Influence of Codeposition on Methylammonium Iodide Degradation during Vapor Transport Deposition

Vapor transport deposition (VTD) is one manufacturing-compatible technique for the large-scale deposition of perovskite films. However, to date, little understanding has been given to degradation products formed by perovskites grown under vacuum. Here, we use methylammonium iodide (MAI) as an example organic precursor to identify degradation patterns through both the sublimation process and transport through a zone with temperatures much higher than that where MAI can thermodynamically survive. We show that degradation due to sublimation effects MAI powders and subsequent integration into methylammonium lead iodide (MAPbI₃) films differently than degradation solely due to material transport through a very high-temperature zone. Additionally, we categorize common postdeposition treatments by their influence on the degradation products seen in MAPbI₃ films. With these results, we give recommendations for VTD reactor design and the feasibility of codeposition as a film growth technique.