Thermally induced recrystallization of MAPbI3 perovskite under methylamine atmosphere: an approach to fabricating large uniform crystalline grains.

A liquid to solid phase transition of methylammonium lead triiodide (MAPbI3) under methylamine (MA) atmosphere at elevated temperatures was discovered, and used to form high quality and uniform thin films containing large, low defect crystal grains tens of microns in size.