Morphology and Crystallinity Amelioration of MAPbI₃ Perovskite in Virtue of PbI₂ Thermal Absorption Drifted Performance Enhancement in Planer n–i–p Solar Cells

Sequential deposition route is widely investigated in fabricating perovskite thin films for state‐of‐the‐art perovskite photovoltaics. However, concerns such as lower morphological control, phase purity, and remnant unreacted salts methylammonium iodide (MAI and PbI₂) are raised, which can significantly deteriorate optoelectronic properties, hence the operational durability of the devices. Herein, a facile two‐step method to prepare high‐quality perovskite thin films with reproducibility is reported, as‐spun PbI₂ is annealed at varying thermal input under controlled rate, and a trend in converted perovskite film properties is noted. Specifically, PbI₂ thin film annealed at 200 °CC results in 20x intensified crystallinity with pinholes free and a subsequent reduction in the crystal microstrain. In addition, it provides higher surface roughness to load more MAI [in iso‐propyl alcohol (IPA)]; therefore, a higher perovskite conversion is achieved. This method enables a significant efficiency enhancement in the treated sample (Pero@PbI₂‐200 °C) as compared with controlled film; it retains around 90% initial efficiency after 384 h of ambient exposure. Furthermore, a facile intermediate solvent treatment method to gain the complete conversion of PbI₂ into perovskite is also reported. This study highlights the importance of morphological control in governing optoelectronic properties, hence the efficiency and stability of perovskite solar cells.