This study investigates the use of zinc additives, specifically zinc trifluoromethane sulfonate (Zn(OOSCF₃)₂), to control iodide defects in perovskite solar cells, which are critical for improving device efficiency and stability. The introduction of Zn(OOSCF₃)₂ in the perovskite solution suppresses molecular iodine formation by reducing it to iodide and precipitates excess iodide through the formation of a Zn-Amine complex. This results in improved photoluminescence quantum efficiency and reduced deep trap density in the perovskite films. The use of these additives also facilitates the formation of uniform perovskite films on large-area substrates, leading to minimodules with certified power conversion efficiencies of 19.60% and 19.21% for aperture areas of 84 and 108 cm², respectively, at the National Renewable Energy Laboratory (NREL). The study highlights the importance of addressing iodide interstitial defects to minimize cell-to-module efficiency loss and demonstrates the effectiveness of Zn(OOSCF₃)₂ in achieving high-efficiency perovskite modules.This study investigates the use of zinc additives, specifically zinc trifluoromethane sulfonate (Zn(OOSCF₃)₂), to control iodide defects in perovskite solar cells, which are critical for improving device efficiency and stability. The introduction of Zn(OOSCF₃)₂ in the perovskite solution suppresses molecular iodine formation by reducing it to iodide and precipitates excess iodide through the formation of a Zn-Amine complex. This results in improved photoluminescence quantum efficiency and reduced deep trap density in the perovskite films. The use of these additives also facilitates the formation of uniform perovskite films on large-area substrates, leading to minimodules with certified power conversion efficiencies of 19.60% and 19.21% for aperture areas of 84 and 108 cm², respectively, at the National Renewable Energy Laboratory (NREL). The study highlights the importance of addressing iodide interstitial defects to minimize cell-to-module efficiency loss and demonstrates the effectiveness of Zn(OOSCF₃)₂ in achieving high-efficiency perovskite modules.