Fighting Health Hazards in Lead Halide Perovskite Optoelectronic Devices with Transparent Phosphate Salts

Organic-inorganic lead halide perovskite (CH₃NH₃PbI₃) solar cells have surpassed 25% power conversion efficiency, being ready for industrial-scale production of cheap photovoltaic (PV) panels. In this action, the major hurdle is its lead content, which in case of device failure, could be washed into the soil, entering the food chain. Since there is a zero tolerance on lead in the human organism, this health hazard is a critical obstacle for commercialization. Here, we propose a solution to this problem by incorporating phosphate salts (e.g., (NH₄)₂HPO₄) in PV and other perovskite-based optoelectronic devices in various architectures. Phosphate salts do not react with CH₃NH₃PbI₃ and do not alter its advantageous optoelectronic properties, but in a wet environment, they react immediately with lead, forming a highly insoluble compound, precluding this way the spread of lead into the environment. It is expected that this study will stimulate research, enabling lead halide perovskite solar cells to reach a similar environmental risk category as the commercially available, nonwater-soluble heavy metal-containing CdTe and gallium diselenide technologies.