One Stone Two Birds: Sustainable Perovskite Solar Cells Obtained by Using Water‐Based Recycled PbI ₂ and Guanidinium Thiocyanate Post‐Treatment

Recycling materials from end‐of‐use metal halide perovskite solar cells (PSCs) is essential for reducing environmental risks and improving the sustainability of this emerging photovoltaic technology, with lead iodide (PbI ₂ ) being a target due to its toxicity and material value. However, the performance of PSCs is known to be highly sensitive to the purity of precursor materials including PbI ₂ . In this study, a simple water‐based recycling and recrystallization method was developed to recover PbI ₂ from spent PSCs. Characterizations have shown that the recycled‐PbI ₂ was comparable to high‐purity (99.99%)PbI ₂ . The perovskite (MAPbI ₃ ) film made from the recycled‐PbI ₂ or lower purity (99%)PbI ₂ shows smaller grains, which are undesirable for their applications in solar cells. It is found that treatment of the recycled PbI ₂ ‐based perovskite film with guanidinium thiocyanate (GuaSCN) can significantly enhance morphology and properties of the perovskite film with larger grains (∼700 nm), reduced trap‐assisted recombination. PSCs with champion power conversion efficiency (PCE) of 17.25% were obtained, which well surpassed the performance of the PSCs made from commercial 99%PbI ₂ (PCE 11.68%). This work shows the potential of reclaiming PbI ₂ from decommissioned, decomposed perovskite materials, and even purifying the contaminated PSCs in a cost‐efficient and environmentally friendly manner, generating commercial and environmental benefits.