Overcoming Uncontrolled Nucleation and Cesium Salt Solubility Limits in Scalable Perovskite Deposition through All-Inorganic Perovskite Nanocrystal Seeding

Optoelectronic performance, defect density, and thin-film morphology of solution-processable lead halide perovskites are highly dependent on nucleation and growth conditions during processing. Additionally, Cs⁺ incorporation into the lattice can have benign effects on the thin films, which is challenging for scalable, deposition-friendly solvents such as 2-methoxyethanol or acetonitrile due to their highly limited solubility of Cs-containing salts. To address both issues, we present an interface-engineering approach that utilizes CsPbI₃ nanocubes as seed crystals for slot-die coating of FAPbI₃. The seeds improve growth-control at the bottom interface and enhance Cs⁺ incorporation into the active layer lattice. Incidence angle varied grazing-incidence wide-angle X-ray scattering enables depth-resolved structural probing of thin films, revealing increased Cs⁺ incorporation with increasing film depth. Additionally, morphological parameters, such as thin-film “face-on” orientation and crystallographic texture, are significantly improved in the seeded film. Accordingly, the seeded films exhibit reduced defect density and enhanced charge-carrier separation due to increased structural ordering and Cs⁺ alloy-induced bandgap tuning across the active layer thickness. Resulting p-i-n photovoltaic devices exhibit superior mean values as well as a narrower spread across short-circuit current density, fill factor, and power conversion efficiency, highlighting the beneficial effects of nanocrystal seeding on active-layer quality and reproducibility.