Lead iodide crystal arrangement modulation promotes preferential growth of perovskite orientation for efficient and stable solar cells

The sequential deposition process has been widely employed to fabricate perovskite solar cells (PSCs) due to its favorable operability. However, the random orientation of perovskite (PVK) films resulting from the rapid and unregulated solid-liquid reaction poses a significant challenge to enhancing the performance of PSCs prepared via the sequential deposition process. This study proposes a strategy for manipulating the arrangement pattern of lead iodide (PbI₂) crystals to regulate the orientation and uniformity of PVK films. Polyvinylidene fluoride (PVDF) molecules are introduced into the PbI₂ solution to manipulate the arrangement of PbI₂ through their interactions. The enhanced PbI₂ crystals with the (301) plane create favorable conditions for the preferential growth of PVK crystals, significantly improving the crystallinity and uniformity of the PVK film. Ultimately, we achieved formamidinium-rich PSCs with photoelectric conversion efficiencies (PCEs) of 24.84 % for a millimeter-scale device (active area of 0.09 cm 2 ) and 21.15 % for a centimeter-scale device (active area of 1 cm 2 ). Furthermore, the reduction in defect state density and internal stress within the film resulted in unencapsulated devices exhibiting remarkable stability under various harsh environmental conditions.