RESUMO
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.