Soil adsorption and transport of lead in the presence of perovskite solar cell-derived organic cations.

Perovskite photovoltaics offer a highly efficient and low-cost solar energy harvesting technology. However, the presence of lead (Pb) cations in photovoltaic halide perovskite (HaPs) materials is concerning, and quantifying the environmental hazard of accidental Pb leaching into the soil is crucial for assessing the sustainability of this technology. Pb from inorganic salts was previously found to remain in the upper soil layers due to adsorption. However, Pb-HaPs contain additional organic and inorganic cations, and competitive cation adsorption may affect Pb retention in soils. Therefore, we measured, analyzed by simulations and report the depths to which Pb from HaPs penetrates into 3 types of agricultural soil. Most of the HaP-leached Pb is found to be retained already in the first cm of the soil columns, and subsequent rain events do not induce Pb penetration below the first few cm of soil surface. Surprisingly, organic co-cations from the dissolved HaP are found to enhance the Pb adsorption capacity in clay-rich soil, compared to non-HaP-based Pb sources. Our results imply that installation over soil types with improved Pb adsorption, and removal of only the contaminated topsoil, are sufficient means to prevent ground water contamination by HaP-leached Pb.