Design and Computational Screening of Be3PX3 (X = F, Cl, Br) Lead-Free Halide Perovskites for Next-Generation Optoelectronic and Water Splitting Applications via DFT and AIMD approach

Inorganic, lead-free halide perovskites have emerged as promising alternatives for next-generation photovoltaic and optoelectronic applications due to their environmental friendliness and tunable physical properties. In this work, a comprehensive first-principles investigation of Be ₃ PX ₃ (X = F, Cl, Br) perovskites is performed using density functional theory (DFT) within the CASTEP framework to explore their structural, electronic, optical, and photocatalytic properties. The optimized structures confirm mechanical and thermodynamic stability, with lattice parameters increasing systematically from F to Br. Electronic band structure analysis reveals indirect band gaps of 4.59 eV, 1.01 eV, and 0.29 eV (HSE06) for Be ₃ PF ₃ , Be ₃ PCl ₃ , and Be ₃ PBr ₃ , respectively, indicating strong tunability across the series. The calculated effective masses (0.04–0.09 \(\:{m}_{0}\)) suggest excellent carrier transport properties, further supported by low exciton binding energies (11.0–2.1 meV), which facilitate efficient charge separation. The combined tunability of band gap, optical response, and carrier dynamics suggests that Be ₃ PX ₃ (X = F, Cl, Br) compounds are promising candidates for optoelectronic applications, particularly in ultraviolet-to-visible photonic devices. Additionally, the band-edge alignment of Be ₃ PF ₃ indicates potential suitability for photocatalytic applications, although further detailed investigations are required to confirm this behavior. Furthermore, the materials exhibit good mechanical stability and low thermal conductivity, indicating suitability for robust device applications. The combined tunability of band gap, optical response, and carrier dynamics highlights Be ₃ PX ₃ compounds as promising candidates for next-generation photovoltaics, optoelectronics, and photocatalytic systems.