Slowing the crystallization speed to prepare high-efficiency flexible tin-based perovskite solar cells

• Effect of hydrochloride with different chain lengths on the quality of thin films were studied. • PACl is got to modify FASnI 3 film with the highest performance. • The flexible lead-free solar cell with high PCE (5.52%) and stability is obtained. In this study, five hydrochlorides are used as additives to slow the crystallization rate between SnI 2 and AI (A + =MA + , FA + , Cs + ) to prepare high-quality perovskite films. This study on film morphology, crystallization and non-radiative recombination demonstrates the effects of organic amine cations with different chain lengths on the quality of thin films. A flexible solar cell device with a lead-free perovskite film doped with PACl is also obtained achieving an efficiency of 5.52 %.