All-in-one additive enables defect passivated, crystallization modulated and moisture resisted perovskite films toward efficient solar cells

The high-quality perovskite film with low trap densities and large grains is a prerequisite for achieving high-performance and stable perovskite solar cells (PSCs). It is desirable to simultaneously realize the defect passivation and crystallization control of perovskite films. Here, an all-in-one additive, named 2-[N,N-bi(trifluoromethylsulfonyl)amino]pyridine (2-BTFSIP), is introduced into the perovskite layer to address this issue. It is demonstrated that the sulfonyl group and pyridine nitrogen cooperatively passivate the deep-level traps (Pb0 cluster and under-coordinated Pb2+ ions), while the trifluoromethyl group suppresses the evaporation of organic cations as well as improves the hydrophobicity of perovskite films. In addition, crystallization control is also realized by the synergetic effect of multiple groups to obtain a larger crystal size. It is revealed that reduced defect densities, suppressed non-radiative recombination and prolonged carrier lifetimes are achieved. As a result, MAPbI3 and FAPbI3 devices passivated by the 2-BTFSIP molecule yield the champion power conversion efficiency (PCE) of 21.96% and 22.90% with negligible hysteresis, respectively. Meanwhile, 2-BTFSIP-modified MAPbI3 devices maintain over 90% of its original PCE as long as for 6000 h storage. Hence, this work provides a new perspective for designing effective multifunctional additives to remarkably improve PCE and stability of PSCs.