Effect of fluorinated arylammonium halide passivation in chloride–iodide perovskite solar cells

Abstract

Due to the radius mismatch between iodine and chlorine, ion migration is unavoidable in chloride–iodide perovskites. The presence of atomic vacancies in the solution-processed perovskite thin film works as a route of ion migration. Here, we investigate the consequence of the ion migration in chloride–iodide perovskite solar cells. We use FA_0.6MA_0.4PbI_2.7Cl_0.3 as the active perovskite layer. We passivate the top surface of the chloride–iodide perovskite thin film with mixed 4-fluorobenzylammonium chloride and 4-fluorobenzylammonium bromide. We observe that fluorinated benzylammonium halides show better passivation and hydrophobicity. Compared to the non-passivated solar cells, we get a significant fill factor and stability improvement. We get 76.44% fill factor from our passivated solar cell. Besides, our passivated solar cell offers a photo conversion efficiency of 21.10%. Moreover, we also get about 80% stability without encapsulation after 56 days.