye degradation and hydrogen generation through water splitting.