<p>Utilizing semiconductor materials for solar-driven energy conversion is a promising approach for sustainable energy systems. In this regard, lead-free Ti-based perovskite-like materials have garnered attentiveness due to their structural stability and adjustable optoelectronic properties. This study examines the structural, electrical, optical, and photovoltaic properties of K₃Ti₂A₉ (A = Cl, Br, and I) by density functional theory. The computed findings demonstrate that these compounds display mechanical and thermodynamic stability, with structural properties aligning with available results. Analysis of the electronic structure reveals semiconducting properties characterized by band gaps of 1.86&#xa0;eV (Cl), 1.51&#xa0;eV (Br), and 1.07&#xa0;eV (I), indicating a systematic drop in band gap with halide substitution and improved absorption of visible light in the compounds. Device simulations utilizing SCAPS-1D were conducted to assess photovoltaic performance, incorporating various combinations of electron and hole transport layers. The optimized configuration (FTO/WS₂/K₃Ti₂A₉/CuI) demonstrates commendable performance, achieving power conversion efficiencies of 16.67% (Cl), 29.21% (Br), 27.73% (I), alongside advantageous values of Voc, Jsc, and fill factor, suggesting use in solar cell technology. Furthermore, band edge positions were evaluated to determine the thermodynamic viability of water-splitting redox processes. The findings indicate that these materials could meet the energetic demands for water oxidation and reduction; nevertheless, this constitutes an initial thermodynamic assessment rather than a forecast of catalytic performance. This study underscores K₃Ti₂A₉ perovskite-like compounds as viable lead-free alternatives for solar applications and elucidates the structure–property correlations in Ti-based halide systems.</p> Graphical abstract <p></p>