Amidinium additives for high-performance perovskite solar cells

Perovskite solar cells (PSCs) have developed rapidly and achieved power conversion efficiencies (PCE) of over 25% with diverse technical routes. However, defect is a major factor for device degradation, so a high-quality perovskite film with low defect density is critical to device performance. Here, we fabricate highly efficient and stable PSCs by introducing butyramidinium chloride (BRCl) into PbI2 precursor solution. BRCl retards the nucleation and accelerates the crystal growth of perovskite by interacting with PbI2, thereby obtaining high-quality crystalline perovskite films with large grains and few defects. In addition, BRCl effectively passivates the defects and reduces non-radiative recombination in the resultant film. Accordingly, planar n-i-p PSCs achieve a champion PCE of 23.27%. Importantly, the device stability under thermal, ambient and illumination stress is improved. Notably, non-encapsulated BRCl-assisted devices retained 93% of their initial PCE after over 1000 h under maximum power point tracking (MPP) in a N2 atmosphere.