Stabilization of formamidinium lead iodide perovskite precursor solution for blade-coating efficient carbon electrode perovskite solar cells

Formamidinium lead triiodide(FAPb I) is a research hotspot in perovskite photovoltaics due to its broad light absorption and proper thermal stability. However, quite a few researches focused on the stability of the FAPb Iperovskite precursor solutions. Besides, the most efficient FAPb Ilayers are prepared by the spin-coating method, which is limited to the size of the device. Herein, the stability of FAPb Iperovskite solution with methylammonium chloride(MACl) or cesium chloride(Cs Cl) additive is studied for preparing perovskite film through an upscalable blade-coating method. Each additive works well for achieving a high-quality FAPb Ifilm, resulting in efficient carbon electrode perovskite solar cells(pero-SCs) in the ambient condition. However, the perovskite solution with MACl additive shows poor aging stability that no α-FAPb Iphase is observed when the solution is aged over one week. While the perovskite solution with Cs Cl additive shows promising aging stability that it still forms high-quality pure α-FAPb Iperovskite film even the solution is aged over one month. During the solution aging process, the MACl could be decomposed into methylamine which will form some unfavored intermediated phase inducing δ-phase FAPb I. Whereas, replacing MACl with Cs Cl could effectively solve this issue. Our founding shows that there is a great need to develop a non-MACl FAPb Iperovskite precursor solution for cost-effective preparation of pero-SCs.