Halide perovskites have garnered significant interest as advanced materials for optoelectronic applications and energy harvesting devices, owing to their adjustable bandgaps, elevated absorption coefficients, and exceptional charge transport characteristics. Among them, double perovskites of the less explored formula, specifically A₃BX₆-type halide double perovskites, remain relatively underrepresented in the literature. In this work, the structural, mechanical, thermodynamic, electronic, optical, and thermoelectrical properties of the lead-free halide perovskites A₃GaI₆ (A = Cs, K, Rb) were systematically investigated using first-principles calculations within the WIEN2k framework employing GGA-PBE, TB-mBJ, and TB-mBJ+SOC functionals. Structural stability was confirmed through Goldschmidt tolerance factors, negative formation energies, convex-hull analysis, and elastic constants. The calculated direct band gaps based on both functionals (TB-mBJ/TB-mBJ+SOC) of 2.06/1.88 eV (Cs₃GaI₆), 1.83/1.65 eV (K₃GaI₆), and 1.94/1.76 eV (Rb₃GaI₆) indicate strong optical absorption in the visible to near-infrared region. Carrier-density and Bader-charge analyses reveal that the Ga–I framework governs electronic transport, while the A-site cations tune the charge distribution, with K₃GaI₆ and Rb₃GaI₆ exhibiting higher carrier densities and stronger charge transfer than Cs₃GaI₆. Among the studied compounds, K₃GaI₆ possesses the most suitable band gap (∼1.65 eV), lower carrier effective masses, higher carrier mobilities, and a larger static dielectric constant, indicating efficient charge separation and transport, and thus superior photovoltaic potential. Based on DFT-derived parameters, SCAPS-1D simulations of sixteen n-i-p device architectures based on K₃GaI₆ yield power conversion efficiencies ranging from 19.48% to 22.48%, with the AZO/STO/K₃GaI₆/Zn₂P₂ configuration showing the best performance due to favorable band alignment and transport-layer properties. After optimization, the efficiency reaches 27.19%, highlighting K₃GaI₆ as a highly promising lead-free absorber for high-performance perovskite solar cells. This work establishes a direct link between material properties and device performance and provides a solid theoretical foundation for the experimental realization of A₃GaI₆-based optoelectronic and energy-harvesting applications.

Understanding solvent-induced crystallization and defect dynamics in hybrid perovskites is crucial for stable and high-efficiency solar cells. Here, we investigate the influence of DMF : DMSO solvent ratios on the nucleation, grain boundary passivation, and optoelectronic behaviors of MAPbI₃ thin films prepared under ambient conditions. X-ray diffraction and photoluminescence analyses reveal that increasing DMSO content promotes PbI₂ segregation, which passivates grain boundaries and modulates trap-assisted recombination. These structural and photophysical changes are correlated with carrier lifetimes using time-resolved photoluminescence measurements and the simulated device performance using SCAPS-1D. We find that a DMF : DMSO ratio of (6 : 4) enhances the interplay between crystalline order, the energy disorder (Urbach tail), and the charge transport. Our findings provide mechanistic insights into how solvent coordination controls defect landscapes and interface energetics in perovskite films, offering a framework for rational solvent design in ambient-stable photovoltaics.

The electrodeposition of Cu₂O thin films was systematically investigated by varying the chloride ion (Cl⁻) concentration in the electrolyte. Current-time transient analysis revealed an increase in the diffusion coefficient (D₀) from 2.09 × 10⁻⁷ cm² s⁻¹ at low Cl⁻ concentration to 3.72 × 10⁻⁶ cm² s⁻¹ at higher Cl⁻ levels, indicating enhanced mass transport and faster growth kinetics. Dimensionless current-time transients compared with the Scharifker-Hills model confirmed progressive nucleation across all conditions, with a decreasing nucleation rate (AN₀) from 21.685 × 10⁶ cm⁻² s⁻¹ to 4.790 × 10⁶ cm⁻² s⁻¹ as Cl⁻ concentration increased. Similarly, the saturation nucleation density (N_sat) declined from 16.980 × 10⁶ cm⁻² to 4.847 × 10⁶ cm⁻², suggesting that higher Cl⁻ concentrations favor larger grain formation by reducing the density of active nucleation sites. X-ray diffraction analysis confirmed the formation of single-phase cubic Cu₂O with a dominant (111) orientation across all samples, with crystallite sizes increasing from 62 nm to 94 nm as Cl⁻ concentration increased. These findings highlight the crucial role of electrolyte composition in controlling the nucleation and growth mechanisms of Cu₂O films, offering valuable insights for optimizing deposition parameters in optoelectronic and energy applications.