Levetiracetam-Assisted Perovskite Crystallization and Tripartite Lead Iodide Reduction in Perovskite Solar Cells.

Sequential deposition technique is widely used to fabricate perovskite films with large grain size in perovskite solar cells (PSCs). Residual lead halide (PbI) in the perovskite film tends to be decomposed into metallic lead (Pb) under long-term heating or light soaking. Here, a chiral levetiracetam (LEV) dopant containing α-amide and pyrrolidone groups is introduced into the PbI precursor solution. The carbonyl oxygen (labeled O1) and amide oxygen (labeled O2) in the pyrrolidone ring have significant electronegativity and form coordination bonds with Pb ions through electron transfer, thereby regulating the nucleation and crystallization process of perovskite. The chirality of LEV induces spatial selectivity in perovskite precursor coordination, promoting oriented growth along the (100) crystallographic facet. Additionally, it enables selective defect passivation, preferentially addressing Pb and I vacancies. Ultimately, LEV doping reduces the tripartite residual PbI in the perovskite film, including multi-interfaces and bulk. Besides, the resulted PSCs achieved a champion power conversion efficiency (PCE) of over 26% with a stabilized power output of 25.8% and maintained 90% of its initial PCE after maximum power point tracking for 1000 h. This study offers a novel research paradigm to advance the development of perovskite photovoltaics.