Highly efficient and stable perovskite solar cells via amide-mediated suppression of iodine impurities

The photoelectronic properties of perovskite solar cells (PSCs) are impaired by iodine (I₂) impurities that originate from the oxidation of iodide ions present in precursor solutions and perovskite films. This study systematically evaluates the effectiveness of two amide-based reducing agents, L-prolinamide (LPM) and 2,3-pyrazinedicarboxamide (LLM), as additives for mitigating detrimental I₂ impurities within perovskite. Notably, the enhanced electrophilicity of pyrazine structure of LLM, relative to the tetrahydropyridine of LPM, facilitates stronger I− anchoring through halogen-nitrogen coordination, thereby effectively suppressing iodide oxidation. Furthermore, the greater number of amide groups in LLM enhances its interaction with perovskite cations such as lead ions (Pb2+) and formamidinium ions (FA+), leading to moderated crystallization kinetics and the formation of larger grains. Consequently, the LLM-doped PSCs attained a champion power conversion efficiency (PCE) of 25.51% and retained 93.9% of their initial efficiency after aging at 85 °C and 85% of relative humidity for 1300 h.