Unraveling the Influence of Solvent on Side Reactions between Formamidinium Lead Triiodide and Methylammonium Cations.

Formamidinium lead triiodide (FAPbI) perovskite thin films are commonly deposited through a solution process, often incorporating a specific amount of methylammonium halide to stabilize the α-phase or enhance their crystallinity. The precursor solution for such coatings significantly influences the fabrication of perovskite solar cells (PSCs), involving time-dependent aging and byproduct formation. The chemical principle underlying this behavior is believed to be related to the deprotonation of methylamine cations (MA) and subsequent chemical reactions with FA to generate -methylformamidinium.

Controlled growth of perovskite layers with volatile alkylammonium chlorides.

Controlling the crystallinity and surface morphology of perovskite layers by methods such as solvent engineering and methylammonium chloride addition is an effective strategy for achieving high-efficiency perovskite solar cells. In particular, it is essential to deposit α-formamidinium lead iodide (FAPbI) perovskite thin films with few defects due to their excellent crystallinity and large grain size. Here we report the controlled crystallization of perovskite thin films with the combination of alkylammonium chlorides (RACl) added to FAPbI.