The paper explores the use of mixed organic-cation perovskites, specifically formamidinium (FA⁻) and methylammonium (MA⁺) cations in lead iodide perovskites (MAPbI₃), to enhance solar-light harvesting in photovoltaic devices. The authors demonstrate that combining FA⁻ and MA⁺ cations in the A position of the perovskite structure can extend the optical absorption into the red region, improving the short-circuit current density and overall device performance. This approach, not previously applied in perovskite-based solar cells, shows great potential for tuning the structural, electrical, and optoelectronic properties of light-harvesting materials. The study also reports the first use of 3D perovskites (MA)x(FA)1-xPbI3 (x=0–1) as light-harvesting pigments in mesoscopic solar cells, achieving a power conversion efficiency (PCE) of up to 14.9% under simulated AM1.5G sunlight. The results highlight the superior carrier-collection efficiency and longer exciton lifetime in the mixed-cation perovskite, which contribute to higher short-circuit photocurrents without compromising photovoltage.The paper explores the use of mixed organic-cation perovskites, specifically formamidinium (FA⁻) and methylammonium (MA⁺) cations in lead iodide perovskites (MAPbI₃), to enhance solar-light harvesting in photovoltaic devices. The authors demonstrate that combining FA⁻ and MA⁺ cations in the A position of the perovskite structure can extend the optical absorption into the red region, improving the short-circuit current density and overall device performance. This approach, not previously applied in perovskite-based solar cells, shows great potential for tuning the structural, electrical, and optoelectronic properties of light-harvesting materials. The study also reports the first use of 3D perovskites (MA)x(FA)1-xPbI3 (x=0–1) as light-harvesting pigments in mesoscopic solar cells, achieving a power conversion efficiency (PCE) of up to 14.9% under simulated AM1.5G sunlight. The results highlight the superior carrier-collection efficiency and longer exciton lifetime in the mixed-cation perovskite, which contribute to higher short-circuit photocurrents without compromising photovoltage.