Tunable photovoltaic effects induced by pressure in cesium-based lead-free double perovskite Cs 2 AgXBr 6 (X = Bi, Ga, In)

Abstract Cesium-based lead-free double perovskites exhibit promising potential in optoelectronic devices and solar cells due to their remarkable stability and excellent photoelectric properties. Pressure regulation, as an effective strategy, can significantly modulate the structure and optoelectronic behavior of materials. Here, using first-principles calculations, we systematically explore their structural, electronic, optical, and photovoltaic properties under 0–20 GPa pressure. The materials remain structurally robust and thermodynamically stable under compression, while bandgaps decrease and carrier mobilities are markedly enhanced; notably, the hole mobility of Cs 2 AgBiBr 6 rises from 42.67 to 722.42 cm 2 ·V −1 ·s −1 . Pressure strongly modulates optical absorption, enhancing visible-light absorption for Cs 2 AgBiBr 6 , while the SLME of Cs 2 AgInBr 6 increases initially and then slightly decreases, with efficiencies remaining between 30.35% and 31.02%. These results demonstrate the tunable optoelectronic properties of Cs 2 Ag X Br 6 and their significant potential for stable, high-efficiency photovoltaic and optoelectronic applications.