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

Abstract

Organic−inorganic lead halide perovskite (CH 3 NH 3 PbI 3 ) 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., (NH 4 ) 2 HPO 4 ) in PV and other perovskite-based optoelectronic devices in various architectures. Phosphate salts do not react with CH 3 NH 3 PbI 3 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.

Managing Lead Leakage in Efficient Perovskite Solar Cells with Phosphate Interlayers

“…The rapid degradation of perovskite film on SnO 2 :Na 3 PO 4 substrate can be ascribed to the fast reaction of phosphate with lead in water, forming transparent products of Pb 2 PO 4 I. [ 19 ] The potential reactions are supposed to be $$\[ \begin{array}{*{20}{c}}{{\rm{N}}{{\rm{a}}_3}{\rm{P}}{{\rm{O}}_4} + {{\rm{H}}_2}{\rm{O}} \to {\rm{N}}{{\rm{a}}_2}{\rm{HP}}{{\rm{O}}_4} + {\rm{NaOH}}}\end{array} \]$$ $$\[ \begin{array}{*{20}{c}} \begin{array}{l}2{\rm{F}}{{\rm{A}}_{0.93}}{\rm{M}}{{\rm{A}}_{0.07}}{\rm{Pb}}{{\rm{I}}_3} + {\rm{N}}{{\rm{a}}_2}{\rm{HP}}{{\rm{O}}_4} + {{\rm{H}}_2}{\rm{O}}\\ \to {\rm{P}}{{\rm{b}}_2}{\rm{P}}{{\rm{O}}_4}{\rm{I}} + 2{\rm{F}}{{\rm{A}}_{0.93}}{\rm{M}}{{\rm{A}}_{0.07}}{\rm{I}} + 2{\rm{NaI}} + {\rm{HI}}\end{array} \end{array} \]$$where the Pb 2 PO 4 I is the water‐insoluble products with transparent color. The chelated Pb tightly bonded on the substrate without dissolving into the water again for possible contaminations.…”

“…The rapid degradation of perovskite film on SnO 2 :Na 3 PO 4 substrate can be ascribed to the fast reaction of phosphate with lead in water, forming transparent products of Pb 2 PO 4 I. [19] The potential reactions are supposed to be…”

“…[ 10,11,17,18 ] It has also been reported that the phosphate additives do not affect the optoelectronic properties of perovskites in dry condition, while react with Pb immediately in wet atmosphere by forming insoluble compounds, thus preventing Pb contamination. [ 19 ] Therefore, it is quite urgent to develop efficient ETLs with both passivated defects and robust Pb‐adsorbing capability.…”

“…[3] Environmentally friendly and high-performance PSCs are highly desired and been aroused with more attention; forming insoluble compounds, thus preventing Pb contamination. [19] Therefore, it is quite urgent to develop efficient ETLs with both passivated defects and robust Pb-adsorbing capability.…”

Halide Perovskite Solar Cells for Building Integrated Photovoltaics: Transforming Building Façades into Power Generators

“…[ 205 ] They can be used to effectively adsorb Pb 2+ through rapid chemical reactions or rapidly precipitates lead in halide perovskites, in an irreversible manner, into highly water‐insoluble lead compounds. [ 206 ] Although such Pb‐absorbing materials and resins are developed to avoid the leakage toxic element from damaged PSCs, however, their influence of on the transparency and color of semitransparent PSCs have not been clearly evaluated.…”