Improving the Air Resistance of the Precursor Solution for Ambient-Air Coating of an Sn–Pb Perovskite Film with Superior Photovoltaic Performance

Owing to narrow band gap and low toxicity, tin-lead (Sn-Pb) hybrid perovskites have shown great potential in photovoltaic applications, and the highest power conversion efficiency (PCE) of Sn-Pb perovskite solar cells (PSCs) has recently reached 23.6%. However, it is still challenging to prepare Sn-Pb films in open-air condition due to the Sn2+ oxidation of the precursor solution under this condition. In this work, we report the stabilizing of the Sn-Pb perovskite precursor solution by using ionic liquid methylammonium acetate (MAAc) as the solvent, which enables the fabrication of Sn-Pb films in air. MAAc is found to coordinate with the Sn-Pb precursor via abundant hydrogen bonding, which stabilizes the colloids and protects the Sn2+ stability in the precursor solution in air. Therefore, the durability of the Sn-Pb precursor solution based on the MAAc solvent is greatly improved, which enables the fabrication of efficient PSCs and achieves a champion PCE of ∼16% with robust device stability. Moreover, due to the chemical interactions of MAAc with Sn-Pb perovskites, the Pb leakage is also suppressed in the MAAc-based Sn-Pb PSCs. This work demonstrates a feasible strategy for reliable fabrication of Sn-Pb PSCs, which could also be applied in many other optoelectronic devices.