Investigation on Crystallization of CH ₃ NH ₃ PbI ₃ Perovskite and Its Intermediate Phase from Polar Aprotic Solvents

Perovskite films are usually fabricated by a solution-processed method due to its low cost and ease of fabrication. The organic solvent plays multiple roles in the growth of perovskites. Here, we investigate the growth of methylammonium lead iodide perovskite and its intermediate phase from microdroplets containing various solvents. The perovskite intermediate phase inclines to grow in the direction of its (020) plane from polar aprotic solvents at low temperature. At high temperature, the growth of perovskites depends on the structure of solvent molecules. The intermediate phase still grows from the solvents with a short chain structure. It tends to form smooth films containing radial domains with dimensions in tens of microns, which consist of nanocrystals due to annealing effects. However, perovskite grains grow directly from the solvents with a ring structure. It tends to form smooth thin films by joining the large hexagonal perovskite crystals together. It provides a guidance to prepare high quality perovskite films for high performance optoelectronic devices.