Halide engineering of GaBeX3 (X = F, Cl, Br, I) perovskites for tunable UV-to-visible photovoltaic applications

Density functional theory (DFT) at the B3LYP/LanL08 level was employed to investigate the structural, optoelectronic, thermal, and spectral properties of GaBeX 3 (X = F, Cl, Br, I) perovskites. All compounds are structurally stable, and X-site anion substitution effectively tunes their photovoltaic characteristics. The band gap decreases from 2.40 eV (F) to 1.05 eV (I), enhancing visible-light absorption. GaBeI 3 exhibits a HOMO-LUMO gap within the Shockley-Queisser-compatible range (0.9–1.6 eV), along with high polarizability (97.43 a.u.) and strong absorption, suggesting promising potential for photovoltaic applications. Reactivity indices provide insight into chemical behavior. Thermodynamic stability follows the formation energy trend: GaBeF 3 < GaBeCl 3 < GaBeBr 3 < GaBeI 3 . TD-DFT absorption spectra reveal exceptional UV absorption, making these materials ideal for UV optical devices. The combination of strong UV response and compositional tunability positions GaBeX 3 perovskites as highly attractive for tailor-made optical applications.