Biomass-derived functional additive for highly efficient and stable lead halide perovskite solar cells with built-in lead immobilisation.

Despite notable progress in the power conversion efficiency (PCE) of lead halide perovskite solar cells (PSCs), their commercial viability remains limited by stability issues and the risk of lead contamination. Uncoordinated lead ions can introduce defects during perovskite crystallization, resulting in reduced stability and potential environmental contamination. Here, we synthesized a biomass-derived tetrabutylammonium alginate (TBA-Alg) polymer that forms a connected network at the perovskite surface and grain boundaries to effectively manage lead ions and passivate defects. The alginate groups anchor unbound lead ions, promoting more ordered crystallization, while the hydrophobic tetrabutylammonium chains enhance moisture resistance. The TBA-Alg-modified inverted p-i-n PSCs achieved a PCE of 25.01% and retained 95.5% of their initial performance after 2000 hours of storage. Under continuous illumination at ∼60% relative humidity (RH) for 1050 hours, the devices retained 80% efficiency. Even under water immersion, the TBA-Alg network effectively protected lead ions from water erosion and suppressed 83% of lead leakage. This strategy simultaneously achieves high PCE and stability of lead halide PSCs, and effectively prevents lead contamination; thereby offering the potential to greatly advance the commercialization of lead halide PSCs.