Spherical hydroxyapatite nanoparticle scaffolds for reduced lead release from damaged perovskite solar cells

Perovskite solar cells continue to attract interest due to their facile preparation and high power conversion efficiencies. However, the highest efficiency perovskite solar cells inevitably contain lead, which raises concerns over contamination of drinking water when a solar module is broken and then flooded. We previously showed that conventional synthetic hydroxyapatite (HAP) nanoparticles could capture some of the lead from broken solar cells, but the amount of lead released was well above the safe drinking water level. Here, we modify the HAP synthesis to prepare new spherical-HAP (s-HAP) nanoparticles with a 60% increase in the Pb absorption capacity. We blend s-HAPs with TiO 2 nanoparticles to construct mixed scaffolds and investigate their effect on (FAPbI 3 ) 0.97 (MAPbBr 3 ) 0.03 solar cell performance and lead capture. Replacement of 80% of the TiO 2 nanoparticles with s-HAP causes the power conversion efficiency to increase from 18.61% to 20.32% as a result of decreased charge carrier recombination. Lead contamination of water from devices subjected to simulated hail damage followed by flooding is shown to decrease exponentially with increasing s-HAP content. The lead concentration in water after 24 h is below the US safe water drinking limit. The contamination of water with lead from damaged perovskite solar cells is a key concern. Here, a spherical hydroxyapatite nanoparticle scaffold absorbs lead from a damaged device, keeping lead concentration in water below safe drinking limits.