Orientation-Controlled (h0l) PbI₂ Crystallites Using a Novel Pb-Precursor for Facile and Quick Sequential MAPbI₃...

Organic-inorganic hybrid lead halide perovskites have shown significant progress in the last few years having achieved efficiencies over 25% at the lab scale. The sequential deposition technique has provided a robust approach in the perovskite film fabrication. However, obtaining a reproducible and quality perovskite film has always been challenging because of the highly crystalline and ordered (001) oriented underlying PbI₂ film. Here, we report a simple solution approach to fabricate a PbI₂ residue-free, superior grade perovskite film by using a compositional engineered PbI₂-precursor solution. We demonstrate that the Pb-precursor film crystallized into a R-centered Hexagonal metric lattice with (h0l), (hk0), and (00l) orientations provides a more efficient and quicker conversion into perovskites compared to conventional (001) oriented 2H-PbI₂. A porous and multi-oriented PbI₂ film is prepared by rationally incorporating a volumetric fraction of Pb(Ac)₂·3H₂O in the typical PbI₂/dimethylformamide precursor solution, which significantly improves the surface features of PbI₂ as well as the structural properties. As a result, a compact, smooth, and large grain perovskite can be obtained by accomplishing a full conversion with comparatively much less reaction time. Furthermore, a comprehensive mechanism of structural modification of PbI₂ and the role of its orientation in ameliorating the reaction kinetics has been demonstrated.