“…Like other kinds of thin-film solar cells, the optoelectronic properties of perovskite materials are highly dependent on their film quality. So far, many approaches have been introduced, such as composition engineering, solvent engineering, interfacial modification, additive regulation, and film-casting processing, − to achieve high-quality perovskite layers, which are critical factor to achieving high-performance PSCs. Additive engineering of perovskite precursors has been proven to be an effective approach for delivering homogeneous nucleation or regulating the crystallization kinetics of perovskite films. − Among the different additives, chlorine-based additives have been demonstrated to be suitable for controlling and improving the perovskite film morphology as well as suppressing the bulk defects to obtain high-performance solar cells. ,, In this regard, methylammonium chloride (MACl) and lead chloride (PbCl 2 ) have attracted a lot of attention due to the chloride ion in their composition, which could retard the crystallization and improve the quality of the perovskite films. , In 2013, Stranks et al showed that the chlorine-containing perovskite could extend the carrier diffusion lengths to 1 μm.…”