Insight into the Defect Chemistry and Ion Migration in Perovskite Fabricated by Hybrid Chemical Vapor Deposition

Hybrid chemical vapor deposition (CVD) is an industrially relevant thin-film deposition method and has demonstrated great advantages in large-area uniform perovskite film preparation. However, perovskite solar cells prepared by hybrid CVD suffer from low power conversion efficiency compared to those deposited by the solution methods. Herein, the origin of the efficiency gaps between hybrid CVD and solution methods is systematically investigated. Optical and electrical characterizations indicated a severe nonradiative recombination loss on the hybrid CVD-prepared perovskite. X-ray photoelectron spectroscopy and thermal admittance spectroscopy measurements revealed the iodine-rich surface and higher density of deep-level defects (i.e., I_Pb and V_Pb) of hybrid CVD-prepared perovskite, which shorten the carrier lifetime via Shockley-Read-Hall recombination. These deep-level defects facilitate the migration of ions under bias, posing a concern for device operational stability. The fundamental understanding could pave the way for the advancement of hybrid CVD methods from a defect engineering perspective.